A Marine Corps AV-8B Harrier that caught fire as it was launching from an amphibious ship to conduct strikes on ISIS last year was the victim of an engine failure, the cause of which remains unclear.
In the March 8, 2016, incident, the pilot exited the aircraft unscathed, but the plane itself sustained nearly $63 million worth of damage, plus another $245,000 in ordnance jettisoned to avoid "cooking off" in the heat of the fire, according to an investigation report obtained by Military.com.
The incident occurred around midday as the Harrier, attached to Marine Medium Tiltrotor Squadron 162 (reinforced), readied to take off from the amphibious assault ship Kearsarge in the North Arabian Gulf.
While the aircraft belonged to a Marine Corps squadron, the pilot belonged to the British Royal Air Force and was deployed with the Marines as part of an allied international exchange program, according to the investigation.
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The 29-year-old flight lieutenant had flown the majority of his career in an RAF Hawk T1, a training aircraft, but had amassed more than 326 hours in the Harrier. The investigation determined he was current, capable and healthy, and did nothing to cause the aircraft malfunction.
Moreover, the Marine investigating officer wrote in the mishap report, "[The flight lieutenant] executed all emergency procedures in an exemplary manner by exercising good judgment despite facing unique and unforeseen circumstances."
According to the pilot's own account, summarized in the report, he had completed all final preflight checks and had slammed the throttle to take off from the ship. Then he heard "a massive pop" and felt the aircraft decelerate sharply.
"The aircraft had a lot of momentum, and it ultimately veered to the port side after rolling down the flight deck for about 80 feet," the report states.
At this point, flames were visible on the body of the aircraft, and the firefighting team attached to the Kearsarge was already moving to extinguish the fire.
A Marine gunnery sergeant described the scene in a witness statement.
"I saw the clamshell panels blow upwards and outwards with a large ball of flames right behind it," he said. "A few seconds later, I saw fuel on the deck start spreading underneath the jet and drifting forward to the nose [afterwards, it became known that when the engine let go, part of it ruptured the left hand drop and was the source of the fuel on deck]. At this point, the fuel ignited covering the entire jet nose to aft in fire."
Over the radio, the pilot was told to eject. But he saw he had control of the aircraft and was able to bring it to a stop, according to the report.
So instead, he "safed" his ejection seat, opened the Harrier's canopy, and moved to exit the aircraft that way.
At first, he was hit in the face with firefighting foam and pushed back into his seat. But after several attempts, he was able to climb down from the aircraft and taken for medical evaluation, according to the report.
While the pilot was given a clean bill of health and no other personnel were hurt, the explosion and fire caused damage to two other Harriers on the deck and one $3.6 million LITENING advanced targeting pod, according to the investigation.
Other Harriers that had already launched from the aircraft were diverted to Bahrain after the fire and ordered to jettison their bombs at sea in a designated "drop box."
While the investigation cleared the pilot of any culpability in the incident, it left questions unanswered as to what caused the engine failure, described by the investigating officer as "catastrophic."
The aircraft was found to be properly maintained and within guidelines for operation. Multiple witnesses and the pilot suggested the damage was caused by a problem with a compressor blade.
"The investigating officer was unable to determine what exactly caused aircraft BuNo 165003 to suffer an unexpected and catastrophic engine failure on 8 March 2016," the investigation states. "An Engineering Investigation is warranted and should be conducted by the AV-BB Fleet Support Team (FST) upon the USS Kearsarge's return to the United States."
There were two more significant mishaps involving Marine Corps Harriers in 2016: a May 6 incident in which a Harrier crashed into the water after losing thrust in Onslow Bay, North Carolina, and a Sept. 22 incident in which a Harrier crashed into the ocean off the coast of Okinawa. In both cases, the pilots ejected successfully.
But following the Okinawa crash, all Harriers in Okinawa were ordered to observe an operational pause to ensure the aircraft was safe.
The causes of the two other Harrier mishaps have yet to be made public.
In 2015, the Corps wrapped up an independent readiness review for the aging aircraft that resulted in improvements to the supply chain for parts most likely to be degraded by age, according to Marine officials.
