Stability and Control characteristics of the Early Mark Spitfires [Archive]

Crumpp

07-14-2012, 02:57 PM

The early mark Spitfire was a excellent fighter.

It was not without its issues like many aircraft. Raw performance numbers for speed and climb do not tell the whole story about any design. The pilots ability to precisely maneuver and use a fighter to the edge of its envelope as an effective gun platform is just as important to the fighting ability of the design as any other performance parameter.

Amoung the Western Front warring powers during World War II, only two nations had measurable and definable stability and control standards. Stability and control was a young science. Airplanes had simply been two slow and light previously. The forces were small enough such that there was little need. The two nation were the United States and Germany.

At the beginning of World War I, the United States found its aviation industry in a dismal state of affairs. Despite being the nation credited with the first manned, powered, controllable, and heavier than air flight, the US aviation industry had only 8 airplanes and 14 trained pilots in 1914. France on the other hand, had 260 aircraft and 171 trained pilots in 1914. This prompted a flurry of US Government action to bolster the aviation industry included the creation of the NACA in 1915. By wars end, the United States produced 7,000 airplanes and 20,000 engines. The surplus was such that post war, for ~$500 dollars cost for the pilot's license a successful solo resulted in the award of a JN-4 Jenny airplane to the new pilot. The emphasis on the aviation industry continued throughout the 1920's and 1930's.

Everyone is familiar I believe with the Nazi parties emphasis on aviation. Like the events in Russia, unfortunate circumstances would align to bolster the introduction of fresh ideas and innovation in the aviation sector.

Let's not be obtuse. None of this is to claim other nations did not progress in aviation or contribute. It is only to lay the historical foundation as to why these were the only Western Nations to adopt stability and control standards.

This thread is going to cover the definable and measure stability and control characteristics of the Spitfire. It is not going to cover opinion outside of stability and control engineers.

What this thread is not going to do:

1. Get into a debate about "easy to fly". It is not definable and has no bearing on the measured facts.

2. It is not going to discuss the sustained level turning ability of the aircraft. That is also measurable and definable. For Example, anyone who is capable of doing the math will see that the Spitfire outturns the Bf-109 is steady state constant altitude turns at low velocity.

Stability and control is the measurable science of flying qualities as they appear to the pilot. This means it is the science of creating a control system that the pilot can safely extract maximum performance of the aircraft. While there are some subjective areas because historical data is incomplete, It is not pilot opinion and while it is branch of aerodynamics, it does not tell us specific performance numbers of a solid body outside of the control system moments.

Moderators, I ask you to keep a close eye on this thread.

Let's lay some of the ground work for the discussion by first looking at what is acceptable and what is not acceptable for longitudinal stability.

The first condition we will discuss is the Longitudinal stability characteristics in an abrupt pull up and release of the stick.

The NACA found the Spitfire to be acceptable in this area. Why discuss it? It is harbringer of things to come in the Spitfires Longitudinal stability and I think the light bulb will come on for most readers as to the importance of stability and control. It will lay the foundation for more informed discussions of other designs included in the game and in the future as the game grows.

These first charts come from the USAAF and USN stability and control standards as adopted during World War II.

Acceptable Longitudinal stability characteristics in an abrupt pull out:

http://img694.imageshack.us/img694/672/longitudinalcontrolabru.jpg (http://imageshack.us/photo/my-images/694/longitudinalcontrolabru.jpg/)

Things to notice....

1. The amount of force required is larger than one would think. A separate NACA study determined that the average pilot can easily apply 80lbs of pull force on the controls. In roughly .5 seconds the pilot is able to apply ~80lbs of force to precisely produce an acceleration of ~3.5 G's. Upon release of the stick, which is the top of the stick force curve at ~80lbs, the acceleration curve is nicely sloped without any wild fluctuations.

So even though the stick is moving around and we see the force move from push to pull, there is no change in the airframes acceleration. The controls are floating after release. The control system friction is sufficiently dampened by the inherent stability of the design.

In other words, the pilot can quickly and precise apply a specific amount of acceleration to the airframe and control it.

The high stick forces act as a solid foundation to resist pilot induced oscillations under aceleration. The pilot does not need to brace himself but can precisely control the aircraft from normal seating.

Now let's look at what is unacceptable longitudinal stability in abrupt pull outs:

http://img824.imageshack.us/img824/9687/unsatisfactoryabruptpul.jpg (http://imageshack.us/photo/my-images/824/unsatisfactoryabruptpul.jpg/)

First thing to notice is the small amount of stick force that produces a large acceleration. This means the pilot must brace himself if he is going to control the accelerations. It also means it is very easy to apply more accelerations than the airframe can handle. The pilot does not have a solid foundation to resist pilot induced oscillation.

The next thing is the slope of the curve of stick force application to release and the accelerations do not match. This means the acceleration increase is not proportional to the amount of stick travel. As the accelerations increase, less stick travel is required to increase them.

After the stick is released, accelerations continue to increase.

The controls do not float. Instead, they released control continues to produce accelerations as the inherent stability of the design cannot overcome the control system friction. Now that does not mean the control force friction is excessive. It could be that but it can also be the design does not have sufficient dampening on the longitudinal axis.

Our aircraft begins to porpoise and begins another acceleration cycle.

Now let's look at the Spitfire in an abrupt pull out as measured by the NACA.

http://img98.imageshack.us/img98/3200/spitfireabruptpullup.jpg (http://imageshack.us/photo/my-images/98/spitfireabruptpullup.jpg/)

First thing to notice is the stick forces. There are light but acceptable in abrupt pull outs. While very steep, the slope of the curve matches our acceleration curve and the controls float without overcoming the inherent stability of the design. The steepness of the curve tells us the pilot is able to very rapidly load the airframe. In fact, the NACA had to make allowance in their stick fixed measurements to prevent damage to the aircraft from acceleration because of the rapid onset the controls allowed.

However, if we look at the acceleration curve we see an abrupt change and not the desirable smooth curve. This points to the stability characteristics contributing to the rapid fluctuations in acceleration that the aircraft exhibits under other conditions.

The harbinger's of things to come:

1. The steepness of the curve tells us the pilot is able to very rapidly load the airframe.

2. The light stick forces does not provide a solid foundation for the pilot to resist oscillation.

Next we will get into the unacceptable longitudinal stability characteristics of the design.

to be Con't.......

Crumpp

07-14-2012, 03:08 PM

Resist oscillation is not the pilot controlling the oscillation with control input. That is the wrong thing to do in most cases and can get you into real trouble.

Instead the high forces mean the stick is not moving and it takes a deliberate effort to control the plane so the chance of over control is reduced.

The light stick forces make it easier to inadvertently over control or apply control pressure when it is not required.

IvanK

07-15-2012, 12:17 AM

A lot of the NACA stuff can be found here:

http://ntrs.nasa.gov/?method=aboutntrs

Crumpp

07-15-2012, 12:28 AM

It was actually addressed in the Spitfire Mk V but the longitudinal instability existed from the beginning.

The RAE did not have stability and control standards. However, the RAE did agree with the NACA even if they did not know it.

They published all the warnings and characteristics of the Longitudinal instability in the Operating Notes. We will get to that.

As for the CG position theory, again, the RAE was in complete agreement with the NACA. They published all the warnings and characteristics of the Longitudinal instability in the Operating Notes.

It is kind of hard to argue that the NACA was incapable of performing a simple weight and balance when the RAE fixed the same issue and published warnings in the Operating Notes. The truth is they just did not know what the NACA was talking about as the stability and control criteria was classified at the time and Gates had not completed his visit.

Gates was well versed in stability and control, however. When presented with the facts and his own testing, he came to the same conclusions as the NACA. That is why the longitudinal instability was addressed with the bob-weights.

I attached the bob-weights which were added to the Spitfire Mk V to correct the longitudinal instability. I also attached an exerpt from Perkins and Hage.

Crumpp

07-15-2012, 12:30 AM

Some of Gates testing results on the early Mark Spitfires.....

TomcatViP

07-15-2012, 12:31 AM

Crumpp

07-15-2012, 12:32 AM

But I guess what I was asking was, is there an archive online that everyone else knows about that I don't where one can get all the RAE and NACA documents?

Here is the RAE stuff...

http://aerade.cranfield.ac.uk/listarcrm.php

CaptainDoggles

07-15-2012, 12:40 AM

Nice. Thanks for the links guys.

Crumpp

07-15-2012, 02:27 AM

http://www.avialogs.com/list/item/3400-ap-1565b-pilots-notes-spitfire-iia-and-iib-aeroplanes-merlin-xii-engines

hve a look p7, 8 & 16 (repect. rpm vs speed as indicated by the manual, handling characteristics and boost). Doc is AP1565B Spit IIA&B flight manual, edited in June 40 and published in July40.

Good post. The RAE was very much aware of the longitudinal instability and the Operating Notes is full of warnings that are the result.

I will post the relevant graphs, stability and control engineer opinion, and the highlights from the Operating Notes in my continuation.

What is funny is the next aircraft I was going to discuss is the Hawker Hurricane. Sir Sydney Camm may not have understood swept wing theoy during the war but he was a master of stability and control design. The Hurricane was a wonderful gun platform and had near perfect longitudinal stability. His other major designs, the Typhoon and Tempest also exhibited the same characteristics.

In the Battle of Britain, Hurricanes scored the highest number of RAF victories, accounting for 1,593 out of the 2,739 total claimed.

Last Witness” Bob Doe explains: “An average pilot could get more from a Hurricane than from a Spitfire. But if you were good you could get more from a Spitfire. A Hurricane was like a brick-built s---house. It was sturdy and reliable, and it did not leap about when the guns were fired.

http://www.telegraph.co.uk/history/battle-of-britain/7851030/Battle-of-Britain-without-the-hurricane-the-battle-would-have-been-lost.html

camber

07-15-2012, 02:54 AM

Thank you for your post, Crumpp

This thread is going to cover the definable and measure stability and control characteristics of the Spitfire. It is not going to cover opinion outside of stability and control engineers.

Defined like that, any argument is rather moot. If it is defined that the only stability and control engineers at that time were in the US (specifically associated with NACA), and they formulated standards which the Spitfire failed, then the Spitfire failed...as defined in this rather narrow question.

I believe that the work of the pioneering stability and control engineers was interesting and valuable for the future of aviation. But the Spitfire seems to be a bad example to demonstrate that value.

As opposed to the objectively derived flight stability data, the standards that NACA set were subjective (e.g. X inches in control deflection to perform Y). Defensible, intuitively correct, but subjective.

Despite failing these subjective standards, many records exists describing the Spitfire handling as (subjectively) good. Many descriptions exist of Spitfire first flights by novice pilots. Some note the Spitfire pitch issues (e.g "found it easy to black myself out"), but express relief at finding the aircraft benign to fly and push hard.

I realise that you want to exclude all these considerations as being mere anecdotes. But then what it is the argument? I think we all agree that NACA failed the Spitfire on certain aspects of it's flight stability. To determine what that meant, we have to go further.

I think the Spitfire is not a good example of the value of the advances in stability and control. Despite it's rather alarming characteristics in the NACA reports, the young humans sitting inside RAF Spitfires were capable of rapidly adapting to them and making the Spitfire what it was intended to be ..a superlative short range military interceptor.

camber

Crumpp

07-15-2012, 03:23 AM

If it is defined that the only stability and control engineers at that time were in the US (specifically associated with NACA), and they formulated standards which the Spitfire failed, then the Spitfire failed...as defined in this rather narrow question.

Gates was not NACA and neither was the RAE when they published the Operating Notes.

Spitfire is not a good example of the value of the advances in stability and control.

It is not meant to be a good example of advances in stability and control. The thread is meant to point out the measureable and definable characteristics so that they can be modeled for the game.

camber

07-15-2012, 04:32 AM

Gates was not NACA and neither was the RAE when they published the Operating Notes.

I read the notes. Do you consider that the warnings against misuse are exceptional for the period, or exceptional compared to later WWII aircraft with better stability characteristics?

It is not meant to be a good example of advances in stability and control. The thread is meant to point out the measureable and definable characteristics so that they can be modeled for the game.

That is a good idea and worth pursuing, but there is an unfortunate snag. Not only are people using different control hardware to control the same virtual aircraft, they have the option to tune the response between the physical control deflection and the virtual control surface deflection with nonlinear curves. This ability is not under the umbrella of the flight sim software itself. Some people have simulated control surface loading (FFB), some do not, and again the user can quietly do their own stability modifications to make their plane handle differently to what the devs attempt to program.

camber

CaptainDoggles

07-15-2012, 05:07 AM

That is a good idea and worth pursuing, but there is an unfortunate snag. Not only are people using different control hardware to control the same virtual aircraft, they have the option to tune the response between the physical control deflection and the virtual control surface deflection with nonlinear curves. This ability is not under the umbrella of the flight sim software itself. Some people have simulated control surface loading (FFB), some do not, and again the user can quietly do their own stability modifications to make their plane handle differently to what the devs attempt to program.

Yes and no. The user can dampen their inputs to the aircraft (e.g. very flat curve around the center), but the user cannot affect the aircraft's response to said inputs. If the aircraft has a tendency to diverge from equilibrium, then it will still do so regardless of what the user's stick curve looks like. A high-wing monoplane like the Storch will still be very stable in the roll axis due to the keel effect. An aircraft with a lot of anhedral is still going to be largely unstable about the roll axis.

Keeping in mind of course that real control columns have a much greater throw than your average consumer-level HOTAS.

MiG-3U

07-15-2012, 05:13 AM

It was actually addressed in the Spitfire Mk V but the longitudinal instability existed from the beginning.

The longitudinal instability existed only if the CoG was in the aft positions as pointed out in the A&AEE report:

(v) Stability - The aircraft is laterally stable at all speeds except in the immediate vicinity of the stall when it is unstable. The aircraft is directionally stable engine 'OFF' and 'ON' at all speeds, but on the climb this is difficult to assess owing to insufficient rudder bias. Longitudinally, the aircraft is stable with centre of gravity forward, but is unstable with centre of gravity normal and aft with engine 'OFF' and 'ON'. Longitudinal stability records are attached

Note that early CoG limits are 5.8" to 8.6" aft the datum point. The revised limits are 5.4" to 7.9" for DeHavilland prop without bob weight (7.5" for Rotol prop).

They published all the warnings and characteristics of the Longitudinal instability in the Operating Notes.

These warning can be found only from the operating notes of the Spitfire II with Rotol prop (most CoG sensitive combination) before the revised CoG limits and bob weights (which were needed only if CoG was too far aft as was case in the NACA tested Spitfire V).

It is kind of hard to argue that the NACA was incapable of performing a simple weight and balance when the RAE fixed the same issue and published warnings in the Operating Notes. The truth is they just did not know what the NACA was talking about as the stability and control criteria was classified at the time and Gates had not completed his visit.

1. RAE criticized NACA static longitudinal stability test and for a good reason. Tests were done only at one position of CoG and that position was aft the revised limits.

2. Operational testing and handbooks of the aircraft were made by A&AEE, not by RAE.

Here is the direct link to the document by Gates:

http://aerade.cranfield.ac.uk/ara/dl.php?filename=arc/rm/2677.pdf

See the page 9. The Spitfire K.9796 was tested at CoG 7" aft the datum point and that is still quite aft given that the range was from 5.4" to 7.9" (revised limits without bobweight and with DeHavilland prop).

Interesting comparison can be made to the Mohawk AX.882 which was tested at CoG 21" behind datum point, rather nose heavy given the range being 19" to 26". And despite forward CoG, the stick force for pull out was about the same as in the case K.9796.

TomcatViP

07-15-2012, 09:13 AM

Interesting comparison can be made to the Mohawk AX.882 which was tested at CoG 21" behind datum point, rather nose heavy given the range being 19" to 26". And despite forward CoG, the stick force for pull out was about the same as in the case K.9796.

Thx for the link.

The comparison with the Hurri values is more interesting IMOHO

NZtyphoon

07-15-2012, 10:27 AM

Here is the NACA Report on Control Characteristics of Spitfire VA specifically stating that the CG of the Spitfire was estimated:

http://i91.photobucket.com/albums/k304/Major_Sharpe/SpitfireVAControlCharacteristics-page-007a.jpg

Crumpp can argue black and blue that NACA accurately calculated the cg properly - the report specifically states this was not the case:

Because no accurate drawings of the Spitfire were available, the calculated location of the mean aerodynamic chord may be somewhat in error....The center-of-gravity location with full military load is not known....center-of-gravity location 31.1 inches behind the leading edge of the wing.

and a Spitfire I CG diagram:
http://i91.photobucket.com/albums/k304/Major_Sharpe/k-9788-cg-diagram.jpg
Datum point 19.5 in aft of wing leading edge
Maximum aft location of cg was 7.6 in (MiG-3U 7.9 to 8.6 in) aft of datum point, 19.5 in aft of the wing leading edge = 27.1 in aft of leading edge (up to 28.1 in) - NACA calculations = 31.1 in aft of leading edge, enough to make a difference in the longitudinal stability (slightly tail heavy).

Crumpp

07-15-2012, 10:44 AM

and a Spitfire I CG diagram:

You are using the wrong variant weight and balance as well as being an actual W/B for a specific aircraft.

There is not any need though to go into any kind of depth in researching this....

The Operating Notes for the type clearly warn the operator of the characteristics the NACA discovered.

Crumpp

07-15-2012, 10:45 AM

These warning can be found only from the operating notes of the Spitfire II with Rotol prop

No they exist in the Spitfire Mk I as well.

NZtyphoon

07-15-2012, 11:04 AM

You are using the wrong variant weight and balance as well as being an actual W/B for a specific aircraft.
Really? Then please show us your definitive cg drawings for all Spitfire Mk Is.

There is not any need though to go into any kind of depth in researching this....

In your opinion - IMO this thread is based on a flawed premise which requires detailed research to point out where it is flawed.

Please explain why the NACA report specifically states that their calculations may be in error.

The Operating Notes for the type clearly warn the operator of the characteristics the NACA discovered.

Clarify how an aircraft tested with the cg further aft than specifications can possibly emulate the control characteristics properly.

Crumpp

07-15-2012, 11:58 AM

All the evidence for the Spitfire Longitundinal instability will be posted in this thread, that includes the Operating Notes, Gates conclusions, the NACA results, stability and control engineering opinion, and the steps the RAE took to fix the longitudinal stability in later Marks.

Really? Then please show us your definitive cg drawings for all Spitfire Mk Is.

The weight and balance is a sideline that the RAE did not even believe.

You don't need comprehensive drawings to do a weight and balance. I will explain the process and how it works both for a type AND the individual aircraft later in detail with documents.

In short, like anything that comes off an assembly line has variation. CG limits is no different and there is a range of acceptable limits for the empty weight CG for the type.

A weight and balance is done when the aircraft is complete and the empty weight CG is estabilished. It must be within that tolerance range for the type but the empty weight CG will be specific to the individual aircraft.

That empty weight CG for that specific aircraft then has its specific range for foward and aft limits based on its authorized configurations. That is why the weight and balance is part of the Pilot's Handbook for that aircraft. It is required documentation and just like the Handbook, propeller logs, engine logs, and airframe logbooks follows the aircraft throughout its life.

The minimum equipment you need to do an accurate weight and balance on any aircraft is a tape measure, plumb bob, string, scales, chaulk, and pen/paper.

The NACA used percentage MAC. Once you know the percentage MAC range, you get all the data from the tape measure and scales for the individual aircraft.

MiG-3U

07-15-2012, 12:47 PM

The basic airframe dimensions of the Spitfires were unchanged up to the Spitfire IX except the nose section and radiator configuration. The loading table is attached, some parts rewritten for clarity. It's for the Spitfire Ia and Ib but the CoG locations are exactly the same for the Spitfire V (as refered in the right corner of the table).

