From: Joseph F Baugher <jfb@ihlpl.att.com>
Subject: Number Thirty-Nine in the Series--Bell P-39 Airacobra
Keywords: P-39F,G,K,L,and M
Organization: AT&T Bell Laboratories -  Naperville, Illinois
Date: Wed, 16 Dec 1992 17:36:52 GMT


From Joseph F Baugher <jfb@ihlpl.att.com>

The next production version of the Airacobra was the P-39F (Bell Model 
15B).  It was almost identical to the P-39D, but had an Aeroproducts 
constant-speed propeller in place of the original Curtiss-Electric.  
The P-39F could be distinguished from the P-39D by the presence of 12 
exhaust stubs on each side of the fuselage instead of six.  Serials 
were 41-7116/7344.  Some Fs were modified in the field to become 
P-39F-2s with the addition of belly armor and the fitting of cameras 
to the rear fuselage to suit the aircraft for ground support duties.  

A single P-39F was experimentally modified as an advanced trainer with 
a second cockpit ahead of the original one.  All armament was removed, 
and dual controls were fitted.  The designation given to this 
odd-looking aircraft was TP-39F.  

Some P-39Ds were fitted with the 1100 hp V-1710-59 engine with 
automatic boost control and were redesignated P-39J.  Serials were 
41-7043/7056 and 42-7059/7079.  At this stage of the war, the "dash" 
system of subdividing model changes was not yet in effect, and 
relatively minor changes brought about letter changes in the series.  

1800 examples of the P-39G (Bell Model 26) were ordered on August 21, 
1941.  Serials were 42-4244/5043 and 42-8727/9726.  They were to be 
identical to the P-39D-2 except for the new Aeroproducts propeller.  
However, the P-39G underwent several modifications during the contract 
stage, leading to different suffix letters being applied as production 
progressed, and none were actually being delivered with the "G" suffix 
letter.  

For some reason, the suffix letter "H" was never assigned.  The suffix 
letter "I" was never used in any case, since it could be confused with 
the number one.  

The first of the redesignated P-39Gs were designated P-39K-1-BE.  They 
differed in no material respect from the P-39D-2 apart from its 1325 
hp V-1710-63 engine driving an Aeroproducts propeller.  Serial numbers 
were 42-4244/4453, and 210 P-39K-1s were built.  

The next of the redesignated P-39Gs were the 250 P-39Ls.  They 
differed from the K in reverting to the Curtiss propeller.  Gross 
weight was up to 9100 pounds, but the more powerful engine gave better 
low-altitude performance.  A new nosewheel of somewhat different 
design offered less drag at takeoff.  Provision was made for the 
fitting of rocket rails under the wings.  Serials were 42-4454/4703.  
Eleven were modified for photoreconnaissance under the designation 
P-39L-2.  

The third series of redesignated P-39Gs were the 240 P-39Ms, which 
began to appear in November, 1942.  These P-39Ms had a new engine, the 
V-1710-67 which was an attempt to provide improved high-altitude 
performance.  This powerplant developed 1200 hp for takeoff and 1125 
hp at 15,500 feet.  This engine added only ten mph at rated altitude, 
which was still too low for aerial combat, and the Airacobra remained 
primarily a low-altitude ground attack aircraft.  Serials were 
42-4704/4943.  The P-39M-1 subvariant was fitted with the V-1710-83 
engine which had the same characteristics as did the -67.  The serials 
were from the P-39M block.  

Sources:

  War Planes of the Second World War, Fighters, Volume Four, William Green,
  Doubleday, 1964.

  The American Fighter, Enzo Anguluci and Peter Bowers, Orion Books, 1987.

  United States Military Aircraft since 1909, Gordon Swanborough and Peter 
  M. Bowers, Smithsonian Institution Press, 1989.

  P-39 Airacobra in Action, Ernie MCDowell, Squadron/Signal Publications, 
  1980

  The Calamitous 'Cobra, Air Enthusiast, August 1971.

Joe Baugher       AT&T Bell Laboratories    2000 North Naperville Road 
		  Naperville, Illinois 60566-7033.   (708) 713-4548

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