I don't claim the spitfire had dynamic stability, I say it is neutral, which simply means it does not try to return to it's original condition, as opposed to dynamic instability where the aircraft would increase it's amplitude of error, enough proof against dynamic instability is the fact the aircraft was not notorious for PIO (pilot induced oscilation) incidents, neutral stability is a desireable quality for an aircraft built purpousely to be agile/manouverable......seems Mitchel designed it just right.

I attached a scan from Kermodes 'Mechanics of flight' and have highlighted in red the 3 conditions, perhaps there are differences in our understanding but I feel it explains where I'm coming from.

Kermode's terminology is a bit dated, I think. What's the publication date?

Most textbooks and the industry people I know prefer the following breakdown:

• Dynamic Stability:
  • Positive
  • Negative
  • Neutral
• Static Stability:
  • Positive
  • Negative
  • Neutral

can you scan or point me to a source for this, seems a bit odd th have these distinctions......what's the difference between neutral dynamic stability and neutral static stability?

I'll see if I can provide you a scan later today, but in the interim have a look at the Centennial of Flight website which is run by NASA, so I'd say it's a reasonably authoritative source.

http://www.centennialofflight.gov/es...ility/TH26.htm

Edit: You can also have a look at this textbook, an earlier edition of which I used in school. Stengel's Flight Dynamics

Yeah I see the 'static' stability as what nasa like to call 'stick-fixed' stability, to be honest not an issue that causes difficulty in flight, it simply means the aircraft maintains attitude when displaced or simply put its light in pitch due to no resistance, hardly a bad quality in an aircraft you are trying to point around the sky to put a gunsight on target, if it were coupled with vicious characteristics in a stall it might cause problems, but again the Spit was known to be docile.

for an aircraft to be considered stable or unstable it really comes down to the dynamic stability, if the Spitfire was dynamically unstable as I believe the Spit bashers are claiming then it would have been impossible to fly in any form of manouvering due to the increasing amplitude of displacement and the subsequent pilot induced oscilations to correct it, by all accounts there was never an issue with this and further more it's practically inconceivable that a typical monoplane format aircraft of that era with a concentration of weight in it's nose to be dynamically unstable.

Kermode may be 'dated' by todays standards but given we are talking 1930/40's aircraft then it covers everything applicable for the time, the new deffinitions of stability you give really have come about since the advent of aircraft capable of all these different states.

Stick fixed is just one version of static stability, you're keeping the elevator angle constant over a speed range and check how the aircraft responds. In case of the Spitfire, no trim change occurred, so the plane would keep the same AoA over the entire speed range at the same elevator deflection. That's neutral stability.

The other version NACA was looking at is stick force stability, if you want to call it that, where you are keeping the stick force constant through the speed range and check how the aircraft responds. In case of the Spitfire, stick force increased with the speed, which in turn leads to smaller elevator deflections which means some sort of positive stability.

The Spitfire was dynamically stable.

All for longitudinal stability.

The laws of physics haven't changed since the war. Stability isn't something that an aircraft is "capable of".

I don't think anyone here is claiming the spit was dynamically unstable, nor would I say anyone here is a "Spit basher".

It's not "bashing" the spitfire to say it was not statically stable. Facts are facts. If you're going to get emotionally invested in this discussion then I'd rather not engage with you.

Well a 'spit basher' would say that, no point admitting to it if you hope to keep under the bias radar and hide the emotional investment in it's counterpart, ok glad we cleared the dynamic stability issue though as thats the only real stability issue which would cause significant problems.

it is 'spit bashing' if that characteristic is being used as an example of a stability problem, I don't mind if you don't wish to engage with me, please don't be under the impression I need it.

understanding of physics has however, stability is an inherrent capability of an aircraft, you must realise that a Cof G shift can cause a change in stability.

Is it your favorite aircraft or something? I've stated nothing but facts and you're calling me biased.

I never said it was a problem. I just said the spitfire is not statically stable.

CG shift has nothing to do with the topic at hand.

I don't aim the claim at you per se, but the general feeling on these topics are mainly led by bias, my favourite aircraft.....late mark perhaps....but not a fan of early spits, couldn't say a particular favourite but I am a secret lover of the cessna 150/152 believe it or not..bloody fantastic little aircraft.

then why was it brought up in the first place?

No, but it was a response to your claim stability is not a capability of an aircraft, if it can be changed then it is a variable, which if used to advantage is a capability, now try denying that some aircraft can shift C of G to their benefit.

Because people throw terms like "stable" around without really knowing what it means, and think that because an RAF pilot said the Spitfire was "easy to fly" that it must therefore mean the Spitfire was a very stable aircraft.

Never mind. Linguistic difference. I was just pointing out that you don't say "The P-51 is capable of static stability." You say "The P-51 is statically stable." An aircraft is designed to be stable under a particular set of conditions. If you change the conditions then the aircraft might not be stable under those conditions, but you aren't changing the aircraft.

Why on earth would I deny that and why is it relevant to the Spitfire?

Nonsense, people interpret it for exactly what it means, the spitfire was easy to fly, nobody mentioned stability until someone wanted to deride the spitfire.

Where did I say anything about the spitfire being 'capable of stability'? I will say it again it was a response to your 'black and white' statement 'Stability isn't something that an aircraft is "capable of".'

Where did I claim it was?

