GDL-82 vs SkyBeacon

Discussion in 'Flight Following' started by Nmm347, Mar 10, 2019.

  1. Nmm347

    Nmm347 Filing Flight Plan

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    I’ve been comparing the Garmin GDL-82 to the SkyBeacon and like them both for my application. The one thing I cannot figure out is the difference between the two in relation to how they “monitor” your transmitter. For reference the GDL-82 Manual says this in para 2-1


    “This unit transmits ownship Automatic Dependent Surveillance-Broadcast (ADS-B) data through the UAT data link. It interrogates connected transponders for Mode 3/A squawk code, IDENT status, and pressure altitude. The GDL 82 with GPS/SBAS includes an internal GPS/SBAS receiver. This receiver allows the unit to function as its own position source for the ADS-B Out message, when an approved position source interface is not installed.”


    And the SkyBeacon manual says this in para 6.3


    “skyBeacon utilizes uAvionix’s Power Transcoder to ensure proper synchronization of data elements between Secondary Surveillance Radar (SSR) replies and ADS-B transmissions. These elements include Mode A squawk and IDENT status. In remote areas where you may not be interrogated by SSR, these data elements may at times be unavailable. The Power Transcoder additionally serves to provide Continuous CalibrationTM data to the altitude encoder.”


    So my question is what’s the difference? The GDL-82 says it interrogates the transponder and the SkyBeacon says it monitors. Does this mean if you were to take off from an airport that is out of range from secondary surveillance radar and your entire flight stayed outside or under the SSR range meaning your transponder would never be interrogated would the SkyBeacon never receive the transponder Mode A squawk and IDENT status? Would this affect your ADS-B out broadcast? In this same scenario does this mean since the GDL-82 interrogates the transponder it would receive this info?


    If I have this correct the final question would be does any of this even matter for VFR US flights? Just trying to fully understand the differences in the two units here.
     
  2. PPC1052

    PPC1052 En-Route

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    Are you Garmin's patent lawyer trolling us?
     
  3. idahoflier

    idahoflier Line Up and Wait

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    I would just ask uAvionix. I found them to be friendly and forthcoming answering all my questions at OSH. I don't think it really matters though as they wouldn't have been successful with the FAA if it really mattered...
     
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  4. Mtns2Skies

    Mtns2Skies Super Moderator Management Council Member PoA Supporter

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    This answer isn't directly related to your question but...
    I have the GDL82 because:
    1. I got tired of Uavionix' unfulfilled promises about when their product would be available. Particularly since I was targeting a date for my ADSB rebate.
    2. I have all other Garmin equipment that works very, VERY well.
    3. The GDL82 doesn't require your lights to be on to work
    4. The GDL82 is a couple hundred dollars cheaper to buy (but longer to install, took me about 4 hours to do)
    5. The GDL82 has position outputs if you ever need to connect it to an ELT or a G5 etc.
    6. The GDL82 came with a free Waas GPS antenna that I can use in the future if I ever upgrade and get a GTN650.
     
  5. Nmm347

    Nmm347 Filing Flight Plan

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    Boy I wish, I bet they make a pretty penny. Just trying to decide the best option for my plane. I’m leaning towards the SkyBeacon but want to make sure I do my research. I’ve called and spoke with uAvonix before and they were super helpful. At the time I was still researching and didn’t have the above question. Wish I did, took me 30 minutes of being on hold to get through to a tech. Thats why I tried asking the question here first. I’m surprised no one has an answer.

    Thanks for the reply Mtns2Skies, all good points for the GDL-82 but not quite enough for me to pull the trigger. The lights on thing doesn’t bother me and I actually lean towards the SkyBeacon because it has an led light and strobe. Something I currently don’t have but want. Where did you find it cheaper than the SkyBeacon? The places I’ve looked it’s been the same price. My google foo may be weak.
     
  6. 3 in the green

    3 in the green Line Up and Wait

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    I'll be following this thread. My 170 has a KT-78 and I just started researching solutions...looking at the GDL 82 and/or the Skybeacon (when it's ready...).
     
