WHEEL BRAKE SYSTEM - PRINCIPLE OF OPERATION
Dynamic braking is achieved through pedal levers installed on the yaw
pedals. Each lever operate a hydraulic master cylinder which generates the
required pressure by means of a hydraulic fluid contained in a reservoir. The
pilot hydraulic master cylinders are supplied through the copilot ones.
There is no priority between pilot and copilot to generate pressure in the
brake system.
Differential braking can be achieved during taxiing on ground by operating
only left or right pedal to obtain the dynamic steering of the helicopter (the
lock of the nose wheel in center position must be disengaged).
Static braking is achieved when the helicopter is parked by pulling and
rotating clockwise the park brake handle and pushing on the brake pedals
until the PARK BRK ON advisory message appears.
When the park brake handle is pulled and set for parking but pressure is
below the minimum value, the PARK BRK PRESS caution message is
displayed in the CAS.
To release the park brake, pilot must rotate the park brake handle ccw and
push the left brake pedal to release the retaining mechanism thus allowing
the park brake handle to reset and release the brake pressure.
In case of park brake system failure (park brake handle released and either
or both brake pressure switches indicate that pressure is applied to the
wheel brake) the PARK BRK ON caution message is displayed in the CAS.
LIMITATIONS
Refer to AW139-RFM-4D Section 1.