All explanations

540 explanations of what ArduPilot Copter and Plane say and log, by topic. Each tells what the message means and what to do, the most likely cause first.

Start-up and what the board reports

The flight controller was restarted by its watchdogForcing safety off for watchdog The firmware cannot tell which board it is running onConfig Error: Pixhawk2 requires FMUv3 firmware Start-up has stopped on a configuration errorConfig Error: fix problem then reboot The IO co-processor could not be given its firmwareConfig Error: Failed to update IO firmware The board's name and the processor's unique ID The revision of the operating system under ArduPilot The firmware's name, version and source revision The motor layout this copter is set up forFrame: …/…The ground station announcing itself Start-up is running, then finishedArduPilot Ready The plane starts without an airspeed sensorNo airspeed sensor Factory calibration values were restored from the bootloader areaLoaded N persistent parameters (N errors)Which signal each output sends A request to enter the loader or replace the bootloaderEntering DFU mode How fast an IMU is readIMUN:…… sampling N.NkHz/N.NkHz The board's second processor was foundIOMCU: 0x… 0x… 0x…The ground station connected before the motors were set upmotors not allocated Start-up: the gyros are being calibrated, keep the plane stillGround start with delay

Arming, disarming and the safety switch

Another aircraft is too close, by ADS-BPreArm: ADSB threat detected A controller gain is zero or negativePreArm: Bad parameter: …ANGLE_MAX is outside 10° to 80°PreArm: Check ANGLE_MAX The pilot's maximum climb rate is zero or negativePreArm: Check PILOT_SPD_UP The disarm switch is in its “disarm” positionPreArm: Disarm Switch on The ground station link is lost right nowPreArm: GCS failsafe on The safety switch has not been pressedPreArm: Hardware safety switch The IMU heater has not reached its temperature yetPreArm: heater temp low (N.N < N)The copter thinks it is tilted too far to armPreArm: Leaning The current flight mode does not allow armingPreArm: … mode not armable The motor interlock switch is in the wayPreArm: Interlock/E-Stop Conflict The motor emergency stop is activePreArm: Motors Emergency Stopped ArduPilot has not finished startingPreArm: System not initialised Remote ID is not readyARM_STATUS not available The minimum airspeed is set below 5 m/sPreArm: AIRSPEED_MIN too low (N < N)A roll or pitch limit is too small to fly withPreArm: PTCH_LIM_MAX_DEG too small (N.N)On a QuadPlane, AUTO needs a mission that begins with a take-offTakeoff waypoint required The long failsafe is set to come before the short onePreArm: FS_LONG_TIMEOUT < FS_SHORT_TIMEOUT The mission is still in its landing partPreArm: In landing sequence The plane will not arm in this flight modenot Q mode Arming or disarming with the rudder stick was refusedRudder disarm: disabled The throttle input is reversed and the failsafe value is on the wrong sidePreArm: Invalid THR_FS_VALUE for rev throttle Mid-stick cruise throttle is on, but the throttle trim is not in the middlePreArm: Throttle trim not near center stick(N)It armed with the arming checks switched offWarning: Arming Checks Disabled The motors are armed The motors are disarmed, and how to see why The lost-copter alarm was switched on with the sticksLocate Copter alarm The plane was armed or disarmedThrottle armed

