Garmin GNC 255, Installation Manual, Page: 73 / 138

190-01182-02 GTR 225/GNC 255 TSO Installation Manual
Rev. B Page 6-19
6.7 Flight Checks
6.7.1 COM Flight Check
After the installation is complete, a flight check is required to ensure satisfactory performance. To check
the communications transceiver, maintain an appropriate altitude and contact a ground station facility at a
range of at least 50 nautical miles. Contact a ground station in close proximity. Press the COM volume
knob to select manual squelch and listen for any unusual electrical noise, which would increase the squelch
threshold. If possible, verify the communications capability on both the high, low, and mid bands of the
VHF COM band. It may be required by the governing regulatory agency to verify operation of the COM
transmitter and receiver at the extents of a ground facility’s service volume (e.g. FAA AC 23-8A).
6.7.2 VOR Flight Check (GNC Only)
1. Tune a local VOR station within 50 miles.
2. Verify the audio IDENT and voice quality and verify that no objectionable electrical interference
such as magneto noise is present.
3. Verify the Morse code decoder IDs the station (95% probability).
4. Fly to and from the station.
5. Verify NAV flag, TO/FROM flag, and CDI are operational.
It may be required by the governing regulatory agency to verify operation of the VOR receiver at the
extents of a ground facility’s service volume (e.g. FAA AC 23-8A).
6.7.3 ILS Flight Check (GNC Only)
1. Tune an ILS at a local airport.
2. Verify the audio IDENT and audio quality and verify that no objectionable electrical interference
such as magneto noise is present.
3. Verify the Morse code decoder IDs the station (95% probability).
4. Fly the approach.
5. Verify NAV flag, GS flag, and CDI and VDI are operational.