The exact values of the CoG location are following at accuracy of two decimals (verified from drawings and RM 2525), these are values by RAE and slightly different as given by NZtyphoon because mean aerodynamic chord is at different position, datum line being the same:

The lenght of the mean aerodynamical chord is 78.54"
The datum line is 18.65" behind the leading edge of the mean aerodynamical chord
The datum line is 23.60" behind the leading at the wing root
The CoG of the NACA tested Spitfire V was 31.40" behind the leading edge at the wing root and 7.80" behind the datum line.

NZtyphoon

07-15-2012, 12:59 PM

...and the steps the RAE took to fix the longitudinal stability in later Marks.

The weight and balance is a sideline that the RAE did not even believe.

Please prove that the RAE had no belief in weight and balance, and explain how the RAE took steps to fix so-called longitudinal instability when they had no belief in weight and balance.

A weight and balance is done when the aircraft is complete and the empty weight CG is estabilished. It must be within that tolerance range for the type but the empty weight CG will be specific to the individual aircraft.

That empty weight CG for that specific aircraft then has its specific range for foward and aft limits based on its authorized configurations. That is why the weight and balance is part of the Pilot's Handbook for that aircraft. It is required documentation and just like the Handbook, propeller logs, engine logs, and airframe logbooks follows the aircraft throughout its life.

NACA did not have any drawings for the Spitfire and specifically state that their measurements might have been in error - without a weight and loading diagram of the specific aircraft tested there is no way to know whether the aircraft was teetering on instability because it was loaded beyond the usual tolerances.

To claim that this report proves all early Spitfires were unstable is a stretch, particularly when the Supermarine chief test pilot Jeffrey Quill, states in his book that the longitudinal stability of the Spitfire I was okay.

MiG-3U

07-15-2012, 01:36 PM

Here is the revised CoG part of the loading table attached to make clear how the CoG and use of the bob weight (inertia device) were connected in the case of the original standard elevator:

With DeHavilland propeller:
CoG range 5.4"-7.9" aft of datum point, no inertia device needed
CoG up to 8.2" aft of datum point, 3.5 lbs inertia device
CoG up to 8.6" aft of datum point, 6.5 lbs inertia device

With Rotol propeller:
CoG range 5.4"-7.5" aft of datum point, no inertia device needed
CoG up to 7.8" aft of datum point, 3.5 lbs inertia device
CoG up to 8.2" aft of datum point, 6.5 lbs inertia device

Regarding if the currently flying Spitfires have the bob weighs installed, here is link to a picture of the elevator linkage of the Spitfire Vb BL628 (from spitfiresite.com):

http://spitfiresite.com/2010/07/anatomy-of-spitfire-cockpit.html/07ar_fuse_001

Edit: Attached also the quote from Perkins and Hage to show how the use of bob weigh and CoG at aft center of gravity are connected :)

MiG-3U

07-15-2012, 02:02 PM

And as we all love quotes, here is Quill in Spitfire, Portrait of a legend by Leo McKinstry:

TomcatViP

07-15-2012, 02:26 PM

"Convex elevator" ? Does anyone have more details on this ?

Crumpp

07-15-2012, 03:32 PM

Attached also the quote from Perkins and Hage to show how the use of bob weigh and CoG at aft center of gravity are connected

Why are you regurgitating the same stuff I just posted. Puzzling...

Anyway, yes, the bob weight artificially increases the stick forces so that the pilot can have more control.

That is band-aid to fix the longitudinal instability the NACA reported!!!

The fact Supermarine recognized that longitudinal instability and took measures to fix it invalidates any pointy tin foil hat theory the instability did not exist.

Crumpp

07-15-2012, 05:20 PM

Now let's get back to the NACA report so there is a better understanding of the issue.

We will look at a condition of flight essential to a dogfighter. The ability to make abrupt turns.

The pilot must be able to precisely control the amount of acceleration he loads on the aircraft. All aircraft performance depends on velocity. In order to get maximum performance out of the aircraft above maneuvering speed, Va, he needs to be able to make a 6 G turn and not exceed that load factor to prevent damage to the airframe. Below Va, the pilot needs to control the acceleration so that he does not stall the aircraft making the abrupt maneuver as well being able to maintain a maximum performance turn.

Doing that in an early Mark Spitfire was difficult and something only a skillful pilot could perform.

First the NACA report. Abrupt 180 degree turns were conducted at various entry speeds to gauge the level of control the pilot had in maintaining steady accelerations. The turns were also done to the stall point in order to gauge the behavior and amount of control.

"In turns at speeds high enough to prevent reaching maximum lift co-efficient" means turns above Va.

http://img404.imageshack.us/img404/2525/rapidturns.jpg (http://imageshack.us/photo/my-images/404/rapidturns.jpg/)

http://img513.imageshack.us/img513/6480/rapidturns2.jpg (http://imageshack.us/photo/my-images/513/rapidturns2.jpg/)

"By careful flying" a pilot can hold a steady acceleration. That agrees with the Operating Notes warning for the pilot to brace himself against the cockpit to get better control when making turns.

Now lets look at the measured results.

http://img843.imageshack.us/img843/6408/rapidturnfig15.jpg (http://imageshack.us/photo/my-images/843/rapidturnfig15.jpg/)

Here we see in a rapid left turn performed at 223 mph the test pilot is unable to hold constant acceleration on the airframe. Very small variations in stick movement and stick force changes of 1-3lbs results in large fluctuations in acceleration.

Next let's look at the pilots ability to control the accelerations in the pre-stall buffet.

http://img600.imageshack.us/img600/4313/stallbuffet.jpg (http://imageshack.us/photo/my-images/600/stallbuffet.jpg/)

Here we see the pilot was able to load the airframe to 5G's in 1 second to reach the pre-stall buffet 3 times. The smooth positive sloped portion of the curve represents the aircraft flying while accelerations are increasing. The top of the acceleration curve represents the pre-stall buffet. The bottom of the curve represents the stall point.

The take away is:

1. The large accelerations change for very little elevator movement.
2. The very rapid rate at which the pilot was able to load the airframe to 5G's.
3. The equally rapid rate at which the airframe unloaded down to 2G's when the pre-stall buffet was encountered. In 1 second, the aircraft went from 5G's to 2G's due to buffet losses. This means a rapid decay in turn rate resulted.
4. The violence of the pre-stall buffet combined with the longitudinal stability and control caused large fluctuations in the accelerations on the aircraft.

Last part of the NACA we will cover for today is the stick force travel. The amount of stick travel as measured by the NACA was not acceptable.

http://img94.imageshack.us/img94/2621/sticktravel.jpg (http://imageshack.us/photo/my-images/94/sticktravel.jpg/)

Next let's look at the opinion of Stability and Control Engineers on the Early Mark Spitfires.

http://img832.imageshack.us/img832/3063/twofamousairplanes.jpg (http://imageshack.us/photo/my-images/832/twofamousairplanes.jpg/)

http://img855.imageshack.us/img855/7210/twofamousairplanes2.jpg (http://imageshack.us/photo/my-images/855/twofamousairplanes2.jpg/)

http://img825.imageshack.us/img825/4462/twofamousairplanes3.jpg (http://imageshack.us/photo/my-images/825/twofamousairplanes3.jpg/)

http://img404.imageshack.us/img404/6078/skittishspitfire.jpg (http://imageshack.us/photo/my-images/404/skittishspitfire.jpg/)

Tomorrow I will post some of the plethora of references to this same issue of longitudinal instability as found in the Spitfire Mk I Operating Notes from July 1940. You will see the same references or similar to the same issue the NACA measured in the Spitfire Mk II Operating Notes.

There is no doubt that the Air Ministry was aware of the longitudinal instability of the early mark Spitfires.

Crumpp

07-15-2012, 05:46 PM

NACA did not have any drawings for the Spitfire and specifically state that their measurements might have been in error -

Correct, the NACA did their own weight and balance analysis so their numbers might not agree with the RAF's. That has nothing to do with flying the airplane outside of the CG limits.

without a weight and loading diagram of the specific aircraft tested there is no way to know whether the aircraft was teetering on instability because it was loaded beyond the usual tolerances.

You don't need a thing from the manufacturer to do a weight and balance analysis. Your leap of logic requires some pretty hefty suspension of belief. One would have to assume the NACA was incapable of doing a simply weight and balance analysis and constructing a potato chart. That is something every homebuilder in the United States does in his garage. A weight and balance analysis and constructing a potato chart is also something every FBO is capable of doing. It is a routine process in aviation.

You need a few simple tools and the knowledge to run the math is all. It is obvious you don't know what you are talking about but are only trying to muddy the waters in defense of a gameshape.

You do not understand the process and do not realize the datum point is just a random point picked to begin measurements.

So what if the NACA picked a line of rivets that is ~5 inches away from the one Supermarine chose on the back of the firewall instead of the front.....

The reference datum point can be anywhere the person doing the weight and balance analysis decide's to put it.

Crumpp

07-15-2012, 06:02 PM

MAC as measured by RAE:

19.5+8.4 = 27.9/84 = 33.2%

NACA CG as flown = 31.4% MAC

The NACA flew the Spitfire with the CG 1.8% MAC FORWARD of the aft CG limit as defined by Supermarine.

TomcatViP

07-15-2012, 06:26 PM

Don't loose your time commenting "comments", Crumpp. Hold the line.

Ended already my long reading for tonight. Enjoyed it as much as any other good entertainment as it shld be from any interested reader in aviation. Sad you don't sell any popcorn. ;)

So now I am waiting for the interludes played by our looney toons :rolleyes:

~S

PS: that story about the NACA not having any drawing is true... but they neither had any for the 109 they tested ;)

Crumpp

07-15-2012, 06:32 PM

that story about the NACA not having any drawing is true... but they neither had any for the 109 they tested

Yep, it is not like switching aviation fuel. Weight and balance analysis is simple and easy to do.

MiG-3U

07-15-2012, 07:42 PM

Why are you regurgitating the same stuff I just posted. Puzzling...

Nothing puzzling there, you just forgot to underline the most relevant part for this thread and I fixed it for you; the bob weigh was added because the CoG had slipped too far aft causing londitudinal instability just like Quill notes.

The fact Supermarine recognized that longitudinal instability and took measures to fix it invalidates any pointy tin foil hat theory the instability did not exist.

Yep, when the CoG slips too far back, instability exist in pretty much every airplane, including Spitfire and Mustang. Bob weighs were used in some models of both fighters exactly for the same reason: CoG shift. Both aircraft were also stable when the CoG was forward enough.

Here is again A&AEE on stability of the early mark Spitfire:

http://www.spitfireperformance.com/k9787-fuel.html

(v) Stability - The aircraft is laterally stable at all speeds except in the immediate vicinity of the stall when it is unstable. The aircraft is directionally stable engine 'OFF' and 'ON' at all speeds, but on the climb this is difficult to assess owing to insufficient rudder bias. Longitudinally, the aircraft is stable with centre of gravity forward, but is unstable with centre of gravity normal and aft with engine 'OFF' and 'ON'.

CoG was at 5.8" aft datum line when the airplane was found to be longitudinally stable, that is 2" more forward than Naca tested. Note that Spitfire IX had CoG around 5" aft datum line at service load, no need for bob weigh.

Crumpp

07-15-2012, 08:03 PM

Slow down and tell me where you get the 78.54 MAC on that sheet.

Do you know what percentage MAC is??

The reason the NACA used percentage MAC is because they did their own weight and balance analysis.

The ONLY number that is comparible...is the percentage MAC!!!

MAC as measured by RAE:

19.5+8.4 = 27.9/84 = 33.2%

NACA CG as flown = 31.4% MAC

The NACA flew the Spitfire with the CG 1.8% MAC FORWARD of the aft CG limit as defined by Supermarine.

If you want to use your 78.54 in MAC with our most narrow aft CG limit...

CoG range 5.4"-7.9" aft of datum point, no inertia device needed

(19.5 + 5.4) / 78.54 = 31.7% MAC

NACA CG as flown = 31.4% MAC

The NACA flew the Spitfire with the CG .3% MAC FORWARD of the aft CG limit as defined by Supermarine.

Crumpp

07-15-2012, 08:19 PM

Longitudinally, the aircraft is stable with centre of gravity forward, but is unstable with centre of gravity normal and aft with engine 'OFF' and 'ON'.

http://www.spitfireperformance.com/k9787-fuel.html

Check it out...That is what the NACA said.....

:rolleyes:

Crumpp

07-15-2012, 08:33 PM

Ok let's not go down the rabbit hole again.

You are using a weight and balance sheet that incorporates the longitudinal stability fix and is from February 1944 to prove the NACA conclusion was not correct.

Yes, the RAE addressed the issue of the longitudinal instability in the Spitfire around 1942. However, the Spitfires used in the Battle of Britain did not benefit from the fix.

This is Spitfire K-9787 and was tested in June, 1939.

http://www.spitfireperformance.com/k9787-fuel.html

If you click on the center of gravity link at the bottom of the page...

The weight and balance diagram is K-9788, the very next Spitfire off the production line.

http://www.spitfireperformance.com/k-9788-cg-diagram.jpg

We can eliminate the February 1944 document from the thread as not applicable and conclude it is the result of the NACA findings.

Which brings us back too:

MAC as measured by RAE:

19.5+8.4 = 27.9/84 = 33.2%

NACA CG as flown = 31.4% MAC

The NACA flew the Spitfire with the CG 1.8% MAC FORWARD of the aft CG limit as defined by Supermarine.

Glider

07-15-2012, 08:44 PM

You still have the question that has yet to be addressed. If in theory the Spitfire was so poor in its stability, why did all the pilots who flew it of every nation, sing its praises?

I should make clear that I do not doubt the calculations, but its a basic difference

MiG-3U

07-15-2012, 08:52 PM

Slow down and tell me where you get the 78.54 MAC on that sheet.

Report RM2535

http://aerade.cranfield.ac.uk/ara/dl.php?filename=arc/rm/2535.pdf

and (wing and datum point are the same on the Spitfire IX)

http://www.spitfireperformance.com/ab197datum.gif

The reason the NACA used percentage MAC is because they did their own weight and balance analysis.

The ONLY number that is comparible...is the percentage MAC!!!

They gave exact reference point, wing leading edge at the root and they (NACA) admited that their measurements for MAC maybe somewhat in error.

WTF, are we going down the rabbit hole like your "superchargers see pressure altitude"???

Well, just like in the other discussion, you ignore the data (USAF handbook) which does not support you and post some irrelevant stuff or accusations.

I don't play that game, let the people see the data and decide themselves.

MiG-3U

07-15-2012, 09:26 PM

You are using a weight and balance sheet that incorporates the longitudinal stability fix and is from February 1944 to prove the NACA conclusion was not correct.

Yes, the RAE addressed the issue of the longitudinal instability in the Spitfire around 1942. However, the Spitfires used in the Battle of Britain did not benefit from the fix.

The only thing that changed was the revised CoG limits for the aircraft with Rotol propeller and bob weighs if the CoG went beyond the normal limits, as often happened in the case of the Spitfire V.

As Quill noted, slight unstability was built in for purpose and prefered by pilots. However, stability margins were narrow and improper loading could easily cause problems.

Crumpp

07-15-2012, 09:44 PM

Report RM2535

Which has what to do with the MAC on the weight and balance sheet? You can be they did their own weight and balance analysis too!!!

The only thing that changed was the revised CoG limits for the aircraft with Rotol propeller and bob weighs if the CoG went beyond the normal limits, as often happened in the case of the Spitfire V.

Negative.

Spitfire K-9788 shows an aft CG that is 33.2%.

The most aft MAC with the Feb 1944 revision is 31.7%.

They closed up the CG limits to address the longitudinal instability.

You have presented the solution to the problem in an effort to claim the problem never existed.

Crumpp

07-15-2012, 09:46 PM

Please start another thread if you feel the need to continue down this rabbit hole claiming the NACA could not perform a weight and balance analysis.

Crumpp

07-15-2012, 09:57 PM

MiG-3U

07-15-2012, 10:12 PM

Which has what to do with the MAC on the weight and balance sheet?
It gives exact location of the leading edge needed for calculation (p.7).

Spitfire K-9788 shows an aft CG that is 33.2%.

The most aft MAC with the Feb 1944 revision is 31.7%.

I claimed normal service load:

7.7" at normal service load 1939
7.9" aft limit for DeHavilland without inertia device
7.5" aft limit for Rotol without inertia device

This means that on normal combat load there was only change in the case of the Rotol prop assuming that aircraft was properly loaded.

Besides, the revised limits were originally issued sometime around 41/42.

Otherwise you seem to have chosen same tactics as in the FTH discussion so my part end here now.

Cpt Doggles, you see my point now.

Fenrir

07-15-2012, 10:14 PM

You present this like it's some revelation Crummp.

If you have done *any* research you'll have read Quill's book, which you should have done considering you're talking about the Spitfire and it's flying characterisics as it's practically source point one - he test flew the aeroplane in all it's marks over 10 years and countless hours - this makes him somewhat more credible than you, so you'll forgive me if I take his word over your clearly subjective posts.

The point is addressed fully and sufficiently in there to make all your posting here as redundant it is cherry picked.

I'm not going to bother posting it here, if you're serious about research, and truly objective you'll read it and come back here and retract some of this frankly irksome Spitfire smear campaign.

Crumpp

07-15-2012, 11:41 PM

Otherwise you seem to have chosen same tactics as in the FTH discussion so my part end here now.

What "tactic" is that? :confused:

You mean showing you the question on an A&P exam?

If a turbo engine is rated at 310 HP up to 18,000', the altitude specified is pressure altitude?

False, the altitude specified is density altitude

http://quizlet.com/2496371/print/

Start another thread on the weight and balance or send me a PM. I would be happy to walk you through the steps in determining percentage MAC.

It is not that hard to do. You will understand it and see how ridiculus the theory the NACA could not do one really is!!

In presenting a February 1944 weight and balance document and for the purposes of this discussion on 1940 Spitfires:

You have presented the solution to the problem in an effort to claim the problem never existed.

NZtyphoon

07-16-2012, 12:48 AM

That empty weight CG for that specific aircraft then has its specific range for foward and aft limits based on its authorized configurations. That is why the weight and balance is part of the Pilot's Handbook for that aircraft. It is required documentation and just like the Handbook, propeller logs, engine logs, and airframe logbooks follows the aircraft throughout its life.

Completely wrong, neither individual CG drawings, nor weight and balance sheets were issued with the Pilot's Notes - fighter pilots especially were rarely allocated their own aircraft and had to take what was made available. Pilot's Notes General, Section 7:
http://i91.photobucket.com/albums/k304/Major_Sharpe/PNGenp7CG-page-001.jpg

Each and every aircraft type used by the RAF and FAA had generic cg/w&b sheets printed, which had fixed fore and aft limits, beyond which the flight qualities started to suffer: Lancaster cg drawings:

http://i91.photobucket.com/albums/k304/Major_Sharpe/lanccg2-page-001.jpg

Loading diagram up to L7532...
http://i91.photobucket.com/albums/k304/Major_Sharpe/Lanccg1-page-002.jpg

L7533 on...
http://i91.photobucket.com/albums/k304/Major_Sharpe/lanccg2-page-002.jpg

Careful study shows the cg limits fore and aft were identical, despite different equipment and loadings - the airframe was the same, so the limits stayed the same - those fore and aft limits for ALL early Marks of Merlin engined Spitfires were identical, Mk I to Mk V and were not changed until the modified elevators with larger mass balances were introduced.