This is my point. Aircraft stability and aircraft flying qualities are two different things. The spitfire had good flying qualities but was not statically stable.

Like I said. Never mind. It would take too much energy to explain.

You brought it up.

the sentence should end at 'easy to fly'....static stability is just not something to consider in this case, if something is easy to fly then it has no appreciable stabiltiy issues.

You brought it up

I'm not too lazy to explain so I'll do it again, response to your odd statement.

However do free flight models fly then?

http://smallflyingarts.com/category/model-showcase/

Amazing isn't it, doggles claims he was setting the record straight for all the 'ignorants' that don't understand stability but forgot it was Kurfurst that raised the stability issue in the first place.

I don't care who raised the issue. Not every f***ing thing on these forums has to be about taking sides. Just because I have a 109 in my sig doesn't mean I am biased toward a guy who runs a 109 website. I don't care who raised the issue.
Facts are facts.

It was a linguistics thing. Never mind.

oooooohhhh! who's tired

I thought Danger Dogz pilots were supposed to be mature?

Umm....yes.....of course we are, it's a strict policy to not have a sense of humour and we all come from the planet Vulcan.

Is it necessary that all discussions on the fm turn into a verbal slap fest instead of an exchange of ideas and thoughts on a topic?

And please do not come again with "it's X who started it" or "Y is so biaised" or "Z just claims things without proof". Even if X started it if you returned the favour you're not better. And as far as I can judge all or nearly all participating in this slap fest are strongly lobbying their favorite aircraft and have made claims without proof.

For someone with an interest in genuine flight mechanics, the FM and its comparison with RL this is really boring.

*end of rant*

On the subject of stability.

The only real questions this whole debate brings up are..

1. Is this instability modlled in CloD?
2. Does any of this effect MkI / Mk II Spitfires (I'm asking because there's been mention speifically of inertia weights on MkV's)
3. Do other aircraft have similar, technical 'issues' and are they included, or is all this deeper than the sim goes?

Whe I fly sims I don't really know the 'maths' behind it all.. I either fly or fall out of the sky. Is this just a carry over from the other thread wrapped up as a problem or is it a problem?

I am sorry but that is plain wrong. If you look at almost any aircraft in the RAF at almost any time you will see that it says intentional spinning is banned. That includes the Spitfire, however it doesn't stop the fact that spinning is undertaken.
Pilots had to be trained to get out of a spin in a combat aircraft, and therefore you have to be in a spin to learn how the aircraft behaves. In reality it means that it should be done under supervision not as a matter of course until experience has been gained

Corkscrewing as an evasion technique is far more violent than a spin but all RAF bombers including Halifax and Lancasters undertook such a method.

This is one area I can speak of with some experience. When I started learning to spin some of this was undertaken in a Hunter T8. If you look at the pilots notes for the Hunter you will find, yes you guessed it, intentional spinning is banned.

Re the comment someone made about arguing with non engineers, I served in the RN as an airframes and engines artificer in the early 70's if that is of interest.

Just an observation, but the RAF never needed to develop a two seat Spit or Hurricane and trained many thousands of pilots to fly them. But the Luftwaffe needed to develop two seat 109's with the inevitable distruption on the design and production teams, presumably because they needed to.

Nobody is "attacking the Spitfire". That statement is ridicules and paranoid, deserving of a pointy tin foil hat.

The Longitudinal stability and control of the Spitfire is well documented.

YES, it can kill the pilot and that is why it is "unacceptable". It did kill pilots.

Is the Spitfire a dangerous aircraft that is not airworthy? NONSENSE, of course it is an airworthy aircraft and one the great fighter designs of WWII.

The limitations of that airworthiness are published in the Pilot's Operating Notes.

The arguments over stability and control do not make anybody look intelligent when they don't know what it means. I don't say that to be a jerk, know-it-all, or

I will try to explain the issue with the Spitfire so that it makes more sense.

All aircraft motion is oscillary. There are two categories of oscillations, long period and short. Short period oscillation represents a wide variation in Angle of Attack. Short period oscillation must be dampened in static stability and disappear without pilot input for the aircraft to be airworthy. Long Period oscillation is considered to have a constant Angle of Attack. It really does not but the variation is minor.

The Spitfire's stability issue was with long period oscillation in the longitudinal axis. These are generally not a big deal and the pilot controls them.

Static, Dynamic, stick fixed, and stick free are all different things.

First let's discuss some general stability terms:

Static Stability - The initial tendency of the aircraft movement when displaced. It is the first thing the airplane will do. If it initially moves opposite of the displacement, it has positive static stability. If it moves farther in the direction of displacement, it has negative static stability. If it does not move farther away or attempt to return from its equilibrium position, it has neutral static stability.

Dynamic Stability is the movement of the aircraft with respect to time. If it is disturbed from it equilibrium point and the maximum displacement decreases with time, it has positive Dynamic stability. If it increases with time, it has negative Dynamic stability. If it remains constant with time, the aircraft has neutral dynamic stability.

An aircraft must have positive static stability. The dynamic stability can be positive to be acceptable. The dynamic stability cannot be negative as oscillations over time are divergent or neutral as . That can cause the pilot to lose control or if coupled with accelerations on other axis can destroy the aircraft.

That coupling with yaw-wise pitch up acceleration is what can cause the Spitfire to break apart in the spin.

