by Larry Anglisano
Without much encouragement, you can develop an itchy rash thinking about emergency locator transmitters or ELTs. The FAA requires these devices yet its common knowledge that theyre a pain in the keister to maintain and, in the end, they don’t work very well.
Most avionics shops are glad to defer required ELT inspection and maintenance chores to the mechanics during annual inspections. When Aviation Consumer last examined the topic of ELTs five years ago, we concluded that theyre like a bad insurance policy-annoying to pay for and often useless when needed.
Nonetheless, they at least provide some backstop protection in the event that you have to put your airplane down off airport in an emergency. As we recently learned after a surprise engine stoppage and a cornfield landing in a Cessna 210, search and rescue might take hours and the ELT might help. Eventually.
ELTs have improved over the years, especially with the advent of 406 MHz alerting, which is more effective than the old 121.5 MHz standard. If your ELT is getting long in the tooth, it may be time to consider a replacement.
Bad Rap
Old ELTs get negative publicity for obvious reasons. The ELTs that most seasoned pilots are acquainted with work on the 121.5/243 MHz frequency band. In the event of a crash, a sensor or G-switch triggers and broadcasts the familiar werping distress sweep tone that can be picked up by other aircraft and by satellite.
The ELT is independent of the aircraft electrical system and runs on its own power-either specialty cells or plain old alkaline batteries. Even with yearly inspections, its obvious that many airplanes are flying around with dead ELT batteries, in many cases because quite a few airplanes are flying around out of annual inspection.
And even if the batteries are good and the crash activates the signal, it might not be heard due to the antenna being shielded by the metal fuselage or by the big terrain and tree that you hit. If you crash hard, the ELT or its antenna might be destroyed. It has happened. What helps is that, per regulation, the unit must be installed in the tail section of the fuselage, the safest area of the airplane during a hard impact.
The low earth orbit SARSAT/COPSAS satellites listen for 121.5 MHz ELT hits but rely on Doppler calculations as they fly over to resolve position. It may take several satellite passes to get close, if the birds hear the ELT at all. Its a crude system, at best.
False alarms are a significant problem. Since an ELT can be activated by a hard landing, severe turbulence or sloppy maintenance handling, there are plenty of false hits. In fact, SARSAT reports that something like 95 percent of all signals are due to false activation.
Newer technology has improved this. The 406 MHz digital ELT system, in which the basic concept is digital messaging, reduces false hits and helps rescue teams arrive at crash sites quickly.
If GPS position is also streamed into the ELT, the job is even easier. The 406 MHz transmitter sends out a 5-watt signal for half a second, every 50 seconds, streaming the beacon serial number, manufacturer code and country code. Once decoded, the ground computer can obtain the owners name, address and type of aircraft. Instead of hastily launching rescue teams, a simple phone call can determine if there really was a crash and where it might be.
And the tight design specs of new 406 MHz beacons cut false activation by 95 percent, says NOAA. Since 406 MHz units are processed by geostationary satellites, not low-earth-orbit satellites, they hear the signal more quickly and cover a large portion of the earths surface.
ELTs: Past is Prologue
Our shop doesnt see many applications for installation of a new ELT. We suspect that maintenance shops get more involved than avionics facilities and thats fine with us. When its time to replace a old ELT, the most cost effective strategy may be to tap the overhaul/ exchange pool.
Since most ELTs work with a specified antenna, replacing a system can get costly for owners who are already skeptical of an ELTs benefits. In this case, a like unit that is newly certified with a fresh battery is the easiest way to go.
A popular source for quality overhauled units of all vintages is MERL Electronics in Meriden, Connecticut. (Contact 860-237-8811.) Theyre we’ll set up to comply with ELT inspection and overhaul regulations governing ELT return-to-service requirements. If the application is such that a new unit with installation is required, you should understand the following: Reliable 121.5/243.0 MHz ELT gear might be relatively short-lived. Were told than when 121.5 MHz-capable satellites reach the end of their service lives by about 2009, they wont be replaced and existing satellites wont be maintained. If this turns out to be true-and who can say for sure?-it will put an end to satellite detection of 121.5 MHz ELTs.
In short, without the help of satellite location, don’t get your hopes up for a speedy rescue if you fall from the sky. Even with the current satellites in service, response time isn’t quick.
