When are non-rechargeable batteries of an emergency locator transmitter (ELT) required to be replaced?

Non-rechargeable batteries of an emergency locator transmitter (ELT) are required to be replaced when 50% of the useful life expires. This guideline ensures that the ELT is always operational and ready for use in an emergency situation. By replacing the battery at this point, it helps to avoid the risks associated with a dead or weak battery when it is needed the most.

The useful life of the battery is an essential factor in maintaining the readiness of the ELT. By adhering to the 50% rule, operators can ensure that they have followed recommended practices for safety equipment, which is crucial in aviation where reliable emergency signaling can save lives.

While some alternatives may seem reasonable, like checking a battery indicator or setting a specific date for replacement, they do not guarantee that the battery is still within its effective operational capability. Monitoring the useful life percentage provides a more precise method for ensuring functionality when an ELT is needed.