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The F-84F “Super Hog” Might Have Been Its Own Worst Enemy

The Republic Thunderstreak bridged the gap from Thunderbolt to Thunderchief

On May 12th 1954 the Republic F-84F Thunderstreak went into operational service with the United States Air Force (USAF). The F-84F was Republic’s answer to the North American F-86 Sabre. The F-84F was a development of the earlier straight-winged F-84 Thunderjet. When first designed it was believed that more than half of the tooling for the swept-wing F model would be the same as that used to build the Thunderjet. In reality it turned out only 15 percent of the tooling could be reused to build Thunderstreaks.

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The F-84F was equipped with swept wings and tail surfaces- a departure from the previous F-84E. The initial prototypes (designated XF-96A) were powered by a single Allison / General Electric J35-A-25 turbojet engine. Republic test pilot Otto Haas first flew the Thunderstreak on June 3rd 1950. Although the F-84F was supposed to perform considerably better than its straight-winged predecessors, in actual practice the performance gains were considered minor.

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That didn’t stop the USAF from ordering the aircraft, now designated F-84F, into production during July of 1950. The F-84F didn’t exactly go straight into service though. Those four years between first flight and service introduction were used to solve several design and performance deficiencies. The Wright J65 turbojet engine replaced the original J35, adding nearly 50% more thrust but availability of the engine was a challenge and the fuselage had to be modified to fit the larger J65.

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The first production F-84F flew for the first time on November 22nd 1952. The production aircraft had a revised canopy arrangement, relocated airbrakes, and still had bugs that needed to be resolved. The Thunderstreak went through changes intended to improve stability and control. A new one-piece horizontal stabilizer (stabilator) and added spoilers got the F-84F into service. The problems didn’t end there.

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During November of 1954 USAF operational testing, dubbed Project Run In, were concluded. By then the F-84F was actually found to be better than the straight-winged E and G models by a considerable margin. Pilots reported that the aircraft was stable and easy to fly. But the Thunderstreak just couldn’t catch a break. Engine problems were both frequent and serious; serious enough in fact to ground every F-84F during early 1955. The J65 engines were flaming out when the airplanes flew through heavy precipitation.

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Equipped with six 50 caliber machine guns and capable of delivering up to three tons of bombs or rockets, the F-84F never used any of its combat capabilities while in service with the USAF. A front-line fighter-bomber that can’t get off the ground won’t last in front-line service for long. Thunderstreaks were removed from active duty squadrons beginning in 1955. They were replaced primarily by North American F-100 Super Sabres. All remaining F-84Fs were being flown by Air National Guard (ANG) and Air Force Reserve (USAFR or AFRES) squadrons by mid-1958.

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The squadrons still flying F-84Fs were called up for the Berlin Crisis in 1961- largely because they were equipped with the Low-Altitude Bombing System (LABS) for delivery of a single Mark 7 atomic bomb. But it was soon found that Thunderstreak control rods were failing due to corrosion. This latest problem grounded the star-crossed jets again in 1962. It took nearly 2,000 man hours to place a single F-84F back in operational service. Once fixed yet again, the Thunderstreaks soldiered on for nearly another decade, the last of the ANG examples finally being relegated to the boneyard in 1971.

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The Fighter Conveyor (FICON) program of the 1950s paired a specially modified F-84F, designated the RF-84K, with the Convair B-36 Peacemaker bomber. The concept envisioned that the fighter, armed with the atomic bomb instead of the B-36, would hitch a ride to the target in the Peacemaker’s bomb bay. The B-36 would release the smaller aircraft near the target, where it would bomb the target and then get a ride back to friendly territory after re-mating with the B-36. The concept was better than the actual practical application, and the concept never got past the experimental stage.

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The reconnaissance version of the F-84F, the RF-84F Thunderflash, came about by accident as much as any other reason. The second YF-84F prototype was built with air intakes located in the wing roots. This arrangement was not acceptable for the F-84F, but some wise soul realized that cameras, and several of them, could be installed in the nose of a Thunderstreak configured in such a manner. The RF-84Fs suffered from the same performance, power plant, and corrosion problems as the F-84Fs. They were finally retired by their ANG operators and replaced by RF-101 Voodoos in 1972.

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The USAF Aerial Demonstration Team, the Thunderbirds, flew the straight-winged Republic F-84G Thunderjet as their first performance aircraft. They switched quickly to the F-84F in 1955 and flew the Thunderstreak for 91 performances. Even the Thunderbirds turned their backs on the F-84F. After only one show season flying them, the Thunderbirds transitioned to the North American F-100C Super Sabre.

Republic Aviation built a total of 2,112 F-84Fs. General Motors built an additional 599 airframes. 1,301 of these Thunderstreaks were operated by Belgium, China (Taiwan), Denmark, France, Germany (West), Greece, Italy, the Netherlands, Norway, and Turkey as part of the Military Assistance Program (MAP). The United States Air Force / Air Force  Reserve / Air National Guard operated the other 811 F-84Fs. 715 RF-84F Thunderflashes were built and 386 of those were delivered to NATO allies. The last operational F-84F variants were the RF-84F Thunderflashes flown by Greece’s Hellenic Air Force. They were retired in 1991.

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Here are five things you might not know about the Republic F-84F Thunderstreak:

  • The first F-84 straight-winged models were nicknamed Hogs. The F-84F, predictably, became the Super Hog. When the Republic F-105 Thunderchief went into service the F-84F was dubbed Thud’s Mother. And, following the nicknaming logic, the F-105 also became known as the Ultra Hog. Those pilots and their nicknames…
  • Have you ever been on an airliner that seemed to be taking an extra extra long time to get off the ground during takeoff? Then you know how every Thunderstreak pilot felt nearly every time down the runway. Because the engine in the F-84F was underpowered to begin with, and it was angled disadvantageously, a hot and high takeoff when mission loaded could easily require 7,500 feet or more of runway roll.
  • Two West German F-84Fs mistakenly crossed into East German airspace on September 14th 1961- smack dab in the middle of the Berlin Crisis. They landed at Tegel Airport in what would soon become known as East Berlin. The two errant German pilots evaded multiple attempts to stop them by Soviet interceptors.
  • On August 16th 1962, two Turkish Air Force F-84Fs shot down a pair of Iraqi Ilyushin Il-28 Beagle bombersThe hapless Iraqis were supposed to be bombing Kurdish rebels but ended up in Turkish airspace instead. This is quite likely the only air-to-air engagement involving the F-84F.
  • In the movie The Hunters (20th Century Fox 1958), F-84Fs stood in for North Korean MiGs trying to shoot down American F-86 Sabre pilot Cleve Saville and his wingmen over Korea.

We hope you enjoy this look at the entire Republic F-84 family of jets.

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Written by Bill Walton

Bill Walton

Bill Walton is a life-long aviation enthusiast and expert in aircraft recognition. As a teenager Bill helped his engineer father build an award-winning T-18 homebuilt airplane in their Wisconsin basement. Bill is a freelance writer, an avid sailor, engineer, announcer, husband, father, uncle, mentor, coach, and Navy veteran. Bill lives north of Houston TX with his wife and son under the approach path to KDWH runway 17R, which means they get to look up at a lot of airplanes. A very good thing.

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