Acceleration and Roll: Myth or Fact?

[BobbyHargrave]

Old Dynon D-10 user tell me that his D-10 unit rolls with acceleration such as on takeoff. He came by my hangar and wanted to blow on my pitot tube to test my D-10A! NO WAY! What the heck?! Is this guy messed up or was there such an issue with early D-10? I did not let him try this on my aircraft!

 

[gmcjetpilot]

Why did you not let this guy blow you pitot tube. :

I know that acceleration can even cause a mechanical attitude gyro to show a pitch change. Roll?

I do think if your buddy would blow into the pitot you would get a pitch indicated and than would level back out. So what? Unless he is going to blow into your pitot on takeoff roll I don't think it is an issue. I think Dynon uses airspeed (or rate of change or acceleration) to take out acceleration errors. Increasing airspeed real fast by artificial means (blowing on the pitot) is not a flight condition.

Components of acceleration in any direction must resolved by the software to show attitude, any EFIS does this. For example take a constant turn while adding power or reducing power, airspeed will change the g's, in all direction, will also change. Airspeed input to attitude display is useful in compensating, so there seems to be a couple to airspeed and attitude in the software. I am no expert so I can't wait to hear what Dynon says, but I have not heard or seen this in any Dynon as a problem on take off. Yes the Dynon can have small errors from time to time but they are small.

Cheers George

 

[dynonsupport]

Thanks for the correct reply George.

If you give the Dynon "false" airspeed by blowing in the pitot tube, you will see pitch. As george says, we use airspeed as one of our acceleration inputs, and thus you just told us that the airplane accelerated when it didn't, you can expect to see some error from this. However, all the error will be in pitch. Basically, the unit sees airspeed change suddenly, but the internal accelerometers see no change. If you think about it, the only way this could happen in flight is with a pitch change that exactly matches gravity's acceleration against the airspeed change.

We are not familiar with any roll error on accleration. This sounds like the unit may be installed "sideways" where the unit is not aligned with the airframe, or the unit may have some other issue. The calculations in the D10 and D10A are exactly the same, so we didn't "fix" that in the D10A, but as far as we know, we also don't have a roll-on-acceleration problem.