Republic XF-91

The wings were built to have considerably more [Vous devez être inscrit et connecté pour voir ce lien] (distance from front to back) at the tip than root, allowing them to generate more lift.

This neatly addressed the problem of Sabre dance by delaying the point of stall on the tip to that of the entire wing.

A side effect of this design was that the tips had more internal room, so the [Vous devez être inscrit et connecté pour voir ce lien] was mounted to retract outward with the wheels lying in the wingtips, using two small tires instead of one larger one.

Another design change was the ability to vary the [Vous devez être inscrit et connecté pour voir ce lien] of the wing as a whole, tilting it up for low speed operations during takeoff and landing, and then "leveling it off" for high-speed flight and cruise.

This allowed the fuselage to remain closer to level while landing, greatly improving visibility.

In keeping with its intended role as an interceptor, the nose was redesigned to incorporate [Vous devez être inscrit et connecté pour voir ce lien], forcing them to move the air intake for the engine from its original nose-mounted position to a new intake below it.

The fuselage was otherwise very similar to the F-84's.

The first prototype did not include the radome, although this was fitted to the second prototype.

Testing and evaluation

The first prototype made its first flight on 9 May 1949, breaking the speed of sound in December 1951.

It was later modified with a small radome for gunnery ranging (although not the "full" radome from the second prototype).

The second prototype included the full radome and chin-mounted intake, but was otherwise similar.

This airframe was later modified to use a [Vous devez être inscrit et connecté pour voir ce lien] for testing. With both the jet and rockets running, the aircraft could reach Mach 1.71, rather respectable for the early 1950s.

Both prototypes completed 192 test flights over the course of five years.

As an interceptor the Thunderceptor was soon eclipsed by designs from other companies, but like the Thunderceptor none of these would go into production.

The [Vous devez être inscrit et connecté pour voir ce lien] decided to wait the short time needed to introduce newer and much more capable designs created as a part of the [Vous devez être inscrit et connecté pour voir ce lien] project.

The Thunderceptor, like the other interceptor designs of the era, had extremely short flight times on the order of 25 minutes, making them almost useless for protecting an area as large as the United States.

The 1954 designs outperformed the XF-91 in speed, range, loiter time, as well as including the [Vous devez être inscrit et connecté pour voir ce lien] and [Vous devez être inscrit et connecté pour voir ce lien] needed for night and all-weather operation.

The era of the dedicated [Vous devez être inscrit et connecté pour voir ce lien]-type interceptor was over.

Survivors

The second prototype, 46-681, had an engine failure during takeoff from Edwards AFB in the summer of 1951.

[Vous devez être inscrit et connecté pour voir ce lien] test pilot [Vous devez être inscrit et connecté pour voir ce lien] escaped from the aircraft just as the tail melted off - total flight time was a mere 90 seconds.

By the time fire apparatus arrived, driving seven miles across the dry lake bed, the tail section had been reduced to ashes. 46-681 was then fitted with a V or "butterfly" tail (more common on [Vous devez être inscrit et connecté pour voir ce lien] of the era) and was flight tested with this configuration.

It was later used at Edwards AFB as a crash-crew training simulator, then scrapped.

The first prototype, serial 46-680, is preserved at the [Vous devez être inscrit et connecté pour voir ce lien].

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Bibliography

• Pace, Steve. Republic XF-91 Thunderceptor Rocket Fighter (Air Force Legends N.210). Simi Valley, Ca: Steve Ginter Books, 2000. [Vous devez être inscrit et connecté pour voir ce lien].
  
• Winchester, Jim. The World's Worst Aircraft: From Pioneering Failures to Multimillion Dollar Disasters. London: Amber Books Ltd., 2005. [Vous devez être inscrit et connecté pour voir ce lien].
  
• [Vous devez être inscrit et connecté pour voir ce lien] and Leo Janos. Yeager: An Autobiography. New York: Bantam Books, 1986. [Vous devez être inscrit et connecté pour voir ce lien].
  
• Yenne, Bill. The World's Worst Aircraft. New York: Dorset Press, 1993. [Vous devez être inscrit et connecté pour voir ce lien].