747-400 Thrust Limit Mode Logic for "GA"
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747-400 Thrust Limit Mode Logic for "GA"
A question raised on another forum (paraphrased)....
If a 747-400 is forced back to the departure airport shortly after takeoff, without the flaps going back to fully UP, will the GA thrust limit mode automatically be armed during the approach (i.e. will the Upper EICAS show G/A) or will it have to be selected manually via the FMC?
The logic states in the manual that the GA thrust limit mode is armed either by flaps not in UP or glideslope mode active. However, the flaps never return to UP in this situation and the aircraft may be returning to an airport which doesn't have an ILS.
I thought that it might be re-armed by the flaps moving towards extend, but the logic might be confused by automatic flap load relief (if that should occur). On the 777, I hear that landing flaps can re-arm the GA mode (if the flaps don't reach UP).
If the mode is not automatically armed. Will the limit change to GA anyway if one of the TOGA switches is pushed?
If a 747-400 is forced back to the departure airport shortly after takeoff, without the flaps going back to fully UP, will the GA thrust limit mode automatically be armed during the approach (i.e. will the Upper EICAS show G/A) or will it have to be selected manually via the FMC?
The logic states in the manual that the GA thrust limit mode is armed either by flaps not in UP or glideslope mode active. However, the flaps never return to UP in this situation and the aircraft may be returning to an airport which doesn't have an ILS.
I thought that it might be re-armed by the flaps moving towards extend, but the logic might be confused by automatic flap load relief (if that should occur). On the 777, I hear that landing flaps can re-arm the GA mode (if the flaps don't reach UP).
If the mode is not automatically armed. Will the limit change to GA anyway if one of the TOGA switches is pushed?
