In the late 1930s, the USAAC
was planning to expand its force, and on January 25, 1939. manufacturers
were invited to submit proposals for pursuit aircraft. The Army
was still thinking in terms of low-altitude, short-range fighters.
Among the contenders were the Lockheed XP-38, the Bell XP-39,
the Seversky/Republic XP-41 (AP-2) and XP-43 (AP-4), and no
less than three planes from Curtiss, the H75R, XP-37, and XP-42.
Although the XP-40 could not match the performance (especially
at altitude) of the turbosupercharged types, it was less expensive
and could reach quantity production fully a year ahead of the
other machines. In addition, the XP-40 was based on a already-proven
airframe that had been in production for some years. Consequently,
on April 26, 1939, the Army adopted a conservative approach
and ordered 524 production versions under the designation P-40
(Curtiss Model 81). At that time, it was the largest-ever production
order for a US fighter, and dwarfed the service test orders
placed that same day for YP-38 and YP-39 fighters. A couple
of weeks later, 13 YP-43s were also ordered.
The P-40 was similar to the
final XP-40 configuration except for the use of 1040 hp V-1710-33
(C15) engines. The armament was the standard USAAC armament
of the day-two 0.50-inch machine guns, mounted in the upper
nose and synchronized to fire through the propeller arc. Provisions
were made for the mounting of one 0.30-inch machine gun in each
wing. Flush riveting was used to reduce drag. Armor, bulletproof
windshields, and leakproof fuel tanks were not initially fitted,
were later added to the aircraft while it was in in service.
The P-40 was a relatively clean design, and was unusual for
the time in having a fully retractable tailwheel.
The first flight of a P-40 (Ser
No 39-156) was on April 4, 1940. Maximum speed was 357 mph at
15,000 feet, service ceiling was 32,750 feet, and initial climb
rate was 3080 feet per minute. An altitude of 15,000 feet could
be reached in 5.2 minutes. Cruising speed was 272 mph, landing
speed was 80 mph, and the range at 250 mph was 950 miles. The
length of the P-40 was 31 feet 8 3/4 inches, which became standard
for all early models. Weights were 5376 pounds empty, 6787 pounds
gross, and 7215 pounds maximum.
Deliveries of the P-40 to Army
units began in June of 1940. Three of the P-40s were used for
service testing, the USAAC contract making no provisions for
the standard practice of supplying YP models. They were delivered
with full camouflage applied-olive drab on the top and grey
on the undersides. The standard rudder stripes and star insignia
were applied to both wings.
The first USAAC units to operate
the P-40 were the 33rd, 35th and 36th Pursuit Squadrons of the
8th Pursuit Group, based at Langley Field, Virginia. It was
soon followed by the 55th, 77th, and 79th Pursuit squadrons
of the 20th Pursuit Group at Selfridge Field, Michigan, and
the 21th, 34th, and 70th Pursuit Squadrons of the 35th Pursuit
group which trained on P-40s prior to being issued with P-39s.
Foreign air forces were beginning
to take notice of the P-40, and in May of 1940, the Armee de
l'Air of France placed an order for 140 H-81As (export model
of the P-40).
Only 200 of the initial P-40
order were actually completed as P-40s. Serials were 39-156/280
and 40-292/357 (c/ns 13033/13232). In September of 1940, the
remaining 324 aircraft of the initial order had their delivery
deferred to enable Curtiss to expedite the delivery of the 140
French-ordered H-81As. The first export aircraft had actually
been completed in French markings in April of 1940. However,
none of these machines actually reached France before the June
1940 Armistice, and the contract was taken over by the Royal
Air Force as Tomahawk I.
16 P-40s were sent to the Soviet
Union after the German invasion.
The P-40 lacked such things
as armor for the pilot, self-sealing fuel tanks, and a bulletproof
windshield, so it was not considered as being suitable for combat.
On October 22, 1942, those P-40s still in USAAF service were
ordered restricted from combat duty and were redesignated RP-40.
War Planes of the Second World
War, Fighters, Volume Four, William Green, Doubleday, 1964.
The American Fighter, Enzo Anguluci and Peter Bowers, Orion
United States Military Aircraft since 1909, Gordon Swanborough
and Peter M. Bowers, Smithsonian Institution Press, 1989.
Curtiss Aircraft, 1907-1947, Peter M. Bowers, Naval Institute
The Curtiss P-40 Tomahawk, Ray Wagner, Aircraft in Profile,
Volume 2, Doubleday, 1965.
Hawk Dynasty: The Curtiss Hawk Monoplanes, Part 2, Ken Wixey,
Air Enthusiast No 72 (1997).