For the OEI descent, whichever strategy, the intention is to keep the remaining engine operating at MCT for the duration of the descent until approaching your chosen (and achievable) ceiling. Shallowing the dive / drift-down as much as possible.
Step 1 - Both TLs to MCT (without the need to identify which one has failed).
Later on, you will be selecting OP DES for the reasons already stated. In the OEI condition, the A/THR range extends up to the MCT detent, thus it would command THR IDLE which is undesirable. To prevent this from happening:
Step 2 - A/THR: OFF.
a) AVIATE is done. Next
b) NAVIGATE
- action the briefed contingency procedure e.g. drift-down escape route, track offset if applicable. Next
c) COMMUNICATE
- speak to the other crew member verifying both are on the same page and paragraph
- alert ATC i.a.w. regional procedures (Emergency, RVSM, MNPS). Next
d) MANAGE SYSTEMS
- follow the appropriate engine drill
I am not aware of any reasons to disengage A/THR apart from keeping the MCT with OP DES. That one is good enough, innit?
Once approaching the OEI ceiling the flight path will shallow asymptotically which becomes impractical, so the technique is to select V/S -500 (increasing descent rate). With the extra available energy due to MCT the speed would start to increase. That is undesirable from FF viewpoint (as well), so A/THR is armed and engaged to allow conventional speed control for the chosen target.
Last edited by FlightDetent; 25th Aug 2017 at 14:05.