[2] Originally known as XF-106 (a designation later reused for the Convair F-106),[3] the project and its resultant prototype aircraft were redesignated XF-84H,[4] closely identifying the program as an F-84 variant, rather than an entirely new type.

[6] The XF-84H was created by modifying a F-84F Thunderstreak airframe, installing a 5,850 hp (4,360 kW) XT40-A-1 turboprop engine[7] in a centrally-located housing behind the cockpit with a long extension shaft to the nose-mounted propeller.

[10] After manufacture at Republic's plant in Farmingdale, Long Island, the two XF-84Hs were disassembled and shipped via rail to Edwards Air Force Base for flight testing.

It was unsuited to combat due to the engine's 30-minute warm-up time, but the most serious concerns were vibration generated from the 12-foot diameter propeller and mechanical failures of the prop pitch gearing.

The shock wave was actually powerful enough to knock a man down; an unfortunate crew chief who was inside a nearby C-47 was severely incapacitated during a 30-minute ground run.

[17] Coupled with the already considerable noise from the subsonic aspect of the propeller and the T40's dual turbine sections, the aircraft was notorious for inducing severe nausea and headaches among ground crews.

[18] The pervasive noise also severely disrupted operations in the Edwards AFB control tower by risking vibration damage to sensitive components and forcing air traffic personnel to communicate with the XF-84H's crew on the flight line by light signals.

With the likelihood that the engine and equipment failures coupled with the inability to reach design speeds and subsequent instability experienced were insurmountable problems, the USAF canceled the program in September 1956.