If the unacceptable stability and control characteristics of the Spitfire are not modeled, then you will never have a simulation of the relative dog-fighting capabilities of these airplanes.

Aerodynamically the Spitfire could easily out-turn a Bf-109E series. A pilot dealing with the real world stability and control issues would leave the contest much closer than the aerodynamic analysis on paper.

The stability and control characteristics of the BF-109 were acceptable and actually conformed to a set standard based on Robert R. Gilruth's findings on flying qualities. Germany was ahead of most of the world in adopting such as standard. Japan was also on an acceptable control standard. None of this was known to the Allies until after the war.

It is interesting to note that the NACA adopted a unified stability and control in 1942 but it was not until 1945 that the USAAF (R-1815-A)and USN (SR 119A) printed their own standards using the NACA findings. The first fighter the NACA tested was a Spitfire Mk V. The aircraft failed miserably and was replaced in USAAF service as soon as possible.

Unacceptable to Who ? A NACA methodology formalised 4 or so years after the aircraft first flew. Didnt a number of US units actually switch from from MKV's to MK VIII's.

As to NACA's evaulation of the MKV the RAE in Technical note No.Aero 1106 made a bit of a rebuttal on the NACA findings. This includes some criticisms in the way NACA carried out its tests. I guess both reports should be read to draw a balanced view. The RAE document refers to NACA reports ARC 6423 and ARC 6422.

Here is the Summary or conclusions of the Langley evaluation of the Spitfire MKVA "Measurements of the Flying Qualties of A Supermarine Spitfire VA Airplane" ... not all exactly bad :)
http://img825.imageshack.us/img825/6267/langlyva.jpg

Here are the conclusions from the second Langley report "Stalling charcteristics of the Supermarine Spitfire VA Airplane again not all bad:

http://img513.imageshack.us/img513/158/langelyva2.jpg

Any stability and control engineer in existence. Remember there was no such person when the Spitfire was designed.

There is a reason why the RAE added bob-weights to correct the stick force gradient. This fixed the control force issue but did not correct the instability itself.

I am aware of the RAE rebuttal. Keep in mind the British were one of the last to adopt any kind of standard on stability and control.

Of course they thought it was fine, there was no established basis for what was acceptable and what was not. A few fatalities later though, the RAE did something about the Spitfire's longitudinal instability. Again, it made it easier to control but did not eliminate the cause of the instability.

http://img12.imageshack.us/img12/561...estability.jpg

It is right there.

You know what stick fixed stability is right?

I agree that the fighter pilots would have driven their kites closer to the limits than tought at flight school. As you indicate yourself by your phrase, aerodynamic calculations are never as accurate as to predict reproducable stall speeds. But this may go both ways that is that calculations are either pessimistic (stall would occur later than calculated) or also optimistic (stall would occur sooner than calculated). So it may be the way you stated it (the pilots drove their plane closer to the limits than what calculations would have predicted) but it may also be the other way around.

Principally I would guess that stall speeds taught to the cadets were obtained experimentally. And keep in mind that pilots appreciated when they got a feedback from the plane (e.g. buffeting) when they got close to the stall limit.

I wonder, is there a clear definition of stall at all...?

Stall is defined as the point where the airfoil's critical angle of attack is exceeded.

Captain Doggles gives a good definition:

The question is not when does the stall occur but rather how much warning the aircraft gives.

That is the conundrum faced by designers. Today stability and control is a well defined science. Aircraft designers have many more tools to take advantage and flying characteristics are a consideration almost from conception. For example, today designers build aircraft with no stall warning at all, these airplanes can be flown at maximum performance right up to CLmax without aerodynamic penalties of a buffet. To warn the pilot he is nearing a stall, an artificial device called a "stick shaker" is used.

To understand that stall warning, one must understand what buffeting is aerodynamically. It is a rapid secession of flow separation and reattachment.

When that boundary layer is not attached to a portion of the wing that portion is stalled, an airplane in turn is no longer turning at maximum rate. If you read the Spitfire Mk I pilots notes it expressly warns the pilot to ensure he experiences no buffeting in a turn. First of all when the airplane is buffeting, the turn rate is reduced even though the airfoil is not at CLmax. Secondly, the Spitfire has an extremely nasty stall that will spin and the aircraft is susceptible to airframe destruction in an aggravated spin.

If the spitfire's stability was unacceptable why would Werner Molders have written

All very subjective I know, but i can only assume that he would have been comparing it to the 109 he flew.

Just because something doesn't comply to a standard doesn't mean it lacks merit, it just means it doesn't comply to a standard.

It's just like if you get a Porche intended for the German market ands try to licence it in Australia, it would fail to meet the Australian safety standard and you wouldn't be able to legaly drive it on our roads. The same car with minor altertations to meet the Australian standards (and given an appropriate compliance plate) would be fine in Australia but in the process render it non-compliant in Germany.

Cheers!

Err yes, 36 years professional flying, including one high performance type with neutral stability (and 50+ degrees Alpha and controllable capability) and the ability to fly in both FBW and basic manual modes. So I have a basic understanding of keeping the pointy end forward.

My point is your original comment ... "If the unacceptable stability and control characteristics of the Spitfire...." is imo a sweeping one. The spitfire had issues but then so does every aeroplane. In general its handling was pretty straight forward. In addition, adding Bob weights in the pitch circuit was quite a common practice at the time.

As to your comment on the Spitfires stall :

"the Spitfire has an extremely nasty stall that will spin and the aircraft is susceptible to airframe destruction in an aggravated spin."

I think that is a bit loose as well and needs to be put into the context in which this area of handling is discussed in the pilots notes. The pilots notes (MKI anyway) mention is made in the Accelerated (or high speed) stall that if not quickly corrected could lead to structural damage. To my mind this is simply pointing out that at high speed High G departure (accelerated stall) there is a possibility of structural failure, my presumption exceeding Rolling G limits etc. This description is similar to a Flick roll at high speeds. In 1G flight the Spitfire stall was pretty straight forward. A personal work colleague and friend of mine is fortunate to fly the both Spitfire MKVIII,XVI,P51D and P40F on a regular basis. He absolutely raves about the Spitfires slow speed handling and its abilty to just "keep giving" in the high AOA region. It might not meet all the NACA requirements but it still was a very well behaved aeroplane.

Sure, no aircraft is perfect but very few safe designs have unacceptable stability and control. It is a fact that the stability and control of the Spitfire was unacceptable, resulted in fatalities, and bob weights were installed. Those issues should be modeled as they very much effect the relative dog fighting capability of these aircraft.

The major point being made on the stall is the engineering tradeoff for that large amount of stall warning in the form of early and hard buffeting is a reduction in turn rate before Clmax is reached.

A spin by definition requires an accelerated stall.

How many different kinds of aircraft? Try to think of one that repeats the warnings found in the Spitfire Mk I Operating Notes. Those warnings are all characteristics of unacceptable stick fixed longitudinal stability.

