MW-50 Bf 109s Vs Fw 190 A

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Siegfried said:
My impression is that the Luftwaffe lagged around 6-9 months in engine development from early 1943 untill mid to late 1944 when it rapidly caught up. This can perhaps be attributed to fuel issues as much as anything else.
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Why fuel issues?
 

Not surprisingly you forgot to mention that Spit LF IX outclimbed 190A-5 with wide marking from SL upwards and at low down the low level Spit XII also outclimbed contemporary A-5. Also during the later part of 43 Spitfires at last got upper hand in combat against Jagdwaffe.

In engines I agree, DB605A let the early 109Gs down up to and incl G-6, only with G-6/AS, G-10 and G-14 (G-6 with MW50) Germans redress the balance. It wasn't only a fuel question, there were foaming of the oil (the main problem) and spark plug problems too.

Juha
 

Spitifre IX was only faster between 7000ft and 14000ft, it was then slower, but faster again above 22,000ft. Below 7000ft the Spitfire IX at 18psig was much slower. In climb rate the IX, but only on 18psig, was a significantly faster climber. However the FW 190 was about the same as the P-47, P-51A, P-38 iand Typhoon climbe at the same time period. It leaves the typhoon behined at about 16000ft. The Spitifre IX was an exceptionally fast climbing aircraft along with the Me 109.

22,000ft is the point at which the FW 190's performance begins of drop off, but below that it performs well, and at low altitudes it is often superior. The Spitifre XII (griffon) scraficed so much for its marginal advantage at low alttidue it was ineffective at even modest altitides. Later FW 190s had the critical altitude at around 25,000-27,000ft and so did much better than 22,000ft.

The stuggle for performance in the DB601 was mainly related to knock control, high octane fuel reduces stresses on pistons, reduces thermal load on the cylinder, allows greater boost, alleviates spark plug issues. Whatever the limitations of the DB601 these stresses would have been alleviated by higher grade fuel.

A new generation of FW 190A with more powerfull engines was comming out at the end of 1944.
 
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Mr Juha
Alleis had the luxury to built specialized sub models to cover weaknesses of their standard fighters.
In later 43 Jagdwaffe was fighting Soviets in the east, and americans in the west . With american heavies taking the full attention of luftwaffe Spitfires had much better opportunities . Read the Jg26 mission profiles in late 43 and compare it with 1942.But i agree from late 43 Fw was less competitive.
Mr Siegfried
Bmw 801 altitude performance was inadequate , thats very clear from every witness and thas way Dora was born
Mr GreqP
Your statement that Spits V and IX had twice the RoC of Fw seems inaccurate according to my bibliografy

Fw 190A8/9 were not totaly obselete in 44/45. They had great rate of rall, good sustained rate of turn at middle speeds which became better with the wide blade propellers of late 44, decent but not great performance below 20000ft. A good pilot could use the strong points of the aircraft to survive. But it was clearly lacking speed in comparison to the competition and AT THE SAME TIME had very high wing loading. Thats not a good reciepe for an air superiority fighter. The simple one stage two speed supercharger was a further a disadvantage. Fw in 44 could not force or escape combat using speed. If had high energy entering a fight could use his ailerons to good effect. But when energy was lost what options a pilot could have against Spit XIV, Tempest, P51 ,? Run ,accelarate, climb,dive, turn? Bf 109K4 G10 (if properly built) could out climb, out accelarate,and run . Late Fws (A6/7/8/9,D9) were FAR too heavy
As for the pilots memories are very valuable but often controversial: Hartmann ,Obleser,Rosmann of Jg52 were avoiding dogfights prefering boom and zoom tactics, while Lipfert,Dutmann and others of the very same Jg52 were hard core dogfighters. Galland was complaining about the turning of 109 yet Marseille was turning with everything. There are alleid references that say Fw s more dangerous opponents over Europe yet Fredric Arnold of 71st FS over northern Africa describes the 109s as morre agressive and dangerous. German pilots were trained from the early stages of their carreers not to orizontally fight Spitfires yet when posted to operational units found with surprise that experienced pilots (eg W-F Galland,Erwin Leykaf) did engange in orizontal turning ,often succesfuly. So what conclusion can be made base only on pilots memories? Of course using numbers can also hide the truth ( as varius anlosaxons site do)
 

? This is a post war Johnny Johnson press article I posted many times before... I don't think your accusation of fraud has anything to stand on just because I saved it to my photobucket account...


