PAUL LEWIS / WASHINGTON DC
Issue of affordability still threatens programme even though safety concerns have eased
The revived Bell Boeing V-22 Osprey flight test effort is about to enter the most critical phase, exploring vortex ring state (VRS). While criticism by US Undersecretary of Defense Pete Aldridge of the tiltrotor's safety and operational suitability appears to have abated, the question of affordability still remains.
A second development machine at NAS Patuxent River, due to fly shortly, will undertake a 13-month two-phase period of high-rate descent testing. Some of the initial effort will repeat the set-piece tests completed during the 50h of VRS flying conducted in the six months between the accident in Marana, Arizona, in July 2000 and the New River crash the following December. The former was blamed on too high a rate of descent, outside the V-22's flight envelope, resulting in a blade stall and roll.
"Over the next year we intend to conduct a more comprehensive programme of dynamic manoeuvres more representative of what pilots will do to see if these types of manoeuvres near the boundaries trigger the problem. It's going to involve getting the aircraft into where we know VRS occurs and then making multiple control inputs like a real pilot misapplying inputs," says Tom McDonald, V-22 chief test pilot.
The threat of programme cancellation appears to have been lifted in the near-term following a series of visits to the test facility by senior Pentagon officials. "We have said we've not finished doing what we've got to do, so don't start blowing the horn," says Maj Gen Mike Hough, US Marine Corps assistant deputy commandant aviation.
Recent briefings and demonstrations of the V-22 to Aldridge included manoeuvring and pulling g within a tight radius while in helicopter mode, steep approaches and rapid acceleration and transition to aircraft mode. Aldridge has asked for answers to several VRS questions by next May.
Proving the V-22 is safe and reliable by itself may not be enough to save the programme, however. Congressman Curt Weldon, a strong supporter of the Osprey and senior member of the House Armed Services Committee, warns "the big question is no longer can the V-22 do the job, but can we afford all the programmes on the table?"
Source: Flight International
