FAR 91.207 Emergency Locator Transmitter: Inspection and Battery Rules

FAR 91.207 requires most U.S.-registered civil airplanes to carry an operable automatic-type emergency locator transmitter, mounted as far aft as practicable, inspected every 12 calendar months, with batteries replaced on defined triggers and each action recorded in the aircraft’s maintenance log. A handful of operations are exempt, and a few situations let you fly briefly without one, but outside those carve-outs a missing, expired, or undocumented ELT makes the airplane unairworthy.¹

Which Airplanes Need an ELT and Where It Goes

If you operate a U.S.-registered civil airplane, the default is that an automatic ELT must be attached and working before every flight. The transmitter has to be approved under one of the applicable Technical Standard Orders: TSO-C91, TSO-C126, TSO-C126a, or TSO-C126b.¹

Placement matters. The unit must be mounted as far toward the tail as practicable and secured firmly enough to survive crash forces without breaking loose. The tail section tends to hold together better than the nose or wings, which gives the transmitter its best chance of staying intact and broadcasting after an impact.¹

The 12-Month Inspection

Every ELT must be inspected within 12 calendar months of the previous inspection. Most owners fold this into the annual so the dates stay aligned. Four items get checked:

Proper installation, meaning the unit is secured and positioned aft as required.
Battery corrosion, since corroded contacts can keep the transmitter from firing.
Controls and the crash sensor, so the internal G-switch will actually trigger.
Antenna signal strength, confirming the transmission can reach a satellite or ground station.

All four are required by the regulation and belong in the maintenance record. A weak or obstructed signal means repairs or an antenna replacement before the airplane returns to service.¹

Battery Replacement Triggers and Logbook Entries

The rule sets two triggers for replacing or recharging the ELT battery, whichever hits first:

The transmitter has been in use for more than one cumulative hour, counting test time.
Fifty percent of the battery’s useful life, as set by the manufacturer, has expired.

Both apply whether the transmitter was activated on purpose or by accident.¹

When the battery is replaced or recharged, the new expiration date has to be legibly marked on the outside of the transmitter and entered in the aircraft’s permanent maintenance record. Skipping either step can make the airplane unairworthy on paper even when the hardware is fine. Mechanics see this often at annual: the battery got changed, but nobody updated the label on the unit or the logbook.¹

When You Can Legally Fly Without an ELT

Paragraph (f) of the rule lists operations that simply don’t need an ELT installed:

Training flights conducted entirely within a 50-nautical-mile radius of the departure airport.
Agricultural operations, such as aerial application of chemicals.
Scheduled flights by scheduled air carriers.
Aircraft in design and testing, manufacturer-authorized pilot training, or delivery of new aircraft.
Ferrying an airplane to a location where the ELT will be installed.

These carve-outs cover flights that either stay near a known location or involve aircraft that haven’t reached the equipment-installation stage yet.¹

Removing the ELT for Repair

You can keep flying with the ELT out of the airplane if it was removed for inspection, repair, modification, or replacement, but two things have to happen. First, the maintenance record has to show the date of removal, the transmitter’s make, model, serial number, and the reason it was taken out. Second, a placard reading “ELT not installed” must be in view of the pilot.¹

Ferry Flights With an Inoperative ELT

Paragraph (e) covers two ferry situations: moving a newly acquired airplane to where an ELT will be installed, and ferrying an airplane with an inoperative ELT from a place where repairs aren’t available to one where they are. Only required crewmembers may be aboard on those flights. Passengers are not permitted. A special flight permit under 14 CFR 21.197 and 21.199 is a separate option for reaching a repair facility, and those permits run for a maximum of 90 days.¹

Testing Without Triggering a Rescue

Testing procedure depends on the frequency. For a 121.5 MHz transmitter, operational tests are permitted only during the first five minutes after any hour, and they must not last longer than three audible sweeps of the tone. Flip the switch to test, listen on a COM radio tuned to 121.5 MHz for the downward-sweeping tone, then return the switch to armed. If a test outside the five-minute window is unavoidable, coordinate first with the nearest FAA control tower or Flight Service Station.²

For a 406 MHz ELT, follow the manufacturer’s instructions. These units generally include a built-in self-test. A live 406 MHz transmission can trigger a satellite alert and a rescue response, so do not activate the full transmit mode during a routine check unless the manufacturer’s procedure specifically calls for it.

Inadvertent Activations

False activations happen after hard landings, in turbulence, and during maintenance handling. If you suspect the ELT has gone off, switch it off and monitor 121.5 MHz to confirm. If it was transmitting, contact the nearest Air Traffic Control facility right away to report the false alarm.³

You can also call the Air Force Rescue Coordination Center directly at 1-800-851-3051 to cancel the alert. For a 406 MHz beacon, have the hex ID ready when you call, since that is how a specific alert is tracked. After any inadvertent activation, the unit may need maintenance before being returned to the armed position.³

121.5 MHz vs. 406 MHz

The regulation still lets a TSO-C91 or TSO-C91a 121.5 MHz unit satisfy the equipment requirement, but the practical picture changed in February 2009, when the COSPAS-SARSAT satellite network stopped processing distress signals from 121.5 MHz ELTs. An aircraft carrying only a legacy 121.5 MHz transmitter will not be detected by satellite after a crash; detection depends on another aircraft or a ground station happening to hear the signal on guard.⁴

A 406 MHz ELT approved under TSO-C126 or its revisions transmits a 5-watt digital signal that satellites can detect and locate with much better accuracy, and each beacon broadcasts a unique digital code tied to its registered owner so rescue coordinators can verify an alert before launching resources.⁴

If you install a 406 MHz ELT, FCC rules require you to register the beacon with NOAA before use. Registration links the beacon’s hex code to your contact information, aircraft identification, and an emergency point of contact through NOAA’s SARSAT program. Keep the record current after a sale or a change in phone number.⁵

A Note on Extended Overwater Operations

FAR 91.207 is the general rule for airplanes. Part 121 operators flying extended overwater routes have an additional obligation under 14 CFR 121.339: an approved survival-type ELT, easily accessible for a water landing without preparatory procedures, installed in a conspicuously marked, approved location. The same battery triggers apply, with one exception for water-activated batteries, which are essentially unaffected during storage and do not follow the standard shelf-life calculation.⁶

1
eCFR. 14 CFR 91.207 – Emergency Locator Transmitters
2
FAASafety.gov. Radio Communications Phraseology and Techniques – P-8740-47
3
Federal Aviation Administration. Aeronautical Information Manual – Emergency Services Available to Pilots
4
Federal Aviation Administration. Termination of Satellite Monitoring of 121.5 MHz ELTs
5
NOAA Search and Rescue Satellite Aided Tracking. United States 406 MHz Beacon Registration
6
eCFR. 14 CFR 121.339 – Emergency Equipment for Extended Over-Water Operations