In 1951 Republic began private venture develop¬ment of a single seat tactical fighter bomber which the company anticipated would be a successor to the F 84F Thunderstreak. The F-105 Thunderchief, or company model AP-63. Alexander Kartveli’s design team originally intended a straight fuselage for the craft but, after seeing NACA data assembled by Richard Whitcomb, was won over by the wasp-waist or ‘area rule’ configuration which enhanced transonic flight performance. At first intended for the Allison J71 engine and powered in prototype form by the Pratt & Whitney J57, the F-105 attained its successes with the 7802kg thrust Pratt & Whitney J75-P-19W turbojet which provided 11113kg thrust with afterburning. Its mid-mounted wing, swept 60 degrees, and the F-105 stood high on its tricycle gear.

Republic F-105 Thunderchief Article

Development began when two J57-powered YF-105As commenced flying 22 October 1955, soon followed by 15 aircraft designated JF-105B and F-105B for test programmes.

The two 1955 YF-105A, 54-0098 and 54-0099, were service testers with 15000 lb P&W J57 engines. The first flew on 22 October 1955, piloted by Russell M Roth.

The F-105A was not built in favour of the F-105B. Three RF-105A photo-recon version were built in 1956.

Production F-105Bs, long delayed by development problems, began to roll from Republic’s Farmingdale line during 1958 and the USAF accepted its first machine on 27 May 1958. The 335th Tactical Fighter Squadron, temporarily moved to Eglin AFB, Florida, began to work up in the new aircraft only to find that, given its complexity and production slippages, it would not become operational until 1960. Meanwhile, a two-seat strike variant, the F-105C, had reached the mock-up stage but was not built.

Though technical problems persisted and critics were calling the ‘Thud’ a maintenance nightmare, Republic proceeded with the F-105D variant which afforded true, all-weather capability by introducing General Electric FC-5 fully integrated automatic flight fire-control system.

The F-105 has mid-set sweptback wings, sweptback tail surfaces, and a one-piece all-moving tailplane mounted low on the fuselage and with a ventral stabilising fin. The ailerons are used only at low speeds and the main roll control is by five section spoilers forward of the large slotted flaps on each wing. The leading edge is variable-camber. ‘Clover-leaf’ air brake is around the exhaust nozzle. Each undercarriage leg has a single wheel, the mains retracting into the wings and nose wheel retracting forward.

The F 105D was powered by a Pratt & Whitney J75 P 19W turbojet engine that develops 26,500 lb thrust (with after¬burning). The F-105D’s fuselage was lengthened by 0.381m. Some 610 were manufactured, and first flight took place at Farmingdale 9 June 1959. The F-105D model soon equipped all three squadrons of the 4th Tactical Fighter Wing at Seymour Johnson AFB, North Carolina. United States Air Forces in Europe (USAFE) were the first overseas recipient of the F-105D, the 36th TFW at Bitburg AB, West Germany re-equipping from 12 May 1961 and the 49th TFW at Spangdahlem soon following. In the early 1960s, with a war growing in Asia, F-105Ds joined the 18th TFW at Kadena AFB, Okinawa.

The F-105D was by now a proven ordnance-carrier. More than 14,000 lb (6,350 kg) of weapons can be carried on under fuselage/wing stations. An internal weapons bay was also provided, and both conventional and nuclear weapons can be deployed. With multiple ejector racks (MER), it could carry an impressive load of external fuel, ECM gear, and eight 340kg bombs on long-range missions. The F-105D could also operate with the Martin AGM-12 Bullpup air-to-surface missile, which was to prove remarkably ineffective against ‘hard’ targets in Vietnam and would be observed bouncing off the Thanh Hoa Bridge. In addition, the F-105D model could carry 70mm rocket pods, napalm canisters and the AIM-9 infra-red (IR) air-to-air missiles, while its integral M61A1 Gatling-type 20-mm cannon proved invaluable in the dual roles of air-to-air combat and air-to-ground strafing. A late-model variant of the F-105D was the F-105D T-Stick II fitted with additional avionics which bestowed all-weather bombing capability, housed in a prominent dorsal fairing extending along the spine of the fuselage to the tail.

