HC, I think it's one failure (fuel line detached) two IFSDs and one with the engine retarded to idle.
Not sure why there would be a need to show compliance with the PC2 exposure requirements, as it can comply with PC2e by using the RFM 'helideck procedures without exposure'.
Notwithstanding that, are you sure that the exposure calculations are based on anything other than engine 'core' failures? I know the operators are supposed to supply the manufacturers with all details of IFSDs, but I think it's the pure 'engine failure' case that is used for the calculations. Perhaps JL can enlighten us?