It was the responsibility of the groundcrew to ensure that the cg limits were adhered to. The only crews that needed to know the position of the cg were bomber crews with their large disposable loads and multiple crew positions

This is how the cg was calculated:

http://i91.photobucket.com/albums/k304/Major_Sharpe/lanccgcalc1-page-001.jpg

http://i91.photobucket.com/albums/k304/Major_Sharpe/lanccgcalc2-page-001.jpg

http://i91.photobucket.com/albums/k304/Major_Sharpe/lanccgcalc3-page-001.jpg

Relatively small changes in equipment weight and equipment position could still make a big difference to the final cg - a few kg a few inches aft of the rearmost cg position could upset the handling of an aircraft;

NACA made it quite clear that their calculations for the Spitfire may well have been in error - until Crumpp can prove that NACA had calculated the cg position correctly, according to early Spitfire cg data charts, the report needs to be viewed with some suspicion.

http://i91.photobucket.com/albums/k304/Major_Sharpe/SpitfireVAControlCharacteristics-page-007a.jpg

Now let's get back to the NACA report so there is a better understanding of the issue.

We will look at a condition of flight essential to a dogfighter. The ability to make abrupt turns.

The pilot must be able to precisely control the amount of acceleration he loads on the aircraft.
Doing that in an early Mark Spitfire was difficult and something only a skillful pilot could perform.

Where did you get this nonsense? Show me accounts of even trainee pilots who found manoeuvring the early marks of Spitfire difficult - I repeat Supermarine's Chief Test Pilot Jeffrey Quill stated categorically that there was no problem with the longitudinal stability of early Mk I & II Spitfires.

Glider

07-16-2012, 07:16 AM

A lot of words and a lot of effort into defend a position or a view but nothing to address the basic question:

You still have the question that has yet to be addressed. If in theory the Spitfire was so poor in its stability, why did all the pilots who flew it of every nation, sing its praises?

There is of course another inconvenient point that should be considered and that is have you done these calculations on the Me109E?

I say this because if you believe that the Spitfire to be dangerous and the German pilots considered the Spitfire to be much easier to fly than the Me109E, How dangerous do you think the Me109 was?

gimpy117

07-16-2012, 07:50 AM

there's a difference between "singing praises" and having a stable aircraft. Data is not subjective, data is data. I'm sure once you got how to know the spitit was a wonderful aircraft...but as far as I know it's not an aircraft you can just "fly" and get maximum performance out of

winny

07-16-2012, 10:43 AM

I have some questions. @ Crumpp
We're other contemporary aircraft also tested in this way?
It's all good and well saying the Spit did this, this and this but, how did other aircraft stack up?

Also, how exactly do you intend to model this phenomenon in CLOD?

It seems to depend on stick forces and stick forces aren't calculated in CLOD? Or are they? We all know that the controls on these aircraft stiffend significantly at high speeds, that's not accounted for either.

So really the most important point, considering where we are is, what would you expect to be done to the FM to replicate this?

Crumpp

07-16-2012, 12:23 PM

We're other contemporary aircraft also tested in this way?

Yes, many other aircraft were tested. My plan is to do threads on the stability and control of all the main fighters involved in the game.

I am sure I will be hated by both "red and blue".

I don't want to de-rail my own thread so if you want an in-depth discussion we will start another one.

It's all good and well saying the Spit did this, this and this but, how did other aircraft stack up?

Well, subsonic incompressible flow theory for symmetrical airfoils will give a one dimensional picture of an aircraft. The stability and control characteristics help to complete the picture.

Stability and control was a new science during WWII. Many of the aircraft have issues and those issues should be modeled.

For example, a symmetrical airfoil analysis of the Spitfire and Hurricane would give the impression the Hurricane was the 2nd rate fighter. In fact, the Hurricane was the real workhorse and an airplane the Bf-109 pilot should respect. Why?

The Hurricane was a very stable and maneuverable aircraft. Air combat is not about fancy flying on a warm sunny day. It is about getting bullets on a target. The Hurricane did not have the convergence issues and was an airplane the average pilot could quickly get guns on target as well as accurately shoot from to destroy his opponent.

I am sure there is nothing you can teach a Spitfire ace about finessing an airplane or over controlling.

Also, how exactly do you intend to model this phenomenon in CLOD?

So really the most important point, considering where we are is, what would you expect to be done to the FM to replicate this?

Well that is up to the devs as I don't know the game engine. If they are using the standard Cm calcs, then it should be rather straight forward.

Sandstone

07-16-2012, 12:43 PM

In fact, the Hurricane was the real workhorse and an airplane the Bf-109 pilot should respect. Why?

The Hurricane was a very stable and maneuverable aircraft. Air combat is not about fancy flying on a warm sunny day. It is about getting bullets on a target. The Hurricane did not have the convergence issues and was an airplane the average pilot could quickly get guns on target as well as accurately shoot from to destroy his opponent.

Air combat is often about speed and climb rate. The Hurricane was effective against bombers but less so against the Bf-109 simply because it was significantly slower and had a poorer rate of climb than the German aircraft. I hope you aren't trying to argue that the pitch sensitivity of the early Spitfire actually made it less effective against fighters than the Hurricane. That would be a very odd thing to be claiming.

TomcatViP

07-16-2012, 12:53 PM

Air combat is often about speed and climb rate. The Hurricane was effective against bombers but less so against the Bf-109 simply because it was significantly slower and had a poorer rate of climb than the German aircraft.

At most combat altitude, the Spit had the same prob.

fruitbat

07-16-2012, 01:08 PM

At most combat altitude, the Spit had the same prob.

Yes, but by a lesser margin, making that particular problem therefore less of an issue than in the Hurricane.

TomcatViP

07-16-2012, 01:22 PM

Yes, but by a lesser margin, making that particular problem therefore less of an issue than in the Hurricane.

+1

but we are OT now ;)

Crumpp

07-16-2012, 01:34 PM

Crumpp

07-16-2012, 01:52 PM

until Crumpp can prove that NACA had calculated the cg position correctly

It is proven. The math has been done several times in this thread. It is not my fault you don't understand it and continue to argue in ignorance.

If you start another thread, I will be glad to go over MAC calculations with you.

The only important information is the NACA's report is their percentage MAC.

What you are taking as evidence of an error is the NACA explaining how they did the weight and balance (percentage MAC) and their numbers might not match.

Percentage MAC does not require the specific numbers to match as long as the margin of error is the same throughout. It is a non-dimensional proportion!!!!

Look at your RAF documents!!! The RAF has the MAC as both 84" and 78.54"!!

Do you really think the RAF did not know what the wing chord was on their own airplane???

Because of the stations chosen for LEMAC and TEMAC, the NACA choose 85" as the MAC.

The fact that has to be explained over and over to folks who pass themselves off as "Gods of Aviation" is puzzling at best. :confused:

winny

07-16-2012, 01:57 PM

Well that is up to the devs as I don't know the game engine. If they are using the standard Cm calcs, then it should be rather straight forward.

OK, let me put it another way, what behaviour would you expect to see?

In layman's terms. What do you expect the Spitfire to do that it isn't already doing in game? Without going into the game engine.

Something like 'if you do xyz then this happens', please.

Just so everyone understands what it is you're asking for, not just the brainiacs..

Al Schlageter

07-16-2012, 02:18 PM

Originally Posted by Crumpp View Post
That empty weight CG for that specific aircraft then has its specific range for foward and aft limits based on its authorized configurations. That is why the weight and balance is part of the Pilot's Handbook for that aircraft. It is required documentation and just like the Handbook, propeller logs, engine logs, and airframe logbooks follows the aircraft throughout its life.

The RAF did not have a Pilot's Handbook either, they had Pilot Operating Notes. Your post is nitpicky and irrelevant.

First there is a Pilot's Handbook and then there is no Pilot's Handbook. :eek:

TomcatViP

07-16-2012, 03:32 PM

You shld open another thread on Crumpp.

But it might be that an edito in the next Cosmopolitan issue will be more suited to your prose.

Al Schlageter

07-16-2012, 03:36 PM

Crumpp does that alot, he hopes he can hide it in the reams of pseudo-braniac blabber.

It is truly hilarious that he says his own post is nitpicky and irrelevant. :(

fruitbat

07-16-2012, 03:39 PM

I await with interest his thread on the 109.

bongodriver

07-16-2012, 03:44 PM

I await with interest his thread on the 109.

Indeed, that's the one I'm really looking forward to aswell.

Crumpp

07-16-2012, 04:35 PM

It is required documentation and just like the Handbook, propeller logs, engine logs, and airframe logbooks follows the aircraft throughout its life.

Holy out of context, Batman!!!

:rolleyes:

You shld open another thread on Crumpp.

I am hoping the Mods will just clean it up. Delete all the pointy-tin foil hat "NACA can't do weight and balance" and sour grapes comments from "lurkers with an agenda".

OK, let me put it another way, what behaviour would you expect to see?

In layman's terms. What do you expect the Spitfire to do that it isn't already doing in game? Without going into the game engine.

Something like 'if you do xyz then this happens', please.

Just so everyone understands what it is you're asking for, not just the brainiacs..

Winny, I have a few more post's to put out before we get into the nuts and bolts for the game. Let's not put the cart before the horse. I would like to get somewhat of a consense and some input from people who know more about the limits of the game.

I hope that after defining the stability and control behaviors that represent the early mark spitfire, we should be able to produce a list that is reproduceable in the game.

gimpy117

07-16-2012, 05:08 PM

well personally I would expect a much lower Roll rate at speed, and a very sensitive Unbalanced Elevator (unbalanced meaning it needs much more roll input than pitch).

winny

07-16-2012, 05:13 PM

Winny, I have a few more post's to put out before we get into the nuts and bolts for the game. Let's not put the cart before the horse. I would like to get somewhat of a consense and some input from people who know more about the limits of the game.

I hope that after defining the stability and control behaviors that represent the early mark spitfire, we should be able to produce a list that is reproduceable in the game.

Put the horse before the cart? You're on the CLOD forum so I just want to know, even in a ballpark kinda way what all this means to a Spitfire in CLOD.

I can look at this thread all day and I'm never gonna be able to relate all this info and graphs and whatever else to what is actually supposed to be happening to the Spitfire?

Treat me like the idiot you normally do and spell it out for me!

Are we talking a small amount of movement, wobble, or whatever it is that this instability creates, in RL?

You keep saying that it's unstable but I still don't know What you actually mean.

Robo.

07-16-2012, 05:48 PM

What exactly is wrong with the Spitfire in game regarding control and stability?

bongodriver

07-16-2012, 05:49 PM

In a nutshell Winny, the Spit was neutrally stable longitudinally, this is an undisputed fact, in very basic terms this means it was very light on the controls in pitch, this basically means the pilot needed very little (only 2 fingers) effort to pitch the aircraft, the other benefit of this is it means the aircraft is very manouverable in the pitch plane too, hence why the Spit was so good at turning, the down side to highly sensitive pitch is the aircraft can be overstressed if used harshly at high speeds and may also mean the aircraft can be stalled very easily too, what this doesn't account for is the fact that despite how the Spit looks on paper all the potentially negative issues never really manifested and the Spit ended up with a reputation of being a 'delight' by the people whose oppinions 'really' count i.e. the pilots, who it turns out were largely not so 'ham fisted' and were able to use sensory feedback to allow the airframe to 'talk' to them and use the effect to it's limits, what Crumpp would like to see is the Spit being 'unforgiving' and basically discourage all of us to use this effect because NACA said it was a problem therefore he canno't accept the truth (we have all seen how resistant he is to hard evidence), it's purely coincidental that this would further pork the Spitfire :rolleyes:

Fenrir

07-16-2012, 05:55 PM

You keep saying that it's unstable but I still don't know What you actually mean.

Hey Win, here's the laymans

I'm flying staright and level, trimmed for cruise and hands off in an aeroplane and I hit a pocket of rough air. The right wing drops a fraction:

Stable: aircraft will settle back to it's trimmed state automatically thanks to inherent clever design - basically it's to do with differing lift vectors and their strength and direction. This is great for trainers, light aircraft and commercial machines as it means a minimum of pilot effort to fly the plane in straight lines. However it also means that the plane will resist slightly manouevres initiated by the pilot, cos it just wants to fly straight and level! Not great for fighter aircraft.

Neutrally stable: The plane will stay at that angle of bank and unless controls are manipulated will not return to it's original attitude. More workload for the pilot but generally not hard to fly, just requires more attention.

Unstable - the aircraft continues or even accelerates the wing drop to the right. Without pilot interaction/correction the manoevre would continue or even amplify till 'bad things' happen. Aircraft of this nature are tiring to fly because you're constantly fighting the plane - like being balanced on a pin and in asituation where even your control inputs are being amplified. Not fun. A good example of this is the P-51B/D with the rear fuselage tank full; it pushed it's CoG back far enough that it took it to the limit of acceptable controllability - there is a quote by Bud Anderson where engaged before he could empty this fuel tank he ended up in a turning fight with the nose still pitching up and round but he had nearly full forward stick input to try and keep it from throwing itself into a spin.

Now Crummps agenda is based on one report of a Mk. V with which he wishes to tarnish the handling of all Spitfires, despite reams of evidence to the contrary.

In truth there were some issues with Mk Vs being not correctly loaded (they carried quite a bit more kit in them than the earlier Mks) and a short term measure of intoducing bobweights into the elevator control circuit ('g' acting on the bob weight during pitching manoevres actuallly weighted the control column to provide a resistance to up elevator input). As this problem was investigated, and it's catalysts understood, better and more careful loading instructions, and ultimately a redesigned elevator mass blance made the bob weights obsolete.

Was the Spitfire's CoG range small? Yes. And it didn't take much to put it close to or beyond them. However, if you've done your reading nearly every one who's flown the thing, in whatever Mk, speaks glowingly of it's handling. Sure there were lemons and I suspect the NACA variant was an old war weary machine not in best of trim, but it seems foolish to take the evidence of one report against a veritable sea of contrary opinion.

TomcatViP

07-16-2012, 06:12 PM

... the NACA variant was an old war weary machine not in best of trim...

The RAE had the same conclusion. (Re-)read the report.

But they might hve been also unlucky and get a war weary machine ? Hummm ... might hve been the 5th German column

Glider

07-16-2012, 06:13 PM

A SPit Va in 1943 in the USA is going to be a tired machine

However we still have the basic questions

If in theory the Spitfire was so poor in its stability, why did all the pilots who flew it of every nation, sing its praises?

There is of course another inconvenient point that should be considered and that is have you done these calculations on the Me109E?

I say this because if you believe that the Spitfire to be dangerous and the German pilots considered the Spitfire to be much easier to fly than the Me109E, How dangerous do you think the Me109 was?

Any comments

TomcatViP

07-16-2012, 06:15 PM

OT. Deleted

CaptainDoggles

07-16-2012, 07:05 PM

10. Off topic discussion - in full or in part. Purposeful and/ or continuous off topic discussion.

Here's a quote from another interesting sticky. Start another thread if you want to keep going.

winny

07-16-2012, 07:11 PM

Hey Win, here's the laymans...

Thank you for taking the time to explain it.. My head has stopped hurting!

I'm no aerodynamics expert, but I am a very keen amateur historian, BoB being my area of expertise. I'm inclined to agree with you. I've read many, many combat reports, memoirs, interviews written by the people who were there and it's hard to believe that this issue was widespread, or severe. I've never read of anyone complaining about it. Quill and Henshaw both mention problems they encountered whilst testing and this wasn't one of them.

robtek

07-16-2012, 07:19 PM

CaptainDoggles

07-16-2012, 07:22 PM

robtek

07-16-2012, 08:04 PM

Sorry bongo,
but your posts can be more readily interpreted as
first: a attack on the person, not the post
and second: as the endeavour to keep the status quo of the spit controls.
You seem to be too much emotional influenced, imo.
But thanks anyway, for supporting my position.

MiG-3U

07-16-2012, 08:20 PM

Ok, one more as I've been asked how to do the CoG calculation.

The dimensions can be found from the AB197 graph:

http://www.spitfireperformance.com/ab197datum.gif

and from page seven of the RM2535:

http://aerade.cranfield.ac.uk/ara/dl.php?filename=arc/rm/2535.pdf

Lenght of aerodynamical mean chord (MAC): 78.54"
Location of datum line: 18.65" behind leading edge at MAC
Aft limit at MAC: 34% 26.7036" behind leading edge
Aft limit at wing root: 2.638' = 31.656" behind leading edge
CoG used by NACA: 31.4" behind leading edge at wing root

The rest is simple math:
Aft limit behind datum line at MAC: 26.7036" - 18.65" = 8.05"
Datum line behind leading edge at wing root: 31.656" - 8.05" = 23.6024"
NACA CoG behind datum line: 31.4" - 23.6024" = 7.7976"
NACA CoG location at MAC behind leading edge: 18.65" + 7.7976" = 26.4476"
NACA CoG % at MAC: 26.4476" / 78.54 * 100 = 33.6741%

Over and out.

NZtyphoon

07-16-2012, 08:41 PM

winny

07-16-2012, 09:16 PM

NACA reports on the spitfire can be found here (http://ntrs.nasa.gov/search.jsp?R=19930092582&hterms=Spitfire&qs=Ntx%3Dmode%2520matchall%26Ntk%3DAll%26N%3D17%26 Ntt%3DSpitfire) for anyone who would like to read the whole thing.

Downloadable PDF.

Edit: here's (http://ntrs.nasa.gov/search.jsp?R=19930092581&hterms=Spitfire&qs=Ntx%3Dmode%2520matchall%26Ntk%3DAll%26N%3D17%26 Ntt%3DSpitfire) a very interesting document on Spitfire stalling characteristics. NACA again.

Fenrir

07-16-2012, 09:25 PM

I think the fact that you have to return the stick almost to neutral after entering a high g turn (>3 g) to prevent oversteering in a Spitfire should be in game, also the very sensible elevator with large reaction for small inputs and the roll rate as documented.
This will be a problem for ham-handed pilots, but a delight for the virtuosos, as it was in RL.
I don't see that as "porking" the Spit further, but to give it the characteristics that made it famous.
Every aircraft in CoD should reflect its pro's and con's as they where documented then.

These characteristics you describe are NOT representative of all Spitfires. Therefore they should NOT be in game. Read again my post on stability. It affected *some* - and it seems I need to remind some people here that does not mean all - Mk V aircraft. A Mk V is NOT a Mk I, or Mk II.

All I can suggest is that you guys go away and read the books I've read, go further make even more research and come back and make an informed opinion then. Please for pity's sake do not take the one single example of an agenda driven poster as gospel.

The NACA test discovered what they discovered - I can't argue with their findings, FOR ONE PARTICULAR AIRCRAFT. However I cannot agree that these are representative of the breed. And as for relevance, well, I've said it already. A Mk V is not a Mk I.

CaptainDoggles

07-16-2012, 09:38 PM

The NACA test discovered what they discovered - I can't argue with their findings, FOR ONE PARTICULAR AIRCRAFT. However I cannot agree that these are representative of the breed.

What is it about the tested aircraft that makes it not a representative sample of the other aircraft?

TomcatViP

07-16-2012, 09:39 PM

These characteristics you describe are NOT representative of all Spitfires. Therefore they should NOT be in game. Read again my post on stability. It affected *some* - and it seems I need to remind some people here that does not mean all - Mk V aircraft. A Mk V is NOT a Mk I, or Mk II.

All I can suggest is that you guys go away and read the books I've read, go further make even more research and come back and make an informed opinion then. Please for pity's sake do not take the one single example of an agenda driven poster as gospel.

The NACA test discovered what they discovered - I can't argue with their findings, FOR ONE PARTICULAR AIRCRAFT. However I cannot agree that these are representative of the breed. And as for relevance, well, I've said it already. A Mk V is not a Mk I.

Did RAE and NACA test the same aircraft ? Because so far we can see they draw the same conclusions.

And oh nasty they are, they even gave some recommendations in the handbook. I guess that they wanted to wage a war 70 years latter on a dark corner of the internet ;)

robtek

07-16-2012, 09:46 PM

The "agenda driven" shoe fits some feet here, i believe.

NZtyphoon

07-16-2012, 09:52 PM

What is it about the tested aircraft that makes it not a representative sample of the other aircraft?