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  7. Mtns2Skies

    Mtns2Skies Super Moderator Management Council Member PoA Supporter

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    I don't think the GDL82 can be advertised cheaply due to corporate things, but if you add it to your cart on aircraft spruce it's $1695. (Add to cart for current pricing)
    https://www.aircraftspruce.com/catalog/avpages/garmingdl82gps11-15319.php

    Now I also was looking at the tailbeacon which is about 2k+ (and STILL not available) since I have recently upgraded my NAV lights.
     
  8. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    There likely isn't anyone with an answer, because you'd have needed to be involved in the engineering of BOTH devices to have an answer, and generally avionics engineers don't hang out on pilot forums and talk about work, because that often gets them in trouble.

    That said, I'll take a stab at an educated guess if that works for you - I have a degree in electrical engineering and I'm kind of a geek about avionics, but I have not worked as an engineer for an avionics manufacturer, FWIW.

    The GDL 82 is wired inline between your transponder and its antenna, so it's relatively easy for them to decode what your transponder is trying to send out.

    From what I know of the SkyBeacon, this "power transcoder" is looking at tiny pulses on the nav light wire it's using for power - I think they're essentially treating the power wire as an antenna as well, since I don't think anything the transponder does in terms of sending the code is going to fluctuate its power draw enough to be detectable once it gets past the transponder power supply, the voltage regulator, and any other parts of the electrical system in between.

    It seems to me that the GDL 82's method is much more robust. I'd love to have an engineer from UAvionix come here and explain why I'm wrong, or a Garmin engineer tell me why I'm right, but I don't think that's going to happen.
     
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  9. hindsight2020

    hindsight2020 En-Route

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    I mean at this point, it's pretty much down to the skybeacon, if the supposed lack of avionics capacity people quote on here is true, vis a vis the deadline. I'm still holding out I may get rid of this thing before the deadline, but if I don't I'm pretty much committed to the skybeacon. The next owner can figure out what he wants to do, since the skybeacon installation is so modular, it doesn't really add any complications to a future "robust" ADSB installation in the fuselage/panel of the airplane.
     
  10. Hiperbiper

    Hiperbiper Line Up and Wait

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    Having installed dozens of GDL-82's I have nothing but good things to report on it; easy to install and set up, hardwired (Coax) to the Transponder and able to use either the internal GPS or use RS232 out from 430/530/etc. No failures or returns thus far (yea I said it ).
    The above being said; I personally loath Garmin. What they did to Navworx and what they're trying to do to uAvonix ****es me off no end. Their "Customer Service" is a damn joke and their in-house phone techs are the rudest jerks I've ever had to deal with.

    JMPO,

    Chris
     
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  11. dmspilot

    dmspilot En-Route

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    Yes, you quoted the passage from SkyBeacon that says exactly that. Your ADS-B will still be broadcast but without a Mode A code or ident.
     
  12. NordicDave

    NordicDave Line Up and Wait

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    Didn't know the GDL-82 had a WAAS position output. Very compelling.

    -David
     
  13. Nmm347

    Nmm347 Filing Flight Plan

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    Does an aircrafts ADS-B broadcast include the Mode A code or ident status? My understanding is it includes the aircraft ID, velocity/speed, position, and altitude.
     
  14. Axtel4

    Axtel4 Pre-takeoff checklist

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    Yes.
     
  15. John Collins

    John Collins Pattern Altitude

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    What did Garmin do to NavWorx. The way I understand it, NavWorx fought with the FAA and lost. In the case of uAvionix, Garmin is suing them for infringement on a Garmin patent. uAvionix has been granted their own patent. It is TBD who is right, but the uAvionix patent was granted by the US Patent office with the law suit preceding the grant.
     
  16. nauga

    nauga Pattern Altitude PoA Supporter

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    I had pretty much decided on a GDL-82 but missed this in the install manual. Now there's no doubt. Thanks for the tip.

    Nauga,
    and his 3-way wingtip lights
     
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  17. kyleb

    kyleb En-Route PoA Supporter

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    I'm leaning that way too. Also, I bet the GDL will have better resale value if you rip it out one day and put an F-22 panel in your RV-4. My only reservation is I don't like feeding the borg, which Garmin has turned into. But they are the borg for a reason. The other solutions usually aren't quite as good.
     
