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

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    mvivion's Avatar
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    406 vs 121.5 ELT (from Another crash in AK thread)

    A couple of folks suggested bringing this topic over on its own, rather than continue to discuss on the accident thread. I am in agreement with that. Let's try to keep the ELT discussion over here.

    This is long, but I think it contains important information on how these units function.

    I just got off the phone with a fellow named Mick, who works for Cobham, Inc, the manufacturer of Artex ELTs. He was VERY informative and clarified a LOT of things for me, so here's his information:

    1) Much of the information on how an ELT signal goes through the "system" that's posted on this site is WRONG. Here's the way it works, from an ELT designer:

    The Beacon activates, and transmits a data burst every 50 seconds on a carrier wave, with an encoded data packet, into the atmosphere. That signal is picked up (assuming the antenna isn't broken, underwater, or????)within ten minutes by EITHER a polar orbiting satellite OR a geosynchronous satellite, and is transmitted down to a Local User Terminal (NOT RCC), of which there are ABOUT 10 to 12 world-wide. There are two in the US.

    IF the initial data burst provides sufficient information and signal strength (strong enough, and maybe received by more than one satellite) the signal is passed along to the Rescue Coordination Center with jurisdiction over the LOCATION of the beacon.

    If the signal isn't strong enough, or the triangulation isn't good enough for a position solution (not uncommon), the signal is passed to the country of origin for the beacon registration (NOT necessarily where the beacon hit came from in other words).

    This goes to the MCC (Mission Control Center, NOT RCC) which decodes the data, searches the database, finds the contact info for the owner and makes the calls. THEN, if it is determined to be a REAL emergency, the information is transmitted to the RCC with jurisdiction and a SAR is initiated. By this time, HOPEFULLY, a better location will have developed, based on multiple satellite hits. Point is, if there is a "decent" general location initially, the system then knows which RCC to notify.

    Note that, as I posted earlier, by the time a SAR crew is actually airborne or ready to launch, ANOTHER polar orbiting satellite will have passed, and refined the location better. So, by the time the CG/ANG/CAP/Troopers head out to actually search, the position of the ELT signal will have been refined more than the initial triangulation, BUT the system, without a GPS enabled ELT DOES NOT provide precisely accurate position location.

    Finally, as the SAR element goes into action, they MUST search using the 121.5 signal, since the 406 signal transmits in momentary bursts every 50 seconds. There is NO way that you can DF on a 406 signal, which is why every 406 ELT and PLB and EPIRB has on board a 121.5 beacon as well.

    Other points that Mick provided information on:

    1) As I suspected, the new 406 ELTs are using the same G-switches as the old 121.5 beacons. So, the reliability of activation by switch hasn't and will not improve UNTIL the manufacturers get a solid state G-switch approved. Mick pointed out that this is a HUGE project, and adding a better switch will increase the cost of the units a LOT due to certification costs. Nevertheless, at present, the same switches are in use.

    2) BUT, Mick then informed me that historically, 40 % of the ELTs that failed to activate (121.5 and 406) were torn from their mount in the accident sequence. This is apparently what happened in the Otter accident near Dillingham a few weeks ago, and by the way, Mick was the technician who disassembled and examined that ELT yesterday. In that case, the antenna cable was broken, so no signal was transmitted.

    SOOOO, properly mounted, the current crop of ELTs would work 40 % more of the time (presumably) IF they were properly mounted. THAT is huge, and we should ALL give some consideration to that.

    3) In the remaining cases where an ELT didn't activate, it turns out that the switches haven't been exercised annually, as part of the annual inspection of the ELT. This is recommended by the manufacturers, by the way. Never heard of this myself BUT..... Mick said that the problem is that the switch is a steel ball inside a cylinder, with springs holding it in position. If it's not exercised, it can seize up (my description, not his) or in any case, won't work. He says ALL ELT G-Switches should be exercised EVERY year. Write that one down, folks.

    4) As I noted on the other thread, I spoke with RCC at Elmendorf, and, as I suspected, they gave me some incorrect information. In fact, the information that Beavercub got from RCC Coast Guard is also wrong in several points. Bear in mind that these are simply the folks who get the message and they aren't necessarily knowledgeable of the system's fine points.

