Bell P-39 Airacobra...

[Double T]

Sound design or abberation?

Personally, I've always been fascinated by the P-39. There was never anything in the air quite like it. Was it simply a leading-edge concept hamstrung by an un-superturbocharged Allison... or a flawed design with the mid-fuselage-mounted powerplant?
The Russians flew both the P-39 and P-63. I think they enjoyed greater success than did the USAAF, and perhaps even got the cannon-firing thru the prop-hub to be an effective weapon. (Russians had a knack for prop-hub cannons.)
I really want to like this plane--car-door and all. (The Typhoon had a car-door version too.) A very distinctive plane with a nice silouette, but loathed by US pilots in the PTO. So what went wrong with the execution of this design?

Tim

[Lightning]

Hi Double T,

The original design for the P-39 called for a turbosupercharger. It was a contemporary of the XP-38. Both were accepted, at about the same time, to be fast-climbing, high altitude interceptors.

After the P-39 was accepted, the decision was made to delete the turbosupercharger. This deprived the fighter of its major performance-enhancing feature. Had this been done to the P-38 (as it, in deed, was in the British version), the Lightning's career and reputation would have paralleled those of the Airacobra.

A major reason for the USAAF's problems with the Airacobra in the early days of the Pacific war was that many, if not most, of those planes were not P-39s at all; they were P-400s--the export version of the Airacobra. They had less-than-effective, high-pressure oxygen systems, and many of the spare parts were not interchangeable between the types. In their defense, however, these planes did a pretty good job in the ground attack/support role--much better than they're usually given credit for.

Regards,
Lightning

[Groggy]

quote:Originally posted by Double T

Sound design or abberation?

Personally, I've always been fascinated by the P-39. There was never anything in the air quite like it. Was it simply a leading-edge concept hamstrung by an un-superturbocharged Allison... or a flawed design with the mid-fuselage-mounted powerplant?
The Russians flew both the P-39 and P-63. I think they enjoyed greater success than did the USAAF, and perhaps even got the cannon-firing thru the prop-hub to be an effective weapon. (Russians had a knack for prop-hub cannons.)
I really want to like this plane--car-door and all. (The Typhoon had a car-door version too.) A very distinctive plane with a nice silouette, but loathed by US pilots in the PTO. So what went wrong with the execution of this design?

Tim


Must have had some good points, Rolls Royce produced a mock-up of the of Merlin or was it Griffon mid-engined Mustang?

[Ricky]

quote:Originally posted by Lightning

they were P-400s--the export version of the Airacobra.
There was apparently a service joke that a P-400 was a P-40 with a Zero on its tail...
And then they went and issued a P-400!:D

[simon]

As an aside, the RAF also recieved via lend-lease a single squadron of P-400s (The difference between the P-39 and the P-400 was that thanks to the RAF requirement the 37mm cannon was replaced with a 20mm cannon) apparently the RAF hated it and very quickly the squadron was re-equipped.

[ChrisMcD]

I suspect that Lightning is right, the P39 was crippled by it's lack of supercharger.

'Winkle' Brown liked it so much he had one as his personal 'hack' and landed it on an aircraft carrier. So it must have had sweet handling. The idea of putting all the weight at the centre being good for manouvreability is as old as the Sopwith Camel.

Bell were very highly thought of by the USAAF - which is why they got into the jet and rocket programmes.

I think that it was the timescale - when the shortage of turbosuperchargers (or whatever we call them this week) meant that they only went to P38's and B17's.

Also the USAAF seemed to have a thing about low altitude being important for 'persuit' that fataly compromised the P40 as well as the P39 when they encountered first class opposition.

[Kutscha]

The P-39 was more crippled by a lack of a 2 speed/2 stage supercharger, just like the P-51 was until it got the Merlin.

The first combat between the P-39 and Zeros resulted in a 4 for 4 exchange. One P-39 pilot, LtCol Boyd Wagner claimg 3 of the Zeros.

Now I ask, was the P-39 better or worse, performance wise, than the F4F? The F4F held its own against the Zero.

