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406 vs 121.5 ELT (from Another crash in AK thread)

I mounted my attenna inside with the whip pertruding through the fabric to the exterior. I also met the specs for the ground plane inside the aircraft. The location of the antenna is behind but on the upper baggage shelf. I actually extended the shelf beyond the usable area rear bulkhead to insure the proper specified area.
 
from section 3 elt 406 install

http://www.ackavionics.com/pdf/E-04_REV_2_SINGLE_PAGE.pdf

THE ANTENNA MAY BE MOUNTED INTERNALLY IN COMPOSITE CONSTRUCTION, AND TUBULAR FABRIC COVERED AIRCRAFT AS LONG AS THE FABRIC OR COMPOSITE MA- TERIAL IS OF A NON CONDUCTIVE NATURE.
so does the aluminum in dope silver count as conductive?

or are they referring to a cover job like Superflites System6 where its basically auto primer instead of a aluminum/silver layer or whatever....

had myself almost convinced this would be ok, but since i am probably not going with this elt now i will have to see what the new ones install says....

the other thread points out CURRENT aircraft manufactures mount the antennas inside(Scout, Husky...) but are they not dope silvered coatings????
 
mit greb said:
My math is a little fuzzy but 1/8 is still better than 0 isn't it?

Not real sure what your point is (no smilie) but like Mr. Mike said...
MTV said:
It wouldn't make much sense to spend this much money and then impair the signal......

Which was my point.
I dunno about Superflight, Huskys/Scouts, etc, but MY fabric has several coats of aluminum (Stitts) and it cut the RF getting out into "the air" down to 1/8 of what the TX puts out. ANY attenuation is unacceptable.

Mike, it sounds more & more like your 'Mick" is the best info source! Good on ya for finding HIM.

Again, I just posted this as my experience, but mainly to let those with an (any) antenna inside the fuse know about the effect of aluminum covered fabric. So there ya go. :)
 
Mike,

Thanks for your research and effort on this subject.

This is one of those times when a re-evaluation of the certification process in in order. There are times where advances in technology are available but the certification process serves more as a barrier to entry than a process that benefits the end user. An improved activation switch would be better than the old spring and ball but we must wait for a perfect switch that has jumped the hoops imposed by certification standards. In the end we get a delayed and ridiculously expensive technology that will serve only to cause some of us to pass it's install because of price, or for those that are happy to be first in line, a delay in the installation.

It's not hard to envision a three year old having a cheap Mickey Mouse watch with a gps tracker and a fall switch sensor that dwarfs the expensive and untimely technology we will end up with because of the antiquated certification process that we must put up with in aviation.


Jerry
 
Moved from other thread.....
Gary Fields said:
........

The mounting of the ELT in the ACS Otter was near the tail on the pilot side about 12" above the floor. The bracket and restraining strap, complete with Velcro appeared to be factory materials. What Bo was installing was a more substantial bracket with a metal restraining strap. Bo told me that the GCI Otter's mounting was nearly the same as his, that is what prompted him to make the change.

So It was a side mount.....

Did the Velcro come loose ? Or did the bracket pull free from plane?
 
Mike,

I asked Mick whether the velcro straps these new ELTs are attached with are adequate, and he noted essentially that the velcro far exceeds the certification standards.

MTV
 
ELT antennae in tail of cub

As it relates to the idea that an ELT antenna will not transmit through the aluminum silver on the fabric of the tail cone of a Cub, I take exception.

My son several years ago was out flying his J-3 and on returning to our grass strip he made what I considered to be a relatively good and gentle landing. After landing he pushed the Cub back into the hangar and proceeded to remove the bugs he had assassinated on his recent flight, and I continued with other projects inside the hangar as well. After about an hour I hear an airplane strafe our field and we both ran outside to see which of our friends had come to pay a visit. It was a somewhat 172-ish looking airplane, which we later found out was a T-41 belonging to the civil air patrol. The aircraft drug the field two or three times and left the area. In about 15 minutes after theT-41 left a white van bearing a civil air patrol emblem on the door arrived.

The fellows in the van informed us that they had tracked an ELT signal to our location and their electronic wizardry, which they had in, hand Pointed to the just landed Cub. We made a check on 121.5 and sure enough the ELT was activated. This ELT installation was done in preparation for a cross-country from Georgia to San Diego and return. An elt antenna was mounted inside the tail cone of the aircraft, and continues to be.

