P-39 Airacobra

[AdmRose]

Anyone else think this fighter would make a good addition to AH?

(Technical specs would be apprecaited, I'm good, not great)

[whgates3]

would be a good plane to have, but would get eaten alive by the good fighters...maybe i'm biased because i dont know how to get out of an inverted spin

[whgates3]

it did see wider use than any fighter plane in WWII other than the P-40

[Holden McGroin]

Type: Single seat fighter-bomber

Date Available: May 1943

Powerplant: Allison V-1710-85 liquid-cooled

Horsepower: 1,200 hp.

Weight-Empty: 5,645 lbs.

Loaded: 7,700 lbs.

Max Over-loaded*:8,300 lbs.

*Can Carry: 1 - 500 lb. bomb or 1 - 75 Imp. gallon drop tank

Max speed and altitude achieved: 385 mph @ 15,000 ft.

Initial climb rate: 2,778 ft/min.

Time to climb to-5,000 ft: 2 mins.

15,000 ft: 4.5 mins.

20,000 ft: 8.5 mins.

Wing Area: 213 sq. ft.

Wing Loading: 36.15 lbs./sq. ft.

Power Loading: 6.42 lbs./hp.

Ceiling: 35,000 ft.

Range: 525 miles normal

Armament: 2 - 50 cal machine guns (nose) with 200 rpg

2 - 50 cal machine guns (1/wing) with 300 rpg

1 - 37mm cannon (nose) with 30 rounds


A highly modified P-39 piloted by Tex Johnston (who later barrel rolled the prototype 707 in front of spectators in Seattle ...twice) won the post war Thompson Trophy Air Race competeing against mustangs, spitfires, and the rest.

Seems the Aircobra got little press as most action was on the eastern front.

[fdiron]

P39 would have been a good aircraft if it didnt have a crappy allison engine.

[whgates3]

nah - it had odd (poor) flight characteristics, probably due to weird center of gravity, and a tendency to end up in inverted spins.  This and it's low ceiling made it a death trap for lesser pilots - maybe thats why the USAAF used it for fighter training.  37mm packs a hell of a punch though, but tough to hit anything in the air with it, although it was done at least once - by Art Rice of the 57th Pursuit Squadron during the Aleutian capaign

[nuchpatrick]

The P-39 was also used widely in the Pacific tour as well.  They were mostly used for ground attack.  The 37mm jamed quite often and was later replaced with 20mm cannon which was more reliable.

[Captain Virgil Hilts]

Originally posted by fdiron
P39 would have been a good aircraft if it didnt have a crappy allison engine.

BULL! The P-39 would have been fine if the USAAF and NACA had not taken the turbocharger off the Allison and screwed up the center of gravity, among other mistakes. Try reading the article at Widewing's site Planes and Pilots of World War II.

The biggest enemy of the American fighter pilot in World War II was a combination of incompetent idiots in his own branch of service and in the NACA and the War Production Board.

[Holden McGroin]

Read "Tex Johnston: Jet Age Test Pilot"

He was chief test pilot for Bell and then Boeing, and he liked the Aircobra.  Johnston atributed inverted spins to poor pilot skills, and with proper procedure, any spin was easy to recover.  The controversy was that some pilots misjudged the inverted spin for "tumbling", going nose over tail, and that was the urban ledgend the aircobra had to live down.

Also, all planes have a center of gravity near the center of lift, or they aren't airplanes (they dont fly) The Aircobra is no different.  Notice that the pilot is in front of the wing, the weight and balance has been adjusted so the center of gravity and center of lift are close to each other.  (actually in conventional rather than canard layout, the C/L is just behind C/G)  

At  least this was true until lately, when unstable airplanes were artificially stabilized by computer power.

[Tony Williams]

Originally posted by nuchpatrick
The P-39 was also used widely in the Pacific tour as well.  They were mostly used for ground attack.  The 37mm jamed quite often and was later replaced with 20mm cannon which was more reliable.