Control terms:

Stick fixed and stick free are two of the most abused terms in aviation when discussing stability and control. They are control terms and NOT references to stability.

Stick fixed is simply the pilot is in the cockpit, the controls are fixed so that they do not move, and the mechanical reversible linkage has mass as well as friction.

Stick free is the controls are free to move and the mechanical linkage has no mass or friction.


Now to the Spitfire early marks....the bold statements are explanations for the NACA language in the Conclusions found in "Measurements of the Flying Qualities of a Supermarine Spitfire Mk VA Airplane."

1. The short period longitudinal oscillation was satisfactorily dampened in all conditions of flight. The aircraft is positively statically stable and airworthy

2. In all flight conditions the stick fixed longitudinal stability is either neutral or unstable, and therefore failed to meet acceptable standards. The longitudinal dynamic stability is either neutral or negative. This means over time, the long period oscillations on the longitudinal axis stay the same or grow larger. It is unacceptable and is the stability issue. It is a dynamic stability issue. The requirement for a stable stick force gradient was met in all conditions of flight except for the condition with flaps down, power on. This describes how the stick forces change as we move away from the trim speed. The Spitfire's stick forces remained on a stable gradient except when the flaps were down and power on. In this condition, the stick forces would change noticeably as we moved farther from trim speed.

3. The stick force gradient in maneuvers was 5.0 pounds per G. The requirement for a force gradient of less than 6lbs per G was therefore satisfied. Some pilots in the NACA felt it was too light but that is opinion. Measurements reveal it is within standards.

4. The stick motion required to stall in maneuvers was 3/4 inch. This value is much less than the 4 inch stick travel recommended for satisfactory flying qualities. The Spitfire's elevator required a "two finger" touch. 3/4 of an inch travel to run the gamut of your useable Angle of Attack is not much at all. This is why we see the Operating Notes advising the pilot to brace his elbows on the cockpit sides to steady his hand when maneuvering. Combined with light stick forces, neutral or negative dynamic stability would make the Spitfire squirrely in any kind of chop or gust conditions. The control characteristics aggravate the stability characteristics. Only having 3/4 of an inch stick travel to work with means the pilot will have trouble in any unexpected or violent maneuver being precise. It makes the aircraft more vulnerable to such things as Pilot Induced Oscillations.

http://en.wikipedia.org/wiki/Pilot-induced_oscillation

The rest of the conclusions are normal with the exception of trim characteristics. Here the longitudinal characteristics shine and the aircraft required little trim input from changes in power or configuration.

Ok, so when is all this unacceptable and badness mean in practical terms?

Three common conditions the Longitudinal stability is dangerous are:

1. Steep turns with the gun ports open...
Stall is violent in the condition and without immediate application of the correct control input will result in a spin. We have already covered why spins can destroy the airframe in the Spitfire.

2. High speed maneuvering - Recovery from a dive or hard maneuvering above Va. Any airplane will break and even destroy itself at full control deflections above Va. It is easier to inadvertently make a full elevator control deflection in the Spitfire above Va.

3. Spins...already covered..see Operating Notes and why deliberate spins are prohibited. The Spitfire recovers from a spin very quickly relative to many WWII aircraft if accidently spun. IIRC, it loses about 2000 feet between input and recovery so after pull out you only need the recommended 4000 to 6000 feet altitude. Many WWII aircraft lost anywhere from 4000 to 6000 feet just in recovery resulting in spins being prohibited below 10,000 feet.

[QUOTE If you look at almost any aircraft in the RAF at almost any time you will see that it says intentional spinning is banned. That includes the Spitfire, however it doesn't stop the fact that spinning is undertaken.
Pilots had to be trained to get out of a spin in a combat aircraft, and therefore you have to be in a spin to learn how the aircraft behaves. In reality it means that it should be done under supervision not as a matter of course until experience has been gained
][/QUOTE]

Don't confuse accidentally spinning with intentional spinning.

Corkscrewing is not spinning.

He is not refering to "engineers" who would be called "Repairman" or "Airframe and Powerplant" qualified. He is referring to the ones all the Historians, Political Science Majors, and Lawyers started out as but could not do the math.

Don't confuse accidentally spinning with intentional spinning.

Corkscrewing is not spinning. [/QUOTE]

Crumpp I was the one in the aircraft and can promise you that they were intentional spins. You don't train in an accidental spin.

I don't understand why you find difficult to grasp that pilots have to be trained to get out of a spin in a plane they fly in combat. To do that training you need to go into a spin and be default its an intentional spin.
You need this training in case you find yourself in an unintentional or accidental spin.

PS I know a corkscrew isn't a spin and I know its more violent than a spin.

In Gliders it isn't uncommon to spin if you want to lose height quickly, as they are very slippery and you can easily exceed the VNE in a dive.

All very interesting.. But, what has a MkV Spitfire got to do with MkI/II?

And more importantly what has any of this got to do with CloD?
(I'm not being sarcastic here)

Is this level of detail contained in CloD? If we're dealing with stick forces?
Last time I checked Spitfires didn't come equipped with a Microsoft standard keyboard. I checked, it's not in the pilots notes...

Edit: I can if you wish find you some examples where BoB pilot's exceeded recommended limits etc.. Including intentional spins, proper ones. They did this mainly because someone was trying to kill them at the time.

Until it was addressed with bob-weights, it existed in all early mark Spitfires.