After serving several years in the Signal Corps, two of which were at Fort Wainwright in Fairbanks I would tend to agree that the silver would have attenuated the signal to a point of being useless. When I installed the antenna in the cub tail, it was at the insistence of my two sons who were adamant that we not diminish the classic Cub look with the likes of antennas stuck all over it. It never dawned on me to think about the fact that the tail was essentially an aluminum skin surrounding the ELT antenna.

All that said, I am still astounded, first that anyone would have shown up within one hour after the landing, and secondly how did they received enough signal to make sense of where we were.

At any rate I thanked the folks with the civil air patrol profusely, provided them with refreshments and offered to pay any expenses they might have incurred looking for the possible crash site. They appropriately chided me and my son for not verifying the status of the ELT after landing, and espoused that they were happy to find all was well and indicated there would be no charge, this time.

Until reading the above post I had never given a thought to the possibility that the tail cone would be a poor location for a transmitting antenna. I also offer no explanation for why the ELT worked so well inside the tail cone as well as being inside an all steel hanger.

Alan Wayne
Flowery Branch, Ga
 
DSCN1441.JPG


Cub Crafters molds a pocket in the seat base of the Carbon Cub for the ME406 ELT. It looks to me like it is well captured in this location.
 
mvivion said:
Mike,
Your point is well taken, and as I said, this discussion and your post has encouraged me to chat with my mechanic to see precisely what an "ELT Annual" is, in his mind.

One of the questions I asked Mick specifically was whether there is an ELT on the market that will connect to a PORTABLE GPS. His answer was no, at the present, but that Artex is about to hit the streets with one.

...
In any case, he did say there are ELTs out there which will "talk" to some panel mounted GPS units at present.

Those are MUCH more expensive than the expensive to begin with basic unit....because of the cost of certification.


MTV

Any ELT that can interface with a panel mount GPS can interface with a handheld GPS as long as it outputs a compatible format. Artex ELTs, for example will accept Garmin or NEMA 0189 formats. So with the proper GPS-to-RS232 cable, you could connect an eTrex, Nuvi or marine GPS to your ELT. Unfortunately, the ELT/Nav interface is about $1800.

I'm waiting for some enterprising smart person to wire a $400 PLB to an inertia switch and install it as a "minor alteration"...keeping the 121.5 ELT to be legal, of course.
 
$225 at Aircraft Spruce.
http://www.aircraftspruce.com/catalog/avpages/artexnavinterface.php

I've not looked into the $300 #232 adaptor but I find it interesting that it's called a 232, which is the same as the output ports on a typical Garmin GPS. I wonder if this adaptor is a plug-in? It sounds like it. From the Garmin 296 spec page "Interfaces: Two RS232 ports with NMEA 0183, RTCM 104 DGPS data format and proprietary Garmin USB interface"

Artex is careful not to say it'll work with handhelds because handhelds are not approved for aircraft navigation. Or so I was told. Of course that was two years ago during my discussions with Artex when I was installing my first ME406 and needed some advice.

SB
 
So Stewart, are you going to buy one and let us other ME406 owners know if it is that simple? I've got a panel mount GX55 GPS in the T41B with an output I'll have to check on now to see what it is.

I looked at the earlier newspaper link you posted. It was timely as I've been checking Captain America's SPOT track out of KOTZ. I took the gist of the article to be; don't rely on one system especially a 121.5 ELT and take advantage of the newest tracking services like SPOT and Spidertracks. That there is technology available today that would eliminate all of these long drawn out expensive searches that also put searchers at risk.
 
No, I have no plans to interface a GPS. The non-interfaced 406s are providing very accurate location info to the rescue crews. On top of that I fly with a Spidertracks device and my ELT info directs RCC to my tracking log. But, at 150mph and 2 minute interval reporting the Spider could be 5 miles off. RCC can get way, way closer than that with a standard 406 burst. You SPOT tracker users who feel safe? In my 180 a SPOT report (10 minute interval) could be 25 miles off. A 25 mile radius leaves a very big search area. That's a 50 mile diameter circle.

