Figure 2-7-1. Transmission Main Oil Pressure Indicator and Selector Switch

Figure 2-7-2. Transmission Main Oil Temperature Switch and Indicator

TM-1-1520-240-10 Army CH-47D Heilcopter (EIC:RCD) Manual
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TM 1-1520-240-10 2-7-2 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 Switch. 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- cate zero. 2-7-8. Transmission Main Oil Temperature Indica- tor. 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 Switch 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-

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