[Trexx]

The center of gravity problem was it's main undesireable characteristic. The weight would change from the discharging of ammo to create a fluid center of gravity during the course of a mission. It was too much for a pilot to compensate for without detrimental manuevering difficulties. The vibration snags from it's driveshaft were being smoothed out and the weapons could be switched to whatever was best. But the center of gravity problem was tenacious.
Otherwise it is quite a superb plane. The door entry is damn sweet! And it was a 1930's era tricycle undercarriaged fighter. I beleive the first ever.

[Double T]

Kutscha:
I wonder if it was a question of tactics, or simply the ceiling of the P-39 that provides the answer. I know the Wildcat had a supercharger and the P-39 did not.
Here's a question...
What if the Flying Tigers were provided with the P-39 instead of the P-40. Would Chenault's tactics have made the P-39 a legend in the same way as the P-40? (The P-39 would lend itself to a nice sharkmouth, wouldn't it?)

Tim

[Kutscha]

quote:Originally posted by Double T

Kutscha:
I wonder if it was a question of tactics, or simply the ceiling of the P-39 that provides the answer. I know the Wildcat had a supercharger and the P-39 did not.
Here's a question...
What if the Flying Tigers were provided with the P-39 instead of the P-40. Would Chenault's tactics have made the P-39 a legend in the same way as the P-40? (The P-39 would lend itself to a nice sharkmouth, wouldn't it?)

Tim


Tim, the Allison V-1710 had a supercharger of the gear driven type. The P-40s and early P-51s had the same supercharger.

Yes, I would say it was a tactics problem. Also a few bad escapades got blown out of proportion and this is all that people hear and remember.

[ssnider]

I talked to a pilot that flew P-39, P-40 and P 51s in combat in the Pacific. He said the biggest problem with the P 39 was that every thing was electric and at least one electric system failed every mission.

[Kutscha]

Tim, here you go, shark mouth P-39,http://www.flybyaviation.com/P-39%20Aircobra%20%2044-3908%20%20-%20%205%20July%202003%20copy.jpg

Also check out the cover page of the S/S book on the P-39.

[Ricky]

Or this...

http://www.ww2aircraft.net/forum/files/p-39_shark_591.jpg

(Sorry Ricky, I've had to edit this one as all that comes up is a message saying the site concerned does not allow linking of pictures. Follow the link instead. Simon.)

(oops, sorry, did not notice - many thanks Mr Moderator!)

[Trexx]

These are all great comments for a fighter plane worthy of examination. Nice work, gentlemen!

[Trexx]

quote:Originally posted by ssnider

I talked to a pilot that flew P-39, P-40 and P 51s in combat in the Pacific. He said the biggest problem with the P 39 was that every thing was electric and at least one electric system failed every mission.


This is the first time that I've heard that critique. ...interesting...

[Trexx]

Here's a thingy I stumbled upon:"

CREDIT: http://home.att.net/~C.C.Jordan/XP-39.html

How America's Best Pre-War Single Engine Fighter
Was Ruined By The Air Corps

At the time the Bell was being evaluated, the AAF was deep into "streamlining" as a way to improve aircraft performance. This is somewhat understandable, due to the relatively low powered aircraft engines of the 1930's. By reducing drag, especially parasite drag, the engineering minds at Wright Field found that significant increases in performance could be attained. This was all well and good. Unfortunately, they carried it too far as it related to the XP-39. NACA engineers decided that the Bell's turbosupercharger inlet created too much drag. Certainly the inlet generated no greater drag than did the Prestone inlets on the Lockheed XP-38. Nonetheless, they were insistent, the inlet scoop had to go. They reduced the height of the canopy, chopped 2 feet off the wing span and lengthened the fuselage by over a foot. A less powerful Allison with only a single stage mechanical supercharger replaced the turbosupercharged engine. This effectively eliminated decent high altitude performance. Thanks to these changes, the Airacobra had it's center of gravity shifted further aft, exacerbating its already marginal stability. All said and done, the people at Wright Field had reversed the old cliche, and created a sow's ear out of a silk purse.

