Hello, I haven't flown ETOPS for a while but while I'm awaiting a new course I had a read through the ETOPS section of our OMA.
When determining the critical fuel scenario it is determined by the most critical of the following scenarios:
- A rapid loss of cabin pressure at the most critical point followed by a descent to a safe altitude as defined by oxygen availability.
- A rapid loss of cabin pressure and a simultaneous engine failure at the most critical point followed by a descent to a safe altitude as defined by oxygen availability.
- An engine failure at the most critical point and descent to one-engine-inoperative cruise altitude and diversion at one-engine-inoperative cruise speed.
I can understand and apply this concept but I just can't think (I'm probably missing something obvious) when number 3 would be the most limiting. Surely it will always be number two a simultaneous engine failure and pressurisation failure. Can anyone think of a scenario when 3 would be the most limiting? If not then I wonder why it isn't just 1+2 or even just 2.
Even Boeing (
https://www.boeing.com/commercial/ae...icle_02_4.html) say that the decompression scenarios "logically define this reserve [fuel]"
Cheers in advance.