GPS Assist

[Carl_Froehlich]

I note the SkyView documentation says airspeed input to the attitude algorithm will shift to GPS ground speed if the airspeed input goes to zero.

What happens to attitude indication with only a partially blocked pitot - such that indicated airspeed is abnormally low or erratic?

Is there a method to force the attitude indication to shift to GPS assist for airspeed input in such a scenario?

Carl

 

[Carl_Froehlich]

Now that the good folks at Dynon are back from the long weekend, resubmitting my query.

Carl

 

[dynonsupport]

Carl:

There's no provision in SkyView to "force" the use of GPS Assist instead of Pitot / Airspeed.

I note the SkyView documentation says airspeed input to the attitude algorithm will shift to GPS ground speed if the airspeed input goes to zero.

What happens to attitude indication with only a partially blocked pitot - such that indicated airspeed is abnormally low or erratic?

Is there a method to force the attitude indication to shift to GPS assist for airspeed input in such a scenario?

Carl

 

[Carl_Froehlich]

Thanks for the response.

What about the other question on what would happen to attitude indication for a partially blocked pitot?

Thanks,
Carl

 

[Dynon]

If your pitot is completely blocked (ie completely frozen due to a heated pitot failure) your airspeed would be "frozen" while you're at the same altitude, but then change incorrectly with changes to altitude. So when you change altitude and airspeed isn't correct, attitude will be incorrect by some amount and should not be considered reliable.

If your pitot is partially blocked, its effect on attitude depends what it's ultimate effect on airspeed is. It could be anything from nothing at all (if airspeed is more or less unaffected despite the partial blockage) to causing the attitude to a bit erratic if the airspeed is.

If the pitot is blocked but leaks down to zero (fairly common in pitot freezes, though not guaranteed), GPS assist takes over and allows for backup attitude.

All of the above is why you need to have a working heated pitot in IFR conditions and why we have an open-ended service bulletin for our heated pitot ( http://www.dynonavionics.com/docs/support_bulletin_101014.html) now that we've improved its design so that it can do a better job of shedding water than it did in its last incarnation. If you have a working heated pitot, you're able to shed water and prevent freezing of the pitot so that you don't need to deal with any of the issues with the above scenarios.