Originally Posted by
Ship741
The critical fuel scenario required by the advisory circular (perhaps codified in FAR now?) requires the most restrictive fuel contingency to be protected. It is either 1EO (1 engine operating at MCT (maximum continuous thrust) driftdown level off altitude (in my experience 16-18,000 feet for a 767-300ER) or 1EO at 10,000 feet (depressurization scenario). Icing also has to be evaluated, though I've heard people argue that the drag created by a potential "frozen fan" on the dead engine was never accounted for. You can be negative fuel at ETP due to unplanned overburn in the early part of the flight but you cannot plan to be negative fuel at ETP.
Little known factoid: Some foreign carriers that have no regulatory requirement for Dispatch routinely plan their flights with negative fuel at ETP. This is due to "corporate bean counters" dictating fuel loads. If the public only knew. Imagine losing an engine at the equal time point and running out of fuel prior to reaching the diversion airport.
There are risks to everything.
ETOPS doesn’t account for fires-for example. In any major fire scenario, planes have become unflyable in 30 mins or less. In that sort of situation, you are in the water.
The folks who set out to design ETOPS knew there would eventually be non-good-outcome scenarios. They should be rare, but one day, one will happen.
The hole in fuel tank, extra drag scenarios, and other such events all have “in the water” as the outcome. Same can happen on a 3 or 4 engine plans.
Life has risk