  18. TigerGene

    TigerGene Pre-takeoff checklist

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    My research indicates that the GDL82 may have a few issues that prevent me from “pulling the trigger” on it.

    1. It is integrated with your transponder. If the GDL82 fails you are grounded. If the transponder fails, the GDL82 fails and you are grounded. However, if the Skybeacon fails for any reason, it seems to me, you can easly remove it (2 screws), enter the removal in the logbook (A&P sign off) and off you go. The FAR says that if ADS-B is installed it must be working and on at all times.

    2. I have read of a few folks having problems with the GDL82 failing when interrogated by certain military radars. Lots of military airspace around the country, could be a problem.

    3. The GDL82 is more expensive after install costs are included and more difficult to access for upgrade, maintenance or repair. Upgrade or program the Skybeacon from your cellphone.

    The Skybeacon is not without it’s problems but seems to be the the cheapest, easiest, cleanest solution available for a non-waas aircraft.
     
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  19. nauga

    nauga Pattern Altitude PoA Supporter

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    The GDL-82 is essentially a bolt-in and connect install for me. Given that Skybeacon does not have an option for an aft-facing white light on the tip installing them would require installing a tail beacon on my airplane. Neither cheaper nor cleaner, and far from easy.

    Nauga,
    tipped
     
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  20. Mtns2Skies

    Mtns2Skies Super Moderator Management Council Member PoA Supporter

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    This is simply false. The GDL82 is fail safe and the transponder still works regardless of the operation of the GDL82. I can pull the breaker to the GDL82 and the transponder still works just fine.
    I have no idea why this would be remotely true since the interrogation is still done through the transponder, and like the skybeacon it just appends the information to the end of the transponder signal.
    The GDL82 can be installed by yourself with a signoff from an A&P and why on earth would you need to access it for "Maintenance or repair"? This is avionics, not an engine. You won't be doing oil changes on your GDL82.
    The Skybeacon is a fine solution, no one is disputing that, but please, please don't make up falsities about the GDL82 to justify your purchase. You're just going to end up spreading misinformation for your own benefit. It sounds like your "research" was guided with you already having made a decision on which direction you were going and you're just looking for ways to make you feel better about it.
     
    Last edited: Mar 17, 2019
  21. TigerGene

    TigerGene Pre-takeoff checklist

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    GDL82 problem with military radar:

    https://tinyurl.com/y5doqfn7

    Concerning inoperative components;

    Once installed, the ADS-B system is required to be on and operating at ALL times.

    If the GDL82 fails you are grounded because ADS-B is inop. If the transponder fails, the GDL82 won’t be able to interrogate it for appropriate info so it won’t work either. Again, you are grounded.

    Perhaps I have this all wrong but this is what FAR 91.225 says:

    (f) Each person operating an aircraft equipped with ADS-B Out must operate this equipment in the transmit mode at all times.

    By my way of thinking, if the Uavionix Tail Beacon or transponder fail, the Tail Beacon can be easily REMOVED (by an A&P), making it no longer INSTALLED. Like an inop ELT, remove it, make a logbook entry, perhaps a placard and continue on. Am I wrong?
     
    Last edited: Mar 17, 2019
  22. John Collins

    John Collins Pattern Altitude

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    Here is what I wrote on the topic on BeechTalk discussing this same issue:

    Note that it does not require the ADS-B Out system to be working or provide good data. It merely indicates that the ADS-B Out system be operated in the transmit mode at all times. The only controls most installations have over the ADS-B Out systems are the circuit breaker and the Avionics Master switch. Some might be controlled by the Nav Light switch. In general, the only control is on/off and there isn't a separate control to disable transmit mode. In the Final rule issued by the FAA on the topic of "L. Ability To Turn Off ADS–B Out Transmissions", the FAA stated:


