Originally Posted by Ex Douglas Driver
FAR 25.111
Aussie rules (CAO 20.7.1b) say the following:
Note that the 4 engine gross gradient is 1.5% for both the third and fourth segment - not 1.7% as in FAR/JARs. Anyone know why the difference?
This actually makes sense... Both agree on 1,2 % for twins (perhaps because airports are designed around this assumption?), but the required climb gradient for trijets and quads is different.
FAA and JAA require 1,5 % from trijets and 1,7 % from quads. CAO is satisfied with 1,4 % for trijets and 1,5 % for quads.
Trijets and quadjets can afford to meet the higher one-engine-out performance standards because of their extra engines. But is it really any less safe to operate a trijet or quad with equal engine-out performance to twin, with the same obstacles ahead?
You could argue that the requirement for extra engine-out climb gradient for trijets and quads fails to make best use of the inherent redundancy of having extra engines, imposes unduly heavy restrictions on their payload/fuel capacity and favours inherently less safe twinjet designs.
Do CAO standards favour trijet and quadjet (B747, A340...) use in Australia rather than twins (A330, B777, B787, A350)?