WASHINGTON, July 28, 2000 -- Like "links in a chain," many things went wrong in the April 8 crash of an MV-22 Osprey that killed 19 Marines, Marine officials said.
Lt. Gen. Fred McCorkle, chief of Marine Corps aviation, told Pentagon reporters that results of an investigation pointed to human factors as the main culprit. The tilt- rotor MV-22 crashed during a training mission at the airport in Marana, Ariz. Four crewman and their 15 passengers died on impact.
Two aircraft were taking part in a night training exercise out of Yuma Marine Corps Air Station, Ariz. The Marines were conducting noncombatant evacuation maneuvers.
The primary cause of the crash was the pilot descended too quickly -- 250 percent the acceptable rate, McCorkle said. Other contributing factors include an unexpected 8- to 15- knot tailwind and crew deviations from their flight plan, which put them higher than expected.
"Both aircraft arrived at the airport 2,000 feet higher than planned," McCorkle said. "In the Marine tradition of getting the mission accomplished, rather than go around, the Marines decided to accomplish the mission."
Both Ospreys exceeded the accepted rate of descent, but the pilot who crashed was in worse shape because he was trying both to descend and take up position behind his leader from line abreast, the general said. During this maneuver, the pilot dropped his speed to near 40 knots and experienced "vortex ring state," a rotor stall that results in a loss of lift. Attempts to recover worsened the situation and the aircraft crashed, McCorkle said.
The Marine Corps administratively disciplined the pilot and co-pilot of the lead aircraft for failure in judgment. McCorkle said they should have waved off instead of attempting to continue the mission.
The Marine Corps pulled the pilot's and co-pilot's designations as aircraft commanders for six months. They can still fly as co-pilots. After six months, they must requalify as flight commanders, said Marine officials.
Other lessons the Marines learned from the crash include stressing the importance of crew coordination both inside the cockpits and with other aircraft. Corps officials said they will continue to explore the aerodynamic characteristics of the Osprey and the best recovery techniques if an Osprey enters vortex ring state.
McCorkle said the Marines are looking at the possibility of developing a warning system that will recognize unsafe rate of descent/low airspeed conditions. "I personally think this will be very hard to do," he said.
He said he still has the utmost confidence in the Osprey. Current plans call for the Marines to purchase 360 MV-22Bs, the Air Force to buy 50 CV-22A special operations aircraft and the Navy to purchase 48 HV-22Bs.