A graphic shows the F-35 losing control before crashing at Hill AFB, Utah, in October 2022.
An F-35 lost control and crashed while on approach to Hill AFB, Utah, because it flew into wake turbulence from another Joint Strike Fighter, causing the aircraft’s air data system to provide incorrect inputs—a problem compounded by the pilot not following wake turbulence procedures, a U.S. Air Force investigation shows.
The pilot was able to eject before the crash on Oct. 19, 2022, and the F-35A was destroyed with an estimated loss of $166 million.
It marked the first time in 600,000 flight hours that air turbulence had an impact on the F-35 Air Data System (ADS), the Accident Investigation Board report said.
The F-35A, tail No. 15-5197, was No. 3 of four F-35As flying in formation for a training sortie at Hill. The F-35 was returning to base in a standard formation in a 1-mi. trail of the first two aircraft. On final approach, the pilot reported a “slight burble, or rumbling” from wake turbulence.
“This atmospheric disturbance resulted in erroneous inputs to the air data application (ADA),” the report says. “The erroneous inputs to the ADA resulted in a condition in which the aircraft flight controls did not respond correctly for the actual conditions.”
When this happened, the pilot recognized the aircraft was not responding appropriately, so he selected full afterburner power to try to recover. However, because of the low airspeed and a sideslip flightpath, the pilot was not able to recover and ejected.
The report says an F-35 test pilot was on the ground at the time of the incident and said the F-35 looked normal “before obviously going out of control ... when the oscillations were happening, I did see really large flight control surface movements, stabs, trailing edge flaps, rudders all seem to be moving pretty rapidly like, probably at their rate limits and huge deflections.”
The witness said the jet turned sideways to 30 to 40 deg., far outside its normal flight envelope.
The report says that based on the weather before the flight, the base’s supervisor of flying declared that wake turbulence procedures were in effect, which would require the jets to be more spaced apart. This was passed to the air traffic control tower to include in the automated weather system. Investigators reviewed the mission data video and audio, in which “wake turbulence procedures are in effect” is audible.
However, when a wingman relayed weather information to the pilots ahead of the mission, the statement that wake turbulence procedures were in effect was not relayed to the rest of the formation. The pilot involved in the crash told investigators that he was not aware that wake turbulence procedures were in effect and he planned to land with standard spacing.
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