(20)
If a difference exceeding 10°C occurs between the left and right IDG oil temperatures, an EICAS message IDG OUT TEMP will display on the maintenance page.
(21)
If an oil temperature sensor failure occurs, a L (or R) IDG TEMP SENS EICAS message is displayed on the maintenance page. The L (or R) IDG TEMP SENS EICAS message will inhibit the L (or R) IDG OIL TEMP and the IDG RISE TEMP EICAS messages so a faulty oil temperature sensor will not cause nuisance IDG oil temperature EICAS messages.
(22)
The maintenance page of EICAS displays IDG oil out temperature, and IDG oil rise temperature. The rise temperature is the difference between oil-out temperature and oil-in temperature. The rise temp is continuously monitored by the corresponding generator control unit. A timer is set to display the most recently calculated rise temperature every 0.55 seconds. (The timer is in right side panel P61). If the difference between the two IDG rise temperatures is greater than 10°F (6°C), for more than 5 minutes, an EICAS message is displayed on the maintenance page: IDG RISE TEMP. (Both engine generators must be running for this message to be displayed. The EICAS message is stored in memory, and an ELEC AUTO EVENT occurs in the EICAS system.)
(23)
IDG Servicing Features (Fig. 4).
(a) An indicator is provided to show when the oil level is low. The indicator has a prism inside the IDG that reflects light back to the viewer when it is not covered with oil. When the prism is covered with oil, the light is absorbed into the oil and not reflected back to the viewer. Therefore, when there is no silver spot in the viewing area, the IDG has enough oil and oil servicing is not required. When there is a silver spot (large or small) in the viewing area, the oil level is low and the IDG requires servicing.
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MAINTENANCE MANUAL
PROPER
MINIMUM ACCEPTABLE OIL LEVEL
LOW OIL LEVEL
SEE
B
REQUIRED REQUIRED
ANY SILVER SPOT ____LARGE OR SMALL -
NOTE: BOTH TYPES OF PRISMS ARE PRESENTLY IN USESERVICING REQUIRED
LOW OIL LEVEL INDICATOR PRISM
B
A54536
IDG Servicing Features
Figure 4
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(b)
The low oil level indicator can operate on low levels of light. Light sufficient to see the white alignment marker is all the light that is needed to view the indicator. Shining a flashlight (or other light source) directly into or onto the viewing face can induce too much light and cause reflections resulting in incorrect interpretation of the indicator.
(c)
The indicator viewing face must be clean before attempting to view the indicator. A dirty viewing face (and back face in early configured indicators) can also cause reflections resulting in incorrect interpretation.
(d)
Filling the IDG through the pressure fill valve causes oil to first flow through the IDG scavenge filter, then through the external oil circuit, and into the IDG case. Air that is in the circuit is forced out ahead of the oil and escapes through the overflow drain. The oil level rises in the IDG sump until the oil level rises above the top of the standpipe and then flows from the overflow drain.
(e)
The overflow drain establishes the proper fill level for the IDG oil system. The IDG oil level is correct when oil overflows from the overflow drain and then slows to drops. The overflow standpipe establishes the maximum oil level in the IDG case.
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