    L. Ability To Turn Off ADS–B Out Transmissions
    The NPRM proposed requiring a pilot to turn off ADS–B equipment if directed by ATC, for example, if the ADS–B unit was broadcasting erroneous information.
    ...
    The FAA modified the ground automation system to be able to exclude incorrect ADS–B data. With this enhancement to the automation, the aircraft does not need to have a capability for a pilot to disable ADS–B transmissions. Therefore, the final rule does not require the pilot to be able to turn off ADS–B Out transmissions.​


    The commenter wrote:
    So 91.215 gives an out for an inop or not maintained transponder. You're good to go so long as you stay out of transponder required airspace. ​

    91.225 does not give such relief. Per 91.225 (f) if you're equipped (its in the airplane) it must be operable at all times and in all airspace (even class G). Both 91.215(d) and 91.225(g) give you the ability to request permission from ATC to proceed with inop equipment to your destination or to a place where it can be repaired, but that's it. So if your mode C transponder breaks you don't need to do anything to fly with it broken outside transponder required airspace until you get a chance to fix it. If your ADS-B breaks you have to immediately get permission from ATC to takeoff anywhere and can only fly to your destination and then to somewhere to get it fixed.​


    It does not require that the equipment be operable at all times, it requires that the equipment be operated in the transmit mode at all times. There are several sources external to the ADS-B Out function that makes its transmissions not meet the requirements, including the transponder, the pressure altitude input, and the position source. Failure of these items or any configuration issues will not necessarily prevent the ADS-B Out equipment from operating in the transmit mode. The provision is telling the pilot that he is not authorized to turn the system off. Of course in an emergency, the pilot can waive any regulation as necessary, such as a fire or shedding a load when there is an alternator failure.

    The referenced section 91.225(g)(1) applies to operation with an inoperative ADS-B Out system. Parsing the wording reads like this (emphasis is mine and the splitting of the phrases is mine, but otherwise this is a direct quote):


    For operation of an aircraft with an inoperative ADS-B Out,

    to the airport of ultimate destination, including any intermediate stops,

    OR to proceed to a place where suitable repairs can be made

    OR both,

    the request may be made at any time.​


    For the most part these failures are going to be pointed out by ATC or by the FAA monitoring system. In the latter case, you may first find out when you get a letter from the local FSDO. Most towers do not have radar and are highly unlikely to know if your ADS-B Out is not performing. If you are VFR and not using ATC services, it is highly likely that you won't know the system is not working and as long as your system is transmitting, you will likely get a letter from the FSDO. If you are not getting power to the ADS-B Out system, no one will know unless you fly into one of the mandated airspace and talk to ATC.

    Regardless, once you are aware that your aircraft has an inoperative ADS-B Out system your request can be made at anytime, but I suspect that unless the aircraft is flying into airspace that mandates its usage, ATC will not be aware of the lack of conformance and certainly if the system failed to broadcast anything, there would not be any indication. You would not get TISB service and in fact your aircraft transponder target would generate a TISB target for other client aircraft.

    Of course if you determine there is an issue with your ADS-B, it should get fixed as soon as practical and at some point the FAA might insist on it for further flight. That might ground you. My guess is you would be given a substantial amount of time to comply.

    Also note the following from the final rule regarding scheduled maintenance:

    X. ADS–B Equipment Scheduled Maintenance
    The NPRM did not propose any additional continuing airworthiness requirements associated with the installation of ADS–B avionics equipment. A few commenters questioned the FAA’s plan for continued airworthiness inspections for ADS–B equipment.​

    This final rule does not add any continuing airworthiness inspection requirements. Transponder-based ADS–B systems will still be required to meet the requirements of § 91.413. However, ADS–B systems, without a transponder, do not have any new inspection requirements. The FAA will use the ground automation system to continuously monitor ADS–B functionality, which accomplishes the purposes of a recurrent inspection.

     
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  23. TigerGene

    TigerGene Pre-takeoff checklist

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    John:

    Thank you for that post. Makes things a bit more clear but the issue is still overly complex.

    I go well out of my way to avoid anything that would precipitate a letter from the FSDO. Strangely, compliance with ADS-B increases the odds of unwelcome FAA attention. Not sure it’s worth it.
     
