Inter−Turbine Temperature Indicator (Itt) Calibration Test - De Havilland DASH8 100 Series Maintenance Manual

**ON A/C ALL
INTER−TURBINE TEMPERATURE INDICATOR (ITT) CALIBRATION TEST − MAINTENANCE
1. Adjustment/Test
Equipment and Materials:
Millivolt Generator−Pyrotest V2777 (or equivalent)
A. Inter−Turbine Temperature Indicator (ITT) Calibration Test
(1) Open and clip the following circuit breakers:
(a) ENG 1 ITT IND (F5) on 28V dc left essential bus circuit breaker panel (when
testing engine No. 1 indicator).
OR
(b) ENG 2 ITT IND (F5) on 28V dc right essential bus circuit breaker panel (when
testing engine No. 2 indicator).
(c) ADVSY LTS 1 (F3) on 28V dc left essential bus C.B. panel and ADVSY LTS 2
(E3) on 28V dc left main bus circuit breaker panel.
(2) Gain access to engine terminal block through the cowl right rear access panel. At
engine terminal block (TC1) (refer to Figure 203) disconnect thermocouple harness
and connect millivolt generator.
NOTE:
(3) Check with no voltage applied to indicator, indicator pointer is off scale and digital
readout is blank.
(4) Close circuit breakers opened in step (1).
(5) Press test pushbutton on indicator and check overtemperature warning light on at
810 degrees C pointer positions opposite blue dot at 1050 degrees C and
equivalent digital reading. Release pushbutton and check pointer and digital
readout return to original readings.
(6) Apply millivolt signal to harness (refer to Figure 201) corrected for ambient
temperature as necessary (refer to Figure 204) and record readings.
(7) At each reading taken in step (6) ensure that indicator readings pointer and digital
are within tolerances given in Figure 204.
(8) Adjust signal input to increase pointer and digital display to approximately 810
degrees C and observe overtemperature warning light comes on (refer to Figure
204).
(9) Open circuit breakers (refer to step (1)).
(10) Disconnect millivolt generator from thermocouple leads.
CAUTION:
(11) Carry out continuity, insulation resistance and voltage output check of T6
thermocouples, harness and T6 trim resistor harness (refer to Engine Maintenance
MASTER
EFFECTIVITY: See Pageblock 77−20−11 page 201
D
S ERIES 100
AIRCRAFT MAINTENANCE MANUAL
PRACTICES
Ensure correct polarity of alumel and chromel leads.
WHEN DOING AN INSULATION RESISTANCE CHECK, DO NOT
APPLY A VOLTAGE HIGHER THAN 500 VOLTS, WHICH IS THE
BREAKDOWN VOLTAGE OF THE SYSTEM.
77−20−11
Dec 20/2004
Page 201