    Mick is VERY informed of the finer points of the system, since he designs ELTs to alert the system.

    5) Advantages of the 406 beacons:

    --They emit a MUCH stronger signal, since this is a digital signal and it goes out in bursts, as opposed to continuous as in the case of the 121.5 beacon.

    --The 406 system triangulates similarly to the 121.5 beacons, but uses TWO layers of satellite systems instead of just one: a geosynchronous layer of satellites, AND a set of polar orbiting. In the days of 121.5 monitoring, the polar orbiting satellites monitored the 121.5 freq, and the geosynchronous monitored the 406 freq. So, NOW, the 406 has better satellite coverage, which will result in faster acquisition of a better, more accurate position, and often does.

    --Nevertheless, initial position location for a 406 without a GPS interface is still 8 to 10 square kilometers at best. The accuracy for the 121.5 was 30 to 50 square kilometers. That's a huge advantage, no doubt, BUT the 406 CANNOT pinpoint a precise location of a beacon, regardless of the number of satellite hits .

    --Some of the 406 ELTs are capable of connecting to a panel mounted GPS. At present, NO ELTs are capable of interfacing with a PORTABLE GPS. Cobham (Artex) is a couple weeks from releasing a NEW ELT that DOES offer a link to a portable GPS, via an NMEA connection port. He didn't give me a price, but it's not going to be cheap. The model number will be the Artex ME-183. I'll be looking at that one.

    --As I suspected, ALL EPIRBS (the vessel version of the aircraft ELT) have onboard GPS units, which is how the 406 system can immediately and precisely locate a vessel that's sinking. Again, without the GPS interface, the initial 406 signal is still sort of vague, BUT it can get rescuers into close enough range so that they can home on the 121.5 signal.

    I asked Mick why the ELT folks don't install GPS in ALL ELTs. His answer was that these boxes have to meet certification standards for ELT's, Comm devices, GPS, Antennas, AND mounting, etc. The GPS standards are especially difficult to meet, and so-----

    both Kannad and Artex (the two largest manufacturers of ELTs in the world) are working on such units, but again, due to certification costs, they will be MUCH more expensive than the basic units. On the other hand, building such capability into an EPIRB for vessel use requires minimal certification.

    I asked him about mounting protocols, and he noted that many manufacturers have mounting protocols for current production aircraft, and you can use that, or the mounting criteria are spelled out in the instructions. By the way, Mick is also an A & P mechanic, with 15 years experience in that field.

    I also asked whether the velcro mounting straps used to secure both the Kannad and the Artex units are strong enough to meet the mounting standards. He said, essentially, that you can't believe how strong those velcro straps really are--they far exceed the 100 G standard.

    Whew!!!! That was a looooong phone call, and very informative.

    I'm now getting closer to the information that I've been looking for.

    Seems like we can IMPROVE our chances of an ELT working by:

    1) Ensure the mounting is STRONG
    2) Exercise the G-Switch annually, by removing the unit, and shaking it to activate. Doesn't activate?? Get it fixed.
    3) And, there are distinct advantages to the 406 beacons, which I recognized to start. This discussion, however has clarified some advantages that I wasn't aware of, AND clarified how we can improve the odds of the things activating in an accident.

    I'm still going to wait to see the cost of that GPS enabled unit from Artex, though.....

    And, by the way, from the SAR website:

    Alaska Search and Rescue
    The Alaska State Troopers, Dept. of Public Safety, have primary responsibility for civilian search and rescue in Alaska. Any search and rescue emergency should be reported to the nearest Trooper Detachment, Village Public Safety Officer, or to Trooper Dispatch in Anchorage (428-7200).

    This is INFORMATION, not hearsay. It's not from "a neighbor", "someone I knew once", or.....as I said, the sergeant I spoke with at RCC Elmendorf yesterday had a LOT of this information wrong when I spoke to him.