The Mk V being better by a hair is exactly what I would expect given they are said to be close: Despite a much larger power increase than wingloading increase, the Mk IX was said to be roughly equal in turn to a Mk V, however I would tend to givve the edge to the aircraft with the shorter nose...

GregP said:
Your quote from the Hurricane pilot is an Error 404 for me - page not found.....
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They do say they changed the adress in it: That is where it's from anyway, and the text is copy/paste unedited... You will note he says "The Spitfire has a heavier wingloading" which is his observed experience, but very far from the raw numbers... I'll go with this guy's experience of the issue rather than the theory... It helps I have a theory that accounts for the discrepancy...

GregP said:
Gaston, All pilots like the fighter they flew in combat ... because they flew it long enough to get to know it, it's strengths and weaknesses, and survived......
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Then why don't you look at the strength and weaknesses they actually mention?

The startling thing is that, aside from a few closely matched Tsagi numbers (which are ridiculous concerning the P-47 being at 27 seconds when the Germans themselves recognized the P-47D out-turned their Me-109Gs at 21 second) and ONE mention of the Me-109 out-turning the FW-190A in a captured La-5 evaluation (and another very high altitude evaluation at 27 000 ft. being irrelevant), there is virtually NOTHING in all of WWII accounts that actually states the Me-109 out-turned the FW-190A...

Perhaps that bears being at least noticed?


I no longer use the "column" notion since you quite rightly pointed out it was the void ahead of the blades that mattered...

Since you work at or are associated with "Planes of Fame", let me ask you this: Are any of the aircraft you have in the collection equipped with a wing strain gauge?

I am afraid, from what I found out so far, not many warbirds, if any, are equipped with a wing strain gauge, or else it would have been easier to realize there is something wrong with basic flight physics for these powerful nose-driven low-wing types: For instance, in horizontal turns (but not dive pull-outs), you would have found 3G horizontal turns at a lower power level cause less wing flexing than at a higher power level for the same 3G horizontal turn...

Remember that in WWII they apparently had no G meters, so they could not correlate what the wing strain gauge would tell them to a given level of Gs...

If you know where to find wing strain gauge data correlated with horizontal turns on WWII fighters, I would love to see what that data says when you vary the power levels...

I know damn well that with a hugely greater wingloading there is no way the FW-190A will out-turn a Spitfire Mk V, yet that is what is observable in combat, and there is nothing you can do about it: I have yet to see a single multiple turn combat showing otherwise...

If it is impossible for the FW-190A to out-turn the Spitfire Mk V with a higher wingloading, then there is something wrong in the way we assume the wingloading is tabulated in our formulas compared to what the real aircraft actually perceives: If you did the wing bending comparison with a wing strain gauge, you would find the FW-190A's wings are under less loading than the Spitfire's wings in actual turning flight...

The turn test with the wing strain gauge data at various power levels would be very easy to carry out with just one aircraft: In theory, a 3 G turn at full power or at 70% power makes no difference to the wingload as long as the turn's G load is the same: If a large difference showed up you would know the flight physics are wrong for these types of aircrafts (and I am pretty sure they are)...

If the flight physics are wrong for that (regarding the power level being irrelevant to wingloading), then you know they are wrong for other things: The FW-190A and Spitfire did not load their wings in the same way, and that relates to the source of the power and the leverages and shapes involved...

The problem with current assumptions is they assume the world works according to what our math tells it to do: It is the world telling the math what it is calculating, not the math telling the world what it is doing...

If you could get an in-flight wing strain gauge turning test done, you would know what I am talking about.

Gaston
 
Hi Siegfried,

Just getting back to the thread ... a lot of traffic today! Huh?

