The airspeed sensor is not ready
What ArduPilot says:
- PreArm: Airspeed N not healthy
- not using Primary (N)
- N need pre-flight calibration
- N not healthy
- N pre-flight calibration in progress
- PreArm: Airspeed: …
An airspeed sensor that is switched on and used for control (ARSPD_USE is not 0) is not healthy: either its driver gets no readings, or its zero (ARSPD_OFFSET) is still 0, which means the calibration at start-up has not finished or has failed. The number is the sensor, counting from 1. It belongs to the Airspeed group of arming checks.
What to do, most likely first
The zero calibration has not been done, or it failed.
Check“Airspeed 1 calibrated” did not appear after power-on, and
ARSPD_OFFSETreads 0.FixCover the pitot tube loosely, so that no wind blows into it, and run the airspeed calibration from the ground station (pre-flight calibration), or reboot with the tube covered. Take the cover off before flight.
The sensor does not answer: wiring, or the wrong type or bus in the parameters.
Check“Airspeed 1 init failed” or “no sensor found” came at start-up; the airspeed in the ground station stays at exactly 0 when you blow gently towards the tube from a distance.
FixCheck the four wires of the sensor, then
ARSPD_TYPEandARSPD_BUS, and reboot.From 4.7: the primary sensor is set not to be used while another one is.
CheckThe message is “not using Primary”; compare
ARSPD_PRIMARYwith theARSPD_USEof each sensor.FixPoint
ARSPD_PRIMARYat a sensor that is in use, or set that sensor's use parameter to 1.
Parameters to look at
| Parameter | What it is |
|---|---|
ARSPD_TYPE | Airspeed type |
ARSPD_USE | Airspeed use |
ARSPD_OFFSET | Airspeed offset |
ARSPD_SKIP_CAL | Skip airspeed offset calibration on startup |
ARSPD_BUS | Airspeed I2C bus |
ARSPD_PRIMARY | Primary airspeed sensor |
Where to do it:Board & Wiring Planner
The code that sends it
PreArm: Airspeed N not healthy
libraries/AP_Arming/AP_Arming.cpp AP_Arming::airspeed_checks() · Open in ArduPilot Copter-4.6.3
not using Primary (N)
libraries/AP_Airspeed/AP_Airspeed.cpp AP_Airspeed::arming_checks() · Open in ArduPilot Copter-4.7.1
N need pre-flight calibration
libraries/AP_Airspeed/AP_Airspeed.cpp AP_Airspeed::arming_checks() · Open in ArduPilot Copter-4.7.1
N not healthy
libraries/AP_Airspeed/AP_Airspeed.cpp AP_Airspeed::arming_checks() · Open in ArduPilot Copter-4.7.1
And 2 more messages, sent from the same places.