The Republic F-84 Thunderjet was an American jet-powered fighter-bomber. Primarily flown by the US Air Force from 1947-64, it suffered many issues during its development and early service. That being said, it performed admirably during the Korean War, and was the first aircraft used by the Thunderbirds.
Development of the F-84 Thunderjet
On September 11, 1944, the US Army Air Forces set requirements for a “day fighter.” It would need a top speed of 600 MPH, a combat radius of 850 miles, and be armed with either eight 12.7 mm or six 15.2 mm cannons. These specifications were later adjusted to feature a smaller combat radius of 705 miles and fewer armaments.
Looking to replace the P-47 Thunderbolt, the USAAF placed an order with Republic for three prototypes of the XP-84. Trusting the company’s reputation, the service didn’t inquire with other manufacturers. The first prototype was completed in December 1945, with testing not occurring until February 1946, following delays with acquiring engines. Wind tunnel tests also showed design flaws with the vertical stabilizer at high speeds, and there were concerns over the weight of the aircraft.
A second prototype was produced in August 1946, and the following month set a national speed record by hitting 607.2 MPH. While this showed the XP-84’s performance, focusing on breaking the national speed record, as well as the international one set by the British (which Republic failed to do), set production behind schedule.
Work commenced in 1947, with the first F-84Bs entering service by December of that year.
Republic F-84 Thunderjet Specs
The F-84 Thunderjet’s general characteristics included a central air intake at the nose of the aircraft, straight wings with wingtip tanks, a sliding canopy that would later be modified with support struts and a tandem landing gear configuration. At its nose were six .50-caliber M3 Browning machine guns, and, later on, pylons were added under each wing and beneath the center of the aircraft to hold up to 32 rockets, 4,000 pounds of bombs or one Mark 7 nuclear bomb.
The F-84 was powered by an Allison J35-A-29 turbojet engine. The J-35 was the Air Force’s first axial-flow compressor jet engine, and it featured a simple design consisting of an 11-stage axial-flow and single-stage turbine. When paired with the afterburner, it produced 5,600 pounds of thrust.
New variants aim to fix persistent issues
In December 1947, the first F-84B Thunderjets were delivered to the 14th Fighter Group at Dow Field, Maine. Maximum speed and acceleration restrictions were soon placed upon pilots, due to issues involving the wrinkling of the aircraft’s skin – a top speed of Mach 0.8 and no more than 5.5 g of acceleration.
Maintenance issues soon earned the F-84B the nickname, “Mechanic’s Nightmare.” These problems grounded the entirety of the F-84B fleet, and modifications were made to the incoming F-84C. These, however, didn’t prevent the new variant from suffering similar issues, with these aircraft also being grounded.
The introduction of the F-84D saved the fighter-bomber. Having fixed the prior issues, it enjoyed a clear superiority over the Air Force’s other jet fighter, the Lockheed F-80 Shooting Star. Modifications were made to the F-84Bs and -84Cs, which allowed them to re-enter service until their retirement in 1952. The F-84D also retired from service with the Air Force that year, but continued with the Air National Guard until 1957.
The F-84E was introduced in 1950. An improvement on the previous iterations, it was the first truly effective version. These improvements included new avionics and systems, a longer fuselage, strengthening of the wings, the addition of pylons to hold external fuel tanks and retractable ones for rockets beneath both wings.
Despite these improvements, the F-84E’s service was hindered by parts shortages, meaning around half of the fleet remained grounded. It was ultimately retired from service with the Air Force in 1956, with the Reserve following suit the next year. It remained in use with the Air National Guard until 1959.
In 1951, the F-84G entered service. Despite the introduction of inflight refueling capabilities, an improved engine and increased payload capability, it was really no more than a stopgap before the swept wing F-84F Thunderstreak was introduced. The Air Force received 789 units, while other countries acquired over 2,000. The F-84G retired from US service in 1964.
Service during the Korean War
Upon the United States entering the Korean War, it was decided that an F-84 Thunderjet wing would be sent overseas. Arriving toward the end of 1950, they began sorties that December and scored their first air-to-air kill on January 21, 1951. However, this victory came at a cost: the loss of two of the fighter-bombers.
It was clear that the air-to-air combat role should be given to the North American F-86 Sabre, as the F-84 was better suited in a ground attack role. By the conclusion of the war, the aircraft had flown 86,408 sorties, dropped 55,586 tons of bombs and 6,129 tons of napalm, and fired 22,154 rockets. The F-84 was responsible for the destruction of 60 percent of all air-to-ground targets, as well as eight air-to-air kills against Mikoyan-Gurevich MiG-15s.
According to the Air Force, 305 F-84s were lost during the conflict, 249 of which were combat-related.
US Air Force Thunderbirds
On May 25th, 1953, the 3,600th Air Demonstration Team formed, with the purpose of putting on public displays, promoting the Air Force, and showcasing the abilities of the aircraft and the precision flying of their aviators. The first to be selected for this role was the F-84G Thunderjet, and it was used by the Thunderbirds from 1953-55.
The F-84E was also used by the Skyblazers, the lesser-known demonstration team with the US Air Forces in Europe.
Accomplishments of the Republic F-84 Thunderjet
In addition to performing efficiently in combat during the Korean War, the F-84 Thunderjet became the first jet aircraft to successfully perform air-to-air refueling with a converted Boeing B-29 Superfortress.
In 1955, a F-84E became the first aircraft to perform a zero-length takeoff. This involved a solid-fuel booster rocket attached to the underside of the fighter-bomber, which enabled it to takeoff from anywhere, including a trailer.