Airspeed readings reasonable?

Matex F765-Wing with a digital airspeed sensor. Pitot well clear of the slipstream.

I understand from the docs that airspeed can be expected to jump around. But this much? Shouldn’t the startup calibration attempt to change the Offset so that the airspeed is pretty close to 0? Outside air temp was -1C if it matters.

Airspeed readings while on the ground, after startup calibration, just walking the plane from the parking lot to the field for launch:

First 30 seconds or so of the flight.

Final approach and landing:

Log at

@tridge I’m curious whether you have any thoughts or pointers?

Hi @Christopher_Milner

Everything looks normal. You have a small offset of the Airspeed sensor of ca. 14 Pascal.
This results in an airspeed offset of nearly 5 m/s.

difference pressure = (air density / 2) * airspeed squared
airspeed = square root (2 times difference pressure / density)

The nature of a square root dependency relates to significant changes especially near zero airspeed.
Put some numbers in the formula above results in
v = sqrt (2*14Pa/1.225gk/m**3) = 4.78 m/s

You can try to reduce the difference pressure sensor offset by let heat up the sensor and covering the Pitot-tube before the ground calibration. An offset drift of a few Pascals is common for this type of consumer grade sensors.

Hope this helps.

Thanks for replying!

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