Hydraulic failure, software blamed in fatal Osprey crash

Marine Corps knew of problem since 1999

hydraulic redesign sought


WASHINGTON - In its final report on the crash of a V-22 Osprey last December, the Marine Corps said yesterday that malfunctioning software caused the aircraft to swerve wildly out of control before plummeting to the ground and bursting into flames, killing all four Marines on board.

The report recommended a battery of new tests, improved inspection regimens and the redesign of the problem-plagued aircraft's hydraulic system before the $40 billion Osprey program would be allowed to proceed.

But the report, whose specific conclusions about the causes of the crash had been expected, did not call for any fundamental changes to the innovative tilt-rotor aircraft, which can take off and hover like a helicopter as well as cruise like an airplane.

Supporters of the embattled program in Congress, the aircraft industry and the Marine Corps cited the report as evidence that the V-22 is aerodynamically sound, contending that the Osprey should be allowed to go into full production. The Marines want to purchase 360 Ospreys to replace Vietnam-era helicopters.

Critics asserted that major questions remain about the cost of maintaining the aircraft as well as its fundamental safety - four Ospreys have crashed in the past 10 years, three causing deaths. The critics said there should be more stringent testing and possibly a more sweeping redesign of the Osprey before the program proceeds.

The V-22 is one of the Pentagon's most beleaguered programs, having experienced two fatal crashes that killed 23 Marines in the past year. The Defense Department inspector general is conducting a criminal investigation into accusations that Marine officers pressured crews at the Osprey's home base in North Carolina to falsify maintenance records.

And a panel of experts, conducting a sweeping review of the Osprey, could propose delaying, scaling back or killing the program. The panel is expected to release its final report this month.

The Marines' report gave a detailed account of the crew's final moments on Dec. 11 as the pilot struggled to control his aircraft even as its faulty computer system was causing it to lose speed and altitude.

Problems began in the night training mission when a hydraulic line in one of the Osprey's two engine casings burst as the aircraft was approaching New River Air Station in North Carolina.

The ruptured line caused warning lights to go off in the cockpit, including one on a computer reset button. The pilot, Lt. Col. Keith Sweaney, pushed that button, a standard procedure that should have resulted in no perceptible change in the aircraft.

But instead of simply resetting the controls, the software changed the pitch of the Osprey's rotors, causing the aircraft to accelerate unevenly.

Not realizing that the reset button was causing the problem, Sweaney punched it as many as 10 times trying to regain control. Instead, the aircraft pitched and rolled like "a bucking bronco," as one analyst put it.

Thirty seconds after the hydraulic line broke, the Osprey stalled and crashed.

The Ospreys have long had problems with their hydraulic lines, which are made of light titanium that cracks easily.

An array of recent reports cited problems with Osprey hydraulic leaks that caused engine failures and fires. Last month, an inspection found that all eight of the Marines' Ospreys had hydraulic problems, the report said.

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