Reliability issues take helicopter electro actuation technology off UK's Merlin upgrade

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Plans to implement novel helicopter electro actuation technology (Heat) aboard the UK Royal Navy's AgustaWestland EH101 Merlin fleet have been dropped as a result of technical maturity and risk issues.

Lockheed Martin UK Integrated Systems, as prime contractor for the Merlin Capability Sustainment Programme (MCSP), was awarded a £750 million ($1.5 billion) contract by the UK Ministry of Defence in December 2005 to bring 30 Merlin HM1s up to an improved HM2 standard, with options on an additional eight aircraft and mission systems.

MCSP is intended to resolve obsolescence issues in the Merlin aircraft and weapon system through to an anticipated post-2030 out-of-service date, introduce an open-architecture mission system and better configure the aircraft for emerging missions. The first reworked aircraft is due for delivery in 2012, with entry into service following in 2013.

 
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Described as a third-generation fly-by-wire system using brushless electric motor actuators for both the main and tail rotors, Heat was originally developed by AgustaWestland and industry partners BAE Systems and Claverham using a mix of MoD and industry funding.

A test rig was built at AgustaWestland's Yeovil site in Somerset in early 2005 for component ground test, and Merlin air vehicle RN01 was subsequently modified for Heat testing.

According to AgustaWestland, the replacement of simplex mechanical flying control systems with quadruplex electronic and mechanical systems would allow complex hydraulic systems to be removed from the aircraft, reduce weight, cut maintenance costs and improve safety.

The Heat modification was selected for the MCSP programme as it offered the potential to resolve obsolescence issues with the Merlin's existing flight control computer, reduce air vehicle weight and reduce through-life support costs, with production costs to be offset against future cost of ownership savings.

But technology demonstration efforts using RN01 revealed issues concerning the reliability of the main rotor actuators. "The amount and level of ground testing undertaken [on RN01] did not demonstrate the required reliability for Heat to proceed [on MCSP] without adding risk to the programme," says AgustaWestland.

"However, we feel the technology approach is still valid and are continuing to take forward development, at a slower pace, with our industrial partners."

The MoD says: "The retention of Heat as a solution within the MCSP programme was predicated on the programme meeting predefined criteria, associated with technical maturity and risk, by November 2007.

Unfortunately, this was not achieved and an alternate solution to the flight-control computer obsolescence has been adopted."

The fallback solution retains the existing flight-control computer, but will introduce new design, qualification and production embodiment, it adds.