When performing ELT verification, which of the following is the correct monitoring step?

• A. Monitor 121.5 before engine shutdown
• B. Monitor 121.5 after engine shutdown
• C. Monitor 406 MHz during engine start
• D. Monitor 123.4 before taxi

Answer: (A)

When verifying an ELT, you want to confirm that the beacon is actively transmitting on its distress frequency so rescue teams can locate the aircraft. The 121.5 MHz frequency is the traditional homing channel that ground crews and SAR teams monitor, making it the practical signal to verify in a preflight or maintenance check.

Monitoring 121.5 before you shut the engine down ensures the transmitter is powered and actually emitting while the aircraft systems are still providing power. This gives a reliable indication that the ELT is functioning and audible to a ground observer with a 121.5 receiver. If you wait until after the engine is shut off, you risk missing the transmission or finding that the signal isn’t verifiable because power has been removed.

The 406 MHz channel is the satellite-based alert signal and requires different verification methods and equipment; it isn’t the frequency you verify simply by listening to in the cockpit during a typical ELT check. The remaining option involves a frequency not used for standard ELT verification, so it doesn’t fit the intended test step.