XP-39 and the Claims

XBe02Drvr · Mar 9, 2021

P-39 Expert said:
How can stall characteristics be good if there is no stall warning? Seems like if this is as critical as you say, then the stall characteristics should have been labeled "deadly" or "catastrophically bad" or something along those lines.

DerAdlerIstGelandet said:
And an aircrafts characteristics regarding the warning leading up to the stall are part of whether it has good or poor stall characteristics. An aircraft that gives you no warning at all is not really ideal.

Koopernic said:
Test pilots often refer to characteristics such as 'stall annunciation' and departure characteristics.

For "everyday Joes" like us, Adler's got it right, but in the rarefied world of aerodynamicists and test pilots (who write performance reports, BTW), it's more like Koopernic says, incipient stall warning and behavior in the stall are two separate topics, to be explored and reported separately.
PS: Any test pilot worth his salt is going to be a very precise flyer who's going to fly through every stall with perfect aileron-rudder coordination, thus not provoking the beast to display its nasties. It's what they do. If he happens to do a "sloppy" stall entry and experiences unpleasantness, and his boss is trying to sell airplanes, or trying to justify buying them, do you think he's likely to make an official big deal over it? Not if he wants to keep his job, and in the case of a civilian, his draft deferment. The infantry is always insatiable for bodies. He'll probably settle for planting a bug in the ears of the folks in the test and development shop.

XBe02Drvr · Mar 10, 2021

Koopernic said:
Test pilots often refer to characteristics such as 'stall annunciation' and 'departure characteristics'. There were differences in the stall when at low speed and not under high G and under high G where aeroelastic characteristics came in

The more G there is on the aircraft at the stall break, the more critical symmetry becomes, and the less tolerance there is for any slipping or skidding. Many factors affect the pilot's ability to control this. Short tail planes like the P39 often have a deficit in rudder authority at high AoAs, and if they also have a short nose, the visual cues regarding rudder-aileron coordination can be frustratingly subtle. I remember several frustrating stall lessons with a student in his AA1 Yankee (the production version of Jim Bede's BD1). That little roller skate would snap into an incipient spin if coordination wasn't PERFECT, and yaw was very hard to see with its wide, short nose. It took my student a while to master it, but he got really good at spin avoidance. OTOH, the Cherokee 6, with its humungous schnozolla and equally long tail, was a dream to fly through any type of stall you wanted. A regular rocking chair. The Cessnas, from the 150 to the 210, all behaved pretty similarly in stalls, just with varying control pressures and muscle required. Solid, reliable, predictable. Likewise, Beechcraft singles, except the T34, which, with it's short, down sloping nose, required a lot of attention to get a zero yaw stall. It was kind of fun to deliberately stall her out of a high G turn, just to go for the ride. She would wind up pretty quick. Ah, the days of young and foolish!

P-39 Expert · Mar 10, 2021

P-39 stall characteristics were good but had little to no warning. Recovery was immediate with forward stick pressure in any configuration. The rest is just noise.

DerAdlerIstGelandet · Mar 10, 2021

SMH...

DerAdlerIstGelandet · Mar 10, 2021

Just noise...

I'm done with this. If I was not a moderator I would put someone on ignore.

Glider · Mar 10, 2021

P-39 Expert said:
P-39 stall characteristics were good but had little to no warning. Recovery was immediate with forward stick pressure in any configuration. The rest is just noise.

I know I am saying something that has already been said but the phrase' P-39 stall characteristics were good but had little to no warning' is a total contradiction in terms.

As an example, a 'little or no warning stall' on the approach to land will certainly result in a lot of noise. An aircraft hitting the ground, sirens from the ambulances and fire trucks do I agree make a lot of noise. It certainly doesn't make the description 'Stall characteristics were good' even close to accurate.

You seem to have missed the tendency of the P39 to go into a flat spin from your description as 'Stall characteristics were good'

FLYBOYJ · Mar 10, 2021

P-39 Expert said:
P-39 stall characteristics were good but had little to no warning. Recovery was immediate with forward stick pressure in any configuration. The rest is just noise.

Power on, gear and flaps up? I don't think so! It's quite evident you're just reading things (and mimicking) you fully don't understand!

pbehn · Mar 10, 2021

P-39 Expert said:
P-39 stall characteristics were good but had little to no warning. Recovery was immediate with forward stick pressure in any configuration. The rest is just noise.