Here's the article link you mentioned. More to the point about the weakness of 121.5, read the article about the two guys who crashed at Friday Creek. I had originally asked why they hadn't triggered their ELT. It turns out they did. Nobody heard it. Nobody came. That article is in the "Happy Ending" thread.
http://www.alaskadispatch.com/dispatches/news/6597

SB
 
StewartB said:
You SPOT tracker users who feel safe? In my 180 a SPOT report (10 minute interval) could be 25 miles off. A 25 mile radius leaves a very big search area. That's a 50 mile diameter circle.

SB

I think the idea is that you're alive enough to hit the SOS button on the spot and get help started your way. If you're already dead, time is not of the essence. If you're too injured to operate the spot, well then you better hope your ELT didn't shear off the mount, and the antenna didn't get cut off, and the battery isn't deat...
 
Couple of other things that I thought of after sleeping on it...

With regards to antennae getting stripped off by trees in a crash, choose the whip antenna. It's bendy and would be less likely to get ripped off as opposed to the rod antenna. Also, is it possible (and legal) to mound the antenna connector on a less rigid platform so that if it does get ripped off, it pulls the mount through the fabric but stays connected to the coax?

And as far as having an internal antenna, my old 121.5 ELT has a fixed whip antenna and sits inside the metal fuselage of my 170. When I was cadet in the CAP, I searched for and found several of these inside metal airplanes that were inside metal hangars, so it is possible. Not sure how that would affect the 406 signal though...

SO, how about putting a splitter on the antenna connector and running an internal and external antenna? Kind of a belts and suspenders approach? Thoughts, comments?
 
Two antennas = less signal being emitted from each. Bad idea, in my opinion.

Also, remember that UHF signals (as in 406 mHz) act VERY differently than do VHF (as in 121.5 mHz) signals, when it comes to blocking, deflecting, etc.

UHF signals are EASILY blocked. The higher the frequency, the easier it is to block the signal, so I don't think you can fairly compare the 121.5 and 406 beacon antennas in this regard.

MTV
 
Antennas

Where on earth can you mount a vertically polarised externally mounted antenna aft of the cabin with sufficient ground plane on a Super Cub?

Anyway, if you crash in such a manner that your vertically polarised top mounted antenna is still intact, you'll more than likely be stepping out of the plane and activating something manually, or wandering over to the nearest house and asking to use the phone. If you smash the thing up severely enough to set off the ELT, more than likely the antenna won't be intact if mounted externally and it certainly won't be pointing up anymore.

I remain unconvinced to move it from inside the fuselage.

Cheers,
Andrew.
 
Andrew,

You make a good point, and this is yet another of the many conundrums we face in this whole transition to 406 beacons.

MTV
 
MainlandCub said:
Where on earth can you mount a vertically polarised externally mounted antenna aft of the cabin with sufficient ground plane on a Super Cub?
...[snippage]...
I remain unconvinced to move it from inside the fuselage.

Quote from earlier mess: ""I had read (I think here, some time back) that some have the ELT antenna mounted inside the (fabric) fuselage. I thought this was a good idea, to help keep it protected from brush/branches/whatever, AND keep it out'a the way for sweeping snow off. I checked w/my local 'lectronics guru & he thought it would be fine too. He understands RF stuff & said the tubes would not appreciably reflect power nor hurt transmission.

THEN he said, wait... it's not just fabric, it has a few coats of aluminum on it. He has a super-testing gizmo (I think he said it was $14K!) Anyway, we tested transmission from outside, and inside, and the aluminum cut it back by 10db! He said that's effectively letting 1/8th of the RF out.""


Note: I do my own maintenance (with adult supervision).
Mount... what I did was to screw a piece of aluminum to the aft U-channel (on my 18-A) above the ext.baggage area, and then glued it to the underside of the fabric behind that. After much pulling/tugging (my cert. process) I was satisfied that it was as strong (G-force wise) as the ELT mount itself, so drilled the hole & mounted the vert. antenna in the middle of the aluminum.

Tested again with his expensive gizmo & 100% output.
This guy is a retired electronics professor & also his hobby. He built our FM radio repeater system(s) and also the TV/radio rebroadcasters on the fire lookout mtn. Point is: he knows what he's doing.

If you got CAP attention through your "aluminized" fabric & metal hangar, you were lucky. As in anything, YMMV. Me... I want ALL of my RF reaching out there!
 