The F-105E was another two-seat variant that was not developed.

In May 1962 Republic proceeded with the tandem two seat F-105F. The first aircraft of this type (62 4412), which made its first flight 11 June 1963, was some 900kg heavier as well as slightly longer than earlier Thunderchiefs in order to accommodate the second crewman in tandem. The second F 105F, which flew for the first time on July 25 1963, flew thirty seven demonstration flights from Andrews AFB on August 18th, turn¬around being consistently completed within twenty minutes. The performance of the two seat F 105F is within 3% of the single-seat F-105D.

The two seat F 105G, developed from the F 105F combat/trainer version, carries advanced ‘Wild Weasel’ equipment to detect emissions from enemy radar sites, controlling surface-¬to air missiles, and missiles which can destroy the sites.

143 F-105Fs were delivered and 61 were later reconfigured for the electronic warfare or ‘Wild Weasel’ role in Vietnam, at first under their original designation and later as the F-105G.

After cancelling all airshows for two big summer months the Airforce Thunderbirds reverted back into F-100s in August 1965 to complete the season. They had started in Republic F-105s but a series of accidents throughout the Air Force grounded all Thunderchiefs.

The F-105D, F-105F and F-105G all fought in North Vietnamese skies, the F-104D model fighter-bomber so extensively that over half of the 610 built eventually fell to Hanoi’s air defences. After withdrawal from South East Asia in 1969-70, the Thunderchief soldiered on in Reserve and Air National Guard units, eventually flying its final sortie in 1984. At one time no fewer than 14 USAF and 11 ANG squadrons operated the type, which was built to the extent of 833 examples. Perhaps because of its complexity, no F-105 was ever exported.

Republic F-105 Experiences

Gallery

F-105B
Engine: 1 x Pratt & Whitney J75-P-5, 25,000 lb
No built: 75

F-105D
Engine: 1 x Pratt & Whitney J75-P-19W, 76.5kN / 26,500 lb reheat
Wingspan: 10.59 m / 35 ft 9 in
Wing area: 35.77 sq.m / 385.02 sq ft
Length: 19.61 m / 64 ft 4 in
Height: 5.97 m / 20 ft 7 in
Max take-off weight: 23967 kg / 52838 lb
Empty weight: 12474 kg / 27501 lb
Fuel capacity: 1000 Imp.Gal
Aux fuel weapons bay: 290 Imp.Gal
Underwing & fuselage fuel: 3 x 375 Imp.Gal
Max. speed: 1208 kt / 2237 km/h / 1420 mph / M2.15 at 36,000 ft
Cruising speed: 508 kt / 940 km/h
Ceiling: 12560 m / 41200 ft
ROC: 34,500 fpm
Range w/max.fuel: 3846 km / 2390 miles
Crew: 1
Armament: 1 x 20mm cannon, M61 Vulcan/1029rds, 6350kg of weapons
Hardpoints: 6
Inflight refuel: yes

The first prototype Republic XP-84 made its maiden flight on 28 February 1946, powered by a General Electric J35 engine.

Fifteen YP-84A were built in 1946 for service trials; 45-59482 to 45-59496.

Dubbed ‘Thunderjet’, the straight-winged F-84 saw operational service in Korea from December 1950, first as an escort fighter to B-29 bombers and then in the ground attack role. The F-84G was developed to carry nuclear weapons for tactical warfare and was used by TAC and SAC; F-84Gs without nuclear weapon delivery systems were supplied to various NATO air forces and no less than 4,457 straight-wing Thunderjets were built.

