BOMBARDIER BD-100-1A10, Operating Manual

Page: 288 / 544

FLIGHT CONTROLS
Volume 2 Flight Crew Operating Manual Sep 13/2004
10-02-06
CSP 100-6
REV 1
SECONDARY FLIGHT CONTROLS (Cont)
FLAPS
The single-slotted Fowler flaps are electronically controlled and operated by a hydraulic motor in the flap power unit. There
are two hydraulic systems. Under normal conditions, the flaps will operate with the right hydraulic system. When ALTN
FLAPS is selected ON, flaps will operate from the left hydraulic system and a FLAPS ALT PRESS lamp will illuminate
in green on the EICAS. FLAPS RATE LOW (A) CAS will illuminate if the flap control unit is controlling the system at a
lower than nominal speed in order to reduce the hydraulic flow. This is the case if either the pressure switches of the hy-
draulic system indicate that the engine driven pump for the main system is not working, or the alternate hydraulic supply
is selected. Normal flap extension from 0 to 30 does not exceed 20 seconds with the right engine-driven hydraulic pumps
operating. However, time extends up to 60-70 seconds while lowering flaps from 0 to 20 in flight when using ALTN FLAPS
or when using the right DC hydraulic pump. Each flap panel, one on each wing, has three safe-life flap tracks and is driven
by two screw jack actuators. A stainless steel shaft transfers power from the hydraulic motor to each flap actuator. The flap
control lever is located on the center pedestal and is recessed to prevent inadvertent operation.
COMPONENTS AND OPERATION
The flap power unit (FPU) is located aft of the wing center section behind the wing attachment fitting and contains the
hydraulic motor, servo control valve, arming solenoid valve and pressure switch. The servo valve responds to electrical
signals from the flap control unit and meters hydraulic pressure to extend or retract the bidirectional hydraulic motor. The
arming solenoid valve must be opened by the flap control unit before hydraulic pressure is available to the servo valve. The
pressure switch monitors system pressure between the arming solenoid valve and servo valve. If hydraulic pressure is not
available on flap selection, flaps are inoperative. If the FPU detects a fault, the flaps may deploy at a reduced speed when
selected and FLAPS RATE LOW CAS will illuminate.
Stainless steel shafts routed along the rear wing spar transmit the rotary motion of the flap power unit to the input shaft of
each of the flap actuators. Two rotary variable differential transformers (RVDTs) mounted on the outboard side of each
outboard flap actuator provide position information to the flap control unit (FCU) and the flap position indicating unit. The
flap actuators incorporate a screw jack and are attached to the rear spar. These actuators convert the rotary input motion
into linear output motion through these screw jacks, driving the flaps. Each actuator has overtravel end stops. The screw
jack design of the flap actuators prevents uncommanded retraction due to airloads or vibration.
The flap control unit (FCU) performs the following functions:
- Controls flap panel movement according to pilot commands
- Monitors critical system conditions (runaway/uncommanded movement, surface asymmetry, system jam, over-
speed and speed differential)
- Switches the system to fail safe condition after detection of a critical failure
- Monitors FPU for internal and external hydraulic leakage and provide annunciation to the aircrew
- Flap position to the stall protection system
- Provides data for cockpit indication and for maintenance purposes
In addition to control and monitoring, the FCU also contains the left hand and right hand flap position indication unit
(FPIU) and provides flap panel position to the EICAS
FLAP ALERTING
The flap position alerting system is monitored by airspeed, flap position, spoiler, gear position, and altitude. An overspeed
warning horn is activated if flaps are extended above the following speed:
- V
FE
210 kt — 10
°
- V
FE
210 kt — 20
°
- V
FE
175 kt — 30
°