Abnormal Com Operation; Stuck Microphone; Com Tuning Failure; Audio Panel Fail-Safe Operation - Garmin G1000 NXI Cockpit Reference Manual

aBNoRMaL CoM oPERaTIoN

STUCK MICRoPHoNE

If the push-to-talk (PTT) Key becomes stuck, the COM transmitter stops transmitting after
35 seconds of continuous operation. An alert appears in the Alerts Window on the PFD to
advise the crew of a stuck microphone.
The COM1 MIC or COM2 MIC Key Annunciator on the Audio Panel flashes as long as the
PTT Key remains stuck.

CoM TUNING FaILURE

In case of a COM system tuning failure, the emergency frequency (121.500 MHz) is auto-
matically tuned in the radio in which the tuning failure occurred. Depending on the failure
mode, a red X may appear on the frequency display.

aUdIo PaNEL FaIL-SaFE oPERaTIoN

If there is a failure of the Audio Panel, a fail-safe circuit connects the pilot' s headset and
microphone directly to the COM1 transceiver.

REVERSIoNaRy ModE

The red DISPLAY BACKUP Button selects the Reversionary Mode. .

dEad RECKoNING NaVIGaTIoN

While in Enroute or Oceanic phase of flight, if the system detects an invalid GPS solution
or is unable to calculate a GPS position, the system automatically reverts to Dead Reckoning
(DR) Mode. In DR Mode, the system uses its last-known position combined with continuously
updated airspeed and heading data (when available) to calculate and display the aircraft' s cur-
rent estimated position.
It is important to note that estimated navigation data supplied by the system in DR Mode
may become increasingly unreliable and must not be used as a sole means of navigation. If
while in DR Mode airspeed and/or heading data is also lost or not available, the DR function
may not be capable of accurately tracking estimated position and, consequently, the system
may display a path that is different than the actual movement of the aircraft. Estimated posi-
tion information displayed by the system through DR while there is no heading and/or airspeed
data available should not be used for navigation.
DR Mode is inherently less accurate than the standard GPS/SBAS Mode due to the lack of
satellite measurements needed to determine a position. Changes in wind speed and/or wind
direction compound the relative inaccuracy of DR Mode. Because of this degraded accuracy,
other navigation equipment must be relied upon for position awareness until GPS-derived
position data is restored.
DR Mode is indicated on the system by the appearance of the letters 'DR' superimposed
in amber over the 'own aircraft' symbol as shown in the following figure. In addition, 'DR' is
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