|
XP-40,
P-40A, P-40B, P-40C
Written by Joe
Baugher
The P-40 was the best known Curtiss-Wright airplane of World War II. It
was also one of the most controversial fighters of the war. It was
vilified by many as being too slow, lacking in maneuverability, having
too low a climbing rate, and being largely obsolescent by contemporary
world standards even before it was placed in production. The
inadequacies of the P-40 were even the subject of a Congressional
investigation. It gets regularly included on lists of the worst combat
aircraft of World War 2.
All of these criticisms certainly had some degree of validity, but it is
also true that the P-40 served its country well during the first year of
the war in the Pacific when very little else was available. Along with
the P-39 Airacobra, the P-40 was the only American fighter available in
quantity to confront the Japanese advance during the first year of the
Pacific War. It helped stem the speed of the Japanese advance until more
modern types could be made available in quantity. The P-40 had no
serious vices and was a pleasant aircraft to fly, and, when flown by an
experienced pilot who was fully aware of its strengths and weaknesses,
was able to give a good account of itself in aerial combat. The P-40
continued in production long after later types were readily available,
the numbers manufactured reaching the third highest total of American
World War II fighters, after the Republic P-47 and the North American
P-51.
The P-40 was obsolete by European standards even before the first
prototype flew, and it never did catch up. Its Initial inadequacies in
the form of low firepower and lack of self-sealing fuel tanks or armor
were a reflection of mid-'thirties USAAC requirements which were
outmoded. The P-40 had been developed as basically a low-altitude
close-support fighter under mid-1930s US tactical concepts which
envisaged more need for low-level ground support operations than for
high-altitude interceptions. The military doctrine of the
"ascendancy of bombardment over pursuit" was dominant in 1937
when the P-40 first appeared. This doctrine assumed that the prospect of
high-altitude enemy air attack on the USA was extremely remote, with
coastal defense and ground attack in the defense of US territory being
seen as the the main tasks for any future fighter aircraft. Low-altitude
performance and rugged construction received priority over high-altitude
capabilities.
During the war, the Senate Special Committee to Investigate the National
Defense Program (usually known as the "Truman Committee",
after its chairman, Senator Harry Truman of Missouri) criticized the
P-40 on several accounts, particularly on the original volume purchase
of an inadequate design and its continued production long after later
designs were readily available. However, they finally concluded that
this was not brought about by any undue favoritism to Curtiss.
Some indication of the enormous P-40 production program undertaken by
Curtiss can be assessed by its claim on factory floor space and
manpower. During 1941, the Curtiss Airplane Division expanded its
manufacturing area by 400 percent. The total work force was 45,000. This
expansion included two new plants, one at Buffalo, New York and the
other at Columbus, Ohio, to supplement the original Curtiss plant in
St.Louis, Missouri. At the peak of wartime production, the entire
Curtiss Airplane Division complex of factories was producing sixty
aircraft A DAY!
The origin of the P-40 can be traced back to the Curtiss P-36 (Model 75)
fighter, which was powered by a radial, air-cooled engine. A step in the
direction toward what was eventually to emerge as the P-40 was the
XP-37, which was described in an earlier post. The P-36 design was
reworked to incorporate the Allison V-1710 liquid-cooled V-type engine,
resulting in the XP-37. The XP-37 was equipped with a General Electrc
turbosupercharger, and featured a cockpit pushed very far to the rear.
Thirteen YP-37 service-test aircraft were built, but problems with the
turbosupercharger caused the development of the P-37 to be abandoned in
favor of a less complex and more straightforward conversion of the P-36
for the Allison V-1710 engine.
Realizing that the radial-engined P-36A was at the limit of its
development, Curtiss designer Donovan Berlin got USAAC permission in
July 1937 to install a 1150 hp Allison V-1710-19 liquid-cooled engine
with integral supercharging in the 10th P-36A (Serial No 38-10). This
project was given the company designation of Model 75P, and the USAAC
gave the project a new fighter designation, XP-40.