The 37mm was initially unreliable but that was soon fixed - it was to do with the ejection chute for empty shells rather than the gun itself.  Some (P400) were built with 20mm guns at British request, and some of these were used by the USA, but the 37mm M4 remained standard throughout the plane's production.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk
Discussion forum at: http://forums.delphiforums.com/autogun/messages/

[Arcon]

Regarding the "C/G" instability of the p39:

Not a problem with the C/G.  It's a problem with the relative location of MASS to the C/G.  Most of the mass of the p39 was located closer to the C/G than in any other aircraft.

In a situation where the plane was departing from normal flight conditions, this made it more unstable.  When the plane is falling through the air rather than flying, mass near the center of geometry reduced the planes tendency to "right" itself.

Also, in initiating a spin, it takes less energy to get the plane rotating about the geometrical center; the mass at the center isn't rotating that quickly and has little rotational inertia.

Planes with engines in the nose have alot more mass further from the point of rotation in a spin, hence, it takes a lot more energy to get them yawing about the center of geometry.

Its an interesting test of a sim's flight model to see how it models the quirky distribution of mass in the p39 near departure speeds. I'm very curious as to how AH would fare.

[akak]

I got this from a newsgroup posted by an ex-WW2 pilot named Earl that used to fly in Air Warrior.  During the war, he flew everything from the P-38G to the P-39Q.  The comparison is writting by another former fighter pilot and quite interesting.  Due to the size, it's in 2 posts  Enjoy.

About the airacobra versus the thunderbolt--it is a rather
complex story and the differences are difficult
to assess in a few words.  I think the main point to keep in mind is that the two fighters represented two very different technological periods--though only some three to four years apart as start up projects. The power plants of the two represented the maximum engine capability achievable at the time.  

The P-39 was designed around a 1000 horsepower engine, not yet available in 1936, when it's design began.  The P-47 was designed around a 2000 horsepower engine, also just coming on stream,
development wise, in 1939-40, when the aircraft design took shape.  (note, I might be off a bit, time wise, on the latter date(s)).  Obviously the two powerplants offered very different challenges and opportunities for the two design teams.  One was highly constrained by weight and size while the other had the power to lift a great deal more weight, providing the possibility of achieving not only more range but greater armament striking power in the design.  It was conceived as a long range fighter interceptor--no one dreamed that the the fighter, a "defensive" weapon, would ever be used as an offensive weapon, in the prewar period.  
Bombers were the only offensive air weapon and they would be able to carry enough defensive armaments to take care of themselves, thank you.  Fighter escorts would not be required.  Both concepts being 'gospel' in the ranks of the senior bomber generals running
the prewar Air Corps.
 
At the time the P-39 was developed the concept was to build an interceptor capable of operating near
top speed at 20,000 feet.  All fighters of the time had engines with at least a single stage supercharger to allow the engine to produce maximum power somewhere around seven to ten thousand feet.  This enabled the engine to be effective near sea level, seven thousand feet below max power, and also at
some seven thousand feet higher than the max power altitude, or, up to some 14 or 15 thousand feet, as an example.  But the only way to achieve full power at 20,000 feet, or higher, was to provide the engine with a two stage supercharger.  That could be achieved by two means, either a second stage mechanical system, or via exploiting the exhaust gasses of the engine to drive a turbo supercharger to gain the added 'boost' for the second stage.  
 
When push came to shove, the Air Corps punted, on the P-39 design.  Originally, the Air Corps had
opted for a turbo supercharger, in line with the P-38 engine decision.  But the design of the P-39
airframe made it difficult to bolt an experimental turbo supercharger to the P-39 engine.  Unlike the
German and British approach where their Daimler-Benz and Rolls Royce engines were modified, as possible, to accomodate the tight designs of the Me-109 and the Spitfire, the Air Staff did not insist that Allison modify an engine to make it easier to integrate a turbo charger into the specific design of the Airacobra--or demand that they take the time to produce a
second stage mechanical supercharger.

With the outbreak of WW II in Europe the US was desperate for all the fighters that could be produced in 39-40 , and the Air Corps chose to concentrate on numbers over technological cutting edge design. As a result, Allison (part of GM) was directed to gear up to build all the 'standard' engines they could, as fast as they could, and Bell was, in effect, told to forget about a two stage supercharger for the Airacobra.  Thus, both Bell and Curtis were committed to
produce large numbers of P-39s and P-40s
and to stick a standard Allison engine into each.  As a result both of these aircraft reached their
maximum horsepower capability in the mid altitude range of something under 10,000 feet.  As indicated, Allison did produce an engine with a turbo supercharger for the large P-38 Lightening design.  
 