He used a spectrum analyzer , probably part of an IFR service monitor. Good catch on the aluminum fabric! This "catch" should become part of some advisory for fabric aircraft so others don't rely on an internal mounting. Did you move the monitor around the aircraft while testing and check all directions? Was the 10db at 122mhz or 406? If 122 then 406 should penetrate a lot better. If 406 then forget 122. Do all the coating systems used on fabric aircraft have aluminum in them??
 
Update,

FYI, the RS 232 gizmo from Artex that Stewart posted a link to on Aircraft Spruce's catalog is a real deal. I was at the AOPA conference this last week and talked to Scott, who also works for Cobham.

Scott showed me that device (actually, there are two of them--one that'll work with a portable GPS, the other is designed to work with a panel mount--different outputs, depending on the manufacturer as well). The device is NOT yet certified. They are expecting certification within the next few weeks, but Scott also rolled his eyes when he said that. Certification has been very time consuming.

Nevertheless, this looks like the hot ticket. He's estimating street price between $250 and $300. The unit plugs directly into the connector on their (Artex) 406 beacon, and has a single wire that goes forward to the GPS unit. I didn't ask him all the models that this thing will work with, but he said basically it'll work with most if not all panel and portable GPS units that have an output. My 396 will definitely work.

I also asked him about the question of mounting location of the antenna inside a fabric covered airplane. He said he really thought that was the best choice. He didn't think the aluminum in the coatings would attenuate the signal THAT much, but his point was that mounted inside, the antenna is MUCH more likely to survive an accident.

I can't believe that AIrcraft Spruce keeps posting this stuff on their online catalog, complete with prices, before the stuff is actually for sale. Amazing. Spruce has had one 406 beacon advertised for over three months now that I know of, and it's still not certified.

Anyway, I'm thinking this winter I'm going to buy an Artex 406 beacon, as soon as that little GPS connector gets certified. That way, I can get the installation and wire runs done all at once.

MTV
 
mvivion said:
Two antennas = less signal being emitted from each. Bad idea, in my opinion.

Also, remember that UHF signals (as in 406 mHz) act VERY differently than do VHF (as in 121.5 mHz) signals, when it comes to blocking, deflecting, etc.

UHF signals are EASILY blocked. The higher the frequency, the easier it is to block the signal, so I don't think you can fairly compare the 121.5 and 406 beacon antennas in this regard.

MTV

At a safety seminar last week an attending experienced CAP guy noted that 406 signals can be blocked by dense foliage.Doesn't sound like a good thing to me.

Bill
 
There is so much piss poor information on the internet. Guys should try harder not to proliferate it.

Consider the article in the latest FAA Safety magazine, page 23. This story took place when satellites were still listening for 121.5, as bad as that service was. If the same accident happened today the boy in the story would also be dead. Got kids?

http://www.faa.gov/news/safety_briefing/2010/media/NovDec2010.pdf

Fly safe, y'all. When that fails, do your best to stay alive.

Stewart
 
Anyone know of any one place we can look at to compare the different 406 ELT's? Something with recent information? Something that specifically describes what each brand/model will do,...and what they won't do?

I'm not afraid to admit I'm seriously confused and confounded (which isn't too unusual). As important as this issue is, it seems like there is a lot of contradictory information out there.

Jim W.
 
I was talking about signals getting out of a metal/tubular airframe. 406 will always do it better. I'll try this, ever notice how if you are listing to a AM broadcast signal and you drive inside a metal lattice structure bridge, the signal (if you are at any distance) will be gone. If listening to an FM station ,no problem or change. The "holes" in the lattice will pass the 88-108 mc signal but not the .550 to 1.700 mhz signal. This is due to the longer wavelength (lower frequency) of the signal not being able to penetrate the bridge lattice. The effect is immediate as soon as the structure openings are even a fraction smaller than needed for a given frequency. The 406 signal requires approx 1/3 the "opening size" in a structure to leave/enter with minimal attenuation compared to 122 mc. Another example of this effect is the door/glass on your microwave oven. The little holes are smaller than the frequency used to cook your food. If the frequency were raised enough the signal would come out into the room :cry: . Now as regarding attenuation by brush, trees etc. that is a valid argument and ground searching for 406 would be somewhat more difficult in certain terrain. I really believe that satellites should receive 406 just fine if no obstructions were in the way. Personally I think the survivability of the smaller antenna and the ability of the 406 signal to escape the airframe better should add up to a better satellite SAR outcome. Neither 122 or 406 will escape a closed aluminum structure with any strength unless they can find a proper sized hole for the frequency. As regards an uncovered super cub fuselage, an open door would pass the 122 signal but not much else. To a 406 signal it's as if the fuselage doesn't exist. Mucho big holes. Now with an aluminized cover all bets are off.
 
