Air mode or Ground mode?

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  • Air mode or Ground mode?

    I have failed my first "PAPR" (Public ADS-B Performance Report) flight that was intended as qualification for the FAA's $500 rebate for installing ADS-B. The reason provided by the FAA translates to "ADS-B system transmitting in Air mode while on the ground."

    I am receiving ambiguous information on how this could be. So a simple question: Does the FAA determine whether I am in Air mode strictly from mode information (Air vs Ground) broadcast by the transponder? Or do they possibly analyze flight characteristics to make that determination independently?

  • #2
    Taxi slower, man. You're not a Southwest captain. ;-)

    (No, I know know what's encoded in the ADS-B Out whilst in ground mode.)

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    • #3
      Originally posted by Scott Dyer HPN/NY View Post
      Taxi slower, man. You're not a Southwest captain. ;-)
      Chuckle, you made me recall one day at DEN while taxiing out to the north on that l-o-n-g taxiway for
      a takeoff towards the south, had some smarta-- copilot <g> say to me "Vee One".

      best, randy

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      • #4
        Mark, What little reading I've done says that planes without a landing gear squat switch, such as yours, can be problematic. Some installations rely on a GPS-given ground speed threshold. That can be a problem for 152s because ground speed can be very low into a honking headwind. One owner's solution was a switch in the pitot line, set to switch between air and ground mode at an airspeed well below stall.

        You need to talk to your installer to find out what s/he set up for the air/ground mode switch -- if anything.
        Hate is a self-built dungeon in which a man imprisons his own soul.

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        • #5
          A quick peek at the ADS-B format indicates there are indeed flags for the mode.

          See Aircraft Operation Status.

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          • #6
            Originally posted by Randy Sohn View Post
            had some smarta-- copilot <g> say to me "Vee One".
            Hmmmm, that doesn't sound that smart to me!


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            • #7
              I just heard from the FAA, and it now appears that they do _not_ rely totally on the mode broadcast by the transponder. They even provided a diagram of my taxi route, overlaid on a satellite image of the airport, showing where the transponder switched to Air mode while I was still on the ground (which they clearly knew).

              Appareo (the device is their Stratus ESG) of course tells me this is MY fault, euphemized as "pilot induced": "...if after the ESG acquires its position as indicated by the Lat/Lon on the display and you taxi out for takeoff at a speed of 15 knots or faster for 10 seconds or longer this will automatically put you into the air mode..." Really?

              My installer assures me the squat switch is set to None. So the advice is to taxi slowly, and also to do a full stop for 10-15 seconds after landing to cajole the unit back into Ground mode.

              Having to learn these undocumented tricks in 2019 to obtain the correct operating mode does not feel very "NextGen" to me. Why not at least a "Ground" button?

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              • #8

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                • #9
                  Originally posted by Larry sreyoB View Post
                  Hmmmm, that doesn't sound that smart to me!
                  "The aeroplane has unveiled for us the true face of the earth." - Antoine de Saint-Exupery

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                  • #10
                    Chuckle, hell's bells, hadda taxi halfway to Cheyenne for that takeoff towards the south - like some ole graybeard once told me when I was a new hire "we ain't got all day!"

                    best, randy

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                    • #11
                      I had the same problem in November with my Appareo. But I was apparently causing it because I was overriding the ground mode.

                      I've always kept my transponder on ALT even on the ground because of this note at some airports: "ASDE-X in use. Operate transponders with altitude reporting mode and ADS-B (if equipped) enabled on all airport surface". When I called about it, I was told for the rebate test, leave the transponder alone and let it do its thing for ground mode. So I repeated the test that way and it was successful and I got my $500.

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                      • #12
                        Appareo refused to communicate any further in email after the initial boilerplate. But the FAA helped me determine that Appareo put me in Air mode because I was taxiing before GPS position was locked. The FAA subsequently approved the rebate after a brief flight where I waited out the GPS lock before moving.

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