Garmin Apollo CNX80 User Manual (English)

Questions and Answers:

L
lcoxAug 22, 2025
What to do if Garmin Apollo CNX80 GPS signal levels drop when avionics are turned on?
- R
  Rebecca RodriguezAug 22, 2025
  If the GPS signal levels of your Garmin GPS drop when you turn on your avionics, it is likely due to noise interference from other avionics. To find the source, turn off all avionics, and then turn them back on one by one to identify which device is causing the interference. Once identified, route the GPS cable and locate the GPS antenna away from that source of interference.
D
Denise SmithAug 23, 2025
How to fix Garmin Apollo CNX80 when it does not compute a position?
- N
  Nancy SnyderAug 23, 2025
  If your Garmin GPS (CNX80) is not computing a position, it could be due to not receiving signals or having an incorrect seed position, time, and date. To resolve this, ensure that a correct position and time/date have been entered. Also, check the GPS antenna connections and make sure the aircraft is clear of obstructions such as hangers, buildings, and trees.
J
Jennifer WatsonAug 25, 2025
How to troubleshoot a Garmin Apollo CNX80 (CNX80) that does not power on?
- A
  andrewandersonAug 26, 2025
  If your Garmin GPS CNX80 unit isn't powering on, it might not be getting power to the main connector P1. To fix this, ensure power is connected to the main 37-pin connector at P1-1 and 16, and ground to P1-2 and 20. Also, check the circuit breakers and the main avionics switch.
J
joshua68Aug 26, 2025
How to fix Garmin GPS message audio or tone when not heard?
- J
  Julian BartlettAug 27, 2025
  If you cannot hear the message audio or tone on your Garmin GPS (CNX80), it could be due to several reasons: the message audio volume level might be set too low, the message tone might be turned off, or the audio inhibit line could be grounded. To resolve this: * Increase the AMA volume level, which can be adjusted under the AUDIO menu in the COM function. * Turn the message tone ON via the system configuration page. * Verify that the inhibit input (P5-77) is not grounded using Ground Maintenance Mode.
H
Henry SchultzAug 27, 2025
What to do if Garmin GPS is not receiving baro correction data from MX20?
- C
  Cameron PatelAug 27, 2025
  If your Garmin GPS (CNX80) is not receiving baro correction data from the MX20, it may be due to an incorrect configuration for the serial port to MX20, using MX20 software prior to v5.x, or incorrect wiring connections. To solve this, go to the serial port setup page and verify that RS232 port 1 has MAPMX set for both CH 1 RX and CH 1 TX (only MX20 version 5.x or later supports the MAPMX protocol). Update the MX20 software if necessary and check the wiring.
S
Susan NelsonAug 29, 2025
Why is my Garmin Apollo CNX80 not receiving heading from compass system (ARINC 429 input)?
- J
  Jennifer FlowersAug 29, 2025
  If your Garmin GPS (CNX80) is not receiving heading information from the compass system using ARINC 429 input, the CNX80 ARINC 429 input might not be configured correctly, the ARINC 429 input port speed might be incorrect, or the wiring connections could be faulty. Check the ARINC 429 input port setting for the port that the device is connected to, verify that the ARINC 429 input port speed setting is correct for that device, and inspect the wiring.
L
Leah CoxAug 30, 2025
Why is my Garmin GPS not receiving heading from compass system (synchro heading input)?
- W
  William WilliamsAug 30, 2025
  If your Garmin GPS (CNX80) is not receiving heading from the compass system using synchro heading input, it could be due to an invalid Heading Valid input, an incorrect 26VAC reference voltage, or incorrect wiring connections. Verify that the heading valid input (P5-57) is greater than 9 VDC, which can be checked in Ground Maintenance Mode. Also, check that 26VAC, 400Hz reference is supplied to P5-20,39 and inspect the wiring.
A
Adam PetersonSep 1, 2025
What to do if ARINC 429 device is not receiving data from Garmin Apollo CNX80?
- D
  Debra JonesSep 1, 2025
  If an ARINC 429 device is not receiving data from the Garmin GPS (CNX80), the CNX80 ARINC 429 output might not be configured correctly, the ARINC 429 output port speed might be incorrect, or the wiring connections could be faulty. Check the ARINC 429 output port setting for the port that the device is connected to, verify that the ARINC 429 output port speed setting is correct for that device, and inspect the wiring.
I
imezaSep 2, 2025
How to fix RS232 device when is not communicating with Garmin Apollo CNX80 GPS?
- J
  Jacqueline OdomSep 2, 2025
  If an RS232 device is not communicating with the Garmin GPS (CNX80), it could be due to several reasons: the CNX80 RS232 port might not be configured correctly, there might be an improper setup on the remote device, the device might be incompatible or improperly connected, or there might be multiple Tx lines connected together. To troubleshoot this, check the RS232 port setting for the port that the device is connected to, verify the configuration of the other device, ensure that the CNX80 Rx is connected to the remote device Tx and the CNX80 Tx is connected to the remote device Rx, and verify that there is only one Tx source per Rx port.
S
Stanley RomeroSep 4, 2025
Why does my Garmin Apollo CNX80 GPS (CNX80) not transmit?
- C
  Christine MezaSep 4, 2025
  If your Garmin GPS CNX80 does not transmit, it could be due to the PTT input not being pulled low, no power to the com, or low input voltage. Check that the PTT (mic key) input is pulled low for transmit. Also, make sure power input is connected to the com 15-pin connector P4-1 and ground to P4-9. Finally, increase the input supply voltage to above 10 volts DC.

