Merlin Snow and Icing Operations – A Case Study

The Merlin HM Mk1 and HC Mk3 are variants of the EH101 helicopter in service with the United Kingdom’s (UK) Royal Navy (RN) and Royal Air Force (RAF), respectively. As part of an integrated climatic trials programme, the safety of operations in snow and airframe icing environments have been evaluated. Joint trials were conducted by European Helicopter Industries, Agusta-Westland and QinetiQ in 1993 and 1999 on pre-production EH101 aircraft. QinetiQ trials with an instrumented production standard Merlin HM Mk1 were conducted in Canada in 2001 and 2004/5. Using all the trials evidence, recommendations for service use were made in September 2005. This paper provides a brief insight into the hazards and difficulties of operating in the snow and icing environments. The trials strategy leading to the clearances for Merlin HM Mk1 and HC Mk3 to operate in these conditions is detailed. The trials aircraft, aircraft modifications and test instrumentation are described and a summary of the test methods and data analysis are given. This trials programme demonstrated the need for flexibility and adaptability to enable evidence to be gathered to underwrite the widest possible clearances for UK in service use.