D180 consistently showing lower airspeed

[5RV]

Morning everyone.
150 hours trouble free D180 in an RV7A.
From the beginning the D180 has been displaying IAS about 10kts lower at the high end tapering down to almost accurate below 70kts.  Standard dynon pitot, standard mounting.
Anyone else encountered this? Any solutions?
thanks..

 

[dynonsupport]

What are you comparing it against? If you are using GPS it needs to be carefully done to take out winds, and GPS is TAS not IAS so it needs to be adjusted against that too. If it's another airspeed indicator, 99% of the time it's the other airspeed indicator that is wrong, especially if it's a mechanical device. Finally, make sure everything is in the same units since the D180 can be in knots or MPH.

If the error is real 90% of the time this is happening it's because of inaccurate static. You can test for this easily by doing a low pass over an airport runway at 70 knots and then at 150 knots. The altimeter should read the same at both speeds, but if you have static error it will not.

 

[PhantomPholly]

Most airspeed errors are caused by static problems. The location, angle of mounting, etc. of the static port is absolutely critical.

A leak in the pitot side of the system will not lower the pressure unless it is nearly as big as the pitot orifice. A pinhole in static can change the reading.