There are some awkward little phrases in the NACA test viz:

http://i91.photobucket.com/albums/k304/Major_Sharpe/SpitfireVAControlCharacteristics-page-007a.jpg

Now, until Crumpp, or anyone else, can prove beyond reasonable doubt that NACA got their cg calculations right there is a question mark over the longitudinal stability of this Spitfire VA as tested.

CaptainDoggles

07-16-2012, 10:05 PM

You know Crumpp's right about expressing CG as a percentage of MAC. The Datum point doesn't have to be in the same spot for the results to be valid. That's why it's called a datum point.

Fenrir

07-16-2012, 10:10 PM

Did RAE and NACA test the same aircraft ? Because so far we can see they draw the same conclusions.

And oh nasty they are, they even gave some recommendations in the handbook. I guess that they wanted to wage a war 70 years latter on a dark corner of the internet ;)

Can you direct me to the RAE test please? I've not read it.

Tomcat, I'm not interested in getting into a slanging match, but I'm finding your tone a little condescending. Can we both agree to keep our future posts a little less aggressive? I'm just trying to present the whole picture as I understand it, without fixating on one source.

Likewise Robtek - I have an agenda, true; I'd like to see every aircraft represented as accurately as possible with the widest possible references to minimise the possibility of error. I just happen to know a great deal about a few aeroplanes (P-38 and P-51 amongst them) with the Spitfire being high on the list. My reference library is not exactly small though by no means complete, and it has been thoroughly absorbed over 20 years. So, you'll exuse me for calling someone out if I think they are presenting data that is either unrepresentative, of poor relevance or inaccurate, on a subject i know a great deal - but not all, admittedly - about.

I'm not after a super plane in game; I simply want both sides to have the pros & cons that the prototypical aircraft had. No more, no less.

lane

07-16-2012, 11:03 PM

Can you direct me to the RAE test please? I've not read it.

Tomcat, I'm not interested in getting into a slanging match, but I'm finding your tone a little condescending. Can we both agree to keep our future posts a little less aggressive? I'm just trying to present the whole picture as I understand it, without fixating on one source.

Hi Fenrir,

Here's some of what I've found that might be of interest:

NACA A.C.R., Sept 1942: Measurments of the Flying Qualities of a Supermarine Spitfire VA Airplane (http://www.wwiiaircraftperformance.org/NACA-Spitfire-V-Flying.pdf)
NACA A.C.R., Sept 1942: Stalling Characteristics of the Supermarine Spitfire VA Airplane (http://www.wwiiaircraftperformance.org/NACA-Spitfire-V-Stalling.pdf)

http://www.wwiiaircraftperformance.org/rae1106_Page_1.jpg
http://www.wwiiaircraftperformance.org/rae1106_Page_2.jpg

Perhaps also of interest: R & M No. 2535 High-speed Wind-tunnel Tests on Models of Four Single-engined Fighters (Spitfire, Spiteful, Attacker and Mustang) (http://www.wwiiaircraftperformance.org/2535.pdf)

Fwiw from A. & A.E.E. Spitfire I report 15 June 1939 (http://www.spitfireperformance.com/k9787-fuel.html):

http://www.spitfireperformance.com/k9788-stability.jpg

NZtyphoon

07-17-2012, 12:11 AM

You know Crumpp's right about expressing CG as a percentage of MAC. The Datum point doesn't have to be in the same spot for the results to be valid. That's why it's called a datum point.

Crumpp wasted countless hours nitpicking the 100 Octane threads with minute, forensic examination of every single little detail - his contention, that the early marks of Spitfire had longitudinal stability problems which needs to be replicated by this game, needs to be proven to the same level that he demanded for 100 Octane fuel; nothing less should do.

CaptainDoggles

07-17-2012, 12:40 AM

Crumpp wasted countless hours nitpicking the 100 Octane threads with minute, forensic examination of every single little detail - his contention, that the early marks of Spitfire had longitudinal stability problems which needs to be replicated by this game, needs to be proven to the same level that he demanded for 100 Octane fuel; nothing less should do.

That 100-octane thread was monumentally stupid on all sides. It just does not matter, even remotely, what percentage of Spitfires were on 100 vs how many were on 87. Both should appear in the game, and both now do appear in the game (performance problems notwithstanding).

Vendettas aside, the sheet that Lane posted looks interesting.

I'm not 100% clear on what those graphs are supposed to be representing, but if we look at #4 for example, it shows the airspeed diverging wildly from equilibrium, which I would assume is due to the aircraft doing the rollercoaster "porpoise" motion.

A stable aircraft should return to equilibrium, not diverge from it.

Crumpp

07-17-2012, 02:47 AM

Crumpp

07-17-2012, 02:58 AM

Lenght of aerodynamical mean chord (MAC): 78.54"

The rest is simple math:
Aft limit behind datum line at MAC: 26.7036" - 18.65" = 8.05"
Datum line behind leading edge at wing root: 31.656" - 8.05" = 23.6024"
NACA CoG behind datum line: 31.4" - 23.6024" = 7.7976"
NACA CoG location at MAC behind leading edge: 18.65" + 7.7976" = 26.4476"
NACA CoG % at MAC: 26.4476" / 78.54 * 100 = 33.6741%

:rolleyes:

MiG-3U

07-17-2012, 05:16 AM

You know Crumpp's right about expressing CG as a percentage of MAC. The Datum point doesn't have to be in the same spot for the results to be valid. That's why it's called a datum point.

There is only one accurate reference point for the CoG in the NACA report, the distance of the CoG from the leading edge at the wing root and that is given as 31.4". NACA admits that their measurements for MAC maybe in error and we can easily see that there is error because in the RM2535 the 34% CoG location at the RAE measured MAC is also given same way as distance from the leading edge at the wing root and the value is 2.638' which is 31.656". Even with these values only we can estimate that the real CoG location was about 33.7% at the MAC given by RAE instead 31.4% claimed by NACA (and NACA admited that their value might be wrong).

As we know accurate reference point at the wing root and dimensions for MAC used by RAE and A&AEE and datum line, we can also easily calculate these.

Lenght of the MAC measured by RAE and A&AEE is 78.54" (or 6,54') and position 31.4" behind leading edge at root is 26.4476" at MAC and that means that CoG was at position 33.6741% in the NACA tests using RAE and A&AEE dimensions.

However, British documentation gives CoG values usually as distance from the datum line so we need to make NACA CoG location comparable with these. And that is easy because we know that the datum line is 18.65" behind leading edge at the MAC:

26.4476" - 18.65" = 7.7976"

And this value, 7.8" aft datum line, is comparable with the other sources like A&AEE and RAE tests and loading instructions.

Over and out.

Robo.

07-17-2012, 05:34 AM

Tommorrow I think we can discuss game behaviors to ask for in the bugtracker.

I wonder how exactly would you like to model jaming pilots elbow against his body. :o

My opinion is (flying all available fighter airplane in the game) that it's the Hurricane and Bf 109 elevator is too light even at higher speeds rather than Spitfire elevator being not light enough. Generally I like how game calculates forces on the stick and how they increase with the increasing airspeed, it just needs some fine tuning and obviously structural G limits modelled.

I believe there already is a bugtracker issue raised regarding structural G limits somewhere, will confirm.

The only problem I see at the moment (1.07) is that they have changed something on the Spitfire FM and it is nearly impossible to get the plane into a high speed stall. Before that, iirc, it was a plane matching the description much better - you had to be careful not to bring it too close to the stall, you had to be more careful with the the elevator than now in 1.07. Have you noticed the same thing Crumpp?

Robo.

07-17-2012, 05:57 AM

Looking at the bugtracker, I can't seem to find the 'structural G limits' issue, but I am sure it has been discussed. This would be a most welcome feature, but very difficult to model reasonably - the virtual pilot is not getting the kind of feedback like the real pilot did. This is already a problem in old Il-2, but the new features enhanced the gameplay in a great way already.

Reading through the other bugtracker issue (re: Merlin incorrect power settings)

http://www.il2bugtracker.com/issues/370#change-1216

I found Crumpp posted following comment:

He has the engine settings wrong for the Merlin III at 100 Octane.

The correct settings by the Operating Notes are:

+12lbs 2850 rpm *below* 20,000 feet
+12lbs 3000 rpm above 20,000 feet

There is not much to discuss. I just was not clear in my post.

interpreting the hard data in most extraordinary way. I believe you've made a mistake in there and I suggest you're more careful with your bugtracker activities, because devs seem to actually read that from time to time and your views are often wrong and misleading. Thank you.

NZtyphoon

07-17-2012, 09:35 AM

Just some of the many references to the Longitudinal instability found in all of the early Mark Spitfires.

Spitfire Mk I Operatings Notes, July 1940:

http://img109.imageshack.us/img109/7976/page10jv.jpg (http://imageshack.us/photo/my-images/109/page10jv.jpg/)

http://img26.imageshack.us/img26/2599/page12dh.jpg (http://imageshack.us/photo/my-images/26/page12dh.jpg/)

http://img542.imageshack.us/img542/9202/page13o.jpg (http://imageshack.us/photo/my-images/542/page13o.jpg/)

http://img607.imageshack.us/img607/2471/page15j.jpg (http://imageshack.us/photo/my-images/607/page15j.jpg/)

http://img651.imageshack.us/img651/2456/page16lu.jpg (http://imageshack.us/photo/my-images/651/page16lu.jpg/)

Here are some good examples of pages designed to be used by trainee pilots and which are conservative in their assessments: for example the "violent pre-stall buffet" is a feature commented upon favourably by most Spitfire pilots who cite this feature as being a good warning device announcing that a stall was imminent, and it is something which was deliberately designed into the Spitfire by Mitchell.

How many aircraft need to be treated with care in bumpy conditions and high-g? All aircraft, except those that are particularly stable, need care when experiencing bumpy conditions under high-g loading, so there's nothing different about having such a warning in a Pilot's Notes. The "Pilot's Notes General" are specific about flying in bumpy conditions:

6. Flying in Bumpy Air.
(i) "Bumpy" air imposes g on the airframe and the effect of either horizontal or vertical variations of the wind on the airframe is proportional to the speed at which it is flying.
(ii) Speed should be restricted when flying in or near heavy cloud formations (especially cumulo-nimbus)...
(iii) As the effect of bumps may be added to g imposed by manœuvres, g due to manœvres should be kept to lower limits in rough weather.

In a high speed fighter pilots need to be careful in bumpy air - so what? Jeffrey Quill's comments about the elevators are interesting (to be posted later).

robtek

07-17-2012, 02:49 PM

TomcatViP

07-17-2012, 04:27 PM

To get an actual idea, it's juts like having the joystick on a slippy surface. Each time you pull or push the stick, the base move. Obviously there the phenomena is reversed but roughly it's the same.

NZtyphoon

07-18-2012, 01:42 AM

NZTyphoon,
bumpy conditions, where a pilot is moved around in the cockpit despite harness, are not so difficult to master if the pilot has to use some force to move the elevator.
The problem arises when minimal stick forces AND minimal stick movements are resulting in major changes.

The notes specifically talk about the pilot jerking the stick while manoeuvring with high-g in bumpy conditions - that does not sound like minimal stick movement or forces.

Crumpp is putting a worst-case scenario on the "buffeting", a feature which many pilots have praised as a pre-stall warning, and on comments about the pilot accidentally jerking at the stick in adverse conditions; in other threads he has gone as far as to claim that early Spitfires were longitudinally unstable and dangerous to fly - as I have said before, he needs to back up such claims with solid evidence, in the same way he demanded that others provide 100% evidence for 100 Octane use. Why should we expect anything else?

robtek

07-18-2012, 11:38 AM

winny

07-18-2012, 11:50 AM

The necessary Stick movement (elevator) to induce a 3 g load at cruise speed was three quarters of an inch in the Spitfire, afaik, very easy to get unintended reactions there if your arm isn't completely fixated.

To be fair, there are loads of references by pilot's to having to either wedge their elbows into the side walls or into their own stomachs to steady themselves.
Quite a few mention going 2 handed. They adapted.

As in most cases in WW2, the pilot's coped with the quirks of their machines and got the best out of them ( the good ones at least ).

robtek

07-18-2012, 01:34 PM

To be fair, there are loads of references by pilot's to having to either wedge their elbows into the side walls or into their own stomachs to steady themselves.
Quite a few mention going 2 handed. They adapted.

As in most cases in WW2, the pilot's coped with the quirks of their machines and got the best out of them ( the good ones at least ).

Exactly, one of the quirks of the Spit was the extreme easy elevator, great for experts, more difficult for beginners; The difference to planes with "normal" handling should be in the game.
Same for the very heavy elevator at very high speeds (>600 km/h) in the 109, i.e.

NZtyphoon

07-18-2012, 02:50 PM

Amoung the Western Front warring powers during World War II, only two nations had measurable and definable stability and control standards. Stability and control was a young science. Airplanes had simply been two slow and light previously. The forces were small enough such that there was little need. The two nation were the United States and Germany.

Slightly OT, but important to this thread; Unfortunately Crumpp's "historical analysis" is seriously flawed - the British, with the likes of William Lanchester, were pioneers in laying down scientific principles for aeronautics, as shown by this extract: http://rsnr.royalsocietypublishing.org/content/61/1/39.full

The eponymous university of a vibrant industrial city was an appropriate institution for studies in higher engineering; his father counselled Ludwig to go to Manchester. At the time, English aeronautics was transforming itself from a fledgling, essentially empirical, science to one grounded on firmer principles, taking forward the perceptive concepts of powered aeroplane flight set down by Sir George Cayley a century earlier. Frederick William Lanchester (FRS 1922), who disapproved of trial and error methods, had produced his theoretical calculations for the lift acting on an aircraft wing. His book Aerodynamics was the standard text to be consulted on the subject.

The university had not long been formed from the incorporation of two higher education establishments, Owen's College and Victoria University. It inherited a brilliant academic staff. The Professor of Mathematics was Horace (later Sir Horace) Lamb FRS.7 His classic work Hydrodynamics underpinned the solution of numerous problems arising from the dynamics of an aircraft in flight. A lecturer under Lamb was J. E. Littlewood (FRS 1916), who after spending an unhappy three years at Manchester (1907–10) returned to Cambridge.8 Wittgenstein attended Littlewood's lectures and eventually met up with him again at Cambridge on equal professorial terms.

Another notable at Manchester had been Osborne Reynolds FRS, a longstanding Professor of Engineering who retired a few years before Wittgenstein's arrival but whose work on kinematic viscosity resulted in the Reynolds number, a parameter of vital importance with regard to the onset of turbulent flow within the boundary layer on the surface of an aerofoil. Reynolds's successor, Ernest Petavel FRS, a distinguished physicist, actually learned to fly; in consequence he underwent a severe flying accident.9 In due course he took up the post of Director of the National Physical Laboratory (NPL), an organization also becoming involved with aviation activities, for instance constructing wind tunnels to test models.5 In 1908 the contributions of these Manchester academics to aeronautics were yet to be fully realized.

I would have though that someone who is supposed to be a graduate of aeronautical engineering would have known of William Lanchester:http://www.guggenheimmedal.org/Pages/Medalists.aspx?Year=1931

Aeronautical science to Lanchester was always a spare-time recreation. One of his earliest contributions was an analysis of the dynamical stability of airplane flight, made in 1897, some years before there were any airplanes. So penetrating was the insight shown that this analysis served as the inspiration and foundation for the later work of Bryan, Bairstow, Hunsaker and many others, who were able to apply Lanchester’s precepts while using modern wind tunnels.

He was also the first to propound the vortex theory of flight and its engineering application to the design of airplanes, which was followed up later by Prandtl and others. The vortex theory was the basis of a paper read by Lanchester before the Birmingham National History and Philosophical Society in 1894, and a further paper submitted to the Physical Society of London in 1897.

Lanchester was one of the original members of the Aeronautical Research Com*mittee under the chairmanship of Lord Rayleigh. In 1926 he gave the Wilbur Wright Memorial Lecture on the subject: “Sustentation in Flight.” He died March 8, 1946, at the age of 77.

and also recognised the role of the likes of the Royal Aircraft factory (later Royal Aircraft Establishment) in laying down the principles of scientific analysis later used by NACA; instead we have these types of comments:

The RAE did not have stability and control standards. However, the RAE did agree with the NACA even if they did not know it.

which are complete nonsense. This type of blinkered ignorance about the role of the British, and the Royal Aircraft Factory and RAE, in laying down the principles of scientific aeronautical analysis beggers belief, and Crumpp's idea that only the USA and Germany "had measurable and definable stability and control standards" during WW2 is farcical.

Crumpp

07-18-2012, 03:05 PM

Great document Lane!!

It gives us a measurement of the divergence and the slope of the Cm increase.

Exactly, one of the quirks of the Spit was the extreme easy elevator

Not only that, it is unstable. That means your coefficient of moment increases each cycle instead of decreasing.

So if you pull a 6 G turn and did nothing except hold the stick fixed, the next oscillation will exceed 6G and continue to increase with each cycle until the airframe is destroyed.

That is the reason why "flick" maneuvers were not allowed in it.

Let's summarize the behavior that occur at normal and aft CG positions and categorize them to be implemented in the game. Then we can build a list for the bug tracker. These are all at NORMAL CG. If the game models a shifting CG then they increase in severity at aft CG positions.

The take away is:

1. The large accelerations change for very little elevator movement.
2. The very rapid rate at which the pilot was able to load the airframe to 5G's.
3. The equally rapid rate at which the airframe unloaded down to 2G's when the pre-stall buffet was encountered. In 1 second, the aircraft went from 5G's to 2G's due to buffet losses. This means a rapid decay in turn rate resulted.
4. The violence of the pre-stall buffet combined with the longitudinal stability and control caused large fluctuations in the accelerations on the aircraft.
5. The violent accelerated stall behavior resulting in spin/loss of height

1. The large accelerations change for very little elevator movement.

1. The Spitfire should be twitchy and unstable gun platform. IIRC, in IL2, people used to complain about the "twitchy" behavior or the Corsair and P-51's so I am sure it is within the games engine to model a twitchy airplane.

It should take very careful and small stick movements to get the gun sight on target. That means a Spitfire pilot will require more skill to hit a maneuvering target than he would need in a stable platform such as the Hurricane.

2. Above Va, large or abrupt elevator control can more easily exceed the airframe limitations of 6G for damage. Currently, it is impossible to stall the Spitfire in a turn or a dive. The reality is it requires careful flying so as NOT to induce an accelerated stall or exceed the airframe limitations.

3. In the turn, the violent buffet is a double edged sword. There is no such thing as a free lunch especially in physics. In the NACA measured results, encountering the buffet represents a change in available angle of bank. The airplane goes from 78.5 degrees of bank to 60 degrees of bank in one second.

****5G @ 147.73KIAS:

ROT = 1091*tan(78.5) divided by 147.73 KIAS = 36.2 degrees a second

****2G @ 141.647 KIAS:

ROT = 1091*tan(60) divided by 141.647 = 13.34 degrees a second

As a quick ballpark using IAS to get an idea of the scope of the effect on turn performance, we see the rate of turn drop from 36.2 degrees a second to 13.34 degrees a second. That means our time to complete a 360 degree turn changes from 10 seconds to 27 seconds!!!

As the Operating Notes relate, you do not want to turn any airplane in the buffet. Energy cannot be created or destroyed, all the energy that was being used to achieve an instantaneous performance rate of turn of 36.2 degrees a second from our ballpark went to warn the pilot of an impending stall, taking the aircraft right down well inside its sustainable performance envelope of 13.34 degrees a second.

The longitudinal stability characteristics of the Spitfire requires skilled flying to achieve a maximum performance turn. In a stable airplane, the pilot would have a much easier time keeping the aircraft at the maximum rate of turn velocity and a less violent buffet would have subsequently reduced effects on the turn performance.

