| The
story of the P-47 began in the summer of 1940. At that time Republic 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, Republic's 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 Republic 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 Thunderbolt, 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 Thunderbolt
first took to the air on May 6,1941. Production began with the P-47B,
which 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 P-47B's 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 Thunderbolt
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 Thunderbolts was 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 Republic P-47 Thunderbolts, 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 P-47B's 307 U.S. gallons of internal fuel.
At the time of the Thunderbolt's 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 the portly Thunderbolt.
By mid-1943
improved P-47Cs were becoming available, with external fuel tanks to increase
range and a longer fuselage to improve maneuverability. Next came the
major production version, the P-47D, and then P-47Gs, and P-47Ms 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, the P-47N, 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 P-47 development, the Republic
XP-72.
P-47's 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.
|
