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-   -   737NG Loss of thrust on both engines (https://www.pprune.org/tech-log/487874-737ng-loss-thrust-both-engines.html)

Low-bypass 12th Jun 2012 15:16

737NG Loss of thrust on both engines
 
Hello folks
My questions on this memory recall checklist are these:
After completing the memory portion of it it says further down that Do not wait for successful engine start(s) before starting the APU does that mean that as soon as it's recognized that we lost thrust on both engines we can already start the Apu before doing the memory items?
The reason i' m asking this is because the FCTM says:
Initiate the memory portion of the LOSS OF THRUST ON BOTH ENGINES NNC before attempting an APU starts which contradicts part 7 of the checklist.If the windmill restart is not successful,an APU should be initiated as soon as practical to provide electrical power and starter assist during follow-on engine start attempts,then why this is the case?

Best regards

MrHorgy 12th Jun 2012 15:23

I think this is a case of the application of airmanship. If I recognised a dual engine failure I think one of the first things i'd do is start the APU asap. The QRH to me overrides the FCTM

Horgy

flyingchanges 12th Jun 2012 16:02

Just did this in the sim. Started at FL350, .82 / 340KT descent, got engines started at FL200. Engines restarted before the APU was available. I disagree with the checklist in attempting APU starts immediately as you are wasting battery power, and it will not suction feed start above FL250 anyway. The inflight relight was exceedingly slow and could easily be unintentionally interrupted by cycling the fuel lever.

misd-agin 12th Jun 2012 17:52

340? Doesn't the checklist call for 300 kts?

flyingchanges 13th Jun 2012 01:12

Yes, but you also need to get down as the cabin goes after about 2 minutes...


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