Although it shared the same generic designation number as the straight-winged F-84 Thunderjet, the Republic F-84F Thunderstreak was essentially a new aircraft. The prototype XF-84F was an F-84E Thunderjet fitted with 40 degree sweptback wing and tail, and longer, faired-in cockpit hood. It was powered by a 5200 lb Allison J-35-A-25 turbojet. When Curtiss-Wright acquired a license to build the Armstrong Siddeley Sapphire turbojet in America, Republic fitted an imported Sapphire in the YF-84F prototype which flew on 14 February 1951. The USAF ordered this aircraft into production, with a Wright-built J65 Sapphire, as the F-84F Thunderstreak.

Republic F-84 Thunderstreak Article

The RF-84F served as the backbone of NATO tactical strike forces, operating with Belgium, France, Italy, Greece, the Netherlands, Turkey and West Germany.

On 10 March 1953, five days after a Polish pilot had defected with his MiG-15 to the Danish island of Bornholm, two Czechoslovakian MiG attacked two American F-84G Thunderjets over Regensburg in Bavaria. One of the Thunderjets was shot down by the 23mm and 37mm cannon of one of the MiGs. The pilot ejected safely over Czechoslovakian territory.

By 1955 the F-84F Thunderstreak was the standard U.S.A.F. fighter-bomber, replacing F-86 Sabres and F-84E and -G Thunderjets. Can carry the tactical atomic bomb, and can be carried itself by GRB-36 “mother-plane”. Versions carried by GRB-36 have anhedral (downswept) tailplane.

Initially conceived by Republic dating 1949, the Thunderstreak was first flown in prototype form as the YF-84F on 3 June 1950, this aircraft using a standard F-84E fuselage with a swept wing and being powered by a single Allison YJ35-A-25 engine rated at 2359-kg (5,200-lb) thrust. Early flight testing of this aircraft very quickly revealed that the performance left a great deal to be desired and it was therefore decided to incorporate the British Sapphire (Wright J65) engine, impetus for the change being largely provided by US involvement in the Korean War, although in the event the F-84F did not see action in that conflict. Adoption of the more powerful engine in turn necessitated some redesign and it was not until late 1952 that the first production specimen made its maiden flight. Altogether 2,711 F-84Fs were built for service with allied nations from the late 1950s onwards.

A specialized photo-reconnaissance derivative of the F-84 known as the RF84F Thunderflash was evolved more or less concurrently, this being most easily recognized by its revised air inlet layout which permitted the battery of cameras to be mounted in the extreme nose section. The RF-84F Thunderflash photo-reconnaissance aircraft had cameras in lengthened nose, only 4 guns, and wing-root air intakes. It too can be carried by GRB-36. The first prototype flew in February 1952. Including the prototype YRF-84F, 716 Thunderflashes were built, almost half of this figure being destined for overseas service under the terms of the Mutual Defense Aid Program, examples being supplied to Italy, Greece, West Germany, Turkey, the Netherlands, Belgium, Denmark, Taiwan, France and Norway.

It has another distinction so far as the USAF is concerned, being the aircraft with which flight refuelling techniques for fighters were developed.

A total of 4457 F-84 “Thunderjet” were built.

The second attempt to use the B 36 as an aircraft carrier took place in 1955 and 1956. Seeking a reconnaissance aircraft with sufficient range to reach the Soviet Union, the USAF came up with FICON, which stood for Fighter In CONvair. By hitching a Republic RF 84 Thunderflash to a B 36, the photo-reconnaissance jet’s range could be extended from 3220 km (2000 miles) to 19,310 km (12,000 miles). Some thought was also given to a nuclear bomb equipped Thunderstreak substituting for the Thunderflash. Twenty five RF 84Fs were modified for parasite duty. On a typical mission the mother ship B 36 would depart from Fairchild Air Force Base, Spokane, Washington to be joined in the air by an RF 84K (as the parasite Thunderflashes were designated) from Moses Lake Air Force Base. The fighter would be hoisted into the B 36’s bomb bay.

