Emergency Locator Transmitters

Section 91.207 — Emergency locator transmitters (ELTs) — establishes the requirement for ELTs in most U.S.-registered civil aircraft, and the inspection/battery rules.

Paragraph (a) — Required: ELT must be installed in most U.S.-registered civil airplanes. Specific exceptions in paragraph (e) include training aircraft within 50 NM of base, aircraft on agricultural operations, design test flights, etc.

Paragraph (b) — ELT inspection: The ELT must be inspected within 12 calendar months for proper installation, battery condition, transmitter operation, and signal strength. The inspection date is recorded in the aircraft logbook.

Paragraph (c) — Battery replacement: ELT batteries (or battery packs) must be replaced (or recharged if rechargeable):

• After 1 hour of CUMULATIVE use; OR
• When 50% of their useful life has expired (manufacturer's published useful life).

121.5 MHz vs 406 MHz: The legacy 121.5 MHz ELT is still legal for installation in most aircraft, but it's no longer monitored by satellite (since February 2009). The 406 MHz ELT is satellite-monitored, transmits aircraft identification, and provides much faster search-and-rescue response. Most operators have upgraded to 406 MHz.

ELT test transmissions: Pilots may transmit on 121.5 for ELT testing during the first 5 minutes of each hour. Use of 406 MHz for any transmission triggers a real satellite alert and may dispatch SAR — do not test 406 MHz without proper coordination.

Reference: AC 91-44A on ELT performance.

ELT Inspection + Battery Math — § 91.207 Decoded

Many pilots will say "the ELT gets inspected every 12 months." That is close enough to be dangerous. The reg uses calendar months, not rolling months, and it has a second clock running on the battery that is completely independent of the airframe inspection. Missing either one renders the aircraft un-airworthy — even if the ELT itself is bolted in and beeping.

Here is what § 91.207 actually requires, in the order it actually matters:

One more point the mnemonics skip: 406 MHz vs 121.5 MHz. The legacy 121.5 MHz ELT is still legal under § 91.207 — the FAA never banned it for domestic flight. What changed is that Cospas-Sarsat stopped satellite-monitoring 121.5 MHz on February 1, 2009. An aircraft that still has a 121.5 unit and crashes off-airport can be heard only by another aircraft tuned to guard. A 406 MHz ELT gets a satellite hit, the aircraft's registration, and (if registered with NOAA) the owner's name and emergency contact — usually within minutes. The reg does not force the upgrade. Survivability does.

What an Examiner Asks About § 91.207

ELT questions show up on every checkride, and they are easy points for an applicant who understands the two-clock structure. Examiners are not looking for a recitation of the reg — they are looking for whether the applicant knows which clock is which.

• "When does the ELT inspection expire?" Every 12 calendar months from the last inspection. If it was inspected on May 14, 2026, the next inspection is due no later than May 31, 2027 — the last day of the 12th calendar month. Not May 14. Calendar-month math provides a small grace and should not be confused with the rolling-month math used for a flight review.
• "When must the battery be replaced?" Two triggers, whichever comes first: more than 1 cumulative hour of transmitter use, or 50% of useful life expired. The 1-hour clock is why an inadvertent ELT activation on a long ferry flight is a logbook entry, not something to ignore.
• "What gets logged in the maintenance record?" The 12-calendar-month inspection, and the new battery expiration date when a battery is replaced. Both are required by § 91.207(c) and (d). The battery date also has to be marked on the outside of the transmitter itself.
• "121.5 vs 406 — does it matter for compliance?" For § 91.207, no — both satisfy the carriage requirement. For getting found, yes. 121.5 MHz lost satellite monitoring in February 2009. 406 MHz is the operational standard.

The point the DPE is hunting for: an applicant who says "ELT inspection every 12 months" and stops. The complete answer is 12 calendar months, with a separate clock on the battery. Two requirements. Two log entries.

Pre-Flight Check of the ELT, Under § 91.207

Consider a typical preflight on a Cessna 172, filed VFR. Opening the rear baggage door reveals the ELT — the orange box bolted as far aft as practicable, exactly where § 91.207(b) requires it. The following discipline is often skipped.

Switch position. Confirm it is set to ARM, not OFF. An ELT in the OFF position is inert. If the airplane just came out of maintenance, that is when it is most likely to be set wrong.

The battery placard. There is a label on the transmitter with a battery expiration date. If the current date is past that date — even by one day — the aircraft is not airworthy. § 91.207(c) does not provide a grace period regardless of a plan to swap it later.

The 12-calendar-month inspection. That record is in the airframe maintenance log, not on the ELT itself. The correct way to answer "when was the ELT last inspected?" is to know, because the record has been checked. Many pilots do not, assuming the shop is on top of it — and then face a ramp check or a failed CFI initial.

The cockpit check. Tune the comm to 121.5 in the first five minutes of the hour (the only window the FCC allows for ELT testing). Nothing should be heard. A continuous warble means the unit is firing — which usually means it bumped on during the last landing. Cycling it OFF then back to ARM and verifying silence resolves it.

CFI candidates lose points on this on every initial ride — not because they do not know the reg, which most can recite cold, but because they do not walk it on the actual preflight. A competent crew verifies both clocks: the inspection date in the logbook, and the battery date on the placard. One day overdue is still overdue, and a plan to handle it later is not a defense to a Letter of Investigation.