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Garmin GNC 355 - User Manual

Garmin GNC 355
290 pages
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GPS 175
GNC 355
GNX 375
Pilot's Guide

Table of Contents

Other manuals for Garmin GNC 355

Questions and Answers

  • T
    Tyler Williams DDSSep 8, 2025
    Why won't my Garmin GNC 355 GPS 175 OBS resolver calibrate?
    • J
      Jeffrey BrownSep 8, 2025
      If your Garmin GPS 175 OBS resolver won't calibrate, the issue is likely due to an incompatible resolver or an improper connection. Check the resolver specifications and wiring to ensure they are correct.
  • M
    Mark JacksonAug 23, 2025
    What to do if my Garmin GNC 355 GPS/GNX/GNC does not compute position?
    • K
      Kevin CainAug 23, 2025
      If your Garmin GPS 175, GNX 375, or GNC 355 is not computing its position, the issue might be due to inadequate GPS signals. Check the GPS antenna connections to ensure they are secure. Also, make sure the aircraft is in a location free from obstructions such as hangars, buildings, or trees.
  • M
    michael11Aug 25, 2025
    Why does Garmin GNC 355/GNX/GNC signal drop when avionics are turned on?
    • A
      Angela RhodesAug 25, 2025
      If the GPS signal level of your Garmin GPS 175, GNX 375, or GNC 355 drops when avionics are turned on, it's likely due to noise interference from other avionics. To address this, turn off all other avionics and then turn them back on one at a time to identify the source of the interference. Reroute the GPS cable and reposition the GPS antenna away from the interfering unit.
  • P
    Peter WoodsAug 26, 2025
    Why are Garmin GNC 355 GPS signal levels very low?
    • M
      Mr. Louis SwansonAug 27, 2025
      If the GPS signal levels on your Garmin GNC 355 are very low, this could be due to several reasons. First, check the GPS antenna installation, connections, and cable routing, ensuring the antenna is mounted on top of the aircraft. Second, ensure the aircraft is clear of obstructions like hangars, buildings, or trees. Third, RF interference at 1575.42 MHz from VHF COM can be the cause. Add a 1575.42 MHz notch filter in COM coaxial. Fix or replace the COM. Disconnect the ELT antenna coaxial to check for possible re-radiation. Move GPS antenna further from the COM antenna.
  • A
    Angela JohnsonAug 27, 2025
    Why are Garmin GNC 355 GPS 175 GPS signal levels very low?
    • M
      marybuckleyAug 27, 2025
      If the GPS signal levels on your Garmin GPS 175 are very low, it could be due to improper antenna installation or the antenna being shaded. Check the GPS antenna installation, connections, and cable routing, ensuring the GPS antenna is mounted on the top of the aircraft. Also, make sure the aircraft is clear of obstructions like hangars, buildings, or trees.
  • M
    miguelfitzgeraldSep 22, 2025
    How to adjust COM sidetone level on Garmin GNC 355?
    • R
      Rachel MillerSep 22, 2025
      If the COM sidetone level on your Garmin GNC 355 is too low or too high, it could be due to using the wrong type of headsets or because the sidetone level needs adjustment. If necessary, adjust the sidetone level on the COM Setup Config Mode page.
  • S
    Susan GibsonSep 16, 2025
    How to correct incorrect Mode S aircraft data transmitted by Garmin?
    • V
      victoriasingletonSep 16, 2025
      If your Garmin system is transmitting incorrect Mode S aircraft data, the problem might be an incorrect Flight ID configuration. Check the Flight ID Configuration page and verify that the settings are configured correctly.
  • K
    Kristina LoveSep 18, 2025
    Why does Garmin GNC 355 COM not transmit?
    • S
      smithkellySep 18, 2025
      If the Garmin GNC 355 COM does not transmit, there might be several reasons: 1. The PTT input is not being pulled low. Check that the MIC 1 Transmit (P3552-11) input is pulled low for transmit; the state of this discrete input can be monitored on the Discrete Inputs page found on the GNC Diagnostics page. 2. There is no transmit power to COM. Ensure power input is connected to the COM 44-pin connector P3552—30, -43, and -44, and ground to P3552-37, -38, and -40. 3. The input voltage is too low. Increase the input supply voltage to >11VDC.
  • S
    Suzanne SchaeferSep 7, 2025
    Why is my Garmin GNC 355 not receiving heading from compass system?
    • C
      Claudia PrinceSep 7, 2025
      If your Garmin GNC 355 is not receiving heading from the compass system (ARINC 429 heading input), this could be due to an incorrect ARINC 429 input speed setting or incorrect wiring connections. Check the ARINC 429 input port speed setting for the device and verify it is correct. You should also check the wiring connections; the raw data being received by the GNC 355 can be monitored on the ARINC Inputs page found on the Diagnostics page.
  • L
    Lauren WilsonSep 4, 2025
    Why is my Garmin GNC 355 175 not receiving heading from compass system?
    • G
      ginabanksSep 4, 2025
      If your Garmin GPS 175 is not receiving heading from the compass system (ARINC 429 heading input), it could be due to an incorrect ARINC 429 input speed setting or incorrect wiring connections. Verify the ARINC 429 input port speed setting for the connected device. Also, check the wiring connections; the raw data received by the GPS 175 can be monitored on the ARINC Inputs page found on the Diagnostics page.

