XP-39 and the Claims

[fubar57]

 

[pbehn]

I have a better idea, lengthen the nose, move the (Merlin) engine into it, square off the wings and tail, add a four bladed prop, stick the radiator in the belly behind the pilot and add 12 numbers to the designation.

My idea would be to take the engine out then go to the pub for a beer.

 

[Thumpalumpacus]

Jeezly Crow, more groundhogs!

 

[DerAdlerIstGelandet]

 

[glennasher]

My idea would be to take the engine out then go to the pub for a beer.

Take that Allison out and put it in a hydroplane and call it good. Then take the aluminum from the rest of the aircraft and send it to a foundry to make ANY other aircraft, wiping it out of our memories forever. Maybe then we'd get some peace from this monster that keeps cropping up and abusing this fine forum.

 

[GregP]

Hi glennasher! Altogether a capital idea, old boy. Make mine a Spitfire Ale.

I say, we seem to out of Spitfire! Bollocks.

 

[XBe02Drvr]

I have a better idea, lengthen the nose, move the (Merlin) engine into it, square off the wings and tail, add a four bladed prop, stick the radiator in the belly behind the pilot and add 12 numbers to the designation.

Hey, you forgot the laminar flow positive G airfoil!

 

[GregP]

Is that flow laminar into or out of the beer glass?

 

[XBe02Drvr]

Is that flow laminar into or out of the beer glass?

View attachment 615473

Down the hatch! Minimum boundary layer turbulence. Maximum flow.

 

[buffnut453]

Since we're on a Spitfire Ale kick:

 

[GregP]

Thank God there's no Airacobra Ale! But Spitfire Ale, we got some of that.

And Messerschmitt Schnapps, too!

And maybe:

And last:

SOmehow, these seem to go together ... likely not strictly per the tech order, but seemingly related.

 

[XBe02Drvr]

Thank God there's no Airacobra Ale! But Spitfire Ale, we got some of that.

And Messerschmitt Schnapps, too!


View attachment 615477

What about Wulfbrau?

 

[Peter Gunn]

Hey, you forgot the laminar flow positive G airfoil!

So typical of me, well, that's what happenzzzz afferr tooo mujch aleeelea... lallaall... aaaeelll... BEER.

 

[GregP]

 

[P-39 Expert]

Not maintained; improved!! It seems most P39s in combat trim, or even in training command, were flying around with CG at or near the aft limit, which may have itself been not conservative enough. A more forward CG increases the pitch-down tendency in a Departure From Controlled Flight (DFCF), reducing the probability of a flat spin. Given the concentration of mass in the core and the lack of polar inertia (a deliberate attempt to improve maneuverability), the impetus needed to get rotation started in a stall situation was pretty low. Add to that the easily blanked rudder and elevator configuration and you've got a potential booby trap for the inept or unwary pilot. Intuitive fliers like Yeager or Brown would naturally fly through a stall with precise coordination, thus avoiding yawing into the asymmetric stall condition that sets up a spin. Eagles of that caliber would of course enjoy the very light stick force gradients and the light "feel" of the plane, and would have the finesse to not overcontrol it as a more ham-handed pilot would.
So get that CG forward, if you can, and make it a better flying machine!

All the sources say that P-39 stalling characteristics were good, yet in the same sentence say that there was little or no stall warning. 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.

 

[pbehn]

All the sources say that P-39 stalling characteristics were good, yet in the same sentence say that there was little or no stall warning. 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.

As I understand it all aircraft stall, some give better warning than others, when close to stall some are still very controllable others very vague, when stall some are easy to recover and behave in a benign predictable way, others are not and become very dangerous very quickly.

 

[DerAdlerIstGelandet]

As I understand it all aircraft stall, some give better warning than others, when close to stall some are still very controllable others very vague, when stall some are easy to recover and behave in a benign predictable way, others are not and become very dangerous very quickly.

And an aircraft's 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.

 

[nuuumannn]

Whilst on a theme, we have this...

 

[GrauGeist]

There's a few breweries out there that have a Ju87 line. One is a Pilsner, one a Hefeweizen.

There is also this beer:

 

[Koopernic]

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.

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 and wings might be untwisting. There was power on and power off stall. The Me 109 may not have been able to out turn a spitfire (maybe for a fraction of a turn its been argued) but it did have outstanding stall and spin recovery. Some aircraft flipped inverted and into a spin when they stalled others just mushed.

In the case of the Me 109 its good stall spin characteristics came from a long tail moment arm. Although the Me 109 is often described as having an NACA 4 digit wing this is not quite true. Messerschmitt used the NACA polynomial descriptor for the wing but also made use the modification system German aerodynamicist had developed (2R1) This was developed to give good pitching characteristics. Professor Messerschmitt's fame rests on techniques he developed to create such pitching characteristics.

An issue the P39 would need to have contended with was its tail moment arm and also the distribution of mass relative to the tail moment arm. Centre of Gravity are not all the same. The weight can be concentrated around the pitching axis of the wing but one could have a 'dumbbell' like distribution (extreme case Dornier Do 335) in which case the moment of inertial would be greater and something called inertia coupling could occur.

I think the P-39 suffered slightly from its mass distribution relative to its tail moment arm length. It does however look like the principle drag axis and the thrust axis probably align which means there would have been minimal pitch changes when power was adjusted.