qsmx440 said:
Good catch on the aluminum fabric! This "catch" should become part of some advisory for fabric aircraft so others don't rely on an internal mounting.

This was exactly my point in pointing this out. Nothing more. There ya go. As always tho, YMMV. Just don't ASSume (or take someone's word) that your (expensive) distress signal will get out when you NEED it to save your A$$. As you've read in this thread, there are lots of opinions & "someone said" ... They ain't all correct.

Did you move the monitor around the aircraft while testing and check all directions?

Nope, he had his big thingie in the house, it needs 110V. His antenna taped to one of the big windows in front. Airplane was "quartering away" @ about 40 yds.

Was the 10db at 122mhz or 406?

406. That's the one we care about! :)

Do all the coating systems used on fabric aircraft have aluminum in them??

Fabric needs UV protection. Aluminized paint is the common form (several coats until NO pinholes of light), but there are others. Some use house paint. heh.
 
55-PA18A said:
Anyone know of any one place we can look at to compare the different 406 ELT's? Something with recent information? Something that specifically describes what each brand/model will do,...and what they won't do?

I bought mine from a major dealer in Vancouver, through a fellow BCFA director. Thing is, they sell ALL the brands, so he wasn't pushing HIS brand.

FYI, his name is Steve Nunn, eddress is steve@stevenunn.com
This guy is a no-BS straight shooter.
 
In talking with the guys at Cobham (who makes Artex), I found them to be totally professional, and at no time did either of these guys cast aspersions on the other manufacturer's ELTs.

The problem is with retailers, who all seem to be trying to get out ahead of certification on these things, and list them "for sale" even though they're not yet certified.

There IS a tremendous amount of BS out there on this subject, I agree.

One point: The 406 signal emitted from these boxes (all of them) goes out at 5 Watts. That is a LOT of power, compared to the 121.5 signal, which goes out at somewhere around 250 milliwatts. So, the 406 signal is much more powerful than the 121.5 signal ever has been.

If indeed the 406 signal IS attenuated by, say 1/8th of it's strength by the aluminized fabric when the antenna is mounted inside a fabric plane, then it is STILL emitting a MUCH stronger signal than the 121.5 beacon would have. And, remember, the 406 beacon only really needs to get ONE good hit to a satellite to start a search.

As to ground searches, the 406 is NOT used to direction find these beacons. The 406 signal, while it's much more powerful, is only emitted as a BURST every 50 seconds, and that burst is very short, as in milliseconds. So, you CANNOT DF the 406 signal, which is why all these boxes also have a continuous running 121.5 beacon as well as the 406. That is what the air or ground searchers will DF on.

MTV
 
Thank you MTV. Last time I new anything about ELT regulations, it was 121.5 only. Sounds like the new ones have 406 digital? and 121.5 analogue?? At some point I need to get up to date. 30 some years ago I did do SAR ops around the Olympic Peninsula and was out ELT searching for downed aircraft at least once a year in these mountains. Lots of bodies. GPS seems to have stopped all of that . 121.5 was awful in the mountains with steep terrain and trees. We would have several crews out and each of us would come up with different solutions as to direction. The reflections and multi-path made it very difficult to get accuracy even close in. Everyone did fine during training but murphy was always at work in the field under actual conditions. As to the power and propagation I do know that stuff from a technician standpoint. (read barnyard :-? ) and each 3 db is a half (or double power point, so to loose -10 db from 5 watts: 1st -3db= 2.5w, 2nd -3db=1.25w, 3rd -3db (-9db so far) = .66w and with barnyard rounding of the last 1db you get maybe 1/2 watt left of your original 5 watts. Imagine you are a TV station trying to add +3db increase (1,000,000 watts) to your original 500,000 watt signal. The power bill could go up considerably :lol:
 
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