In this case the standard is a little higher. It is not about comfort but rather what will cause the death of a pilot and what will not.

The longitudinal stick fixed stability of the Spitfire was unacceptable because it could kill the pilot. In fact, it did kill and bob weights were installed on the aircraft in response.

No, just a stall.

W.

Ok guys let's not make this an other "experts" issue.

Both of you are talented with no doubts.

Facts is that raising any suspicion abt the flying qualities of the SPit enclosed you immediately in a defensive posture thx to the grands Spitfire's popes tht cruise there and elsewhere on every WWII's sims forums :(

Reading Crumps I see that he tried only to lift the case on the difficulty to perform well in the spit in slow tight turns. There shld be a far more un-forgiving ctrls pattern for doing such in the sim just like what we have with the hurri (the hurri need cte monitoring of the slip needle).

Remind that there was some extensive washout on that wings to give artificial aileron authority near the stall (what the 109 and the hurri did achieved without any washout). This is a direct layoff of the EW (ellip. wing), the thin airfoil with a max camber point put far frwd).

I think it would be more interesting to discuss the doc IvanK has posted earlier and comments all the data and small info we can gather here.

For example the stick force for the 109 is nearly the same of that of the spit mkV at 400mph !!! That's by itself is a revolution in ll2 world !!! :-)

Whether the Spit is unacceptably balanced was not the issue, was it?

The discussion WAS; are aircraft in sim over/under powered, which developed into a turning discussion.

And then,..?

"A spin by definition requires an accelerated stall. "

So are you saying you cant spin from a 1G stall entry ?

Bussard the way the SPit pop out in the skies each time it zoom up makes any comments regarding the boost and whatever useless.

Let them fix the drag of the Thing and then we will see what the Merlin has wrong (although as a Hurri pilot I don't see the issue)

Pffff that's such a commonplace... :rolleyes: [/EnvyMode=OFF]

So we are all reading from the same page, here are the relevant bits from both the Spit MK I and Spit MKV pilots notes. (The Spit MKII section is pretty much word for word whats in the MKV manual)

SPIT MKI
http://img10.imageshack.us/img10/6791/spitistall.jpg


SPIT MKI ON FLICK MANOEUVRES
http://img41.imageshack.us/img41/9532/spit1flick.jpg

Warnings on the dangers of high speed flick manoeuvers but no real dramas on Lower speed flick manoeuvres, makes sense as no chance of real overstress or excedence of rolling G etc. As you can see pilots are being encouraged to experiment with these

The section in the Spit MKV manual on Stalling and Spinning.
http://img200.imageshack.us/img200/8...vstallspin.jpg

intersting to note for the neg G cut-out debate : in the Rolling paragraph of teh Aerobatic section : "The roll being barrelled just enough to keep the engine running throughout"

Def even with an MkV, G as to be kept positive to say the least

OOhh and pls do take attention to the cruise speed ;)

http://www.alphatrainer.com/handouts.../pg_4-12-2.pdf

http://www.mountainflying.com/Pages/...revisited.html


http://www.pilotoutlook.com/airplane_flying/spin

Can you force an aircraft to spin by control input from a 1G level stalled condition?

Sure!!

What are you doing with your accelerations to the aircraft when you input those controls?

Think about it.

Thanks for posting that.

Can you post the section on maximum turn performance recommendations from the Spitfire Mk I Operating notes so that all can read it?

I think the participants will have a better understanding of what I said earlier:

Crump you are mixing terms .... early in this discussion you introduced the term Aggravated and then picked up on Accelerated as others started to use it. Aggravated in terms of aerodynamics is not a common term. The Alpha pdf you refer to is the first time I have seen it used this way. The use of the term Accelerated with respect to stalling refers to to Stall entry at greater than 1G, to do this obviously requires higher IAS to generate the additional G at the same critical AOA. So by definition An Accelerated Stall is a stall at greater than 1G. In our Spitfire discussion where structural damage was being referred to we were describing a Spin entered from a high G accelerated stall departure with subsequent excessive G (notatably rolling G which is usually dramatically lower limit than the usual quoted symmetrical G limit)

Now as to thinking about controls and accelerations at spin entry as you suggest. A standard copybook 1G stall and spin entry has you arriving at the Critical AOA in 1G flight with close to full backstick. As the stall develops (ideally a nanofart before) you smoothly apply and hold full rudder (I guess you could say this is "aggravating" the stall ). The aircraft will then autorotate and (in most cases) if the controls are held it will stabilise in a spin. That is a classic 1G un-accelertaed stall spin entry. At the departure point you are already at max AOA (at or close to full backstick at 1G) so dont have the ability to increase G therefore the stall is un-accelerated.

Is this the section you wanted posted from the Spit I pilots notes ?
http://img577.imageshack.us/img577/7397/spitturn.jpg

Sounds pretty standard to me, Max turn performance in a conventional straight wing aeroplane.

Turning just short of critical AOA is a pretty basic fighter pilot skill. The Stall buffet in many aeroplanes has "depth" and differences in the degree of buffet that can be felt through the stick. As the AOA is eased on the first clues is a low intensity buffet described in some circles as the "Buzz" as the AOA increases the buffet gets harsher (Buzz turns into buffet) eventually you get to critical AOA and the stall ocurrs. Embryo military pilots are taught to feel the subtle differences in the buffet. Max performance turning is done "On the Buzz". A standard exercise is to do this whilst airspeed and G are changing whilst holding the aeroplane on the Buzz throughout without reference to AOA instrumentation etc ... just by feel.

In the more modern types (FBW with active leading and trailing edge flaps etc) high AOA capabilty and aerodynamic configuration has you in a lot of buffet any time you are close to max turn performance ... typically in the 25-30 degree Alpha regime (except in the pussy low AOA limited F16 :). As such AOA cueing via instrumentation or audio is there to help you get the max out of the jet though there still is a certain tactile feel to just how deep into the buffet you really are.

Every pilot, be they Axis or Allied attested to the Spits flying ability.
Disregarding the BoB, at the end of the Malta aircampaign the attrition rate was 1 allied loss for every 10 LW/Italian confirmed kills. Beurling (Spit Mkv) scored 3 BF109 kills and a Ju88 in one sortie with 29 Kills over the few months he was flying in that campaign - that tells me more than any data sheet!

Now THAT's the evidence we definitely needed. *giggle*

I was taught to pull to the 'nibble', just a slightly different colloquialism I suspect.

The 'depth' of the buffet is due to washout I suspect, and very indicative of the progressive nature of the stall along the span. With light buffet, a very small inboard section of the wing has actually exceeded alpha max, but the remainder of the wing is at or near CLmax.

W.

Nobody is mixing terms.

Sure it is a common term.

http://profs.sci.univr.it/~zuccher/d...DS_JOA2007.pdf

Any stall under any acceleration is aggravated. Anytime you have uncoordinated flight, you have lateral acceleration.

http://books.google.com/books?id=nxb...flight&f=false

http://faculty.chicagobooth.edu/john...C%2061-67C.pdf

It is and I did not ask you to post it because of some abnormality. I asked you to post it because it specifically warns the pilot NOT to fly in the buffet zone and even to ease off the stick by pushing it forward.


