25 OCT 2010 R66 Maintenance Manual Chapter 75 Engine Air Systems Page 75.1
CHAPTER 75
ENGINE AIR SYSTEMS
75-00 Description
This chapter includes a description of the engine anti-ice system. Refer to RR300 Series
Operation and Maintenance Manual (OMM) and manufacturer’s maintenance publications for
system-specic inspection, repair, and maintenance procedures.
The Rolls-Royce engine model 250-C300/A1 anti-ice system provides hot compressor discharge
air to the compressor front support. Areas of the front support are subject to ice formation
when the engine is operated near or below freezing temperatures and visible moisture is present.
An anti-ice switch located on the cyclic box cover is selected by the pilot in certain conditions
(see R66 Pilot's Operating Handbook).
The engine anti-ice system includes an air valve, a solenoid valve, and a pressure switch. The
air valve is mounted on top of the compressor scroll; the solenoid valve and pressure switch
are mounted on top of the compressor. When anti-ice is switched "ON", the solenoid valve de-
energizes, the pressure-activated air valve opens, the pressure switch closes which illuminates
the green anti-ice segment on the annunciator panel, and hot, compressed-air is routed to
hollow passages in the front support vanes and center hub.
Anti-ice system operation will result in some performance degradation due to hot induction air
and reduced air-volume reaching the power and gas producing turbine stages.
The anti-ice solenoid valve is electrically-closed, or powered-off. Anti-ice will automatically
function in the event of an electrical failure.
75-10 Engine Anti-Ice
See RR300 Series Operation and Maintenance Manual (OMM) for anti-ice system maintenance.
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