CSP–520N–1
General
MD 520N (500N) ROTORCRAFT FLIGHT MANUAL
TM
Original
1–11
Torque is transmitted independently to the rotor through the main rotor
drive shaft. Lifting loads are prevented from being imposed onto the main
transmission eliminating thrust loading of transmission parts.
Anti Torque System:
The NOTAR
R
system is an anti−torque system made up of an enclosed fan
driven by the main rotor transmission through the aft transmission, a circu+
lation control tailboom, direct−jet thruster, and horizontal stabilizer with
two vertical stabilizers.
The left vertical stabilizer is connected to the pilot’s anti−torque pedals. It
operates similar to an airplane rudder. The stabilizer moves through ap+
proximately 29 degrees of motion, and is moveable to provide sufficient con+
trol power in an autorotation and to unload the thruster in forward flight
for optimum cruise performance. A Yaw Stability Augmentation System
(YSAS) controls the right vertical stabilizer and is driven by a small elec+
tro−mechanical actuator mounted within the horizontal stabilizer. The right
stabilizer moves through approximately 15 degrees of motion. Signals for
the yaw SAS are obtained from a yaw rate gyro and lateral accelerometer
mounted under the right pilot seat. The YSAS is installed to enhance han+
dling qualities.
In forward flight the vertical stabilizers in conjunction with the direct−jet
thruster provide the required anti−torque and directional control.
Main rotor system:
The helicopter utilizes a five bladed, fully articulated main rotor assembly
with unique features. While contemporary helicopters use torsion tension
straps in lieu of thrust bearing stacks to contain blade centrifugal loading
and allow feathering, the MDHS strap pack arrangement goes three steps
further. First, the strap configuration (while secured firmly to the hub) ac+
tually allows the centrifugal load exerted by one blade to be countered by
the force exerted by the opposite two blades. Thus, very light centrifugal
loads are sensed by the hub. Second, the V−legs of the strap pack rotate as
driving members to turn the blades. Finally the straps are configured to al+
low feathering and flapping of the blades. The main rotor blades are se+
cured to the hub with quick release lever type pins.
Flight controls:
Cyclic, collective, and adjustable pedal controls are provided at the left crew
position (right position, military only). Adjustable friction devices, which
may be varied to suit the individual pilot, are incorporated in the cyclic, col+
lective and throttle controls. In addition, electrical cyclic trim actuators al+
low flight loads to be trimmed out. Since stick control forces are low, a hy+
draulic boost system is unnecessary. An optional dual control system may be
easily removed to provide room for passengers or cargo.