I think it is correct to say the BMW 801 was not a good performer at altitude becuase the European war was largely fought at 25,000 - 35,000 feet and the Fw 190 radial model performance started to decline at 20,000 feet and was pretty much gone by 25,000.

If you look at the archive of M. Williams, he has several Air Ministry technical reports on many aircraft. Among them is the Fw 190A-3 Technical Report #7908. In the report, the gross weight at takeoff is given as 8580 pounds with 203 square feet of wing area for a wing loading of 42.3 pounds per square foot. Net wing area is 177 square feet. Aspect ratio is 5.87.

The air craft was flown at the 3-minute engine rating and they got 304 mph at sea level, 325 mph at 11,000 feet, 375 mph at 18,000 feet, and 351 mph at 25,000 feet. Full throttle height in M blower was 4,500 feet and full throttle height in S blower was 18,000 feet. Speeds are TAS.

Max climb rate in M blower was at 4,000 feet at 3050 feet per minute and in S blower at 17,500 feet at 3280 feet per minute in the 3-minute rating. The 30-minute rating climbs were 2760 and 2750 feet per minute respectively. Climb speeds started at about 130 mph and went up from there. At high altitude, max climb speed was above 260 mph, which was closing in on max speed as the aircraft went up (like in all WWII fighters).

Max boost was 4.5 psi at 2,450 rpm.

Rate of climb starts to drop off rapidly at 17,500 feet. Sea level speed was 304 mph and rises to a max of 325 mph in M blower and tapers off until switching to S blower at about 11,000 feet at 330 mph or so. Speed build up tp 375 mph or so at 17,500 feet or so, where it tapers off rapidly. These speeds are at the 3-minute rating. In the 30-minute rating power, the max speed was down from 375 mph to about 355 mph at 17,500 feet.

The heavy wing loading was mention, along with smooth, well-harmonized controls. This technical report is located at http://www.wwiiaircraftperformance.org/fw190/fw-190-rep234.pdf . Other reports say the same thing, which is exactly what I said. Performance was good but not spectacular and tended to fall off above 20,000 feet ... which goes a long way to explaing why a B-29 would have an easy time with the radial engine Fw 190A models ... as I said earlier above. All tey had to do was get high and fast and the Fw 190A-3 would ahve a very difficult time catching the B-29 since the speed was only avaialbe at a 3-minute power rating. Otherwise, the top speed was about 10 - 15 mph faster than a Mistubishi Zero, which could not catch a B-29 under most circumstances unless ideally positioned at exactly the right time.

Now this is only one report, but there are many otehrs that say about the same thing, not just this one, including reports from the Lufwtaffe.
 
Hi Gaston,

Being an electrical engineer, I am very fmailiar with stain gages (not gauges). I used them as primary data acquisition for more than 10 years in my engineering career. They are simple and relaible. They are also not cheap to employ and, when used, are funded by a project under development with funding for dynamic load testing.

Our museum is a flying museum dedicated to preservation of WW2 (and other) milirtary warbirds in flying condition. We do not have any need to run strain tests since we certify, maintain, and fly to the published manufacturer's manual levels or less. That is, we fly within the operating envelope at all times and have a great safety record.

Let me put it to you this way. If you can afford the stain gages and assocauited electroncs, round up some, go get a friend with an RV-4/RV-6 to test it out for you. I already know what it will say, having flown g-meters in RC aircraft for several years and exploring level turns at verious degrees of bank. These RC planes had a higher power loading than ANY full-scale aircraft and could accelerate from zero to 150+ mph in less than 4 seconds/ I'm talking about a Quickie 500racer with a Nelson 40 up front. Top speed in the 190 mph range with wicked accelration, definitely higher acceleration than ANY jet aircraft. I got exactly what I ecxpected to get in my own tests, but feel free to eperiment. The g-meters in verious full-scale aerobatic aircraft I have flown say the same thing as I expect, too. You may find a G-meter is WAY less expensive, practially, than strain gages.

