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This plane often came back from combat shot full of holes, their wings
and control surfaces in tatters. On one occasion a pilot, Lieutenant
Chetwood, hit a steel pole after strafing a train over Occupied France.
The collision sliced four feet off one of his wings--yet he was able to
fly back safely to his base in England.
The story of this aircraft began in the summer of 1940. At that time the
manufacturer was building the P-43 Lancer and had plans to
produce a lightweight fighter, designated the P-44 Rocket. In
view of combat experience in Europe, however, the Air Corps decided that
if the United States became involved in the war something larger and
better than the P-44 would be required.
Alexander Kartveli, the companies chief engineer, quickly prepared a
rough sketch of a new fighter. It was a daring concept. He planned to
use the new Pratt &
Whitney Double Wasp , 2,000 h.p. XR-2800-21 eighteen-cylinder
two-row radial engine. It which was largest and most powerful aircraft
engine ever developed in the United States. He also envisioned that his
plane would have eight .50-caliber machine guns and enough armor plating
to protect the pilot from every direction. These features added up to an
airplane weighing about 4,000 pounds more than any existing single-engined
fighter.
Without such power of the new 2,000 h.p. Pratt &
Whitney Double Wasp , Kartveli could see no way of meeting the
performance and load carrying demands being made by the U.S.A.A.F. From
an engineering standpoint, the requirements presented some enormous
problems, but far more problems were presented by the engine. The first
of these was the need for an efficient super-charging duct system that
would offer the least interrupted airflow. Kartveli therefore adopted
the unorthodox method of designing this feature first and then building
up the fuselage around it; the large turbo-supercharger was stowed
internally in the rear fuselage, with the large intake for the air duct
mounted under the engine, together with the oil coolers. Exhaust gases
were piped back separately to the turbine and expelled through a waste
gate in the bottom of the fuselage, and ducted air was fed to the
centrifugal impeller and returned, via an intercooler, to the engine
under pressure. Surprisingly, all this ducting of gases under
temperature and pressure did not prove very vulnerable in combat, for
the fighter was to become renowned for its ability to absorb battle
damage and return home.The new
design was approved, and the manufacturer began work on the first test model.
The XP-47B was ready in just eight months and was taken up for its first
test flight on May 6, 1941. It proved to be an outstanding success, and
was able to do everything Kartveli had hoped, plus more. Its speed of
412 miles per hour was even higher than expected.
The conventional three-bladed propeller could not efficiently utilize
the power of the new engine and a four-bladed propeller was adopted.
Although this propeller was an admirable solution to the power gearing
of the engine, there remained the problem of providing sufficient ground
clearance for its 12-foot diameter. If a conventional undercarriage were
to be employed its suspension would have been too far outboard to permit
the wing installation of the guns and ammunition requested by the
U.S.A.A.F., and therefore Republic had to design a telescopic landing
gear which was nine inches shorter when retracted than when extended.
Numerous other problems were to be faced in absorbing the loads and
stresses which would be imposed when a battery of eight 0.5-in. guns (a
phenomenal heavy armament for that time) was fired simultaneously, and
in providing the necessary tankage for the quantities of fuel stipulated
to make the machine the first true single-engined strategic fighter.
Thus, it was only to be expected that when the first prototype, the
XP-47B, made its first flight, on May 6, 1941, it dwarfed not only its
pilots but all previous fighters and, with a loaded weight of 12,086
lb., turned the scales at more than twice the weight of most of its
contemporaries.
The prototype first took to the air on May 6,1941. Production began and
the plane entered United States Army Air Force service in November 1942,
first becoming operational with the Eighth Air Force stationed in the UK
on April 8,1943. The range was not really good enough for escort duties,
and its maneuverability was poor, but at least it offered a measure of
real protection to the Allied bombers which had previously suffered very
heavy losses.
To increase the tempo of flight development of the XP-47B such leading
test pilots as Colonel Ira C. Eaker were employed, and at one time it
was hoped that the design could benefit from combat testing with the
R.A.F. in the Middle East. Production difficulties caused General "Hap"
Arnold to notify the British Air Ministry, in September 1941, that it
was considered inadvisable to do this until various teething troubles
were eradicated, and an optimistic estimate of May 1942 was established
as a target date for the plane to be combat ready. This was eventually
to prove almost a year out. Numerous problems soon presented themselves
as the XP-47B test program advanced. At altitudes above 30,000 feet
ailerons "snatched and froze", the cockpit canopy could not be opened
and control loads became excessive.
773 production versions were ordered. But this was only the beginning.
Before the war was over, a total of 15,579 planes were built, about
two-thirds of which reached operational squadrons overseas.
When, in January 1943, the U.S.A.A.F.'s
56th Fighter Group arrived in the United Kingdom with its massive
planes, R.A.F.
Spitfire fighter pilots banteringly suggested that their American
colleagues would be able to take evasive action when attacked by undoing
their harnesses and dodging about the fuselages of their huge mounts.
The Thunderbolt was certainly big. In fact it was the largest and
heaviest single engined single-seat fighter ever built! But sheer size
was not to prove detrimental to the Thunderbolt's subsequent operational
career.
The first tasks of the Thunderbolt, which began on April 8, 1943, were
high-altitude escort duties and fighter sweeps in which the new aircraft
acquitted itself well, despite the inexperience of its pilots. It was
soon discovered that the heavy Thunderbolt could out dive any Luftwaffe,
or, for that matter, Allied, fighter, providing a decisive method of
breaking off combat when necessary, but at low and medium altitudes it
could not match the rate of climb or maneuverability of German fighters.
One shortcoming, which was even more marked in other Allied fighters,
was that of insufficient range to permit deep penetration into Germany,
but means were already being sought to add to the 307 U.S. gallons of
internal fuel. At the time of the European debut radial-engined
single-seat fighters were a rarity, the only other such fighter
operational in Europe being the Fw 190A.
To prevent confusion between the two fighters of the opposing sides the
engine cowlings of the Thunderbolts were painted white, and white bands
were painted around the vertical and horizontal tail surfaces--an
appropriate comment on recognition standards appertaining at that time,
as it would seem impossible to mistake the sleek and
beautifully-contoured German fighter for this portly American plane.
By mid-1943 improved planes were becoming available, with external fuel
tanks to increase range and a longer fuselage to improve
maneuverability. Next came the major production version, and then other
versions with more powerful engines, giving a maximum speed of 756 km/h
(470 mph). They were used for anti V1 Flying Bomb duties.
The final version was built primarily for use against the Japanese. The
fastest model was the XP-47J, which did not go into production. On
August 4, 1944, this plane reached a speed of 504 miles per hour.
Production plans were shelved in favor of another development, the
XP-72.
These planes flew more than 546,000 combat sorties between March 1943
and August 1945, destroying 11,874 enemy aircraft, some 9,000
locomotives, and about 6,000 armored vehicles and tanks. Only 0.7 per
cent of the fighters of this type dispatched against the enemy were to
be lost in combat.
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