Certainly Larry Bell and Bob Woods were outraged at the butchered result. Unfortunately, there was very little they could afford to do about it. Bell Aircraft was at the edge of bankruptcy. Having only produced 15 total flyable aircraft, of any type, Bell was deep in debt. Neither Bell nor Woods were willing to go to the mat for their beautiful fighter. To preserve the company's financial viability, they would have to take it on the chin. Their pressing need was to get an order and establish some inward cash flow.

Fortunately, Bell sold the French on the P-39 and received 2 million dollars in advance on an eleven million dollar order. Later that same year (1940), Bell received orders for just under 1,000 P-39Cs and Ds from the USAAF. These were equipped with self-sealing fuel tanks and additional armor, the weight of which, only further degraded performance. Without the turbosupercharger, or even a gear driven two speed, two stage supercharger, the Airacobra was not capable of taking on modern fighter aircraft at anything above 10,000 feet. It should also be noted that the early versions of the Allison V1710 engine never produced anything close to their advertised power rating without a turbosupercharger pressurizing the intake system.

Overall handling had degraded to a point where some claimed (without a grain of truth) that if the pilot simply sneezed, the plane would spin. Some Brits flat out refused to fly the plane, one pilot saying it was more dangerous to RAF pilots than the Luftwaffe. Such extreme examples of exaggeration followed the P-39 throughout its service life.

Adding to the general unhappiness with the airplane, the 37mm Colt M4 cannon frequently jammed after only firing a few rounds. The balance of the guns, 2 .50 cal. M2 and 4 .30 cal. Brownings were inadequate by 1942 standards. One of the problems pointed out by the British was the cockpit being filled with cordite fumes after firing the guns. They also found that firing the guns would knock the magnetic compass out of whack. The RAF did admit that at low level they found the Airacobra to be a match for the Bf-109E. Unfortunately, the RAF needed a high altitude fighter. Besides, the Luftwaffe was now getting newer and far better performing fighters.






Because the Russians were seemingly satisfied with the P-39 is not indicative of the aircraft's performance as much as the Russian's desperate need for combat aircraft. Moreover, the air war on the eastern front was fought largely below 20,000 feet, and more often than not, well below that. At these heights, the P-39 possessed some marginal level of capability. Credit must be given to those Soviet pilots who, despite the severe limits of the aircraft, used them very effectively against the Luftwaffe's superior Bf 109s and Focke Wulf 190s.

Bell P-39s served in North Africa and Italy with the USAAF and several other Allies including the Free French and Italians. Airacobra service in the Pacific has been the subject of many books and articles. In a single sentence; the "Iron Dog" was replaced as quickly as possible.

Taken as a whole, the P-39 was a dismal failure of the AAF's engineering and procurement establishment to identify and develop the better attributes of an advanced and promising fighter aircraft. This was the same establishment that prevented Lockheed from installing Merlin engines in the P-38 as early as 1941. Had the USAAC (Air Corps) not stripped the turbosupercharger from the XP-39, the United States may have entered the war with a competitive single engine fighter plane already in service. Indeed, it was not until the advent of the Bell P-63 that the level of performance finally matched that of the Bell XP-39 of 1939. Of course, by that time, the P-63 was already outclassed by the P-38, P-47 and P-51. Indeed, the P-63 was too little too late. In large part, it was the Air Corps myopic vision of the future of aerial warfare that caused it to be so.



RESOURCES:
Rick Mitchell, The Complete Story of Bell Aircraft Corporation's P-39 Pursuit Fighter Plane.
Ernest R. McDowell, P-39 Airacobra in Action.
Francis H. Dean, America's Hundred Thousand.
Warren M. Bodie, The Lockheed P-38 Lightning.

[Tony Williams]

That article is a bit biased. The early reliability problems with the 37mm gun were soon traced to a spent case ejector chute which encouraged the spent cases to get jammed rather than eject. The shape of the chute was altered and the problem went away. After that, the gun was reliable. Of course, its ballistics still sucked but that's another matter!