Only in modern FBW....

Aerodynamic buffeting will not increase your turn performance, it will degrade it.

And that "buffet" has nothing to do with the aerodynamics of the aircraft. It is a programed stick shaker placed there by the engineers to let the pilot know he is nearing stall speed and is "On the Buzz" at the point the stability and control engineers put it.

Watch from 3:50 on to get a better idea what we are discussing. When you see those little pieces of sting stand straight up and then reverse, that portion of the wing is stalled.

That stall progresses if the pilot continues to increase angle of attack to CLmax until the wing can not longer support the weight of the aircraft and is no longer flying.

That flow reversal over a portion of the wing is what causes aerodynamic stall buffeting.

At 4:29 the test pilot begins recording a "light" buffet. Observe the tufts and imagine a "heavy" buffet....

http://www.youtube.com/watch?v=dUj6rmgku10

An airplane does not increase its turn rate if it experiences aerodynamic buffeting. An airplane that buffets will decrease it's turn rate when the buffeting begins.

When artificial means such as stick shaker were not available, the only choice a designer had was to reduce the amount of stall warning he gave the pilot. The less buffet, the closer the pilot can fly to CLmax without degrading his turn performance due to aerodynamic buffeting.

Crump you said :

"It is and I did not ask you to post it because of some abnormality. I asked you to post it because it specifically warns the pilot NOT to fly in the buffet zone and even to ease off the stick by pushing it forward."

Guess what you do when you go past the Buzz and get into the buffet ... you ease the back pressure off to get back into the Buzz .... Ideally the very first hint of it. Thats the art of max performance turning.

Then in response to my statement:

"Max performance turning is done "On the Buzz". A standard exercise is to do this whilst airspeed and G are changing whilst holding the aeroplane on the Buzz throughout without reference to AOA instrumentation etc ... just by feel."

You said:
"Only in modern FBW...."

Ok you are really off the plot in this response and thats just wrong.
I learnt to fly on the "Buzz" in a Winjeel and then on MB326H aircraft. Both Cable and or Manual push rod controls no Hydraulics or FBW. I also do it regularly in a YAK52. Whether you like it or not thats the way you practically get max turn performance in conventional straight wing aircraft. You want to get pretty close to Clmax to do achieve that, without an AOA gauge the first onset or the buzz IS the cue that is used. I am not the only one posting here to that effect.... see RAF_Wingers post.


You then said
"Aerodynamic buffeting will not increase your turn performance,it will degrade it."
No argument I didnt say that.... but see above response.....

You then said;
"And that "buffet" has nothing to do with the aerodynamics of the aircraft. It is a programed stick shaker placed there by the engineers to let the pilot know he is nearing stall speed and is "On the Buzz" at the point the stability and control engineers put it."

Sorry mate but with respect thats just total crap, and shows you dont really know what you are talking about. The fighters I have flown operationally the Mirage III and F18 Buffet like hell as soon as you start to get some Alpha on the jet. The Mirage III is even in buffet in the circuit ! ..... nature of the beast..... neither type has a Stick shaker or Stick Pusher system

As to Stick shakers I have flown 2 types that were equipped with these ... both commercial transports that required them certification wise both conventional Hydro mechanical controls.

Now I dont know your background Crummp but if you had some practical experience in realitvely high performance straight wing aerobatic aircraft and had been taught how to get the maximum out of it you wouldnt be saying the things you are.

Here is someone elese's view on this. The text is from a civilian Aerobatics manual. The author a qualified Military Test pilot and graduate of ETPS... and even referring to an Aeroplane with a typical WWII type wing.
The last line says it all.

http://img534.imageshack.us/img534/6210/buzzburrble.jpg

Lets put this into a practical example that is a realistic life or death situation that requires your best possible turn performance in this case Min radius.

Lets say you find yourself 90 degrees nose down pointing at the ground. You are unsure if you have sufficient height to pull out you may or may not but you must give it your best shot. How would you fly the recovery ? Any delay makes the problem worse, you need your best Turn RFN. Get it right you live get it wrong you DIE.

Well, it doesn't actually say that - as given: "Even if the aeroplane does not begin to shudder or otherwise indicate an imminent stall, it may not be turning quite as quickly as it would if the stick is very slightly eased forward."

As has been said before - the buffet region of flight has 'depth' due to washout and the progressive nature of the stall across the wingspan. It's possible for a pilot experienced on type to know how much he can pull through the buffet before a full-blown stall & consequent stall and/or flick will occur.

The 'buzz' or 'nibble' does not necessarily presage an imminent stall, it just indicates that the inner part of the wing has exceeded max AoA, the airflow has separated from that surface and is impinging on the elevator.

That's sort of true, but not completely. For a wing with washout, max turn performance might not occur until some portion of the inner part of the wing is stalled and the wing as a whole has reached CLmax.

W.

only a minor portion

Regarding buffeting it is a highly unstable flight regime by def. Generally a localized buffeting zone is set artificially during the design phase to warn the pilot that is entering the stall flight regime.

The buffeting is caused by a major recirculation of flow above the wing. Thus being unstable by definition. The Lift force ad pitching moment oscillating around a certain value cause the "shaking". Aeroelasticity plays also its role here needing more washout to give a safety margin (and more drag) (see http://www.aerospaceweb.org/question/planes/q0099.shtml)

Winger , I can put my tail plane on top of a 10m pole above the fuselage and will still experience wing buffeting. ;)

Regarding the F18 without going OT, if I wd hve been at Northrop I would hve design the buffeting point before the LERX vortex start to interact with the wings flow. A pilot would know then when he is entering high AoA flight regime. What I mean here is that the buffeting zone might be wider than in a conventional aircraft due to the interaction of conventional wing behavior and LERX.

http://www.aerospaceweb.org/question/planes/q0176.shtml

Regarding the Spitfire, the wider wing chord being rather flat (the max camber line being slightly frwd than conventional design), the pitchng moment is rather stable with AoA. This is good if you want to fit a variety of diverse equipment in a fighter aircraft but nasty when it comes to deal with a stall regime (IvanK that might give you some souvenir of teh Fr delta fighter spin ;) )

In particular once such aircraft is committed in a spin, it is more stable here than an other aircraft with shorter wing chord and more rounded airfoil (there I wld like readers fans of RoF to think abt the barn door wing profiles of British WWI planes).

That said, it is mandatory to warm young pilots about the nasty behavior of such an aircraft in the spin. Then they will be more cautious in fight and the "turnability" of a Spitfire will vary greatly with the experience of its pilot.

That's all we said here as I can understand with Crumpp writing and I think this shld be in the sim (I was saying very much the same thing years ago with IL2).

