Flying Cat A means that if you respect the flight manual (weight,OAT,performance charts) an average pilot will be able to land or take-off safely with one engine inoperative.
CAT A procedures use international standards (35 ft obstacle clearance...)
A procedure is established for each case by the manufacturer of the aircraft and has been demonstrated in flight
-you have to abort take-off before a decision point and continue take-off after this point
- you have to go around one engine inoperative before a decision point and land after this point
CAT A is not only performed on helipad but also on runways.
On runways you take in account acceleration-stop distance.
Some twins are not CAT A capable the AS 355F1 for example, but the AS 355N is CAT A capable due to is engines
Some twins can fly CAT A but with a reduced weight, the AS 332L max take-off weight is 9000 kg but CAT A take-off max weight is reduced to 8600 kg
Hope i've been clear
Most companies are pretending flying CAT A, they don't, just imagine they have to reduce the passengers/pay-load by 15% to 45% !!!!!!! no way $$$$$$$$