Read the Operating Notes....

I would have to call you on this and ask for proof the aircaft were placarded. I have done plenty of spin training and it is always performed in an aircraft approved for spining.

Check the pilots notes.

Ok, what has it got to do with CloD?

Glider,

They were trained but they did not spin Spitfires intentionally. The RAF Training Manual clearly states you will not intentionally spin an aircraft that is placarded against spinning.

The FAA, in following convention estabilished by British law says:

http://nobleairventures.com/StallandSpinAwareness.pdf

Jesus wept...:roll:

Weren't the FAA set up in 1958?

You guys would have a better understanding of what you are reading in these documents and manuals if you learned a little about Aviation Law and Legislation. It would really help you to understand how to fit them into context. Testing standards and certification of airframes, engines, fuels, pilots manuals are all part of the airworthiness of the design. They were all done on the same principles with very little variation by the convention signers.

The FAA was created by merging the two aviation authorities in the United States under one roof. Before the FAA, aircraft were administered by both the Department of Commerce and the Department of Transportation.

It relocated everyone under one roof like the Air Ministry but the rules established by convention still applied and remained in place!

The FAA is based on British Aviation Law. The same law the Air Ministry still followed in 1940.

The United Kingdom pioneered Aviation Law and was a major player in helping to establish an international standard for all convention signers.

http://specialcollections.wichita.ed...8/92-18-A.HTML

There we have our ongoing difference between the practical and experience vs theory.

Logic - how can you train someone to spin a combat aircraft without putting it in an intentional spin, plus experience - someone who has actually done it.
vs
Theory - the paper says you cannot do it therefore you didn't do it

Logic - if the fuel is installed at a station and we have pilots combat reports that says they used the fuel therefore a) the fuel was in use in those stations and squadrons and b) the aircraft had to be modified to use it
vs
Theory - I haven't got the right paperwork therefore it didn't happen

I havn't been able to find a T8 Pilots notes but the T7 was basically the same aircraft and the F6 was also exactly the same apart from the cockpit so I would expect them to have the same notes re spinning if that helps

That's just plain silly. Everybody needed two seat trainers, but it wasn't widely practiced in WW2, the need it was just began to be realized.

BTW: Supermarine Spitfire T9:

http://www.key.aero/central/images/news/2084.jpg

I will reword my previous posting:-

Just an observation, but during WW2 the RAF never needed to develop a two seat Spit or Hurricane and trained many thousands of pilots to fly them. But the Luftwaffe needed to develop two seat 109's with the inevitable distruption on the design and production teams, presumably because they needed to.

--------------------------------------------------------------------------------

Still plain silly. You want to make the lack of a proper two seat trainer variant a good thing...

I've got to step in to defend Crumpp on something......partially, let's be fair, you can't just nonsense everything someone says just because you are arguing with them.

spin training absolutely is done on aircraft 'cleared' for spinning, if an aircraft is not cleared for spinning it has been deemed so beause of some form of complexity in its recovery behaviour 'OR' it never went through spin trials for certification, as for the issue of spinning a hunter I hold my hands up and say 'I just can't comment', my belief is that the aircraft cannot be willfuly spun if it is placarded not to because those placards form a legal base that would be crazy to ignore, imagine the investigators sifting through a wreckage of a spin accident and finding the placard, insurers will just walk away and lawyers will be rubbing their hands together.

RAF pilots would have received spin training in the Tiger Moth, because spin recovery 'technique' is universal and it is a skill that can be applied to all aircraft.

But I am quite frankly amazed crumpp claims the Spitfire would 'break up' in a spin, if he really knows anything about this subject he would know a spin is 'not' a high stress manouvre, if an aircraft is going to break up in a spin it would break up in normal flight too, more than likely the Spitfire was found to have an undesireably long recovery time due to it's small rudder and/or it's neutral static stability, there really aren't many aircraft that can't actually be spun and recovered but they all have different behaviour, the clearance to spin would be granted on the basis of wether an 'average' pilot using standard recovery techniques can recover in a specified amount of time/altitude, if an aircraft can't do this it's just easier to not clear it than bring in a specialised spin training course for the aircraft.

some of my aerobatic experience is on the Military variant of the Slingsby T-67 Firefly both 160hp and 260hp(USAF T-3) variant, this aircraft was banned from spinning by the USAF and ultimately withdrawn from service after the loss of some aircraft and sadly some students and instructors too, the USAF said it was 'dangerous' and didn't recover........but I'm still alive despite having spun it countless times, the issue with the firefly is the spin recovery 'must' be done by the book but it is still just the standard technique and it will recover very predictably, get it wrong or be complacent and you beter hope you remembered the parachute if you didn't start with enough altitude, it is still cleared for spinning by the british military and civil aviation authority.

Just an observation, there were no ww2 spitfire two seat trainers and thousands of pilots were trained to fly them, and the Luftwaffe did have two seat 109's and 190's for a reason.

Personally I have often wondered why the RAF didn't have trainer versions. The jump from a Harvard to a Spit/Typhoon/whatever is a serious leap and a two seat version for at least the first say three - five flights makes sense, just to make sure they remember all the drills and can handle the extra speed.

Going way o/t here...

