"air on ground" ADS-B test failure

[mooneyflyfast]

I had a new GTX 345 installed in my 81 J.  FAA test for the rebate shows "air on ground" failure--which I understand means it is reporting airborne when the airplane is on the ground.  Neither Garmin nor FAA seem to know how to correct this.  Seems like Garmin could at least let my shop know what configuration settings to check  My shop is a fair distance away and I have already had it back one time.  Trial and error guessing is not the best.  Has anyone else had this problem?  

At this point I can't recommend the GTX 345 or Garmin's customer support.

 

[Deb]

There is some discussion of this on Beechtalk.com:

I had the same issue with a GTX 345 and 430W. The error is transmitting 'air' status when on the ground. My installer had the emitter category mis-configured as 'Small' as opposed to 'Light' and the max airspeed set to <300 kts vs <150 kts. This may have screwed up the internal air vs ground logic. Haven't yet flown it since these changes were made to know if that was the problem. Anybody else see this and know what would cause it with a GTX 345 or 345R?

And:

Yes, I know of someone else who is seeing a problem with "air on ground" errors with the 345, primarily occurring after landing for up to 2 to 3 minutes, triggering an error in their FAA report. They have swapped units with no change. Interestingly, the flight timer is also running during this time, so it certainly appears to be a logic problem versus the ground equipment. So far, no word from Garmin on what could be causing this. My 345 works fine, and I have the same installer, so it seems unlikely that it is a configuration issue.

Also:

Regarding the "air on ground" issue. I found Garmin Service Advisory 1629. Deals with the GDL 84/88 interfaced to GNS and GTN boxes. It says the air onground error can be caused by taxing before the navigator has a 3D signal. I'm wondering if this may the cause of my problem with the GTX 345r. I have been disappointed with Garmins lack of customger service with this problem.

You might try emailing Trek Lawler at Garmin: trek.lawler@garmin.com. He's usually responsive.

[TrekLawler]

Hello everyone,
   I've been asked lately a lot about the air on ground faults on reports being received. in most of these cases we can explain the issue after speaking with the pilot but the GTX and other ADSB units require certain parameters to make sure the system reports this correctly. along with the service advisory on this that can be found here:

http://garmin.blogs.com/aviationalerts/2016/05/service-advisory-1629-airground-status.html

here are some steps to take on your next flight which will make sure the system is not transitioning this data incorrectly.

1.    Position the aircraft outside of any hangars with a clear view of the sky.
2.    Conduct a normal aircraft power on sequence by starting the engine(s) and avionics.
3.    Remain stationary until GPS position has been obtained and your ADS-B equipment indicates no faults or failures.
4.    Taxi at a normal taxi speed (no faster than a brisk walk).
5.    Depart the runway using a normal climb profile for your aircraft.
6.    Fly either a normal traffic pattern or straight-in approach to land. Fly a normal 3 degree glide path, or as close as possible given any obstacles on the approach path.
7.    Upon touchdown, decelerate in a straight line on the center of the runway, only turning off the runway after a normal taxi speed (no faster than a brisk walk) has been achieved.
8.    After exiting the runway, stop the aircraft for a period of at least 5 seconds before taxiing.
9.    Taxi to parking at a normal taxi speed (no faster than a brisk walk).
10.    Allow the aircraft to come to a complete stop for a period of at least 5 seconds before turning off avionics.

let me know if there are any other questions,

[flyboy0681]

Had the same problem with the GTN 750/GDL 88 combo. The shop emailed me the following instructions to change the GTN configuration. I'm not sure how it will translate to other Garmin units however:

1. The antenna we use should be set for "disable test" not "enable test".
2. Change air/ground discrete to "not installed".

 

[Piloto]

There is no squat switch on the M20J but an airspeed switch. The switch on the ground status is active when below 60kts IAS. The switch is attached behind on the airspeed indicator. It is used to keep the gear from retracting on the ground. You may tie to the switch for an on ground indicator. You can also use the KR-87 ADF timer switch located underneath the left wing. It looks like a small spoon hanging down.

José

Edited November 9, 2016 by Piloto

[jetdriven]

On November 9, 2016 at 3:28 PM, Piloto said:

There is no squat switch on the M20J but an airspeed switch. The switch on the ground status is active when below 60kts IAS. The switch is attached behind on the airspeed indicator. It is used to keep the gear from retracting on the ground. You may tie to the switch for an on ground indicator. You can also use the KR-87 ADF timer switch located underneath the left wing. It looks like a small spoon hanging down.