The XP-40 flew for the first time on October 14, 1938, with Edward
Elliot at the controls. Armament was two 0.50-inch machine guns located
in the upper fuselage deck and synchronized to fire through the
propeller arc, standard armament for US pursuit aircraft at the time.
Wing racks could be fitted for six 20-pound bombs. A small oil cooler
was located beneath the pointed nose. The air intake for the
single-stage supercharger was mounted on top of the engine cowling
between the two machine guns, but during tests it was replaced by a long
cowled intake duct which became characteristic of all the early P-40
production models. Initially, the coolant radiator was placed under the
fuselage aft of the wing, but it was gradually moved forward until it
finally ended up located underneath the extreme nose. The radiator
intake was redesigned to include an oil cooler and two coolers for the
ethylene/glycol engine coolant. The initial XP-40 had a single exhaust
port on each side of the fuselage, but in its final form it had six
separate exhaust ports on each side. The initial XP-40 had inherited
from the P-36 a set of mainwheel fairing plates which covered the
mainwheels when they retracted into their wing wells, but these were
eventually deleted and replaced by two small doors which closed over the
wheel struts upon retraction.
The maximum speed of the XP-40 was 342 mph at 12,200 feet at a gross
weight of 6260 pounds. This was faster than the Hawker Hurricane, but
slower than the Spitfire or the Bf 109E. Empty weight was 5417 pounds,
and fully-loaded weight was 6870 pounds. Range was 460 miles at 299 mph
with 100 gallons of fuel. With 159 gallons of fuel at 200 mph, a range
of 1180 miles was claimed, almost twice that of the contemporary
Hurricane, Spitfire, and Bf 109E. Wingspan was 37 feet 4 inches, wing
area was 236 square feet, length was 31 feet 1 inch, and height was 12
feet 4 inches. The wingspan and wing area were to remain the same
throughout the entire history of the P-40 production run.
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 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 1040 hp
V-1710-33 (C15) engines and provisions 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 added 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 reached in 5.2 minutes. 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.
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-81A
(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. The remaining 324 aircraft of
the order had their delivery deferred to enable Curtiss to expedite the
delivery of the 140 H-81As to France. However, none of these actually
reached France before the Armistice in June 1940, 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, the P-40s still in USAAF service were
ordered restricted from combat duty and were redesignated RP-40.
The P-40A designation was skipped in the initial designation
assignments. However, it was applied retroactively to P-40 Ser No 40-326
when it was converted to a camera-carrying photographic reconnaissance
model at Bolling Field in March of 1942.
The P-40B (Model H81B) differed from the P-40 in having an extra
0.30-inch machine gun in each wing. The engine was still the V-1710-33.
In September 1940, 131 P-40Bs were procured by the Army to replace the
deferred P-40s. Serials were 41-5205/5304 and 41-13297/13327. The first
P-40B flew on March 13, 1941. The P-40B retained the same dimensions of
the P-40, but weight was increased to 5590 pounds empty, 7326 pounds
gross, and 7600 pounds maximum loaded. Because of the additional weight,
the P-40B had an inferior performance to the P-40, maximum speed being
352 mph, service ceiling being 32,400 feet, and initial climb rate being
2860 feet per minute. Normal range was 730 miles, but a maximum range of
1230 miles could be attained at the minimum cruise settings.
The export equivalent of the P-40B was the Tomahawk IIA (Model H81-A2).
They differed from the American version by having the wing guns replaced
by 0.303-inch Brownings. 110 were produced for the RAF. RAF serials were
AH881/990. 23 of these planes were transferred to the USSR, and one
(AH938) went to Canada as an instructional airframe.
The initial P-40 order
was finally completed with 193 P-40Cs (company designation H81-B).
Serials were 41-13328/13520. The first flight of a P-40C was made on
April 10, 1941. The P-40C retained the 1150 hp Allison V-1710-33 engine,
but was fitted with a new fuel system with 134 gallons in new tanks with
improved self sealing. In addition, provisions were made for a 52-gallon
drop tank below the fuselage. The P-40C had a SCR-247N radio instead of
the SCR-283. These additions produced yet another upward crawl in the
weight --- the weights for the P-40C were 5812 pounds empty, 7459 pounds
gross, and 8058 pounds maximum loaded. Consequently, the performance
continued to degrade. Maximum speed was 345 mph at 15,000 feet. Normal
and maximum ranges were 730 and 945 miles respectively. Service ceiling
was 29,500 feet, and initial climb rate was 2650 feet per minute.