4. Below Va, the Longitudinal instability of the Spitfire make it more difficult for the average pilot to prevent an acelerated stall or overcontrol the aircraft by pulling deeper into the buffet zone.

I think the fact that you have to return the stick almost to neutral after entering a high g turn (>3 g) to prevent oversteering in a Spitfire should be in game, also the very sensible elevator with large reaction for small inputs and the roll rate as documented.
This will be a problem for ham-handed pilots, but a delight for the virtuosos, as it was in RL.
I don't see that as "porking" the Spit further, but to give it the characteristics that made it famous.
Every aircraft in CoD should reflect its pro's and con's as they where documented then.

Exactly. That is our goal to recreate the flying qualities of all of these aircraft.

In this thread we have focused primarily on the Longitudinal stability. Most of the Spitfires issues stem from that.

For example, the heavy lateral control forces would not be an issue if the control forces were equal on all axes. The control harmony was poor in the Spitfire and Gimpy raises a good point:

well personally I would expect a much lower Roll rate at speed, and a very sensitive Unbalanced Elevator (unbalanced meaning it needs much more roll input than pitch).
The pilots ability to apply lateral control would be reduced by the longitudinal control characteristics.

*****Not a silly argument on actual turn performance, just a quick ballpark so readers understand the importance and general effect of encountering the buffet on turn performance.

Crumpp

07-18-2012, 03:22 PM

the British, with the likes of William Lanchester, were pioneers in laying down scientific principles for aeronautics,

:rolleyes:

You are confused about this whole subject. Of course, there were some brilliant British engineers.

What does he have to with an adopted measureable standard for stability and control????

You understand, an engineer in the United States or German designing a fighter could go look to see the measured characteristics that he must meet.

Gates was the British engineer who tried to shoulder that task of getting the Air Ministry to adopt a measureable standard. He eventually achieved it in the post war.

taildraggernut

07-18-2012, 03:37 PM

So why was the Mustang III considered longitudinaly unstable too?

winny

07-18-2012, 05:28 PM

So, now all we need is the same data for a MK I and II.
Because, correct me if I'm wrong, they didn't test them at NACA.

I'm pretty sure that if I came on here saying that the 109 E was wrong, and used an F or G's data I'd get laughed out of here. Especially by you.

So I'd like some hard data on the same phenomenon in I's and II's, please.

Thanks.

Edit: and bear in mind that the spitfire in lanes docs is around 300lb lighter than a spit in BoB trim.

JtD

07-18-2012, 05:38 PM

It was designed for a load factor of 10, not 6. Calculation showed wing to be the weakest point, it was tested and met specification. Specification was changed to 12 for later marks.

CaptainDoggles

07-18-2012, 05:54 PM

Slightly OT, but important to this thread; Unfortunately Crumpp's "historical analysis" is seriously flawed - the British, with the likes of William Lanchester, were pioneers in laying down scientific principles for aeronautics, as shown by this extract: http://rsnr.royalsocietypublishing.org/content/61/1/39.full

...

I would have though that someone who is supposed to be a graduate of aeronautical engineering would have known of William Lanchester:http://www.guggenheimmedal.org/Pages/Medalists.aspx?Year=1931This is being disingenuous; your argument is flawed. The fact that someone didn't mention Lanchester when discussing a subject that was mostly unrelated to him doesn't mean that that person has never heard of Lanchester.

robtek

07-18-2012, 08:06 PM

taildraggernut

07-18-2012, 08:15 PM

The airframe of the Mk Va is similar to the Mk I and II

is similar a good enough benchmark? even the Mk9 airframe was similar.

I think Winny's point is valid, would it be accepted if the aircraft being analysed was a 109?

taildraggernut

07-18-2012, 09:30 PM

That is the reason why "flick" maneuvers were not allowed in it.

Flick manouvres were permitted in the Mk2 (from pilots' notes) at slow speeds, there are several other aircraft including the P-40 which were prohibited from 'flick' rolls and intentional spinning.

Al Schlageter

07-18-2012, 09:47 PM

The Fw190 had a nasty tendency to do a crazy maneuver when in a banked turn that was very dangerous to the pilot, especially the low time pilot and Germany had many, many of these. It didn't matter if the turn was to port or starboard, the a/c always ended up going to starboard.

No doubt we will hear that this was caused by incorrectly adjusted ailerons.

NZtyphoon

07-18-2012, 10:05 PM

:rolleyes:

You are confused about this whole subject. Of course, there were some brilliant British engineers.

What does he have to with an adopted measureable standard for stability and control????

You understand, an engineer in the United States or German designing a fighter could go look to see the measured characteristics that he must meet.

Gates was the British engineer who tried to shoulder that task of getting the Air Ministry to adopt a measureable standard. He eventually achieved it in the post war.

Wrong again, Lanchester's work on aerodynamics, as well as other British academics, provided a basis for the adopted measurable standards for stability & control worldwide - the British did indeed have such standards, and adopted them well before NACA; to claim that only the Americans and Germans had such standards is farcical. Read the articles and do some historical research of your own before making such claims. What work, for example, did the National Physical Laboratory in Britain do during WW1? http://www.npl.co.uk/about/history/ The Duplex wind tunnel was completed in 1919. It had a cross-section of 2 m by 4 m.

During the first world war, activity in aerodynamics expanded dramatically and NPL made major contributions to advances in theoretical and practical aspects of the stability of aeroplanes, airships, kite balloons and parachutes. Techniques had been developed for testing scale models of wings, ailerons, propellers and of complete models of aeroplanes in wind tunnels.

CaptainDoggles

07-18-2012, 10:30 PM

is similar a good enough benchmark? even the Mk9 airframe was similar.

I think Winny's point is valid, would it be accepted if the aircraft being analysed was a 109?

IMO, the difference between a MkII and a MkV is much less than the difference between a 109F and a 109G.

My understanding is that a MkV is basically just a MkI but with a Merlin 45. True?

By contrast, the 109F is drastically different, structurally speaking, from the 109E. Different wings, different tail empennage, lack of wing guns, different engine cowling, etc.

If we were talking about, say, Fw 190A variants it might be a different story.

taildraggernut

07-18-2012, 10:57 PM

My understanding is that a MkV is basically just a MkI but with a Merlin 45. True?

in very basic terms yes, but there were relatively significant differences, the bob weight, but even an engine change makes it a different beast, it performs differently it is loaded differently, the pilot's notes between the 2 reflect that, so I don't think it's a fair comparison at all.

winny

07-18-2012, 11:34 PM

IMO, the difference between a MkII and a MkV is much less than the difference between a 109F and a 109G.

My understanding is that a MkV is basically just a MkI but with a Merlin 45. True?
.

It's essentially a MK I airframe, yes. There are differences though.
The airframes were strengthened (I must admit I don't know what this involved)
The radiator scoop under the wing is bigger, and there was a difference in weight .
MK V's had the inertia weight fitted into the elevator system as well. There's also a difference between early V's and late V's, they got heavier as more mods were added.

It's all a bit confusing, I've got Crumpp saying that the stall is horrid and yet I've got a NACA report on the Spitfire stall that says that it has the best stall characteristics of any fighter they had tested and that they were 'desirable'

The other problem I have with this whole argument is that there is no data for the same tests on any of the other a/c in the game (AFAIK). How many WW2 aircraft would have also been considered unstable by NACA?

Al Schlageter

07-18-2012, 11:59 PM

winny it is all about making an Olympus Mons out of a mole hill.

CaptainDoggles

07-19-2012, 12:18 AM

Olympus Mons

:lol:

Crumpp

07-19-2012, 01:03 AM

It's all a bit confusing, I've got Crumpp saying that the stall is horrid

Read the NACA report.

Stall warning is NOT buffet effect on turn performance.

Accelerated stall is NOT a 1G wings level stall.

Crumpp

07-19-2012, 01:14 AM

Crumpp

07-19-2012, 01:41 AM

provided a basis for the adopted measurable standards for stability & control worldwide

Great!! A basis is not an adopted standard, Capeesh??

There were several British pioneers of stability and control. In fact, Gates is the one who came up with Aerodynamic Center and Stability Margin.

It made Center of Pressure theory obsolete and was integral part of Gilruths work. Like I said earlier, Gilruth and Gates were good friends.

That does nothing to change the fact the Air Ministry had no measurable standard in place until after the war.

Your link is a meaningless and has no bearing on stability and control standards.

Crumpp

07-19-2012, 02:49 AM

So, now all we need is the same data for a MK I and II.

See my post above with the Mk I Operating Notes.

We also have Cm's on the Spitfire Mk I.

NZtyphoon

07-19-2012, 02:53 AM

Great!!

There were several British pioneers of stability and control. In fact, Gates is the one who came up with Aerodynamic Center and Stability Margin.

It made Center of Pressure theory obsolete and was integral part of Gilruths work. Like I said earlier, Gilruth and Gates were good friends.

That does nothing to change the fact the Air Ministry had no measurable standard in place until after the war.

Your link is a meaningless and has no bearing on stability and control standards.

The only part you are right about is that there were several British pioneers of stability and control - the National Physical Laboratory had made major contributions to advances in theoretical and practical aspects of the stability of aeroplanes, airships, kite balloons and parachutes. long before NACA, - to claim that the "Air Ministry had no measurable standard in place" until after WW2 shows an abysmal ignorance of the history of aeronautical science in Britain - something which a supposed graduate in aeronautical engineering should know and understand.

Do some basic research Crumpp, before making claims you cannot substantiate.

Crumpp

07-19-2012, 03:24 AM

made major contributions

Is not an adopted standard....

:rolleyes:

winny

07-19-2012, 07:29 AM

See my post above with the Mk I Operating Notes.

We also have Cm's on the Spitfire Mk I.

That Mk I is way too early. Doesn't have the pilot's armour, bullet proof windscreen, etc.. It's at least 300 lb lighter than a Spitfire in BoB trim (around 6,100 lb auw). Check the serial number.

winny

07-19-2012, 08:21 AM

Spitfire Mk I Operating Notes, July 1940.

What do you think the "violent shudder" is.....hint....PRE-STALL BUFFET.

http://img607.imageshack.us/img607/2471/page15j.th.jpg (http://imageshack.us/photo/my-images/607/page15j.jpg/)

Ok.. NACA report on stalling characteristics of the same MK V
http://i822.photobucket.com/albums/zz147/winistrone/aebc089d.jpg

http://i822.photobucket.com/albums/zz147/winistrone/ff51dc44.jpg

Further on in the report

http://i822.photobucket.com/albums/zz147/winistrone/59551859.jpg

http://i822.photobucket.com/albums/zz147/winistrone/6f5ead08.jpg

taildraggernut

07-19-2012, 08:40 AM

Is not an adopted standard....

:rolleyes:

Why exactly is this relevant in any case? the US managed to put aircraft into production with almost exactly the same 'apparent' problems as the Spitfire, the Mustang III was actually longitudinally 'unstable' while the Spit was neutrally stable, most of the pilot's notes I have read on several WWII aircraft do not permit intentional spinning and do not permit 'flick' manouvers, the free lessons in aerodynamics make for interesting reading to the Layman I'm sure but I'm wondering what the actual point is, the Spitfire never had a bad reputation for stability.

taildraggernut

07-19-2012, 09:31 AM

Spitfire Mk I Operating Notes, July 1940.

What do you think the "violent shudder" is.....hint....PRE-STALL BUFFET.

Precisely....and with an aircraft that is easy to control because it is light in pitch it is much easier for the pilot to control it to the edge of buffet, a Spit pilot only needs to use two fingers to unload the wings at the buffet, easy peasy.

NZtyphoon

07-19-2012, 10:41 AM

Is not an adopted standard....

:rolleyes:

Wrong, again - the British adopted standards that had been set by the likes of Lanchester, the NPL and Royal Aircraft Factory- the assertion that neither the RAE or Air Ministry had set standards is completely false. See, for example http://aerade.cranfield.ac.uk/reports.html

and
http://i91.photobucket.com/albums/k304/Major_Sharpe/2609-page-002a.jpg

Why exactly is this relevant in any case?

Crumpp claimed right at the start of this thread that only the Americans and Germans had adopted standards for stability and control and that the RAE and British Air Ministry had not adopted such standards until after WW2 - such claims show an abysmal ignorance, bias and a lack of objectivity from someone who claims to have in-depth knowledge of aeronautical engineering.

taildraggernut

07-19-2012, 10:53 AM

Crumpp claimed right at the start of this thread that only the Americans and Germans had adopted standards for stability and control and that the RAE and British Air Ministry had not adopted such standards until after WW2 - such claims show an abysmal ignorance, bias and a lack of objectivity from someone who claims to have in-depth knowledge of aeronautical engineering.

Yes, this is what I find most confusing, it seems the Spitfire is getting a character assasination based on some entries in pilots notes and flight tests, yet I can find many of the same restrictions in many other pilots notes on other aircraft....American ones no less, so with all these 'adopted' stability and control standards the Americans were producing aircraft with the same apparent problems? the Germans also produced aircraft with what might be considered 'dangerous' characteristis....so why is the Spitfire getting all this attention?

Robo.

07-19-2012, 11:26 AM

so why is the Spitfire getting all this attention?

Because Crumpp :grin:

Crumpp

07-19-2012, 11:49 AM

Crumpp claimed right at the start of this thread that only the Americans and Germans had adopted standards for stability and control

:rolleyes:

You don't seem to grasp the difference between research and adopted standard.

This is an adopted Standard:

http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?type=simple;c=ecfr;cc=ecfr;sid=dee22aca65b1304 2f95550f409867af5;idno=14;region=DIV1;q1=25;rgn=di v5;view=text;node=14%3A1.0.1.3.11#14:1.0.1.3.11.2. 158.27

You keep making these claims without proof.

Go search the forum. I have posted the document.

You can buy the book yourself too and read it.

It is pretty interesting.

seems the Spitfire is getting a character assasination

:rolleyes:

Read the thread. Spitfire is just the first one.

The history is interesting but a sideline. Start another thread if you want to discuss it.

The Spitfires Longitudinal stability characteristics are well defined and measured. The NACA and Air Ministry were very much aware of it.

Why exactly is this relevant in any case?

It is not to this thread about the Spitfire. So please start another thread if you want to discuss it.

taildraggernut

07-19-2012, 12:18 PM

:rolleyes:

Read the thread. Spitfire is just the first one.

The history is interesting but a sideline. Start another thread if you want to discuss it.

The Spitfires Longitudinal stability characteristics are well defined and measured. The NACA and Air Ministry were very much aware of it.

First of all there is no need for the little blue sarcastic face, secondly....start a new thread to discuss what?
the Spitfires Longitudinal stability characteristics were actually quite unremarkeable and yes that 'is' very well documented, can you explain why the P-40 was not allowed to spin or flick roll? these seem to be important facts you use to back up claims about Spitfire stability issues.

It is not to this thread about the Spitfire. So please start another thread if you want to discuss it

Sorry? i ask if something you posted is relevant and you say it's not, but as it's in this thread and I felt the need to enquire then why do I need to start another thread?

Please quit with the sarcastic tone.

taildraggernut

07-19-2012, 12:32 PM

You don't seem to grasp the difference between research and adopted standard.

This is an adopted Standard:

http://ecfr.gpoaccess.gov/cgi/t/text....3.11.2.158.27

But this is a 'post war' adopted standard, have you got a link to the evidence of adoption of standards during the war? and clear evidence the British did not have any?

p.s. not sure why you PM'd me the answer, but it is probably the most relevant post made, would you mind if I put your PM up on here?

Crumpp

07-19-2012, 01:13 PM

have you got a link to the evidence of adoption of standards during the war?

Start another thread.

I PM'd you the answer because it has NO BEARING on the Early Mark Spitfires.

The purpose of this thread is to define the early Mark Spitfire characteristics so they can be included in the game. Those characteristics are measured, defined, and agreed upon by all parties involved in the Spitfires design.

It is not to debate the history of stabilty and control engineering.

taildraggernut

07-19-2012, 01:33 PM

Start another thread.

Sorry but that doesn't really cut it, there is nothing 'off topic' in my asking for your sources for claims you make on this thread, it's an open forum and that all sounds a bit evasive if you ask me, not to mention the rude tone you keep coming back with once someone asks a question.

I PM'd you the answer because it has NO BEARING on the Early Mark Spitfires.

The link to the modern day adopted standards has no bearing on the Spitfire either but it seems no problem to include it here....the adopted standard here seems a double one.

The purpose of this thread is to define the early Mark Spitfire characteristics so they can be included in the game. Those characteristics are measured, defined, and agreed upon by all parties involved in the Spitfires design.

That may be what you'd like it to be, in a one man show unhindered way, but it seems you have attracted a difference of oppinion, for the most part the enquiries into your sources have been valid and polite and deserve to be answered, it just seems the threat needs to titled 'according to Crumpp'

It is not to debate the history of stabilty and control engineering.

You did after all claim that the british had no adopted standards and have put NACA on a pedestal as an example of an establishment which had adopted standards.....this does not conform to what you put in the PM, I just think it's a little unfair to expect to have a thread dedicated to your 'sole' oppinions.

NZtyphoon

07-19-2012, 01:36 PM

:rolleyes:

You don't seem to grasp the difference between research and adopted standard.

This is an adopted Standard:

http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?type=simple;c=ecfr;cc=ecfr;sid=dee22aca65b1304 2f95550f409867af5;idno=14;region=DIV1;q1=25;rgn=di v5;view=text;node=14%3A1.0.1.3.11#14:1.0.1.3.11.2. 158.27

:rolleyes::rolleyes:
So what? You have absolutely no evidence for this ridiculous claim that the British had no adopted standards, although I have searched through all of your posts to find a "document" you claim to have posted - without success...

Go search the forum. I have posted the document.

this is exactly like Crumpp's assertions over 100 octane and 16 fighter squadrons - all this does is show his level of ignorance and biased POV about the British aviation industry and administration, and about the Spitfire.

It is not to debate the history of stabilty and control engineering.

Crumpp's introductory comments to this thread:

Amoung the Western Front warring powers during World War II, only two nations had measurable and definable stability and control standards. Stability and control was a young science. Airplanes had simply been two slow and light previously. The forces were small enough such that there was little need. The two nation were the United States and Germany.

Let's not be obtuse. None of this is to claim other nations did not progress in aviation or contribute. It is only to lay the historical foundation as to why these were the only Western Nations to adopt stability and control standards.

Yeah, right - the poor ol' British had no proper stability and control standards and no clues, until the heroic Americans helped sort it out for
them...:grin::grin::grin:

Crumpp

07-19-2012, 01:42 PM

P-40 was not allowed to spin or flick roll?

Sure, you can look at the design and its characteristics to easily see the behaviors that prohibited spins and flick rolls.

It is not that hard.

As for the Spitfire's longitudinal stability, there is nothing to dispute or argue about at this point. The only discussion that is really open is what can be modeled in the game.

People might not understand some things but the RAE Cm graphs, NACA measurements, RAE oscillation graphs, Operating Notes, and pilot reports are all in agreement.

Just as all the pointy tin foil hat CG position theory from people who do not understand MAC calculations, we are now just arguing because folks don't understand the results of the RAE Cm graphs, NACA measurements, RAE oscillation graphs, Operating Notes, and pilot reports.

Crumpp

07-19-2012, 01:45 PM

I will be happy to take to PM and explain the results for the few who have questions.

Feel free to send me one.

Crumpp

07-19-2012, 01:48 PM

That may be what you'd like it to be, in a one man show unhindered way, but it seems you have attracted a difference of oppinion, for the most part the enquiries into your sources have been valid and polite and deserve to be answered, it just seems the threat needs to titled 'according to Crumpp'

DEFINE what you do not understand.

Posting "It flew great and was easy" is not an argument nor definable. It is opinion.

taildraggernut

07-19-2012, 01:54 PM

Sure, you can look at the design and its characteristics to easily see the behaviors that prohibited spins and flick rolls.

