Avionics News May 2018 - 24

ARTEX introduced the world's only 406
MHZ approved transport-grade alkaline
battery-powered ELT during the
2018 AEA International
Convention & Trade
Show in Las Vegas.

121.5 MHZ ELTS

Continued from page 23

scene. False alarms were rampant with the old ELTs, with
most originating from non-ELT transmitters. The ELT's
inertial switches are similarly unreliable.
406 MHz
The first and most-important benefit of using the 406 MHz
ELT flies overhead every few minutes: satellites. The second:
the ability to transmit GPS coordinates to guide searchers.
SAR launches on first alert, saving an average of six hours
for inland accidents. Hourly satellite passes help improve the
accuracy of the original fix. Alerting is nearly instantaneous.
On first alert, searchers have a defined area of 25
square nautical miles. Doppler shift analysis reduces the
search area to between 1 and 3 square nautical miles -
without a GPS input.
With GPS, that search area quickly drops to 100 square
yards. Faster location should mean quicker rescues.
False alarms also drop with 406 MHz ELTs. Since the
406 MHz ELT broadcasts a digital signal, it can include
coded data identifying the owner of the ELT; phone calls
to the owners resolve most false alarms. Today's best
406 MHz ELTs also broadcast on 121.5 to aid ground
searchers the last few yards to their target.
Battery replacement cycles and batteries themselves are
typically less expensive for these new ELTs. Newer 406
MHz ELTs come with battery-replacement cycles ranging
from five to 12 years, with overall lower life cycle costs.
24

avionics news

may

2018

Better, but problems persist
The end of authority to install new 121.5 MHz ELTs in
aircraft helped nudge the changeover forward, if for no
other reason than for new aircraft to meet Federal Aviation
Regulation 91.207, the only options available are all 406
MHz units.
Thankfully, for the existing fleet, lower prices, better
features and reduced maintenance needs and costs helped
move many owners to upgrade - even lacking a mandate
to do so.
Despite some solid saves with 406 MHz ELTs, however,
some of the problems of the preceding technology
continue to occur. Failure to trigger in a crash; failure of
a triggered ELT to broadcast; failure of mounts. These
problems largely trace back to errors in installation.
Former Sen. Ted Stevens, 86, was the longest-serving
Republican senator in history when he retired in 2009 and
was one of nine souls aboard a 1957 DeHavilland DHC3 Otter when it crashed into a brush- and rock-covered
mountainside on Aug. 10, 2010.
The crash site, about 17 miles north of the southwest
Alaska fishing town of Dillingham, was not quickly
located because the 406 MHz ELT mount was improperly
installed and failed in the crash.
In departing its mounting point in the crash, the ELT
body separated from the coaxial cable connecting it to
its antenna. Despite the unit trigger functioning properly,
the lack of antenna integrity prevented the signal from
reaching the satellites.
406 MHz ELTs:
Options abound at various price points
Since a pilot or aircraft owner can't buy a new 121.5
MHz ELT anymore, the only options for a new ELT is a
406 MHz model.
Three basic versions exist out of many, many models:
406 MHz ELTs with an integral GPS engine to supply
precision position info; 406 MHz models capable of
being fed GPS position data by an external navigator;
and 406 MHz models with no GPS option.
And yes, even those uninformed ELTs deliver better
performance and greater accuracy than the old 121.5
MHz models. Remote triggering/activation and an
activation enunciator remain standards required by the
regulations. q

Table of Contents for the Digital Edition of Avionics News May 2018