Intended Single Engine Operation (ISEO)

Helicopters that are equipped with two or more turboshaft engines for safety reasons, mostly operate in part load conditions. As the specific fuel consumption is reduced with increasing engine load, shutting down one engine in suitable flight envelope areas would cut down fuel consumption significantly and reduce engine operating hours. To account for safety in case of failure of the active engine, the inactive engine is required to restart fast enough to minimize the altitude lost until a stationary flight condition is recovered. Thus a quick start system concept for turboshaft engines has been developed and tested on a test bed in preceding studies.