Do you read or only remember that which suits you? If your plane stalls in a high G turn without warning, will it recover with some forward stick pressure? There is a discussion of the Fw 190 Spitfire and P-51 aerodynamics posted on the forum. The Fw-190 was a great plane to fly in 1 G conditions, giving warning of a stall and being easily recoverable, in high G power on turns it would stall and tumble without warning in spectacular fashion, the top pilots used to practice doing it and used it as an escape gambit, if they had the altitude. In USA hands the P-39 was mainly used as an advanced trainer, the requirements of a trainer are different to a combat aircraft, you have to train people to fly without killing them in the process.

glennasher · Mar 10, 2021

DerAdlerIstGelandet said:
Just noise...

I'm done with this. If I was not a moderator I would put someone on ignore.

I had to do just that, to keep my blood pressure within a safe range. It also keeps me from getting an aural hematoma from SMH like an old hound dog.

P-39 Expert · Mar 10, 2021

FLYBOYJ said:
Power on, gear and flaps up? I don't think so! It's quite evident you're just reading things (and mimicking) you fully don't understand!

Thank you for telling me yet again that I don't understand something. I believe I do understand exactly what I am talking about.

"Stalling characteristics are good, but there is little or no stall warning" is from virtually every description of P-39 stall characteristics. If the lack of stall warning is that serious, then stalling characteristics cannot be labeled as "good."

"In any condition, at any time after the stall occurred, recovery could be effected promptly by applying down elevator" is straight from "Measurements of the Flying Qualities of a Bell P-39D-1 Airplane (AAF No.41-28378)" from wwiiaircraftperformance.org.

Sorry this is not what you want to hear, but those are the facts.

pbehn · Mar 10, 2021

P-39 Expert said:
Thank you for telling me yet again that I don't understand something. I believe I do understand exactly what I am talking about.

"Stalling characteristics are good, but there is little or no stall warning" is from virtually every description of P-39 stall characteristics. If the lack of stall warning is that serious, then stalling characteristics cannot be labeled as "good."

"In any condition, at any time after the stall occurred, recovery could be effected promptly by applying down elevator" is straight from "Measurements of the Flying Qualities of a Bell P-39D-1 Airplane (AAF No.41-28378)" from wwiiaircraftperformance.org.

Sorry this is not what you want to hear, but those are the facts.

This means not good, and was one of many reasons the Supermarine Spiteful was shelved.

Glider · Mar 10, 2021

P-39 Expert said:
Thank you for telling me yet again that I don't understand something. I believe I do understand exactly what I am talking about.

"Stalling characteristics are good, but there is little or no stall warning" is from virtually every description of P-39 stall characteristics. If the lack of stall warning is that serious, then stalling characteristics cannot be labeled as "good."

"In any condition, at any time after the stall occurred, recovery could be effected promptly by applying down elevator" is straight from "Measurements of the Flying Qualities of a Bell P-39D-1 Airplane (AAF No.41-28378)" from wwiiaircraftperformance.org.

Sorry this is not what you want to hear, but those are the facts.

Sorry but clearly you are being very judicious in the examples you give. Even the quote you use is being interpreted selectively. Note the Line after the stall occurred. To use my example you are already dead because you had little or no warning of the stall. If you have altitude you may (note may, see next point) survive but without warning you are dead.

Point 2 . Please read the spinning test results also on the same site the following are the conclusions

Subject: Report of Spin Tests
Section: Flight
Serial No: ENG-47-1779-A

Conclusions
1. The P-39 should not be spun intentionally under any circumstances.
2. The P-39 should not be snap rolled as the roll usually ends in a spin.
3. The best spin recovery is to simultaneously apply opposite rudder and neutralize the stick.
4. Power should be cut immediately if a power on spin is entered.
5. Care must be excercised during the recovery to prevent an accelerated stall and re-enty into the spin.
6. The wing tip spin chute does not aid recovery of the P-39Q from a flat spin.

DerAdlerIstGelandet · Mar 10, 2021

My recommendation? Everyone just walk away...