Radio control

The throttle failsafe value does not fit the throttle rangePreArm: Check FS_THR_VALUE The VTOL forward-throttle control is not at its minimumPreArm: VTOL Fwd Throttle is not zero A radio calibration is in progressPreArm: RC calibrating It is in radio failsafe right nowPreArm: Radio failsafe on More than one serial port is set to RC inputPreArm: Multiple SERIAL ports configured for RC input The receiver has not been seen since power-onPreArm: RC not found A stick's calibrated range is too smallPreArm: … radio min too high A stick is off-centre at the moment of armingPreArm: … (RCN) is not neutral Two switches, or a switch and the mode channel, are set to the same jobPreArm: Mode channel and RCN_OPTION conflict The throttle channel reads below the failsafe valuePreArm: … below failsafe The throttle stick is too high to armPreArm: … too high A channel's trim lies outside its minimum and maximumPreArm: RCN_MAX is less than RCN_TRIM The plane is waiting for its receiverPreArm: Waiting for RC The receiver's port is a poor choice, or two telemetry set-ups collide…: passthrough telemetry conflict on SERIALN A switch is set to a function this firmware does not haveInvalid channel option (N)A second serial port is set to RC input and is ignoredSERIALN_PROTOCOL: duplicate RCIN not permitted The radio link reports its speed…: RX device ping failed The receiver's protocol was recognisedRCInput: decoding … (…)A switch on the transmitter changed positionRCN: … …

Compass

The compass in use has stopped sending dataPreArm: Compass not healthy The calibration failed: the compass does not face the way its settings sayMag(N) bad orientation: N/N N.N The calibration failed: the field strength is far from what is expected hereMag(N) bad radius N.N expected N.N The compass calibration would not startCompass cal requires GPS lock Reboot after the compass calibrationPreArm: Compass calibrated requires reboot A compass calibration is in progressPreArm: Compass calibration running The magnetic field the compass measures is too strong or too weakPreArm: Check mag field: N.N, max N, min N The measured field does not match the Earth's field at this placePreArm: Check mag field (z diff:N.N>N)The quick (fixed-heading) compass calibration failedMag: WMM table error A compass that is in use has no calibrationCompass not calibrated A compass on the priority list did not show up at start-upCompass N not found The first compass needs too large a correctionPreArm: Compass offsets too high The compass order was changed: reboot before going onCompass cal requires reboot after priority change The compasses disagree with each otherPreArm: Compasses inconsistent Compassmot ended without a resultFailed The motor interference test (compassmot) would not startRC not calibrated The compass was calibrated without knowing where it isMagCal: No location, fix_radius skipped The log shows the compass dropping out (ERR COMPASS)ERR COMPASS (Subsys 3)A missing compass was dropped from the list, or replaced by a new oneMag: Compass #N with DEVID N removed The calibration confirmed, or corrected, the compass orientationMag(N) good orientation: N N.N In-flight compass learning has started, or finishedCompassLearn: Finished Compassmot is running, or has finishedCalibration successful

GPS

GPS blending is asked for, but this firmware does not have itPreArm: GPS_AUTO_SWITCH==2 but no blending The GPS position and ArduPilot's own position estimate are apartPreArm: GPS and AHRS differ by N.Nm The GPS has no 3D fix yetPreArm: GPS N: Bad fix The two GPS receivers cannot be blendedGPS blending unhealthy The DroneCAN node numbers chosen for the GPS receivers do not fitSelected GPS Node N not set as instance N The position estimator does not trust the GPS right nowPreArm: GPS glitching The satellites in view give too imprecise a positionPreArm: High GPS HDOP The pair of GPS receivers is not giving a headingIncorrect Role set for DroneCAN GPS, N should be Base A configured GPS has never answeredGPS N: was not found The GPS is not sending positions fast and regularly enoughPreArm: GPS N: not healthy The two GPS receivers report different placesPreArm: GPS positions differ by N.Nm ArduPilot's main GPS slot is emptyPreArm: GPS N: primary but TYPE 0 A GPS has not finished being set up by ArduPilotPreArm: GPS N still configuring this GPS The u-blox GPS has not accepted one of ArduPilot's settingsGPS N: u-blox … configuration 0x0x…The u-blox GPS refused to switch a satellite signal on or offGPS N: unable to configure band 0x0x…ArduPilot is checking, and may erase, what is stored in the u-blox GPSGPS N: Requesting all config (…) pos=N A GPS receiver was foundGPS N: probing for … at N baud The u-blox GPS says what it isGPS N: Legacy config unsupported ArduPilot is configuring a newer u-blox GPSGPS N: updating GNSS mode The u-blox GPS is told to remember its settingsGPS N: u-blox saving config