I'd think the main reason that the British didn't develop trainer versions of the Spitfire and Hurricane was because they had powerful advanced trainers such as the Harvard and Miles Master, which replicated most of the flight characteristics of fighters, albeit they didn't have the same high speed capabilities. One pilot who describes transitioning from the Harvard to a Spitfire in 1940 was Geoffrey Wellum; he didn't seem to have a huge amount of difficulty. The Harvard could bite pilots who got careless, but I don't know much about the Master, although it looked likely to be a good intro to the Hurricane. Interesting that it was equipped with a Rotol C/S prop. (Maybe another aircraft type for the developers???)

The Germans used aircraft such as the Ar 96. There really wasn't much call for a two-seat 109 until later in the war, otherwise the Jagdfliegervorschulen, the basic fighter training units, used various version of the 109 and captured D.520s etc; the pilots then transitioned to Ergänzungsgruppe which were similar to OTUs but attached to Jagdgeschwader

That asymetrical loading is what can cause the airframe to break apart in spin recovery.

Completely different condition of flight from in a spin.


As for the T-67, it depends on the type. Some are certified to spin and some are not. There is no blanket prohibition in either country.

Either way, the United States and Great Britain follow convention. It is impossible for an aircraft to be disapproved of something in the United States and approved of it by another convention signer without violating the convention.

Read the Type Certificate issued by the United Kingdon Civil Aviation Authority. It quotes FAR/JAR and CFR's. That stands for Federal Aviation Regulation/Joint Aviation Regulation and Combined Federal Regulations.

In otherwords, all convention signers are on the same standard for airworthiness. In aviation, what is British Law, is United States Law as well as everyone else who signed the convention. We all do things basically the same. It has been that way since 1919.

http://www.caa.co.uk/docs/1419/srg_acp_ba17-08.pdf

Not really. The Harvard is a beast to fly and if you master it, the Fighters are "easy to fly" by very subjective comparison. The Harvard's mission is prepare pilots to fly these fighters. It does that very well and will bite a student hard if he does not follow the basic rules. That is the airplanes purpose in life, to teach pilots to become pilots and not break those rules. It is not to be gentle and docile so that a pilot thinks he can get away with something. A good trainer should bite but not kill you. It is hard to make the next lesson if you are dead.

The Spitfire is "easy to fly" compared to the Harvard/Texan.

http://www.stallion51.com/news-press-releases.php?i=9

http://www.warbirdalley.com/articles/T6-sf.htm

How does the civilian aviation relate military aviation?

and in wartime as well.

anyone who's had any contact with the military will know for sure that peace time rules and war time rules are not the same. Safety levels are somewhat different.

:rolleyes:

The only exemption from the convention is the navigation rules for state aircraft in wartime.

In short, it says you don't have to file a flight plan or notify customs if you are at war with a convention signing nation to overfly their airspace with state aircraft.

:grin:

I don't think airplanes were an issue the last time the United States and England went to war.

lost me on that one, but i am willing to concede that point.:-)

The rules for airworthiness remain the same.

i don't disagree that the rules are the same.

i just don't believe they are adhered to in the same way.

IIRC, the War of 1812 was the last time England and the United States declared war on each other, Fruitbat.

Airplanes were not an issue in that war.

i'm aware of that, i just don't understand what relevance that has to do with the price of fish.

recovery....reshmovery and where the hell did that quote come from anyway, Spitfires did not break up in spin recovery but some did break up recovering from dives because granted the Spit was built a little delicately for it's sensitivity in pitch.

what exactly was your link to the CAA supposed to show me?

Of course they were adhered too. Dead is dead. It does not matter if the enemy kills you or the airplane.

Not only that, if you suddenly had everyone in your force going out breaking airplanes, what are you going to fight the enemy with while all your airplanes are getting fixed? Idiots making airplane noises on the ground because they think they know more than the designers?

You guys read a few anecdotes from a very small group who gambled and won. You don't get the wartime feedback from the 85% who lost because they are not around to tell you, "Hey, that did not work like I thought it would."


Those rules and operating limits define the airworthiness of the aircraft. Within those limits, you are flying an airplane, outside of them you are no longer in an airplane but a trainwreck headed for disaster.

I like fish....

Quite a few pages back when I first mentioned it.

All convention signers are on the same rules for airworthiness, then and now.

and the origin of that original statement?

No...it seems to just show some FAR's for certification in the US, much like American light aircraft certificates show UK/European requirements likewise, really not an indication of similarity but more of differences in standards.

And what are doing in spin recovery?

Asymmetrical loading....

With a significant yaw-wise pitch up.....in the Spitfire

An airplane with a neutral or negative dynamically stable airplane with 3/4 inch stick travel at 5 lbs per G.....

http://avstop.com/ac/flighttrainghan...maneuvers.html

Asymmetrical loading is the mechanism. It significantly degrades the airframe load factor limits when you start adding multiple axis accelerations. You are approaching the airframe limits on normal recovery. Stomp the rudder too much or add in some gusting and you can break the airplane.

Read the pilot notes as it will tell you how to operate the aircraft so that is stays within its airworthy limitations.

Hi. Only about ~100 aircraft were modified to G-12 standards (it was conversion only, G-2, G-3, G-4, G-6 types). I think these aircrafts used more for combat training, not for the basic exercises, circuits. For example, the RHAF did not use the G-12 type (Hungary also produced 109 G-6, G-8, G-14 types). If this was really necessary, then they would have converted.

