CHAPTER 71
POWERPLANT
71-00 Description
One Rolls-Royce model 250-C300/A1 (commercial designation RR300) free-turbine
turboshaft engine powers the helicopter. The engine is equipped with an ignition exciter,
igniter, starter-generator, two tachometer senders, and additional powerplant instrument
senders.
A direct drive, squirrel-cage style cooling fan is mounted to the intermediate shaft and
supplies cooling air to the engine and gearbox oil coolers.
Induction air enters through multiple openings in the upper fuselage cowlings and flows into
a plenum forward of the firewall. The plenum contains a radial-flow air filter at the engine
compressor inlet. The standard filter element is foam. A high-efficiency filter element with
pleated media is optional. The high-efficiency filter includes a sight gage inside the upper
left cowl door with provides an indication of filter dirt load.
NOTE
The high-efficiency filter is recommended for operating in dusty
conditions. The filter may not filter fine sand or dust, resulting
in reduced engine life.
If the air filter becomes blocked, spring-loaded doors at the front of the filter housing open
allowing unfiltered air to the engine. The AIR FILTER annunciator illuminates when filter
bypass is occurring.
Periodically performing power assurance checks may provide indication of engine
deterioration or air filter blockage. Maintenance actions such as air filter cleaning and
compressor wash should be performed if aircraft fails power assurance check.
A temperature switch is mounted to the firewall above the engine to detect a fire in the
engine compartment. Abnormally high temperature causes the ENGINE FIRE annunciator
to illuminate.
JUL 2020 Chapter 71 Powerplant Page 71.1
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