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Mounting ELT Antenna

RV505 said:
I would not! I reason that if the builder didn't follow instructions installing ELT equipment designed by enginers/manufacturers they probably skimped or failed to properly follow work instructions in the construction in other areas of their aircraft... Some or one of the areas could be critical... Pretty paint can hide a turd but it can't take the smell out...

No...

A smart person would do a lot of research on the subject, and find that ELT antenna installations involve a lot of compromises for many different situations. As they say, there is more than one way to skin a cat!

L.Adamson
 
I wrote:

I would not hesitate to fly a beautifully-crafted RV regardless of the location of its ELT antenna.

And a response was:

I would not! I reason that if the builder didn't follow instructions installing ELT equipment designed by enginers/manufacturers they probably skimped or failed to properly follow work instructions in the construction in other areas of their aircraft... Some or one of the areas could be critical... Pretty paint can hide a turd but it can't take the smell out...

To which I respond at the risk of prolonging a now dubious discussion by repeating more of my earlier post:

Seriously, this is a subject where all of us as adults need to use some common sense and assume that each of us is smart enough to evaluate the risks inherent in our pursuit of aviation and our comfort level with those risks.

After inspecting a bunch of RV's in the course of serving as an EAA Technical Advisor over the past seven years, and after "inspecting" scads of RVs at airshows large and small, I think I have a pretty good sense of what gives me a warm and fuzzy feeling toward a particular aircraft. I can assure you that there are a lot of beautifully crafted RVs, many of which have the hardware earned in judging, that do not have bonafide ELT antenna installations. A quick jog up and down the rows of RVs at S-N-F and OSH will bear this out. If the lack of a by-the-book ELT antenna installation is sufficient to make a particular pilot avoid a plane, then so be it. But I have seen many RV's that most of us would LOVE to have in our hangar and in spite of there being no ELT antenna in sight, I have the highest regard for the integrity and competence of the builder of those planes. Next time you bum a ride in an RV, take a careful look at it. I bet you a handful of clecoes that more than likely you won't see an external ELT antenna. :)

By the way, any builder who has hung around the RV scene for nearly a decade will be able to quickly sniff out the problems that are hidden by pretty paint jobs. ;)
 
EAA Technical Advisor ?!!! :eek: You gotta be kidding! As a Airline/General Aviation mechanic working 8 hours a day for 25 years I define work procedures and instructions as right and wrong not in warm and fuzzy..
 
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Not a big deal, I think coverage is greater

MarkEsterhuizen said:
So you reckon carrying a cell phone will cut it in an emergency? Here's a map of cell coverage in the continental USA.

The yellow areas are no coverage - that's about 70% of the map.

CelCoverage-USA-T-Mobile.jpg
Negative, I know you are proud of you zinger, but that's not totally correct. It may be true for your plan, but with a dual or tri-band phone you can talk off network or ROAM. The T-mobile composite coverage I looked at is better than your 70% yellow map. Sprints PCS map below shows no coverage areas with white. MT and ND have "other digital service" (blue), what ever that means (probably more $$ to talk). The light & dark green and orange are all the in network and roam digital areas. (Cingular is more spotty in the west, NV, ID, MT, ND and SD)

U.S.coverageMapSprint_663903.gif



PS: My Artex ELT instructions say mount it externally ON TOP of the fuselage. No comment or opinion just another data point.
 
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MarkEsterhuizen said:
So you reckon carrying a cell phone will cut it in an emergency?

Here's a map of cell coverage in the continental USA.

CelCoverage-USA-T-Mobile.jpg


The yellow areas are no coverage - that's about 70% of the map.

That thing can't possibly be right. Are you saying that cell phones don't work except in the pink regions?? Virtually the entire state of Nevada, except Vegas and Reno? Four Corners area? This can't posssibly be right.
 
RV505 said:
EAA Technical Advisor ?!!! :eek: You gotta be kidding! As a Airline/General Aviation mechanic working 8 hours a day for 25 years I define work procedures and instructions as right and wrong not in warm and fuzzy..

Just out of curiosity, how many experimental aircraft have you built? My reason for asking is that in my own building experience I've run into many situations for which there is no standard procedure. Many of the parts on an RV are specific only to this type and it's up to the builder to sort things out as he/she sees fit. In building my 4, the instructions got thinner and thinner as the project advanced. Things like plumbing and wiring are left to the builder's discretion. The same goes for instrumentation and panel layout.

As for the idea that a non-standard placement of an ELT antenna is an indicator of a sloppy builder, I would have to call B.S. on that one.
 
