ELT detection and battery life: 406 MHz vs 121.5 MHz
ELT detection (SAR 3.5, SAR 3.1, SAR 3.4):
| 406 MHz | 121.5 MHz | |
|---|---|---|
| Satellite detection | Yes: geostationary within minutes of activation (unobstructed signal); polar-orbiting within 90 min | None since COSPAS-SARSAT stopped monitoring on February 1, 2009 |
| Detected by | Satellite | ATS facility in range, or passing aircraft relaying (sometimes military or commercial traffic monitoring 121.5 or 243 MHz) |
- 406 MHz position: either satellite type gives a position.
- 406 MHz identity: tied to a unique user; rapid ID, false alarm may take only a few phone calls (SAR 3.1).
- 121.5 MHz useful once SAR already works the area: short-range location by siren-like tone on any tuned receiver.
Battery life (SAR 3.1):
- Properly maintained ELT with serviceable batteries: runs continuously for minimum 24 hr.
- Expired batteries: not serviceable, whatever else checks out.
Trap: 24 hr is minimum continuous run time, not detection time or test duration.
References
- TC AIM SAR 3.1
- TC AIM SAR 3.4
- TC AIM SAR 3.5