    MTV

  2. #2
    Clay Hammond's Avatar
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    Thats great info Mike. Thank you for calling and getting the clarification.
    Fatum Est Venator

    http://about.me/clayhammond

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    Gordon Misch's Avatar
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    Thanks, Mike - that took some considerable effort to compile.
    Gordon

    N4328M
    My SPOT: tinyurl.com/N4328M (case sensitive)

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    www.SkupTech.com mike mcs repair's Avatar
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    Re: 406 vs 121.5 ELT (from Another crash in AK thread)

    Quote Originally Posted by mvivion
    3) In the remaining cases where an ELT didn't activate, it turns out that the switches haven't been exercised annually, as part of the annual inspection of the ELT. This is recommended by the manufacturers, by the way. Never heard of this myself BUT..... Mick said that the problem is that the switch is a steel ball inside a cylinder, with springs holding it in position. If it's not exercised, it can seize up (my description, not his) or in any case, won't work. He says ALL ELT G-Switches should be exercised EVERY year. Write that one down, folks.

    MTV
    great info thanks, we need more threads like this!

    actually you have been required to test the G switch each inspection for a long time...
    and they make us log "elt inspectected an function checked IAW FAR 91.207......." which is kinda BS... since you really don't log every other FAR you are to comply with.....


    Sec. 91.207

    Emergency locator transmitters.

    (a) Except as provided in paragraphs (e) and (f) of this section, no person may operate a U.S.-registered civil airplane unless--
    (1) There is attached to the airplane an approved automatic type emergency locator transmitter that is in operable condition for the following operations, except that after June 21, 1995, an emergency locator transmitter that meets the requirements of TSO-C91 may not be used for new installations:
    (i) Those operations governed by the supplemental air carrier and commercial operator rules of parts 121 and 125;
    (ii) Charter flights governed by the domestic and flag air carrier rules of part 121 of this chapter; and
    (iii) Operations governed by part 135 of this chapter; or
    (2) For operations other than those specified in paragraph (a)(1) of this section, there must be attached to the airplane an approved personal type or an approved automatic type emergency locator transmitter that is in operable condition, except that after June 21, 1995, an emergency locator transmitter that meets the requirements of TSO-C91 may not be used for new installations.
    (b) Each emergency locator transmitter required by paragraph (a) of this section must be attached to the airplane in such a manner that the probability of damage to the transmitter in the event of crash impact is minimized. Fixed and deployable automatic type transmitters must be attached to the airplane as far aft as practicable.
    (c) Batteries used in the emergency locator transmitters required by paragraphs (a) and (b) of this section must be replaced (or recharged, if the batteries are rechargeable)--
    (1) When the transmitter has been in use for more than 1 cumulative hour; or
    (2) When 50 percent of their useful life (or, for rechargeable batteries, 50 percent of their useful life of charge) has expired, as established by the transmitter manufacturer under its approval.
    The new expiration date for replacing (or recharging) the battery must be legibly marked on the outside of the transmitter and entered in the aircraft maintenance record. Paragraph (c)(2) of this section does not apply to batteries (such as water-activated batteries) that are essentially unaffected during probable storage intervals.
    (d) Each emergency locator transmitter required by paragraph (a) of this section must be inspected within 12 calendar months after the last inspection for--
    (1) Proper installation;
    (2) Battery corrosion;
    (3) Operation of the controls and crash sensor; and
    (4) The presence of a sufficient signal radiated from its antenna.
    (e) Notwithstanding paragraph (a) of this section, a person may--
    (1) Ferry a newly acquired airplane from the place where possession of it was taken to a place where the emergency locator transmitter is to be installed; and
    (2) Ferry an airplane with an inoperative emergency locator transmitter from a place where repairs or replacements cannot be made to a place where they can be made.
    No person other than required crewmembers may be carried aboard an airplane being ferried under paragraph (e) of this section.
    (f) Paragraph (a) of this section does not apply to--
    [ (1) Before January 1, 2004, turbojet-powered aircraft; ]
    (2) Aircraft while engaged in scheduled flights by scheduled air carriers;
    (3) Aircraft while engaged in training operations conducted entirely within a 50-nautical mile radius of the airport from which such local flight operations began;
    (4) Aircraft while engaged in flight operations incident to design and testing;
    (5) New aircraft while engaged in flight operations incident to their manufacture, preparation, and delivery;
    (6) Aircraft while engaged in flight operations incident to the aerial application of chemicals and other substances for agricultural purposes;
    (7) Aircraft certificated by the Administrator for research and development purposes;
    ( Aircraft while used for showing compliance with regulations, crew training, exhibition, air racing, or market surveys;
    (9) Aircraft equipped to carry not more than one person; and
    (10) An aircraft during any period for which the transmitter has been temporarily removed for inspection, repair, modification, or replacement, subject to the following:
    (i) No person may operate the aircraft unless the aircraft records contain an entry which includes the date of initial removal, the make, model, serial number, and reason for removing the transmitter, and a placard located in view of the pilot to show "ELT not installed."
    (ii) No person may operate the aircraft more than 90 days after the ELT is initially removed from the aircraft; and
    [(11) On and after January 1, 2004, aircraft with a maximum payload capacity of more than 18,000 pounds when used in air transportation.]