Actually, the strain gages are cheap. The associated instumentation amplifiers and other electronics as well as data recording systems are, while not expensive to an aerospace company in a developemnt effort, very expensive to ME, especially since I studied Physics and Aeronautics already, and so have little interest in re-proving what I already know. But, feel free to go for it. I suggest the friend with an RV as a very good starting place. Any competent RV pilot can do a 4.0 - 4.5 g loop or horizontal trun and you can record your data at various power settings. 4 g's is 4 g's. regardless of the power involved, and any vertical (pitch axis) 4-g acceleration (without rolling or yawing) will impart the same stress to the airframe. Any horizontal (yaw) 4 g stress will do the same, but it will be different from pitch stress.

I don't believe I ever got to a 4 g stress in the roll axis and I don't know anyone esle who did either ... unless it is some unknown F-104 pilot who tried to find the maximum roll rate of the Starfighter. If he did that, he probably ejected from the flat spin and tumble after 6 or more rolls ... it diverges at max deflection and gets very unstable. I believe the emergency checklist for that action terminates in "EJECT!"

Of course, about 75% of the F-104 emergency checklist terminates in "EJECT!" so that seems to be nothing unusual in the F-104.

Sorry Gaston, I don't believe your claims but, by all means, investigate on your own. If you are well instrumented, verified and have a current calibration, you'll get what everone else gets who has done aerodynamic testing. But, if you DO it, at least you'll have some fun doing it.
 
Thanks for the details Greg,

Unfortunately the data I would want could not be from an aircraft of less than 1000 hp and 5000-6000 pounds, and would have to be a low-wing monoplane with a single piston nose-traction engine... I doubt the effect is scaleable to anything else, even to a high wing monoplane of the same weight/power...

My theory is based on the migration of the Center of Lift due to prop assymetry resistance, which substitutes to the elevator's effort so that there seems to be no effort involved for the pilot in defeating the prop's inside turn assymetry resistance. It would not be surprising if such an effect was not scaleable: It could be the prop's resistance to turn assymetry manifests itself in a non-linear way: Ie, none below a certain power level, and suddenly a lot above a certain power level...

What I would like to find is where is the actual data for WWII aircrafts? Wing strain gage data for jets is of course irrelevant.

You would think wing bending data would exist somewhere for WWII types of aircrafts...

I have little doubt that some wing strain data does exist, but is it correlated to horizontal turn Gs and power output in horizontal turns? Since apparently no one knows that this is a problem, I wonder if the data would have been laboriously collected and correlated in this way for a non-existent issue? Especially since, at the time competitive combat turns on prop aircrafts mattered, there was apparently no G meter to correlate the turn data to an amount of wing bending...

So if you have wing bending data for WWII figher aircrafts, I would certainly like to see it, or know where I can find it.

As for the notion that you "know" what is going on here, sorry: Every year I find a dozen or so new accounts to the thousands I have already gathered, and every time a "new" one arrives it points in the opposite direction to the conventional wisdom (how do you like the "new" RCAF account of John Weir?): Anyone who thinks the Me-109G out-turns in sustained low-speed turns the P-47D, or that the Spitfire (any mark) out-turns in sustained low-speed turns the FW-190A is more than out to lunch: If they had genuinely tried to be less informed, they would not have succeeded...

Regardless, if you could find that wing bending data, I would be most grateful...

Gaston
 
First, a strain gage is a two-axis (shaped like a cross or an "X") piece of metal foil attached to a metal beam ... such as a wing spar. Each leg will slightly change resistance as it gets compressed or stretched in tension by bending of the beam (or wing). From this, the slight voltage differences from excitation can be amplified and the stress and starin can be calculated. It is basic materials science and is widely used in figuring stress and strain in aircraft structures.

Gaston, I sympathize with your need for a high horsepower, heavy aircraft to test. The museum will usually do this type of stuff ... but not for free. If you are willing to pay for it, it can probably be arranged. P-51 Mustangs go for about $1600 per hour or so and other planes are proportional to costs. A P-40 is less and a B-25 is probably in the neighborhood of $2,500 per hour or so.

