Originally designated YF-96A and first flying on 3 June 1950, the Thunderstreak was a company-sponsored swept-wing development of the F-84C Thunderjet. Official interest, lukewarm at first, hardened soon after the outbreak of the Korean Way and the type was ordered into production with a designation in the F-84 series and various design improvements, among them the substitution of the Wright 165 (Sapphire) in place of the original underpowered Allison. By August 1957, Republic and General Motors had built 1,410 F-84 's for TAC and SAC (USAF) and 1,301 for various NATO forces.The US Thunderstreaks were relegated to units of the ANG in the early 1960s.

Originally designated YF-96A and first flying on 3 June 1950, the Thunderstreak was a company-sponsored swept-wing development of the F-84C Thunderjet. Official interest, lukewarm at first, hardened soon after the outbreak of the Korean Way and the type was ordered into production with a designation in the F-84 series and various design improvements, among them the substitution of the Wright 165 (Sapphire) in place of the original underpowered Allison. By August 1957, Republic and General Motors had built 1,410 F-84 's for TAC and SAC (USAF) and 1,301 for various NATO forces.

The US Thunderstreaks were relegated to units of the ANG in the early 1960s The Thunderstreak's basic roles were interception or ground attack, but its excellent range also made it a useful escort aircraft.

Republic F-84F Thunderstreak of the Turkish Air Form, circa 1964

Like the Thunderstreak, its range was considerably extended by twin drop-tanks, and the Thunderflash had four 0.50in guns. Of 715 RF-84Fs built, 386 were supplied to Belgium, Nationalist China, Denmark, France, West Germany, Greece, Italy, the Netherlands, Norway and Turkey. The Dutch aircraft were replaced by the F 104 Stairfighter. ANG units in the USA also employed the RF-84F

REPUBLIC F-84 THUNDERJET, THUNDERSTREAK, THUNDERFLASH

Alexander Kartveli and his design team started to explore possible layouts for a jet powered fighter-bomber which might be a worthy successor to the P-47 towards the end of 1944, at the same time that Lockheed and North American were initiating design studies on prototypes which were to result in the P-80 and the P-86. In the early stages,
the Thunderbolt's creator considered the simple expedient of installing a jet engine in the P-47 airframe but he very soon decided to start from scratch again, with a completely new design for a cantilever low-wing monoplane, with straight and laminar flow wing and cantilevered horizontal tailplanes mounted half way up the vertical fin.

Structure was all-metal with a duralumin skin and for the first time in an American jet fighter, the air inlet for the turbine engine was to be located in the nose. The pressurized cockpit was equipped with ejector seat and had a teardrop canopy; a large airbrake was installed in the belly of the plane, below the cockpit.

The USAAF''s Materiel Division liked the look of this aircraft with its classic lines and ordered three prototypes and 400 additional aircraft, designated P-84, in March, 1945. The end of the war caused the cancellation of the remainder of the Thunderbolt production program which left Republic fully committed to this new program, on which its future depended. On February 28, 1946, Major William Lien took off from Muroc Dry Lake (later renamed Edwards AFB) the first XP-84, powered by the 3,7501b (1,701kg) General Electric
5-GE-7 turbojet.

The Thunderjet, as it was called, was the first new American fighter to have its maiden flight after the end of World War and on September 7, 1946, it set a new American speed record, at 612 mph (983km/h), having the world speed record snatched from it by the British Gloster Meteor that same day, over in England.

With victory for the United States and its allies, all existing orders had been suspended but then, on January 15, 1946, the USAAF confirmed its order for 15 YP-84A research aircraft and 85 series P-84Bs. The YP-84A was powered by13 Allison engine instead of the General Electric power plant, had tiptanks and was armed with six .50in machine guns, four mounted in the nose and two in the wings.

The 15 YP-84A aircraft and the third prototype (which were virtually identical) were delivered for evaluation by the user by April, 1947, and the aircraft proved satisfactory all respects. Production of the P-84B, redesignated F-84B in mid-1948, totaled 226 aircraft, lasting from June, 1947, until February, 1948, and the first of these went to 14th Fighter Group (37th, 48th and 49th Squadrons). After a batch of 191 F-94Cs which were identical to the F-84B except for the engine used and for some detail changes and refinements, production switched to 154 F-8413s in 1948: this was a much improved variant, with the new, more powerful J35-A-17D engine, it was followed by 843 of the F-84E longet-range version with stretched fuselage, radar and increased stores and armament provision. One hundred of these F-84Es were the first Thunderjets to enter service with the air forces of America's NATO allies, followed by 1,936 of the series F-84G which had the traditional wing and was the variant built in the largest number. The F-84G was the last unswept wing aircraft deployed by the USAF and was used by Strategic Air Command until 1956, and afterwards by Tactical Air Command for a few years longer; it was more effective than its predecessors, equipped with LABS (LowAltitude Bombing System), flight refuelling probe, autopilot and the ability to carry and deliver bombs with nuclear warheads.

