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406 ELT

VA Maule

Well Known Member
Working on the installation of an Artex 345 ELT. The instructions are not very helpful regarding antenna installation " Select a suitable location where the antenna can be installed vertically "&" guidance may be found in AC 43.13-2, Chapter 3 ". With this unit ( all 406 ELT) sending their signal to a satellite the antenna must be installed on the top side of the airplane per Artex technical support.
So here's the question has anyone figured out where to install the antenna? Per my attempts at selecting a location no suitable location can be found on a RV-8 with a slider canopy. To the exterm rear of the fuselage where it's not interfering with the rear canopy skirt the wind blasts would cause the stainless steel whip beat upon the vertical stabilizer.
In the call to Tec support when I explained my plight the guy I spoke with he didn't know what a RV8 is and when I explained what it was his reply was "we don't do experimental "
Any ideas or suggestions
 
I put mine on the aft portion of the right back-seat armrest.

The concern I have is that if you make an off airport landing there's a good chance the airplane will end up on its top; therefore the antenna should be on the bottom???
 
One location that works at least somewhat well is just aft of the canopy in the fully open position, canted at about 10 or 11 o'clock when viewed from behind the aircraft, bisecting the angle between horizontal and vertical stabilizers.

The '8 with a slider makes antenna installation a challenge - there's just not much real estate available.
 
If there is a good mounting spot on a RV-8 for the ELT antenna, I'm still looking for it.
Less than ideal spots
- Best less than ideal spot- right above the F-807-1 bulkhead, on the front edge of the turtle deck skin, you might have to notch the antenna base to clear the canopy frame when closed, bend the antenna wire sideways & attach rubber knob so it doesn't scratch the canopy. Best exposure but ground plane compromised.
- A bit more less than ideal- mount on rt arm rest, secure antenna wire so it doesn't stab passenger, questionable broadcast properties as is sheltered.
- Again lower on the ideal scale- mount on right cockpit side wall so antenna wip sticks up through roll over cross bar, more open but bars very disruptive to broadcast but is mostly out of the way for passenger.
- Maybe more ideal if you pre-plan to crash upside down- under horizontal stab pointing out the side of the fuselage, bend the wip portion of antenna back, kind of protected area, as mentioned preferred if you do end upside down, probably will need replacing every so often due to turbulent air flow causing fatigue damage to the wip.
- Worst ideal spot- bracket on upper edge of firewall in engine compartment- I think that is a crush zone...

Canadian Joy suggested a good spot actually. A alternative would be to mount directly ahead of the Vert Stab and fashion a notch into the canopy skirt to clear the antenna base (dreaded fiberglass work though). & consider controlling antenna wip damage to the Vert Stab some how.
 
No good spots

The idea of clocking between 10 to 11 as far aft as possible is the better option other than the issue of working in the very narrow tail cone. I'll have to do a test fit of myself to see if it would even be possible to get me far enough in there to get the job done ( note to self make sure to have a helper to pull me out)

Believe I'll have to think about this a while longer. In the meantime any more ideas and suggestions are truly appreciated
 
If you put the antenna on the side of the plane it won't matter if you crash face up or down. Just saying!
 
If you put the antenna on the side of the plane it won't matter if you crash face up or down. Just saying!

But it will matter if you crash on your left or right side. :)

How about mounting it in the fairing that covers the vertical to horizontal stab intersection? It's been a while since i've looked at an -8, but that must be behind the -8 canopy when it's open?

You could even go back down one side of the vertical stab, and mount it on an angle between the two... Of course you're back to the "which side do I crash on" question.
 
I still like a horizontal mounting under the fiberglass empennage fairing. Protected during accident sequence and again, who knows what attitude the bird will wind up. Any external mount is more susceptible to damage. Some DAR's frown upon this setup and require mounting per manufacturers instructions.
 
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I still like a horizontal mounting under the fiberglass empennage fairing. Protected during accident sequence and again, who knows what attitude the bird will wind up. Any external mount is more susceptible to damage. Some DAR's frown upon this setup and require mounting per manufacturers instructions.

While you may well like that installation location, the reality is that it absolutely sucks from the perspective of Radio Frequency performance. After all, it's an antenna, so it's job is to work at radio frequencies. By installing the antenna under the empennage fairing one is grossly handicapping ELT performance right out of the box.

Yes, any external antenna can be swept off in the crash sequence. In fact it's likely safest to say that any antenna installation is a bit of a **** shoot since we really have no idea what will happen in a crash. All we can do is our very utmost to make the ELT installation as good as we possibly can, to put as many variables to work in our favor, then hope the crash isn't terribly violent.
 
AC 91-44A allows for internal ELT antenna mounting when external mount is not practicle. You determine practicle.
 
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All we can do is our very utmost to make the ELT installation as good as we possibly can, to put as many variables to work in our favor, then hope the crash isn't terribly violent.
One other thing to keep in mind: If you're relying on the crash to set off the ELT, you're throwing away your best chance of being found *at all*. Your ELT (or SPOT, InReach, whatever) needs to be calling out the cavalry *before* you hit the ground. The GPS in a fixed 406 ELT won't even start trying to find it's position until it's activated... if it's upside down, it won't ever find it.
 
One other thing to keep in mind: If you're relying on the crash to set off the ELT, you're throwing away your best chance of being found *at all*. Your ELT (or SPOT, InReach, whatever) needs to be calling out the cavalry *before* you hit the ground. The GPS in a fixed 406 ELT won't even start trying to find it's position until it's activated... if it's upside down, it won't ever find it.

Rob - not disagreeing here, just hoping to refine the general understanding of ELT operation...

An ELT which is connected to an external position source is getting position data all the time, as long as that position source is active and can see the sky. With this in mind we should understand that such an ELT will broadcast GPS position coordinates in the first transmission burst, 50 seconds after crash activation or manual switch activation.

Other ELTs such as the Kannad Integra which have a built-in GPS receiver behave as you have mentioned, needing a view of the sky in order to get a position fix, and that fix may not be broadcast on the first burst, depending on how quickly the GPS can get a position. It may never get a position fix, and if that's the case the ELT still broadcasts but without the position data.

Interestingly, the search radius associated with 406MHz ELTs is considerably smaller than that associated with 121.5MHz ELTs, so even without GPS data the 406MHz ELT has already reduced the search area considerably. That's when the built-in 121.5MHz homing signal, which broadcasts continuously except when the 406MHz burst is being transmitted, comes into play, allowing searchers to home on the ELT.

Another interesting point is that the 406MHz signal is very robust, about 5 watts, compared to a typical 100 milliwatts of 121.5MHz signal. That whackin' big 406MHz signal can get through a surprising amount of "stuff". More than one ELT owner has discovered the hard way that 406 signals travel right through hangars!
 
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