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    Thursday
    Jan202011

    Life Raft Emergency Locator Transmitters

    There is also an ELT in the life raft so when after a ditching, when your aircraft has sunk, and you are bobbing about in your life raft, you can be assured that someone will be able to find you.  Most of the ELTs installed on the life rafts are automatic – they start to transmit immediately when the life raft hits the water.  In the Winslow Life Raft described on this site, it is the SRB-406 Emergency Locator Transmitter.  It is installed to provide satellite-based position locating during search and rescue operations.  The ELT begins to transmit immediately upon deployment via a water-activated sensor built into the life raft. In case of ditching in an environment other than water, there is a manual lanyard activation feature.  Here it is when detached from the life raft.   

     The ELT transmits on 3 frequencies at the same time. The first and most important frequency is 406 Mhz, which will be picked up by satellites to pin point your position.  It transmits on this frequency for 24 hours.  It also transmits on 121.5 Mhz and 243 Mhz – these frequencies are used by search aircraft to narrow down your position so they can rescue you.  It transmits on these frequencies for 50 hours.

    If you want even more detail, here is the brochure information:

    Transmitter Duty Cycle: 5 watt digital signal every 50 seconds, for 440 MS duration, Homing Signal Tone Frequency: 700 Hz Sweep between 1600 and 300 Hz, Homing SignalTone Sweeping Rate: 2 to 4 times per second, Operating Temperature Range: -20°C to 55°C (-4°F to 131°F), Homing Signal Operating Range: 100-280 miles (160-450 km), subject to atmospheric conditions, receiver altitude, and sensitivity, Battery Operating Life: 50 hours (homing), Battery Operting Life: 24 hours (406 MHz), Battery Service Life: 5.0 years, Frequency: 121.5 MHz, 243.0 MHz, 406.028 MHz.

    This next photo gives you some idea of its size, compared to the human hand.