If you are flying at FL 330 and your Grid MORA is FL220 and your drift down is FL180. What would you do? You have an engine failure.
First question is are you off route or not? If you follow the airway and MEA is depicted below FL 180 forget grid MORA descent to FL 180 applying necessary drift down strategy. In case you're off the airway then you better have a good situational awareness regarding the terrain profile along your route coz, at least on the BUS, grid MORA is only good for 40 NM after that it might rise or fall. If you happen to have a newer FMS version with indication of the lowest and the highest terrain within the selected range, well no brainer here, isn't it?
If the loss of an engine is your only worry, no pressurization problems, then even the obstacle strategy initially is OK. You'll certainly pass 40 NM applying even standard strategy for the drift down. The question is what's thereafter?
Funny, those upgrade questions, aren't they? Best of luck commander.