Wonder where Van's mounted their ELT antennas on the factory demo planes. Not implying anything by this...just honestly curious. I mention this in response to some of the "I wouldn't fly in an airplane with an ELT antenna on the inside" comments.
 
RV505 said:
I would not! I reason that if the builder didn't follow instructions installing ELT equipment designed by enginers/manufacturers they probably skimped or failed to properly follow work instructions in the construction in other areas of their aircraft... Some or one of the areas could be critical... Pretty paint can hide a turd but it can't take the smell out...

Wow, this airplane building and flying thing is way too dangerous. I didn't realize my install, or lack of install, hid a deeper meaning. Anybody want to buy a Darwin 7, I'll even let RV505 (whoever he is) be the auctioneer. Cell phone, ballistic chute, flare gun, mirror and lucky four leaf clover included.

Think I'll buy an RV3...............oh, no I can't, they are not required to have an ELT. What do I do, oh, what do I do.

Sorry, bored with this thread. Got some sloppy building to do, after I unfold my arms.

Jest of the message, lighten up guys.
 
what is this ???

MarkEsterhuizen said:
So you reckon carrying a cell phone will cut it in an emergency?

Here's a map of cell coverage in the continental USA.

CelCoverage-USA-T-Mobile.jpg


The yellow areas are no coverage - that's about 70% of the map.

Here's Canada:

canada.gif


85% not covered.

this is all out inaccurate, this map is way off for sc, i know phone coverage to be more like 100 % in this state it shows myrtle beach as no coverage i think your map is for your carrier..
 
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That maps gotta be at least 10 years old - not even close. Personally, I travel all over the continental US daily for my job - very few locations without cell service, and this is oil-field remote locations I'm going to, not major cities.
 
Flying higher than required minimums and with greater than minimum fuel increases chances for survival-like optimum mounting of an ELT antenna, it just makes common sense. At the same time, FARs dictate annual condition inspections, pitot static, and ELT checks. Probably because someone decided there is a limit to common sense.
If common sense fails, consider whether your insurance coverage will be in effect if you are forced down, injuries result, and rescue time is prolonged. In instances like this, lawyers love terms like "standard practice" and "not in compliance with industry or manufacturer's recommendations".
We need to keep in mind that we hold responsibilites as both pilot and aircraft builder. I don't believe the small placard required on our IP in any way absolves us of these.
 
What does James Clerk Maxwell have to say?

The 121.5 MHz ELT works at the same frequency as VHF comm radios, and very close to VORs. Are any of you installing your comm and VOR antennas in the tailcone?
 
WOW this got sarcastic

I appreciate the passion behind each persons opinion, but "can't we all get along". :D

So WHAT about ELT antenna location? Fact it's a TSO'ed item and comes w/ approved installation instructions, period end of story. Also its likely than an antenna mounted externally on top of the fuselage of a RV will fair a little better in transmitting (right side up or flipped) than say one hidden in the tail intersection fairing. THAT'S SUBJECT TO DEBATE OBVIOUSLY.

I can guarantee a RV plane sitting on its gear, with the ELT antenna mounted, vertical and external on the top of the fuselage will out perform alternative antenna installations (horizontal, hidden, cockpit), for this scenerio. By how much? Who knows. Of course how a RV comes to rest after am off field forced landing is unknown. I show a RV flipped and it still looks like the Vert stab will protect an external antenna. That does not discredit the others and that's the debate, are they good enough.

With that said, it's the installer that "certifies it", and that would be YOU. You get to make the decision. DAR could reject your ELT installation, but hiding antennas inside the tail fairing or cockpit is an accepted practice. That does not mean its OK or not OK, but it's the reality, at least for experimentals.

The cockpit antenna has precedence with EBC ELT's with an integral antenna. A cockpit antenna with a bubble canopy does not seem too bad. An EBC-ELT in a Cessna with high wings and fuselage blocking the antenna is "approved"? I guess if you want to mount the antenna in the cockpit I guess the DAR can say "get an EBC ELT". We all can agree a little milliwatt VHF transmitter cannot get past metal. In my opinion a vertically mounted antenna in the cockpit may not be ideal but should work, but is there an ideal crash?

Of course the ELT takes on more importance if you like to fly over remote rugged regions (mountains, forested, remote unpopulated). Planning on how to survive a crash is important, but avoiding the accident is more important. For you fatalist don't bother.

