CAT and performance classes
Here is a small attempt to sort these ideas out a bit for some of the posters (and perhaps readers) who are trying to sort them out: It isn’t meant to be definitive and is not aimed at those who have a good knowledge of this stuff.
CAT A – is about certification of complex helicopters with more than one engine. The key concept for pilots is stay up capability following an engine failure. Only got one engine? You can’t. So single engine helicopters are never certified CAT A. And neither are some twins; because they don’t meet other design criteria, or because they are pretty rubbish at staying aloft following an engine failure at their certified max weight.
CAT B – not CAT A (not meeting design criteria for certification or having no stay-up capability).
Performance classes – important if you operate where CAT A is broken down into full stay-up capability and stay-up capability once the helicopter has reached a certain speed. Perhaps the best example is offshore operations in Europe, such as the take-off from a platform:
Performance class 1 – stay-up capability (and the ability to climb) following an engine failure after the take-off decision point (no need to ditch), or a safe landing before (land back on the platform).
Performance class 2 – stay-up capability (and the ability to climb) following an engine failure once the aircraft has reached a certain airspeed, or a forced landing before (you’ll have to ditch).Until you reach that speed there is “exposure”.
So CAT A, Performance Class 1 is the gold standard (for this particular risk). A properly defined and flown procedure means the aircraft can suffer an engine failure at any stage of the flight and the outcome should be no risk to aircraft or occupants.