Position and attitude estimate (EKF, AHRS)

The EKF threw the compass heading away and took one worked out from GPSEKF2 IMUN emergency yaw reset The EKF's sensors disagree: the position estimate is no longer trustedEKF variance The chosen estimator is not the one in usenot using configured AHRS type The position and attitude estimate is not ready to flyPreArm: AHRS: …Home has not been set yetPreArm: AHRS: waiting for home The attitude estimate is not ready at the moment of armingPreArm: AHRS not healthy No height estimate yet for a mode that holds heightPreArm: Need Alt Estimate The external AHRS has no GPS fix or has not finished aligningSensAItion Aligning The external AHRS is switched on but not set upExternalAHRS: Invalid backend The external AHRS is not sending good dataVectorNav received VNERR code: …The EKF has no usable attitude yetPreArm: EKF attitude is bad Two attitude estimates disagree… … inconsistent N deg. Wait or reboot One copy of the EKF reports itself unhealthyEKF3 core N unhealthy A plane's EKF will not start without a GPS fixEKF3 init failure: No GPS lock EK3_MAG_CAL still holds a value that older versions used for external yawEK3_MAG_CAL and EK3_SRC1_YAW inconsistent There was not enough memory to start the EKFEKF2 IMUNGSF: allocation failed A sensor disagrees with the EKF too much to armPreArm: EKF velocity variance An EKF source parameter holds a value that is not allowedCheck EK3_SRCN_POSZ The EKF has not finished startingEKF2 not started GPS speed and the EKF's speed differ by more than 2 m/s on the groundEKF3[N] vel error N.N The EKF cannot start until the GPS has been identifiedEKF3 waiting for GPS config data ArduPilot does not yet know where the copter isPreArm: Fence enabled, need position estimate The EKF gave up on one compass and moved to the nextEKF2 IMUN switching to compass N A copy of the EKF was restarted on the groundEKF2 IMUN forced reset The compass was disturbed on the ground; the heading was corrected during the climbEKF2 IMUN MAGN ground mag anomaly, yaw re-aligned The aircraft changed to another copy of the EKFNavEKF2: lane switch N A request to set the EKF origin was refused: it already has oneEKF2 refusing set origin The EKF no longer has a position: it holds attitude and height onlyEKF3 IMUN stopped aiding GPS heading was lost in flight; the EKF fell back on the compassEKF3 IMUN yaw fallback active The EKF switched to another core (ERR EKF_PRIMARY)ERR EKF_PRIMARY (Subsys 24)The transmitter's telemetry warns that a sensor disagrees with the EKFError terrain alt variance Which estimator is supplying attitude and position nowAHRS: … active The EKF set its heading again once clear of the groundEKF3 IMUN MAGN in-flight yaw alignment complete A copy of the EKF has startedEKF3 IMUN initialised The EKF has fixed the point it measures positions fromEKF3 IMUN origin set The EKF started using a position source other than GPSEKF2 IMUN is using range beacons The EKF knows which way is downEKF2 IMUN tilt alignment complete The EKF has started using the GPS: position modes are availableEKF3 IMUN is using GPS The EKF set its heading without the compassEKF2 IMUN yaw aligned using GPS The EKF has taken its first heading from the compassEKF3 IMUN MAGN initial yaw alignment complete