Obviously an experienced fighter pilot will laugh of "the danger of being in a spin". But wait... Germans have shown the world twice that you don't win an air-war with experienced fighters pilots. That's all abt teh Legion Condor and the Hurricane, the experteen and the P51 or the WWI JastaCirkus and SPADs.


Note :
Writing this, I remember a Spit WWII WCO commenting the guncam footage of various pilots that were convinced they have hit their prey and demonstrating to them that they hve missed mostly because their plane were always drifting. This tells us a lot of how they were flying those planes that required much more attention than conventional aircraft when manoeuvring aggressively (of course not more than the early supersonics)

PS: it's a great discussion we hve here :grin:

WEAK burble.....

Hardly the description of the Spitfire's very hard and pronounced buffet as related by the NACA and its effects on turning performance confirmed in the Spitfire Mk I notes.

I just thought I'd give some historical perspective on this.

I've got lots of BoB RAF pilot's accounts, a recurring theme from the top pilot's is "riding the buffet" Geoff Wellum mentions it in 'First Light' And I've seen it repeated quite often.

Also, when the RAE were conducting the mock dogfights against a 109 they found that in every case where the 109 managed to get behind the Spitfire, it could stay there. when they looked at why, they found that the RAF pilot's were easing off when the buffeting started, when in fact they could have flown it on the edge and even tightened it slightly.

It fits with contemporary accounts from both sides, with plenty of cases of each out-turning the other. As is usually the case, the more familiar the pilot is with his plane the better the chances of survival were. Some flew it on the edge, some flew it as per the handbook.

I am not wrong and you even agree with what I said.

Ideally the very first hint of it...... No, Ideally you have none at all and are at the point just before any buffeting occurs. That is also what the Spitfire Mk I notes relate, crazy idea huh!

If you have no other way to determine that point, it works for practical purposes.

Gee, that is exactly what I have said!!

Degree in aeronautical science....graduate type

Pilot......Aircraft Owner....several of them, they are great way to waste a lot of money! :)

Oh yeah, aerobatics too...

Umm there is no difference. The handbook tells you how to fly it to the edge...

What do you think the engineers are doing when they tell you those parameters??

Here is a secret....they are telling you how to get the maximum performance out of the aircraft, live to tell about it, and maybe be able to use the airplane on the next mission.

Mh. I think the pilots were taught to fly their planes after the handbook.

With experience and in battle they started to feel the plane and forgot about the handbook resulting perhaps in situations where they were closer to the edge than written in the handbook. One should remember that air behaviour depends on much more than just velocity and angle of attack. It may well depend on current temperature, roughness of the skin of the plane, winds and gusts, air humidity ...

What do you mean, no difference, it's the exact opposite.

You can argue with Geoff Wellum all you want. You said that the pilot's notes say to ease off when buffeting occurrs. Geoff Wellum, for one, didn't do this, and they weren't too concerned with the rule book or the maths of it either, they did what they had to to survive. I've also read of plenty of WEP abuse, bent airframes, bale outs when lost ( i.e. not bothered about using the airplane again)

I think the engineers were conservative in their pilot's notes.

Not even close. This is gaming fantasy and not the reality of flying aircraft.

Of course accidents happen and circumstances are not always ideal especially in combat. We get to hear the tails about the lucky ones who survived their experience. Unfortunately we cannot hear from the others who died because of exceeding the published limits.

Let's look at what the reality of operating aircraft has to say about the Pilot Operating Instructions:

MMMM, maximum performance = follow the book

Maximum Performance AND you get to stay alive!!

If you read this primer on Pilot Operating Instructions, you will find that for most maximum performance there is ONLY one point or airspeed that maximum performance can be obtained. That point is linked to the physical design of the aircraft and is given to the pilot by the engineers. There is nothing to be "conservative" about. Additionally, the margins are such there is very little room engineering wise to be "conservative" and still produce a machine that flys.

Read and enjoy!!

http://www.faa.gov/library/manuals/a...apter%2010.pdf

I can't put this any clearer. I'll leave it to someone who was there instead.

Geoff Wellum - " In a Spitfire, just before the stall, the whole aircraft judders, it's a stall warning, if you like. With practice and experience you can hold the plane on this judder in a very tight turn. You never actually stall the aircraft and you don't need to struggle to regain control because you never lose it. A 109 can't stay with you."

Time and time again people push machines past their operational limits, some live some die, that's not the point. The point is that 'riding the buffet' happened, for real. Geoff Wellum did it, as did many many other Battle of Britain pilots.

As for the reality of flying aircraft, what's your experience of flying Spitfires in combat?

I'll take my info from people who know what they are talking about, because they were there, thanks.




You're sarcasm is palpable.

It's simply not the truth. I'll say it again, The RAE themselves (They conducted the 109 vs Spitfire mock dogfights) found that the reason in initial tests a Spitfire could not shake a 109 of it's tail was because the pilot's were backing off as soon as the buffet set in, when in fact it was possible to fly with the juddering and make a tighter turn. So max turning at least was achieved by not following 'the book'



No if you follow the book, you can't shake a 109, and you die.

And what exactly has this got to do with combat flying? Irrelevant, they did whatever they could to stay alive.

Guys we are now entering the irrational. What is not on the book or reported being said by only a few without charts & nbr as a back up is not debatable.

One thing is sure. Some can perform more than other and surely by a slight margin (there is no post stall manoeuvrability in a spit !) some did.

What we care here as a rendering of RL situation would be that very specific node were experienced will get trough with a "slight margin" of G and other that will fear a sudden stall or fail in an accelerated stall aggravated with a wing over with a minor slip angle (that we can all agree - it's documented).

Stick shaking would be not necessary (and hardly done without th erequired hardware compatibility) but head shaking and blur with increasing effect are example of what wld be "easy" to implement. Of course this is speculation. But damn me if any reader here won't prefer TC speculations to both of your tigers pi**ng contest.

On that base it is possible to compute the exact buffeting speed with both wings level and use a charts and RL experience for the resulting bank angle achievable before the stall.

Pls be constructive. I hve the feeling that we could help to build of delectable Spitfire at LEAST !

Crumpp you really don't read what other people post. You sprout falsehoods with abandon, surprising for someone with a "Degree in aeronautical science". Your words just don't match that qualification !

I certainly switched off much of what you said at the constant "your wrong...blah, blah, blah" in your last post over how much lift a wing will produce at flow reversal causing buffeting.

I am sure you understand that aerodynamic buffet is the result of flow reversal of a portion of the wing.

It is especially silly when you flatly state the same thing I am saying and therefore agree in point.

That is not what I read. The RAE was concerned that pilots were worried about the abrupt stall and subsequent spin entry being afraid to push the airplane. Any sane person would be afraid of that.

