On Saturday, June 20, 2015 at 1:36:28 AM UTC-7, wrote:
What I mean is a logbook entry stating that the installation was performed using approved data - the ELT manufacturer's installation instructions, AC43-13, aircraft manufacturer's maintenance manual or TN etc. The sorts of things that the document you linked to talks about. I would like to find something like that that states an antenna installation that's practical in a non metal glider is OK. As yet I haven't and as far as I can tell it would be contrary to the ELT manufacturer's installation instructions and the linked AC seems to state that if one does that it is no longer a minor mod. There's a DG TN about 406's but it's not available online so I don't know what's in it.

First just a nitpick, an minor alteration does not need to utilize approved data, it may utilize acceptable data or be performed by elementary operations. There is clearly some gray area here. But to your point, maybe in say a silly case I could imagine an FAA inspector measuring an ELT ground plane and saying you made this 8 inches when the installation manual says it should be a minimum of 12 inches might cause a problem, but I'd hope everybody has better things to worry about that things like that.

I doubt any ELT manufacturer has really looked at what would be needed to get a really good practical ELT install in a glider, let alone wrote this up, there is just no market for them. Several glider manufactures have different documentation that mentions installing ELTs (sometimes just in the pilot/maintenance manuals), most are brief and mostly useless. e.g. Schleicher just says it's possible to install an ELT antenna in my ASK-26E in the luggage space extending into the canopy area.... ah right, totally impractical/useless. I don't know how much effort DG put into theirs, but it sounds at least like more than typical.

I don't understand the reference to "non-metal" part, a pure fiberglass fuselage might in some cases provide be an easier option as you might be able to install an anteena inside the fueslage, but given antenna lenths and desire to keep it away from conductive parts etc. even that may be hard.

Are you really willing to drill a hole in the upper fuselage on any metal or carbon fiber fuselage glider and bung an big ELT antenna there? Most glider owners are not. Which at an extreme results in things like ELT antenna installed somewhere inside the cockpit, or bent under the RF transparent area of a turtledeck etc. often not ideal. Sometimes with no ground plane at all. Installs are trade off and hopefully one the owner and A&P is well aware of. And that is all not a bad thing, working to do the best practically to get an ELT installed is likely better than not having an ELT. But with the poor activation results of ELTs (even if optimally installed in a GA airplane) as well as the difficulty isntalling the antenna in most gliders and the confidnce/testability provided by tracking solutions like InReach or Spot I would hope people are looking at ELTs only as a backup to InReach or SPOT devices used for tracking.

I just thin the bureaucratic process is the wrong thing to to think about here. Discuss that with your A&P. Look with them at what antenna installs may be practical and decide whether it is worth doing at all or not. This all needs some common sense applied to trying to install something that hopefully provides some SAR help. There is no regulatory requirement for gliders to carry ELTs, not requirement that any ELT installed in a glider must be TSO approved, installs in practice are usually not done as major alterations, and there are better options than an ELT in the fist place.

If you really wanted to get a 406MHz ELT installed as well as possible in a glider then it may be ugly and expensive. e.g. maybe cutting holes for an external antenna, and installing a ground plane or maybe going to a high-end ELT with dual-outputs and at least trying to do a really good external mount for a single band 406 MHz whip or blade antenna (therefore a short antenna that needs a small ground plane) and then going with a less optimal 121..5 Mhz antenna mounted in the cockpit or external with a sub optimal ground plane etc. It's only the 406 Mhz signal that is used to alert SARSAT/COSPAS. And keep the ELT solidly mounted in the correct orientation and all the coax cables as short/secure as possible. Think about carrying a collapsible portable antennas where you can remove the ELT and place it on the ground with that antenna (good idea if your glider ends up broken/on it's side etc and you are still alive enough to do so.

I had purchased a nice Artex 406 MHz ELT and spent much of a day trying to work out how it could be realistically/well installed in a new ASH-26E. I decided it was impossible and gave up and returned it and purchased a McMurdo 406MHz PLB (with GPS), I also had a SPOT tracker at that time. If doing this today I'd use an InReach (mounted on the glareshield/panel with good sat view) and a 406 Mhz PLB (on parachute harness). That combination is much better than a 406 MHz ELT. And if you bail out it is nice to have a PLB with you not with the glider. But if you also want/can manage some reasonable install of an ELT as backup beyond that then great.