IMU: accelerometers, gyros, vibration

Vibration is spoiling the height estimate; the copter changed how it holds heightVibration compensation ON The accelerometers have no valid calibrationPreArm: 3D Accel calibration needed The accelerometer calibration is saved; reboot before flyingPreArm: Accels calibrated requires reboot The accelerometers of two IMUs disagreePreArm: Accels inconsistent Raw IMU logging was switched on but is not running yetFailed to allocate N bytes for IMU batch sampling The in-flight noise analyser (FFT) is not readyFFT: resolution is N.NHz, increase length A gyro is read too slowly for the main loop rateGyro N rate NHz < loop ratex1.8 NHz The gyros of two IMUs disagreePreArm: Gyros inconsistent The gyros could not find their zero at power-onPreArm: Gyros not calibrated The level calibration was refusedtrim over maximum of 10 degrees No IMU was found at start-upINS: unable to initialise driver An IMU is not delivering dataPreArm: Accels not healthy An IMU temperature calibration is being learnedPreArm: temperature cal running The notch filter settings ask for more filters than the board allowsConfig Error: Too many notches: N > N The FFT tune switch tried to set the notch filter from a hoverFFT: Notch frequency N.NHz and ref N.N selected A gyro filter or the noise analyser could not get its memoryFailed to allocate window for AP_GyroFFT One motor's vibration is getting through the gyro filtersNoise %.fdB on motor N at %.fHz How an IMU is being read (LSM6DSV16X, external AHRS)IMUN: LSM6DSV16X … sampling N.NkHz The level calibration succeededTrim OK: roll=N.N pitch=N.N yaw=N.N The level trim was saved, or an AutoTrim endedTrim saved

Barometer and airspeed

Airspeed and GPS speed disagree: the airspeed sensor is suspectAirspeed sensor N failure. Disabling The airspeed sensor is not readyPreArm: Airspeed N not healthy The EKF's height and the barometer's height differ by more than 1 mPreArm: Altitude disparity No working barometer at start-upConfig Error: Baro: all sensors uncalibrated The barometer's altitude and the GPS altitude are impossibly far apartGPS alt error N.Nm (see BARO_ALTERR_MAX)A barometer is not giving usable readingsPreArm: Baro: …The airspeed sensor does not answerAirspeed N init failed The airspeed zero moved a lot since last time: wind was probably in the tubeArspd N offset change large;cover and recal The barometer stopped giving usable readings (ERR BARO)ERR BARO (Subsys 18)The airspeed sensor's zero was measuredAirspeed N calibrated, offset = N.N The barometer was zeroed at start-upBaro: no sensors found, skipping calibration The height of the take-off field above sea level was set, or could not beField Elevation Set: N.Nm The barometer's ground level was set againBarometer calibration complete

Battery and power

The battery failsafe has triggeredBattery N is … N.NV used N.N mAh A battery failsafe from the last flight is still setPreArm: Battery failsafe The flight controller's own 5 V supply is too low or too highPreArm: Board (N.Nv) out of range N.N-N.Nv The servo rail voltage is below the limit you setPreArm: Servo voltage to low (N.Nv < N.Nv)A battery monitor refuses armingBattery N …The battery is already at a failsafe level The battery is below the level set as the minimum to arm The critical battery threshold is not below the low one No analog input is left for the battery monitorConfig Error: No analog voltage channel for battery N A battery monitor is switched on but gives no reading A smart battery says it is switching offVehicle N battery N is powering off Notices from a DroneCAN battery or solar chargerBattery N: Node change from N to N for Id N