Yep, this is why i hate the war stories as technical or performance "evidence". Interesting stories, but nothing more :) Best example is the maneuverability. Both sides said they're all turned better than the other side. Ok, but what were the circumstances of the situation? That is very little read, and one of the most important thing in the pre-battle situation. :rolleyes:

Not pulling out of a Vne dive thats for sure, if you think spitfires all broke up in post spin dives then every one of them would have crashed.

absolutely nothing you have written here applies specifically to the Spit, you cling on to the obscure certification entry about 'no intentional spins' which if you know anything you will accept it can be down to factors I described earlier.

A load factor of 2.5 G's......wow massive, the Spit airframe could stand 10 G's, serously find a official source for claims spitfires 'broke up' post spin.

It is a fact all convention signers follow the same rules, principles, and procedure for aircraft airworthiness.

That is why we all use the same regulations and quote them.

Here is a quick highlight of the worlds aviation conventions. The only thing state and military aircraft are exempt from is the navigation rules.

They still must abide by the convention airworthiness standards.

http://www.fabioaddeo.com/2011/02/26...nd-agreements/

10G's asymmetrically? You think?

Yup

I can't be bothered to wait for you to browse wiki or scour the internet for other obscure stuff....

You don't really seem to even know what asymetrical g load is, remember that thread about roll rate at high speed? well......diving a spit to 400 mph and applying max stick roll force.....thats aymetrical loading my friend.....I don't seem to recall wings peeling off in those tests, if it could take those asymetrical loads then there is no way in hell it will break up in spin recovery no matter how sensitve the elevator is or how staticaly neutral it is.

Well you are dead wrong bongodriver.

First of all the 10G's is to the failure point. It is 10G's on a single axis and assumes a perfect airframe. That 10 G's represents a 100% chance the airframe will be permanently deformed and we run a good chance of having the airplane turn to confetti. This is why the POH warns the airframe will certainly fail if this limit is much exceeded.

Our we run the risk of damage threshold is lower than that at 6G's.

That too, is 6G's on one axis with a perfect airframe.

Just like your car suspension wears, so does an airframe. It is not the spars or major structures that fail first, it is the ribs, skin, and supporting structures. An airframe flexes in flight, even at 1G. Gusting, accelerations, and turbulence all add wear to the airframe and lower those limits. It is just like your cars suspension wears from driving all the bumps it has to absorb.

Asymmetrical loading significantly reduces the airframe limitations. The average is about 20%. So our 6G damage limit is now 4G's with an asymmetrical loading.

Our normal spin recovery AVERAGES about 2.5G's so on AVERAGE we could spin a Spitfire safely as long as the pilot correctly and precisely applied the control inputs.

But wait, he has a very hard time being precise with control inputs especially when he is subjected to the same accelerations. Oh yeah, when he steps on the rudder, it also produces even more acceleration on the longitudinal axis adding to his difficulty.

He has 1.5G's to play with before he can damage the airframe. The airframe is now weaker and will fail at a lower point.

Now let's add in the vertical load from gusting...Oh crap we are at the threshold in light turbulence!! The POH also warns of this! Coincidence?

You botch the recovery, damage the airframe, and it re-enters the spin, as the POH once again warns the pilot about. Why can you re-enter a spin so quickly and must build up your speed? In any airplane if you don't have enough speed you can re-enter the spin. In the Spitfire is especially important. The pilot needs that speed to have better precision on the controls. He only has 3/4 of an inch of stick travel to use up all of this angle of attack at 5lbs per G. The heavier he can make that stick, the more precise he can be in controlling the acelerations. If he re-enters the spin with a damaged airframe his chances are even less of coming home.

Now do you see why spins are prohibited in the Spitfire? The average time you spin the airplane, it will come out "just fine". The margins between "just fine" and disaster are tighter than you think.

If the pilot could precisely control the accelerations and did not have the yaw-wise pitch up, it would be a much safer aircraft to spin.

What is a max stick force roll at that speed? :grin: Don't confuse stick forces and control surface deflection.

You realize that 400 mph is well over Va so full control deflection will exceed the airframe limits on just one axis......

Think about what you are saying in this claim.

I think the point is, that in a spit, during a stall-recovery, it is extraordinarily easy to exceed the stick movement necessary to overload the airframe.

Much more easy as in the comparable planes, which needed more stick-travel and force.

Exactly. Conditions mean everything and without them, it is useless to draw general conclusions.

Right, the majority of the warnings in the Spitfire Operating Notes are in relation to the unacceptable longitudinal dynamic stability.

How would this effect your game?

It compresses the turn performance differences especially for large angle of bank turns. The Spitfire is harder to control precisely in that condition and the stall is extremely rough and will result in a spin.

It is like that punk skateboarder kid. He can do some really cool tricks but when he makes a mistake, it is a whooper.

The Bf-109 on the otherhand has those LE slats on a flat top polar. It is like a a racing bicycle with training wheels.

Read the stall behaviors:

http://kurfurst.org/Tactical_trials/...ls/Morgan.html

It has yaw-wise stability issues but stall behavior is typical for an aircraft equipped with LE slats. It simply stops flying and begins to descend. No violent behaviors and no tendency to spin at all. LE slats are a typical anti-spin device if you want to spin-proof an airplane. They really are like training wheels.

Both airplanes have excellent stall warning with adequet control and can be flown in a partially stalled condition. The Bf-109's stall is a non-event and the Spitfires is a the begining of wild ride.

