Periodic Maintenance; Equipment Calibration; Cleaning; Battery Replacement - Garmin GDL 90 Installation Manual

6 Periodic Maintenance

This section contains information on periodic calibration and maintenance required for continued
airworthiness.
6.1

Equipment Calibration

No scheduled servicing tasks or internal manual adjustments are required on the GDL 90.
6.2

Cleaning

The GDL 90 does not require regular cleaning.
6.3

Battery Replacement

The GDL 90 includes an internal battery that will last about 10 years. The battery is used for internal
RAM memory and GPS system information. Regular planned replacement is not necessary. The GDL 90
Maint. LED will be lit when replacement is required. To verify that the battery needs replacing, use the
"Service" command in Maintenance Mode. Once low battery is confirmed, the battery should be
replaced within 1 to 2 months.
If the battery is not replaced and becomes totally discharged, the GDL 90 will remain fully operational,
but the GPS signal acquisition time will be increased. There is no loss of function or accuracy of the
GDL 90 with a discharged battery.
The battery is not user-replaceable. To replace the battery, contact the Garmin AT repair station.
6.4

Altitude Source

The altitude source provided to the GDL 90 must be tested and inspected every 24 months, as described
in FAR 91.411. Refer to the manufacturer's calibration or installation manual. The Maintenance port "alt"
command may be used as described in Part 43 Appendix E paragraph (c) as a method to measure the
automatic pressure altitude data.
6.5

Audio Alerts

If GDL 90 audio alerts are used in the installation, test that the audio level is set correctly. Use the
"playaudio" maintenance command, or activate the IDENT function while the aircraft is on ground, if
this feature is enabled. (See "Audio Ground Test" APM configuration setting)
GDL 90 Installation Manual 560-1049-02 Rev. B
Periodic Maintenance
6-1