737 NG EEC alternate
Thread Starter
737 NG EEC alternate
Hi,
The QRH states:
In my mind the thrust levers are already in a 'mid position' when cruising with 88% N1 set. I imagine it provides sufficient buffer to limits and would consider that step satisfied.
Your thoughts?
The QRH states:
2 Thrust levers (both) . . . . . Retard to mid position
This prevents exceeding thrust limits when switching to the EEC alternate mode.
This prevents exceeding thrust limits when switching to the EEC alternate mode.
Your thoughts?
2 Thrust levers (both) . . . . . Retard to mid position
Obviously, if the throttles are already 'mid' position or lower, there would be no need to retard them.
Thread Starter
Thanks td.
I understand that. To be more specific with my question, do you think that 88%N1 ( ie a standard cruise setting) is 'mid' enough to prevent any excedance being possible.
Personally I do, but I know of others who would retard the levers further in order to achieve a 'mid' position.
Cheers
I understand that. To be more specific with my question, do you think that 88%N1 ( ie a standard cruise setting) is 'mid' enough to prevent any excedance being possible.
Personally I do, but I know of others who would retard the levers further in order to achieve a 'mid' position.
Cheers
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By the way, how can you notice EEC Altn light during routine operations? As far as I remember it doesn't trigger master caution, so if there's no DEU failure with DSPLY SOURCE annunciation you'll hardly ever see it.
Framer, I don't work 737 (I'm a wide body sort of guy ), so I can't really comment on the specifics of the 737 installations. Your answer would probably have to do with the exact cruise conditions and how close you already were to max climb/con power set. But I suspect it is a least possible to exceed the max climb/con rating by selecting alternate mode with the throttle at a 'normal' cruise setting.
Thread Starter
Thanks again.
That really is the crux of the matter in that some people do suspect that, and others ( like myself )don't think it's likely there will be a 11 or 12% increase in N1. Unless I get more info I will be conservative and assume that it is possible as there is nothing to lose by retarding the levers a bit more.
Don't feel bad. I used to have the same problem until I entered a workplace 'Biggest Loser' competition. I now have so much energy it's amazing.
You do get ENG on the master caution panel.
But I suspect it is a least possible to exceed the max climb/con rating by selecting alternate mode with the throttle at a 'normal' cruise setting.
I'm a wide body sort of guy
By the way, how can you notice EEC Altn light during routine operations?
Thread Starter
I think you are right Rat 5 but obviously the reason behind the physical mid point is to reduce the actual engine parameters in case the new data base sourced N1 is significantly higher. ( unless I'm completely missing something......it wouldn't be the first time )
Yes, 'mid position' is geometric, but those instructions are common across the current production Boeing fleet - which encompasses a number of both N1 and EPR engines.
So 'mid position' keeps it simple and common.
So 'mid position' keeps it simple and common.
Could you be more specific - which speed(s) are you speaking of? And are we still talking 737NG?
I know the EPR engine aircraft typically have a weight penalty associated with Alternate Mode dispatch (due to increased uncertainty in thrust) but I don't recall that being extended to engines with N1 thrust settings (GE/CFM).
I know the EPR engine aircraft typically have a weight penalty associated with Alternate Mode dispatch (due to increased uncertainty in thrust) but I don't recall that being extended to engines with N1 thrust settings (GE/CFM).
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With hard alternate mode (as in EEC ALTN dispatch), the thrust may be higher than the one in normal mode, resulting Vmc(a/g) will be higher and speeds need to be adjusted.
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EEC alternate light triggers master caution and ENG on the system annunciator panel.