TAIL ROTOR SERVO ACTUATOR - GENERAL
The tail rotor servo actuator is a fixed body actuator comprising two separate
cylinder assemblies, which are bolted together at the actuator center and
tandem pistons.
TR SERVO ACTUATOR – PRINCIPLE OF OPERATION
The actuator body is provided with a mounting flange for the installation to
the left side of the TGB. One piston end extends with a control rod which is
connected to the rotating control spider; the other piston end is connected
with the input lever. Each cylinder assembly has an integral flow distributor
that contains a dual concentric valve which provides the normal servo
control and a jam tolerant function.
The flow distributor assembly is controlled through an input lever which
receives the input from pilot's flight controls and through a feedback link
which is connected to the input lever and hence to the output piston.
The anti-jamming device consists of a inner and outer sleeve that are held in
place under the action of a spring.
In case of a valve spool jam the force required at the input lever to operate
the main valve exceeds a preset value thus compressing the spring and
allowing the two sleeves to move relatively to control the hydraulic fluid
within the cylinder chambers.
The actuator is designed to operate normally with two hydraulic systems
which are completely separated within the actuator. In case of failure of one
system, the level of performances with only one hydraulic system operating
ensures no degradation of the helicopter handling qualities.