San Diego Union-Tribune


03-Feb-2001 Saturday 

Osprey can't land safely if engines fail, critics say 


WASHINGTON -- The Marine Corps' beleaguered Osprey aircraft may offer some capabilities no helicopter can match, but critics say it lacks one lifesaving feature common to most choppers: the ability to make a soft landing if its engines fail.

"It will not auto-rotate for a safe landing in a power failure, in most situations," Pentagon systems analyst Charles Spinney said, using the technical term for an emergency procedure that has saved hundreds of lives in helicopters over the years.

The Osprey, which can take off and land like a helicopter but flies like a propeller-driven airplane, is the focus of intensifying controversy, partly because of three fatal crashes. Questions about its ability to land softly
when the engines fail could represent another obstacle for an aircraft whose production is jeopardized by safety concerns.

The Marines argue that the Osprey's inability to use its rotors to make a soft landing during an engine failure is not a concern because it is unlikely to lose both engines at the same time and can glide to a safe landing like an airplane if it does.

Spinney and Jon Kettles, a former Army helicopter pilot, however, believe the inability to perform the normal helicopter emergency maneuver increases the danger to the MV-22's crew and passengers.

"If both engines quit, it virtually assures you're going to hurt the people on board," Kettles said.

All commercial helicopters sold in the United States are required to be able to auto-rotate if their engines fail. Virtually every military helicopter has the same ability.

To auto-rotate, a pilot puts the helicopter into a glide so that forward airspeed keeps the rotors spinning even though the engine has stopped. As the helicopter nears the ground, the pilot uses the lift remaining in the spinning blades to slow the descent. If done correctly, the helicopter
touches down relatively softly with little or no forward motion.

The Osprey was not designed to do that, Marine 1st Lt. David Nevers said.

In the helicopter mode, "safety is provided by two extremely powerful engines, either of which can power both rotors," Nevers said.

In about 5,000 hours of testing, the Ospreys have never had one engine fail, let alone two, he added.

If both engines fail, he said, the Osprey can glide to a landing like a normal aircraft. "But we consider that a very remote risk," Nevers said.

Some critics, however, note that the MV-22s are intended to fly troops into combat situations where enemy fire could disable both engines.

Kettles also sees a problem "in the flight profile the Osprey will be in most of the time" -- low and slow while going into or lifting out of a small landing zone.

In that situation, the heavy aircraft would have trouble gliding to a landing slow enough to avoid injuring the people on board, he said.