Aerodynamically, the P-39 was a very slick design, however, and still had enough power at some 1100
to 1200 horsepower, (by 1940/41 the engine power had achieved this range) to be a serious
contender, up to 15,000 feet.  In tests conducted by the
RAF's Air Fighting Development Unit in July
1941, they determined that the P-39 could out run and out dive their Spitfire Mark V , the latest version reaching combat units, below 15,000 feet. However, the Spit was superior to the Cobra in both turning radius and in the climb.  More important, they flew a captured Me-109 E, the Battle of Britain fighter, against the P-39 and found that it could outrun, out dive and out turn the Messerschmitt at 15,000 feet and below.  Though the document I have seen does not mention it, I assume that the mechanically driven two stage supercharger of the Me-109 enabled it to easily out climb the P-39 at all altitudes, as the latter was both heavier and had less horsepower than the 109.  Unfortunately, this important performance information about the relative
strengths and weaknesses of the P-39 versus
the Me-109 was never shared with the P-39 pilots in combat.    
 
The E model of the Me-109 was not the latest version in 1941, the F had reached some Luftwaffe
units but its mid and lower altitude performance was not materially improved over that of the "E".  When I tested an Me-109 G against the P-39 in February 1944, I came to the same conclusions the RAF had reached, two and a half years earlier.  I had no knowledge of the earlier tests, of course. But above some 15,000 feet the single stage supercharger of the Airacobra's power plant caused its horsepower to drop off steadily with every increase in altitude.  So, in summary, the P-39 was quite advanced, aerodynamically, at the time, but limited by its engine design.  The Germans and the British, were, of course, confronted with the same engine design problem for
their two small fighters, the Me-109 and
the Spitfire, both about the same size as the P-39.  It should be noted that the Germans succeeded in adding a two stage supercharger to their bird first, followed by the Spitfire (I believe I have the order
right) by 1939 or 40.  The Airacobra never achieved that capability though its follow-on, redesigned as the P-63 Kingcobra, was equipped with a mechanical two stage boost system which gave it a competitive speed capability at 20,000 feet and above.  However, the US never fielded the P-63 in combat--almost all the production going to the Red Air Force, which had achieved high scores with the P-39 in air to air combat on the Eastern front, against the same enemy we faced in the MTO.  
 

Ack-Ack
479th FG - Riddle's Raiders

[akak]

Here's the second part...Enjoy

In the summer of 43 each Squadron in the 350th Group was equipped with two P-38s to augment their
P-39s so that we could intercept the high flying Luftwaffe reconnaissance flights being sent down to surveil the fleet gathering for the invasion of Sicily.  We kept a flight of two P-39s and a single P-38 on 5 minute scramble alert at the end of the runway of the airfields we occupied on the Algerian coast.  On scramble, we usually got all three aircraft off in 3 minutes, the two 39s usually going first as the P-38 had
to start two engines.  The P-39 could hold its own with the P-38 up to some 13 to 15 thousand feet,
but above that the 38 pulled away steadily.  I flew both aircraft on these scrambles and of course was highly impressed with the 38's climb at higher altitudes and its range capabilities.  But I was not impressed wih the design; for a single engine fighter pilot it was too big to be nimble, though it could turn with, or almost with, the P-39, when we rat raced.  But it had too much wing and fuselage on each side of the cockpit capsule to be an ideal design for detecting
approaching enemy fighters.  However, none
of the early designs gave the pilot a view to the rear, certainly not the P-39, Me-109, P-40 or the early P-47 and P-51.  The Hawker Typhoon and Fw-190 showed the advantage of the bubble canopy
design, adopted for all subsequent fighter aircraft.  
 
I did not fly the P-51.  It was a racer, with  range enough to escort bombers to any target in Europe, when they added the fuselage tank.  It was not nearly as survivable as the Jug but was a fine aircraft for escort duty, once the Allison engine was replaced with the higher performing, two stage supercharged British Rolls Royce mill.  
 