  24. Mtns2Skies

    Mtns2Skies Super Moderator Management Council Member PoA Supporter

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    How often are you planning on this happening? Every other flight? They're both solid-state thoroughly tested components. You can go into the failure analysis on every single piece of electronics equipment you own and see how "easily removed" it is... but that's frankly paranoid thinking.

    Install it, set-it and forget it. You're WAY overthinking this and again trying to justify the decision you've already made.
     
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  25. TigerGene

    TigerGene Pre-takeoff checklist

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    I have NOT made a decision on WHAT to install or even to comply or not. However, whenever I make an important decision I always spend a lot of time reseraching until I thoroughly understand the issue to include all problems I can reasonably expect to encounter.

    I have been researching ADS-B for about 3 years now, both for the aircraft I fly at work and my personal aircraft. I have consulted with the FAA at conventions, and manufacturers sales reps and received good and BAD information from both. The GDL82 and the Sky Beacon are both attractive options for non-waas aircraft, and truthfully, either would be a fine choice.

    If one can wait till after 2020, the installed price of all ADS-B systems may drop dramatically as backlogs are satisfied and avionics shops clear out. Waiting may be the best choice for those able to do so. In the meantime, the reliability of the devices and the support offered by the manufacturers will be revealed. They seem to still be in the “Beta” phase where odd problems still crop up from time to time. How they address the problems are important.
     
  26. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    I wouldn't plan on that. On 1/1/2020, a significant portion of the fleet, possibly even a majority, still will not have been upgraded. Too many people waited, first because they thought the FAA was going to change the deadline, then because they thought other things would be coming out... And now, apparently, because they think the prices are going to go down.

    I think Garmin anticipated this kind of thing, because when they introduced the GDL 82 in 2017, on the webinar they specifically said "This is it. All our cards are on the table. We aren't even working on any further ADS-B products. Don't wait."

    For several years, it has been said that if every avionics shop in the country stopped doing anything but ADS-B installs, there still wasn't enough capacity to get all the installs done by 2020. I wouldn't be surprised at all to see the avionics shops continue to be slammed throughout 2020 and into 2021 before things start to calm down... And there's probably a backlog of people waiting for all the ADS-B stuff to calm down prior to their next upgrade (me, for example).

    Finally, for all the people who have decided that they will simply avoid rule airspace rather than equip, those non-equipped airplanes will continue to be sold over the next decade plus to owners who might want to fly in rule airspace and will get them equipped after purchase.

    So, I wouldn't expect ADS-B systems to drop in price any time soon, and if they do, it certainly won't be "dramatically".
     
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  27. GRG55

    GRG55 Final Approach

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    I see Aircraft Spruce is now advertising the Tailbeacon for sale. $1999, delivery in June.
     
  28. c177tx

    c177tx Pre-Flight

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    Explain the GNX375?
     
  29. asicer

    asicer En-Route

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    It's a remix.
    • GTX335 + GDL50R = GTX345
    • GTN650 - GNC255 = GPS175
    • GPS175 + GTX345 = GPS175 + GTX335 + GDL50R = GNX375
    Sort of like Taco Bell.
     
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  30. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    They may not have been working on it at the time... Someone came along with the idea, and they did it.
     
  31. George Qualley IV

    George Qualley IV Filing Flight Plan

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    Just installed a skyBeacon and did my test flight for my ADS-B rebate. The determining factor for me was the fact that (at least one avionics guy I talked to--but not the person that did the skyBeacon) my Narco AT50 didn't have enough output power to drive the GDL 82. If that's accurate, I would expect that there are a lot of people in that boat...
     
  32. trenton

    trenton Pre-Flight

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    We decided against the GDL 82 for the same reason (an aging KT 76). We opted for at GTX 335. Got tired of waiting for "next month" for the Skybeacon to ship.
     
  33. George Qualley IV

    George Qualley IV Filing Flight Plan

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    In case it's helpful to others, it does seem like they're pretty available now. The wait time was a week or so longer than quoted, but it was still wasn't bad.
     
  34. trenton

    trenton Pre-Flight

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