Communication, Navigation, Position and Warning Practice Test

The main idea is that ELT batteries have a limited life that depends on time and actual use, so they must be replaced before they can fail to perform in an emergency. The best rule is to replace when any of these thresholds are reached: after more than one cumulative hour of operation, when half of the battery’s usable life has been used (about 50%), or at the stated expiration date. This ensures the transmitter can deliver reliable power when needed, since both aging and usage wear down the battery. Testing the unit doesn’t by itself mandate replacement, and never replacing the battery would risk an inoperative ELT.