737 standby hyd
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737 standby hyd
Recently got into a debate with a few co-workers and we were not able to come to a conclusion do to lack of resources. Will the rudder trim remain operative with a loss of sys a and b hydraulics with the standby rudder active?
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It will continue to work through the standby rudder PCU 
Reference AMM SDS 27-21-00
During electric trim operation, the pilots move the rudder trim
control on the aisle stand which sends a signal to the rudder
trim actuator. The rudder trim actuator moves the rudder feel
and centering unit. This moves the rudder torque tube and the
main and standby rudder PCU input rods and it backdrives the
rudder pedals to the new commanded position. The trim
actuator movement also creates a new neutral position for the
feel and centering unit.
control on the aisle stand which sends a signal to the rudder
trim actuator. The rudder trim actuator moves the rudder feel
and centering unit. This moves the rudder torque tube and the
main and standby rudder PCU input rods and it backdrives the
rudder pedals to the new commanded position. The trim
actuator movement also creates a new neutral position for the
feel and centering unit.
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The plain English way to say this is that the "trims" on all Boeing aircraft work by re-centering the artificial feel, not by moving trim tabs. So, as long as artificial feel is in play (surface is hydraulically powered) the "trims" will continue to operate.
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With A and B system hydraulics inop, you'll still have rudder and elevator trim. Aileron trim will still operate but it will be ineffective as there is no hydraulic power to hold the ailerons in the trimmed position. They will want to fair with the airstream.
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Recently got into a debate with a few co-workers and we were not able to come to a conclusion do to lack of resources. Will the rudder trim remain operative with a loss of sys a and b hydraulics with the standby rudder active?
are the aileron trim usable when the Sys A and B fail?
So NO.
With A and B system hydraulics inop, you'll still have rudder and elevator trim
Elevator trim?you mean elevator balance tabs? They are mechanical so they will help in offloading elevator forces during manual reversion.
The stabiliser trim can be electrical via the switches or manual via the handles,in any case hudraulic pressure is not needed to operate the stabiliser.
Last edited by de facto; 3rd Oct 2012 at 04:25.
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I should have specified the aileron and rudder trims.
The trim wheel works any time it moves, electrically or manually. That is true of the 707, 727, 737, I'm not familiar with the stab trim on later Boeings.
The trim wheel works any time it moves, electrically or manually. That is true of the 707, 727, 737, I'm not familiar with the stab trim on later Boeings.
Last edited by aviatorhi; 3rd Oct 2012 at 04:41.