It is no wonder you read anecdotes of Bf-109 pilots who swore the airplane would outturn the Spitfire.

In case some folks can't be bothered to read the NACA tests, I'll post a part to put the "unacceptable longitudinal dynamic stability" into proper perspective.
Eventually, the longitudinal stability was not unacceptable. The Spitfire was accepted into service with about 20+ military air forces, was built in 20000 examples, and is still being flown today. Unacceptable longitudinal stability would mean acceptance into 0 air forces, and a production of a handful of examples, and none would be cleared for flying today.
However, it is true that the Spitfire did not meet all the requirements set by NACA in "Requirements for Satisfactory Flying Qualities of Airplanes". Other planes that failed to meet all the requirements were for instance the P-39 or the XP-51.

Interesting stuff JtD.

you sure thats the same NACA report, lol.

This instability was fixed in the Spit V.
Several Spit pilots complained that the Spit V felt sluggish. Of course the flight characteristics was not worse, just more stick movement and force was needed. iirc Crumpp showed a couple of documents about this.

Hi JtD,

Thanks for the perspective. You might find the following RAE comments of the NACA test to be of interest, in case you havn't already seen them.

http://www.spitfireperformance.com/rae1106_Page_1.jpg

http://www.spitfireperformance.com/rae1106_Page_2.jpg

According to Alex Henshaw about 25 Spitfires were known to have broken up in flight; the majority of those were Spitfire Vs which had been badly loaded at a squadron level pushing their cg too far back, and breaking up during dive recovery. As Jeffrey Quill explained, this helped lead to the addition of bob weights in the tail, then the larger mass balances on the elevators. Some of these are documented in Morgan and Shacklady.

Apart from that I'd like to see Crumpp provide some documentary evidence that Spitfires regularly broke up in flight during spin recovery.


OT slightly; NACA's report on the P-47D which had some problems of its own; one of the few fighters to meet NACA standards was the P-51H.

Putting weights to the tail for what purpose?

Better to say inertia weights (or bob weights) were added to the control circuits of the elevators - I'm not sure if later Spitfires with the bigger elevator mass balances continued to use them.

That's not what the NACA report says:

"The motion beyond the stall was not violent and an unusual amount of lateral control was available in many flight conditions, even when full up elevator was applied. "

The weight was built into the elevator circuit, in simple terms it was used to counteract the effect of light elevators and high g forces. The weight was effected by the g forces so if there was a high load the elevators needed more force to move them.

It was fitted to spitfires to solve the problem of spitfires breaking up when pulling out of a high speed dive, which was a known, and big problem at the time.

Because the elevators were so light pilots were pulling out of the dives and over stressing the airframe. There were loads of examples of this happening.

So basically the more g that was pulled the harder the elevators became to move. As far as I know it had nothing to do with any instability.

Thanks, winny. That is now pretty clear to me. Wouldn't have made sense to put weights to the tail in order to improve stability. It would just worsen it.

Yeah, it was only a small weight, 3.5 or 6.5 lb, depending on which wing was fitted, the lighter was for browning wing heavier for cannon wing, added to the actual control cables. It was about 3 quarters of the way down the fuselage.

"The stall warning possessed by the Spitfire was especially beneficial in allowing the Pilot to reach maximum lift coefficients in accelerated maneuvers. Because of the neutral static stability of this airplane, the pilot obtained no indication of the lift coefficient from the motion of the control stick, nevertheless, he was able to pull rapidly to maximum lift coefficient in a turn without danger of inadvertent stalling...."

A nice feature in a fighter !

If the Spitfire was such a terrible a/c, at least according to Eugene, why did the USAAF accept them for service?

You might find the following information useful....

Gilruth's developed the concept of stick force per G, control movement measurement, and pretty much wrote the standards of measurement for stability and control as used by the NACA.

Only two nations in the world had stability and control standards during World War II, the United States and Germany.

The NACA's measurement and classification system developed by Gilruth was not published until 1941 and was classified. It was not released to Allied Nations until 1943.

Even Gates, a very prominent RAE researcher who pioneered stability and control standards for the RAE was not privy to them during his 1942 "dash around America" tour of the United States research facilities. Gates was the one who defined Aerodynamic Center, stability margin, and maneuver points during his lifetime. He had a passion for stability and control and published some 130 papers before his death. Before him, the neutral point was termed the metacentric ratio.

Unfortunately, nobody at the RAE paid much attention to Gates and it was not until post war that the United Kingdom adopted any defined standards of what is acceptable and what is not in terms of stability and control. When they did, it was a mirror of Gilruths work at the NACA.

So, by what standard is the RAE refuting the NACA? The answer is really none. The RAE had no defined standards of stability and control except subjective opinion.

Still doesn't prove the Spitfire was a dangerous aircraft to fly; apart from that I'd like to see Crumpp provide some documentary evidence that Spitfires regularly broke up in flight during spin recovery.

;)

I didn't say any of the parts in bold, which you claim to be quoting from me.

First of all, let's get what I said correct. Feel free to point out where I make any reference to "regularly". That is your own pointy tin foil hat theory.

I said it could happen to the Spitfire. The Operating Notes clearly warn the pilot of the hazardous longitudinal stability characteristics.


http://img546.imageshack.us/img546/8...ramedamage.jpg

http://img209.imageshack.us/img209/9...amedamage2.jpg

Right, I did the bold.