Pilots were not finding the limit as IvanK says:

And I clarified:

Maximum turn performance will occur at the point just before buffeting begins as the Spitfire POH instructs. That is how the physics works. It does not matter what tricks our mind might play as we shake, rattle, and roll through a turn hunting for that 2D polar CLmax. If you just ease the stick forward to the point the buffeting stops, the airplane will increase in turn rate. With buffet....the entire wing is not working producing maximum lift force in the direction you want it to go....Without buffet...the entire wing is working at your command.

I wonder if when being at stall limit in a turn if the speed can be maintained? Usually induced drag increases quite a bit with increased angle of attack. And that's what one does: increasing angle of attack until buffeting. Here draf is highest. Consequence: Loss of speed ==> Closer to stall speed ==> Need to ease up on stick or gain speed by loosing altitude.

Well...new patch 109 has a little more speed.
Without WEP I can get it up to and maintain 450kph, with WEP 460kph.
Cool with me.

Hi. If you turn with stall limit, the turning radius will be very tight, but the aircraft will be very slow (angular velocity is low). If you want to turn to a theoretical maximum angular velocity (constant speed, sustainable energy for a long time), you need the corner speed (this is a basic, well-known thing. It is taught in military academies).

So what changed?
Edit: These speeds are without WEP. The "Notleistung" is 20% plus power that these should be added (of course, the efficiency of the propeller and the air resistance due to the growth rate of less than 20%, but it is certain that more than 10km/h)

+10 to 20kph/5 to 12mph
Of course that is with 10% fuel, at less than 10 meters, and no ammunition.
Did you not get an increase? I was always firmly stuck at 440kph before.

I did not tested it today, just my PC performance. But I read that the Spitfire FM is unchanged too.

In sustained level flight?
Thats what Im on about, maintained level flight for minutes on end. I was even able to barely touch 470, in level flight, for a few minutes.

I think you'll have to wait until the next patch where we know that FM's are being worked on before we can evaluate things.

Your efforts Crump are becoming tiresome, and frankly your arguments about the spitfires 'Dangerous Instability' are verging on laughable. Every post that you put up serves only to advertise your bigotry and deepen your alienation of the rest of the forum.

I'll leave on this;

1) A pitch unstable aircraft is not pleasent to fly; it tightens in turns and does not settle automatically from a disturbed path. IT is VERY hard work. EVERY pilot who has flown a Spitfire, particularly those who have flown in combat say time and again the similar thing; words like DELIGHTFUL, EASY and WONDERFUL are repeatedly used to describe the handling and time and again they use the analogy that you didn't get into a Spitfire YOU PUT IT ON. Not to labour the point, but how on earth is there any correlation between these two factors? Cos apparently according to you they co-exist in the same airframe.

In case you missed it the first time, I'll write it again: Spitfires stability was MARGINAL. That does NOT make it UNSTABLE. You, with your self proclaimed expertise on aerodynamics should know this.

2) This bob weight stuff you seem hung up on is a poor argument; I have already related as to how it only affected Mk.V variants - thats Mark Five by the way; introduced many months after the Mk I & II in game - and was a result of increasing amounts of ancilliary equipment that was loaded into these a/c being poorly loaded at squadron level. But yet AGAIN you seem to have missed or ignored someones counter argument when it doesn't fit your model. So, yet AGAIN I'll direct you to Jeffrey Quill's excellent book on the subject. But somehow I get the feeling you won't read it; might not fall into line with some of your 'well founded' opinions.

Crump, your only working to serve your increasing reputation as a stuck up opinionated blowhard. One of these days you're gonna post something ace, a real piece of pukka gen as the old saying goes, and know one round here's gonna give a monkeys cos your credibility is vanishing with every cherry picked argument you present. But please, if you wish to continue shooting yourself in the foot......

http://img268.imageshack.us/img268/5...estability.jpg

Pilots died from it....

http://img706.imageshack.us/img706/4...veaccident.jpg

Like this??

From the Spitfire Mk II Pilot Operating Notes:

http://img703.imageshack.us/img703/3...evatorload.jpg

The same warning is in the Spitfire Mk I which contains even more details.

If you want I will scan the pages from my college text from my stability and control classes. They deal a lot with the Spitfire and the DC-3 as both are famous icons that lack the most basic of stability, longitudinal. Unfortunately, Stability and Control engineering was new science at the time and nobody collected data on just how many accidents could have been prevented had these airplanes had acceptable longitudinal stability.

There is no agenda or bias, bud. You can learn something or not.

Notice, this is not MY opinion.....

http://img43.imageshack.us/img43/681/spitstability.jpg

http://img810.imageshack.us/img810/9...stability2.jpg

http://img694.imageshack.us/img694/6...stability3.jpg

http://img52.imageshack.us/img52/123/spitstability4.jpg

Here is part of that text book. Read the last myth on a stable aircraft being less maneuverable than an unstable one.

http://books.google.com/books?id=D-c...0myths&f=false

What kind of verification do you have for these sources Crummp? As far as I know you've written that stuff on an old typewriter and scanned it. Besides, when it says 'failed to meet requirements' - whose?! What requirements? For all I know the Spitfire fails to meet requirements for a heavy lift wide body! Context man, for pitys sake.

Besides, if what you infer is correct we'd have seen spitfires and DC-3s - or more accurately, there constituent parts - scattered all over the landscape because every single one was an inherently dangerous saftey hazard. Take a look how many survive into the modern day and are flown regularly and aerobatted reguularly without incident. Look at the war record of these a/c. Since when on either type is it apparent that they were falling out of the sky in pieces with a methodical regularity?

Do I have to point out that the pictoral example of a structural failure that you provide IS A BLOODY Mk. FIVE again.

Gimme strength!

Besides which where on that photo/drawing does it show that this breakup was caused by excessive g due to instability? Oh that's right, it doesnt. It could have been faulty construction, metal fatigue, flutter, any number of causes. You just assume that it's down to some inherent flaw with Spitfires stability because you've got your axe to grind.

As for your quote on the Mk. II that buffeting can cause large variation in stick travel and g - wow, revelation. Any one who's read into the spitfire knows how sensitive the elevators were. At what what point does it say ANYWHERE in that text that the a/c is longitudinally unstable or prone to taking itself to pieces in that text? It does not. You're extrapolating, badly while your at it, tying it in with other flawed and irrelevant data.

The simple fact is your opinion extrapolated from text book teachings do not correlate with the historical record from a massive amount of disparate sources. And your one textbook evidence - whose validity I suspect - is not only being qouted without context - again WHAT & WHOSE requirements - but upon re-reading them it even agrees with me - NOTE the passage that you underlined 'the small static longitudinal stability',

It says small. It does not say none. It says the stick was very sensitive to movement in pitch.

It does not say Spitfires were falling apart all over the sky.

AT NO POINT DOES IT SAY THAT A SPITFIRE IS DANGEROUSLY AND INHERENTLY UNSTABLE.

Sorry just had to laugh; read the first line of your text, then the last line of the text under the 3rd image.:

Er.... But then death and serious injury are the same thing aren't they? Like marginal stability and none, apparently.

