SHOULD the P39 have been able to handle the Zero? Was it training or performance?

[Greyman]

In the interest of comparing like with like - range figures from British data sheets:

Though one difference is the P-39's figures all seem to be for 15,000 feet and the others for 20,000 feet.

 

[pbehn]

An interesting question - the shoot down occurred near Janville as 15 Stukas were caught sneaking in at dusk 100' off the deck.

The Area Patrol was between 10 and 15K and following RTB, dropped to the deck for strafing when the 357FS called the Ju-87s rallied the two squadrons in for the shoot. Went out in a direct line from Janville so nowhere near Normandy.

His first combat mission was at 0251 to 0851 on an Area Patrol just east of the Beachhead - dropping down to shoot stuff up behind German lines near Caen... so this one possible

Well my father certainly wouldn't have, you have a limited field of view in a destroyers boiler room, searching for U Boats on the edge of the fleet., my uncles job was actually to identify "friend or foe" to the ships gunners on a converted US "Liberty" flak ship. The gunners were straight from the USA with obviously no experience in identification. My uncle called out friend or foe and the US commander of gunners issued the order to fire. They only saw 10 minutes of "action" in the two weeks he was there, but that was very "hairy", he got a nice commendation from the captain.

 

[P-39 Expert]

What troubles me about those figures is the P-39s apparent extreme sensitivity to power and and weight.
The P-39Q used the same engine and prop as the P-39N and yet the addition of 557lbs knocked 500fpm off the climb at 15,000ft, 430 fpm off at 20,000 and 370fpm off at 25,000.
Also note that the P-63, although it had about 1000lbs more weight, may have had around 1300hp at 15,000ft and 1200hp at 20,000ft.

Those P-39N figures are in an official document but I suspect you would be very hard pressed to get them in the field.

The P-39Q was burdened with the gondola underwing guns which cost about 15mph top speed and affected climb/ceiling also. Basically the same plane as the N except for the wing guns. Hard to compare the two planes, but the Russians removed the wing guns in both making them both the same plane.

 

[XBe02Drvr]

Having limits on spins is not the same as being FORBIDDEN to perform one!

Our Navy Flying Club T-34 was placarded against spins, although at Pensacola they were spun every day. It's just that the civilian type certificate for the T-34B was test flown by the California Forest Department for use as a firefighting air tanker leader, and they didn't see any need to do all the spin testing for their purposes. So the FAA (CAA) issued the certificate with that restriction. There was no aerodynamic or structural reason why it couldn't do them, as I discovered when I pushed it a little too hard in a steep turn and found myself in a spin. It spun nicely and recovered instantly when asked.
Cheers,
Wes

 

[P-39 Expert]

What's this "we" stuff??? But I do agree it's been a real hoot discounting your facts one by one. Can you at least try to stick to one set of facts from now on, please???

Can you point to one single P-39 performance fact from these official tests that you have "discounted". And there were 10 different P-39 models so there are a lot of facts. My story about the British and the P-400 differs from conventional history and I obviously cannot prove that, but it does make sense and other authors have presented this view. I did not make this up.

 

[pbehn]

Can you point to one single P-39 performance fact from these official tests that you have "discounted". And there were 10 different P-39 models so there are a lot of facts. My story about the British and the P-400 differs from conventional history and I obviously cannot prove that, but it does make sense and other authors have presented this view. I did not make this up.

I discount all of them showing that it was of any use at all. Trying to sell an aircraft 2 years behind the game in power and down a cul-de sac in airframe design. Your story about the P-400 is a conspiracy theory with nothing for it and much against it, they should have been called P356 for a start.

 

[pbehn]

Simple, the war started Dec 7th 1941 and the air war ended March of 1944

Ties in nicely with P-39 production, I have the basis of a new conspiracy theory.

 

[drgondog]

The P-39Q was burdened with the gondola underwing guns which cost about 15mph top speed and affected climb/ceiling also. Basically the same plane as the N except for the wing guns. Hard to compare the two planes, but the Russians removed the wing guns in both making them both the same plane.

Looking at the Q-1 Operating manual, it is interesting to note that Only 'clean' was any data prepared for long range cruise up to 20K - nothing at 25 K

Fuel consumption data for cruise stops at 14K -----------> 31.7 in MP, 750 HP and 74 g/hr. but the Cruise tables do show 200mph IAS (280 TAS) at 20K w/220RPM and 24" Mp, but no data above 20K.

The max altitude for Cruise tables with 75 gallon external tank is 15K.

Best time to 25K is 10.1 minutes at 7600# GW, 13.1 minutes at 8100 (w/75 gallon tank) using MP @ 44.5" in Military Power.

Single 50 underwing gondola ~ 6-8mph increase in drag at SL

 

[Milosh]

The max altitude for Cruise tables with 75 gallon external tank is 15K.

Would this indicate no pressurization of the drop tank?

 

[Shortround6]

Can you point to one single P-39 performance fact from these official tests that you have "discounted". And there were 10 different P-39 models so there are a lot of facts. My story about the British and the P-400 differs from conventional history and I obviously cannot prove that, but it does make sense and other authors have presented this view. I did not make this up.

You can find people who claim the earth is flat too.

It ONLY makes sense if you can find actual weight charts that support it. Or memos/memorandum that discus it.
Existing weight data available to the general public does not support this view.
The British were buying NO fighter aircraft without self sealing tanks and armor/BP glass unless for use as trainers at this time (summer of 1940) and strangely enough the USAAF was following suit. NO aircraft without self sealing tanks and armor/BP glass would be categorized as combat capable. Curtiss, Bell, Douglas, Grumman, Brewster and Boeing all got caught by this (and maybe some others).
Blaming the British sounds like sour grapes or trying to cover up that the P-39 was overweight from the day it rolled out the door as the XP-39.