Summary

System at a Glance

Overview

General description of the GPS 175, GNC 355/355A, and GNX 375 navigators and their features.

Pilot Interface

Details the physical components and controls of the unit, including bezel, touchscreen, knobs, and keys.

Compatible Equipment

Lists required and optional Line Replaceable Units (LRUs) and interfaces compatible with the system.

Get Started

Power Up

Describes the initial power-on sequence, software versions, and database status checks.

Databases

Explains database updates via SD card or Flight Stream, supported types, and effective cycles.

Connectivity

Details how Connext works via Bluetooth, enabling features like GPS position and flight plan transfer.

Navigation

Map

Explains the map display features, aircraft symbol, track vector, basemap, and overlays.

Active Flight Plan

Details how current flight plan information is displayed as a scrolling list on the Active Flight Plan page.

Direct To

Explains how to set a course to any waypoint using the Direct To function with various selection methods.

Waypoints

Describes database and user waypoints, including search functions and specific page features.

Procedures

Explains how to load and manage departure, arrival, and approach procedures for flight plans.

Planning

Vertical Calculator

Describes how to calculate time to TOD and vertical speed required to reach a target altitude.

Fuel Planning

Explains how to view and compute fuel conditions along a flight plan or between waypoints.

DALT;TAS;Wind Calculator

Details how to calculate density altitude, true airspeed, and winds based on input variables.

RAIM Prediction

Explains how to determine GPS coverage availability and predict fault detection integrity.

Hazard Awareness

Weather Awareness

Covers FIS-B weather products, display, data limitations, and reception.

Traffic Awareness

Explains ADS-B In traffic applications (AIRB, ATAS, SURF), features, and display.

Terrain Awareness

Details terrain and obstacle depictions, including color shading, proximity, and alerting functions.

Messages

Advisory Messages

Explains system-related messages, their display, logging, and message key.

Database Advisories

Lists advisories related to database issues, their conditions, and corrective actions.

Flight Plan Advisories

Covers advisories for flight plan import, storage, and changes, with corrective actions.

GPS;WAAS Advisories

Details advisories for GPS receiver issues, loss of integrity, and navigation errors.

System Hardware Advisories

Lists advisories for hardware faults, temperature issues, data loss, and component failures.

Qualification

Glove Qualification

Explains how to qualify gloves for touchscreen use, including selection considerations and guidance.

Regulatory Information

Compliance

States that the Garmin unit meets FAA AC 90-100A requirements for RNAV operations.

Garmin GNC 355 Specifications

General IconGeneral
Channels200
InterfaceRS-232
GPS ReceiverWAAS
ConnectivityBluetooth
Display TypeColor
ApproachesLPV/LNAV/VNAV/GPS

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