Air Force Accident Investigation Board Clears F135 Engine In Incident

An engine fire aboard an F-35A at Mountain Home AFB in Idaho last September was caused by strong tailwinds, and not because of an issue with the F135 engine on the airplane, according to the Air Force Accident Investigation Board.

Defense News reports that, according to the AIB, the fire started after hot air was forced into the inlets of the jet's power pack. Contributing to the incident were insufficient torque and slow engine rotation speed, causing the airplane to continuously supply fuel to the engine at an increased rate.

According to the report: “During this mishap, however, the fire became uncontained due to the increased amount of fuel added while the engine rotation speed was slowing. Once the uncontained fire started coming out of the aircraft exhaust, the tailwind carried it rapidly along the exterior surfaces of the jet.”

The pilot survived but suffered burns on his head, neck and face.

The incident occurred on September 23. The Air Force said at the time that it had no intention of grounding the fleet, as it believed that the weather or human factors were the root cause of the fire. No modifications to the aircraft have been planned by the F-35 joint program office.

The investigators said in the report that the aircraft systems performed as designed. But they also said more could have been done to prevent the mishap.

In a statement of opinion on the investigation, AIB president Col. Dale Hetke wrote "[Integrated power pack] and engine start issues with a tailwind were known prior to the incident. However, the publications were written and communicated in such a way that the F-35A pilot community had only vague awareness of the issue. This vague awareness led to inadequate training for engine starts with a tailwind.”

(Image from file)

FMI: Original Report