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    very comforting to know they only work 40% of the time at best

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    mvivion's Avatar
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    Mike,

    No, that is not correct.

    His point was that in 40 % of the cases where the ELT did NOT function, it was a result of the ELT MOUNTING failing, NOT because the switch didn't work.

    That's a little different. And, his point was that better mounting integrity could substantially reduce this failure rate, new unit or old.

    On top of that, if we regularly exercised the G-Switches, we could reduce the failure rate further.

    MTV

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    very comforting to know they only work 40% of the time at best

    Which is why it should be just one part of your overall system: filed flight plan, fixed ELT, portable 406 PLB, sat phone and SPOT/Sidertracks type tracking.

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    just wondering then, what's the overall failure rate, regardless of reason?

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    spinner2's Avatar
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    Thanks Mike for doing the homework. I'll bet that was about as much research as writing a magazine article.

    I have an Artex ME406 in my Cessna and the same in the now-sold Cub. I feel comfortable knowing that if I wreck a signal is going up to the satellites. With 121.5 that isn't happening. So in the scenario where you're alive but unable to activate a PLB or make a phone call the signal is still being heard by a satellite. And if you're dead is saves searchers much valuable time and risk.

    I have 121.5 DF equipment in my Cessna and used it again on a search this summer. My observer and I didn't find it, a Homeland Security helicopter did on the third day, but on our first evening looking we heard a short burst of 121.5 squeal. To this day we don't know where it came from but we wasted time looking in an area where the plane was not found.

    The easier it is for searchers to narrow the search area the better. On this search the weather was good but what about when it isn't? Using the best technology available makes the best sense to me for both the lost and the searchers.

    And as George said, make it just a part of the tool box.
    "They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety." Benjamin Franklin

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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by mvivion
    Mike,

    No, that is not correct.

    His point was that in 40 % of the cases where the ELT did NOT function, it was a result of the ELT MOUNTING failing, NOT because the switch didn't work.

    That's a little different. And, his point was that better mounting integrity could substantially reduce this failure rate, new unit or old.

    On top of that, if we regularly exercised the G-Switches, we could reduce the failure rate further.

    MTV
    You failed to read my post then.....

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    mvivion's Avatar
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    OK, Mike, how about POINTING OUT what I missed in YOUR lenghty post? I DID read it, and I don't see what's inconsistent with what I posted.

    What's your point, por favor?

    MTV

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    sharp's Avatar
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    I think Mike's point is that they are excercised annually
    You are inferring they are not excercised

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

    Quote Originally Posted by mvivion
    --Some of the 406 ELTs are capable of connecting to a panel mounted GPS. At present, NO ELTs are capable of interfacing with a PORTABLE GPS. Cobham (Artex) is a couple weeks from releasing a NEW ELT that DOES offer a link to a portable GPS, via an NMEA connection port. He didn't give me a price, but it's not going to be cheap. The model number will be the Artex ME-183. I'll be looking at that one.
    The ACK E-04 understands both Garmin Aviation format and NMEA format GPS position sentences. It also has been close to release... for a long time! Updates here: http://www.ackavionics.com/406%20Page.html. Its announced price is cheap, comparitively.

    --Paul

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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by sharp
    I think Mike's point is that they are excercised annually
    You are inferring they are not excerised
    exactly, and he says he doesn't, so i guess his plane is not airworthy then

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    mvivion's Avatar
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    Mike,

    THanks for explaining your point. I did read your post, which was the regulation. What I said was that I didn't realize they were supposed to be exercised annually. That doesn't mean mine wasn't, since I trust my maintenance to a professional AMT....

