What we learned about stealth technology from the combat career of the F-117.
- By Bill Sweetman
- Air & Space magazine, January 2008
Tech. Sgt. Kevin J. Gruenwald/USAF
(Page 2 of 10)
The discovery of a 1964 paper published by Russian mathematician Pyotr Ufimtsev, which showed that a radar return is proportional to the arrangement of edges of an object, not the size, inspired a new shape of airplane (see “The Invisible Men,” Apr./May 1997). The entire shape was made of flat plates and covered in linoleum-like, radar-absorbent material.
Nobody had any illusions that the resulting airplane would set records for range, speed, or maneuverability, but the compromise was vital to Lockheed’s winning the contract for the Experimental Survivable Testbed, or XST, in April 1976. It would also prove critical in the design of the F-117—and, in the long term, seal its fate.
Air Defense Assassin
In November 1978, after the XST prototypes (renamed Have Blue) had flown, Lockheed was awarded a contract to develop the aircraft, under the code-name Senior Trend. The Pentagon’s leaders had recognized the power of stealth and initiated a secret debate about how to exploit it.
The final decision was to field, as quickly as possible and in complete secrecy, a stealth aircraft designed primarily for one mission: putting a bullet through the brain of the enemy’s air defense system in the first hours of war.
Lockheed would build five development airplanes while starting an initial batch of 20 production aircraft. The goal was to fly the first aircraft in July 1980. The need for speedy design defined the F-117. Its external shape was as close to Have Blue as the designers could get, while achieving a just-acceptable range, altitude, and landing speed.
Overholser believed that it was possible to incorporate curvature on the wings, but he could not prove it. “Very simply, the configuration of the F-117 was entirely designed by radar signature requirements,” engineer Alan Brown summed up in a 2003 paper. “No compromises were made in this respect at all.”
Neither was there time to design parts for the entire jet. The navigation system came from the B-52 bomber. The engines were from the Navy’s F/A-18 Hornet fighter. The infrared targeting system, from Texas Instruments, was assembled from parts of other systems. The F-16 contributed the computers and flight control system. The biggest cockpit display was from the Navy P-3 Orion patrol airplane.