Skyview attitude dependent upon GPS?

[ChiefPilot]

I've upgraded my -6A to include a Dynon Skyview system and wondering if what I saw today is normal.

Situation is this: sitting in the hangar, the attitude display is solid. Field elevation from the AWOS dialed shows the correct field elevation, attitude indicates wings level and approximately 4.5º nose up (the -6A sits slightly nose high). All good.

The problem happened when the GPS2020 receiver managed to lock onto four satellites (shown via the GPS status display) through the open windows/door of the hangar. The attitude display started swinging up, down, left, and right. Disabling the GPS caused a reversion to normal steady display.

Is this normal? Is the Skyview so dependent on GPS information that it's attitude display becomes unreliable with questionable GPS reception?

7" Display, one ADAHRS, one magnetometer, one 2020GPS, and two AP servos in the system running 14.0.7.3621 (my serial # is not affected by the other bug(s) in v14 - I need this version to see the 2020 GPS).

 

[KRviator]

Here's the same post I made on the VAF, in case you see this one first.

What you are seeing is normal. Mine does the same when I lose GPS lock in the hangar.

SkyView uses a combination of inertial sensors coupled to airdata, and defaults to GPS when the airdata is unavailable. So when the GPS position (and consequently GPS 'speed') is lost and reacquired (with a different position and consequently "speed to this new positon"), it throws the attitude algorithm off as the only way to achieve such "performance" is with funky attitudes.

When you're in flight, it will use IAS in its' computations and will be rock solid. Remember you don't have to have GPS for SkyView to work.

Don't stress.

 

[ChiefPilot]

Here's the same post I made on the VAF, in case you see this one first.

What you are seeing is normal. Mine does the same when I lose GPS lock in the hangar.

Thanks for the reply (in both places )

If that's the case, shouldn't "GPS ASSIST" be displayed? It was not...

So another test today revealed more problems. Same as before, only this time clear of any buildings and with 8 satellites locked / 12 in view per the GPS status screen. Attitude was incorrect, changing by several degrees in pitch and heading wandering by a couple of degrees as well.

Disabling the GPS2020 revealed another issue as well. I was under the impression that the map would fall back from POS1 to GPS1 for map position if POS1 became unavailable as described on page 4-28 of the system installation guide. This did not occur - the map was shown but had an error that indicated that the position was unknown.

This was interesting because the panel mount GPS (KLN89B, configured as "GENERIC AVIATION" on GPS 1) was providing flight plan info - the map was selected to display flight plan data from GPS 1 and was in fact showing the flight plan loaded into the KLN89B. Skyview was clearly reading the waypoints without error, but failed to update the map with the position provided by the GPS.

Dynon - help! Any suggestions?

 

[KRviator]

Dynon's gurus will no doubt clarify when they get in on Monday morning, but I recall GPS ASSSIST is only displayed in flight, where you had airspeed to begin with and then lost it. Whereas with us on the ground in the hangar, it is smart enough to realise we never had it to start with and is using GPS in addition to not in place of the air data.

Did your KLN-89 have a valid position? You'd need to verify that on the KLN rather than SkyView. It is one thing to display the flight plan, but it won't be able to navigate along that plan if does not know where it is, even though it will still output the flight plan to external devices.

 

[ChiefPilot]

Did your KLN-89 have a valid position? You'd need to verify that on the KLN rather than SkyView. It is one thing to display the flight plan, but it won't be able to navigate along that plan if does not know where it is, even though it will still output the flight plan to external devices.

Yes, the KLN had a position solution as verified on the unit itself. It won't in fact display a flight plan unless it already knows where it is, so I'm pretty sure it was delivering the current position to the Dynon along with the waypoints in the flight plan.

 

[dynonsupport]

Brad,
We replied over on VAF as well. It's a bit tricky to try and manage two identical threads at once as they diverge!

http://www.vansairforce.com/community/showthread.php?t=135878

I think you'd do better with a call to us when you're at the plane and it's outside. We can see all sorts of things on diagnostic screens which will help us get the system configured correctly to use the KLN, and see what's up with that GPS-2020.

 

[ChiefPilot]

It's going up later this week and if problems persist I'll call in to get better diagnostic info to you.

Thanks!
Brad