Garmin Apollo CNX80 Specifications

General

Brand	Garmin
Model	Apollo CNX80
Category	GPS
Language	English

Summary

General Information

About This Manual

Describes the installation and checkout procedures for the Apollo CNX80 Color GPS/Nav/Com.

Equipment Description

Details the Apollo CNX80 Color GPS/Nav/Com unit, its features, and system interfaces.

Specifications

Provides detailed electrical, physical, environmental, and performance specifications for the Apollo CNX80.

Regulatory Compliance

Outlines TSO, advisory circular references, FCC grant, and STC authorization.

Database Updates

Explains how to update the CNX80 database using a Compact Flash Memory datacard.

Installation

Pre-Installation Information

Provides essential information and practices to follow before starting the installation process.

Installation Overview

Outlines the general steps and considerations for a successful installation.

Materials Not Supplied

Lists materials and supplies required for installation that are not included with the CNX80.

Special Tools Required

Details specific tools necessary for making reliable crimp contact connections for D-sub connectors.

Installation Considerations

Covers important factors affecting installation, including system configuration and mounting.

Equipment Mounting

Describes the process of mounting the CNX80 unit in the avionics stack, including tube installation.

Electrical Connections

Details the electrical connections and interface connector definitions for the CNX80 unit.

Functional Descriptions

Explains the functionality of various outputs, inputs, and interfaces of the CNX80 unit.

Antenna Installation and Connections

Provides instructions for installing the Comm, GPS, and Nav antennas for optimal performance.

Electrical Load Analysis

Details the procedure for completing an electrical load analysis prior to aircraft installation.

Post Installation Configuration & Checkout Procedures

Mounting and Wiring Check

Verifies that all cables are securely connected and shields are properly installed.

Equipment Setup and Configuration

Guides the installer through configuring the CNX80 for the specific installation.

CNX80 Checkout Utilities

Provides utilities for checking the display, controls, and I/O of the CNX80 unit.

System Checkout – Ground Checks

Details the procedures for verifying CNX80 operation and GPS navigation on the ground.

VHF Nav Checkout

Describes how to check the functionality of the VHF Navigation receiver.

VHF Com Checkout

Provides steps to verify the performance of the VHF Communication transceiver.

Interface Checkout

Verifies proper communication between the CNX80 and interfaced systems.

System Checkout – Flight Checks

Outlines flight tests to verify system functions not adequately testable on the ground.

Database Check

Ensures the installed database is current and verifies its expiration status.

Troubleshooting

Troubleshooting Procedure

Provides a guide to identify and resolve common problems encountered with the CNX80.

Contacting the Factory for Assistance

Provides contact information for Garmin AT Technical Support for assistance.

Limitations

Operation

Details operational limitations, TSO authorizations, and system safety assessment guidance.

Installation

Covers installation requirements, compatibility, and limitations for aircraft integration.

Equipment Interfaced to the CNX80

States that interfaces beyond those shown are outside the manual's scope and may require further approval.

Periodic Maintenance

Equipment Calibration

States that no scheduled servicing tasks or internal manual adjustments are required.

VOR Checks

Requires VOR accuracy checks for IFR flight every 30 days per CFR 14 paragraph 91.171.

Battery Replacement

Details the internal battery lifespan and replacement procedure for the CNX80.

Appendix A - Certification Data

Environmental Qualification

Presents the environmental test conditions and results for the Apollo CNX80 per RTCA/DO-160D.

Appendix B - Serial Interface Specifications

Serial Input Specifications

Details the available RS-232 serial input configurations supported by the CNX80.

Fuel/Air Data Computer Input

Describes input formats for fuel/air data computers, including Shadin 'S' and 'Z' formats.

Serial Output Specifications

Lists available RS-232 serial output configurations supported by the CNX80.

Appendix C - Equipment Compatibility

Altitude Sources

Lists compatible altitude sources that meet serial or ARINC 429 specifications.

Autopilots

Lists compatible autopilots that meet Nav mode and analog deviation data specifications.

Appendix D - Interconnect Diagrams

Appendix E - Acceptable Aircraft by Evaluation

Appendix F - Optional Accessories Not Supplied

CDI/HSI Source Selection Annunciators

Lists suitable indicators and switches for CDI/HSI source selection annunciation.

Related product manuals

Garmin Apollo CNX80 User Manual

Table of Contents

Questions and Answers:

Garmin Apollo CNX80 Specifications

Summary

General Information

About This Manual

Equipment Description

Specifications

Regulatory Compliance

Database Updates

Installation

Pre-Installation Information

Installation Overview

Materials Not Supplied

Special Tools Required

Installation Considerations

Equipment Mounting

Electrical Connections

Functional Descriptions

Antenna Installation and Connections

Electrical Load Analysis

Post Installation Configuration & Checkout Procedures

Mounting and Wiring Check

Equipment Setup and Configuration

CNX80 Checkout Utilities

System Checkout – Ground Checks

VHF Nav Checkout

VHF Com Checkout

Interface Checkout

System Checkout – Flight Checks

Database Check

Troubleshooting

Troubleshooting Procedure

Contacting the Factory for Assistance

Limitations

Operation

Installation

Equipment Interfaced to the CNX80

Periodic Maintenance

Equipment Calibration

VOR Checks

Battery Replacement

Appendix A - Certification Data

Environmental Qualification

Appendix B - Serial Interface Specifications

Serial Input Specifications

Fuel/Air Data Computer Input

Serial Output Specifications

Appendix C - Equipment Compatibility

Altitude Sources

Autopilots

Appendix D - Interconnect Diagrams

Appendix E - Acceptable Aircraft by Evaluation

Appendix F - Optional Accessories Not Supplied

CDI/HSI Source Selection Annunciators

Related product manuals