I A P 2 0 2 3 . 0 0 1 - A F M / I R I S T E X A N I I P A G E | 25
FOR SIMULATION USE ONLY ā NOT A TRAINING AID
Power for the oil pressure transducer is provided through a circuit breaker,
placarded OIL TRX located on the battery bus circuit breaker panel in the front
cockpit.
Reduction Gearbox (RGB)
The RGB is a two-stage planetary reduction drive to reduce the power turbine
output shaft speed of over 30,000 RPM to the propeller operating speed of 2000
RPM.
The RGB is mounted on the front of the engine and driven by the hot gases
impinging on the two-stage power turbine. There is no mechanical connection to
the gas generator section.
A chip detector is mounted in the RGB to detect ferrous material in the oil. If the
chip detector is activated, a signal is transmitted to the EICAS illuminating a red
CHIP warning message indicating oil contamination.
The propeller interface unit (PIU), torque probe, and permanent magnet alternator
(PMA) are mounted on top of the RGB, and the air conditioning compressor is
mounted on the right side of the RGB and is belt driven by the propeller assembly.
Engine power output is measured by the torque produced by the reduction gearbox.
Propeller
The power turbine drives the aluminium 97-inch, four bladed, constant-speed,
variable-pitch, non-reversing, feathering propeller (Figure 1-11) through the
reduction gearbox.
The propeller system is designed to maintain a constant speed of 2000 RPM (100%
NP) during most flight conditions.
The engine power management unit (PMU) and the propeller interface unit (PIU)
automatically control the propeller blade angle (pitch) and propeller speed (NP).
Because the engine is flat rated, 100% torque is available from sea level to
approximately 12,000 to 16,000 feet MSL on a standard day.
At 100% indicated torque, the engine is producing approximately 2900 foot-pounds
of torque at the prop shaft. This equates to approximately 2750 pounds of thrust at
sea level, zero airspeed.
Propeller pitch may be defined by three basic conditions: feathered; low pitch (flat
or fine); and high pitch (coarse).
Each pitch condition is the measure of the angle between the plane of rotation of
the propeller and the chord line of the blade. When feathered, the propeller blades
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