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TM 55-1520-240-23-5
6-1
DRIVE SYSTEM
(Continued)
6-1
COMBINING TRANSMISSION
The combining transmission receives input torque from
the two engine transmissions through the engine drive
shafts. It combines the torque and transmits it to the
forward and aft drive shafting through output shafts.
NO BREAK - WORK HARDER
The transmission is bolted to the airframe in the lower
forward part of the pylon. Access is through hinged
fairings at the forward end of the pylon.
Lubrication System
The combining transmission contains an integrated
lubrication system that supplies the combining
transmission and both engine transmissions.
NO BREAK - WORK HARDER
Oil for the system is contained in a sump bolted to the
top of the transmission. The sump is divided into three
sections, one for the combining transmission and one for
each of the two engine transmissions. Oil is circulated by
a main and an auxiliary oil pump inside the transmission.
NO BREAK - WORK HARDER
The lubrication system is monitored and protected by
the following:
Two debris detection screens and a chip detector at
the lower forward end of the transmission. With
37 , a chip burnoff system lets the chip detector
burn off light fuzz and similar normal debris before
it activates indicators on the master caution and
maintenance panels.
NO BREAK - WORK HARDER
An inlet screen and a main filter on the sump cover.
NO BREAK - WORK HARDER
A temperature probe at the forward end of the sump.
NO BREAK - WORK HARDER
An auxiliary filter and a pressure switch at the forward
end of the transmission.
Hot oil from the transmission passes through a circular
oil cooler mounted on the sump cover under oil coolers
for the left and right engine transmission. The oil is
cooled by a fan that pulls air through the coolers. The
fan is driven by a vertical shaft that as driven by a gear
on the aft output shaft of the transmission.
ENGINE TRANSMISSION
The engine transmissions turn the direction of
engine torque 90º to direct it towards the combining
transmission.
NO BREAK - WORK HARDER
A one-way clutch in each transmission allows the drive
system to overrun the engines during autorotation or
a sudden reduction in engine rpm. Each of the two
engine transmissions is the same except for the location
of some external parts. Either transmission can be
converted to one for the opposite side by exchanging
the location of these parts.
Lubrication System
Each engine transmission is lubricated by oil from a
section of the combining transmission sump. Oil is
delivered to each transmission by a separate oil pump in
the combining transmission.
NO BREAK - WORK HARDER
Oil is carried between the combining transmission and
each engine by two external oil hoses. A vent hose
carries oil vapor from the transmission to the combining
transmission sump.
NO BREAK - WORK HARDER
The lubrication system is monitored and protected by
the following for each engine transmission:
A temperature probe and a debris detection screen
on the side of the combining transmission.
NO BREAK - WORK HARDER
A main filter on the back of the combining
transmission.
NO BREAK - WORK HARDER
An inlet screen and a pressure switch on the airframe
above and aft of the combining transmission. With
37 , the combined detector and switch is replaced
by a separate chip detector and plugstat. They
are part of a chip burnoff system that lets the chip
detector burn off light fuzz and similar normal
debris before it activates indicators on the master
caution and maintenance panels.
NO BREAK - WORK HARDER
A combined chip detector and overtemperature switch
at the bottom of the engine transmission.
Hot oil from each engine transmission is cooled in
a separate oil cooler mounted on the combining
transmission sump cover.
6-7
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