Survival gear is must flying over remote areas (sleeping bag, water, etc) Also a detailed flight plan (fly exactly) is cheap insurance. In flight positon reports, even VFR is good. Cell phones or $700 PLB's with self contained GPS (personal locator beacon) are great. Australia is allowing PLB's instead of aviation ELTs. Hand held radio is also good. Most airline operators require crews to monitor 121.5. I hear 121.5 ELT's and report them to ATC once every year or 2. 121.5 is not totally useless.

Surviving a crash to die later has happened. Survive the crash and live, only to die from exposure and shock many days later is extra tragic. Before the famous 1972 loss of two congressmen in Alaska, in 1967, a mother and daughter survived a plane crashed in the Sierra Nevada's. They lived 54 days. The 16 year girl kept a diary and heard 59 airliners a day fly over them. Two years later a DC-3 crashed and 3 search planes where lost in the mountains, so California was the first to call for ELT's for aircraft based in state. It was made national law in 1974.

I know of one case personally
. The flight school I CFI'ed for had a C172 go down in Oregon trying to shoot a non-precision approach. After a miss and another attempt, it hit a mountain, only 5 miles from the airport and a mile from a major interstate, which ran near the airport and crash site. The ELT did not go off. The pilot walked away in shock and died a day later from exposure and shock. The passenger expired in the plane at some time. I'm not clear if she died immediately or later. Clearly a "save" was possible if the ELT worked. Even with radar it took too long to find. The crash was violent enough to rip the ELT from its mount. Unknown if pilot tried to recover or manually activate the ELT or if possible. He was only a mile from a super busy freeway! I never flew with the accident pilot, but I knew the CFI who did his recent instrument comp check. She was very upset, as one would imagine. (note: this was before wide spread cell phones and GPS use. I'm sure a cell phone would have saved one or both. Those new PLB's could be a life saver.)

FOR THOSE WHO SAY ELT's NEVER OR RARELY WORK, consider the context. Granted, early ELT's where terriable and rushed into use after two congressman where lost in Alaska. Also, factory planes are NOT an example of GREAT installations. Factory plane where casual with installations instructions and they did not know better. Factory installations and early ELT's where horrible. WE CAN DO BETTER TODAY!

ELT's are like medical/auto insurance, just because you have it does not mean you want a car accident to collect on your policy. However if I'm going to have it (insurance or an ELT) I want it to work. Cheap insurance with lots of deductions does little good.

Do hidden antenna's or cockpit antenna's work? Who knows for sure. Lets find out! Probably will not change minds but would be nice to know.

Here's a picture of a RV flipped after loss of power on takeoff, later repaired and flown. Pilot/instructor walked away with just cuts and scrapes, but had to dig their way out through cracked canopy and marshy ground (hint get egress tools for survivalist, fatalist don't bother.) I penciled in possible antenna locations for grins & giggles. No comment or prefrence implied, JUST a visual to consider for entertainment purposes only. (cockpit, external top fuselage, wng-tip and inside tail intersection fairing :rolleyes:
eltant7cc.jpg

(ELT unit near antenna is critical. You should be able to access ELT unit after the accident of course. The tail location is hard to see, but I think it would have the least transmission range and omni-directionality. The external one is probably best by visual inspection. Who knows for sure?)

Here's my old RV-4 with antenna near roll bar. Likely a terriable RF radiation pattern from the physics of antenna design , but very common RV-4 set up. For the side-by RV's, like Robert Scott, I'm installing similarly but on passenger side.
eltantzg9.th.jpg

It should be better than up against the roll bar as I had in the RV-4. The lack of "ground plane" and obviously blockage from fuselage are negatives, but hey its OK for the EBC. :rolleyes: It's vertical, protected and exposed on top "under glass". That's my story and sticking to it. The RV-7 needs weight as far forward as possible so the ELT unit goes on fwd baggage floor. ELT access and short antenna coax run are pluses. The negative, ELT damage from being exposed in the baggage area, but beefed up mount structure and protective cover should do.

I'm not recommending, just talking folks. Do what ever you like. I do think external top is best. A friend has an antenna analyzer and plan on checking the ELT's radiation pattern. YES you can do test ELT (with in 1st 5min of hr, 3 sweeps).

Have any of you with horizontal antennas in the tail determined how far it transmits and in which directions? Might be good to know? Not saying it will be bad. The Ham radio guys have antenna these spectrum analyzers. Another method would be use DF equip and have someone from a distance in different directions try to "find it", from the ground or airborne. I bet if we knew our installation was really compromised, even under ideal conditions, it might change our decisions? I'm going to test my cockpit antenna installation. If it failed miserably compared to an external one, I'd drill the hole and mount it outside. I'll let you all know. I'll leave you all with this question: HOW GOOD (or bad) ARE OUR SPECIAL ELT INSTALLATIONS?
 