The RV-6 can be flown for ... maybe ... $50 per hour, so I thought the cost differntial was worth the savings.

But, if not, then the only obstacle is money. For enough money, we'll repaint and fly any of our aircraft for films, etc. If you want to blow up a Merlin with full power runs, all you have to do is supply the replacement engine and we'll probabluy do it for the right price and the right to salvage the blown engine parts. The right price includes incentives for the museum and pilot's time and risk and well as any fees incurred for airspace reservation ... assuming the task is reasonable and both the museum and the pilot (and FAA) agree with that assessment.

So if you want to dive a P-47 vertically at full ppower for 20,000 feet from 35,000 feet, we have done that. It wasn't cheap for the party involved, but it was done. The results are known but are the property of the guy who paid for it. You could do the same if you want and you'd own the data along with the museum, if the contract reads that way. As far as I know, we ALWAYS have a right to data we produce or we don't produce it. But that could change with the money ...

Maybe the RV-6 is sounding better?

All I'm saying is that I don't know anybody who will instrument his warbird at his own expense and subject it to stress. They operate at book limits or less, and no owner wants to stress his aircraft beyond what is considered normal ... unless he has financial incentive to do that.

Good luck.

And any 28 lbs/sq ft aircaft will out-turn any 42 lbs/sq ft aircraft ... really. No bull. It's basic aerodynamics and assume broadly similar airfoils and moments, which ALL WWII fighers had. None were fielded with BAD airfoils and the single engine types had broadly similar moments of intertia about all axes (of course the twins were different from the singles). Without high-lift devices to overcome the basic wing loading difference (and the Fw 190 didn't have them) then the ligher wing loading fighter will out-turn the heavier wing loading fighter. That assumes competent design and both the Spitfire and the Fw 190 were very competent designs by two talented designers. Both aircraft were thoroughbreds and were very well designed, so there was none of the "idiot designer" stuff involved.

Sorry, the Fw 190A didn't out-turn a Spitfire V unless the Spit pilot didn't use his aircraft very well. I'm sure that happened, but not very often after the initial encounters. Until the avent of the Fw 190, the Spitfire pilots didn't have to extend their aircraft very hard in horizontal turn against the Me 109 (the 109's basically fought in teh vertical or they had problems with Spits). So, the early encounters with the Fw 190 were likely cases of lackluster response from the Spits due to not ever having to do anything else in the turn fight.

After a few shoot-downs, that changed really quickly and the Fw 190's were recognized and responses were altered accordingly. Look at combat record, say, after 2 months of Fw 190 vs. Spirfire combat and you won't find the Fw 190 out-turning the Spits since the Spit drivers were then aware of the threat and reacted accordingly.

Also, the Spitifre would EASILY outclimb a radial-powered Fw 190. Look at the power loading and the recorded rates of climb.

This isn't all that tough, Gaston, but we disagree here heavily. That isn't all that bad and I know I will not change your opinions. Likewise, mine are pretty solid and are rooted in real-life knowledge of real-life warbirds, including real-life radial-powered Fw 190's ... including Paul Allen's real-life, BMW 801-powered Fw 190. Our museum was involved in the test flying and the subsequent display flying from the first test flight to now. It is very good, but the Spitifres aren't in danger of being out-turned if the Spit driver is compentent and aware, then or now.

I'll look for the wing bending data in my free time as I am now intersted, but AFTER our May airshow in Chino. That is the full-time free-time occupation until after the first week in May. I'm working on one of our displays and helping with an engine change after overhaul.
 
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Well I am very glad to hear you are directly involved with warbirds, and that almost anything can be done for a price!

I won't be able to pay such money for now, but in a few years down the road this is not inconceivable: There would be no excessive G strain involved for the airframe as I need no values higher than 3.5 Gs in a full near 90° bank. I might ask full "normal" power if that is possible: Maximum continuous power. If near WEP is possible for one turn, at a price, then so much the better!

The main thing would be a variety of lower power levels at the same 3.5 G sustained turn rate... Right down to 50% power or whatever is possible at 3.5 Gs... The preferred aircraft would be the P-51 or later Merlin Spitfires, maybe even both!

