Thrush Aircraft S2RHG-T65 TURBO THRUSH Maintenance Manual page 68

THRUSH AIRCRAFT, INC – MODEL S2RHG-T65 TURBO THRUSH
AIRCRAFT MAINTENANCE MANUAL
various sizes that allow entry of compressor delivery air. The flow of air changes
direction 180 degrees as it enters and mixes with fuel. The fuel/air mixture is ignited
and the resultant expanding gases are directed to the turbines. The location of the liner
eliminates the need for a long shaft between the compressor and the compressor
turbine, thus reducing the overall length and weight of the engine.
Fuel is injected into the combustion chamber liner through 14 simplex or Dual Orifice
Fuel nozzles supplied by a dual manifold consisting of primary and secondary transfer
tubes and adapters. Two spark igniters that protrude into the liner ignite the fuel/air
mixture. The resultant gases expand from the liner, reverse direction in the exit duct
zone, and pass through the compressor turbine inlet guide vanes to the single-stage
compressor turbine. The guide vanes ensure that the expanding gases impinge on the
turbine blades at the most optimum angle, with minimum loss of energy.
The still expanding hot gases from the gas generator are still directed forward to the
power turbine inlet guide vane which directs, at the most optimum angle, the gas flow
onto the power turbine which drives the propeller shaft via a two-stage reduction gear
box.
The compressor and power turbines are located in the approximate center of the engine
with their respective shafts extending in opposite directions. This feature provides for
simplified installation and inspection procedures. The exhaust gas from the power
turbine is collected and ducted in the bifurcated exhaust duct assembly and directed to
atmosphere via twin opposed exhaust stubs.
Interturbine temperature (T5) is monitored by an integral bus bar, probe and harness
assembly installed between the compressor and power turbines with the probes
projecting into the gas path. A terminal block mounted on the gas generator case
provides a connection point to cockpit instrumentation.
All engine-driven accessories, with the exception of the propeller governor, over speed
governor and NP tachometer-generator, are mounted on the accessory gearbox at the
rear of the engine.
These components are driven by the compressor by means of a coupling shaft, which
extends the drive through a tube at the center of the oil tank. The rear location of
accessories provides for a clean engine and simplifies maintenance procedures.
The engine oil supply is contained in an integral oil tank, which forms the rear section of
the compressor inlet case. The tank has a total capacity of 2.3 US gallons and is
provided with a dipstick.
An engine-driven fuel pump further pressurizes fuel supplied to the engine from an
external source and the fuel control unit (FCU) controls its flow to the fuel manifold.
The power turbine drives a propeller through a two-stage planetary reduction gearbox
located at the front of the engine. The gearbox embodies an integral torque meter
device, which is instrumented to provide an accurate indication of engine power. A chip
detector is installed at the bottom of the gearbox.
The propeller reversing installation is comprised of a single-acting hydraulic propeller
that is controlled by a propeller governor which combines the functions of a normal
constant speed unit (CSU), a reversing valve and a power turbine (Nf) governor. A
mechanical linkage between the propeller governor Beta control valve and the air bleed
link enables the FCU and the propeller governor to modify engine power to maintain
4-4
Effective: 5/05/04