No. 2 engine transmission oil reservoir on the combining
(mix) transmission through the right pump assembly, fil-
ter, cooler, jet protection screen, and to the jets which
spray the oil onto the various gears and bearings. One of
the scavenge elements of the right pump assembly re-
turns the oil from the No. 2 engine transmission sump
through a debris indicating screen and back to the No. 2
engine transmission oil reservoir. Engine transmissions
do not have auxiliary lubrication systems.
All No. 1 and No. 2 engine transmission lubrication sys-
tem components are on the combining (mix) transmis-
sion except the jet protection screen and jets. Separate
oil jets are utilized for each transmission lubrication oil
system. The individual oil cooler for the combining (mix)
and both engine transmissions are mounted on the com-
bining (mix) transmission and utilize a common transmis-
sion driven fan for cooling air.
2-7-6. Transmission Main Oil Pressure Indicator.
A transmission main oil pressure indicator is located on
the center instrument panel (fig. 2-7-1). It indicates either
the lowest main oil pressure in any one of the transmis-
sions or only the oil pressure in the transmission selected
by the pilot. The indicator is electrically connected to
each transmission. In addition, each transmission and
the aft rotor shaft bearing has a separate low pressure
switch. These switches are connected to the XMSN OIL
PRESS caution capsule on the master caution and the
TRANSMISSION MAIN OIL PRESS indicating lights on
the MAINTENANCE PANEL (fig. 2-10-1). Power to oper-
ate the indicator is supplied by the No. 1 AC bus through
the XMSN OIL PRESS circuit breaker on the No. 1 PDP.
2-7-7. Transmission Main Oil Pressure Selector
A transmission oil pressure selector switch is located on
the center instrument panel (fig. 2-7-1). The switch posi-
tions are labeled TEST, SCAN, FWD, AFT, MIX, LEFT,
and RT. When the switch is set to TEST, the pointer on
the transmission pressure indicator will drop to zero or
below. When the switch is set to SCAN, the lowest main
oil pressure among all the transmission will be indicated.
The remaining positions are used to select a particular
transmission oil pressure indication. When selecting a
particular switch position, be sure the switch is in detent.
If the switch is not in detent, the pressure gage will indi-
2-7-8. Transmission Main Oil Temperature Indica-
A transmission oil temperature indicator is located on the
center instrument panel (fig. 2-7-2). It reads from 70_ to
+150_C. It indicates the highest oil temperature among
all the transmissions or only the oil temperature of the
selected transmission. A temperature probe is located in
the forward and aft transmission sumps and in each
compartment of a three-compartment oil tank for the
combining (mix) transmission and in each engine trans-
mission. The temperature probes in the three tank
compartments measure oil temperature in the tank and
may not immediately indicate a transmission problem.
Loss of oil or low oil pressure may not be accompanied
by high oil temperature indication.
Figure 2-7-1. Transmission Main Oil Pressure
Indicator and Selector Switch
Each temperature probe incorporates a high oil tempera-
ture switch which is independent of the temperature indi-
cator and is triggered at 140_C, lighting the XMSN OIL
HOT caution capsule on the master caution panel and to
the TRANSMISSION OVERTEMP magnetic indicator on
the MAINTENANCE PANEL. Power to operate the indi-
cator is supplied by the No. 1 AC bus through the XMSN
OIL TEMP circuit breaker on the No. 1 PDP.
2-7-9. Transmission Main Oil Temperature Selector
A transmission oil temperature selector switch is on the
center panel below the transmission oil temperature indi-
cator (fig. 2-7-2). The switch positions are labeled TEST,
SCAN, FWD, AFT, MIX, LEFT, and RT. When the switch
is set to TEST, the pointer on the transmission oil temper-
ature indicator deflects full scale toward low temperature.
.When the switch is set to SCAN, the highest oil tempera-