It is not that hard.

Actually the reason is even simpler, intentional spins were simply 'discouraged', there simply is no physical reason why the aircraft (any of them) could not be spun.

As for the Spitfire's longitudinal stability, there is nothing to dispute or argue about at this point. The only discussion that is really open is what can be modeled in the game.

Well I would tend to agree on the basis that there is 'nothing' particularily remarkeable about the Spitfires stability, so yes I see no need to continue a thread like this one, it seems to be going nowhere....appart from trying to paint an innacurate picture of the Spitfire, what should be modelled in the game is a Spitfire with light elevator controls that gives plenty of pre stall warning simple as that, the Spitfire did nothing out of the ordinary in a high speed stall, you only have to look at other aircrafts pilots notes to see that.

Just as all the pointy tin foil hat CG position theory from people who do not understand MAC calculations, we are now just arguing because folks don't understand the results of the RAE Cm graphs, NACA measurements, RAE oscillation graphs, Operating Notes, and pilot reports.

Bold claims, are you sure nobody else but you understands them?

taildraggernut

07-19-2012, 01:55 PM

I will be happy to take to PM and explain the results for the few who have questions.

Feel free to send me one.

Why all the 'cloak and dagger' secrecy of PM's, this is a forum, why can't people ask you a question and you answer them?

taildraggernut

07-19-2012, 01:58 PM

DEFINE what you do not understand.

Posting "It flew great and was easy" is not an argument nor definable. It is opinion.

I don't understand what you are trying to prove with this thread, I don't need to PM you to get that accross.

it seems to me that if we wen't down the road of how you would like the Spitfire 'defined' then it wouldnt fly so great and be easy.......which seems at odds with real world oppinion.

Crumpp

07-19-2012, 02:01 PM

odds with real world oppinion

:confused:

Just because these people put a ruler to it and measured against a definable standard, it is invalid because folks flew the plane around the pattern???

RAE Cm graphs, NACA measurements, RAE oscillation graphs, Operating Notes, and pilot reports

taildraggernut

07-19-2012, 02:02 PM

folks flew the plane around the pattern???

Pattern?.....are you equating air to air combat during WWII to flying a cirquit pattern?

Crumpp

07-19-2012, 02:07 PM

Let's get back on topic:

This thread defines the characteristic that can submitted for the bugtracker.

Great document Lane!!

It gives us a measurement of the divergence and the slope of the Cm increase.

Exactly, one of the quirks of the Spit was the extreme easy elevator

Not only that, it is unstable. That means your coefficient of moment increases each cycle instead of decreasing.

So if you pull a 6 G turn and did nothing except hold the stick fixed, the next oscillation will exceed 6G and continue to increase with each cycle until the airframe is destroyed.

That is the reason why "flick" maneuvers were not allowed in it.

Let's summarize the behavior that occur at normal and aft CG positions and categorize them to be implemented in the game. Then we can build a list for the bug tracker. These are all at NORMAL CG. If the game models a shifting CG then they increase in severity at aft CG positions.

The take away is:

1. The large accelerations change for very little elevator movement.
2. The very rapid rate at which the pilot was able to load the airframe to 5G's.
3. The equally rapid rate at which the airframe unloaded down to 2G's when the pre-stall buffet was encountered. In 1 second, the aircraft went from 5G's to 2G's due to buffet losses. This means a rapid decay in turn rate resulted.
4. The violence of the pre-stall buffet combined with the longitudinal stability and control caused large fluctuations in the accelerations on the aircraft.
5. The violent accelerated stall behavior resulting in spin/loss of height

1. The large accelerations change for very little elevator movement.

1. The Spitfire should be twitchy and unstable gun platform. IIRC, in IL2, people used to complain about the "twitchy" behavior or the Corsair and P-51's so I am sure it is within the games engine to model a twitchy airplane.

It should take very careful and small stick movements to get the gun sight on target. That means a Spitfire pilot will require more skill to hit a maneuvering target than he would need in a stable platform such as the Hurricane.

2. Above Va, large or abrupt elevator control can more easily exceed the airframe limitations of 6G for damage. Currently, it is impossible to stall the Spitfire in a turn or a dive. The reality is it requires careful flying so as NOT to induce an accelerated stall or exceed the airframe limitations.

3. In the turn, the violent buffet is a double edged sword. There is no such thing as a free lunch especially in physics. In the NACA measured results, encountering the buffet represents a change in available angle of bank. The airplane goes from 78.5 degrees of bank to 60 degrees of bank in one second.

****5G @ 147.73KIAS:

ROT = 1091*tan(78.5) divided by 147.73 KIAS = 36.2 degrees a second

****2G @ 141.647 KIAS:

ROT = 1091*tan(60) divided by 141.647 = 13.34 degrees a second

As a quick ballpark using IAS to get an idea of the scope of the effect on turn performance, we see the rate of turn drop from 36.2 degrees a second to 13.34 degrees a second. That means our time to complete a 360 degree turn changes from 10 seconds to 27 seconds!!!

As the Operating Notes relate, you do not want to turn any airplane in the buffet. Energy cannot be created or destroyed, all the energy that was being used to achieve an instantaneous performance rate of turn of 36.2 degrees a second from our ballpark went to warn the pilot of an impending stall, taking the aircraft right down well inside its sustainable performance envelope of 13.34 degrees a second.

The longitudinal stability characteristics of the Spitfire requires skilled flying to achieve a maximum performance turn. In a stable airplane, the pilot would have a much easier time keeping the aircraft at the maximum rate of turn velocity and a less violent buffet would have subsequently reduced effects on the turn performance.

4. Below Va, the Longitudinal instability of the Spitfire make it more difficult for the average pilot to prevent an acelerated stall or overcontrol the aircraft by pulling deeper into the buffet zone.

I think the fact that you have to return the stick almost to neutral after entering a high g turn (>3 g) to prevent oversteering in a Spitfire should be in game, also the very sensible elevator with large reaction for small inputs and the roll rate as documented.
This will be a problem for ham-handed pilots, but a delight for the virtuosos, as it was in RL.
I don't see that as "porking" the Spit further, but to give it the characteristics that made it famous.
Every aircraft in CoD should reflect its pro's and con's as they where documented then.

Exactly. That is our goal to recreate the flying qualities of all of these aircraft.

In this thread we have focused primarily on the Longitudinal stability. Most of the Spitfires issues stem from that.

For example, the heavy lateral control forces would not be an issue if the control forces were equal on all axes. The control harmony was poor in the Spitfire and Gimpy raises a good point:

well personally I would expect a much lower Roll rate at speed, and a very sensitive Unbalanced Elevator (unbalanced meaning it needs much more roll input than pitch).
The pilots ability to apply lateral control would be reduced by the longitudinal control characteristics.

*****Not a silly argument on actual turn performance, just a quick ballpark so readers understand the importance and general effect of encountering the buffet on turn performance.

robtek

07-19-2012, 02:16 PM

Could please a mod put a stop to the personal attacks and the derailing of this thread?

taildraggernut

07-19-2012, 02:28 PM

Not only that, it is unstable. That means your coefficient of moment increases each cycle instead of decreasing.

An unremarkable quality shared with many other types.

So if you pull a 6 G turn and did nothing except hold the stick fixed, the next oscillation will exceed 6G and continue to increase with each cycle until the airframe is destroyed.

Above Va, large or abrupt elevator control can more easily exceed the airframe limitations of 6G for damage

inconsistency, first quote you are already at 6G and expect airframe failure beyond that, second quote you say the limit is 6G, the limit was more like 10G

That is the reason why "flick" maneuvers were not allowed in it.

incorrect, the MkII low speed flick manouvers were permitted.

1. The Spitfire should be twitchy and unstable gun platform. IIRC, in IL2, people used to complain about the "twitchy" behavior or the Corsair and P-51's so I am sure it is within the games engine to model a twitchy airplane.

It should take very careful and small stick movements to get the gun sight on target. That means a Spitfire pilot will require more skill to hit a maneuvering target than he would need in a stable platform such as the Hurricane.

interestingly enough the Hurricane pilots notes describe a very similar longitudinal stability to the Spitfire

The longitudinal stability characteristics of the Spitfire requires skilled flying to achieve a maximum performance turn. In a stable airplane, the pilot would have a much easier time keeping the aircraft at the maximum rate of turn velocity and a less violent buffet would have subsequently reduced effects on the turn performance.

Below Va, the Longitudinal instability of the Spitfire make it more difficult for the average pilot to prevent an acelerated stall or overcontrol the aircraft by pulling deeper into the buffet zone.

Why? the elevator controls were light, requring much less effort on the part of the pilot to correct.

In this thread we have focused primarily on the Longitudinal stability. Most of the Spitfires issues stem from that.

What issues? the Spitfire never built up a reputation for any 'issues', can you at least give me the benefit of the doubt and provide some examples of documented events which gave the Spitfire any sort of bad reputation, it's a fair question.

For example, the heavy lateral control forces would not be an issue if the control forces were equal on all axes. The control harmony was poor in the Spitfire and Gimpy raises a good point:

it states clearly in the pilots notes that the exeptionally heavy ailerons were only apparent at very high speed, certainly not the sort of speeds one is likely doing in a combat turn where the speed is more likely decreasing, in a sustained turn there is little need for constant aileron correction, bad harmonisation is of no consequence here.

The pilots ability to apply lateral control would be reduced by the longitudinal control characteristics.

Again, only you seem to be able to understand this, just explain it in simple terms, how does elevator affect aileron control?

*****Not a silly argument on actual turn performance, just a quick ballpark so readers understand the importance and general effect of encountering the buffet on turn performance.

Quite right, no silly arguments here, just a need to have some very counter intuitive statements explained, Glider is 'spot on' when he said that buffet simply acts as a device to say 'hey bud ease off the back pressure a little'

taildraggernut

07-19-2012, 02:32 PM

Could please a mod put a stop to the personal attacks and the derailing of this thread?

I don't see any 'personal' attacks....unless asking questions or having a different oppinion is classed as an attack?

Robo.

07-19-2012, 02:42 PM

1. The Spitfire should be twitchy and unstable gun platform. IIRC, in IL2, people used to complain about the "twitchy" behavior or the Corsair and P-51's so I am sure it is within the games engine to model a twitchy airplane.

It should take very careful and small stick movements to get the gun sight on target. That means a Spitfire pilot will require more skill to hit a maneuvering target than he would need in a stable platform such as the Hurricane.

I am sure that you're aware that this is already the case in the sim.

lane

07-19-2012, 04:10 PM

Ok.. NACA report on stalling characteristics of the same MK V
http://i822.photobucket.com/albums/zz147/winistrone/aebc089d.jpg

http://i822.photobucket.com/albums/zz147/winistrone/ff51dc44.jpg

Further on in the report

http://i822.photobucket.com/albums/zz147/winistrone/59551859.jpg

http://i822.photobucket.com/albums/zz147/winistrone/6f5ead08.jpg

Nice post winny. See also related R.A.E. Technical Note No.Aero 1106 - Comments on N.A.C.A. Advance Confidential Report Nos.A.R.C. 6423 and 6422 - "Stalling charteristics of a Supermarine Spitfire VA airplane" and "Measurments of the flying qualities of a Supermarine Spitfire VA airplane" (http://www.spitfireperformance.com/rae1106.pdf)

lane

07-19-2012, 04:14 PM

Spitfire I K-9787 & K-9788 were tested by A. & A.E.E. (http://www.spitfireperformance.com/k9787-fuel.html) and a report issued in June 1939 on Fuel consumption tests, handling and diving trials.

Longitudinal stability was measured and records attached to the report: Fig 3. Stability Records (http://www.spitfireperformance.com/k9788-stability.jpg)

Regarding stability:

http://www.spitfireperformance.com/Spitfire-I-K9787-pg18-ii.jpg

http://www.spitfireperformance.com/Spitfire-I-K9787-pg18-iii.jpg

Control and stability at the stall was tested in accordance with standards stipulated in A.D.M.293. The Spitfire I handling was found satisfactory and the aircraft deemed fit for service use. Of particular note it was concluded that during acrobatics: "Loops, half rolls off loops, and slow rolls have been done. These manoeuvres are easy to make and the aeroplane behaves quite normally in all of them."

CaptainDoggles

07-19-2012, 04:19 PM

Thanks for posting, Lane.

Longitudinally, the aircraft is stable with centre of gravity forward, but is unstable with centre of gravity normal and aft with engine 'OFF' and 'ON'.

So at normal CG, the A&AEE concludes that the aircraft is longitudinally unstable. I'm sure certain characters will try to wriggle out of this one, but it seems open-and-shut to me. I'm sure we will be deluded with marginally-relevant allusions to British aerodynamics pioneers, and pilot quotes saying that the Spitfire was a dream to fly. Nobody's saying it wasn't a good aircraft.

Seeing people describe this thread as a "character assassination" has been amusing.

ACE-OF-ACES

07-19-2012, 04:20 PM

CaptainDoggles

07-19-2012, 04:27 PM

So assume for a moment that the Spit was as unstable as some would have us belive.. You mean like the British Aeroplane & Armament Experimental Establishment?

Than ask yourself.. How did such an unstable plane that was outnumbered win BoB?It's the pilot, not the plane.

taildraggernut

07-19-2012, 04:30 PM

Thanks for posting, Lane.

So at normal CG, the A&AEE concludes that the aircraft is longitudinally unstable. I'm sure certain characters will try to wriggle out of this one, but it seems open-and-shut to me. I'm sure we will be deluded with marginally-relevant allusions to British aerodynamics pioneers, and pilot quotes saying that the Spitfire was a dream to fly. Nobody's saying it wasn't a good aircraft.

Seeing people describe this thread as a "character assassination" has been amusing.

Appart from ACE there, can you quote 'anybody' that said the Spit was not unstable?

No I didn't think so, in fact nobody is denying it, the instability is 'not' the apparent problem that Crumpp is trying to emphasise, the Mustang was longitudinaly unstable, heres an example where you needed to take your own advice and pay attention to what people write.

taildraggernut

07-19-2012, 04:38 PM

So assume for a moment that the Spit was as unstable as some would have us belive..

Than ask yourself.. How did such an unstable plane that was outnumbered win BoB?

At which point your BS meter should be pegged in the red! ;)

ACE the Spitfire was unstable....it just wasn't a problem, it was easy to fly

the question should really be how did rookie pilots with barely any experience on type (lets face it even the experienced Spitfire pilots didn't have much time on type at the time of BoB) manage to fly it if it was so 'dangerous' to handle?

CaptainDoggles

07-19-2012, 04:39 PM

Appart from ACE there, can you quote 'anybody' that said the Spit was not unstable? In fact, yes I can.

Here:

Crumpp is putting a worst-case scenario on the "buffeting"

...

in other threads he has gone as far as to claim that early Spitfires were longitudinally unstable and dangerous to fly
Now, until Crumpp, or anyone else, can prove beyond reasonable doubt that NACA got their cg calculations right there is a question mark over the longitudinal stability of this Spitfire VA as tested.
The NACA test discovered what they discovered - I can't argue with their findings, FOR ONE PARTICULAR AIRCRAFT. However I cannot agree that these are representative of the breed.

--

No I didn't think so Foot in mouth, etc.

Now let's stop this silly derailment of this thread and stay on topic :)

taildraggernut

07-19-2012, 04:41 PM

In fact, yes I can.

Here:
Foot in mouth, etc.

Sorry no cigar, only NZTyphoons quotes actually mentions stability and even then it is more emphasis on the dangerous to fly part, which clearly the Spitfire was not dangerous to fly...at all.

ATAG_Dutch

07-19-2012, 04:45 PM

So with a full tank, trimmed for level flight, pulling back on the stick then releasing to neutral would return the aircraft to level flight.

With a half full tank in the same conditions, pulling back on the stick would need a push on the stick to return to normal flight, and a bigger push when the tank is near empty.

That's my simplistic understanding of longitudinal stability or not as the case may be.

All modern military aircraft are designed with inherent instability which requires a computer to control. Instability is necessary for manoeuvrability.

I totally fail to see the point in this thread, other than to ask the devs to model a changing CofG and longitudinal stability according to fuel load. Is that the point?

CaptainDoggles

07-19-2012, 04:51 PM

I totally fail to see the point in this thread, other than to ask the devs to model a changing CofG and longitudinal stability according to fuel load. Is that the point?

Here's a simple example from the game: Right now, to hold a turn in the spit you have to hold the stick back a significant amount.

In reality, after initiating the turn I believe it was necessary to relax your pressure on the stick (move it closer to center). Otherwise, the aircraft could tighten its turn, and if you are above corner speed that means it would be easy to inadvertently exceed the G limits and damage the airframe.

There's a quote I remember reading from a pilot who said he actually had to push the stick almost all the way forward to hold a turn, because the aircraft kept wanting to tighten up.

--

I also think that the very light stick forces and (lack of) control harmonization should be modeled.

winny

07-19-2012, 04:51 PM

I have another question, the RAE refer to the bf-109 as being " too stable for a fighter".

So is instability a good or bad thing?

ACE-OF-ACES

07-19-2012, 04:55 PM

ACE the Spitfire was unstable....it just wasn't a problem, it was easy to fly
Agreed

Note I did not say it was not unstable.. My point was if it was as 'unstable' as some would have us belive than those Spits would have been falling out of skys as soon as the pilot moved the stick

Al Schlageter

07-19-2012, 04:56 PM

I have another question, the RAE refer to the bf-109 as being " too stable for a fighter".

So is instability a good or bad thing?

It depends if one is BLUE or RED. ;)

ATAG_Dutch

07-19-2012, 04:57 PM

There's a quote I remember reading from a pilot who said he actually had to push the stick almost all the way forward to hold a turn, because the aircraft kept wanting to tighten up.

I too have read such anecdotes, however the aircraft had to be returned to the factory for a new monocoque, as for some reason a batch of Spits had been produced out of shape.

Dangerous to trust pilot's anecdotes, as we keep being told. ;)

Edit: Plus you'd be unconscious well before you endangered the airframe.

CaptainDoggles

07-19-2012, 04:57 PM

I have another question, the RAE refer to the bf-109 as being " too stable for a fighter".

So is instability a good or bad thing?

I've read that quote, but Mike Williams seems to have sort of picked it out without including a lot of context from the original source, so it's hard to know exactly what they were referring to.

Here's the quote for people unfamiliar:
Longitudinally the aeroplane is too stable for a fighter. There is a large change of directional trim with speed. No rudder trimmer is fitted; lack of this is severely felt at high speeds, and limits a pilot's ability to turn left when diving.

Now, the way I interpret it is that they're referring to the trim problem. I could be wrong. There could be a truncated sentence or two preceding the quote that makes it more clear, but that's how I interpret it.

Edit: I think in this case that they're correct. You don't want the pilot's attention on trimming the aircraft every five seconds; you want the pilot's attention devoted to situational awareness.

taildraggernut

07-19-2012, 04:57 PM

Agreed

Note I did not say it was not unstable.. My point was if it was as 'unstable' as some would have us belive than those Spits would have been falling out of skys as soon as the pilot moved the stick

Yep, and if instability was a problem then Mustangs would have been falling out of the sky too, oddly enough the Mustang case was the reverse situation with regards to fuel load, a full fuselage tank made it unstable in all conditions.

CaptainDoggles

07-19-2012, 05:05 PM

This quote says it best, IMO:

To be fair, there are loads of references by pilot's to having to either wedge their elbows into the side walls or into their own stomachs to steady themselves.
Quite a few mention going 2 handed. They adapted.

As in most cases in WW2, the pilot's coped with the quirks of their machines and got the best out of them ( the good ones at least ).
Exactly, one of the quirks of the Spit was the extreme easy elevator, great for experts, more difficult for beginners; The difference to planes with "normal" handling should be in the game.
Same for the very heavy elevator at very high speeds (>600 km/h) in the 109, i.e.

