[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 4.5? 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 Dynon so dependent on GPS information that it's attitude display becomes unreliable with questionable GPS reception?

 

[n82rb]

I'm sure someone from dynon support will answer quickly they are on here, but no that is not normal. The attitude info comes from the ahrs the gps data should not affect it.

Bob burns
Rv-4 n82rb

 

[ChiefPilot]

I'm sure someone from dynon support will answer quickly they are on here, but no that is not normal. The attitude info comes from the ahrs the gps data should not affect it.

Bob burns
Rv-4 n82rb

That's what I thought and that would make sense - hopefully they'll have some insight for me on Monday.

Thanks!

 

[KRviator]

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, 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]

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, it throws the attitude algorithm off as the only way to achieve such "performance" is with funky attitudes.

It should be displaying "GPS ASSIST" in that case, which it is not doing...

 

[Dynon]

Brad,
What you are seeing is "normal" although a bit unexpected.

SkyView uses the pitot system for the attitude solution when you're in flight. It doesn't use the GPS at all, until the pitot fails. So 99.99% of the time your GPS can do anything and you won't see this.

When you're on the ground in a hangar like that, SkyView does assume the pitot has failed, and is using GPS as a backup. Because you're always in GPS ASSIST on the ground and that's normal, we don't show "GPS ASSIST" until you're in the air. We try and only show warnings when it's not the expected situation.

It sounds like your GPS solution is coming in and out, and this is pushing the attitude around a bit by giving us large changes in position. This is the kind of unexpected part, since the GPS is generally pretty good at telling us if it has a stable solution and we don't use if it doesn't. Sounds like you are right on the very edge and the GPS is struggling. This is really unlikely in any kind of flight unless you're in a tunnel Right now we're not really worried since GPS can be really unstable in a hangar, but if it was to do that once outside we'd probably want to see that GPS.

For you to see what you're seeing in flight, you'd need two failures- your pitot would need to fail, and then your GPS would need to act up. The effect would also be smaller, since the various errors would be smaller percentages. If you're doing zero knots, even a 2 knot error is an infinite percentage. In flight, at 100 knots, a 10 knot error in your GPS doesn't cause any noticeable issues. Being on the ground is always a weird place for a system since none of the flight physics apply, and we don't really have solid data that you're on the ground, so we're basically always defaulting to assuming you're in the air when that's the safer assumption.

--Ian Jordan