Page 5-24
GTN 725/750 TSO Installation Manual
Rev. A
190-01007-02
5.6.4
VHF NAV Checkout (GTN 750 Only)
Touch the CDI key to select VLOC mode, which is indicated by a green ‘VLOC’ annunciation on the
bottom center of the display. Check the VOR reception with ground equipment, operating VOT or VOR,
and verify audio and Morse code ID functions (if possible). Tune a Localizer frequency and verify the
CDI needle and NAV flag, and VDI needle and GS flag operation.
5.6.5
VHF COM Checkout (GTN 750 Only)
5.6.5.1 Antenna
Check
If desired, the antenna VSWR can be checked using an inline wattmeter in the antenna coax using
frequencies near both ends of the band. The VSWR should be < 2:1. A VSWR of 2:1 will cause a drop in
output power of approximately 12%.
5.6.5.2 Receiver/Transmitter
Operation
Tune the unit to a local VHF frequency and verify the receiver output produces a clear and
understandable audio output. Verify the transmitter functions properly by contacting another station and
getting a report of reliable communications.
5.6.6
TAWS System Check (For Units with TAWS Only)
While on the ground, turn on the GTN following normal power-up procedures. Also turn on the audio
panel.
NOTE
A 3D GPS position fix is required to conduct this check.
1.
Select the TAWS page.
2.
Touch the MENU button.
3.
Select the Test Terrain? field and press the ENT key.
4.
Wait until the TAWS self-test completes (10-15 seconds) to hear the TAWS system status aural
message.
•
The aural message “TAWS System Test OK” will be annunciated if the TAWS system is
functioning properly.
•
The aural message “TAWS System Failure” will be annunciated if the TAWS system is
NOT functioning properly.
If no audio message is heard, then a fault exists within the audio system and the TAWS capability must
be considered non-functional.
Summary of Contents for GTN 725
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