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A test

mgomez said:
The 121.5 MHz ELT works at the same frequency as VHF comm radios, and very close to VORs. Are any of you installing your comm and VOR antennas in the tailcone?


They do get mounted routinely in the wing tips.

OK, here is what I did. During the first 5 minutes of this past hour I was able to pick up the ELT with my inside fuselage antenna.

Test so far. Everything hooked up, baggage compartment cover installed. Airplane in the basement. I got my handheld, walked about 300 yards away, line of sight, trusty cell phone in hand and had Elaine activate the ELT using the remote panel mount. I picked up the signal loud, even through the fuselage, den wall and garage doors. Seems quite good to me. The only way I can test a longer line of sight is to stick the tailcone in line with the garage, open the double den doors and garage doors. This would give me 1/3 mile line of sight. Any use in that test?

I know this is so shade tree mechanic it is probably useless, but does it prove anything, or is it totally useless? I am asking that question seriously. I know I don't have fancy measuring equipment and double throw me down wizz bang graphs and charts, but I did pick up the signal quite good.
 
Yes, but FIBERGLASS wingtips!

Fiberglass, being an insulator is more or less transparent to VHF. So wingtip antennas work well.

Aluminum, being a very good conductor, reflects it...some of it leaks out, and that's why you were able to pick it up with your handheld.

It's a matter of signal strength. What your test didn't tell you is how close to NOT receiving anything you were...that's what the "fancy test equipment" does.

It worked at 300 yards (about 1/5 of a mile). If the signal was JUST enough, then to go 1 mile, you'd need 25 x more power. To go 10 miles, you'd need 2500 x more power...etc.
 
mgomez said:
It's a matter of signal strength. What your test didn't tell you is how close to NOT receiving anything you were...that's what the "fancy test equipment" does.

It worked at 300 yards (about 1/5 of a mile). If the signal was JUST enough, then to go 1 mile, you'd need 25 x more power. To go 10 miles, you'd need 2500 x more power...etc.

Martin, since I don't have any "fancy test equipment" (double throw me down equipment:), turning it on and seeing if, in fact, it would transmit through alum. was my only means to test. It will, no doubt, be less signal strength than out in the open, but it does transmit.........and fairly well, in my very, very uneducated mind and even more poorly standardized testing procedure. To furthur expound, I walked it off; I ended up around 280 yards+-, when I lost the signal. To get that far, the signal had to go through the fuselage, and through my dang basement wall. My "experiment" was like a Myth Busters show, it only proved one thing but didn't address all the what if's, why fors and even thoughs. My cell phone signal however, was rock solid strong (tongue in cheek, come on guys laugh a little).
 
Testing

If there is any interest out there, I would be happy to conduct a better test using a practice ELT beacon.

It transmits on 121.775 so the frequency difference is minimul. We are currently waiting on a new battery for it so when it's in, I can pull my plane from the hanger and mount the antenna in different locations in and on the plane. From different points 1-2 miles away and then in closer, I can get both signal strength and direction from the beacon. We have an older DF unit and a new one that just came out this year. The older crystal controlled one is a Ltronics LH Series Little L-Per which is the unit that 95%+ CAP units use to DF signals. This is the unit that you see the teams riding around at Oshkosh using. The new unit is much better and much more acurate also called the Little L-Per. You can check out that unit at www.ltronics.com. They also have two great articles on DFing at www.ltronics.com/dft.htm. They highlight some of the problems encountered while searching. Also check out how an antenna is covered up in aluminum foil to stop the signal from radiating if it cannot be deactivated.


My experience is that from a distance, if the signal can be recieved, you can generally DF to the area but when you get closer in, the signal bounces off of everything and is much more difficult to nail down.

So, if enough people are interested speak up. I'm happy to do this.
 
No antenna....

BlackRV7 said:
They do get mounted routinely in the wing tips.

OK, here is what I did. During the first 5 minutes of this past hour I was able to pick up the ELT with my inside fuselage antenna.

Test so far. Everything hooked up, baggage compartment cover installed. Airplane in the basement. I got my handheld, walked about 300 yards away, line of sight, trusty cell phone in hand and had Elaine activate the ELT using the remote panel mount. I picked up the signal loud, even through the fuselage, den wall and garage doors. Seems quite good to me. The only way I can test a longer line of sight is to stick the tailcone in line with the garage, open the double den doors and garage doors. This would give me 1/3 mile line of sight. Any use in that test?

