WASHINGTON — The Marine Corps disciplined two pilots deemed partly responsible for a sequence of mistakes and misjudgments that led to the crash of an MV-22 Osprey aircraft in April, killing 19 Marines.
The action was taken against the pilot and co-pilot of an Osprey that was flying a short distance ahead of the one that crashed while trying to land at Marana airport in Arizona on April 8.
Lt. Gen. Fred McCorkle, the head of Marine aviation, told a Pentagon news conference Thursday that an internal review board concluded that the two pilots of the lead Osprey were partly responsible because they failed to follow the flight plan and put themselves in a position of having to descend too rapidly.
The decision by the pilots of the first aircraft to continue their approach to the airport — instead of pulling up and trying a new, safer approach — despite an excessive rate of descent "resulted in the mishap aircraft chasing (the lead aircraft) into the (landing) area," a summary of the accident investigation report said.
The crews of neither Osprey "recognized the dangerous potential of the flight profile," the summary said.
McCorkle said the two pilots will not be allowed to fly as aircraft commanders of any Marine Corps aircraft for six months, and after that period they will be required to requalify for that designation. He did not identify the pilots and said details of the disciplinary action are "privileged information."
An investigation report summary released by McCorkle said that although the crew of the Osprey that crashed made mistakes, the main cause of the accident was "human factors," not pilot error.
Asked to explain the difference, McCorkle said the pilot and co-pilot of both aircraft had committed "human factor errors."
McCorkle said it appears in retrospect that the pilots should have broken off their approaches to the airport and circled for another landing attempt. As to why they did not, he said he could only speculate that, "as Marines, they were trying to complete the mission."
The sequence of events and mistakes that apparently led to the crash began with both Ospreys arriving at their final approaches to the airport 2,000 feet higher than the mission had called for.
McCorkle said the attention of the co-pilot in the lead aircraft was distracted at a point when the pilot should have begun his descent, and so the descent was begun late at an accelerated rate. The co-pilot apparently dropped a map or some other article in the cockpit and spent 25 seconds searching for it, McCorkle.
The lead aircraft began its descent at an estimated 1,200 feet per minute — far in excess of the maximum recommended rate — and a tail wind estimated at between eight and 15 knots aggravated the problem. The pilot of the second Osprey followed a similar pattern, but at an even faster rate of descent. He apparently fell into an uncontrollable nose dive after making a 15 degree banking maneuver, McCorkle said.
The Osprey is unique in its ability to take off like a helicopter, rotate its propellers 95 degrees and fly like an airplane. A group of four Ospreys were participating in a mock "noncombatant evacuation" exercise at Marana, about 30 miles northwest of Tucson, when the accident occurred.
The too-rapid approach of the second Osprey produced a phenomenon known as "vortex ring state" — essentially a stall, the investigators concluded. The Osprey plunged into a fatal nose dive, killing the crew of four and their 15 passengers.
The crash was the worst aviation disaster for the Marines since 22 were killed in a helicopter crash in South Korea in 1989.
The Marine Corps halted flights of its remaining Ospreys after the April 8 accident, then resumed flying in early June.
The Marine Corps had previously announced that investigators found no evidence of mechanical, engineering or structural flaws in the Osprey. The final report released Thursday affirmed that finding.
The manufacturers — Boeing Co. and Bell Helicopter Textron — are due to deliver 11 Ospreys to the Marines this year. Eventually the Marines are to field 360 of them to replace the corps' Vietnam-era CH-46 helicopters as the primary means of transporting troops into combat from ships offshore.
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On the Net:
Marines' Osprey Web site: www.hqmc.usmc.mil/factfile.nsf/ and follow links
Boeing Osprey Web site: http://www.boeing.com/rotorcraft/military/v22/