I guess it comes down to those who want a faithful depiction of reality, or those who want their favourite aircraft to be the best.

Right now, the Spit and 109 handle very generically, if you will. We have a situation where there's two aircraft, and they're not really a spit or a 109, it's more like we have two aircraft where one turns better and one climbs better. That's why I want threads like this to continue; because these are two of the most-researched and most-documented aircraft of the war. They should have distinct, unique handling qualities. You should be able to feel the 109's slats deploying, etc.

ACE-OF-ACES

07-19-2012, 05:07 PM

Yep, and if instability was a problem then Mustangs would have been falling out of the sky too, oddly enough the Mustang case was the reverse situation with regards to fuel load, a full fuselage tank made it unstable in all conditions.
Exactally!

Fact of the mater is most if not all modern fighers are designed to be unstable.. It is what makes them so manuverable..

It is true now and it was true than

Only difference is today it takes a computer to act as a middle man between the pilot and the plane to keep it from falling out of the sky.. Where as in WWII the pilot was responsable.. That is to say they can make them even more unstable and thus more manuverable today due to computers..

In summary

What ever the instability was in WWII wrt the Spit, Mustang, etc..

It was not so much that the pilot could not deal with it to get the job done..

Put another way a cessna is a great plane for modern civ pilots in that it is so stable that it practaly flys itself better when the civ pilot lets go of the stick.. But a cessna is not and would not make a good WWII figher! ;)

taildraggernut

07-19-2012, 05:08 PM

This quote says it best, IMO:

I guess it comes down to those who want a faithful depiction of reality, or those who want their favourite aircraft to be the best.

I think you are spot on, and every time this Crumpp chap is cornered when debating the alleged problems with the Spitfire his usual 'thugs' jump in to cause a disturbance, in a way to prevent their favourite fighter being outclassed in 'any' way.

ATAG_Dutch

07-19-2012, 05:09 PM

This quote says it best, IMO:
I guess it comes down to those who want a faithful depiction of reality, or those who want their favourite aircraft to be the best.

So, you want the light elevators of the Spit, and the heavy elevators of the 109.

Where does the 'normal' bit come in? Which of the aircraft in the game behave 'normally'.

And does it make a difference whether i've got a G940 or a 3D Pro?

ACE-OF-ACES

07-19-2012, 05:10 PM

CaptainDoggles

07-19-2012, 05:10 PM

I think you are spot on, and every time this Crumpp chap is cornered when debating the alleged problems with the Spitfire his usual 'thugs' jump in to cause a disturbance, in a way to prevent their favourite fighter being outclassed in 'any' way.

I think you will find there are just as many 'thugs' on the Allied side of things, who get hot under the collar when there's the potential that the Spitfire might not be the aircraft equivalent of Zeus himself.

winny

07-19-2012, 05:13 PM

I've read that quote, but Mike Williams seems to have sort of picked it out without including a lot of context from the original source, so it's hard to know exactly what they were referring to.

For your reference, the quote, in context.

http://i822.photobucket.com/albums/zz147/winistrone/e3a496bc.jpg

Apologies for the quality, it's an iPad screen grab.

Al Schlageter

07-19-2012, 05:14 PM

CaptainDoggles

07-19-2012, 05:15 PM

So, you want the light elevators of the Spit, and the heavy elevators of the 109.Among other things, yes.

Where does the 'normal' bit come in? Which of the aircraft in the game behave 'normally'.Well for example the Hurricane, by all accounts, was a very stable gun platform. I don't think you'll find anyone disputing this. That could maybe be classed as "normal".

Every aircraft has its quirks and problems, of course. But right now the major difference in game between a Hurri and a Spit is that one is faster. That really shouldn't be the case, don't you think? They should feel different.

And does it make a difference whether i've got a G940 or a 3D Pro?Of course it does.

CaptainDoggles

07-19-2012, 05:17 PM

Only when the other thugs try to castrate the Spitfire.

I don't consider asking the developers to model accurate handling characteristics to be a castration.

taildraggernut

07-19-2012, 05:17 PM

I think you will find there are just as many 'thugs' on the Allied side of things, who get hot under the collar when there's the potential that the Spitfire might not be the aircraft equivalent of Zeus himself.

i think you will find it's the total closed mindedness of people like Crumpp who inflame things, every time he gets nailed with an awkward question he vanishes and then you and some others jump in and start some kind of riot with all the 'please stay on topic bla blah', why is it when I've asked Crumpp all these questions I end up in a debate with you?

taildraggernut

07-19-2012, 05:18 PM

Well for example the Hurricane, by all accounts, was a very stable gun platform. I don't think you'll find anyone disputing this. That could maybe be classed as "normal".

The Hurricane is described as longitudinally unstable in the pilot's notes.

ATAG_Dutch

07-19-2012, 05:19 PM

Well for example the Hurricane, by all accounts, was a very stable gun platform. I don't think you'll find anyone disputing this. That could maybe be classed as "normal".

Every aircraft has its quirks and problems, of course. But right now the major difference in game between a Hurri and a Spit is that one is faster. That really shouldn't be the case, don't you think? They should feel different.

The Hurri was a stable gun platform largely because of the close grouping of the guns, as against the wide spread along the wing of the Spit. The instability in the Spit when firing was in the yaw axis owing to the uneven firing of the guns.

The Hurri and the Spit in game feel completely different. The Spit is lively, light on the controls, the Hurri is sluggish in comparison and stalls far too easily for me. They're completely different Doggles mate. ;)

CaptainDoggles

07-19-2012, 05:19 PM

i think you will find it's the total closed mindedness of people like Crumpp who inflame things, every time he gets nailed with an awkward question he vanishes and then you and some others jump in and start some kind of riot with all the 'please stay on topic bla blah', why is it when I've asked Crumpp all these questions I end up in a debate with you?

If you don't want other people jumping in, then take it to PM. This is a public forum, not a dueling arena.

I furthermore don't think that wanting to stay on topic is "starting a riot". This thread is cluttered enough as is, and I hope the moderators come and remove some of the clutter.

taildraggernut

07-19-2012, 05:20 PM

I don't consider asking the developers to model accurate handling characteristics to be a castration.

Accurate by whose standards? Ok let's see how it goes when Crumpp starts the apparent topic on the 109.

CaptainDoggles

07-19-2012, 05:21 PM

Accurate by whose standards?

Well, according to the docs that Lane posted, the A&AEE's standards.

Ok let's see how it goes when Crumpp starts the apparent topic on the 109.

I'll be just as active in that thread as I am in this one. See you there.

taildraggernut

07-19-2012, 05:24 PM

ACE-OF-ACES

07-19-2012, 05:26 PM

Ok let's see how it goes when Crumpp starts the apparent topic on the 109.
Goodluck!

I highly recomend you don't hold your breath waiting on that one! ;)

taildraggernut

07-19-2012, 05:27 PM

Well, according to the docs that Lane posted, the A&AEE's standards.

Would you mind pointing out where those standards show clearly how dangerous and what a 'death trap' the Spitfire allegedly is?

I'll be just as active in that thread as I am in this one. See you there.

I have absolutely no doubt whatsoever

Al Schlageter

07-19-2012, 05:27 PM

I don't consider asking the developers to model accurate handling characteristics to be a castration.

Have you forgotten all the 100 octane threads?

Al Schlageter

07-19-2012, 05:28 PM

I have absolutely no doubt whatsoever

It will be from the other side of the fence tho.;)

taildraggernut

07-19-2012, 05:32 PM

Goodluck!

I highly recomend you don't hold your breath waiting on that one! ;)

But it has been promised, this one has been done to death, Spitfire debates are getting boring, I wan't to get into the guts of the 109 anyway...it's everyones favourite.;)

CaptainDoggles

07-19-2012, 05:33 PM

Have you forgotten all the 100 octane threads?

No I haven't. Those threads were monumentally stupid from all perspectives.

There should be 87- and 100-octane aircraft in game. We have those now, so I feel the issue is moot and not worth discussing unless it's to correct the performance. But words cannot describe how much I just don't care if it was 100% or 0% of the RAF that was on 100 octane.

CaptainDoggles

07-19-2012, 05:34 PM

Would you mind pointing out where those standards show clearly how dangerous and what a 'death trap' the Spitfire allegedly is?I never said it was dangerous, or a death trap, and neither do the A&AEE's conclusions.

taildraggernut

07-19-2012, 05:36 PM

I never said it was dangerous, or a death trap, and neither do the A&AEE's conclusions.

Sowhat exactly is the point of this thread? Crumpp certainly seems to be saying that and you are avidly defending him.

CaptainDoggles

07-19-2012, 05:43 PM

Sowhat exactly is the point of this thread? Crumpp certainly seems to be saying that and you are avidly defending him.

As far as I'm concerned, the point of this thread is to provide a measurable definition of the spitfire's handling characteristics, and hopefully to assemble something that the developers can put in game.

Something more concrete than a pilot saying "the spitfire was easy to fly" because you can't measure that, which means you can't code it.

People think I'm here to neuter the spitfire because I have a Bf 109 in my signature. If they have the data and want to run the 109 through the same process I will accept any conclusion that the data supports.

ATAG_Dutch

07-19-2012, 05:48 PM

The early mark Spitfire was a excellent fighter.

He should've stopped there, for all this thread's been worth.

taildraggernut

07-19-2012, 05:48 PM

As far as I'm concerned, the point of this thread is to provide a measurable definition of the spitfire's handling characteristics, and hopefully to assemble something that the developers can put in game.

Something more concrete than a pilot saying "the spitfire was easy to fly" because you can't measure that, which means you can't code it.

People think I'm here to neuter the spitfire because I have a Bf 109 in my signature. If they have the data and want to run the 109 through the same process I will accept any conclusion that the data supports.

I really don't think we will get that far, ACE is probably right and Crumpp will magically get bored of the idea of educating us all as soon as he is satisfied the Spit is well and truly jaffa, I see no reason he couldn't be running concurrent threads covering both aircraft....call me cynical but I have been watching Crumpp at work for a while.

TomcatViP

07-19-2012, 06:43 PM

I am sorry to remind it to some but the Hurri won BoB statically.

[OT_Mode=ON]
The fact that the airframe reached his limitation and she was pull out of air to air action after BoB does not allow you to negate this fact in favor of the Spit.

Also one thing that made the Hurri more stable is her thicker and more robust wings. The flexibility of the Spit was not the most suitable characteristic to put guns. I guess that the new wing design that came latter was also made to improve this.
[OT_Mode=OFF]

Is longitudinal instability suitable for a fighter ?
There is different philosophy here. It would be too long to be discussed here but basically if you want a fighter to be fast and fly longer you'll make it stable. Pilot input are draggy (ailerons, elevators, rudder and most notable oscillation around the desired velocity vector). Power was low at the time. Speed being of utmost importance during WWII, basically, it would have been a bad choice to go for such a design philosophy.

So, if some plane had some problem with instability it is more probable that these were unpredictable results sourcing from modification of the airframe, added equipment or bad predictions. For example the rear tank in latter Spits was seldom used and the Mustang was not allowed to fight with the rear tank not emptied. We all know that.

The fact that the MkV was stretched forward of the CG might have been a way to reduce this problem.

Anyway if you re-read the Spit MkII manual that was posted earlier (not the one on SptPerfdotCOM), it's clearly stated that there was a prob here.

So I don't know what are all this debate for. Crumpp work (because it is obvious that this has taken time to compile for us) shld inspire at least some respect and being debated with arguments and not feelings.

May I remind here that the Spitfire legacy is not privately owned by some individuals but belong to every one?

taildraggernut

07-19-2012, 07:26 PM

I am sorry to remind it to some but the Hurri won BoB statically.

The RAF won the BoB, the Hurricane just shot down more enemy aircraft, this is statistically logical considering there were more of them and they concentrated on bombers, I don't think the outcome would have been quite the same if britain had only hurricanes...even if it meant more Hurricanes, the Spit was needed to tackle the 109.

Is longitudinal instability suitable for a fighter ?

it is if the design philosophy is geared toward manouverability.

So, if some plane had some problem with instability

Heres the thing, despite what we know of inherent problems with stability there never was any appreciable recorded issue with most of the aircraft at the time, and many of them were longitudinally unstable.

The fact that the MkV was stretched forward of the CG might have been a way to reduce this problem.

The fact the issue only got a 'stop-gap' remedy with the MkV shows that there probably was no problem of any pressing urgency.

So I don't know what are all this debate for. Crumpp work (because it is obvious that this has taken time to compile for us) shld inspire at least some respect and being debated with arguments and not feelings.

May I remind here that the Spitfire legacy is not privately owned by some individuals but belong to every one?

Yes it's clear that the Spitfire has become a 'labour of love' for Crumpp.

lane

07-19-2012, 07:26 PM

For your reference, the quote, in context.

http://i822.photobucket.com/albums/zz147/winistrone/e3a496bc.jpg

Thanks for the context winny! Here is some more "context":

http://www.spitfireperformance.com/ba-1640-1.jpg

http://www.spitfireperformance.com/ba-1640-33.jpg

http://www.spitfireperformance.com/AAEE-me109-pg1.jpg

ACE-OF-ACES

07-19-2012, 07:40 PM

Longitudinally the aeroplane is too stable for a fighter
Bingo!

Just as I was saying.. Fighters, than and now, intentionally design an alittle instability to make them more maneuverable!

So I can understand how some modern civ pilots..

Who are already blinded by their agenda

Could fool themselves into thinking a fighter that does not have the same stability attributes of their putt-putt cessna is a failure.

winny

07-19-2012, 07:51 PM

Robo.

07-19-2012, 07:56 PM

But right now the major difference in game between a Hurri and a Spit is that one is faster. That really shouldn't be the case, don't you think? They should feel different.

Just for the record - they are very very different indeed. Hurricane is much lazier in the climb and it flies ('feels') much heavier than the Spitfire, especially when the speed builds up. elevator feels different, the rudder is different and the rollrate is just horrendous. It does not retain it's energy nearly as good, if simply feels completely unique to the Spitfire and not only because of the obvious lack of speed. I can get into more details if you wish...

Other than that, I agree with what you're saying, there are many problems with the FM, but I wouldn't call them generic where plane A turns better and plane B climbs better, but I understand what you're saying.

taildraggernut

07-19-2012, 07:58 PM

For anyone who would like to read the full RAE evaluation of the 109 it's here (https://dl.dropbox.com/u/62278321/R%26M2361-me109%20handling%20test.pdf) in PDF.

It's 14 Mb and should open in your browser, you can then save it if you wish.

I hope an RAE evaluation is admissable, don't forget the British had no concept of stability and control :grin:

TomcatViP

07-19-2012, 08:12 PM

Stability and Control characteristics of the Early Mark Spitfires

That is the name of the thread.

Seems once again you didn't read it. Why you guys don't open a new one ?

NZtyphoon

07-19-2012, 08:35 PM

If you don't want other people jumping in, then take it to PM. This is a public forum, not a dueling arena.

I furthermore don't think that wanting to stay on topic is "starting a riot". This thread is cluttered enough as is, and I hope the moderators come and remove some of the clutter.

You do realise that Crumpp has made lots of assertions in his first posting which do, in fact, make them part of this thread and a matter for legitimate debate? His claims about the so-called lack of stability and control standards for all countries apart from the good ol US of A and Germany are ridiculous and call into question his neutrality in this thread.

As for the Spitfire - of course it wasn't perfect, and I have never tried to make out that it was; however, the NACA report makes it quite clear that there was some doubt about the correct cg position as measured by NACA, and that should be sufficient reason to question its conclusions.

Also, as a fighter, it was in good in good company:

http://i91.photobucket.com/albums/k304/Major_Sharpe/20050029413_2005019367-page-001.jpg

http://i91.photobucket.com/albums/k304/Major_Sharpe/20050029413_2005019367-page-002.jpg

most pilots reported that the F8F was an excellent aircraft to fly and fight in, yet there was a certain amount of longitudinal instability. It would seem that a well designed fighter could exhibit some longitudinal instability as long as it could be controlled.

6S.Manu

07-19-2012, 09:46 PM

I hope an RAE evaluation is admissable, don't forget the British had no concept of stability and control :grin:
Since they state that a captured 109 is inferior to the Hurricane as fighter, then I wonder what are the mandatory characteristics of an airplane they want to call it "fighter".

No problem... British still drive on the left side of the road.. it's a matter of preference. :-D

taildraggernut

07-19-2012, 10:08 PM

Since they state that a captured 109 is inferior to the Hurricane as fighter, then I wonder what are the mandatory characteristics of an airplane they want to call it "fighter".

No problem... British still drive on the left side of the road.. it's a matter of preference. :-D

But they didn't really say that did they, they just say the 109 is less manouverable.....a reasonable handicap as a dogfighter.

we drive on the left for a historic reason not really preference or because we have 2 heads and 6 fingers on each hand :grin:

CaptainDoggles

07-19-2012, 10:08 PM

You guys should put the 109 stuff in a separate thread.

ATAG_Dutch

07-19-2012, 11:56 PM

we drive on the left for a historic reason not really preference or because we have 2 heads and 6 fingers on each hand :grin:

And so do the Japanese. My car is a grey import from Japan. Great car too. ;)

Crumpp

07-20-2012, 12:22 AM

The Bf-109 is another thread.

This one is about the measured flying qualities of the early mark Spitfire. That means the ones in the game.

Crumpp

07-20-2012, 12:34 AM

CaptainDoggles

07-20-2012, 01:02 AM

Just as I was saying.. Fighters, than and now, intentionally design an alittle instability to make them more maneuverable!

I just want to point something out here: Adding instability does not necessarily make the aircraft more maneuverable.

Perfect example is the B-2 Spirit. Extremely unstable, but not particularly maneuverable.

Crumpp

07-20-2012, 01:05 AM

Thank you again Lane for posting those documents.

Problem is on a few in the discussion even understand the topic. For many it is a emotional affair riddled with fear their favorite gameshape will be somehow ruined.

I did not read the report but did look over the graphs from Lane's post. Here is what those graphs are telling us about the Spitfires Longitudinal stability in various conditions of flight.

Negative stability is divergent. Co-efficient of moment and Co-efficient of lift have an inverse relationship in a stable airplane. You can look at the Co-efficient of moment against Co-efficient of Lift plots in the other report Lane posted and see the slope is positive.

What does that mean in plain english. As the wing approaches CLmax, the Coefficient of Moment is well into the negative values and wants to push the nose down. Therefore, the pilot must pull the stick back to keep the nose up.

In a positive slope, as the wing approaches CLmax, the Coefficient of Moment is high in the positive values and wants to push the nose up. Therefore, the pilot has to push forward on the stick to keep the nose down.

This is confirmed behavior in our test flight document below.

Crumpp

07-20-2012, 01:09 AM

I just want to point something out here: Adding instability does not necessarily make the aircraft more maneuverable.

Perfect example is the B-2 Spirit. Extremely unstable, but not particularly maneuverable.

Exactly. Instability does not do anything except make the aircraft harder to control.

It is a myth that instability has positive effects on maneuverability. In fact, it narrows the maneuvering envelope because the pilot cannot precisely control the aircraft.

Crumpp

07-20-2012, 01:48 AM

NACA report makes it quite clear that there was some doubt about the correct cg position

:rolleyes:

31.4% MAC is quite clear.

CaptainDoggles

07-20-2012, 04:56 AM

Negative stability is divergent. Co-efficient of moment and Co-efficient of lift have an inverse relationship in a stable airplane. You can look at the Co-efficient of moment against Co-efficient of Lift plots in the other report Lane posted and see the slope is positive.

This is what I got from the report as well, but what I wasn't sure about was the difference between columns 1 and 2. Did they just run 2 trials at each flight condition and those are the results?

