When activated, an emergency locator transmitter (ELT) transmits on which frequency?

• A. 121.5 MHz
• B. 406 MHz
• C. 243 MHz
• D. 1090 MHz

Answer: (B)

The key idea is how modern emergency beacons are located. ELTs now transmit on 406 MHz as part of the COSPAS-SARSAT satellite system. That frequency is designed for satellite detection and delivery of the beacon’s identity (and, if equipped, GPS coordinates) to rescue authorities, so responders can pinpoint the aircraft quickly. The older 121.5 MHz signal exists as a homing aid for ground teams once a rough location is known, but satellites do not use it to locate a beacon. The other frequencies listed aren’t used for ELTs: 243 MHz is a military distress band, and 1090 MHz is used for surveillance-related transponder signals, not for ELTs. So, 406 MHz is the modern, globally coordinated frequency for ELT transmissions.