Sloppy maintenance culture, several errors caused F-22 to overheat, investigation finds


Multiple maintenance errors, a dangerous unit culture and leadership failure caused an F-22 Raptor to overheat while in the workshop at Nellis Air Force Base, Nev., L last fall, which cost $ 2.7 million to repair, according to an investigative report released on Friday.

The forward fighter, assigned to 422 Test and Evaluation Squadron at Nellis and maintained by 757 Aircraft Maintenance Squadron, suffered a series of oversights and incorrect procedures as the airmen revised the airframe for prepare it for new operational test missions.

Part of the aircraft’s auxiliary powertrain was removed two days before the Oct.30, 2020 crash so airmen could troubleshoot one of the modifications, the Air Force said. This auxiliary unit is an engine that supplies electrical and hydraulic power to an aircraft for ground operations.

But those responsible for maintenance did not properly label the affected circuit breakers with a “REMOVE BEFORE FLIGHT” label or did not add the correct warnings to the aircraft or its digital documents, as required by the repair manual. .

When the incident occurred, the emergency stop switch on the auxiliary power unit was improperly set to “normal,” the service said in a press release Friday. A maintainer turned on the power while the plane was drained, not realizing that an exhaust duct still had to be installed to let out excess hot air.

“Once the [power unit] was started, the hot exhaust gases flowed directly into the exhaust bay rather than being diverted out of the aircraft, ”the Air Force said. “With smoke emanating from the exhaust bay, the maintenance member chose the wrong course of action by inappropriately attempting to run diagnostics and examine the trouble reporting codes. “

This allowed the Raptor to overheat for longer, until another maintainer manually shut off the power source.

“The [F-22] sustained damage to the airframe, systems, wiring, hydraulics and surrounding structure and… exhaust bay components as a result of an overheating event, ”the report revealed. “Temperatures in the exhaust bay reached 600-700 degrees Fahrenheit for less than 10 minutes.”

Several maintenance officials failed to prevent the incident, the report said, including a supervisor who was on hand to check on the work of another airman but failed to correct their mistakes. Investigators also noted that Nellis’ Airmen were distracted by a morale-boosting day with a VIP tour and flight demonstration, causing them to skip certain steps.

Prior to the accident, various airmen carried out inspections for which they were not qualified, did not realize that the exhaust duct needed to be installed, did not correctly complete maintenance documents and put visual reminders of the remaining work on the aircraft, and disagreement on the correct way to remove fuel from the jet.

All but one of the unit’s maintenance technicians who serviced or inspected the aircraft were fully trained and qualified, according to the report.

“At the time of the incident, there was no one officially designated to supervise the [F-22] and its forms beyond standard production staff, ”the report added.

The F-22 had 51 “red X” events in its records, indicating the “most serious condition possible: whether the aerospace vehicle is unsafe, unusable or not airworthy,” according to the report. Still, the jet was towed between the hangars and fueled according to service guidelines.

Maintenance officials correctly noted F-22 exhaust duct installation warnings only about a third of the times when they were removed in the year before the incident, investigators found.

“If the maintenance teams have correctly performed the appropriate maintenance procedures in accordance with [technical order] advice, this incident would not have happened, ”the report said.

Rachel Cohen joined the Air Force Times as a senior reporter in March 2021. Her work has been featured in Air Force Magazine, Inside Defense, Inside Health Policy, the Frederick News-Post (Md.), The Washington Post and others. .


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