Helen Woods of CAP tells us that since the RCC (Air Force Rescue Coordination Center) doesnt launch rescue missions until a second satellite passes to refine the accuracy of the first beacon hit, it might be too late for a successful rescue.
On the other hand, 406 MHz beacons don’t require a second look since theyre so accurate. This new technology has already saved many lives so we think if youre buying new, the 406 MHz models are worth considering, especially if cost isn’t an issue.
Installation
Physical installation of an ELT system is relatively straightforward since no connection to the aircraft electrical bus is required. The biggest part of the job is routing the cable through the interior to the remote switch. The remote switch adds its own challenge because finding empty space on the panel is easier said than done in many airplanes. Installation of the antenna on pressurized aircraft takes extra regulatory approval and time.
The shop should put the antenna in an area that is easy to access, as ELT antennas will need to be replaced at some point, usually due to corrosion but also because of wear and tear from flight. We recall a Piper Arrow that went through three antlers because it was mounted in an area hit hard by the slipstream. The antenna, part of the ACK E01, stressed and cracked in the same spot each time. Factory engineers finally suggested we put a slight bend in the antenna for improved aerodynamics and it solved the problem.
Products
Not much has changed in ELT offerings since our last review. We suspect this wont remain true once we get closer to the anticipated end of the 121.5 MHz satellites. The most popular units for GA aircraft are built to satisfy the FAAs TSO C91a specification, which assures a certain performance specification if not any guarantee theyll work when needed.
The ARTEX, Inc. ELT 110-406 406 MHz system is popular in newer aircraft and can be found in everything from Boeings to Beechcraft. Artex was the first to offer an approved satellite-based 406 MHz SARSAT system a few years back and still holds the market in this technology.
While the 406 model is far from cheap, its fancy, with versions available to connect up to onboard GPS and NMS systems to stream positional information. Expect to pay $3000 to install one of these systems and if the 121.5 MHz system goes away, you just might have to. A newer variant of this is the G406-4, which sells for $1750.
The lower cost ELT 110-4-a 121.5 MHz system-is the more popular offering for GA aircraft and is a reasonable choice for upgrade, at $550. Its durable from an installation standpoint, since it arms itself only when snapped into the mounting tray, helping to eliminate false hits when a ham-fisted mechanic drops it on the bench.
The Artex ELT200 sits on smaller footprint but has a less secure mounting scheme than the ELT 110-4, in our estimation. This unit is, however, one of the smallest ELTs around. Its light, too, making it a reasonable choice for weight challenged applications. Cost: $400.
Top of the 121.5 MHz line is the Artex ELS10, which has a voice broadcast of who crashed and where, instead of the basic and general sweep tone. With Artex seemingly the pioneer in 406 MHz technology, we expect them to lead the way in future product design and enhancements.
The AmeriKing AK-450 121.5 MHz ELT is another popular beacon that uses Duracell D-cells, making battery replacement easy during annuals. It also talks, transmitting voice communications on the 121.5/243.0 MHz frequencies. Its quite small measuring 4.27 X 2.95 X 5.0 and weighs a mere 2 pounds.
The remote controller module, however, is a bit big for tight panels and always gets in the way when we try to use every bit of panel real estate during big retrofits.
Still, at around $225, this system is a good value. Plus, it comes with an extra portable antenna for going mobile and interconnects are easy with standard modular cable. AmeriKing also makes a version designed for helicopters.
Like the AK-450, the very popular ACK E-01 was designed to make yearly maintenance easy, operating on eight Duracell D-Cell batteries and connecting with modular phone cable. They also provide a secondary portable antenna, appropriate for when you want to take the ELT walking through the woods after you free yourself from the wreckage.
The unit weighs about 3 pounds and uses the familiar antenna with cone shaped base. It has a list price of $375 and includes a panel-mounted control unit thats smaller than AmeriKings.
The beacon itself, however, is larger measuring 7.75 X 2.75 X 2.75. Our shop has installed more of this model than any other and weve had no complaints.
Pointer dates back to the early days of ELTs but has been improved over the years. Older 3000 units can be easily replaced with newer 3000 series beacons that meet RTCA DO-183 specs for ELTs. These sell for about $552. The small remote switch is a familiar face in some new airplanes and takes little panel space compared to others.
The 3000-10 model offers voice broadcast and all models use alkaline battery packs, not specialized ELT batteries.
We have to wonder if Narcos ELT sales-primarily the ELT10-kept the company going through turbulent times as their units are found in many airplanes.