I think that the P-39 was a brave and interesting design which didn't quite work out. Personally, I would have liked the designers to have been even more radical. Split the drive from the engine to two small wing-mounted props. That leaves the nose clear, so move the cockpit up front with the gun actions and magazines behind it. You then achieve the following advantages:

1. Magazines moved back towards the CG, so addressing the CG-shift problem as ammo is used up.

2. The .5" guns no longer need to be synchronised, improving their rate of fire by about 60%.

3. Pilot's forwards and downwards view is much improved.

4. Propwash goes straight over the wings and flaps, helping with low-speed lift.

Develop this variant as a ground attack plane, with more armour, and fit it with the high-velocity 37mm M9 gun (which was installed in the single P-63D prototype) and you have a neat little tankbuster which could also defend itself against fighters.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk

[Tophe]

quote:Originally posted by Double T
Personally, I've always been fascinated by the P-39. The Russians flew both the P-39 and P-63.
Tim
Do you know the Russian Twin-Airacobra project? and the French what-if Twin-Airacobra & Twin-Kingcobra? P-39T+P-63T= double-T, like Tim-Tom, somehow:) (they are illustrated as thumbnails on my homepage, and the book with them can be downloaded for free);)

[Trexx]

I have just realized what a small and compact little airplane it actually was.
It was excellent example of innovation and what the modern age would bring, having advancements far and away from it's contemporaries of 1938-39.

[Double T]

Trexx:
Very interesting insights. Thanks for sharing...

This is not the first time that I've heard critisism of the USAAC procurement-policies. Honestly, it sounds like they found a way to ham-string most every innovative design put forth. They insisted the Allison powerplant be used, even though the Merlin was clearly superior. Deny the two-stage turbosuperchargers and doom a promising design.
It's a miracle the P-38 was allowed to evolve into the legend it became.
Maj. Alex Seversky was scathing in his book "Victory Through Air-Power." Some of these inflexible policies and un-enlightened thinking ring as crazy as Hitler's insistence on the Me262 being a 'schnell-bomber.'
As to the 37mm cannon...
There seems an underlying tone of 'overkill' in the books of airpower theory I read from the 1930's. The concept of 'bomber-destroyers' that heralded the "Zerstorer" Me110 for example. Some of the artist's conceptions show airframes bristling with large-caliber weaponry.
The Bell P-39 Airacobra had more going for it than a 'cool-name.' Just imagine if it had been allowed to mature as designers envisioned and not subject to ridiculous mandates imposed by USAAC procurement-policies. It sounds like the entire process with riddled with corruption, influence-peddling and incompetency. The radical-looking P-39 certainly deserved better cards than it was ultimately dealt. What a shame.
Using the latest technology and engine-power available, it should have been the scourge of the South-Pacific in the early-days of the war, chewing-up Zeros and Oscars... like a 'Lightning.'

Tim

[Double T]

Tony:
I wish I could scan images. I have an artist's depiction at my fingertips that is similar to what you describe. The engine(s) were located in the fuselage, and shaft-gear-driven to pusher-type props in the wings. In one twin-engine concept, there was a gunner-station in each wing with a 37mm cannon facing forward. LOTS of firepower.
Pretty far-out thinking, but serves to underline the notion that "Victory through Superior-Firepower" is a valid concept.
Ohh-Rah.
Thanks for sharing.
Tim

[simon]

A couple of points I'd like to pick up here.

Firstly the German concept of the Zerstoerer pre-war (Sorry RTF, No umlauts on my keyboard!) is completely different from a bomber destroyer. Zerstoerer were to sweep ahead of the bomber formation using their speed and overwhelming firepower to destroy the intercepting fighters. They were to be an offensive rather than defensive weapon.

