The airspeed zero moved a lot since last time: wind was probably in the tube
What ArduPilot says:
- Arspd N offset change large;cover and recal
The zero just measured for the airspeed sensor differs from the one saved last time by more than ARSPD_OFF_PCNT allows: the change would shift the reading by more than that percentage of AIRSPEED_MIN. A sensor's zero rarely moves that much by itself; usually wind was blowing into the pitot tube during the one second of calibration. The new zero has been saved all the same, so the airspeed in this flight may be wrong.
What to do, most likely first
The pitot tube was uncovered in the wind during the calibration at start-up.
FixCover the tube loosely and calibrate again: from the ground station (pre-flight calibration, airspeed) or by rebooting. Uncover it before take-off.
The sensor or its tubing was changed, or the temperature is very different from last time.
CheckCalibrate once more with the tube covered: the message does not come back.
FixNothing more: the second calibration confirmed the new zero.
Water in the tube, or a kinked or leaking hose, makes the zero wander.
CheckThe message comes back at every calibration even with the tube covered.
FixBlow the tube out away from the sensor, never into it, and replace kinked or loose hoses.
Parameters to look at
| Parameter | What it is |
|---|---|
ARSPD_OFF_PCNT | Maximum offset cal speed error |
ARSPD_OFFSET | Airspeed offset |
AIRSPEED_MIN | Minimum Airspeed |
The code that sends it
Arspd N offset change large;cover and recal
libraries/AP_Airspeed/AP_Airspeed.cpp AP_Airspeed::update_calibration() · Open in ArduPilot Copter-4.7.1