The Republic F-105 Thunderchief was the first supersonic tactical fighter-bomber developed from scratch. Apart from being the biggest single-seat, single-engine combat aircraft in history, the F-105 was notable for its large internal bomb bay and unique swept-forward engine inlets in the wing roots. The wing was highly swept and incorporated low-speed ailerons and high-speed spoilers for lateral control, and a droop-snoot leading edge.
Known as "the Thud", this greatest of all single-engine combat jets bore a huge burden throughout the Vietnam War, and was a deadly and effective tactical fighter-bomber. A supersonic jet, the Thud is characterized by two unique systems: it is the only jet fighter to refuel from a side-fuselage boom, and was the first jet fighter to employ a Vulcan 20mm "Gatling Gun" cannon. The D-model made more air strikes against North Vietnam than any other US aircraft, and also suffered more losses. During the war, the versatile Thud was also credited with 25 MiG kills.
The F-105 evolved from a project begun in 1951 by Republic Aviation at Farmingdale NY to develop a supersonic tactical fighter-bomber to replace the F-84F. The massive F-105 was intended primarily for nuclear strike missions. Designed from the outset as a fighter-bomber for long-range interdiction missions, the Republic F-105 Thunderchief was a large, heavy aircraft with Mach 2 performance. A unique feature for a fighter was the internal bomb bay intended to house a nuclear weapon.
The prototype first flew on October 22, 1955, but the first production aircraft, an F-105B, was not delivered to the USAF until 1958. After winning a flyoff competition with the North American F-107 in 1956, the F-105 first entered squadron service in 1958. With the designation F-105B came an engine change to a Pratt & Whitney J75-P-3. Other changes were made in this model too, including the use of a unique type of swept-forward air intake to control the shock-wave and introduction of "area rule" on the fuselage. A total of 75 F-105Bs were built.
The F-105D all-weather strike fighter and the two-place F-105F dual-purpose trainer-fighter were also built before F-105 production (833 aircraft) ended in 1964. No "C" or "E" series were produced and "Gs" were modified "Fs" outfitted with extensive electronic countermeasure equipment. F-105G aircraft were nicknamed "Wild Weasels" and specialized in jamming enemy radar and destroying surface-to-air missile sites.
The configuration incorporated a shoulder-mounted 45 sweptback wing with airfoil thickness ratios varying from 5.5 percent at the root to 3.7 percent at the tip. Trailing-edge Fowler flaps together with leading-edge flaps were used to increase the maximum lift coefficient of the wing. Roll control was achieved by shortspan outboard ailerons assisted by upper-surface spoilers. The all-moving horizontal tail was mounted in the low position to aid in preventing pitch-up. Careful fuselage area ruling reduced the magnitude of the drag rise as the Mach number increased from subsonic to supersonic values. A most unusual feature of the aircraft are the two-dimensional variable-area supersonic inlets mounted in the wing-root position. The speed brake was an unusual petal-type arrangement that surrounded the jet nozzle.
The internal bomb bay was designed to accommodate a nuclear weapon. Not long after the F-105 became operational, however, the concept of carrying a nuclear weapon in the aircraft was discarded, and the bomb bay was used to house additional fuel. A six-barrel Vulcan 20-mm rotary cannon was carried in the aircraft, and there were provisions for 12 000 pounds of external armament including bombs, rockets, and missiles. Such a large load could be carried only on short-range missions, however, with a more normal load being 6000 pounds. Combat radius for this load varied from 600 to 800 miles depending on the amount of external fuel carried. The F-105 was provided with all the necessary electronic equipment for full all-weather capability.
Maximum Mach number of the F-105D was 2.08, or 1372 miles per hour, at an altitude of 36 090 feet; at sea level, the maximum Mach number was 1.1, or 836 miles per hour. Normal cruising speed was 584 miles per hour. Sea-level rate of climb was a spectacular 38 500 feet per minute; only 1.7 minutes were required to reach an altitude of 35 000 feet. Ferry range with no war load was 2207 miles. With a maximum gross weight of 52,838 pounds, the F-105D is by far the heaviest fighter so far considered, nearly as heavy as the 55,000-pound, four-engine B- 17 bomber of World War II.
A total of 833 F-105 aircraft were manufactured before production ended in 1964. Extensively used in ground-attack operations in Vietnam, the Thunderchief continued to serve with the USAF for a number of years following the end of the conflict. Last of the F-105's was withdrawn from the Tactical Air Command in 1980, but a few remained in service with the Air National Guard.
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