Auto Throttle will not Arm

[John M. 0]

I suppose as a newcomer to PMDG Next Generation 737 I am overlooking something obvious but ........On many occasions when I click the switch to arm the autothrottle it will not stay in the correct position. The annunciator shows fleetingly 'throttle armed' message or some similar wording but then nothing. The middle warning light (which says A/T and something else I cannot read)flashes on and off and I can clear it by clicking on it. But I still cannot get the auto throttle to arm.I would be grateful if someone could help, perhaps by listing the conditions which have to be met before the autothrottle can be armed,Best wishes to all, John Morgan

[Guest meyomyx]

Welcome John,A common one this - do a search for autothrottle and you'll find it. Check your engine driven generators are selected on (rather than the APU generators) - think that'll sort it!

[John M. 0]

Thanks Nick,I think that does it............I think!best wishes, John

[nmrdude 0]

There is another reason A/T will not arm besides engine generators being off.. The alt target in pref is set higher than the aircraft can reach at current weight.  If this happens and you are flying, vnav should be OK and should mange speed target but you will need to manually move throttle up to ~n1 of 96% or so to have reasonable power for proper climb rate. Once established A/T might arm if alt target on dash dial is OK.  In any case once at stable flight on climb profile more or less go to pref and lower alt target to something reachable at weight and set mcp dial on dash to match.