Additionally, it seems odd to me that in the "Engine Off" case, it appears stable in trials 5, 6, and 7 but #8 is not stable. All the other variable appear to be the same (flaps+gear are up, altitude is the same, trim set to -7.5).

Anybody know why that would be the case?

taildraggernut

07-20-2012, 07:07 AM

I just want to point something out here: Adding instability does not necessarily make the aircraft more maneuverable.

Perfect example is the B-2 Spirit. Extremely unstable, but not particularly maneuverable.

You do know it's a bomber? It's extremely unstable longitudinally and if it wasn't for the computers toning down its controls it would be extremely sensitive in pitch.

taildraggernut

07-20-2012, 07:20 AM

Exactly. Instability does not do anything except make the aircraft harder to control.

It is a myth that instability has positive effects on maneuverability. In fact, it narrows the maneuvering envelope because the pilot cannot precisely control the aircraft.

So if this is true why was the Spitfire 'known' for it's ease of control?

Interesting, yet when they wanted to increase the Spitfire roll rate they had to make it less laterally stable by clipping it's wings, so not such a myth about instability, seriously think about it, stability is a resistance to change, stability will never be conducive to manouverability, neutral to slight instability would be the ideal (which is approx where the Spitfire is) and high instability starts to require computers for control.

ATAG_Dutch

07-20-2012, 09:28 AM

Instability does not do anything except make the aircraft harder to control.

It is a myth that instability has positive effects on maneuverability.

Even your average R/C flyer could tell you just how much rubbish the above statement is.

You don't win aerobatic championships by flying an inherently stable trainer.

Nor can you fly an aerobatic championship winning aircraft hands off for very long.

As to the Spit being 'easy to fly', the key word which is always missing is 'relatively'. Otherwise anyone with a pilots licence could've been selected for fighter training . They weren't. There was a rigorous selection procedure which many pilots did not get through and were sent to other, non-fighter training units.

I still fail to realise what your thread is trying to prove.

taildraggernut

07-20-2012, 09:29 AM

Heres a couple of links that clearly show the relationship between stability and maneuverability i.e. the relationship is inverse, this is what USN student pilots are being taught, I am fairly sure the USN currently are using 'adopted' standards :rolleyes:

http://navyflightmanuals.tpub.com/P-1231/P-12310068.htm

http://navyflightmanuals.tpub.com/P-1231/P-12310031.htm

So lets get all this in perspective, longitudinal instability does 'not' mean the aircraft is difficult to control, and it 'does' mean the aircraft is more manouverable, it's all about how far on the scale you go, and the Spitfire just sits on the slightly unstable end, the 109 would sit slightly on the stable end.

I will just quote Crumpp again so you can draw your own conclusions wether he really knows what he is talking about or just has a sinister agenda.

Exactly. Instability does not do anything except make the aircraft harder to control.

It is a myth that instability has positive effects on maneuverability. In fact, it narrows the maneuvering envelope because the pilot cannot precisely control the aircraft.

TomcatViP

07-20-2012, 09:32 AM

NO NO and NOOOOO

Two of the most manoeuvrable fighters today are perfectly stables: Mig29 and Su27.

It's a matter of philosophy from the manufacturer and the air forces using it.

Today, aft positioned CG is used to lower the drag in high AoA configuration : less elev surfaces deflection (especially in the case of elevons), less tail plane surface, less drag when deflected. Have a look at the range of tailplane incidences available on modern fighters (when they do not act as airbrake).

Moreover I suspect you are mixing stability (or the lack of it) and relaxed stability (what you call instability). The former is what ease the plane in flight for the pilot and, in the case of modern plane with relaxed pitch stability, is always implemented by the flight controls (the pitch crl of F16 and airbus is ctrled by the number of inputs basically - you don't have to pull and push), and relaxed stability (akka positive longitudinal instability) used in modern fighter and Airbus airliner to reduce the drag, accelerate the pitch rate or both.

I don't see why a pilot would want an unstable aircraft especially in pitch when you have to do lengthy flight in clouds, bad weather or simply T.O at dusk . There was the same prob with the Camel during WWI. they made it instable "in purpose" to give him a way to fight the superior airfoil section used by the Germans but at a very high cost : pilot SA dramatically dropped. And there we had teh same result: Experienced pilots were at ease in that situation but rookies had all their attention drown in flying the plane. Doesn't it remind you something ? ... Like section leaders landing back to base with both his wingmen shot down as depicted in a famous 1969 movie?

... And the 47 and the 51 over Europe have told us that you don't win a war with experteen but with a range of perfectly trained young pilots at ease in planes easy to master.

Regarding the Cessna, if you really push and turn the yoke My memory tell me that the 172 is quite manoeuvrable. I won't hve had a dogfight with a 29 but still you feel secure in mountainous terrains.

ATAG_Dutch

07-20-2012, 09:40 AM

Regarding the Cessna, if you really push and turn the yoke My memory tell me that the 172 is quite manoeuvrable. I won't hve had a dogfight with a 29 but still you feel secure in mountainous terrains.

Yes, but release the yoke and the Cessna returns to normal flight due to its stability.

taildraggernut

07-20-2012, 09:43 AM

Yes, but release the yoke and the Cessna returns to normal flight due to its stability.

exactly and you get very tired very quickly wrestling a stable aircraft around the sky.

Two of the most manoeuvrable fighters today are perfectly stables: Mig29 and Su27.

the 29 is practically obsolete, the 29's inherent stability is why it no longer competes against modern fighters, and the 27 is fly-by-wire.

I don't see why a pilot would want an unstable aircraft especially in pitch when you have to do lengthy flight in clouds, bad weather or simply T.O at dusk

mainly because it gives the edge in a dogfight because of the increased maneverability, I'm fairly sure flying in cloud is not a high priority in fighter design.

Sandstone

07-20-2012, 09:51 AM

Skimming this thread, it seem that the Spitfire was longitudinally unstable in a narrow technical sense, which primarily manifested itself as a perceived sensitivity to elevator input.

However, the aircraft had generally good handling properties and pilots on both sides actually regarded it as rather easy to fly. In fact, it was successfully used by low-hours pilots without problem, so clearly the technical instability had either very little or no impact on its real-world use.

Can this be represented in a game? No, not unless the game forces the use of full-size force feedback joysticks and prevents players using response curves.

We should note that words like "instability" can have a narrow technical meaning that is rather different from their normal everyday meaning. Crumpp would have avoided a lot of confusion, much of it his own, if he had made this distinction clear from the beginning.

TomcatViP

07-20-2012, 09:57 AM

Again You are mixing instability and relaxed stability.

instability would make the plane depart itself from its velocity vector

relaxed stability is implemented in the design but ctrl the plane trough a computer. And there is a raison to that.

Exemple :

Stable or FBW stable F16 Rookie pilot: 400Kts, pull 6G -> Black out -> the plane unload by itself. Pilot woke up 10 sec after safely

Taildraggernut design instable "NutShark Uber Killer 2121" aircraft with Tomcat pilot : 400kts, pull 6G, Black out -> the plane continue to tighten the turn untill what remain of Tomcat'brain is crushed. Pilot CTG 10 sec latter.

Note:
- The 27 does not have FBW implemented. Only latter vers have pitch ctrll.
- Good luck trying to teach NATO or US fighters pilots that the 29 is obsolete. You might have the same kill rate ratio as them in BFM ;)

taildraggernut

07-20-2012, 09:59 AM

taildraggernut

07-20-2012, 10:02 AM

Again You are mixing instability and relaxed stability.

instability would make the plane depart itself from its velocity vector

relaxed stability is implemented in the design but ctrl the plane trough a computer. And there is a raison to that.

Exemple :

Stable or FBW stable F16 Rookie pilot: 400Kts, pull 6G -> Black out -> the plane unload by itself. Pilot woke up 10 sec after after

Taildraggernut design instable NutShark Uber Killer 2121 aircraft with Tomcat pilot : 400kts, pull 6G, Black out -> the plane continue to tighten the turn untill what remain of Tomcat'brain is crushed. Pilot CTG 10 sec latter.

Note:
- The 27 does not have FBW implemented. Only latter vers have pitch ctrll.
- Good luck trying to each NATO or US fighters pilots that the 29 is obsolete. You might have the same kill rate ratio as them in closed dogfight ;)

I'm not mixing anything.....but with a statement like yours I think you are mixing some volatile chemicals right now.

p.s. the Su-27 had a 'pitch only' fly by wire

http://www.milavia.net/aircraft/su-27/su-27.htm

TomcatViP

07-20-2012, 10:07 AM

I'm not mixing anything.....but with a statement like yours I think you are mixing some volatile chemicals right now.
:shock::shock:
Rgr that TDN, hve fun

Crumpp

07-20-2012, 10:10 AM

We should note that words like "instability" can have a narrow technical meaning that is rather different from their normal everyday meaning. Crumpp would have avoided a lot of confusion, much of it his own, if he had made this distinction clear from the beginning.

Really guy??

Obviously you have not read much of the documentation in this thread or seen the Cm over Cl plots.

Crumpp

07-20-2012, 10:12 AM

the relationship between stability and maneuverability

:rolleyes:

Feel free to point out where the manual states a fighter should be unstable.

Thank you.

ATAG_Dutch

07-20-2012, 10:27 AM

OK, now you're back please answer my question, this is the third time.

What is the purpose of this thread, and what are you trying to prove?

Edit: Sheesh, the bloke mustn't read very much. He's gone again.

taildraggernut

07-20-2012, 10:36 AM

:rolleyes:

Feel free to point out where the manual states a fighter should be unstable.

Thank you.

Ok, take time to very very carefully understand the point, it clearly shows how slight instability is beneficial for maneuverability....a desireable quality in a dogfighter yes? at no point have I said a fighter 'needs' to be unstable, if it is a ground pounder then stability is probably a desireable quality, if it is an interceptor then it is also probably good to be stable, but a pure air defence dogfighter would benefit greatly from being able to outmanouver an opponent.

Youre welcome.

ATAG_Dutch

07-20-2012, 10:43 AM

Maybe we should substitute the word 'manoeuvrability' for a graph demonstrating degrees of deviation per ounce of pilot effort in all axes at a given airspeed, followed by a graph showing time taken to return to normal flight following a release of the controls at a given airspeed (if at all), followed by some really patronising :rolleyes: emoticons.

Maybe then he'd get it. Then again, maybe not.

NZtyphoon

07-20-2012, 10:57 AM

The British did not have Stability and Control Standards during World War II. Only the United States and Germany had them in place.

To determine flying qualities, the RAE relied upon the individual talent of the design firm and the opinion of its test pilots.

http://img15.imageshack.us/img15/8906/britishlackofastandard.jpg (http://imageshack.us/photo/my-images/15/britishlackofastandard.jpg/)

Wrong, once again: the RAE did indeed have standards and supplied these to the aviation industry:
http://i91.photobucket.com/albums/k304/Major_Sharpe/001-1.jpg

http://i91.photobucket.com/albums/k304/Major_Sharpe/009a.jpg

During WW2, however, the demands of production testing thousands of aircraft meant that each factory adopted its own techniques, designed to test aircraft to an acceptable standard, as quickly as possible, before delivery: this did not mean that there wasn't a standard set by the RAE, simply a divergence of ways in which it was done at a production level. The same thing happened in the 'States, each factory adopted a testing regime broadly following the NACA guidelines.

6S.Manu

07-20-2012, 11:18 AM

Feel free to point out where the manual states a fighter should be unstable.

I feel "standards" can be misleading. How should a fighter be?

Standards are used to hold down the aircraft characteristics with an "ideal one" in mind.

But as Tomcat says "It's a matter of philosophy from the manufacturer and the air forces using it."

So the longitudinal instability of an airplane can be required by some airforces (more or less instability) and totally avoided by other.

One can produce an highly dangerous airplane that is really effective (look at the Tempest) while other can design a safer plane that influences greatly the pilot's range of manoeuvre.

In my opionion this thread demostrate that Spitfire had some characterics who actually were dangerous if the pilot was not experienced... the ability to reach a great amount AoA in so little time (given the low stick forces) CAN BE dangerous if the pilot is not really well trained. Above all if the manoeuvres were made by sharp actions on the stick. The pre-stall warning could easily alerts the pilot if he was entering in the turn smoothly, but since it raised only a pair of mph over the stall speed I really don't think that it could be recognizable during a sharp turn that could easily end in a violent stall.

Because of this there were pilots afraid to turn tightly.

It's like the drifting capability of a car: some capable pilots can recognize the limit and containing a loose car from spinning but an average pilot will not always succeed in it and will find himself with the car pointed at the wrong way.

Then we can talk of "aiming" in a longitudinal unstable aircraft...

winny

07-20-2012, 11:24 AM

Like I said before... Now all we need is for some data for the actual in game aircraft, instead of a MK I that is too early and a MK V which is too late...

:rolleyes:

taildraggernut

07-20-2012, 11:28 AM

In my opionion this thread demostrate that Spitfire had some characterics who actually were dangerous if the pilot was not experienced

It's Ok to have an oppinnion, my oppinion is that the stability was not a problem given the actual pilots who were flying the aircraft at the time had the bare minimum time on type and weren't ripping the wings off the aircraft, just my oppinion but the Spitfire was not famed for being an aircraft 'only experts' could fly.....quite the opposite in fact.

robtek

07-20-2012, 12:09 PM

About stability, the best one could have in a fighter is neither stable or instable but neutral stability, afaik.

robtek

07-20-2012, 12:20 PM

lane

07-20-2012, 12:22 PM

http://i91.photobucket.com/albums/k304/Major_Sharpe/001-1.jpg

http://i91.photobucket.com/albums/k304/Major_Sharpe/009a.jpg

Nice find NZtyphoon!

lane

07-20-2012, 12:23 PM

Like I said before... Now all we need is for some data for the actual in game aircraft, instead of a MK I that is too early and a MK V which is too late...

You do have a point there winny...

6S.Manu

07-20-2012, 12:42 PM

It's Ok to have an oppinnion, my oppinion is that the stability was not a problem given the actual pilots who were flying the aircraft at the time had the bare minimum time on type and weren't ripping the wings off the aircraft, just my oppinion but the Spitfire was not famed for being an aircraft 'only experts' could fly.....quite the opposite in fact.

I've not said it could be only flown by experts: I'm saying that only experts could fly it at its limits. It was a easy plane to fly below those limits.

As this is true for any plane, IMO it's easier to gain confidence in a plane who actually doesn't allow you to fly it in a wrong way than a plane who does not put limits to the pilot's input.

But involuntary spins actually happened, and some pilots were so afraid of it that they could not outturn a 109 flown by a RAF pilot (enough confident in his new ride but, imo, not as the pilots who were flying it all the time).

Towards D-Day

The Norwegian squadrons continued their operations over the channel and into France. Covering American or British bombers on their way to targets on the continent were one of their jobs. Sometimes they were on offensive patrols over France or the channel trying to get the Germans up in the air to fight. Other times they were flying low offensive sweeps into France. The youngest pilot of them all, Marius Eriksen, barely 19 years old of age got shot down when he tried a head-on attack on a FW190. He survived and was taken prisoner. His best friend Jan Eirik Løfsgaard is not so lucky and is shot down when Marius is on leave in London. Other casualties included Captain Stein Sem.

-We dived side by side heading for the coast of France. Just before reaching the coast a FW190 appeared just over and behind Sem’s plane. I called out to him over the radio but it was too late. Black smoke came out from his engine. I heard him calling to me over the radio but I couldn’t hear what he said. I last saw him breaking hard right and upwards with thick black smoke still coming out. I pulled up and to the left but the plane got into a spin and the engine stopped. I couldn’t get the plane out of the spin and knew I had to jump out. I couldn’t get the canopy open and thought I was over and done with. At 4000 feet the plane flatted out and I continued over the channel before the engine stopped again and glycol streamed out. I finally got the hood open enough to get out but the release handle hit me in my face and I had to get out by pulling myself up and kicking the stick hard enough so I would get free. Covered in blood and oil I had a hell of a time finding the parachute opener but found it after awhile and the chute opened at 300 feet. I got into my dingy and after half an hour I was picked up by a British fishing boat. – Pilot Officer Malm.

6S.Manu

07-20-2012, 12:48 PM

The missing harmony must be reflected in game, regardless about that, that many will be gaming the game and correct the joystick profiles accordingly.
And more, are longitudinal and lateral oscillations in the game?

lane

07-20-2012, 12:51 PM

The missing harmony must be reflected in game, regardless about that, that many will be gaming the game and correct the joystick profiles accordingly.

Indeed, from here (https://dl.dropbox.com/u/62278321/R%26M2361-me109%20handling%20test.pdf):

http://www.wwiiaircraftperformance.org/me109/ba-1640-harmony-aerobatics.jpg

Sandstone

07-20-2012, 01:48 PM

In my opionion this thread demostrate that Spitfire had some characterics who actually were dangerous if the pilot was not experienced... the ability to reach a great amount AoA in so little time (given the low stick forces) CAN BE dangerous if the pilot is not really well trained.

The Spitfire was flown by pilots who were not well trained by modern standards. The need to get pilots into action meant that training was relatively short and pilots were entering action with only a few hundred hour on type. However, I'm not aware of accounts describing the Spitfire's elevator response as a major challenge to the pilot. I'm certainly not aware of any reports of pilots pulling the wings off or losing control because of the elevator response. It would be interesting to find some if they exist.

I suspect some of the confusion evident in this thread is because:

i) Some posters (including, it appears, the OP) seem to regard stability as existing only in extreme values, so that an aircraft is either stable and thus perfectly safe, or unstable and thus horribly dangerous. However, the truth seems to be that while the Spitfire was indeed longitudinally unstable, this instability presented almost no problems even for relatively inexperienced pilots. IIRC, one of Crumpp's posts also describes the DC-3 as being unstable. Again, it probably was, but there is little evidence that this caused problems for its pilots. In fact, it's worth noting that most aircraft actually are spirally unstable (i.e., left to themselves they will ultimately end up in a spiral dive), but the instability mode is so slow to develop that the pilot isn't even usually aware of it.

ii) Some posters regard instability as a desireable characteristic for a fighter aircraft as if it promotes manoeuvrability. But in technical language "unstable" is not the opposite of "unmanoeuvrable" (if by the latter we mean not agile). An aircraft can be simultaneously unstable and unmanoeuvrable (DC-3), or it can be stable and manoeuvrable (Pitts Special) or it can be unstable and manoeuvrable (Spitfire), or stable and unmanoeuvrable (almost any large aircraft). Unfortunately, popular accounts and casual useage mix these terms up and sometimes use unstable to mean manoeuvrable, or imply that instability is necessary for manoeuvrability. It isn't.

Whether any of this can be represented in a flight sim is a different matter. The lack of force-feedback, short PC joysticks and the need to allow response curves all suggest to me that it would be tricky at best.

FWIW, there have been attempts to relate the pilot's experience of how easy an aircraft is to fly to deficiences in stability or other aerodynamic deficiencies of the design. One such method is the Cooper-Harper scale for evaluating aircraft flying qualities (often used by test pilots). The scale considers the aircraft characteristics and how they impose demands on the pilot in selected tasks or required operation. The scale runs from 1 (good) to 10 (very bad), with 1 defined as "pilot compensation is not a factor in desired performance" and 10 meaning that "control will be lost during some portion of required operation". On the scale, 3 is defined as an aircraft characteristic which exhibits "some mildly unpleasant deficiencies" and imposes demands on the pilot such that "minimal pilot compensation (is) required for desired performance". The scale defines 4 as requiring "moderate pilot compensation". The division between deficiencies warranting improvement is at the 3/4 boundary (not required for 1-3, required for 4-10). I suspect that the longitudinal instability of the early Spitfire if assessed on the scale would be on that 3/4 boundary - i.e., it warranted improvement but was not seen as a major deficiency.

It would have been useful if the OP had clarified some if these matters at the start.