The F-84G Thunderjet featured conventional ailerons, elevators, rudder and trailing edge flaps. An air-brake is under the centre fuselage. The tricycle undercarriage has a single wheel on each unit, the mains retracting inward into the wings, and nose-wheel retracts rearward.

Even in the mid-1950s the superiority of the jet powerplant for combat aircraft was questioned by some. A modern technology propeller driven by a turbine (a turboprop) offered high speeds, long endurance and low landing speeds. To test this concept the USAF commissioned two XF-84Hs from Republic.

Powered by the Allison XT-40 coupled turboprops driving a singe supersonic blade propellor, the noise the F-84H made has been described as an ‘unholy shriek’, leading to the nickname ‘Thunderscreech’. Resonance off the ground made groundcrew physically sick. The two aircraft only made a dozen test flights, all but two of which resulted in emergency landings and the USAF refused to accept it for their own tests, cancelling the programme in 1956.

The first XF-84H spent 40 years on a pole at Bakersfield Airport, California, its propeller slowly (and quietly) rotated by an electric motor.

Gallery

F-84E Thunderjet
Fighter-bomber
Engine: 5,000 lb. thrust Allison J35-A-17 turbojet.
Wingspan: 37 ft. 5 in
Length: 38 ft. 5 in
Loaded weight: 18,000 lb.
Max. speed: 630 m.p.h.
Ceiling: over 45,000 ft
Normal range: 1,700 miles
In flight refueling: yes
Armament: 6x.50 in. machine-guns
Bombload: 4 x 1,000 lb. bombs or up to 32 x 5 in. rockets.
Crew: 1

Republic F-84F Thunderstreak
Type: single-seat strike fighter
Powerplant: one 3275-kg (7,220-lb) thrust Wright J65-W-3 turbojet
Maximum speed 1118 km/h (695 mph) at sea level
Initial climb rate 2499 m (8,200 ft) per minute
Service ceiling 14020 m (46,000 ft)
Combat radius, clean 724 km (450 miles)
Ferry range 3444 km (2,140 miles)
Maximum take-off 12701 kg (28,000 lb)
Wingspan 10.26 m (33 ft 7¼ in)
Length 13.23 m (43 ft 4¾ in)
Height 4.39 m(14 ft4¾ in)
Wing area 30.19 sq.m (325 sq ft)
Armament: six 12.7-mm (0.5-in) M3 machine-guns
Bomb load, 2722 kg (6,000 lb)
Crew: 1

RF-84F Thunderflash
Engine: Wright J65-W-7, 7800 lb
Wingspan: 33 ft 7 in
Length: 47 ft 7.75 in
Height: 15 ft
Max speed: 679 mph at SL
Max ROC: 8000 fpm
Service ceiling: 46,000 ft
Max range: 2200 mi
Armament: 4 x .50 in mg

F-84G Thunderjet
Engine: 1 x Allison J35-A-29, 24.9kN / 5600 lb
Wingspan: 11.4 m / 37 ft 5 in
Length: 11.7 m / 38 ft 5 in
Height: 3.8 m / 12 ft 6 in
Wing area: 24.2 sq.m / 260.49 sq ft
Wheel track: 16 ft 6 in
Max take-off weight: 8455-10670 kg / 18640 – 23523 lb
Empty weight: 5033 kg / 11096 lb
Max. speed: 970 km/h / 603 mph
Cruise speed: 775 km/h / 482 mph
Ceiling: 12350 m / 40500 ft
Range w/max.fuel: 1680 km / 1044 miles
Armament: 6 x 12.7mm machine-guns
Bombload: 4500 lb
Crew: 1

XF-84H
Engine: 1 x 5850 hp Allison XT40-A-1 turboprop
Wingspan: 10.18 m / 33 ft 5 in
Length: 15.67 m / 51 ft 5 in
Height: 4.67 m / 15 ft 4 in
Max take-off weight: 8123 kg / 17908 lb
Max. speed: 837 km/h / 520 mph
Crew: 1