assembly transmits through the safety coupling.
train. The propeller brake has three positions.
They are the released, applied, and locked
Positive torque occurs when the power section
drives the propeller through the reduction gear
The propeller brake is a friction-cone type,
assembly. Negative torque occurs when the
propeller drives the power section. The safety
consisting of a stationary inner member and a
coupling backs up the NTS system to prevent
rotating outer member. During normal engine
operation, reduction gear oil pressure holds
the brake in the released position. This is
NTS system fails to limit negative torque, the
accomplished by oil pressure, which holds the
safety coupling protects the engine from exten-
outer member away from the inner member.
sive damage by decoupling.
When the engine is shut down, reduction gear oil
pressure drops. A spring force moves the outer
member into contact with the inner member or
to the applied position. The propeller brake locks
when it is moved in a direction opposite normal
and turbine rotors can rotate easily when the
rotation. When locked, it acts upon the reduction
engine is shut down, a propeller brake is needed.
The propeller brake prevents the propeller from
gearbox primary stage reduction gearing to
prevent movement along with the friction-cone
windmilling on the ground or when it is feathered
in flight. It also decreases the time for the
propeller to come to a complete stop after engine
TURBOPROP CONTROL SYSTEMS
shutdown. The brake is in the reduction gearbox
assembly between the rear case and rear case inner
The control of a turboprop engine involves the
diaphragm. It is part of the accessory drive gear
control of engine speed, temperature, and torque.
Figure 8-6.-Control schematic.