What happened
On 19 October 2022, an F-35A, tail number 15-5197, crashed at Hill Air Force Base, Utah, during the final stages of a landing approach. The aircraft, operated by the 421st Fighter Squadron under the 388th Fighter Wing, was part of a four-ship formation returning from a training sortie at the Utah Test and Training Range.
As the aircraft was on final approach to Runway 14, it encountered wake turbulence from a preceding aircraft in the formation. This atmospheric disturbance caused the aircraft's air data application (ADA) to receive erratic inputs. The pilot attempted to recover by applying full afterburner power; however, due to the low altitude and airspeed at the time of the encounter, the aircraft could not be regained in controlled flight. The pilot successfully ejected before impact, sustaining minor injuries, while the aircraft was destroyed upon impact.
The investigation
The Accident Investigation Board (AIB) examined flight data from the crash survivable memory unit (CSMU) and mission recordings from other aircraft in the formation. The investigation focused on how the wake turbulence interacted with the aircraft's sensors.
Investigators utilized simulator reenactments at Hill AFB to replicate the flight conditions. The analysis of the air data system (ADS) revealed that the atmospheric disturbance caused the system to exclude readings from the left side multifunction probe and intermittently disregard readings from the right side. This forced the system to transition between primary and backup sources, causing the aircraft's internal assessment of its flight parameters to diverge from actual conditions. Consequently, the flight control system issued incorrect commands to the control surfaces and failed to respond to pilot inputs.
Findings
- The primary cause of the mishap was that the F-35A departed controlled flight due to air data system errors immediately prior to landing, leaving no opportunity for recovery.
- A significant contributing factor was that the pilot did not increase landing spacing from preceding aircraft in accordance with established wake turbulence procedures.
- While the wingman in the formation had received updated weather information indicating that wake turbulence procedures were in effect, this information was not relayed to the rest of the flight, leaving the pilot unaware of the need for increased separation.