SmartCockpit Fokker 50, Manual

Page: 11 / 18

FLAPS
Operation
The flaps can be controlled by a seven position flap selector (UP, 5, 10, 15, 20, 25, 35). The
mechanically operated flap selector valve directs hydraulic pressure to the flap drive unit in
accordance with flap selector position. The position of the flaps is indicated by a flap position
indicator located at the center main instrument panel. Position markings are located at the
inboard side of the engine nacelles. A disagreement light illuminates when flap position is not
in accordance with flap selector position. The alert is inhibited during the period when the
flaps are in transit.
Alternate operation
Adjacent to the flap selector is an alternate flap control switch that operates the flap drive unit
electrically. The travel range is the same as in the hydraulic mode; however, the flaps extend
at a slower rate. After alternate operation, no hydraulic operation can be made before the
system is reset. Reset is obtained on the ground by moving the flap selector to an other
position.
Asymmetry protection
LH and RH flap positions are continuously compared and when an angular difference is
detected an alert is presented. When asymmetry is detected during hydraulic operation,
further flap movement is stopped.
Fokker 50 - Landing Gear & Flaps
Page 11