WRIGHTSVILLE BEACH, NC (WECT) - While on a May 6, 2016 low-altitude training mission off the coast of Wrightsville Beach, the pilot of a Marine Corps AV-8B Harrier jet heard three distinct "thumps." Moments later, he learned his engine had failed catastrophically, causing his aircraft to plummet into the Atlantic Ocean.
Very little information about the crash was released while the US Marine Corps investigated the incident, which was classified as a "Class A Mishap." WECT recently obtained a copy of USMC's report through a Freedom of Information Act (FOIA) request.
Shortly after takeoff from the Wilmington International Airport, the pilot, who was not injured in the incident, reported an unknown, "unusual" noise in the cockpit at 4:39 p.m.
He noted the noise did not include any violent or noticeable aircraft tremors, shaking, unusual cockpit indications, or warning/caution lights, according to the report. He added the engine seemed to respond correctly to throttle movements, and he was ready to proceed with a flight maneuver planned as part of the training.
But while preparing to attempt the flight maneuver, the pilot relayed to his aircrew a second occurrence of the "thump."
"I don't know what that was, but it scared me," the pilot, whose name is redacted in the report, commented on the inter-flight frequency.
After the second round of troubleshooting, the pilot said he no longer heard the noise and was prepared for the flight maneuver - which he then successfully performed.
Just minutes later, around 4:45 p.m., the pilot radioed "knock-it-off," a term used for flight safety issues, and explained his engine was not operating correctly. Seconds later, the pilot transmitted "I'm out," and ejected from his aircraft, which then crashed into the ocean about two miles offshore.
"I asked the flight if they had anymore suggestions, but I noticed I was getting closer to the water so I made the decision to pull the ejection handle," the pilot is quoted in a statement taken after the crash.
After entering the 69.1-degree water, the pilot retrieved and entered his life raft, and tried to contact the rest of his division.
Although Wrightsville Beach Ocean Rescue arrived first to the scene, an H-60 helicopter from the USS Wasp, a Navy multipurpose amphibious assault ship, recovered the pilot and took him to Camp Lejeune Naval Hospital for treatment.
A fellow pilot witnessed unusual sparks originating from the aircraft's hot nozzles and watched as it descended below 1,000 feet median sea level -- well below the mission's intended level of 4,000 feet, according to the report. He then saw the pilot's ejection, parachute opening, and entry into the water.
The aircraft was fully recovered on June 17, 2016. A post-mishap assessment showed significant damage to the entire airframe and engine, which was attributed to the high-speed water entry impact.
The final computer data received before it went offline revealed the aircraft was at Mach .318 (approximately 242 miles per hour) immediately prior to the crash.
The engineering investigation determined the catastrophic engine failure stemmed from foreign object damage to the seventh stage high-pressure compressor blades. But there was an apparent disagreement on where the object, a 28 threads-per-inch fastener with a 5/16th-inch double hexagon bolt head, that likely caused the failure came from.
"It was determined damage was severe enough to degrade all available stall margin rendering the engine inoperable," the report states.
Although the initial opinion was redacted, subsequent reviews of the report indicate one option considered was the aircraft "ingested" the fastener on the runway at ILM or Marine Corps Air Station Cherry Point. But the AV-8B Fleet Support Team (FST) concluded if this were true, the aircraft would not have been able to generate sufficient power for takeoff.
Instead, the Commanding Officer of the Marine Aircraft Group 14 and the Commanding General of the 2nd Marine Aircraft Wing, who both reviewed the investigation, agreed with the FST's determination that the fastener likely "dislodged from inside a boundary layer door." The FST, however, was unable to determine the exact origin of the fastener.
Total estimated damage costs for the aircraft are $62.8 million, the report states. Additionally, estimated damage costs for an advanced targeting device recovered from the jet are $1.646 million.
Although the report notes the pilot misdiagnosed the noise he heard, it lists several reasons why he continued the flight, including the lack of abnormal revolutions per minute/jet pipe temperature indications or any immediate indications requiring emergency procedures.
"It was reasonable for [the pilot] to continue the flight after the sounds were heard," the report states.
"However, more experience in the aircraft and prudence with a potential malfunction warranted continued troubleshooting or analysis," the document continued.
There was no apparent disciplinary action taken against the pilot, however, he did reportedly violate his squadron's standard operating procedure by not having a video tape in his aircraft's tape recorder.
The report recommends the Commanding Officer re-emphasize the usage of video recording devices across the squadron.
The report also recommends the mishap be used as a case study for low-altitude loss of engine thrust training for all AV-8B pilots.