José

That's funny, my M20J has a squat switch. 

[Piloto]

5 hours ago, jetdriven said:

That's funny, my M20J has a squat switch. 

Yes early M20J had the squat switch. Later on Mooney replaced it with the air switch.

[takair]

I don't have the 345 install manual, but I suspect some of the basics are the same as the 330.  The air-ground on the 330 can be set by ground speed.  40kt would be typical. It is easy to set....or mis-set.  

Where do you fly out of?  I would think that ADS-B coverage is limited at many airports, especially 1090.  It may be possible that you are getting erroneous data from the FAA site.  I would think you need to be at one of the larger ADS-B equipped airports for them to have this data regarding your flight.

[mooneyflyfast]

I followed Trek's procedure on a regular cross country flight Friday and passed the test including no "air on ground problem".. The only "rule"airspace I was in was above 10,000 and I made 0 turns in it. 

[ArtVandelay]

On 11/11/2016 at 6:52 PM, Piloto said:

Yes early M20J had the squat switch. Later on Mooney replaced it with the air switch.

My 78 has an air switch, so I assume only 77s had squat switch?

[Jeev]

On 11/9/2016 at 9:38 AM, TrekLawler said:

Hello everyone,
   I've been asked lately a lot about the air on ground faults on reports being received. in most of these cases we can explain the issue after speaking with the pilot but the GTX and other ADSB units require certain parameters to make sure the system reports this correctly. along with the service advisory on this that can be found here:

http://garmin.blogs.com/aviationalerts/2016/05/service-advisory-1629-airground-status.html

here are some steps to take on your next flight which will make sure the system is not transitioning this data incorrectly.

1.    Position the aircraft outside of any hangars with a clear view of the sky.
2.    Conduct a normal aircraft power on sequence by starting the engine(s) and avionics.
3.    Remain stationary until GPS position has been obtained and your ADS-B equipment indicates no faults or failures.
4.    Taxi at a normal taxi speed (no faster than a brisk walk).
5.    Depart the runway using a normal climb profile for your aircraft.
6.    Fly either a normal traffic pattern or straight-in approach to land. Fly a normal 3 degree glide path, or as close as possible given any obstacles on the approach path.
7.    Upon touchdown, decelerate in a straight line on the center of the runway, only turning off the runway after a normal taxi speed (no faster than a brisk walk) has been achieved.
8.    After exiting the runway, stop the aircraft for a period of at least 5 seconds before taxiing.
9.    Taxi to parking at a normal taxi speed (no faster than a brisk walk).
10.    Allow the aircraft to come to a complete stop for a period of at least 5 seconds before turning off avionics.

let me know if there are any other questions,

Do what Trek lists above.  I failed two times for Air on ground, after I followed the instructions above I passed.  Rebate on the way

[PeytonM]

1989 J. I did a swap of my 430W for the IFD440. I had no issues with ADS-B test before the swap. After the swap, I got the "Air-on-ground failure." Garmin330ES. 

Did I miss a config screen in the IFD440?

[Cruiser]

Avidyne Installation Manual - Section 6.12

Table 73 ADS-B Output (page 85)

For ADS-B out compliance, a squat switch is required for automatically selecting the transponder air or ground mode of operation. For aircraft without a squat switch, connect the squat switch input of the transponder to P1001 pin 8 of one of the IFD5XX/4XX. Set the transponder to accept an active low when performing that squat switch setup.

[Cruiser]

Garmin Install manual Table 6-38 Squat Switch Configuration.

Default selection is Squat Switch = NO 

This sets the GTX to use automated airborne determination from other sources.

 

Avidyne says you need it, Garmin says you don't (squat switch) 

Only your avionics technician knows for sure.

[Piloto]

On ground can easily be determined by the GPS ground speed been less than 60kts. Why Garmin  wouldn't use this instead of a on ground switch.

José

[jetdriven]

Squat switch is hard to install on a 172. 

Garmin does use this st least on the 345.  Default is 45 or 60 knots can't remember which. It's adjustable. 

Edited June 24, 2017 by jetdriven

[PeytonM]

I guess my "air-on-ground" error was a fluke. I have flown a half dozen flights since, with no issue.