The Jug was a huge beast, twice the loaded weight of the Cobra, but with its turbosupercharger it had an excellent high altitude capability and was an easy and honest bird to fly.  A pilot had to be a bit more skillful to get the maximum out of the P-39 design.  Any fighter of the time could be forced into a snap roll if the pilot was ham handed enough and exceeded the lift of the airfoil by overcontrolling the aircraft.  However, the Airacobra was easier to slip into this condition when on its back and with its nose up.  In such cases, the aircraft sometimes snapped into
a wicked rotating action before ending up
in a spin that was harder to break than with most fighters of the time.  With experience in the bird, spins were no problem, you could rack the bird around just as hard as any fighter, you simply kept the bird flying and stayed out of spins.  This did not require any conscious "thought" on the part of the pilot, any
more than a race driver "thinks" about getting through an up-coming curve.  The experienced pilot
sensed where the max limits were and controlled the bird accordingly.  Any pilot in any fighter who over controlled and ended up in a spin quickly became vulnerable in the recovery maneuver to any
opponent alert to take advantage of the opportunity.  But that was still the era when it
was deemed desirable for pilots to familiarize themselves with spins in a fighter.  The Air Force
abandoned that approach 30 or 40 years ago and has trained its pilots to stay out of spins ever since.  I think we lost 4 P-39 pilots to spins and, off the top of the head, I can recall only one lost in a Jug.  
 
The P-47 turned well, climbed poorly--in comparison with the Spitfire, for example-- and almost certainly relative to the Me-109, an excellent climbing machine--at least up to an altitude above 20,000 feet.  However, it reputedly gained the advantage over the Me-109 at the highest operating altitudes of WW II.  In September and October 44 we often encountered
thunderstorms over the Apennines, blocking our entry into the Po valley.  We routinely attempted to fly over these storms and I have led flights loaded with the belly tank and two 500 pound bombs
to 27,500 feet, over the top of the
'bumpers' and on to our target in the Po.  We could only admire a machine with that capability.  The P-47 could out dive anything in the sky, constrained only by compressibility, a high speed condition at high altitude that resulted in the stick being frozen in place with the pilot losing any capability of pulling out of the dive until the aircraft reached  denser air at some 10 to 15 thousand feet.  On reaching the lower altitude where the pilot could regain control, he had
only a few seconds to pull out and avoid
impact, of course.  However, as the word got around on compressibility, pilots simply avoided the condition by throttling back in a dive, as necessary.  The jug's speed on the straight and level was competitive but not outstanding--our pilots lost some long chases with the Luftwaffe reconnaissance birds.  It had great survivability and dished out a withering fire with 8 fifty caliber machine guns which had a long firing capability with 800 rounds per gun.  The
P-39 had adequate fire power with a 37 mm
cannon and two fifties in the nose, and four 30s in the wings--but it had a short firing time with its cannon and fifties.  On the other hand, each of the 30s had a thousand rounds capacity.  The only time we carried the full load of 30s was on strafing missions--for air defense operations we normally loaded only
4 or 5 hundred rounds for each wing gun.  The Me-109 had a 20mm canon and two 30s in the nose, in the straight air to air fighter version.  The 30s were replaced by 50s with the G version, the model with the largest production run.  Again it had a short firing time.  A Bell Technical Representative in the Soviet Union during the war stated in correspondence to the factory that some of the Red Air Force units had removed the four 30 caliber guns from the wings of their P-39s to lighten the bird for air to air combat.  Their highest scoring pilots claimed up to 60 kills total, double the highest scoring American pilot on the Western Front.  Some of the top
scoring pilots flew the P-39 with some claiming
up to 40 kills in the Airacobra.  By contrast, I had an opportunity to shoot down two Me-109s with the P-39, apparently the only Airacobra pilot to do so in the MTO.  So you can see that we had drastically different missions--they used the bird as a counter-air, air superiority fighter over some of the largest battles on the Eastern Front in the 42-43 period, when it was one of the top performing fighters in their inventory.  We, on the other hand, used the bird primarily
in a defensive role in the MTO and secondarily as an offensive fighter-bomber, and never in
an air superiority role.  Our Group shot
down two Fw-190s, and five Me-109s, with P-39s, all confirmed in the post war, and lost four P-39s
to Fws and Mes.  Henry Nelson was also shot down in a P-39 on the flight from England to Africa on 5 February 43, after his flight broke up in a severe storm, out over the Bay of Biscay.  A German pilot, Hermann Horstman, in a Ju-88 fighter version, stumbled across him while on patrol and probably ambushed him.  Not a real fighter to fighter aerial combat, as we envision such actions, but none the less a loss to an enemy fighter.  In addition to the fighter kills, our pilots in Airacobras, shot down another six
bomber and reconnaissance aircraft.   But our total P-39 kills are so few in number that they seem appaling in comparison to claims made by P-39 aces in the Red Air Force.  
 