Quote from page 46 of a book by Morgan & Shacklady taken from this discussion:

http://forum.keypublishing.com/showthread.php?t=75816


The Air Ministry was not completely satisfied with the spin recovery of the Spitfire, and at a meeting on 17 January 1938, chaired by Air Cdr. Verney, Supermarine persuaded those in attendance that no modifications be made to production aircraft apart from the addition of an anti-spin parachute. For the Air Ministry Verney said that based upon model tests at Farnborough production aircraft could not be passed for spinning even with a tail parachute. Supermarine then pointed out that Jeffrey Quill had made sixteen successful spins of eight turns in the prototype. After more discussion the DTD agreed to accept the Supermarine proposal and that the first 20 production models should be fitted with the tail parachute and undergo further spinning trials. He, DTD, would be satisfied with recovery at 15,000 ft. When the first production Mk 1 Spitfire, K9787, was completed at the beginning of May 1938 an anti-spin parachute was duly fitted and the aircraft made its first flight from Eastleigh, piloted by Quill, on 14th of the same month .

The DC-3 also had longitudinal stability and control issues. The fact both the Spitfire and DC-3 had long careers is not an excuse to dismiss flying quality requirements. It is perfectly reasonable to assume that both of these fine airplanes would have been even better had they been more longitudinally stable under all flight conditions. Nobody has ever run definitive, statistically valid experiments on the value of good flying qualities in terms of accident reduction or military success. Common sense prevails and the entire world has since adopted stability and control standards to reduce accidents and increase air to air combat effectiveness.

http://img99.imageshack.us/img99/584...sopenstall.jpg

In that case, maybe you can next time avoid putting your words in my mouth by using proper formatting.

On the contents you added, I won't disagree with what you've said regarding the stick fixed and stick free stability testing, as it is absolutely right. You should, however, keep in mind that I try to explain things in a way that the concept can be understood by anyone interested, not just those with a suitable education or years of experience in the field. In my opinion, it is easier to understand "no trim change with constant elevator when speed changes" than to understand a description of an initial reaction to displacement.

However, I disagree with, because NACA says:
regarding dynamic stability:and regarding neutral or negative stability which they recorded:
.
To sum it up, NACA did not record long period oscillations for the Spitfire and the assessment of neutral or negative stability was made for static longitudinal stability.

Your words. It is my understanding that this is exactly what NACA assessed and what they found to be neutral or unstable, only that they used a different method for testing.
NACA didn't have a problem with (short period) oscillations over time, the Spitfire would dampen any (short period) oscillations within a cycle or two.
NACA did have a problem with the fact that a bit of extra elevator at any speed, if not reduced, would change the AoA for good, meaning the plane would not come back to a more level attitude even when speed was reduced.

Looking at the easy to understand diagrams CaptainDoggles linked, neutral static stability appears to be exactly the problem NACA had with the Spitfire.

I see you deleted your last post, but it might still help if I leave this one up to make sure we all use the same terminology.

They are talking about static stability. Wow, shows you how much things have changed and how new stability and control was as a science during WWII.

Static instability is horrible in an airplane. Seriously...the FAA and ICAO would send you back to the drawing board if you were seeking certification.

http://www.law.cornell.edu/cfr/text/14/23.173

Poor choice of words on my part. Long period Oscillation has specific meaning and it should read:

The longitudinal dynamic stability (Oscillations over time) was neutral or negative as recorded by the NACA.

Good diagrams and I have some others that will make it clearer for you all.

That diagram would make you think the elevator is held constant but it is not.

Keep in mind when that report was written there were not any standards of the day. It is not like testing processes or airworthiness. It was a very new science that was not covered in convention. In the 1980's there was even a "counter-revolution" in stability and control engineering.

As I understand and from RAE papers the installations of bob weights to the elevator and longitudal instability were related. To my best understanding - and do correct me if I am wrong - instability means that if you pull the controls (in whatever direction), the aircraft will not only change its roll/pitch/yaw to the extent of control movement, but also keep increasing it on its own, as if there were some kind of inertia/acceleration going on. This was noted on Spitfire Vs by the British.

By adding the bob weights and making the controls progressively harder to move for greater deflections, it made this increased acceleration problem more difficult to encounter.. It did not cure the instability itself, which was an inherent aerodynamic feature of the design, but made it harder for the pilot to make it happen.

Its interesting to note that the Bf 109 won the fighter tender against its Heinkel rival due to the excellent spinning and stability characteristics much desired by the Imperial Air Ministry. Green notes, that the Commission ultimately ruled in favour of the Bf 109 because of the Messerschmitt test pilot's demonstration of the 109's capabilities during a series of spins, dives, flick rolls and tight turns, throughout which the pilot was in complete control of the aircraft.

while not strictly related to the spit/109 debate, the fitting of elevator bob weights wasn't unique

http://p51h.home.comcast.net/~p51h/sig/TO/01-60-90.pdf

Stability and Control issues were not unique in WWII era aircraft. The science was very young and there were no standards in place. Most if not all of them had some sort of issue.

It is the area WWII fighters show the most variation in performance and is just as important to their fighting abilities as the aerodynamics.

Germany was the only combatant to have standards when the war started. The United States had standards by the time it entered the war as well. Everyone else did not adopt any defined standards until after the war.