Originally Posted by
gipsymagpie
No Cat A profiles I think
Sorry that is total rubbish. I was looking at the first version of the supplement. Cat A operations are now permitted.
So big picture, Airbus want to sell more H135T3H. So the engineers look at the stress and fatigue capability of the airframe and give the nod. The flight test team then go and generate the new performance and handling data. The flight envelope is limited (due to either a limited flight test envelope or due to sheer performance limits). For example you are limited to 5000 ft for take and off and landing rather than 16000ft and you have a restricted angle of bank and speed envelope. I suspect those are due to the potential stress loads on the airframe exceeding the engineers red lines.
There is a limit to how far they can take the AUM as if they go beyond 3175kg you would encounter certification issues as the "upgrade" might have to be done on the certification basis of CS-29 rather than CS-27. Not only that but it would probably be the latest version of CS-29 rather than the 1996 version of CS-27 which the original underlying 135 was certified to. Lots of things on the airframe not actually related to AUM increase might have to change. I think Bell 429 had that issue.