Another interesting thing to test would be the use of full coarse prop pitch during slow speed turning on the P-51D: You remember the pilot account that made intricate references to this... At 20 000 ft. there should be enough room for safety...

I am surprised at how involved is the strain gage data gathering, as I would have thought it was a simple straight wire whose "shortening" under bending would be measured...

If it is more precise, then so much the better!

Since the P-51D is around 9000 lbs, and 3.5 Gs would be (in theory) 31 500 lbs on those wings, would it be possible to have a set of spare wings bent to 31 500 lbs to get a reference to the wing bending results in flight? I fear doing that to a flier would be unthinkable.... Are there spare P-51 wings around that could be used as a data reference point?

I am very glad I got you interested in finding wing bending data, as I am personally convinced that this could prove very valuable.

I'll await whatever you can come up with in your research!

Gaston
 

The actual strain gauge is a single axis device - but for most purposes using just a single axis isn't very useful. Often they will use two devices mounted at 90° (as you said), or 3 at 0°, 45° and 90°



As you can see from this picture, you need a channel for each strain gauge axis used.

btw, it's gauge pretty much everywhere except the USA.
 
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is not full true that 190 can not outurn a Spitfire, the wing load is not all, at some speed 190 can turn best of Spitfire (i read this time ago and now i don't remember if comparison was for a Spit V or a IX maybe a V)
 
Wayne,

Yes there are single axis strain gages available; we never used them in a single-axis mode. We always used two-axis strain gage mounts, or even 3-directions, since the cost differential was slight (we already had the equipment available) and and the off-axis data was always required. In fact, I forgot that you can actually use a strain gage in a single-axis mode since we never did it except in training (to reduce training costs). When I say the insttrumentation amps are expensive, the term is relative. You can get good instrumentation amps from the vendors for $1500 and the strain gages themselves are cheap, on the order of $50 each. So a full X-Y set of amplifiers and strain gages, cables, oscilloscopes, etc. can be had for uinder $10,000 and sometimes for half that if the data are not complex.

That is a cheap test for, say, Boeing. For me personally, I am simply not interested enough to lay out thousands of dollars of my money to satisfy my curiosity. I already DID that at work many times, but not with aircraft wings. My work was with explosive devices and the stresses involved, particularly abiabatic pressure rise inside a closed bomb to measure the energy produced by 1 gram of propellant, deflagrant, or other explosive media. I leave aircraft tests to the aircraft designers and they pass along the costs to the buyers. Part of the cost of every Cessna or F-22 is testing cost.


Gaston,

Two things.

First, spare P-51 wings are not available, but can be made. The spar is pretty simple and relatively low-cost compared with a complete wing. Fighter Rebuilders (Steve Hinton's business) can make you a complete P-51 wing spar, and can do it rather quickly. I think any bending data that are lying around for WWII fighters are static data from wartime research. Nobody destryos a P-51 today out of curiosity.

Two, I finally think I understand what you are trying to say when you talk of low-speed turn stress. See if I am right. You are thinking that if the aircraft is at a relatively low speed, say … 180 mph, and in a level, say … 4g turn, then the power in the engine must be increased and this, in turn, applies more stress to the airframe than a level, 4g turn at, say … 300 mph. Is that it? Also, the aileron on the downward-tending wing must be deflected more to keep at the correct bank angle, so the downward-tending wing incurs more stress than the upward-tending wing. Perhaps you are also thinking of maneuvering speed in a light aircraft, which is the maximum speed at which full and abrupt use of the controls is OK and will not overstress the aircraft.

Is that what you are trying to say?

First the structure of a fighter aircraft (or any aircraft, for that matter) is designed to be able to handle the stress of the aircraft sitting still on the runway witt the engine developing full power, or as close to it as possible, and the prop feathered, plus a safety factor of 1.5 or more; usually 2.0 or more. The reason the prop is feathered is that is one failure mode that should not cause airframe damage. After all, constant speed props DO fail.

