Aviation From My Rocking Chair: Let’s Talk About Our “Little Fren” the ELT

Hello once again, my friends. I was going to write this month about people I have met during my lifetime of airplanes and airplane people. That, however, got way too complicated so…y’all will just have to listen to another dry lecture from the rocking chair.

First, a little ELT history. In 1972, U.S. Representative Hale Boggs and Nick Begich were lost in an Alaskan air crash, and were never found. For this reason, in 1973 Congress required most G.A. aircraft to be equipped with Emergency Locator Transmitters (ELT) The first and second generation of which were analog and transmitted on 121.5 or 243.0 MHz.

ELTs were originally intended for use on 121.5 for alerting ATC and aircraft monitoring the frequency. In 1982 a satellite-based monitoring system (COSPAS-SARSAT) was started to provide a better way to detect distress signals. In 2009 the international (COSPAS-SARSAT) satellite system discontinued monitoring 121.5/243 MHz frequency, in part due to a high number of false signals attributed to them. Today, the only satellite monitoring is done by digital ELTs operating on 406 MHz.

Surprisingly, there is no requirement in the U.S to replace first and second generation (TSO-C91 and 91a) ELTs. There is a problem however. Since 2119, following an FCC final rule, the manufacture, importation, or sale of 121.5 ELTs is prohibited. Note: This Does Not ban the use of or repair of gen.1 or 2 ELTs as long as parts and new batteries are available. The yearly function test is still required. FAR 91.207 covers ELT requirements for battery replacement and installation/testing.

So, why upgrade to a new TSO-c126 operating on 406MHz? The main reasons I see are: 1) They activate 81-83 percent of the time in a crash, as opposed to 73 percent with the 121.5 systems. (2) Satellite based accuracy positions are within 1-3 NM with SAR search time of 4.5 hrs (avg) opposed to position accuracy for 121.5 ELTs of 12-15 NM, a SAR search area of 782 sq.mi., and 40.25 hr SAR average search time.

(3) May have Nav-Interface installed to link GPS for position information.

O.K, troopers. A couple more items to clean up, and I’ll let you go.

All ELTs must be tested once a year and an entry made in the log book. Only test a 406MHz unit for 30 seconds, and test a 121.5 unit the first 5 minutes after the hour for a maximum of 3 sweeps. Remember FAR 91.207 covers ELT requirements, and the Manufacturer recommendations cover installation and testing procedures.

I would like to thank all of you for the support I’ve received with this endeavor, and none more than Skip Brown. Without her, you probably wouldn’t recognize this chicken scratch. So…rest easy my friend. You deserve it.

Merry Christmas to everyone and we’ll see you at the Party!

Rick Vaux TC4130