enicalyth, its also interesting to consider aerodynamic qualities of your airplane for a very rear occasion like dual flame out., in other words what is my finesse? Maintaining the same descent speed profile .82/300 due to technical reasons windmilling etc.... It takes about 100 NM (15 min) to come down from FL 400 or a factor of 4 or finesse of 25 with all engines stopped.
Cheers.