Light aircraft have a placarded "maneuvering speed" which is not shown on the airspeed indicator, but IS a placard on the panel. In fighter aircraft, the maneuvering speed is commonly called the "corner velocity" or "corner speed," and it the top left cusp of the V-N diagram. Below the corner speed, the aircraft will stall if the g-available is exceeded. Above the corner speed, the aircraft is limited by structural strength and can be made to fail in the air if overstressed.

Gaston, the wing of a WWII fighter will withstand a certain g-load plus a safety factor. If the aircraft is slow and if the ailerons must be deflected more to compensate, the g-load on that wing simply increases. Below corner speed, if the g-load available is exceeded, the wing stalls and the aircraft spins (or comes VERY close to spinning due to asymmetric loading at the stall). Above corner speed, the pilot CAN fail the wing, but above corner speed the aircraft is not in a "low speed turn" and the situation does not apply.

All that happens at lower speeds is that the stall margin is degraded a bit and the pilot must not stall it, particularly at low altitudes. Many Me 109's and Fw 190's stalled at low altitude when trying to turn with or escape from a Yak-3 or La-5 / 7. You can find tales of this in Russian writings by pilots of WWII. Lest you think that is anti-German, many Allied pilots also spun in at low altitude trying to evade the Messerschmitt or Fw 190. The real issue is the speed at which the evading fighter is flying relative to the V-N diagram when the pilot attempts an abrupt maneuver.

In simple terms. If the aircraft gets slower, there is less margin before stall occurs. As the aircraft goes up in height, the stall speed increases. At absolute ceiling, the stall speed is just above the maximum speed at which the aircraft can fly in straight and level flight. Any higher (or any load) and the aircraft stalls and descends. It has little to do with stress and everything to do with aerodynamics.

Recall tales of the "coffin corner" in a Lear 23? At 49,000 feet in a Lear 23, Mach buffet was 2-3 knots above cruise and stall was about 2-3 knots below cruise. Get sloppy and you get into either a stall or Mach tuck. It happened, sometimes fatally. By the tme the lear 25 was flying, the margins were 15 - 18 knots and there was no more issue.

A 747 at Mach 0.86 at 35,00 feet has a very comfortable margin from cruise to either Mach buffet or stall.
 
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A big problem with trying to use anecdotally evidence as a "data base" is that some very big variables are not included.

By the time a fighter has been pulling a number of "G"s for more than a few seconds the pilot is greying out or blacking out. Turning at 4-6 "G"s is NOT a smooth steady turn. It is a succession of minor control inputs that tighten and loosen the turn that result in a 4-6"G" average. The more experienced the pilot the better he got at skating on the edge of blacking out, and relaxing pressure on the stick for a few seconds at a time to keep from blacking out.
Another thing is that NO fighter could sustain a high "G" turn for very long without loosing speed. As the speed falls off the same "G" turn tightens in radius.
Some planes had more control authority than others or, in other words, responded differently to the controls. Early Spitfires had overly sensitive elevators. It didn't take much to over control the plane and provoke a high speed stall.
Now you have a low time pilot, trying to turn tight, with 4-5 Gs trying to pull his arms down into his lap and afraid of over controlling and Stalling, and he is graying out, getting tunnel vision and loosing situational awareness. A more experienced enemy ace out turns him with a theoretically inferior turning plane. Not exactly a big surprise or a reason to throw out decades of aerodynamic knowledge.
 

Hello Jim
Now Spit LF IX wasn't pure low level fighter like LF V amd MK XII were, in fact it was faster than 190A-5 over 22000ft and PVO (Soviet Air Defence AF) used it as high altitude interceptor. British simply lowered the FTH for Merlin 66 to get its performance more suited for the combat enviroment of ETO. In fact LF IX became the standard Spitfire in ETO. We probably agreed that an extra difficulty for LW was that while in the East combats were fought mostly in low or medium altitudes in the West much of the combat were fought clearly higher up. Yes in 43 LW SE fighter performance was in stagnation but IMHO both 190 and 109 were still dangerous opponents. The technical superiority moved to and fro between Allied and Germans during the WWII.

Juha
 
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