Zenith Aircraft Builders and Flyers
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ELT antenna replacement options
So it's time to replace my 121.5 ELT with a combination 121.5/406. The install of the ELT and cockpit wiring are pretty straight forward, but the replacement of the antenna has got me at a bit of a loss.
The ELT antenna itself is located on the top of the fuse just forward of the tail faring. I can't figure out how to get to it easily to get it out and the new one in.
After staring at it for an hour or two and talking it over with the other airport guys who are sympathetic with my plight we came up with a few options.
1. Disconnect the control cables and get someone skinny to climb back there and undo it. I'm not sure the skin will support the weight of someone in there, or if it's even feasible to climb past the flaperon controls. Looks barely doable and I would support the tail of the plane with some wood topped with foam. Still seems like a risk for damage. Has anyone done climbed back in there and come out unscathed?
2. Cut an access hole under the antenna and reach up from the underside. Looks like my arm would just be long enough. Probably wouldn't be a fun job and I don't necessarily like that idea too much.
3. Leave the ELT antenna as it is and install the 406 ELT antenna where the current com antenna is, then move the com antenna to a bent whip under the fuselage. This is probably the easiest option, even though a bit silly as it leaves useless stuff on the plane. But, least risk of damage.
Any other ideas or thoughts?
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Replies to This Discussion
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Permalink Reply by John Austin on
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If your 121.5 ELT is still functional, one alternative is to just buy a PLB and keep it in the plane.
John
N750A
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Permalink Reply by Nick on
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Thanks for the suggestion - I've already got the ELT and the battery was due in the one that's in there anyways, so this seemed like the better option... At the time...
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... and there are pros and cons to the PLB - a big plus is that it is portable and could also be used for other outdoor activities, or goes with you easily (they're light and compact) if you are down in a remote area and able to hike out. Of course, the big con is that after a crash you have to be not incapacitated to the point that you couldn't activate it, unlike a ELT that will likely (but not !00%!) automatically activate, Fortunately, most of the Zenith aircraft are so light and slow that a crash is low energy and one has very good chances of being physically able to activate either the ELT (if it is not triggered) or a PLB!
John
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Permalink Reply by Bob Simmons on
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I really wish Zenith would incorporate an access panel in the rear fuselage into the design. My plane is getting one, and many other builders have added one as well. The full width diagonal could be eliminated, so you'd have more room. I'm not sure how someone might attempt a retrofit for that, even if you wanted to.
This is really a matter of what effort you want to expend, and the quality of the installation. Whether to go easy or fancy, or somewhere in between, is entirely up to you.
One thing to keep in mind is that antenna mount will probably leak at some point, so you'll have to gain access eventually anyway. For that reason, and because I can be very picky, I'd personally opt for the access panel. But, you do you.
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Permalink Reply by Jim and Amelia Isaacs on
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I’m with Bob on adding an access panel. I did it, and it’s not difficult. My ELT is back in the tail area underneath the antenna so access to both transmitter, battery, and antenna is all via one small panel. Don’t attempt to crawl back there or you will be replacing bent metal.
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Permalink Reply by David Gallagher on
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Since the 601XL already has a lower access door as part of the design, I was surprised to see that you high wing guys did not have one. I'm sure it's a bigger job to incorporate one now, but if you wanted to, the 601XL design would likely be a starting point. You could ask Zenith if it could be a direct retrofit and follow their drawing. It's basically just a square sheet door, a hinge, some stiffeners and a bunch of nut plates. It has been very handy to pop mine open during inspections and when I retrofitted shoulder harnesses.
Dave G.
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Hi David,
Yeah we (701/750) have a belly hatch but in my situation, I wanted the ELT and antenna as far aft as possible, so I added a small access panel to the side of the fuselage to reach the ELT and antenna for servicing and annual testing. Kinda difficult to spot, it’s just below and forward of the data plate.
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Permalink Reply by David J. Beaulieu on
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Another option...drillout the current doubler holding the antenna, cut and fashion an access panel which holds the antenna, reinforce as necessary, install with nutplates and done. (The access panel doesn't need to be centered on the top skin) Good luck with it, not a difficult job, though intimidating (at first) to consider cutting a large hole in the top skin...
Cheers! Dave
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Everyone has their own preferences, but I prefer not to have access panels on top that might leak. This is obviously less of an issue if your plane is always hangared.
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Put in on the side of fuselage if overly concerned with water infiltration. For a top panel that wll be opened only a couple of times over the lifetime of the airframe I would just seal it up with gasket and seam sealer and not worry about it until the next time it had to be accessed. The wing root skins and fuel tank overs are essentially huge acess panels, though admittedly, not on a strictly flat profile.
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As I said, everyone has their preferences. But I spent too many years working leaky airplanes not to think about that stuff. The wing top surfaces are curved, so water doesn't pool, unlkke the flat fuselage, and the wing panels get sealed with paint for the most part.
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On the drive home from the airport I had an idea... Bordering on somewhat comical and not having much to lose, I bought one of those grabby tool extend-a-hand things and was able to undo the TNC connector on the antenna.
I've got some adapters and mounts 3D printing to get a wrench on the end of the grabby tool / broom handle to hold the nut and undo the antenna from the bottom. New antenna should drop right in and with the nut holder on the grabby tool I should be able to get the antenna in from the top and someone on the bottom holding the tool to thread it in.
It's a bit fiddly and cumbersome and kind of seems like weird keyhole surgery on the plane, but I think it beats putting an access panel in! Will report back with the rest of the results when I get to it later this week.
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