Emergency Locator Transmitters
September 3, 2011 Leave a comment
INTRODUCTION: On get-togethers with a friends, we commonly ask the age-old question “what did you do today?” Bill Weiler usually keeps us entertained by relating the trials and tribulations of tracking down ELTs that have gone off. While the ELTs have saved thousands of lives, they just as frequently are set off inadvertently, leading crews of Civil Air Patrol or the Coast Guard on wild goose chases. I plan to corral guest bloggers familiar in the art of ELT tracking for future posts. But to start this category, I asked Bill to give us a definition and explanation of what an ELT is and how it works.
BILL WEILER, Captain Civil Air Patrol, ON THE ELT:
Whether you’re lost in the woods, aboard a sinking ship, or forced to make an off-airport landing or crash in an aircraft, there are technological tools that can let someone know you’re in distress, and help the SAR team (Search And Rescue) find you. Hikers can carry a PLB (Personal Locator Beacon), most boats going off-shore carry an EPIRB (Emergency Position-Indicating Radio Beacon), and aircraft are equipped with an ELT (Emergency Locator Transmitter).
While the size, shape, and activation of each beacon may be different, they all transmit a distinctive siren/whoop tone on the international distress frequency, 121.5 Mhz. PLBs are manually activated by the user, EPIRBs can be either manually activated or may be equipped with automatic activation systems if they go underwater, and all ELTs have both manual activation and an automatic activation system when it senses the G forces of a sudden stop or exceptionally hard landing. All of the newer radio beacons also transmit a digital signal on 406Mhz that is continuously monitored by satellites which can help locate the signal quickly, and identify the registered owner of the device.
ELTs became mandatory on most aircraft in 1973, following the crash of a plane in Alaska carrying House Majority Leader, Hale Boggs, and another Representative, and the wreckage and bodies have never been found. In 1982, the first satellites were launched to help track emergency radio beacons as an international effort called COSPAS/SARSAT which included the US, Soviet Union, Canada, and France. The system has been credited with saving over 28,000 lives since its inception.
Listen to the distinctive sounds heard by rescuers tracking down an ELT.
Bill Weiler, Capt CAP
Florida Wing Civil Air Patrol