Ack-Ack
479th FG - Riddle's Raiders

[akak]

Here's the final part, thought it would have been able to fit in two parts but I guess not.  

Flying P-38s, it appears from German records that our pilots shot down seven reconnaissance birds
over a three month period.  I have not counted any claims for which there is no confirmation, at least so far, in Luftwaffe records.  Like all organizations of all Nations, pilot claims exceed opponent losses.  As for the Jug, our pilots shot down some 20 Italian pilots flying Me-109s in the last eight months of operations over northern Italy--without a direct loss.  However, one P-47 was lost when it's tail wheel would not come down for landing at Pisa after having taken
several 20 mm rounds in the tail.  The pilot,
Tomlinson, of 346 Sq. landed on the tail and was able to get the bird almost all the way off the landing strip.  However, before it could be moved, an 86th Fighter Group pilot landed and failed to see Tommy's aircraft in time to avoid it, crashing into it and wiping out both birds.  So, in fact, the record was 20 versus 1, or 2, depending on how one wishes to scores it.
 
The P-39 had only one external shackle, while the Jug had three.  As we had only the one hanger, when we carried a bomb, either a 500 or a 1000 pounder, we were severely restricted in our strike range.  We carried out strikes across the 80 to 140 mile run from Corsica to coastal targets along central Italy but had little endurance for carrying out extended strafing forays after dropping our bomb.  The P-47 had a 110 gallon drop tank and could carry two 500 pound bombs to most targets in the Po Valley, from Pisa.  We had enough ammunition and fuel after dropping
bombs to spend considerable time hunting for strafing targets, on most missions. In the final
battle of the war in Italy, in April 45, some of
our sorties were flown without the centerline drop tank and two 1000 pounders were carried to the Po
by our P-47s.  
 
With its up front cockpit and abbreviated nose, the P-39 gave the pilot the best strafing platform of the WW II fighters. From near zero altitude you could see every thing in front of you in a 180 degree arc, pop up to two or three hundred feet and push over to execute a quick firing pass, minimizing exposure to enemy flak.  The Jug had a huge nose that the pilot had to look over, requiring flight at a few hundred
feet to enable an effective strafing pass.  I found the nose gun tracers of the P-39 far more effective as an aiming aid than the spread out tracers fired from the wing guns of the P-47.  Though only some 10 feet out on each side from the pilot's line of sight, the wing guns simply did not provide the direct contact with the target that the tracers did when eminating from a
few inches below the pilot's eyes.  You could
look straight down the string of tracers right into the target and had an instantanious feed back on how to adjust your aim to correst any error in your bullets impact.  You got a similar imput from the wing gun tracers but their off set position and converging pattern was simply not equal to the nose gun feed back. With its rugged radial engine the P-47 was much more survivable than the P-39 with its glycol plumbing system, though the little bird was structurally quite strong.  
 
That's some of the story, off the top of the head. If I had the time to restudy some of the dates and
other numbers, I'm sure I would have to change some of the above, a bit--but its close enough to give you some idea of the strengths and weaknesses of the two birds.  I enjoyed flying both aircraft--butwas terribly disappointed in the missions we drew most of the time with the P-39--as were all the Group's pilots.  C'est la guerre.
 
Cheers,
 
Hugh

Ack-Ack

[MOSQ]

Bring the P-39 AirCobra  and P-63 KingCobra to Aces High !

http://www.ophetweb.nl/ww2w/ww2htmls/bellp63.html

http://www.ophetweb.nl/ww2w/ww2htmls/bellp39.html