Dimensions were wingspan 27 feet 3 1/2 inches, length 31 feet 8 1/2
inches, height 10 feet 7 inches, wing area 236 square feet.
The export equivalent of the P-40C was the Tomahawk IIB (Model H81-A2).
A total of 930 were built. RAF serials were AH991/999 (all to USSR),
AK100/570 (36 to China), AM370/519 (64 to China), and AN218/517.
100 of these planes, unofficially designated H81-A3, were transferred to
China where they were used by the American Volunteer Group --- the
famous "Flying Tigers". 23 went to the USSR, and unspecified
numbers went to Turkey and Egypt. The rest were used extensively by the
RAF and South African Air Force in the North African theatre.
Tomahawk, Flying Tigers, North Africa
Much-rebuilt Tomahawk IIB, recovered from Russia and painted in the
colors of Bob Neale of the AVG. The plane is on display at the Naval
Aviation Museum, Pensacola.
At a very early stage, the Curtiss P-40 attracted the attention of
foreign air forces. On May 10, 1939, the French ordered 140 export
versions of the P-40 for the Armee de l'Air. These aircraft were
designated Hawk 81-A1 by the manufacturer. The Hawk 81-A1s were
identical to the US P-40 except that they had French instruments and
equipment and were equipped with reverse-movement
"French-fashion" throttles. The first of the French-ordered
H81-A1s flew on June 6, 1940, and a few were actually completed with
French markings. However, before any of their H81-A1s could be
delivered, France surrendered. Britain agreed to take over the entirety
of the French order, and gave the H81-A the name Tomahawk I in RAF
service. RAF serials were AH741/840 and AH841/880.
The USAAC had agreed to defer deliveries of their P-40s so that the
Tomahawk Is could be supplied to Britain as soon as possible. The first
Tomahawk Is reached England in September of 1940. The two 0.5-inch
machine guns in the nose were retained, but they were supplemented by
four wing-mounted 0.303-inch Browning machine guns in place of the
7.5-mm FN-Brownings specified by the French. Such was the urgency of
their delivery to Britain that many of the 140 machines still had French
instruments and bore cockpit lettering in French when they arrived.
However, Britain quickly concluded that these planes were not suitable
for combat, since they lacked armor protection for the pilot,
armor-glass windshields, or self-sealing fuel tanks. Nevertheless, since
a German invasion was feared to be imminent, they were actually issued
to several operational squadrons.
However, the Hun never invaded England, and so the Tomahawk Is were used
only for training roles within Britain. Overseas, the first Desert Air
Force squadron to be equipped with Tomahawks was No. 112 which exchanged
its Gloster Gladiators for the Curtiss fighter. No 112 Squadron became
famous for its "shark's tooth" insignia on the engine cowling,
and this scheme was later adopted by the American Volunteer Group in
China. AH774,793, and 840 were sold to Canada for use as instructional
airframes, but they retained their RAF serials.
The Tomahawk IIA (Model H81-A2) was equivalent to the US P-40B. It had
protective armor and externally-covered self-sealing tanks. 110 were
built for the RAF under a direct-purchase contract. It carried two
0.30-inch machine guns in the wings in addition to the two 0.50-in guns
in the fuselage. A British radio was fitted. RAF serials were AH881/990.
AH938 was transferred to Canada as an instructional airframe. 23 of
these planes were transferred to the USSR.
The Tomahawk IIB (Model H81-A2) was generally equivalent to the US
P-40C. It had four 0.303-inch Browning machine guns in the wings in
addition to the two nose-mounted 0.50-in guns. Whereas the Tomahawk IIA
had a British radio, the Tomahawk IIB had US equipment. A total of 930
of these planes were produced in four lots. RAF serials were AH991/999,
AK100/570 (36 of this batch were shipped to China and were selected at
random with no particular sequence), AM370/519 (64 were shipped to
China, selected at random), and AN218/517. They were used extensively by
the RAF and the South African Air Force in North Africa starting on June
16, 1941.
