A Marine Corps AV-8B Harrier's cross-country training flight on May 6, 2016, was abruptly cut short when the aircraft suffered catastrophic engine failure and crashed in the water off Wilmington, North Carolina, shortly after takeoff.
According to a command investigation newly obtained by Military.com through a Freedom of Information Act Request, the disaster was likely caused by debris damaging the engine -- and the suspected culprit was a screw fastener with a 5/16ths-inch hexagonal bolt head.
The Marine pilot ejected soon after the aircraft's engine failed and was recovered from the water uninjured.
But the mishap totaled more than $64 million in damage for the Corps, including the totaled Harrier and an expensive Litening advanced targeting pod that was mounted on the aircraft.
- Investigation: 'Catastrophic Engine Fire' Totaled Harrier at Sea
- Marine Harrier 'Departed Controlled Flight' Before 2016 Water Crash
- Lifeguard Captain Describes Rescue of Harrier Pilot
The results of the investigation give insight to the military's rigorous policing of foreign objects and debris, or FOD, on flightlines and around aircraft. On ships' flight decks and on runways, military personnel conduct routine "FOD walks" in which they comb the area for even the tiniest bits of debris.
In this case, however, officials found it was unlikely the aircraft engine ingested the screw on the runway at Marine Corps Air Station Cherry Point, North Carolina, or at the Wilmington airport, as the plane would not have been able to generate the power it needed for takeoff.
"[The Harrier fleet support team] believes it is more likely that the fastener had been lodged inside a boundary layer door for an indeterminable amount of time," Col. Thomas Gore, commanding officer of Marine Aircraft Group 14, wrote in a May 2017 endorsement of the command investigation.
According to the investigation, events unfolded fast when things went south for the Harrier.
The aircraft, which belonged to Marine Attack Squadron 542 out of Cherry Point, had been set to conduct a seven-hour, cross-country mission that would continue into May 7. The pilot took off from MCAS Cherry Point the morning of the 6th and landed at the nearby Wilmington airport in preparation for the longer flight.
Departure from Wilmington was normal but, shortly after takeoff, as the aircraft flew over the Atlantic, the pilot heard an unusual "thump" noise.
In an official account given to investigators, the pilot said the noise sounded like the nose-landing gear hitting the nose-gear doors.
Concerned, the pilot did an instrument check. There was a second "thump," and then a third, more powerful noise.
"This time, it was more violent and I felt as if it shook the aircraft," the pilot recalled.
By now, the throttle had also stopped responding.
"I got nothing," the pilot reported via radio. Then, as the aircraft began to descend rapidly, he sent one more message: "I'm out."
The plane went down in the Atlantic about 12 miles southeast of the Wilmington airport. The amphibious assault ship USS Wasp, which was operating in the region, deployed an H-60 helicopter to rescue the pilot, who was then sent to Naval Hospital Camp Lejeune and given a clean bill of health.
The investigation determined the Harrier crash was inevitable once engine thrust was lost and the compressor stalled. It called for further investigation of the object, believed to be a screw, that caused the engine to fail, citing possible changes to maintenance and preflight inspections that might result.
This investigation is the third and final to become public following three major Harrier mishaps that took place in close succession last year.
A Harrier that caught fire as it launched from the amphibious assault ship USS Kearsarge in the North Arabian Gulf on March 8, 2016, was found to have suffered "catastrophic engine failure," though the cause was never pinpointed. A Sept. 22, 2016, crash in which a Harrier went down off the coast of Okinawa was found to have occurred after a series of pilot maneuvers that may have overstressed the aircraft.
The Harrier has been flying since the early 1980s and is slated to be replaced by the F-35B Joint Strike Fighter in coming years.
But the Marine Corps needs the aging platform to fly reliably for a while longer: A plan from the Corps' former head of aviation, Lt. Gen. Jon Davis, changed the F-35 transition schedule to enable the service to retire the embattled F/A-18 Hornet faster.
That means Harrier squadrons will be among the last to transition to the F-35, and the aircraft may continue to fly until as late as 2030.