Why? If he died, he never flew again... ;)

I find it interesting, but I do not think it Crumpp prove that the Spitfire was a bad aircraft, which is obviously not true. But there was not a perfect plane, perhaps, as some would like to believe. The Spitfire is a legend (in a good sense of the word), and not wonder if something like these test results, opinions have never enjoyed great popularity.

Fenrir comments are way too much aggressive to be relevant.

Nothing that Crumpp has says is a non-sense unless over interpreted by the reader. It fit actually many well known aero principles.

By the way Fenir, the marginal mkV was just the most mass produced Spit variant ever.

Who said the Spitfire was a bad aircraft? DC-3 is not a bad aircraft either.

The RAE investigated a series of fatal accidents and concluded that pilots were overloading the airframe on recovery.

The longitudinal instability was not corrected until the Mk V with the installation of bob weights to increase the stick force per G. Bob weights certainly help the pilot to maintain better control of his accelerations but they did not fix the actual problem of insufficient vertical and horizontal stabilizer area. That too was fixed in later marques as stability and control matured greatly as a science during the war. At the time the Spitfire was designed, the United Kingdom did not have a standard and there was no such thing as a stability and control engineer. It just was not that big a deal at the low speeds of open cockpit biplanes common before the war. As speeds and power increased though, it became very important.

Yeah folks are very emotionally tied to the Spitfire. I can even remember students in class defending it. That is why it makes such a good example for fledgling stability and control engineers.

Think about what the NACA says on the stick travel. You only have 3/4 of an inch of travel to run the wing from a CL of .3 to CLmax. The minimum standard was 4 inches.

It is no wonder the Operating Notes suggest the pilot brace himself on the cockpit walls to control the aircraft. Imagine trying to land on a gusty day getting tossed around the cockpit with only 3/4 of an inch movement between controlled flight and a stall spin accident.

The Spitfire was at about 5 lb/g, requirements were around 8 lb/g. So it was too light on the elevator.

It would be unstable if it was <=0 lb/g. It wasn't.

P-39 was less stable, with down to 2 lb/g at the most rearward CG allowed.

I don't get you ?! Negative mass in a Spit ? Is that in concordance with the black mass theory ? :rolleyes:

Do you mean inverted ctrl ?

Unstable means either that you have a too variable force to pull/push per deg of pitch (ideally it would hve been linear) or that you encounter a zone were the stick forces are reversed (but not negative). For ex the WWI Camel had a degree of reverse ctrl were you needed to push on he stick to raise the nose further up.

That is not even close to correct. You can easily have a zero static margin for a condition of flight as the NACA determined.

Cable and hinge pressure alone can give you 5lb/G.

He is confused.

He does not understand that classifying control characteristics as Neutral does not mean they are at the Neutral Point with a margin of zero as the engineering definition.

The airplane would be unflyable and that is not what the NACA or anyone else who tested and measured the stability and control of the early Spitfires concluded.

The classification is based on the what control inputs by the pilot, that is why it is termed "flying qualities".

For static that is generally the airplanes reaction to a disturbance. If the airplane returns to last trimmed condition of flight with the stick free, it has positive static stability.

If it does not return but just stays on its disturbed course, it is neutral. That is why the NACA classified the aircraft as poor in rough air. It stays on whatever course the disturbance sets it on for practical purposes.

In this case the low positive static margin is stability is probably eaten up by hinge moments or balances leaving the system neutral for all practical purposes. Certainly it would eventually return to course but the time required is longer than the parameters set for positive stability.

If the disturbance increases, it is divergent or negative.

I was too :oops:

Poor post than mine. Will delete/correct content

~S

Stick force. Thought that would be clear from the context, but reading again it is not. Sorry.

The Spitfire was tested with around 5 lb stick force per g normal acceleration.

Again so everyone is clear. This should read:

The Spitfire exhibited a stick for per g of 5lbs under the tested conditions.

Stick Force per G is not stick force nor is it something that was applied by the tester during the test. It is something that was measured and can be calculated in the design phase for a condition of flight and CG position.

It is the force required to reach 1G increment in acceleration. It represents the slope of the stick force gradient. It is a function of the hinge moments and stability margin. It is also a function of dynamic pressure and varies with altitude and condition.

IIRC, in the case of the NACA test, the stick force at CLmax was ~22lbs. How does that stack up? Sounds like such light controls would be wonderful, huh? Not at all....

To put it in perspective, the FAA dictates minimum control force to reach maximum airframe g limits. Maximum limits is not structural failure. An aerobatic aircraft catagory is rated for a maximum of 6G's for example. A quick formula to ballpark the minimum control force is weight of the aircraft divided by 140.

7500lbs/140 = 53lbs

53lbs would be considered the minimum control force the pilot should experience at a 6G acceleration.

You can begin to see why the NACA classified the Spitfire as unacceptable.

Now let's get a ballpark figure for how long it would take our pilot to stall the aircraft with the Spitfires acceleration gradient. We will fudge it with known NACA measurements that are considerably higher than the Spitfires measured 5lbs per G.

One of things engineers had to do when stability and control became a science was determine what the parameters were for a pilot to move the controls.

According to the NACA, at 33lbs of stick force, the slowest rate of pull they recorded was 33 inches per second and the fastest rate 80 inches per second. With mental distractions, this rate dropped to 22 inches per second for the minimum recorded value.

Time = Distance / Rate

Time = .75 in divided by 22 in/sec

Time = 0.034 seconds to move the stick from cruise CL of .3 to CLmax and stall at the minimum recorded value. The average pilot with the lower Stick Forces of the Spitfire could do it literally in the blink of an eye.

Do you have sources for those numbers?

You can look in the FAR.

http://rgl.faa.gov/Regulatory_and_Gu...4!OpenDocument

The stick rates comes from:

NACA RB No. L4E31

ORIGINALLY ISSUED

May 1944 as Restricted Bulletin L4E31

MAXIMUM RATES OF CONTROL
FROM GROUND TESTS

By De E. Beeler

As for the original premise of this discussion, the effect of a hard buffet for stall warning on turn performance:

http://www.flightlab.net/Flightlab.n...u%232BA152.pdf

In the absence of boundary layer devices, buffeting will increase the radius and decrease the rate of a turn. The harder the buffet and larger the buffet zone, the more dramatic the result.

Stall warning is another engineering trade off. If you produce an airplane with large amount of stall warning, it will not achieve best rate of turn at 2D CLmax. The less buffet with smaller buffet zone and less stall warning, the closer to 2D CLmax the aircraft can achieve best rate of turn.

NACA did not classify the Spitfire as Unacceptable what it actually said was .."therefore failed to meet the accepted requirements" (NACA's referenced requirements ... nobody else's) and to a specific item. If you read the various NACA reports in their entirety you don't come away with the impression that the Spitfire was a POS from a handling point of view.

http://img256.imageshack.us/img256/5341/spitunaccep.jpg

They also said with respect to being able to rapidly pull to Clmax without the risk of stalling:

http://img823.imageshack.us/img823/2...stallbehav.jpg

Something most Fighter pilots would consider a highly desirable characteristic.

