D180 IAS Window is Jumpy

My D180's IAS window is jumpy... it will go from 75.. 76.. 74.. 73.. 75... The leak-down test for the static and pitot were better than the PAP recommendation. The altimeter window changes smoothly... does anyone else see this issue? Called Dynon but they had no idea(s).

Thanks,
-Ron

Some EFIS makers do more smoothing/averaging on the ASI than others. Dynon seems to be on the fast side of the group. Some of them are on the other extreme and are really smooth but look to have some lag in them.

Which is best? Good question, there are pros and cons for both....

A jumpy reading can be hard to figure out. It could be buffeting along the static ports. It could be a intermittent leak somewhere in the pitot or static system. It could be just the normal noise in the system and the fact that Dynon does not average it out.

This shows up on steam gauges as a bouncing needle. With them you can pick the number in between the bounces. It is a little more noticable when you have a digital number on an EFIS changing.

Could just be the day, I fly an Evektor with steam guages while I am building and on windy bumpy days the ASI jumps all over the place.

It can be unnerving when on final close to stall speed in heavy crosswinds, I did a weeks full of crosswind work and got good at picking out 65 Kts out of a jumpy needle.

redmark said:

My D180's IAS window is jumpy... it will go from 75.. 76.. 74.. 73.. 75... The leak-down test for the static and pitot were better than the PAP recommendation. The altimeter window changes smoothly... does anyone else see this issue? Called Dynon but they had no idea(s).

Thanks,
-Ron

Click to expand...

I'd be inclined to make a simple flow restrictor and put it in the pitot plumbing. Say, a plug of aluminum rod with a .060" orifice or so.

Mine's the same

and so was the red prototype when I checked out in the aitplane. IAS numbers are continually changing but the TAS readout (internally calculated) is steady. I just assumed it's typical of the D180. I'm planning to add steam gauges in the near future.

Wayne 120241/N143WM