An MV-22B Osprey takes flight to transport Marines to conduct a tactical recovery of aircraft and personnel training mission during the Amphibious Squadron 5 and 11th Marine Expeditionary Unit Integration. Photo courtesy of the U.S. Marine Corps
Neither pilot error nor aircraft malfunction caused a V-22 Osprey to slam into the deck of an amphibious transport ship in August off the coast of Australia, according to an investigation into the incident that killed three U.S. Marines.
The likely culprit was downwash from the rotors reflecting off the deck of the USS Green Bay back into the rotor arc of the aircraft, causing a loss of thrust, according to a heavily redacted investigation report published by Marine Corps Headquarters May 21.
On the afternoon of Aug. 5, 2017, an MV-22B Osprey assigned to Marine Medium Tiltrotor Squadron 265 of the 31st Marine Expeditionary Unit crashed off the coast of Queensland, Australia during a routine training exercise.
Both pilots and all crew members were found fit for duty, got plenty of sleep the night before and showed no signs of fatigue prior to the routine flight, according to the investigation report.
While descending to the deck of USS Green Bay amphibious transport dock ship with 26 personnel aboard, the Osprey’s left nacelle struck the flight deck of the ship. The Osprey’s fuselage hit the side of the ship near the left nose of the aircraft.
The aircraft slid along the side of the ship until it hit a metal stairway while the left propeller blades repeatedly struck the flight deck “sending large debris flying” which damaged a UH-1Y parked nearby on the deck, according to the report.
The impact with the stairway punched a hole in the cockpit and crushed the cockpit display panel. Hitting the stairway stopped the V-22. It then bounced off the ship’s catwalk, rolled over and fell 30 feet into the ocean. It sank in under five minutes, the report says.
Sailors from the Green Bay launched a rescue operation and recovered 23 of the 26 personnel that were aboard the Osprey. Three Marines onboard were killed. Along with the total loss of the V-22, the Green Bay and the UH-1Y were damaged.
A different MV-22B in a separate mishap Dec. 9, 2015, settled with no power onto the USS New Orleans, which is the same class of ship as the Green Bay. A NAVAIR engineer discovered in both incidents the "presence of recirculated downwash reflecting off the hull of the ship and back into the rotor arc, creating a thrust deficit," according to the report.