737 NG EEC alternate
Hi,
The QRH states: 2 Thrust levers (both) . . . . . Retard to mid position 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. |
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 |
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.
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Framer, I don't work 737 (I'm a wide body sort of guy :E), 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.
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Thanks again.
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? |
I'd always thought 'mid-position' was physical geometric thing rather than an N1%. Wrong or right?
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RAT 5,
I don't think so, as the thrust levers aren't linearly(?) aligned with the N1, if that makes sense. |
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 :) )
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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. |
Just imagine a 'Display Source' indication on your PFD, in Climb..and follow the QRH, on your next flight. This will answer the question.
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Speed adjacement
When dispatching with EEC in ALTRN, we should adjust speed.
Why ?? |
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). |
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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Originally Posted by Emel.OW
(Post 8439109)
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.
EEC alternate light triggers master caution and ENG on the system annunciator panel. |
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