Flaps retract from 40 to 30 but do not extend to 40 when airspeed is reduced to less than 157 knots



Fleet Type:

All NG

Applicable Reference:

SDS 27-51-00-023 AMM 27-51-00-720-804 SSM 27-54-11


Flaps retract from 40 to 30 but do not extend to 40 when airspeed is reduced to less than 157 knots

Possible Fix:

Replace Flap hydraulic drive motor.


If power and ground is supplied as needed then removed when airspeed is decreased the problem should be a Flap drive problem. This problem was corrected by replacing the Flap drive motor.

The flaps would retract and extend as specified from 30-25-30 when airspeed was decreased. But would not go from 40-30-40, per the AMM Flap load relief task in this instance.

When the flap hydraulic drive motor is not installed in the aircraft the shaft should not be excessivly stiff to move.


Power is provided to the Flap load relief solenoid through the Flap Control handle when the handle is positioned as required. The ground to this solenoid is provided from the FSEU when the airspeed value required is supplied to the ADIRU which provides that airspeed information to the FSEU using a digital data bus.

If this system is operating as required, then the Flap hydraulic drive system is suspected as at fault for incorrect or lack of movement. Thanks to Tom S. for his input !



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