The first Thunderjets to have a taste of battle were the F-84E series aircraft of 27th Fighter-Escort Wing (522nd, 523rd and 524th Squadrons) in December, 1950, in Korea and they were joined during the course of that campaign by the F-84s flown by 49th Group (7th, 8th, 9th Squadrons); 58th (69th, 310th, 311th); 474th (428th, 429th, 430th) in 1951, and 1952. At first the Thunderjets were used to escort bombers but when the swept-wing MiG-15 appeared on the scene, which could outfly all the American fighters, they were used as fighter-bombers to outstanding effect, earning widespread respect for their effectiveness.

The design of the F-84 had originated as far back as 1944 when Alexander Kartveli had started to think about developing a jet version of the P-47 Thunderbolt.. The basic design of the F-84 was completed before the end of that year after a long series of experiments and plans using various power plants which were being developed at that time. The prototype was built round the General Electric TG-180 turbojet (subsequently called J35). and at the beginning of 1945 this design effort was rewarded by an order for three aircraft which were designated XP-84 and for 400 series aircraft.

The first prototype had its maiden flight on 28th February 1946 and the second followed in August. At the end of the test flights, production started off with 25 pre-series models designated YP-84 and subsequently went on to the manufacture of the definitive variant, the F-84B. The new fighter reached units from the summer of 1947 onwards and procurement was 226. The following version was the C model (which first flew in April 1948) which had structural details chanued, and of which 191 were built. In November the following year the first F-84Ds appeared (154 built) which had stronger airframe and more powerful engines. These Thunderjcts were the first to be used in the Korean War where they gave a good account of themselves.

On 18th May 1949 the prototype of the following production variant was fflown, the F-84E (843 built) which was again modified and the fuselage was about 30 cm longer. Finally, in Novemberer 1950, the fifth and last straight-winged-version appeared, the F-84G (3,025 built) which was developed specifically at the request of Tactical Air Command who needed a light fighter-bomber able to deliver tactical nuclear weapons. The Thunderjets were the first single-seaters able to carry out such tasks.

In the following variant, the F-84F, the configuration of the aircraft was drastically changed when a 45' swept wing was adopted; the prototype flew on 5th June 1950 and the first series aircraft (named Thunderstreak) flew on 22nd Novembcr 1952. A total of 2,711 were built which went into service from 1954 onwards and represented the final stage of the design as a straight combat plane. The final version, the RF-84F. was for photo-reconnaissance.

One of only two US swept-wing fighters derived directly from existing straight-wing aircraft to achieve production status (the other being the Grumman F9F Cougar), the Thunderstreak was conceived during a period of acute governmental parsimony towards new warplane development. Stemming from a late-1949 proposal (AP-23M) to mate the fuselage of the F-84E with sweptback surfaces and utilize up to 55 per cent of existing tooling, the project underwent incremental redesign that produced a fundamentally new fighter- bomber retaining no commonality with its precursor. A standard F-84E fuselage fitted with a new wing swept-back 40 deg at quarter-chord and sweptback tail sur faces flew on 3 June 1950 as the YF-96A powered by a 5,300 lb st (2 404 kgp) Allison J35-A-25. This designation was changed to YF-84F on the following 8 September, at which time the name Thunderstreak was adopted.

The first of two further YF-84Fs with the J35-A-25 supplanted by the imported Armstrong Siddeley Sapphire engine flew on 14 February 1951, this having a deeper nose air intake and fuselage to accommodatethe larger turbojet. The third YF-84F which followed had extended wing roots embodying engine air intakes, but these lateral orifices caused substantial thrust losses and were consequently rejected for the series fighter, although subsequently adopted for the tactical reconnaissance RF-84F Thunderflash. As the Wright J65, the Sapphire was licence -manufactured for the series F-84F, the first example of which flew on 22 November 1952 with a YJ65-W-1 engine of 7,220 lb st (3 275 kgp). The -1 power plant equipped the first 275 Thunderstreaks, and a further 100 or so had the improved -1A. These engines then gave place (F-84F-5) to the similarly-rated, but more reliable, J65-W-3 (or Buick-built J65-B-3). The USAF accepted its first F-84Fs on 3 December 1952, these presenting numerous problems, not least of which was inadequate high-speed longitudinal and lateral control. In consequence, initial operational deployment (506th SFW) was delayed until January 1954, but the F-84F remained of limited use as a result of its unsatisfactory engine and other deficiencies. Some of the less pleasant handling characteristics of the Thunderstreak were alleviated by introduction of an all-flying tail (F-84F-25) in 1954, and NATO began to receive this fighter-bomber early in 1955. The F-84F carried a built-in armament of six 0.5-in (12,7mm) M3 guns and was capable of lifting 6,000 lb (2 722 kg) of ordnance externally. Late production aircraft (F-84F-50) received the J65-W-7 (or J65-B-7) engine of 7,800 lb st (3 538 kgp), and the last of 2,348 Thunderstreaks (of which 237 were built by General Motors) was delivered in August 1957.