Saturday, November 29, 2008

Installing the "here's where my remains are" machine

The ELT system in the United States is changing. Starting in February, the 121.5 frequency will no longer be monitored. Instead, satellites will monitor the 406 mHz frequency and a new generation of emergency locator transmitters has been created that encodes the aircraft's identity and also makes it possible for rescue people to pinpoint the signal's location to feet (or maybe yards) instead of miles.

I bought the Artex 406 mHZ ELT and paid about $900. Today I checked Aircraft Spruce and it's selling now for almost $2,000. Ridiculous. Van's sells them for $945. Technically I didn't have to go with the new ELT. I could've gone with the old-fashioned 121.5 system. And then it was a question of where to put it. Many RV airplane builders tuck it under the baggage floor, but to me, there's too great of a possibility the baggage area won't withstand a crash well and an ELT won't work. Also, many RVers who put there, run it to a whip antenna that goes on the backside of the rollbar. It might work, although there isn't a sufficient ground plane for the antenna, in my opinon.

Artex's instructions say to put the ELT where it'll survive a crash, and keep the antenna cable run short. So after some discussion on the RV list, which yielded very little in answering my questions (which basically was about a proper ground plane for the antenna) , I visited this site and got the idea for the location from it. I like it.

So today, I built a gizmo for installing it.

As I indicated, I'm going to position the antenna out in the breeze. There's one major problem with this, however. I have a tri-cycle gear RV-7A. An interesting thing happens with tri-cycle gear RV-7As when they crash, they flip on their backs.

It's possible the vertical stabilizer would keep the antenna functioning. There's a switch on the instrument panel to "arm" the ELT. My emergency checklist will include activating the ELT in the event of an emergency, in progression with setting the transponder to 7700 and issuing a mayday on 121.5.

I still have to run 5-conductor shielded wiring to the panel. That should be interesting since I'm running out of room to run wiring through the 705 bulkhead, especially since one pathway is taken up by the manual trim cable. But that's a chore for another day.


  1. Hi Bob,

    nice story, especially so because it makes me aware of non-European aspects of aviation.
    This mounting the antenna on the outside: aren't somewhat concerned that you might loose that part during those instances you need it the most?


  2. Hi Hans!

    Yes, that's exactly what I'm worried about and it was one of the reasons I posted a question about it to the RV List.

    There is, it seems, a tradeoff in this excercise. Putting the antenna on the outside increases the chances it will work UNLESS the RV flips on its back.

    Putting it on the inside as many do (behind the rollbar) increases the chances that it won't work, but also increases the chances it will still be intact in a crash.

    It's a very difficult situation, if you ask me.

    The way I've chosen to get around it is to manually energize the ELT if I should get into an emergency BEFORE I crash. That at least will give people an idea where I am if the thing is destroyed on impact (in which case, I'd probably be destroyed too).

    There are times when that's not an option, as the video showed. But in times like that, the ELT isn't going to help anyway.

    I'd love to hear more ideas of how aviators approached this.