Republic XF-91 Thunderceptor

Republic Aviation Corporation · United States · first flew 1949 · fighter

The Republic XF-91 Thunderceptor was an experimental mixed-propulsion interceptor combining a General Electric J47 turbojet with four Reaction Motors rocket motors. Its most distinctive feature was its inverse-taper wing, which was wider at the tip than at the root.

Recognition (WEFT)

W — Wings	Mid-mounted, swept
E — Engines	1 × rocket, fuselage-mounted
F — Fuselage	13.18 m fuselage
T — Tail	Conventional

WEFT is AircraftIQ's four-point recognition method — how it works.

Spot it by:

Inverse-taper wing — wider at tip than root — unique among jet fighters
Auxiliary rocket motors in the tail for high-altitude boost
Republic 'razorback' nose intake with a prominent central cone

The inverse-tapered swept wing — noticeably broader at the wingtip — is wholly distinctive. Combined with the nose intake and rocket-equipped tail, the XF-91 is unmistakable.

Specifications

The Republic XF-91 Thunderceptor has a length of 13.18 m (43 ft).
It has a wingspan of 9.517 m (31 ft).
Its maximum speed is 1584 km/h (984 mph).
Typical crew: 1.

Figures are for the representative variant described above; marks differ. See how AircraftIQ sources figures.

History

Developed in the late 1940s as part of USAF experiments into high-altitude rocket-boosted interceptors, the XF-91 first flew in May 1949. Two prototypes were built and extensively tested, becoming the first US fighter to exceed Mach 1 in level flight in December 1952. The project was cancelled as pure jet designs improved sufficiently.

Variants

Only two XF-91 prototypes were built; no production variant proceeded.

Where you'll see it

Strictly an experimental aircraft; it never entered operational service. Both prototypes served as research tools at Edwards Air Force Base.

Related aircraft

AircraftIQ — the aircraft field guide: 4,893 recognition guides, live overhead identification, works offline.