Why is SE ifr helicopter more difficult to certify than SE ifr airplane? As far as I know many SE airplanes have been certified many years ago, even for commercial air transport now under EASA i.e. Pilatus PC12, TBM900, Piper PA46 .. All single engine turbine with pratt engines PT-6. Why it is so difficult for helicopters? It would solve a lot of problems in our company where in foggy days, and there are a lot of them during winter, we have to use expensive twins.