ELT antenna question

jlfernan · Post by **jlfernan** » Sun Dec 31, 2006 9:41 pm

I plan on simply putting the ELT antenna on top of the aft portion of the fuselage. My question is do I need a doubler beneath the skin and about what size?

captain_john · Post by **captain_john** » Sun Dec 31, 2006 10:33 pm

Hmmmm, Jorge...

I hate to answer a question with a question, but why put it out there in the wind?

I thought most guys were tucking them away inside the airplane and what not.

I was thinking of mounting it in the baggage compartment on the longeron kinda like Dan did on this page:

http://www.rvproject.com/20031020.html

BTW, what do you think about going with the 406 mhz unit? I understand that the 121.5 units (aside from being pretty much useless) won't be supported much longer by SAR units!

The 406's are pretty pricey, but what is you hide worth? I dunno. I s'pose they will come down some in time. I think I will go with the 406 unit.

Happy New Year!

CJ

svanarts · Post by **svanarts** » Mon Jan 01, 2007 12:16 am

Another favorite out of the wind location is mounted under the empanage intersection fairing. Others have run them down the inside of the gear leg fairings.

In my RV-4 it's mounted on the floor and runs up the bulkhead that holds the rear passenger's seat back. The only remark I got about it from the FAA during the inspection was that if I flip over, the satellites will have a hard time locking on to my signal. He finished with, "oh well, if you flip over bad enough to set off the ELT there won't be a need to find you right away."

Nice!

captain_john · Post by **captain_john** » Mon Jan 01, 2007 8:44 am

Here is the SARSAT Phase Out Plan,

http://www.sarsat.noaa.gov/Phase-outFinal.pdf

CJ

captain_john · Post by **captain_john** » Mon Jan 01, 2007 9:02 am

This antenna is 406 only, but is so small, it could be belly mounted next to the transponder antenna!

http://www.artex.net/documents/110-329.pdf

I just noticed this too. Artex is just down the road from Van's!

CJ

Wicked Stick · Post by **Wicked Stick** » Mon Jan 01, 2007 9:42 am

I don't think I'd want to mount it on the belly. In a forced off airport landing, chances are greater that it will be broken off if your landing in rough terrain.

I'm planning on mounting mine like the picture below. I might even mount the ELT in that area or in the baggage compartment.

captain_john · Post by **captain_john** » Mon Jan 01, 2007 9:51 am

Good point, Dave.

Usually the "spare" antenna is fastened to the ELT so that you can remove it from it's mount, connect the "spare" and set it out next to the site and wait!

The tailcone mount is cool! Ideally, the antenna should be pointed upward. So, in the event of an actual emergency you will need to dig a hole and plant your propeller in the ground in order to achieve the best performance!

CJ

svanarts · Post by **svanarts** » Mon Jan 01, 2007 1:30 pm

That's the catch. To really work good your ELT antenna has to face the sky. So what's the normal mode of your accidents? You think you'll flip over, put it on the belly. You think you'll pancake it in, put it on the top. Not planning on using it at all, put it anywhere you like.

Wicked Stick · Post by **Wicked Stick** » Tue Jan 02, 2007 10:30 pm

Yeah, I think it's a crap shoot on guessing how you end up in a crash landing. I think I just want to make sure I mount the antenna in a place where the least amount of damage will occur so that it remains operational.

In the event I can walk away from the accident, I will most likely want to grab the ELT and install the remote antenna and keep it with me. If I'm unable to egress then I hope that the current position of the install provides enough range for help to find it.

svanarts · Post by **svanarts** » Wed Jan 03, 2007 12:56 am

I'm thinking of running it along the backside of my rollbar in the RV-7. That way if I flip over, there should still be enough daylight for the antenna to get a signal out, if I stay upright, so much the better.