A helicopter crash that killed two Camp Pendleton Marines en route to Twentynine Palms earlier this year was caused by a loss of oil pressure and the crew's mistaken belief that a recently replaced sensor had given a faulty reading, it was reported Tuesday.
An improperly installed filter cover and the use of the wrong sealant caused a loss of oil pressure shortly before the 3rd Marine Aircraft Wing UH-1Y Huey helicopter crashed while conducting routine flight operations on the afternoon of Jan. 23, the San Diego Union-Tribune reported.
The Huey's pilot, Capt. Elizabeth Kealey, 32, and copilot, 1st Lt. Adam Satterfield, 25, died from injuries suffered in the crash. They were assigned to Marine Light Attack Helicopter Squadron 169, and were the only two aboard the aircraft.
A subsequent investigation found that oil leaked from the main rotor gear box when the cover of the 40-micron filter assembly came off during the training flight. Oil pressure in the helicopter's main rotor gear box dropped to zero, the rotors stopped and the chopper fell about 200 feet.
Investigators recommended that the Marine who signed off on the improperly installed filter cover that touched off the training mishap should have his inspection credentials suspended, although HMLA-169 was granted waivers to allow its maintainers to inspect the filter without removing it from the fuselage, according to the Union-Tribune.
"It is reasonable to surmise that if the aircraft waiver was never approved and the filter assembly had been previously replaced with the correct sealant, this mishap would never have occurred," the report stated.
Investigators also said the helicopter involved in the crash was held back for scheduled maintenance prior to Kealey and Satterfield heading to Twentynine Palms, which may have played a role in their downplaying the oil- pressure crisis, according to the Union-Tribune. The pressure sensor in the main rotor gear box had been replaced.
A low oil pressure warning went off around 15 minutes before crash. If Kealey and Satterfield had diverted the Huey to Palm Springs or Yucca Valley, they would have been able to land before the aircraft became inoperable, according to the report.