CRUMPP you said above:

"As for the original premise of this discussion, the effect of a hard buffet for stall warning on turn performance:"

The premise of the discussion was NOT flying in Hard Buffet at all ! but on the very first indication i.e. The "Buzz" or the "Nibble" or the "Burble" ... what ever you want to call it. In a previous post you erroneously said the Buzz and Buffet I described was in fact the stickshaker going off even though in these aeroplanes no stickshaker system was fitted, you also told me that it was only valid technique in FBW aircraft ... even though we were talking about coventional cable/pushrod flight control systems ! You fail to accept that flying on the Buzz was/is a technique practised by Fighter pilots the world over and examples provided in this thread from at my count by 4 independent people/references ... by those that have actually used the technique....including a Spitfire pilot from the Battle Of Britain.

Thanks

Ok - I admit I shortened "failing to meet acceptable requirements" to just "unacceptable."

Was I wrong? :)

Nobody said it was a POS. There are some very good qualities the Longitudinal Instability gave the aircraft from a flying perspective. I love the Spitfire.

It was a two fingered aircraft and one can see how its pilots felt all you had to do was "think about it" and the plane responded. It is an airplane a highly skilled pilot would have love to fight in.

In rough air, Instrument conditions, as a gun platform, precision landing or precision aerobatic platform, the early marques could best be described as skittish. It certainly was not ideal for those missions and a more stable aircraft would not require as high a degree of skill to perform the same maneuvers.

In terms of your game, the excellent stall warning the type possessed means that any computer FM based on 2D Clmax calculated turn performance is optimistic.

No they don't say CLmax, they say maximum lift coefficient and they list those coefficients achieved in the report. That makes it very easy for somebody who wants to program a computer game, btw.

That is the source of the confusion between the NACA and the RAE. Somebody at the RAE thought it was 2D Clmax too.

Again, a skilled pilot would love it. He could pull very quickly to the burble and back off to the point just before to achieve that maximum lift coefficient to make his best rate of turn. All within ~3/4 of an inch of stick travel.

The United States had the ONLY stability and control standards during the war on the Allied side.

Only Germany and Japan had stability and control standards at the beginning of the war. The NACA was the first Allied organization to develop any standards. The British never did during the war and it was not until post-war that they came on board to develop any.

Remember, a stable airplane can do any maneuver an unstable aircraft can. The stable airplane can do it just as fast and more precisely requiring a less skilled pilot to do the same thing. It can also do things the unstable one cannot. Such as not destroy itself by overloading the airframe, shoot down other airplanes much faster, land with more control and precision, maneuver better in rough air, and hold a precise altitude/heading in instrument conditions.

It is amusing insight to human perception that some of the pilots were not happy when the RAE did address the Longitudinal Instability of the early marques. Some pilots actually felt the bob weights took away the maneuverability.

All they did was increase the stick force gradient to make the longitudinal control heavier. Bob weights do not effect the dynamic pressure acting on the control surface or even the hinge coefficients.

Bob weight force is simply added to the force gradient already present to achieve a higher stick force per G resulting in the perceived stick forces achieving the minimum standards.

You are welcome! :)

Why do you think I disagree with you?

Yes the correct technique to achieve maximum rate of turn performance without FBW is to fly to the first indication of flow separation and back off to the point just before that flow detaches.

Tell me this, does CoD model the effects of the stick shaker zone or does maximum rate of turn performance occur at 2D CLmax?

I imagine this is what the RAF pilots were taught, however I could easily see less-educated pilots or perhaps pilots who didn't grasp (or weren't taught) the physics misinterpreting as "fly in the buffet zone".

We haven't done a lot of testing yet as our flight models are still somewhat out of whack (see flamefests re: Spit Mk 2) and are due to be changed in the next patch.

If I were to hazard a guess it would be that buffeting does not decrease the turn rate, and is merely a cosmetic effect applied to the player's screen/speakers to warn of impending accelerated stalls.

Selective reading, again. The linked document actually states this: (2) For stick controls, W/140 (where W is the maximum weight) or 15 pounds, whichever is greater, except that it need not be greater than 35 pounds.

The spit Mk1 MTOW is 5,844 lb BTW, gives me 42 lbs according to the FAA formula for chimp-proof civil aircraft.

At what speed? What was the resulting acceleration? You're only telling half the story.

W.

?

W.

Naca Spitfire reports are available here.

thx !!

To be airworthy......

That is not the ideal by any means nor did the Spitfire have unacceptable stick force gradients.

It had a low stick force gradient and that served to aggravated the neutral longitudinal stability issue.

Although steepening the stick for per G gradient was the fix used to increase the pilots ability to safely control the aircraft, the stick force gradient was not the issue with the Spitfire.

The issue was the longitudinal stability was neutral and not positive. That makes for a twitchy airplane that is easy to stall, hard to precisely maintain a load factor in a turn, and easy to overstress the airframe.

3/4 of an inch from cruise to stall is not safe and would not be considered acceptable.

That is for all aircraft seeking certification in the United States and since most of us are all on the same standard now, much of the world.

Just to clarify. I did read it. You just think my point was the control forces of the Spitfire were bad.

You are mistaken.

They were on the low end of the scale but acceptable. I just illustrated how quickly a pilot could go from cruise to accelerated stall with the neutral stability, tiny stick travel margin, and low stick forces characteristics of the type.

It's an interesting point, and from pilot's accounts it seems true.

Time and time again Spitfire pilots say stuff like "you only had to think about moving the stick and she responded" or "the lightest touch was all that was needed". It's also supported by people who flew both Hurri's and Spits most of who say the Hurricane was more stable. The Spitfire was known to be twitchy if flown heavy handed.

I'm not convinced that it was a problem though, technically maybe, but I've never read anything where Spitfire pilot's were complaining about stability (at least up until some of the bigger ones). Isn't a little bit of unstability good for maneuverability?

I suppose it could cause problems in the 'pit if you're throwing it around simply because it must have been hard to stay relaxed on the stick.

Not at all. In fact that is big myth.

Remember, a stable airplane can do any maneuver an unstable aircraft can. The stable airplane can do it just as fast and more precisely requiring a less skilled pilot to do the same thing. It can also do things the unstable one cannot. Such as not destroy itself by overloading the airframe, shoot down other airplanes much faster, land with more control and precision, maneuver better in rough air, and hold a precise altitude/heading in instrument conditions.

Unstable just means the airplane is skittish and hard to control.

Sure it was....

The RAE even recognized it attempted to fix it. Eventually it was eliminated in the very late marques with an empennage redesign.

So, when someone refers to a Modern Aircraft being unstable (I'm thinking of the ones that need a computer to fly them) are they talking about the same 'unstability'? Is it even true? (I'm not arguing here, I'd just like to know)

About the 'problem', how come the vast majority of Spitfire pilots say it was so easy to fly? How did this problem manifest it's self?