After the German invasion of the USSR in June 1941, one hundred and
ninety-five Tomahawk IIBs were shipped to the USSR, some from the USA,
others selected from the reserve forced based in the United Kingdom in
anticipation of the German invasion which never came. These Russian
Tomahawks went into action on the Moscow and Leningrad fronts in October
1941, and were the first US-built planes to be used by the Russians in
the new battle area. An unspecified number of Tomahawk IIBs were
sent to bolster Turkish neutrality in November 1941. Turkey was supplied
with planes from both the Allies and the Axis during World War II.
The Tomahawk IIs were active in the Middle East from October of 1941
onward. They shared in the strafing of the retreating Axis troops. The
ability of the Tomahawk to absorb an incredible amount of punishment
became almost legendary. They served with Nos 2, 26, 73, 112, 136, 168,
239, 241, 250, 403, 414, 430 and 616 Squadrons of the RAF. They also
served with Nos 2 and 4 Squadrons of the South African Air Force and No
3 Squadron of the Royal Australian Air Force. At low altitudes, the
Tomahawk II was actually superior to the Bf 109, but this advantage
rapidly disappeared when combat took place at altitudes above 15,000
feet. The weight which handicapped the performance of the Tomahawk did
have one tangible benefit --- the rugged structure could absorb a
terrific amount of battle damage and still allow the airplane to return
to base. Although generally outclassed by the Bf 109, the Tomahawk was a
capable fighter in the hands of experienced pilots such as Neville Duke.
Wing Commander Clive Caldwell of the RAAF scored more than twenty
victories while flying a Tomahawk in the Middle East. However, much of
the opposition to the Tomahawk was provided by obsolescent fighter
biplanes (e.g. Fiat CR-42) and underpowered, lightly armed fighter
monoplanes such as the Fiat G-50 of the Regia Aeronautica. It had
difficulty with the more advanced Macchi C-202 Folgore.
100 of the RAF Tomahawk
IIBs were released to China and served with the American Volunteer Group
(AVG) --- the famous "Flying Tigers". Company records list
them as Model H81-A3. The Tomahawk IIB was more-or-less equivalent to
the P-40C, but some sources list the Flying Tiger Tomahawks as being
equivalent to the P-40B. There is confusion on this point.
It is with the Flying Tigers that the P-40 achieved immortality.
Newly-promoted to Brigadier General in the Chinese Army, Claire
Chennault went to the USA in November 1940 to recruit pilots for the
AVG. The AVG came into existence in August 1941. General Chennault
ordered 100 P-40s through a loan from the US government. By the time of
Pearl Harbor, some 80 American pilots were serving with the AVG based at
Kunming and Mingaladon. Contrary to popular understanding, the AVG did
not actually enter combat until AFTER Pearl Harbor. The famous
"shark's teeth" marking did not originate with the Flying
Tigers, but was copied from the markings used by the Tomahawks of the
RAF's No. 112 Squadron in North Africa.
The AVG drew first blood
on December 20, destroying six out of ten attacking Japanese bombers.
When the AVG encountered the Japanese Zero for the first time, they
initially underestimated the maneuverability of their opponent, and they
lost two pilots on December 23. [Actually, the Dec. 20 encounter ended
with three Kawasaki Ki-48 "Lily" bombers shot down and one
force-landed in Vietnam. The retractable-gear aircraft that fought the
AVG were Nakajima Ki-43 Hayabusa fighters, later called
"Oscar" in the west.] It was soon learned that it was wise not
to mix it up with the Zero on a one-to-one basis because of the inferior
maneuverability and climb rate of the Curtiss, but instead to use the
P-40's superior speed and diving ability to advantage. The most
effective tactic against the Zero was a diving pass followed by a rapid
departure from the scene. The P-40 gained a reputation for ruggedness
which enabled many an AVG pilot to return safely home after his plane
was damaged in combat.
|
