6.7 Communication, Navigation, Antennas, and Avionics Inspection

Communication and Navigation: Installation Quality Drives Reliability

Communication and navigation systems include radios, antennas, coaxial cables, intercoms, emergency locator transmitters, navigation receivers, GPS, VOR, DME, ILS, transponders, ADS-B, TCAS, weather radar, radio altimeters, autopilots, and related displays or controllers. The Airframe ACS does not expect guessing at hidden active test questions. It expects understanding of operating principles, components, inspection points, and risk controls.

Many avionics discrepancies are installation problems. A radio that transmits poorly may have antenna, coax, bonding, connector, power, microphone, or equipment faults. A navigation receiver complaint may involve antenna location, coax loss, water intrusion, connector condition, configuration, or interference. A transponder or ADS-B fault may involve encoder data, antenna, wiring, configuration, or power.

Study avionics inspection with this list:

• Verify required placards and equipment identification.
• Inspect equipment racks, mounting trays, shock mounts, cooling, and security.
• Inspect antennas for correct mounting, sealant, corrosion, bonding, and physical damage.
• Inspect coaxial cable for routing, bend radius, chafing, connector condition, and security.
• Check bonding jumpers and static discharge wicks for security and resistance when required.
• Follow approved procedures for ELT tests and battery expiration checks.
• Respect high-power systems such as weather radar, HF, and SATCOM.

Antennas are not decorative parts. They depend on correct location, ground plane or bonding as applicable, structural mounting, sealing, coax connection, and protection from damage. A loose antenna can be both an electrical fault and a structural or water-entry problem. Static discharge wicks help dissipate static charge; missing or high-resistance wicks can contribute to radio noise or static problems.

Coaxial cable inspection is a common practical skill. Coax should be secured, protected from chafing, routed away from heat and interference sources as directed, and connected with proper fittings. Tight bends, crushed cable, corrosion, moisture, or loose connectors can degrade signal quality. Wire harness routing is a risk-management item because poor routing can lead to chafing, arcing, interference, or intermittent faults.

Emergency locator transmitter work requires exact procedure. Testing is limited by regulation and manufacturer instructions to avoid false alerts and to verify proper operation. The battery expiration date and replacement criteria must be checked. A hard landing or maintenance event may require inspection based on aircraft data.

Autopilot and stability systems connect avionics to flight controls. Maintenance includes identifying major components, inspecting servos, brackets, wiring, connectors, and control linkages, and following operational-check procedures. Incorrect installation or rigging can create serious control risk.

For exam questions, prefer answers that inspect installation quality, protect electrostatic-sensitive equipment, control live electrical and high-power hazards, and use the aircraft procedure for operational checks. Avionics reliability often depends on basic airframe maintenance discipline: security, bonding, routing, sealing, and documentation.

Navigation complaints should be tied to the phase of operation and equipment path. A fault that appears only in rain may point to moisture at an antenna or connector. A fault after interior work may point to harness routing or bonding. The technician narrows the system before disturbing calibrated equipment.