Marines ‘optimistic’ after tiltrotor’s strong performance
The US Marine Corps has released statistics showing the Bell-Boeing MV-22 Osprey tiltrotor cleared nearly all its performance objectives during a three-month operational test and evaluation (Opeval) phase that ended last month. Final judgement on the evaluation will not be known until a Department of Defense evaluation team issues a report expected in late August, but programme officials are very “optimistic”.
The US Navy’s internal evaluation has meanwhile determined that the MV-22 passed Opeval with flying colours and has recommended introducing the aircraft to the fleet.
A positive Opeval report is required from DoD evaluators to clear the project’s next milestone, and the Defense Acquisition Board will meet on 27 September to consider advancing the programme into full-rate production.
Approval is needed by October to enable the V-22’s manufacturers to begin buying long-lead production items ahead of programme ramp-up in fiscal year 2007. The latest Opeval statistics verify the programme’s dramatic turnaround since a disastrous year in 2000, when two fatal crashes sparked doubts about the aircraft’s basic airworthiness and operational test data that found major reliability and maintenance shortfalls.
By contrast, the 2005 statistics show the MV-22 is meeting most maintenance targets and easily beats mission performance goals. However, one noticeable deviation concerns an average repair time twice as long as expected to fix a maintenance problem that caused a mission to be aborted.
But programme officials say the single failure of a proprotor head threw off the statistics because the replacement part took 128 man hours to assemble and that this is not a fair measure of the MV-22’s reliability performance. Other reliability metrics appear to support that assertion. The MV-22 on average was flown for 25.1h before a maintenance failure, beating the USMC’s goal by 8h.
The aircraft needed 7.2 maintenance man-hours for every flight hour, 13h fewer than the USMC’s demands. The eight Block A aircraft used for Opeval achieved a mission capability rate of 78%, which after a total of 10,000 flight-hours is in line with a goal to deliver an 82% rate by the 60,000 flight-hour mark. Lt Gen Michael Hough, USMC assistant commandant, aviation, estimates the MV-22’s per-hour operating costs at around $6,000, making it cheaper to operate than Boeing’s CH-46 Sea Knight and Sikorsky’s CH-53E Super Stallion.
The USMC’s VMX-22 test squadron identified three Opeval deficiencies that the programme must address before the service’s first operational unit can be fielded in early 2007.
The first is a software glitch that prevents the aircraft’s SINGCARS radio waveform from scrambling transmissions across the entirety of 1,000 possible frequencies, while the Osprey’s troop seating and three-point harness system was also found lacking, often becoming entangled in the passengers’ gear.
Correcting the third deficiency will prove harder, since this involves a classified defect found in the APG-39 radar warning receiver which extends to any aircraft using the system. The MV-22 issue can be partially resolved by 2007, but a permanent solution must be developed and funded by the APG-39 programme.
STEPHEN TRIMBLE / JACKSONVILLE
Source: Flight International
