Grounded Osprey to return to flight testing

V-22 Osprey

WASHINGTON (CNN) -- The V-22 Osprey, an aircraft that can fly like an airplane and land and take off like a helicopter, is going back into flight testing in April after two deadly crashes grounded it for two years, a Pentagon official announced Friday.

The Osprey program has experienced a series of deadly crashes and accusations of covering up other failures. The program has since been in limbo.

"I've had some serious doubts about the safety, reliability and operational suitability of the V-22," said Pete Aldridge, under-secretary for acquisition in the Defense Department. "I personally have still have some doubts, but the only way to prove the case one way or the other is to put the program back into flight testing."

RESOURCES Message board: The U.S. military

The tilt-rotor Osprey has been grounded for about a year following two crashes, one last December that killed four and another the previous April, in which 23 Marines were killed.

In addition, several Marines were disciplined earlier this year for falsifying maintenance records to make the program look like it was ready for full production when it wasn't.

Aldridge said the testing regimen will differ from what had been planned. The new, two-year plan includes new control software and redesigned "nacelles," the wing structure that allows the plane's engines and props to tilt forward and back.

Last December's crash was blamed on a leak in the hydraulic lines in one of the nacelles. Instead of compensating for the leak, which was caused by chafing between the hydraulic and electric lines, control software apparently caused the aircraft to veer out of control, Aldridge said.

The earlier crash was blamed on "vortex ring state," which can cause rotor aircraft to lose control if they descend too quickly. The Dallas Morning News reported Friday that some critics believe the placement of the rotors on the wings makes the Osprey too vulnerable to the phenomenon.

Twenty Ospreys have been built at a cost of nearly $90 million per aircraft. Four have crashed.

The new testing regimen means a revival for the Osprey program, which appeared moribund earlier this year. Congress has approved spending $1.5 billion to purchase nine Ospreys for the Marine Corps and two for the Air Force.

The Ospreys are built by a partnership of Bell Helicopter Textron of Texas and Boeing's helicopter division in Pennsylvania.

The Marines plan to buy some 360 Ospreys. The Navy and Air Force plan to buy about 50 each.

Following the crashes, an independent commission determined that a redesigned Osprey could be operated safely.

In addition to tests involving vortex ring state and the redesigned elements, shipboard compatibility, low-speed hover conditions, combat maneuverability and mid-air refueling will be examined, Aldridge said.

"The flight test effort will be event-driven as opposed to schedule-driven," Aldridge said. "We will not be driven by trying to accomplish something within a certain period of time."

Aldridge said he and the secretary of the Navy will periodically review the flight tests to assess progress.