Adding a cabin heater should not turn a world beater into a dog.
Any sales agent worth his salary/commission should have been able to at least estimate any performance penalties from extra equipment and have written in suitable adjustments to the performance penalty/cancellations sections of the contract.

 

[DarrenW]

My story about the British and the P-400 differs from conventional history and I obviously cannot prove that

Yes views might differ but well established facts normally don't. And why is it fine when you hypothesize but when someone else presents their understanding of something, which has no clear cut answer, you dismiss them outright?

 

[DarrenW]

Can you point to one single P-39 performance fact from these official tests that you have "discounted".

Come again???

 

[pbehn]

You can find people who claim the earth is flat too.

It ONLY makes sense if you can find actual weight charts that support it. Or memos/memorandum that discus it.
Existing weight data available to the general public does not support this view.
The British were buying NO fighter aircraft without self sealing tanks and armor/BP glass unless for use as trainers at this time (summer of 1940) and strangely enough the USAAF was following suit. NO aircraft without self sealing tanks and armor/BP glass would be categorized as combat capable. Curtiss, Bell, Douglas, Grumman, Brewster and Boeing all got caught by this (and maybe some others).
Blaming the British sounds like sour grapes or trying to cover up that the P-39 was overweight from the day it rolled out the door as the XP-39.

Adding a cabin heater should not turn a world beater into a dog.
Any sales agent worth his salary/commission should have been able to at least estimate any performance penalties from extra equipment and have written in suitable adjustments to the performance penalty/cancellations sections of the contract.

It should also be remembered that the Hurricanes tanks were not able to be completely self sealing and in any case were vulnerable, Hurricane pilots paid a heavy price for it, but not buying and using Hurricane wasn't an option in 1940. Self sealing tanks were not a silly British whim. I don't know what equipment was on the P-39 at the time but things like IFF equipment weighed 40lbs.

 

[Shortround6]

The P-39Q was burdened with the gondola underwing guns which cost about 15mph top speed and affected climb/ceiling also. Basically the same plane as the N except for the wing guns. Hard to compare the two planes, but the Russians removed the wing guns in both making them both the same plane.

Man, somebody screwed the pooch on that one.
Germans claim only 2-4mph loss for a pair of gondolas with 20mm guns under the 109's wings.
Russians claimed around 12-18mph for the under wing pods on the Mig3 but ti doesn't appear to be the cleanest installation ever seen.

I would also note the pilots manuals show the P-39K doing 300mph at sea level at 2600rpm and 37.5in MAP and burning 97 gallons an hour while a P-39Q doing 300mph at sea level needs the same 2600rpm and a bit higher boost 39in and burns 96 gallons an hour.
The P-39Q is spinning the supercharger impeller over 2000rpm faster (needs a bit more power to turn the impeller) and needs to use a smaller intake opening (throttle closed a bit more) to make roughly the same power to the prop.
15mph at top speed should show up as something at max continuous power.

You have a pair of test results of different airframes with different engines showing one thing and the pilots manuals showing something different.

 

[DarrenW]

Every pilots manual for an American WWII fighter had a warning not to snap roll or spin that airplane....

I guess the Hellcat was the exception to this cardinal rule, huh? So will you finally admit that you were completely wrong when you made this outlandish statement? It's ok, we won't hold it against you....

Excerpt from AN 01-85FB-1 Page 38 (Grumman F6F-3/5 Pilot's Handbook - 1 May 1946):

 

[Shortround6]

Pilots manual for the P-40F & L prohibits spins of more than 3 turns, or any spins with baggage, auxiliary fuel or any other overload.

Snap rolls at speeds over 140mph indicated are also prohibited.
Page 29.

 

[pbehn]

I guess the Hellcat was the exception to this cardinal rule, huh? So will you finally admit that you were completely wrong when you made this outlandish statement? It's ok, we won't hold it against you....

Excerpt from AN 01-85FB-1 Page 38 (Grumman F6F-3/5 Pilot's Handbook - 1 May 1946):

View attachment 487702

I don't know about the USA but in UK from 1917 the ethos of training changed from avoiding dangerous flying events to practicing them in a controlled way.
This was known as the "Gosport system" pioneered by Robert Smith-Barry. In 1941 at a time when the RAF were clipping the wings of the Spitfire to match the FW190 roll rate the idea that pilots were forbidden to roll or spin an aircraft under any circumstances is fanciful. Maybe just another reason the Brits didn't buy the P-39?

Lieutenant-Colonel Robert Smith-Barry | Taking flight | Exhibitions & Displays | Research | RAF Museum
quote
Smith-Barry taught his students to explore the aircraft's capabilities and to learn the cause and effect of any movement in the air. Instead of avoiding dangerous manoeuvres, such as spins, they were taught how to get out of them safely and, by so doing, developed the skill and confidence to fly their aircraft to the limit.

 

[pbehn]

Pilots manual for the P-40F & L prohibits spins of more than 3 turns, or any spins with baggage, auxiliary fuel or any other overload.

That of course depends on the pilot being able to correct the spin before 3 turns and on aircraft like the P-39 whether it is possible at all, after all, a test pilot couldn't manage it.

 

[Shortround6]

Strangely P-40Es were allowed to snap roll at speeds up to 175IAS. Same 3 turn limit on spins

 

[pbehn]

Strangely P-40Es were allowed to snap roll at speeds up to 175IAS. Same 3 turn limit on spins

I don't know about US training but if you cant do a snap roll in training what do you do if the guy you want to shoot down does? Setting height, speed or load limits isn't the same as a prohibition.