Deadly failings that caused US Marine Corps tragedy
Why did a US Marine Corps amphibious assault vehicle sink to the bottom of the Pacific Ocean off California, with nine young military personnel trapped inside? It was, the report said, completely preventable.
The US Marine Corps recently released the results of an investigation into what it describes as an “assault amphibious vehicle (AAV) mishap” that occurred off the coast of California in July 2020. That ‘mishap’ – can it ever be thought of as that – resulted in the death of eight marines and one US Navy corpsman, all aged between 18 and 22.
The tragedy began on the morning of the first day of a scheduled two-week joint US Marine Corps-US Navy training exercise, designed to address some of the operational challenges faced when working together.
Thirteen 26ft (7.94m) AAVs, each crewed by US Navy personnel and carrying a contingent of US marines, set off from the San Antonio-class amphibious transport dock ship, USS Somerset, and headed for San Clemente Island.
Problems from the start…
However, the ill-fated AAV immediately ran into the first of a series of problems when the vehicle drew up onto one of the island’s beaches and significant amounts of oil were discovered leaking from its engine.
Five hours later, having done their best to mend the vehicle and refilling it with more than six gallons of oil, the crew finally set off on their return trip to USS Somerset. They immediately encountered sea conditions that were a great deal rougher than forecast or permitted by the mission’s no-go standards.
“We began rocking back and forth really hard,” a surviving marine later told investigators. “There was so much water coming through the hatches it felt as though it was raining.”
Electrical and transmission failure
By now the 26-ton AAV was taking on water through several points – including an improperly installed headlight and the intake and exhaust grills.
Eventually, having once again become drastically low on oil, the transmission failed, sending the engine into an idle and causing the AAV to stop dead in the water. When the rising water level engulfed the generator, the electrics failed, crippling the bilge pumps and the radio communications system.
With the water inside the vehicle now reaching calf height, the vehicle commander moved to the top of the AAV and started waving a blue and white chequered ‘November’ flag to indicate his vehicle was in danger of sinking.
Stock image. The USS Somerset returning to port (Credit: Shutterstock)
Delayed rescue
However, no safety boats had been deployed that day to assist with the exercise.
The men inside the AAV prepared for evacuation in darkness, using their mobile phones as torches.
Instead, it took 20 minutes for another AAV to eventually arrive to help – by which time the stricken AAV had been sinking for around 45 minutes.
With the emergency lighting system also now defunct, the men inside the AAV prepared for evacuation in darkness, using their mobile phones as torches.
The two AAVs then collided with each other – causing the disabled AAV to veer broadside into the swell.
“I remember the men in the back of the vehicle just looking up at me before I got knocked off the AAV by a wave” the vehicle commander said later.
As the waves swept across the vehicle, seawater poured in through the open hatch. The vehicle rose up, nose high, then sank backwards into the ocean.
Maintenance failures, safety, and training at fault
The comprehensive 2,000-page accident investigation report concluded that the cause of the incident was a combination of “maintenance failures due to a disregard of maintenance procedures, AAV crewmen not evacuating personnel when the situation clearly demanded they be evacuated, and improper training of embarked personnel on AAV safety procedures”.
Other contributing factors were found to be “the material condition of the AAVs, a lack of safety support boats, and insufficient buoyancy provided by personal flotation devices at depth.”
While the flotation devices used on the day were designed to allow a marine carrying full combat gear to float on the surface, buoyancy would have been halved by the time the men were 10m (33ft) below the surface.
The weight of their equipment and the AAV’s quickly increasing depth meant, therefore, that the trapped men could never have reached the surface alive.
All of them were found wearing heavy, small arms protective plates, seven still had their Kevlar helmets on, and two were holding onto their rifles.
The report adds that: “The platoon was assigned AAVs in horrible condition.”
The AAV that sank was 36 years old.
New inquiry launched
Three months after the incident, the Marine Corps relieved two officers of their duties and took “disciplinary action” against seven other personnel whose failures were judged to have contributed to the incident.
Details of what exactly those actions actually were have yet to be released.
The Corps says it has now launched a deeper investigation into the incident to reassess the service’s training, material readiness, and operational oversight.
“The accident investigation report reveals that a confluence of human and mechanical failures caused the sinking and contributed to a delayed rescue effort,” said Lt. Gen. Steven Rudder, commander of Marine Forces Pacific, who signed off the report.
“Ultimately, this tragic mishap was preventable.”
Read the Marine press release.
Dennis O’Neill is a journalist specialising in maritime.