ROTOR BRAKE – OPERATIONS
The braking action is manually controlled by the Rotor Brake Control Lever
(RBCL). The movement of the lever allows to generate the required
hydraulic pressure, using a mechanical pump that is installed inside the
Rotor Brake Control Module (RBCM). The RBCL and the pump are
connected via a control rod. The stroke between PUMPING and BRAKE
positions, produce the pressure for:
NORMAL BRAKING
• When the pilot moves the RBCL to BRAKE, the RBCM supplies the
hydraulic pressure needed to stop the rotor disk (≈ 26-28 bar). The
rotors stop in 11 ÷ 15 sec approx. (DYNAMIC BRAKING).
PARKING
• To perform a “pumping action” the RBCM permit to reach a value of 46
bar required to maintain the rotors stopped for approximately 8 hours.
When the lever is set to OFF, the outlet valve (mechanically connected to
the lever), goes in open position and permit to de-pressurize the circuit.
For safety reason, the RBA can move in the up and down position. This
feature, permit to maintain the Rotor Brake Assembly (RBA) away from the
RB disk when all the engines are running and the helicopter is in flight. The
RBA is moved by an electrical motor, called Rotor Brake Actuation Assembly
(RBAA).
This function is managed by the Rotor Brake Relay Box (RBR) that uses the
following signals:
• RBCL / RBAA UP/DOWN positions;
• Engine Control Panel selectors positions;
• WOW (Weight-On-Wheels).
The RBA moves in UP position only when the helicopter is on the ground
and the engines mode selector in set to OFF.
The electrical shut-off valve prevents inadvertent pressurization of the RBA
(valve open) when:
ON GROUND
• all engines are OFF and WOW ON and hydraulic circuits are
pressurized (pressure detected by the Interlock Pressure Switch)
IN FLIGHT
• all engines ON and WOW OFF.
In case the system is already pressurized and the “ENGINE START-UP
PROCEDURE” begins, the shut-off valve automatically opens and depressurizes
the hydraulic circuit.
IN FLIGHT OPERATIONS
• the RBCL is in OFF position
• no hydraulic pressure is furnished to RB circuit
• the caliper is DOWN
• the CLPR DOWN green LED on the Rotor Brake Pressure Indicator
(RBPI) is lighted