Emergency Locator Transmitters (ELTs): What They Are and How They Are Maintained

An Emergency Locator Transmitter (ELT) is a distress beacon carried on an aircraft that transmits a locating signal after an accident so search and rescue teams can find the site. It is a standalone, battery-powered unit with its own antenna, and it is maintained as a line-replaceable item: the operator keeps the battery, mounting, and antenna serviceable, tests the unit at defined intervals, and sends it to an approved repair station for battery replacement, repair, or overhaul. Turner Aviation, an avionics and spares specialist holding CAA, EASA, FAA, and ISO 9001 approvals, lists ELTs among its core support lines alongside aircraft generators and flight deck printers, offering Standard, Priority, and AOG service to a global customer base.

What an ELT does and when it activates

The ELT's job is narrow and specific: after a crash, it broadcasts a signal on the 406 MHz distress frequency (and, on many units, a lower-power 121.5 MHz homing signal) so the international satellite-based search and rescue system can alert a rescue coordination centre and narrow the search area. Some units also transmit a GNSS-derived position, which shortens the search considerably.

Activation happens in three ways:

• Automatic (G-switch): a built-in acceleration switch senses the impact forces of a crash and fires the transmitter without crew action.
• Manual: a cockpit remote switch or a switch on the unit itself lets the crew activate it deliberately.
• Water activation: on some survival and portable units, contact with water completes the circuit.

The unit is designed to keep transmitting for a defined period after activation, which is why battery condition is the single most important maintenance variable.

The main ELT types

The distinction matters for maintenance because AF and AP units are tied to the aircraft's airworthiness programme, while survival units are usually managed as equipment with their own battery and inspection schedule.

Key components

• Transmitter and battery pack: the beacon itself and its primary power source. The battery is a controlled-life item with a printed expiry date.
• Antenna and coaxial cable: must be correctly matched and undamaged; a poor antenna or a broken coax run is a common reason a beacon transmits weakly or not at all.
• Mounting tray and hardware: holds the unit rigidly so the G-switch sees the intended crash forces and so the unit does not become a projectile.
• Remote switch and harness (where fitted): the cockpit control that arms, tests, and manually activates the beacon.
• ELT itself as an LRU: in most installations the beacon can be removed and replaced without major structural work, which is what makes bench repair and exchange practical.

Regulatory requirements and testing intervals

ELT carriage, installation, and inspection requirements are set by the applicable airworthiness authority and the aircraft's operating rules — for example, the FAA in the United States, EASA in Europe, and the CAA in the UK. Turner Aviation holds approvals from the CAA, EASA, and FAA, which is relevant when a unit needs work that must be released under a specific authority's approval.

Because the exact intervals depend on your aircraft's approved maintenance programme and the ELT manufacturer's instructions, treat the following as the categories of work rather than fixed numbers:

• Scheduled inspection: physical check of the unit, mounting, antenna, cabling, and connectors, plus a functional/self-test as permitted by the manufacturer.
• Battery replacement: driven by the battery's expiry date or by cumulative transmission time, whichever the manufacturer specifies. This is the most common reason an ELT comes off the aircraft.
• Recurring functional test: a short self-test or bench check to confirm the transmitter and its indicators work. Never perform a live 406 MHz transmission as a routine test — use the manufacturer's self-test mode.
• After any activation: any inadvertent or genuine activation should trigger an inspection and, where required, a battery assessment.

Always confirm the current requirement against your aircraft's maintenance programme and the ELT manufacturer's component maintenance manual; the intervals are not universal.

Common failures and troubleshooting

• Expired or depleted battery. The unit may pass a self-test but have insufficient capacity for a full transmission. Check the expiry label and the maintenance record first.
• False alarms. Accidental activation from a hard landing, handling, or a mis-set remote switch. These consume battery life and generate unnecessary rescue response; the unit should be inspected and the event recorded.
• Antenna or coax faults. Corrosion, water ingress, chafed cable, or a damaged connector. Symptoms include failed self-tests or low transmitted power on a bench check.
• Mounting and tray issues. A loose tray or missing hardware can prevent correct G-switch operation and is an airworthiness concern in its own right.
• Remote switch and wiring faults. The cockpit switch may fail to arm or activate the beacon even though the beacon itself is serviceable.
• Water ingress into the beacon. Particularly relevant for units exposed to the elements or to ditching scenarios.

A practical troubleshooting order is: confirm battery status, run the manufacturer's self-test, inspect antenna and coax, check the mounting and remote switch circuit, and only then remove the unit for bench testing.

Repair, overhaul, and AOG support

ELT work generally falls into three service levels:

1. Line maintenance — inspection, self-test, battery replacement, and unit swap at the operator's facility.
2. Bench repair and overhaul — carried out by an approved repair station under the relevant authority approval, with the unit returned to service with the correct release documentation.
3. AOG (aircraft on ground) support — expedited turnaround or exchange when an aircraft is grounded by an unserviceable ELT.

Turner Aviation states that it supports ELTs for a global customer base with Standard, Priority, and AOG services, and holds industry approvals including Dukane Seacom (an ELT manufacturer) alongside AstroNova, Collins, Honeywell, Safran Electrical Power, and Skurka Aerospace. For an operator, the practical selection criteria when choosing a support provider are:

• Approvals that match your aircraft's registry — a repair released under an approval your authority does not recognise creates a paperwork problem.
• Battery and parts availability — the turnaround time is usually governed by whether the correct battery pack is in stock.
• AOG capability — whether the provider can ship or exchange outside normal hours.
• Traceability — authorised distributor status for OEM spares and overhaul kits, which Turner Aviation states it holds.

Turner Aviation's stated operating approach is built around low turnaround times and minimising operating cost by maximising time on wing, which is the relevant promise to test against your own dispatch reliability requirements. Note that the company was acquired by Precision Aviation Group in July 2025, with VSE Corporation completing its acquisition of PAG in May 2026, so group-level MRO capacity may be relevant if you need support across regions.

What to do next

If you operate an aircraft with an ELT, the actionable checklist is: verify the battery expiry date and remaining capacity margin, confirm the unit and antenna pass the manufacturer's self-test, inspect the mounting and coax at each scheduled check, and identify in advance which approved repair station you will use for battery replacement and overhaul. For operators who want a single source across ELTs, generators, and avionics, Turner Aviation's sales team can be contacted directly for service options and turnaround.