B737 speedtrim fail / start switch
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B737 speedtrim fail / start switch
We had this question on our recurrent test. Can anyone comment or direct me to source of such information?
Last edited by vlkyplky; 31st Mar 2015 at 08:00.
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If you're not sure of option A then look at the others; Options B and C are nonsense in the first 6 words. 
Only the action of setting the start switch to Continuous will keep the EEC powered.
Only the action of setting the start switch to Continuous will keep the EEC powered.
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Power Plant
".....blank parameters which are controlled by the EEC and hence are only displayed when the EEC powers up when the associated start switch is selected to GND. During start-up the EEC's receive electrical power from the AC transfer busses, but their normal source of power are their own alternators which cut-in when N2 is above 15%."
".....blank parameters which are controlled by the EEC and hence are only displayed when the EEC powers up when the associated start switch is selected to GND. During start-up the EEC's receive electrical power from the AC transfer busses, but their normal source of power are their own alternators which cut-in when N2 is above 15%."
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If we consider the SW to be true, still where is the link between the EEC and Speedtrim fail? I think thats about half of the answer. Mainly why?
in the meantime Urban Dictionary: Sauce
in the meantime Urban Dictionary: Sauce
Last edited by vlkyplky; 31st Mar 2015 at 18:43.
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Ok,just because you taught me some Essex slang which ill definitively use in the future,ill give a hint on the speed trim.
The speed trim needs the N1 info,otherwise how can it work? remember it is about speed stability,(low thrust-high speed--->stab trim gives nose up and high thrust-low speed--->speed trim sends info to the the stab trim to give nose down trim)
The EEC has that info,it uses it to control your engine thrust and provide that info toyour speed trim.
The speed trim needs the N1 info,otherwise how can it work? remember it is about speed stability,(low thrust-high speed--->stab trim gives nose up and high thrust-low speed--->speed trim sends info to the the stab trim to give nose down trim)
The EEC has that info,it uses it to control your engine thrust and provide that info toyour speed trim.
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Groucho,
There is no direct answer in the FCOM,if that is the sauce you are looking for....
However,the Engine start switch powers the EEC via the engine start lever in Idle or if the engine start switch in GND or CONT.(AMM wiring schematic 73-22-11).
The second part of the question is the link between no N1 info and subsequent loss of speed trim...i believe i answered it above and one needs to find the interaction between the EEC and the speed trim function.
The EEC gets info of N1 directly from the sensors or via the DEU,if no input then speed trim has no info to work with..(AMM 22-11).
There is no direct answer in the FCOM,if that is the sauce you are looking for....
However,the Engine start switch powers the EEC via the engine start lever in Idle or if the engine start switch in GND or CONT.(AMM wiring schematic 73-22-11).
The second part of the question is the link between no N1 info and subsequent loss of speed trim...i believe i answered it above and one needs to find the interaction between the EEC and the speed trim function.
The EEC gets info of N1 directly from the sensors or via the DEU,if no input then speed trim has no info to work with..(AMM 22-11).