I know this is so shade tree mechanic it is probably useless, but does it prove anything, or is it totally useless? I am asking that question seriously. I know I don't have fancy measuring equipment and double throw me down wizz bang graphs and charts, but I did pick up the signal quite good.

Dana ... try repeating the test with the antenna disconnected.

Since these are emergency beacons, I bet they are designed to emit radiation directly from the unit. It would be an easy test for you to repeat.

I can't find a copy of the TSO 91a on line, so I can't find their design specification... :(

gil in Tucson
 
Update - added EBC ELT data...

az_gila said:
Hi Dana.... these installation instructions may not say "outside", but they do say the antenna has to be within 15 degrees of vertical (page 23)

http://www.artex.net/documents/570-1015RevG.pdf

Ameri-King is a bit more explicit, and states that the antenna must be external to meet the requirements of TSO 91a and FAR 91.52 (page 9). They also give a vertical requirement of 20 degrees to vertical (in normal flight attitude for you acro guys... :) ....)

http://www.ameri-king.com/pdf/9.1.22.pdf

ACK is a bit different, allowing up to 45 degrees from vertical, but only allowing internal antenna mounting in a composite or fabric plane. It does actually say externally for metallic aeroplanes. (page 4)

http://www.ackavionics.com/images/Model_e-01_ELT_Manual.pdf

Most of the pictures so far don't come close to these manufacturer's instructions, which are required as part of the "approved" data that our ELTs must meet per the FARs... :rolleyes:

Anyone got any other approved installation manuals that say something different?

gil in Tucson

PS ... I like the cell phone ON idea.... I usually do it just because I forget to switch it off when I put it in my flight bag... :)

UPDATE ... the only common ELT I did not link to was the EBC 502 that is cockpit mounted... so to add to the previous data.

The EBC 502 FAA approved installation manual is here...

http://www.emergencybeaconcorp.com/instruction_manuals/ebc502.pdf

It states the the antenna must be vertical with as much exposed to the window as possible. The window must be 12 H by 13 W minimum. The antenna must be at least 1 inch away from any metal part.

It would appear that the "curve it over and attach it to the roll bar" method is not really approved...

I never did hear from any DARs..... :(

gil in Tucson
 
az_gila said:
Dana ... try repeating the test with the antenna disconnected.

Since these are emergency beacons, I bet they are designed to emit radiation directly from the unit. It would be an easy test for you to repeat.

I can't find a copy of the TSO 91a on line, so I can't find their design specification... :(

gil in Tucson

Deal, I'll do it in the morning. I am not trying any "I told you so" here, just a real world test. I'm game.
 
Warning

Be aware, it's usually a no-no to enable any transmitter without an antenna. It may be an expensive experiment. It's kind of like running an engine without a prop.
 
Like Tom says, transmitters are designed to run with the "load" of an antenna. Some transmitters are transformer coupled as a protective device. Smaller, simpler transmitters like ELTs usually are direct coupled. Without the antenna load, the transmitter can go to max power burning up the output stage. Be careful.
 
Mel said:
Like Tom says, transmitters are designed to run with the "load" of an antenna. Some transmitters are transformer coupled as a protective device. Smaller, simpler transmitters like ELTs usually are direct coupled. Without the antenna load, the transmitter can go to max power burning up the output stage. Be careful.

Mel and Tom, I thought about it last night and it would seem the ELT manufacturers would think to protect the ELT with the reasoning being the antenna could easily be stripped off the fuselage during an event. This would enable the equipment to still be used remotely.

With that in mind, I did disconnnetted the antenna and activated the ELT during the first 5 minutes. It did transmit through the fuselage skin. However, it was degraded.

With this said, the optimal position for the antenna has got to be on the outside of the fuselage; that is just obvious. With that said, I am satisfied with my install. Certainly other opinions are present, and that is perfectly fine with me.

Getting close and really, really liken it!!!
 
That what the TSO is for....

Mel said:
Like Tom says, transmitters are designed to run with the "load" of an antenna. Some transmitters are transformer coupled as a protective device. Smaller, simpler transmitters like ELTs usually are direct coupled. Without the antenna load, the transmitter can go to max power burning up the output stage. Be careful.

Mel... I would hope the TSO specifies that the transmitter can operate into a direct short or a complete open circuit on the antenna.

It's not much of an emergency device if it can't do that.... think crumpled up plane, inverted.... antenna laying on the ground....

Does anyone have a copy of the TSO C 91a? I retired last week and can't get a copy form work any more... :(

gil in Tucson
 
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