G900X/G950 Installation and Maintenance Manual – GDC 74A
Page 6-7
190-00719-00
Revision
D
6.6.2 Pneumatic
Plumbing
The GDC 74A has two ports that are connected to the aircraft’s pitot pressure source and static pressure
source. The two ports are labeled on the unit. Pressure ports have 1/8-27 ANPT female threads, all
fittings should have 1/8-27 ANPT male threads.
GDC 74A (011-00882-10)
Pitot Air Port
Static Air Port
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Figure 6-1. GDC 74A Air Hose Fitting Locations
Use appropriate air hoses and fittings to connect the pitot and static lines to the unit. Avoid sharp bends
and routing near aircraft control cables. The GDC 74A should not be at the low point of the pitot or static
plumbing lines, to avoid moisture or debris collecting at or near the unit. Ensure that no deformations of
the airframe surface have been made that would affect the relationship between static air pressure and true
ambient static air pressure for any flight condition. Refer to part 43, Appendix E for approved practices
while installing hoses and connections.
6.6.3 GTP 59 Icing
The GTP 59 OAT probe has no icing protection. If ice accumulates on the GTP 59 OAT probe, its
accuracy is unknown. Consequently, air temperature measurements may be incorrect if ice accumulates
on the probe. Furthermore, computations dependent upon air temperature measurements may be affected
(e.g. true airspeed and delta-ISA).
