Installing the ELT 110-4 Is More About Wiring Than the Radio Itself

Most people treat the Artex ELT 110-4 like it just clips in and works. That is wrong. The unit itself is dead simple. It is a self-contained 406 MHz distress transmitter with an integrated G-sensor crash switch. The manual walks you through the physical mount in about three pages. The real time sink is getting the power feed, the on/off switch, the external antenna, and the breakup sensor wired correctly while passing a pre-buy or annual inspection without a bunch of open questions. I have installed roughly two dozen of these across different airframes. The ones that gave me trouble were never the unit itself. They were the installer who ignored the antenna isolation requirements or routed the coax right next to the aircraft bus.

Artex Elt 110 4 Installation Manual Notes

The manual covers the basics. Mounting bracket, four #8 screws into a flat aluminum surface, torque to 70 to 90 inch-pounds. External 50 ohm antenna, minimum 3 feet from the transceiver body, minimum 6 inches from any other VHF antenna. Power comes off a dedicated 5 amp breaker, battery is an 8-year replaceable lithium cell, and there is a built-in hourly test feature that runs for about 2 seconds if you cycle the master switch. That part is straightforward. What the manual does not scream at you hard enough is that the ELT 110-4 has a remote ON/OFF switch that must be installed in the flight compartment if you want it operational in a meaningful way. Some installers skip this and just wire it to always be on, which works mechanically but fails a lot of inspection checklists and is a regulatory gray area depending on your country's CAA or FAA inspector. I recommend the remote switch every time. It is a $15 part and five minutes of running a small gauge wire through the console. I remember one build on a 1978 Cub where the co-phaser box for the whip antenna was mounted directly behind the instrument panel, and the ELT coax had to cross the avionics bus return path. During initial ground testing the ELT pulled about 2.5 amps on test mode and tripped the 5-amp breaker intermittently. Turns out the coax shield was grounded at both ends due to the mounting bracket, creating a ground loop through the battery negative. I broke the ground at the ELT housing with a fiber washer, ran the shield ground only at the antenna, and the problem disappeared. The manual mentions grounding but does not give you a clear diagram for multi-point antenna installations in metal tube airframes like that. The other thing nobody warns about is the 406 MHz beacon registration. When the ELT 110-4 transmits, it sends a GPS-positioned distress signal with a unique hex ID. If you have not registered that ID with your national authority before installation, the whole system is essentially invisible to rescue coordination centers until someone manually looks it up and ties it to a tail number. I once flew onto a ramp where the previous owner had installed a used 110-4 with a generic factory-registered ID. The beacon was active on the 406 band but was pointing to a location in France and listed a different aircraft type. Took about 20 minutes to re-register through the Cospas-Sarsat database and update the aircraft records. Always verify the registered hex ID against the physical unit serial number before you close the panel.

Practical Installation Steps

Pick a flat spot on the aircraft structure, preferably near the battery but away from high-vibration areas. Drill four holes, tap if needed, and bolt the bracket down with nylon locknuts. Apply a thin coat of dielectric grease to the connector pins before mating them. The waterproof seals on the ELT 110-4 connectors are decent but they rely on clean pin-to-sleeve contact, and oxidation causes intermittent failures that take days to track down. Run the power wire from the dedicated 5-amp breaker to the ELT power terminal. Use at least 16 gauge, ideally 18, and keep it away from the starter solenoid and alternator field wires. Install the remote switch in a location the pilot can reach without removing a hand from the yoke or throttle. Label the switch clearly as ELT TEST/ON/OFF so that during an inspection the mechanic knows exactly what it is. Mount the external 50 ohm antenna. Follow the 3-foot separation rule from the transceiver and the 6-inch rule from other VHF antennas. If you are using a co-axial whip in a high-speed aircraft, verify the antenna's maximum speed rating. The standard Artex whip is good to about 180 knots indicated. Going faster and you will get vibration damage or seal failure around the mount. Connect the breakup sensor if your airframe has one. The sensor is a small pull-wire assembly that triggers the ELT into emergency transmit mode if the aircraft breaks apart. Route the wire through a reinforced strain relief point and tension it according to the manual, usually about 1.5 to 2 pounds of pull. Too loose and a hard landing triggers it. Too tight and it pulls free during normal turbulence. This is the kind of detail where the manual is accurate but vague, and your best guide is a previous installation on a similar aircraft.

Common Pitfalls to Avoid

Using a non-50 ohm antenna. The ELT 110-4 expects a 50 ohm load. If you use a CB or marine antenna that presents a different impedance, the unit may still transmit but the power output drops significantly and the distress signal may not reach the 406 MHz satellite network at full strength. I have seen this happen with someone who tried to save money on a used antenna. The ELT lit up on the bench test, looked fine, and then the SAR aircraft overflight found a weak signal that was borderline undetectable at range. Always use an Artex-approved antenna or one listed in the manual as compatible. Running the ELT test too long. The manual says test mode is 2 seconds. Some installers hold it longer to check for a strong RF output or to listen to the squelch tone. Do not do this. Holding the test button beyond the designed duration can cause the lithium battery to heat and degrade prematurely. The battery life is rated at 8 years from manufacture date, not from installation date, and the test feature is meant to verify the circuit, not to measure output power. Ignoring the GPS position update. The 110-4 has a built-in GPS that sends your position during a 406 MHz alert. If the GPS antenna is blocked or poorly placed, the unit will still transmit but without positional data. Rescue aircraft will receive the beacon but will not know where you are. Mount the GPS patch antenna with a clear view of the sky, preferably on the top of the fuselage, and verify the position update during installation by pressing the test button and watching for a GPS lock indicator if your unit has one. Most 110-4 units do not have a visible indicator, so the only way to verify is with a spectrum analyzer or by checking the signal quality on a 406 monitoring receiver.

When the Manual Falls Short

The Artex ELT 110-4 Installation Manual is accurate but assumes you are working in a controlled environment with good reference materials. It does not cover every edge case in a 40-year-old bush plane with a corroded ground bus. If your aircraft has unusual grounding issues or you are doing a conversion from an older 121.5 MHz-only ELT, you may need additional diagrams from Artex's technical support. Their service bulletins occasionally update the wiring recommendations, especially around antenna placement and ground loop prevention. Check the Artex website for the latest service information before you start cutting panels. If you are installing this in a composite aircraft, note that the standard metal bracket mount will not work the same way. You need to use a grounding pad or a dedicated bonding strap to ensure the ELT chassis is properly grounded to the aircraft structure. Composite does not conduct electricity, so the ground path has to be explicitly created. I learned this the hard way on a homebuilt kit plane where the ELT was mounted on a fiberglass bulkhead. The first test showed normal current draw, but after a few flights the ELT went into fault mode because the ground connection had migrated due to vibration. Adding a bonding strap fixed it permanently. For the actual manual, search for "Artex ELT 110-4 installation manual" on the Artex website or through the FAA's database of approved aircraft documentation. The PDF is usually available for free and includes the wiring diagrams, torque specs, and antenna specifications you need. Make sure you have the revision that matches your unit's serial number, because Artex has issued a few updates over the years to the mounting and grounding sections.