The airspeed sensor does not answer
What ArduPilot says:
- Airspeed N init failed
- Airspeed N not initalized, cannot cal
- AUAV AIRSPEED[N]: no sensor found on bus N
- MS4525[N]: no sensor found
- Airspeed N unhealthy
- MS5525[N]: no sensor found
Also explained here: 1 more
- Airspeed N not initialized, cannot cal
An airspeed sensor is switched on in the parameters (ARSPD_TYPE) but the flight controller cannot talk to it. “init failed” and “no sensor found” come at start-up, when nothing answered on the bus. “not initialised, cannot cal” comes when a calibration is asked of a sensor that never started. “Airspeed 1 unhealthy” means the sensor gave no valid reading during the whole calibration. The plane has no measured airspeed: with ARSPD_USE 1 it will not arm, and with ARSPD_USE 0 it flies on its own estimate.
What to do, most likely first
The sensor is wired wrongly or has no power: the two data wires swapped, a plug in the wrong port.
CheckAn I2C sensor needs four wires: 5 V, ground, SDA to SDA and SCL to SCL. Many boards do not power the port from USB alone.
FixCorrect the wiring and power the board from the battery; the Board & Wiring Planner shows which pads are SDA and SCL.
ARSPD_TYPEnames another sensor than the one fitted, orARSPD_BUSpoints at the wrong I2C bus.CheckRead the chip name on the sensor (MS4525, MS5525, SDP3x, DLVR) and compare it with
ARSPD_TYPE.FixSet the right
ARSPD_TYPE; if the sensor is still not found, try the other values ofARSPD_BUS. Reboot after each change.No airspeed sensor is fitted, but one is switched on in the parameters.
FixSet
ARSPD_TYPEto 0 and reboot. A plane flies well without an airspeed sensor.
Parameters to look at
| Parameter | What it is |
|---|---|
ARSPD_TYPE | Airspeed type |
ARSPD_BUS | Airspeed I2C bus |
ARSPD_PIN | Airspeed pin |
ARSPD_USE | Airspeed use |
Where to do it:Board & Wiring Planner
The code that sends it
Airspeed N init failed
libraries/AP_Airspeed/AP_Airspeed.cpp AP_Airspeed::add_backend() · Open in ArduPilot Copter-4.7.1
libraries/AP_Airspeed/AP_Airspeed.cpp AP_Airspeed::allocate() · Open in ArduPilot Copter-4.7.1
Airspeed N not initalized, cannot cal
libraries/AP_Airspeed/AP_Airspeed.cpp AP_Airspeed::calibrate() · Open in ArduPilot Copter-4.6.3
AUAV AIRSPEED[N]: no sensor found on bus N
libraries/AP_Airspeed/AP_Airspeed_AUAV.cpp AP_Airspeed_AUAV::init() · Open in ArduPilot Copter-4.7.1
MS4525[N]: no sensor found
libraries/AP_Airspeed/AP_Airspeed_MS4525.cpp AP_Airspeed_MS4525::init() · Open in ArduPilot Copter-4.7.1
And 3 more messages, sent from the same places.