CSP−900RMM−2MD Helicopters, Inc.
Rotorcraft Maintenance Manual
Page 1
Original
79-00-00
ENGINE OIL
DESCRIPTION AND OPERATION
1. Oil System
The engine oil system supplies lubricating oil
to the accessory drive splines and bearings and
engine bearings. The system consists of
pressure, scavenge, and breather subsystems.
A. Pressure Oil Subsystem
The pressure oil subsystem is unregulated,
whereby oil pressure and flow rate vary with
Ng speed. Oil flow rate is 30 lbs/min. at idle, to
50 lbs/min. at takeoff. Pressure operating
range is from 75 to 105 psig and varies
depending on Ng speed and oil temperature.
Oil is drawn from the integral oil tank by the
oil pump and enters the pump through a filter
screen in the bottom of the reduction gearbox
housing. The oil is then routed to the oil cooler
and returns through the oil filter assembly
before being distributed throughout the
engine.
The permanent magnet alternator (PMA), air
conditioning compressor, and starter/generator
drive pads are oil jet lubricated. The reduction
gearbox bearings are lubricated by side jets.
Oil to the No. 1, 2 and 3 bearings is fed
through the input shaft and provides lubrica
tion to these bearings. The pressurized oil for
the No. 1, 2 and 3 bearings must first flow
through a screen which protects the oil nozzles
from blockage by foreign matter.
Windmill / Cold Start Valve - the combined
windmill / cold start valve located downstream
from the pressure pump is a spring loaded
pressure relief valve. It provides a safeguard
against excessive pressure buildup during
starts in cold weather operation. The valve
opens and bleeds oil back to the sump if the oil
pressure exceeds 200 psig.
It also stops the oil flow through the engine to
prevent potential fire hazards in a windmill
situation.
Oil Cooler - each engine's pressure oil from
the oil pump is routed to one of the combina
tion engine and transmission oil coolers. The
oil cooler has separate core tubes to provide a
heat exchange for the engine or transmission
oil. Cooled engine oil from the oil cooler
returns to the engine reduction gearbox
through the oil filter assembly.
Oil Filter Assembly - the oil filter assembly
is located on the reduction gearbox below the
engine output shaft. Particles in the oil are
trapped in the filter. The filter assembly has a
bypass valve and impending bypass indicator.
Oil Filter Bypass Valve - a filter bypass
valve is located adjacent to the oil filter
assembly. In the event of filter blockage, the
spring loaded bypass valve will open at 25 psig
differential pressure to allow oil to bypass the
filter element.
Oil Filter Impending Bypass Indicator - a
differential pressure actuated filter impending
bypass indicator is located adjacent to the oil
filter assembly. In the event of impending filter
blockage, the bypass indicator protrudes from
the housing.
A thermal lockout feature prevents impending
bypass indications below 100 F oil tempera
ture which prevents false indications at engine
start up with cold oil.
Pressure Adjustment Valve - the Pressure
Adjustment Valve (PAV), located at the bottom
of the reduction gearbox, adjusts oil pressure
at specified engine operating conditions. The
PAV operation ensures proper oil pressures
and flows throughout the entire engine
operating range. Excess oil from the valve is
returned to the pressure pump inlet.
No. 5 Bearing Oil Pressure Tube - oil to
lubricate the No. 5 roller bearing flows
through a stainless steel tube that attaches to
the reduction gearbox and to an exhaust duct
flange at the No. 5 bearing cover.
Sight Glass - a prismatic sight glass is
located on each side of the reduction gearbox.
Each bull's eye type sight glass provides a
visual oil level indication.
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