enclosure, where a bleed-air hose is coupled to the
The air-driven, vane, axial cooling fan is connected
by ducting to the oil temperature regulator assembly; it
provides the necessary air to cool the return oil flowing
BLEED-AIR HOSE.--The pneumatic starter
through the cooler.
duct, also called the bleed-air hose, consists of a
OIL TANK.--A rectangular, internally baffled
flexible duct, scuff cover, handling ring, bands, and an
container, the oil tank provides a reservoir for the
end fitting to connect the assembly from the air start
lubrication system oil. Located behind an enclosure
unit to the aircraft. The bleed-air hose assembly is
access panel, the oil tank is secured in place by steel
available in 30- and 60-foot lengths.
straps. Oil is drawn from the outlet, near the tank
Inspection.--It is extremely important to
bottom, by the engine-driven oil pump. Oil is returned
regularly inspect bleed-air hose assemblies because a
to the tank by the engine-driven scavenge pump via the
break or separation in the assembly can cause serious
oil cooler assembly. A drain port with a removable plug
injury to personnel and damage to equipment. The duct
is provided at the bottom of the tank and a filler neck
should be visually inspected for damaged components,
and cap assembly with a dipstick are located on the
loose clamps, and air leaks. Dimensional inspections
must also be performed to check for minimum length,
OIL PUMP.--Mounted to the accessory drive
number of splices, and the installation of the scuff
section, the oil pump is a rotary type pump that
cover. Refer to the maintenance manual for specific
operates at 4,172 rpm (nominally). Replacement of the
inspection points and dimensions.
oil pump is described in the operation and maintenance
manual. However, it is important to note that certain
Repair.--Repair of the pneumatic duct assembly
steps are particularly critical in the replacement of the
is outlined specifically in the technical manual and
oil pump. First, when installing the new oil pump,
should be adhered to when performing repairs.
ensure that the drive gear engages with the drive gear in
Particular attention should be directed to guidance on
the accessory housing. Failure to do so could indicate
splicing the hose assembly.
oil pump failure when, in fact, the pump is not being
Replace.--When repair of the duct assembly
driven. Damage may also occur to the pump.
exceeds specific guidelines specified in the technical
It is also important to prime the oil pump prior to
manual, replace it with a new assembly.
engine operation. This prevents air pockets from
forming in the oil system and decreases the amount of
time that the engine is rotated without positive oil flow
The lubrication system consists of lubricating
components and the necessary interconnecting
O I L S C AV E N G E P U M P . -- T h e o i l p u m p
plumbing (fig. 12-19). The main component of the
contains three scavenge oil elements that pump
system is the oil pump (fig. 12-20), which incorporates
scavenge oil to the oil temperature regulator valve
where, depending on temperature, it is passed through
within one unit a gerotor-type pressure pump, three
the oil cooler or bypassed directly to the oil tank.
gerotor-type scavenge pumps, and an oil filter. Other
components of the system are the cooling fan, oil
OIL FILTER.--The oil pump has a replaceable
temperature regulator assembly, oil cooler, and the oil
filter to filter contaminates from the oil stream.
O I L C O O L E R A S S E M B LY . -- T h e c o o l e r
The system functions to supply pressurized and
assembly is a two-part unit that consists of the oil
splash lubrication to the accessory drive gears, to the
assembly bearings, and to the turbine rotating
a s s e m b l y b e a r i n g s . T h e s y s t e m a l s o p r ov i d e s
Lubricating oil, MIL-L-23699, contains materials
hazardous to health and produces paralysis if
pressurized oil for operating the hydraulic servo
swallowed. Prolonged contact may irritate skin,
assembly in the modulating and shutoff valve. The
so wash your hands thoroughly after handling.
scavenge oil is pumped to the oil temperature regulator
Use in a well-ventilated area. Lubricating oil may
valve, where, depending on oil temperature, it is either
burn if exposed to heat or flame.
passed directly into the oil tank or diverted through the
oil cooler tubes, and then to the oil tank.