Republic F-84 Thunderstreak
Single-Seat, Single-Engine Jet-Powered Fighter
The Republic F-84 Thunderstreak was an advanced swept-wing development of the earlier, straight-winged F-84 Thunderjet.
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The original F-84 "Thunderjet" originated as a straight-winged jet-powered fighter form in 1947. However, the design, with roots in a wartime (World War 2) United States Army Air Forces (USAAF) requirement of 1944, went through a prolonged period of development, not seeing a first-flight until the war was over in 1946 and only entering service in the viable D-model form in 1949. The type was plagued by engine issues and production delays which nearly derailed this classic American entry from ever seeing service. Like the Grumman F9F "Cougar" jet fighter, the Thunderjet was another American jet-powered straight-winged aircraft to have been evolved into swept-back winged forms - this became the definitive F-84F "Thunderstreak" which, while derived from the original F-84 family line, was essentially an all-new aircraft for what eventually became the United States Air Force (USAF).
Origins of the Thunderstreak lay in work conducted during 1949 around proposal "AP-23M" which sought to develop a high performance jet-powered fighter based on the existing framework of the F-84E Thunderjet. E-models carried the Allison J35-A-17D turbojet engine and supported Rocket-Assisted Take-Off (RATO) cannisters for increased take-off performance while inboard external fuel tanks were carried for improved operational ranges. Beyond this, the airframe was lengthened by over a foot for more internal fuel as well as general streamlining of the fuselage. From this standard was generated some 843 production examples.
With the E-model as a starting point, engineers looked to advanced the design to produce a better high-speed fighter. This involved a complete reworking of the tail surfaces as well as implementation of a new swept-back wing mainplane (given 40-degrees sweepback). Very little, if any, commonality was eventually had with the earlier F-84s and a little more than half of the existing Republic Aviation production equipment could be reused.
With its Allison J35-A-25 turbojet engine of 5,300lb thrust output, the prototype "YF-96A" flew for the first time on June 3rd, 1950 - built from an F-84G (51-1345) production model. The designation was then updated to become "YF-84F" joined by the name "Thunderstreak" before the end of the year. Two more aircraft were then added to the program with the first carrying the dimensionally-larger British-originated Armstrong Siddeley "Sapphire" turbojet engine. Due to its size, the fuselage was modified to accept the Sapphire and a deeper air intake at the nose was introduced. In this guise, the aircraft flew for the first time on February 14th, 1951.
The second of the two went down a much more drastic development road, having a complete assembly added over the nose intake and the intake now split into twin triangular-shaped openings at either wing root. In this form, the aircraft's thrust output tested poorly and was ultimately rejected by USAF authorities as a frontline fighter. However, it was revisited as the YF-84F/YRF-84F to become a dedicated tactical reconnaissance aircraft (the nose section housing camera equipment). In service, this aircraft became the RF-84F "Thunderflash" (detailed elsewhere on this site).
The British Sapphire engine was then adopted for local licensed production as the "Wright J65" and its developmental form, the YJ65-W-1 engine of 7,220lb thrust, assisted its prototype airframe during a first-flight recorded on November 22nd, 1952.
All of this then led to the formal adoption of the "F-84" as the "Thunderstreak" in USAF service and this was followed by 3,482 total units (with General Motors chipping in 237 units of this total). The aircraft was nicknamed as "Super Hog" due to the earlier F-84A being named "Hog". The initial 275 F-model aircraft were equipped with the J65-W-1 turbojet engine and then followed 100 more F-models with the J65-W-1A series powerplant. The J65-W-3 then followed both into production.
Standard armament for the fighter became the American staple of 6 x 0.50 caliber (12.7mm) Browning M3 Heavy Machine Guns (HMGs) and all were installed at the upper nose section. In addition to this, the little fighter could carry upwards of 6,000lb of ordnance, mainly in the form of mainly rockets and conventional drop bombs under the wings. Fuel tanks could be affixed at each wing root for increased operational ranges as needed.
The first F-84F Thunderstreak was taken into American service on December 3rd, 1952 but, like other Thunderjet / Thunderstreaks before them, the type suffered from several issues including handling. An "all-moving" tail was introduced to help with controlling and items like this are what delayed the formal introduction of the F-models until 1954.
As built, the F-84F held a single crewman under a lightly framed canopy aft of the nose intake. Overall length of the airframe reached 43.4 feet with a wingspan of 33.7 feet and a height of 14.4 feet. Empty weight was near-14,000lb against an MTOW of 28,000lb. Maximum speed was 695 miles-per-hour with a range out to 810 miles (twin drop tanks fitted), a service ceiling of 46,000 feet (requiring cockpit pressurization), and a rate-of-climb equal to 8,200 feet-per-minute.
Beyond its major global operator being the USAF, the primary recipient of the new jet-powered fighter became many of America's NATO allies in Europe. This included the Belgian, West German, and Netherlands air forces which began receiving the type as soon as the early part of 1955 (about 852 of the total Thunderstreak production lot found their way to NATO forces in Europe). The final Thunderstreak was delivered during August of 1957. After their usefulness had expired, ex-West German F-84s were sold off to allies Greece and Turkey while the USAF sent their own expiring stock to recipients in Europe and, more locally, to the Air National Guard (ANG). The latter received their Thunderstreaks beginning in July of 1964 and operated them into November of 1971.
Beyond this, the F-84F line produced a pair of XF-84H prototypes fitted with Allison XT40-A-1 turboprop engines and tested under the name of "Thunderscreech" - though these prototypes were not advanced. The YF-84J mark, of which two were built to the standard, were given enlarged nose intakes for better airflow to their General Electric J73 turbojet engine. Flown to a speed of Mach 1.09 on April 7th, 1954, this F-84F potential production standard aircraft was also not advanced.
Beyond the stated operators of the Thunderstreak line, customers also included Denmark, France, Italy, Norway, and Taiwan. Italy flew their Thunderstreaks into 1974. A number of the aircraft remain preserved all over the world at various indoor and outdoor displays - with most survivors located in the United States.