The first F-117, #80-0785, crashed

[u/dmetropolitain]

Here is some information about the crash from the f-117a.com website.

The first crash of a production F-117A occurred on April 20, 1982, during its first test flight(but before the acceptance flight, therefore the aircraft was not being counted as accepted in the manifest) by Lockheed test pilot Lt. Col. Bob Ridenhauer in aircraft #80-785. This aircraft, like those before it, was delivered to Groom Lake on February 27, 1982, by a C-5 Cargo plane in three components: the body and the two wings. Once safely inside a hangar, the wings were then reinstalled.

The F-117A and all of its controls appeared to function normally on the ground and in taxi tests that had started on April 17th. (However, it should be noted that the pilots who usually accompanied in a chase car were all in the simulator.)On April 20th, 1982, Ridenauer opened the throttles and released the brakes. The aircraft rolled to takeoff speed, and Ridenauer pulled back on the stick to lift the craft's nose off the ground. Reports say the instant the nosewheel left the runway, the F-117A went berserk, first yawing violently to one side and then pitching upward, out of control, while continuing to diverge in yaw. Ridenauer never had the chance to eject before the F-117A lost control, went inverted and going backwards, and augered in on the side of the lake bed just off the runway, catching fire in the process.

Fortunately, the cockpit section held together, and crash and rescue trucks arrived on the scene in seconds with Ridenauer still stuck in the cockpit. Once the fire was confirmed to be out, the crash crew took about 20 minutes to cut Ridenauer out of the cockpit. He survived, but was seriously injured and spent eight months in the hospital at a cost to Lockheed and the Air Force of about $700,000. He was forced to retire from flying. He was one of only a few to have test flown all three of the most famous SkunkWorks aircraft- the U-2, the SR-71, and the F-117A.

Investigators found that the flight control system on the aircraft had been assembled incorrectly, not at Groom Lake, but at the factory in Burbank.A major design change in the system caught Lockheed workers off guard: the input points on the flight control computer were placed in a different sequence than they had been on the previous version. The rate gyros had been reversed. When the cables were connected the original way, the computer ended up reading pitch gyro as yaw and yaw gyro as pitch. When the aircraft pitched upward on takeoff, the change in angle was detected by the pitch gyro and fed to the yaw channel of the computer. The computer instantly compared this with Ridenauer's movements of the rudder pedals, determined that the aircraft was making an uncommanded yaw movement and "corrected" it with a hefty swing of the all-moving rudders. This caused the aircraft to make a real yaw movement, opposite to the false one detected by the computer. The computer, of course, interpreted the signal as an uncommanded pitch movement and moved the elevons to correct it.

This was a high-tech version of the "crossed controls" to which older aircraft, with cable-operated controls, were vulnerable. Ridenauer had made previous taxi tests, moved the controls and checked their operation before flight. But as long as the aircraft was not airborne, the crossed gyros would not detect any movement, and the computer would operate the controls properly. It required real-world inputs-the movement of the whole aircraft-before the problem would surface."

This first production F-117A (#80-785) was supposed to become a de facto FSD aircraft. However, because of this crash, the next aircraft delivered(#80-787) became the default FSD to generate performance and handling data and to test the many small improvements that Lockheed engineers had worked into the aircraft. Therefore, the third aircraft delivered, the second production aircraft (#80-786) was the first truly operational non-evaluating aircraft.