    I said several times here that a big part of my purpose here was to LEARN.

    I'm learning. I will, however chat with my mechanic about this, just to be certain.

    In any case, Mick noted that a LOT of the units they see have obviously NOT been exercised routinely, based on the fact that the switch is stuck.

    Also, note in the same part of that reg that the IA is required to verify the mounting integrity of the ELT as well.

    Now, go back to that part about 40 % of the failures being the result of improper installation....

    MTV

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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by mvivion
    Mike,

    THanks for explaining your point. I did read your post, which was the regulation. What I said was that I didn't realize they were supposed to be exercised annually. That doesn't mean mine wasn't, since I trust my maintenance to a professional AMT....

    I said several times here that a big part of my purpose here was to LEARN.

    I'm learning. I will, however chat with my mechanic about this, just to be certain.

    In any case, Mick noted that a LOT of the units they see have obviously NOT been exercised routinely, based on the fact that the switch is stuck.

    Also, note in the same part of that reg that the IA is required to verify the mounting integrity of the ELT as well.

    Now, go back to that part about 40 % of the failures being the result of improper installation....

    MTV
    just enjoying picking on you while I had your feathers ruffled up so pretty

    this will be a good thread as I am also interested what failed and what I can do to prevent it ...

    I am also about to be forced to bail on the ACK ELT and go with another brand in the coming days,

    what is the best, that will tie to the aircraft GPS data, I thought all did, but have not researched it...

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    Darrel Starr's Avatar
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    During the rebuild of our Super Cub, N18SY, we got 51 Form 337s approved. One of them concerned mounting the ELT. We first took a picture of the ELT & mounting and sent that into the MN FSDO -- REJECT! I called and asked why. The Inspector called my attention to AC 43.13 and that I had to prove that the mounting would pass the "G" forces required. He suggested that I weigh the ELT with batteries then multiply it by the "G" force required, which as I recall was 9 in the forward direction. Then he said "Doesn't Bob Eckstein ( the IA) have a spring scale? So we got out the spring scale and made the tests, took pictures showing the force being pulled and added the pictures to the resubmission of the 337 - PASSED! I thought at the time that this was a bit over the top but given the Otter crash, now it all looks prudent. This approval was in 2004 so things might have changed since then.
    Darrel




    This is the sheet attached to the 337:
    Liquidating Excess Funds Through Aviation



  18. #18
    Louis's Avatar
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    Is the buzzer in the dash explosion proof ? I just read that it is not waterproof, i wonder if it is a piezo with a spark.

    Louis

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    mvivion's Avatar
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    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.

    I believe ACK has also been "about to hit the streets with one" for something like a year.

    One interesting thing that Mick told me was that the AVIONICS certification standards required by the FAA are MUCH more stringent than the structural certification standards. Go figure.

    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.

    I'm beginning to think that my best bet is going to be a basic unit and my PLB in my pocket.

    MTV

  20. #20
    this would be a title NimpoCub's Avatar
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    POINTER has had an ELT with built-in GPS & powered by the airplane 12V for some time now.

    Like I said in the (other) thread, I was told by an ELT exec, and a SAR exec that the 406 signal is the important one, and the final homing in on you is done with the 121 signal. There is much more involved, yes, but that's the basic deal.

    The only advantage of the GPS that I see is if you burn/submerge there is a better chance your location has been sent. As others have said, the ELT is just one component of your "easter egg package".
    Nimpo Lake Logan... boonie SuperCubber
    200mi (300km) from nearest stoplight... just right! - "Que hesitatus fornicatus est"

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    375handh's Avatar
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    So, does anyone know anything about Emerging Lifesaving Technologies ELT406GPS? It appears to be a straightforward ELT with built in GPS, that Aircraft Spruce, and many others, sells for about $1,360.
    Ineptocracy - A system of government where the least capable to lead are elected by the least capable of producing and where the members of society least likely to sustain themselves or succeed are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers.

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    91.207 is pilot responsibility. Mike, good research! From my conversations and reading the Guberment didn't do a very good job on this Satellites shutdown and there are way to many people giving out wrong info. Then there are the ones that can't remember what it was like before the Satellites where used
    Tim

  23. #23
    mvivion's Avatar
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    Nimpo,

    From Pointer's web site: "Our approval program is in process.
    We have completed COSPAS/SARSAT testing.
    FAA testing has begun."

