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Enstrom TH-28/480 Series Maintenance Manual Supplement 8
G1000H Integrated Flight Deck System
Rev. 1, Jan 25/18
Page
1-37
GDC 74H Air Data Computer (Figure 25)
1.5.6.1 Scheduled
Maintenance
The GDC 74H is subject to conditional maintenance with the exceptions described in
Section 7 of the G1000H Integrated Avionics System Standard Maintenance Manual.
1.5.6.2 Removal
A. Remove power to the GDC 74H. Pull the ADC circuit breakers out (emergency
circuit breaker panel also). Disable the circuit breaker by installing a cable tie or
other similar device around the circuit breaker stem.
B. Access the GDC 74H by removing the PFD (para. 1.5.1.2).
C. Hold the LRU firmly in hand and remove 4x MS24693-274 screws and 4x
NAS1149FN832P washers from the unit.
D. Loosen the jackscrews holding the backshell to the LRU. Remove the connector
from the back of the unit.
CAUTION
Use care to avoid getting fluids or particles anywhere within the pitot and
static lines connected to the GDC 74H.
D. Disconnect the pitot-static plumbing from the unit. Remove Teflon tape or sealing
compound. Cap the openings on the GDC 74H if it is to be reinstalled.
1.5.6.3 Installation
A. Inspect connector(s) and pitot-static plumbing for damage.
B. Connect the pitot-static plumbing to the unit. Seal the connections, as required.
C. Connect the backshell and connector to the unit and fasten jackscrews.
D. Fasten the unit to the tray with 4x MS24693-274 screws and 4x NAS1149FN832P
washers.
E. Reinstall the PFD (para. 1.5.1.3).
F. Remove the cable tie or other similar device from the ADC circuit breaker stem and
push the stem in to set the circuit breaker.
G. Perform the GDC 74H testing (and field calibration, if required) procedure in
accordance with Section 6 of the G1000H Integrated Avionics System Standard
Maintenance Manual.
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