UK Royal Navy's EH101 Merlin fleet flies around corrosion issue

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The UK Royal Navy's five squadrons of AgustaWestland EH101 Merlin HM1 multi-mission helicopters will amass a combined 7,500 flight hours this year, despite suffering a corrosion problem that will require the service's 38 aircraft to undergo tail boom modification work.

Discovery of the issue, which affects an untreated bulkhead that is exposed when the HM1's tail is folded, has required AgustaWestland to design and build a replacement part for each aircraft, and to self-fund the production of two new tail jigs to support the work.

 
© Craig Hoyle/Flight International

The manufacturer expects to complete the modifications within a 12-month period, with the repair covered by its 25-year Integrated Merlin Operational Support (IMOS) contract with the UK Ministry of Defence. Established late last year, the deal is centred on the use of a depth maintenance line for the HM1 and the UK Royal Air Force's 22 Merlin HC3 transports at RNAS Culdrose, Cornwall.

"This [repair] was part of the service, and at no financial cost to the customer," says AgustaWestland's IMOS service manager Neil Cromarty. The fix could have taken three to four years to complete under previous support arrangements, according to military and industry sources, who say the problem has not affected EH101s in use by the RAF or other users.

"We have seen in the first year that IMOS does work, and industry is providing effective support," says Cdr Tony Gray, head of air engineering and operational support at Culdrose. More than 80% of the Merlin's required spare parts are now delivered on time, says the MoD, with this representing a 10% improvement since 2006. The Culdrose line will also be used during the Merlin Capability Sustainment Programme, which will upgrade the RN's aircraft to an improved HM2 standard.

Navy operations involving the Merlin have seen up to 23 of its aircraft deployed this year, performing tasks including monitoring sea lanes in the Gulf region, supporting the interception of drug-running aircraft in Latin America and tracking renewed Russian submarine movements in the North Atlantic. "We are getting immense value out of this aircraft," says Culdrose commanding officer Capt Philip Thicknesse.

The HM1 fleet recorded 6,300 flight hours in 2006-7, and the service expects to log around 10,000h with the type in 2008-9. "This is very much a force in growth," says Cdr Steve Murray, Merlin force commander.