The Australian Transport Safety Board has release an investigation report into the effectiveness of electronic location transmitters (ELT) in aircraft crashes.
ELTs are usually fixed in place on an aircraft and are triggered automatically by either a g-force switch or a water-activation switch. They have not been mandatory on light aircraft since 1997, when CASA approved EPIRBs and PLBs as an acceptable alternative.
The ATSB conducted the report because the effectiveness of fixed ELTs has been brought into question by the aviation industry. Examining accidents from 1983 to 2012 in which an ELT could have been expected to activate, the report showed that they were effective in only 40-60% of cases.
Regardless, ELTs have been credited with saving 52 lives over that period. Reasons for ELTs failing to activate included:
- Pilot not arming the ELT before the crash
- Incorrect installation
- Flat batteries
- Lack of water proofing
- Lack of fire protection
- Disconnection from the antenna during the crash
- Damage or loss of the antenna during the crash
- Aircraft coming to rest inverted after impact.
The full ATSB report can be downloaded from the ATSB website here.