Intended Single Engine Operation (ISEO) offers fuel saving potential for twin engine helicopters but the shut-off of one engine implies safety concerns. Due to the restart time of the gas turbine the helicopter will experience a significant loss of altitude which limits the safe envelope where ISEO is applicable. In this paper, an air impingement system, which is capable of reducing the startup time of the engine by about 60 % to 80 %, is investigated experimentally. Different parameter variations are carried out to minimize the amount of air which is necessary to accelerate the engine in order to reduce the overall weight and size of the system. The modifications to the process are elaborated for startup of the engine to ground idle and to flight operation mode. For startup to ground idle the impinged air mass could be reduced by 25 % without having drawbacks in startup time.

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