YES!! They are much more maneuverable than if the designer had built a stable aircraft.

They are so twitchy a human being cannot react fast enough to keep them from destroying themselves.

Hence you answered your own question:

:-)

IIRC, IL2 players complained quite a bit about the P51 Mustang FM's being twitchy.

That is sort of how an airplane with a small enough stability margin to be considered neutral in longitudinal flying qualities will behave.

In some cases the negative or "relaxed" stability of the aircraft is a consequence of the design, rather than an explicit design goal. I'm thinking here of the F-117 and the B-2, whose fuselages are very unorthodox due to stealth requirements. Aircraft such as these require FBW systems to stay aloft.

In fact I once heard the B-2 described as being "held in the air by sheer computing power" :lol:

Other aircraft such as the F-16 are designed to be intentionally unstable.

People often get mixed up due to the terms stable/unstable having very specific, prescribed meanings.

Yes, terminology is very important. Take the "maximum lift coefficient" term. That is often used to define the highest Coefficient of Lift over a given range.

http://www.google.com/search?q=Cruis...w=1920&bih=941

http://enpub.fulton.asu.edu/aero/mae...ingchapter.pdf

"Maximum coefficient of lift" is the term for the CLmax a section can produce and defines the Angle of Attack the airfoil stalls.

http://www.google.com/search?q=Cruis...0&bih=941&bs=1

F117 is unstable due to the interaction of the uncunventional faceted shape and aerodynamics forces. Ben Rich's team added some FBW rules (out of an F16 ;)) to free designer to go much further in the quest for stealth.

The unstability of the B2 is more linked to the clean flying wing shape with no vertical surface.

With the F16 and the Mirage 2000 the world of high perf fighter begin a new aera were the relaxed stability was the norm. What does it means ? Simply that the balancing forces around the CG were modified to allow a more compact design with the CG moving aft with high pitch authority as a direct benefit.

If you look closely at a post 80 design with FBW added you'll see that the jet engines are put at the tip end with no long draggy inner combustion pipe such as in the early jet and mid 60's (draggy because a jet engine blowing in a pipe loose that way its flow momentum due to inner wall friction. Hence a loss in propulsive power). This as freed the designer for a more balanced design improving the overall aero efficiency, lowering the empty weight (hence the direct and OP cost) and increasing the potential modifications in the .

What the FBW do ? It simply act where the pilot can't with only minor correction to correct the induced instability of the aircraft.

This principle was re-used by Airbus to minimize the tail surface of its design (drag lowered) such as the A320 witch was a seemingly logical step forward with the introduction of airfoils with a reflex zone (that cld be discussed today).

SO instability and relaxed stability is not exactly the same thing. In fact you can possibly design an unstable aircraft with relaxed stability ;)
... Or have a stable aircraft with some relaxed stabilty added :rolleyes:
Or hve a stable aircraft that can be turned unstable in pitch if you move the ctrl further bckwrd :cool:

The best way to asses the Spit instability for everyone here and its uncomfortable 3/4 inch (2cm) stick travel would be to reconfigure your joystick to allow only that travel in the pitch zone.

I am sure dozen here will instantly become Spit hatter in a single day !! :rolleyes:

By the way as ths is a Spit mkIIa thread can Devs stop the annoying characteristic of that bird in CoD that have a better P/W ratio than the 109.
Now I see most of the Spit moving in the vertical plan knowing that there is a bug with the FM. :!::-x

You don't have the real life forces on your joystick. So stick travel doesn't give you the feedback you get in the plane.

I'm not certain if you're agreeing or disagreeing with me, or just expounding on the design of the F-117 and B-2

As the required forces in the spit are very low, being the "problem", i dont think that matters so much.

There is a spring in your stick, isnt it?

Also there is always ffb a possibility.

I don't pull 5 lb on my stick, let alone 50, which even with the low stick forces in the Spit were necessary on occasion to bring the plane to the limit.

Stick forces in the Spit were low but OK, not "the problem".

hehe I agree with you. I was just complementing the answer.

Remember, size does matter......

:o

A good simulation of the Spitfire will have the aircraft twitchy or skittish and hard to precisely control in the longitudinal axis. The higher the angle of attack, the more skittish the aircraft; the lower the angle of attack, the more stable the longitudinal axis. It will take skill and constant attention to maintain a set altitude and will require small precise stick inputs to keep it from overloading the airframe on dive recovery or reaching an accelerated stall in a turn. If it does experience an accelerated stall, the stall is extremely harsh and will require immediate application of the correct control inputs ( reduce the angle of attack and increase airspeed) to keep from spinning.

It will take about 2000 feet to stop the spin and then the pilot will have recover the aircraft to flight. The correct inputs are full rudder in the opposite direction until the spin is fully recovered; Stick neutral and then slowly brought forward. The nose will come down and the rotation speed will increase until enough dynamic pressure is built for the control to be effective and stop the rotation. The aircraft will be nose down in a dive which the pilot then recovers from. The book recommends 5,000 to 6,000 foot margin to ensure a recovery from an accidental spin. Deliberate spins are prohibited because the airframe can fail under certain conditions in a spin.

Remember that the Spitfire had poor control force harmony as well. The lateral control forces have a much steeper gradient than the longitudinal. That means the aileron forces increase much faster than the elevator forces. While your elevator is very light in control forces with only a 3/4 inch travel from cruise to stall point, the ailerons require much more force to induce a given roll rate. As the Operating Instructions relate, it would require the pilot to brace his elbow in order to apply the heavy aileron force required to reach maximum deflection while being careful not to induce any elevator input.

No but variable neutral zone can makes you feel as if you had to pull harder

All is said there.

But the 3/4inch value need to be assessed one more time. We can't only rely on a single NACA report. Even if NACA/NASA docs are among the most reliable sources available on the web.

If we put things back in the contest, at the time of the evaluation the US fighter industry was struggling to produce a viable pony capable to compete with Eu models.

Certainly.

Stability and control is one area the United States was ahead of other Allied Nations.

The United States pioneered stability and control research. It was the first to quantify the science.

In fact, both the Germans and the Japanese standards were based on Warner, Norton, and Allen's work at MIT as well as Gilruth's work at the NACA.

In 1942, an RAE engineer named Sydney B Gates made his famous (in stability and control engineering circles only, lol ) "dash around America" comparing NACA research to RAE at the time. It was primarily thru Gates efforts that the RAE eventually did adopt a standard but his efforts did not reach fruition until post war. That standard mirrored the NACA's standard.

That sound just like was happening with me at Hawkinge about 10 minutes ago. 2000 foot recovery sounds about right. Recovery fairly conventional as you describe. CoD must be a good sim.

To stop the spin or to recover?

For the plane to stop spinning and I jammed on the throttle. Though I don't profess to be an expert, I'm sure that would be a lot of better pilots around.

I'll have a go at recording a track and see how the numbers stack up on the guages.

Cheers!