Grumman’s ‘Ugly Cat’

With the end of World War II the U.S. Navy realized it would need a high performance, general-purpose jet fighter. As usual, it turned to Grumman Aircraft for the new fighter.

Grumman began to develop the aircraft, Design 83, in 1947, but as the Navy’s requirements grew more ambitious — a range of 650 nautical miles and a large radar, with a corresponding increase in weight — it became clear that a normal swept or delta wing would not work.

Grumman first looked at a variable incidence wing, but even that proved to be inadequate, so the company proposed a complicated and heavy (1,900 pounds) variable sweep wing as the only possible solution.

The resulting aircraft, the XF10F Jaguar, was two and a half times as heavy as the jet fighters entering service.

The aircraft was also odd looking. It had a high wing that gave it a hunchback appearance and a horizontal stabilizer was mounted on top of the vertical stabilizer in a “T” configuration.

The wing was also complicated. It could be swept from 13.5 degrees (take-off and landing) to 42.5 degrees for high-speed flight, and it was equipped with swiveling pylons to carry drop tanks, rocket pods or bombs.

To keep weight and complexity down, Grumman decided not to use hydraulic controls but to develop a pitch system that did not require hydraulic power. The result was a horizontal stabilizer fairing with a small pivoting center body that had a delta foreplane at the nose and a larger rear delta main wing mounted behind it.
The delta foreplane was directly controlled by the pilot who used it to maneuver the stabilizer, but at slow speeds with less air over the foreplane’s surface, the control response became increasingly sluggish.

The engine, a single Westinghouse J40 turbojet single turbojet engine fed by cheek intakes, added to the problems.

Unfortunately, the J40 only developed 6,800 pound of thrust rather than the promised 11,000 pounds and had a large number of other problems eventually traced to poor quality control.

The prototype XF10F-1 first flew on May 19, 1952, and flew 32 test flights in the next year. Only one Grumman test pilot, Corwin “Corky” Meyer, flew the Jaguar.
The most challenging area, the wing-sweep mechanism, generally worked well, with one exception. On one occasion, the poorly serviced hydraulic fluid congealed and jammed the wing fully swept back, which would have made the aircraft virtually impossible to land.

However, Meyer had been told by the engineers if this happened the wing would unsweep itself. Fortunately, this is exactly what happened.

Despite its advantages, the variable sweep wing mechanism was heavy and, with the development of larger carriers with angled flight decks and steam-driven catapults, the Navy decided that the swing-wing configuration was unnecessary. In April 1953, the Navy canceled the program, and with it the 112 production aircraft that had been ordered.

Overall, Meyer found the XF10F completely unsatisfactory, though he noted, “It was a fun airplane for me to fly because it had so much wrong with it and gave me plenty to do.”

In a later letter, Meyer said, “An English test pilot made the following complete report about another airplane he had flown, and it fit my total assessment of the Jaguar perfectly: ‘The entrance to the cockpit of this airplane is most difficult. It should have been made impossible.’”

However, the variable sweep wing’s advantages remained. Grumman and the Navy returned to it when suitably powerful engines were available and produced the F-14 Tomcat, immortalized in the movie “Top Gun.”

(Dr. Michel’s articles appear twice a month in the KA. For questions or comments, e-mail Dr. Michel at marshall.michel@spangdahlem.af.mil.)