GrauGeist · Mar 10, 2021

P-39 Expert said:
Sorry this is not what you want to hear, but those are the facts

There are quite a few people here who have a considerable amount of flight experience (far beyond my time logged and in far more advanced types) who are trying to explain the difference between reading about stall characteristics and actually living through it.

We get that you're a proponent of the P-39 and that's fine, but no matter how you interpret the data will not change it's legacy.

Just a suggestion: go to your local airfield and see if a flight instructor would take you up up for a ride and show you some stalls.
Keep in mind that if they do, these will be done at a safe altitude AGL and not in combat situations, and they'll be done with a predictable recovery routine BUT will be an eye opening experience.

FLYBOYJ · Mar 10, 2021

P-39 Expert said:
Thank you for telling me yet again that I don't understand something. I believe I do understand exactly what I am talking about.

"Stalling characteristics are good, but there is little or no stall warning" is from virtually every description of P-39 stall characteristics. If the lack of stall warning is that serious, then stalling characteristics cannot be labeled as "good."

"In any condition, at any time after the stall occurred, recovery could be effected promptly by applying down elevator" is straight from "Measurements of the Flying Qualities of a Bell P-39D-1 Airplane (AAF No.41-28378)" from wwiiaircraftperformance.org.

Sorry this is not what you want to hear, but those are the facts.

If you did understand what you were talking about you would mention that stall recovery doesn't only consist of "pushing the stick forward." Again, you're just mimicking what you want to out of the flight manual.

So maybe now YOU will listen and understand that there are actually SEVERAL types of stalls and configurations - but you knew that, right?

XBe02Drvr · Mar 10, 2021

FLYBOYJ said:
If you did understand what you were talking about you would mention that stall recovery doesn't only consist of "pushing the stick forward." Again, you're just mimicking what you want to out of the flight manual.

So maybe now YOU will listen and understand that there are actually SEVERAL types of stalls and configurations - but you knew that, right?

If this old carcass was still airworthy, and there was a T34 or similar aircraft available, X-spurt and I would go up and experience a few things that have heretofore been only paper exercises. Just make sure he's got a helmet and chute on and he took his Dramamine.

FLYBOYJ · Mar 10, 2021

This is from a P-39Q Flight Manual - some observations;

The stall information shown is basically for a power-off stall gear up flaps down (Vs1). This is probably the most benign configuration and can be accomplished in straight and level flight. No mention of other stall configurations. I wonder why there is a caution note under spins!

P-39 Expert · Mar 10, 2021

We're talking about stalls, not spins. To spin a plane has to stall first. Spinning was prohibited in almost every AAF fighter flight manual.

"In any condition" means clean, gear and flaps down and any combination thereof.

"At any time after the stall occurred" means just that.

"Recovery could be effected promptly by applying down elevator." Straight from an official test. Hard to argue with that, but know some of you will.

P-39 Expert · Mar 10, 2021

Glider said:
Sorry but clearly you are being very judicious in the examples you give. Even the quote you use is being interpreted selectively. Note the Line after the stall occurred. To use my example you are already dead because you had little or no warning of the stall. If you have altitude you may (note may, see next point) survive but without warning you are dead. How can I be judicious by quoting the exact line from the report? Recovery was just that easy.

Point 2 . Please read the spinning test results also on the same site the following are the conclusions

Subject: Report of Spin Tests
Section: Flight
Serial No: ENG-47-1779-A

Conclusions
1. The P-39 should not be spun intentionally under any circumstances. We are talking about stalls, not spins.
2. The P-39 should not be snap rolled as the roll usually ends in a spin.
3. The best spin recovery is to simultaneously apply opposite rudder and neutralize the stick.
4. Power should be cut immediately if a power on spin is entered.
5. Care must be excercised during the recovery to prevent an accelerated stall and re-enty into the spin.
6. The wing tip spin chute does not aid recovery of the P-39Q from a flat spin.

Please see above.

XBe02Drvr · Mar 10, 2021

Glider said:
As an example, a 'little or no warning stall' on the approach to land will certainly result in a lot of noise. An aircraft hitting the ground

...doesn't make all that much noise; just a sort of a "whump" (unless you're real close to ground zero). I've heard that sound five times, which is five times too many. One time, I even mistook it for the closing of the baggage door on a nearby Twin Otter.

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