    In other words, the Pointer 406 unit is not yet approved, and I could only find a brief mention of an option for GPS.

    375,

    I haven't heard of or seen that one. I called Aircraft Spruce and inquired about it. It is NOT currently approved. Why they list it in their catalog, and on Emerging Lifesaving Technologies web site the way the do is a little misleading.

    The sales person at ACS said "May be available in mid October".

    So far, that guy Mick has provided pretty accurate information. He said that meeting the TSO standards is a bitch, and apparently, that is oh, so true.

    MTV

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    www.SkupTech.com mike mcs repair's Avatar
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    so..

    of the 40% torn from mount does that mean the supplied elt mount failed, or bolts ripped through it, or what it was mounted to failed, could use a doubler? or??

  25. #25
    this would be a title NimpoCub's Avatar
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    Here's another interesting tidbit...
    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.

    So, not only am I changing my 'plan' but wanted to let y'all know that if you know someone who has an antenna mounted inside the fuse, that it won't work. I'm sure thankful I have good adult supervision around here!
    Nimpo Lake Logan... boonie SuperCubber
    200mi (300km) from nearest stoplight... just right! - "Que hesitatus fornicatus est"

  26. #26
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by NimpoCub
    Here's another interesting tidbit...
    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.

    So, not only am I changing my 'plan' but wanted to let y'all know that if you know someone who has an antenna mounted inside the fuse, that it won't work. I'm sure thankful I have good adult supervision around here!
    ya its here somewhere...

    i still debate that with myself... ack says ok, others say no go.....

  27. #27
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by NimpoCub
    Here's another interesting tidbit...
    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.

    So, not only am I changing my 'plan' but wanted to let y'all know that if you know someone who has an antenna mounted inside the fuse, that it won't work. I'm sure thankful I have good adult supervision around here!
    ya its here somewhere...

    i still debate that with myself... ack says ok, others say no go.....

  28. #28

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    Quote Originally Posted by NimpoCub
    He said that's effectively letting 1/8th of the RF out.
    My math is a little fuzzy but 1/8 is still better than 0 isn't it?
    Tim

  29. #29
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    Mike,

    Thanks for the research. I still think a good sat phone or Spot Messenger is your friend. I don't own either one of those but may in the near future. Like I said, a good elt only keeps the relatives and friends happy so they can fight over what you left on this earth. If one is lucky enough to survive a crash a sat phone or Spot may be your best answer. They will both let people know you need help.

    One last comment. Local law enforcement has jurisdiction over aircraft crashes in their jurisdiction. Every state varies on what local law enforcement means. Some states take that as the county sheriff and others let the State Troopers, Department of Public Safety, State Aeronautics take care of it. But then again I was an RCC sergeant and I probably don't know shiz.

  30. #30
    mvivion's Avatar
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    Nimpo,

    Mick specifically stated that 406 antennas should NOT be mounted inside fabric covered aircraft due to signal attenuation. It wouldn't make much sense to spend this much money and then impair the signal......

    MTV

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    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.

  32. #32
    www.SkupTech.com mike mcs repair's Avatar
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    from section 3 elt 406 install

    http://www.ackavionics.com/pdf/E-04_...INGLE_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????

  33. #33
    this would be a title NimpoCub's Avatar
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    Quote Originally Posted by mit greb
    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...
    Quote Originally Posted by MTV
    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.
    Nimpo Lake Logan... boonie SuperCubber
    200mi (300km) from nearest stoplight... just right! - "Que hesitatus fornicatus est"

  34. #34
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    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
    If it looks smooth...it might be

    If it looks rough...it is!!

  35. #35
    www.SkupTech.com mike mcs repair's Avatar
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    Moved from other thread.....
    Quote Originally Posted by Gary Fields
    ........

    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?

  36. #36
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    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

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    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

  38. #38
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    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.
    "They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety." Benjamin Franklin

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    Quote Originally Posted by mvivion
    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.

  40. #40
    StewartB
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    $225 at Aircraft Spruce.
    http://www.aircraftspruce.com/catalo...vinterface.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

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