Subject: Number Forty-Six in the Series--Curtiss XP-46

From: [email-masked]
Date: 19 Jan 93 17:39:08 GMT

>From [email-masked]

When the Curtiss P-40 fighter was initially entering production, 
Curtiss's chief designer Donovan Berlin was already thinking about its 
successor.  The P-40 was already largely obsolescent by contemporary 
European standards even before it entered production, and early war 
experience in Europe suggested that more speed, more protection, and 
more firepower would very soon be required.  Influenced by 
contemporary British and French thinking, Berlin submitted his ideas 
to the USAAC.  The USAAC was sufficiently impressed that they issued a 
Circular Proposal (CP 39-13) based on Berlin's proposal.  The Army 
ordered two prototypes from Curtiss under CP 39-13 on September 29, 
1939.  The designation was XP-46 and the serials were 40-3053 and 
40-3054.  

The XP-46 was generally similar to its P-40 predecessor, but was 
somewhat smaller and featured a wide-track, inwardly-retracting 
undercarriage.  The engine was to be the newly-developed Allison 
V-1710-39 (F3R) twelve-cylinder liquid-cooled Vee of 1150 hp.  This 
same engine was also later to power the D-version of the P-40.  In 
view of the relatively high wing loading, automatic leading-edge slots 
(a la Bf 109E) were fitted to the outer portions of the wing to give 
increased aileron control near the onset of the stall.  Armament was 
to be two 0.50-in machine guns in the nose below the cylinder banks 
and no less than eight 0.30-inch machine guns in the wings.  This made 
the XP-46 the most heavily-armed American fighter up to that time.  A 
month after the initial XP-46 order, the USAAC modified their 
requirement and called for the provision of self-sealing fuel tanks 
and armor protection for the pilot.  The maximum speed when fully 
armed and armored was to be a rather ambitious 410 mph at 15,000 feet.  

In order to save time and get something in the air as quickly as 
possible, the second prototype (40-3054) was delivered without 
armament or radio.  This aircraft was redesignated XP-46A.  The XP-46A 
was actually the first to fly, taking to the air on February 15, 1941.  
Even with all the military equipment taken off, the XP-41 was just 
barely able to achieve 410 mph at 12,200 feet, the required maximum 
speed when fully equipped.  

When the fully-equipped XP-46 flew for the first time on September 29, 
1941, the additional weight of the military equipment slowed the 
fighter down to only 355 mph at 12,200 feet.  

In the meantime, while the XP-46 and XP-46A prototypes were still 
under construction, the USAAC had decided in June of 1940 not to order 
the P-46 into production, but rather to order a similarly-powered 
version of the already-existing P-40.  This was eventually to emerge 
as the P-40D.  This decision had the advantage in not disrupting 
Curtiss production lines by the introduction of a completely new 
airframe at a critical period.  In the event, this turned out to have 
been a wise decision, since the fully-equipped XP-46 was actually 
slower than the P-40D.  

Specification of the XP-46: 

One 1150 hp Allison V-1710-29 liquid-cooled engine.  Armed with eight 
0.3-inch machine guns in the wings and two 0.50-inch guns in the nose.  
Maximum speed of 355 mph at 12,300 feet.  Climb to 12,300 feet in 5 
minutes.  Service ceiling of 29,500 feet.  Range at maximum cruising 
speed was 325 miles.  Weights were 5625 pounds empty, 7322 pounds 
loaded, and 7665 pounds maximum.  Dimensions were wingspan 34 feet 4 
inches, 30 feet 2 inches long, 13 feet 0 inches high, and wing area 
208 square feet.  

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.  

  Curtiss Aircraft, 1907-1947, Peter M. Bowers, Naval Institute Press, 
  1979.  

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