An F-35A Lightning II fighter crashed at Hill Air Force Base, Utah, last October when turbulent air confused its avionics, rendering the jet uncontrollable, an Air Force investigation has found.
The nonfatal crash marks the second time an Air Force F-35A has been destroyed in an accident since the jets began flying in 2012. Its loss cost the Air Force more than $166 million, the service said in a report released Thursday.
The accident unfolded just after 6 p.m. local time on Oct. 19, 2022, as a quartet of F-35As returned to Hill from an “uneventful” training sortie, the report said. The jet that crashed, assigned to Hill’s 421st Fighter Squadron, was approaching the base as the third aircraft in the four-ship formation.
As they prepared to land, the pilot felt a “slight rumbling” of turbulence from the wake of the aircraft in front of him, the report said. The bumpy air caused the F-35′s flight controls to register incorrect flight data, and the jet stopped responding to the pilot’s attempts at manual control.
The pilot tried to abort the landing and try again, but the jet responded by sharply banking to the left. Further attempts to right the aircraft failed, and the pilot safely ejected north of the base. His F-35 crashed near a runway at Hill.
The entire incident lasted less than 10 seconds, the report showed.
The aircraft “looked like a totally normal F-35 before obviously going out of control,” an F-35 test pilot who watched the accident from the ground told investigators. “I did see really large flight control surface movements — [stabilizers], trailing edge flaps, rudders all seem to be moving pretty rapidly.”
Investigators found that the pilot involved in the crash hadn’t followed turbulence procedures in effect that day. That requires airmen to fly farther apart, with at least 9,000 feet between landings.
However, the report noted that the F-35′s flight manual tells pilots to space out their landings by 3,000 feet, and doesn’t specify how far apart they should be in case of turbulence.
Simulations confirmed that the issue stemmed from the jet’s misinterpretation of the flight data, not the physical effects of turbulence itself.
“The F-35 enterprise has over 600,000 flight hours and this is the first known occurrence where wake turbulence had this impact on the air data system,” the report noted.
The Air Force said the likelihood of a similar accident happening again is minimal.
“As with any aircraft accident, we will incorporate the findings from this report as appropriate to improve processes and enhance flight safety across the Air Force,” an Air Combat Command spokesperson said.
The F-35A is the Air Force’s most advanced stealth fighter for aerial reconnaissance, ground strike and air defense missions. The service plans to grow from about 375 to 432 F-35As in 2023, stationed at several bases in the U.S. and overseas.
Rachel Cohen is the editor of Air Force Times. She joined the publication as its senior reporter in March 2021. Her work has appeared in the Washington Post, the Frederick News-Post (Md.), Air and Space Forces Magazine, Inside Defense, Inside Health Policy and elsewhere.