(3)
Check the thermocouple harness and lead for shorts to ground. Resistance shall not be less than 50,000 ohms.
(4)
Remove ohmmeter and reconnect harness leads to the engine terminal strip.
(5)
Close engine cowl panels.
500
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500 Exhaust Gas Temperature Indicating System Terminal Strip
Feb 01/75 Figure 501 77-21-01
Page 503
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
4. Operational Test No. 1 (Preferred)
A. Open left side cowl panel (Ref 71-11-11).
B. Disconnect indicator leads (Alumel-green and Chromel-white) from terminal strip (Fig. 501).
C. Connect millivolt source to airplane wiring at thermocouple terminal strip.
D. Immerse junction of millivolt source and thermocouple terminal strip in ice bath (Fig. 502).
E. Energize AC STANDBY BUS and close applicable engine EGT circuit breaker EGT IND. Allow at least 5-minute warmup before proceeding with test.
F. Apply voltages and observe indicator readings (Fig. 502). Lightly tap front of indicator before taking readings.
G. Voltage shall be within the limits of Fig. 502. The pointers shall move smoothly throughout all testing.
H. De-energize AC STANDBY BUS and open applicable engine EGT circuit breaker EGT IND.
I. Disconnect millivolt source from airplane wiring.
J. Connect indicator leads to terminal strip.
K. Close left side cowl panel (Ref 71-11-11).
5. Operational Test No. 2 (Option 1)
A. Perform steps 4.A thru C.
B. Record ambient temperature from cockpit indicator.
C. Add ambient temperature from step 5.B. to each indicator reading in Fig. 502.
D. Perform steps 4.E. thru K.
500
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500 Exhaust Gas Temperature Indicating System
Jan 20/82 Operational Test Requirements 77-21-01
Figure 502 Page 505
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6. Operational Test No. 3 (Option 2)
A. Perform steps 5.A thru C.
B. Record temperature of the terminal strip. For each degree (C) subtract 0.04 mv from the millivolt input values shown in Fig. 502.
NOTE: For example, if the terminal strip temperature is 11°C, subtract 0.44 millivolts from the values shown in Fig. 502.
C. Perform steps 4.E. thru K.
7. Thermocouple Functional Check
A. Heat one of the engine thermocouple probes with a hot soldering iron, or hot air from a heat blower gun.
WARNING: HEAT GUNS, SOLDERING GUNS AND SOLDERING IRONS ARE NOT EXPLOSION-PROOF. DO NOT USE WHERE FUEL OR FUEL VAPOR IS PRESENT (REF MM 20-10-171, MP).
B. Observe indicator for a temperature rise indication. If indication decreases, then the
thermocouple is connected in reverse.
C. Repeat steps 7.A. and B. for each thermocouple. This procedure will determine if each thermocouple is functioning correctly.
NOTE: The thermocouples are located in approximately the center of the probe. The soldering iron should, therefore, be placed on the probe at the center to assure adequate heat transfer to give the indication.
8. Failure Indication Test
A. Energize AC STANDBY BUS and open applicable engine EGT circuit breaker EGT IND.
B. The pointer shall go to the off scale position for expanded scale indicators. A flag shall appear over the counter for the pointer/counter indicators.
C. Close applicable engine EGT circuit breaker EGT IND and de-energize AC STANDBY BUS.
D. The pointer (counter) shall return to its former position and the flag shall disappear from view for the pointer/counter indicators.
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EXHAUST GAS TEMPERATURE INDICATING SYSTEM (SERVOED) -INSPECTION/CHECK
1. Exhaust Gas Temperature Indicating System Check
A. General
(1)
Engine compartment cleanliness is important because the extensive mass airflow tends to draw foreign objects into the engine. Thoroughly clean the entire engine compartment with a vacuum cleaner after completion of any work. Keep the compartment and the annular duct free of dirt, oil and grease, and remove all unused parts, such as nuts, washers, and pieces of lockwire. Immediately cover all apertures resulting from the disconnection of parts. Use external caps on all openings, not internal plugs.
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