F-35 Crash Caused by Wake Turbulence and Flight Control System Error

August 3, 2023

An image from the recently released F-35A accident report shows the flight conditions being experienced by the pilot right before the crash. (Image: Hill Air Force Base)

The October 2022 crash of an F-35A at Hill Air Force Base (AFB), Utah was caused by wake turbulence from a preceding aircraft and erroneous air data inputs to the flight control system, according to a final accident report released by the Air Force about the crash last week. There were no fatalities from the crash and the F-35A was destroyed upon impact, causing a total loss of over $166 million, according to the report.

The mishap flight consisted of four F-35A aircraft, with the mishap aircraft (MA) flying as the number three aircraft in the flight. After an uneventful training sortie, the MA returned to Hill AFB Runway 14, in a standard formation with the number 3 aircraft in one nautical mile trail of the number 1 aircraft. On final approach to landing, the mishap pilot (MP) experienced a slight rumbling to his aircraft due to wake turbulence from preceding aircraft. This air flow disturbance resulted in erroneous inputs to the air data

application (ADA) of the F-35 flight control system. The erroneous inputs to the ADA resulted in a condition in which the aircraft flight controls did not respond correctly for the actual current conditions of the MA.

Recognizing that the MA was not responding appropriately to control inputs, the MP selected full afterburner power to attempt to recover to controlled flight. Due to the low altitude, low airspeed, and sideslip flight path of the MA, the MP was unable to recover the aircraft and initiated ejection. The MP ejected before the MA impacted the ground and was destroyed. The MP landed just north of the base outside the Hill AFB airfield boundary fence and was recovered by emergency responders.

The accident investigation board (AIB) president found, by a preponderance of the evidence, the cause of the mishap was that the MA departed controlled flight due to air data system errors immediately prior to landing and there was no opportunity to recover the aircraft to controlled flight. The AIB President found one significantly contributing factor to the mishap: the MP did not increase landing spacing from preceding aircraft in accordance with wake turbulence procedures.

The MP testified that when he rolled out on final approach, he felt a distinct “burble” (or rumbling) on the MA (Tab V-1.1.5). Most F-35 pilots interviewed for this investigation and the AIB’s F-35 Pilot Member, regularly experience wake turbulence while flying the aircraft (Tabs V-2.1.6, V-4.2.5, and CC-1.2). Based on available data, the MA was in disturbed air, called wake turbulence, for three seconds from 18:08:27L to 18:08:30L (Tab J-1.19).

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