I read an interesting article on line a while back about how the USAAC Killed the Airacobra (That may have even been the title), it was interesting but highly biased. Whilst the lack of turbo superchargers still seems odd, most of the rest of the criticisms were of changes to the design that the USAAC insisted on which increased the weight to the detriment of performance. This might seem bad except when you consider that the changes referred to were adding armoured plate, self-sealing fuel tanks, all the kind of things that early combat in Europe in WWII showed were important in a contemporary warplane.

[Kutscha]

I have read that the Merlin P-38 was killed by lobbying in Washington by GM, Allison being part of GM.

On the P-39/P-400 in the Pacific, would put it down to tactics. The F4F was not quite as good (imho) as the P-39, yet the F4F did vey well against the Japanese a/c.

Hitler's insistance that the 262 be used as FB is not that crazy. The prop FBs were having a tough time of it in the West. The speed of the 262 would give the a/c some servivability. The only question is, how long would it have taken the Allies to come up with counter measures?

[CAPILATUS]

Hi all! My friend from Ukraine is going to interview a veteran, flying P-39Q throughout the war. We're collecting now questions we'd like to ask, then she will visit him and have the interview.

As soon as the interview done I'll try to translate it in to English in details.

If you wanna ask her few questions concerning P-39 to be added in the list - hurry up, she will visit him on the next week. Just send them to my mail yarikmln@mail.ru

Regards, Capilatus

[Wuzak]

quote:Originally posted by Tony Williams

I think that the P-39 was a brave and interesting design which didn't quite work out. Personally, I would have liked the designers to have been even more radical. Split the drive from the engine to two small wing-mounted props. That leaves the nose clear, so move the cockpit up front with the gun actions and magazines behind it.

Sounds like an Arado project http://www.luft46.com/arado/are561.html

Except in teh Arado case there were two engines.

[Trexx]

One thing I have recently learned is that there are many different explainations to it's developmental problems and many different views to it's best use. This is an intriging airplane indeed!

Check out the photographs, they do show a nice shape!

http://img.villagephotos.com/p/2004-11/897605/P-39s_.jpg
I think these boys were trying to break their mounts, by the look of the thrashed paint jobs and intense exhaust scorching...

http://img.villagephotos.com/p/2004-11/897605/P-39_XP-39best.jpg
Here's the XP-39. Look how small of an airplane it was... almost dainty...

[Trexx]

More great shots:

http://img.villagephotos.com/p/2004-11/897605/P-39_line.jpg
Line 'em up, move 'em out!

http://img.villagephotos.com/p/2004-11/897605/P-39_XP-39_alt.jpg
Another photograph of a prototype.

http://img.villagephotos.com/p/2004-11/897605/P-39_gas.jpg
Saucing them up.

[Trexx]

A nice in flight picture:

http://img.villagephotos.com/p/2004-11/897605/P-39_in_flight.jpg

[Mark J]

Some nice photo's

Have you seen this site?

http://home.att.net/~jbaugher1/p39.html

some good reading

cheers

[Groggy]

quote:Originally posted by Mark J

Some nice photo's

Have you seen this site?

http://home.att.net/~jbaugher1/p39.html

some good reading

cheers


The P39 is an interesting aircraft, the tricycle undercarriage was the way to go. But did not some American pilots say that it was prone to Tumbling?

[Trexx]

quote:Originally posted by Groggy

quote:Originally posted by Mark J

Some nice photo's

Have you seen this site?

http://home.att.net/~jbaugher1/p39.html

some good reading

cheers


The P39 is an interesting aircraft, the tricycle undercarriage was the way to go. But did not some American pilots say that it was prone to Tumbling?


Apparently there was quite a lot said about the Airacobra.

[Lightning]

Hi Trexx,

Re: Your postings of Oct. 5

I think the use of the big white numbers denotes that these planes were used by a pilot-training unit. I know that was common practice during the war. Most of the planes used were out-dated early models or war-weary airframes.

It is intereting to note that the air intakes on the prototype shown in the first posting are on the side of the fuselage rather than behind the canopy. Compare with the prototype shon in your second posting of that date.

Regards,
Lightning