Effects of the Ship Air-wake on Helicopter Controls during Recovery Operations

Prior to the introduction into service of a new helicopter or ship type, The Royal Australian Navy has a requirement to certify the specific helicopter-ship combination for operations. Part of this certification includes the determination of the Ship Helicopter Operating Limits (SHOLs) via a First of Class Flight Trial (FOCFT). To reduce the risks associated with FOCFTs, DSTO has developed a tool (named the FOCFT risk reduction tool) that uses simulation to predict the potentially high risk conditions during launch and recovery operations from ships as a result of the turbulence created by the ship air-wake. This tool combines Computational Fluid Dynamics (CFD) results with a helicopter flight model and an autopilot to determine the Wind over Deck (WOD) angles that are most likely to affect the controllability (including power requirements) of the aircraft during launch and recovery operations. This paper describes the FOCFT risk reduction tool and its suitability for helicopters and ships in service for the ADF. The results can show combinations of WOD angles and landing spots that may cause lower than anticipated wind speed limits during recovery operations. The analysis can also allow a flight test engineer to assess similar control and power limits for multiple landing spots and hence reduce the planned total number of flight test points.