Osprey nacelle burns

Washington DC
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The US Marine Corps' Bell Boeing MV-22 Osprey tiltrotor transport has suffered another engine-nacelle fire caused by a hydraulic leak. Described as minor, the incident on 29 March was caused by a recurring problem with a quick-disconnect fitting on a hydraulic line.

A more serious nacelle fire in December was caused by a bearing failure in the engine air particle separator (EAPS), which resulted in one of the 34bar (5,000lb/in2) hydraulic-system lines rupturing, says Col Matt Mulhern, V-22 programme manager.

The USMC is funding a redesign of the EAPS, which incorporates a hydraulic-driven blower, to be retrofitted to MV-22s before their first operational deployment later this year, he says. The redesign includes stronger titanium hydraulic lines.

Anticipating problems with sand ingestion in Afghanistan and Iraq, despite the EAPS, Rolls-Royce is evaluating two erosion-resistant compressor blade coatings for the V-22's T406 engines, Mulhern says. One is the MDS-Prad Technologies titanium nitride coating used in USMC Sikorsky CH-53s.

Bell Boeing, meanwhile, has submitted its proposal for a cost-saving multi-year procurement of 167 Ospreys - 141 MV-22s and 26 US Air Force CV-22s - over five years from 2008. Production would increase from 14 this year to 35 annually under the procurement, says Gene Cunningham, Boeing's deputy programme manager.