Chanute Air Museum

The Republic F-84F Thunder streak was an American-built swept-wing turbojet fighter-bomber. While an evolutionary development of the straight-wing F-84 Thunderjet, the F-84F was a new design.

In 1949, Republic created a swept wing version of the F-84 hoping to bring performance to the F-86 level. The last production F-84E was fitted with a swept tail, a new wing with 38.5 degrees of leading edge sweep and 3.5 degrees of anhedral, and a J35-A-25 engine producing 5,300 pound-force of thrust. The aircraft was designated IF-96A. It flew on 3 June 1950. Although the airplane was capable of 602 knots (693 mph), the performance gain over the F-84E was considered minor Nonetheless, it was ordered into production in July 1950 as the F-84F Thunder streak. The F-84 designation was retained because the fighter was expected to be a low-cost improvement of the straight-wing Thundered with over 55 percent commonality in tooling.

In the meantime, the USAF, hoping for improved high-altitude performance. Production quickly ran into problems. Although tooling commonality with the Thundered was supposed to be 55 percent, in reality only 15 percent of tools could be reused. To make matters worse, the F-84F utilized press-forged wing spars and ribs. At the time, only three presses in the United States could manufacture these, and priority was given to the B-47 Stratojet bomber over the F-84. The YJ65-W-1 engine was considered obsolete and the improved J65-W-3 did not become available until 1954. When the first production F-84F finally flew on 22 November 1952, it differed from the service test aircraft. It had a different canopy which opened up and back instead of sliding to the rear, as well as air brakes on the sides of the fuselage instead of the bottom of the aircraft. The aircraft was considered not ready for operational deployment due to control and stability problems. Since early aircraft suffered from accelerated stall pitch-up, F-84F-25-RE introduced an all-moving tailplane. A number of aircraft were also retrofitted with spoilers for improved high-speed control. As a result, the F-84F was not declared operational until 12 May 1954.

Operational history

Project Run In completed operational tests in November 1954 and found the aircraft to be to USAF satisfaction and considerably better than the F-84G. However, ongoing engine failures resulted in the entire fleet being grounded in early 1955. Also, the J65 engine continued to suffer from flame outs when flying through heavy rain or snow. As the result of the problems, the active duty phase out began almost as soon as the F-84F entered service in 1954, and was completed by 1958. Increased tensions in Germany associated with construction of the Berlin Wall in 1961 resulted in reactivation of the F-84F fleet. In 1962, the fleet was grounded due to corrosion of control rods. The aircraft were retired from active service in 1964. Stress corrosion forced retirement of ANG F-84Fs in 1971.
Flying the Thunderstreak

The Thunderstreak suffered from the same poor takeoff performance as the straight-wing Thunderjets in spite of having a more powerful engine. In reality, almost 700 pounds-force or 10 percent of total thrust was lost because the J65 was installed at an angle and its exhaust had a prominent kink. On a hot day, 7,500 feet of runway were required for takeoff roll. A typical takeoff speed was 160 knots (185 mph). Like the Thunderjet, the Thunderstreak excelled at cruise and had predictable handling characteristics within its performance envelope. Like its predecessor, it also suffered from accelerated stall pitch-up and potential resulting separation of wings from the airplane. In addition, spins in the F-84F were practically unrecoverable and ejection was the only recourse below 10,000 feet .

With the appearance of the F-105 Thunderchief, the Thunderstreak became known as the Thud's Mother.