Failsafes and emergencies in flight

Crash detected: the motors were stoppedCrash: Disarming: AngErr=N.N>N.N, Accel=N.N<N.N Dead reckoning: flying on an estimated position, without GPSERR FAILSAFE_DEADRECKON (Subsys 31)The dead-reckoning script: flying home without GPSDR: could not get home or vehicle location Avoiding a manned aircraft (ERR FAILSAFE_ADSB)ERR FAILSAFE_ADSB (Subsys 20)Loss of control: the parachute was released (ERR CRASH_CHECK-2)ERR CRASH_CHECK-2 (Subsys 12, ECode 2)The EKF stopped agreeing with its sensors (ERR EKFCHECK)ERR EKFCHECK (Subsys 16)EKF failsafe: the position estimate is no longer trustedEKF Failsafe A fence was crossed (ERR FAILSAFE_FENCE)ERR FAILSAFE_FENCE (Subsys 9)No frame from the receiver in time (ERR RADIO-2)ERR RADIO (Subsys 2)Thrust loss: full throttle and still descending (ERR THRUST_LOSS_CHECK-1)ERR THRUST_LOSS_CHECK (Subsys 25)Vibration failsafe: height is being held in a cruder way (ERR FAILSAFE_VIBE)ERR FAILSAFE_VIBE (Subsys 29)Battery failsafe: land nowERR FAILSAFE_BATT (Subsys 6)A failsafe triggered, but the copter carries on with what it was doing The ground station went silent: the copter is acting on its ownERR FAILSAFE_GCS-1 (Subsys 8, ECode 1)Radio link lost: the copter is acting on its ownERR FAILSAFE_RADIO-1 (Subsys 5, ECode 1)SmartRTL could not start: falling back to RTL or LandSmartRTL Unavailable, Trying RTL Mode Terrain failsafe: the height above ground is no longer knownFailsafe: Terrain …The failsafe's first choice was refused: falling back to RTL or LandTrying Land Mode The aircraft crossed a fence The EKF no longer trusts the GPS (or the heading is wrong)GPS Glitch or Compass error Another aircraft is close: the plane is avoiding itAvoid: Performing action: N The Advanced Failsafe is ending the flight on purposeTerminating due to fence breach Plane decided it has crashed or landed hardHard landing detected Long failsafe: the radio or the ground station stayed lost… Failsafe On: switched to …The parachute was releasedParachute: Released again Short failsafe: the first seconds after the radio is lostRC Short Failsafe: switched to …The radio link was lost (“on”) or has come back (“off”)Throttle failsafe …RTL lost the ground height and started again at a height above homeRestarting RTL - Terrain data missing RTL could not work out its pathRTL: unexpected error setting climb target A flight termination was asked for and not done, or called offUnable to terminate, termination is not configured The ground station asked for the parachute and Plane refusedParachute already released FS_GCS_ENABLE is set to 2, a value that no longer existsPreArm: FS_GCS_ENABLE=2 removed, see FS_OPTIONS A failsafe came while on the ground: the motors were stopped RTL wanted a height above ground and is using a height above homeRTL: no terrain data, using alt-above-home The ground station is heard againGCS Failsafe Cleared The radio link is back, but the copter keeps the failsafe modeRadio Failsafe Cleared Back inside every fenceFence breach cleared The fence stands back for 10 s after a mode changeManual recovery started The EKF trusts the GPS againGlitch cleared The Advanced Failsafe changed stateAFS State: GPS_LOSS

Flight modes

Auto refused: armed on the ground and the mission does not begin with a take-offAuto: Missing Takeoff Cmd AUTO RTL refused: the mission has no return path or landing sequenceMode change to AUTO RTL failed: No landing sequence found Follow mode is switched offSet FOLL_ENABLE = 1 The flight mode change was refusedMode change to … failed: …The ground station is not allowed to select this modeGCS entry disabled (FLTMODE_GCSBLOCK)Mode changes are locked while the copter recovers from a fence breachin fence recovery A stick-flown mode cannot be entered while the radio is in failsafein RC failsafe The mode's own start-up check said noinit failed This mode holds height itself, and there is no height estimateneed alt estimate This mode needs a position estimate, and there is nonerequires position The throttle stick is too high to switch to a manual-throttle mode on the groundthrottle too high AUTOLAND: the landing direction, and why the mode can refuseMust already be flying!The mode change was refused, and the message says whyMode change to … denied, GCS entry disabled (FLTMODE_GCSBLOCK)The new flight mode refused to startFlight mode change failed A flight mode was asked for that this firmware does not haveNo such mode N This mode cannot be paused or resumedFlight Mode Pause failed SmartRTL has stopped recording the way backSmartRTL deactivated: init failed SmartRTL was left part-way and one point of the return path was lostSmartRTL: lost one point The recorded way back is nearly fullSmartRTL Low on space!A flip was abandoned (ERR FLIP-2)ERR FLIP (Subsys 13)Follow took the present distance to the lead vehicle as its offsetRelative follow offset loaded Simple or Super Simple mode was switchedSIMPLE mode off Throw mode: from the hand to a steady hoverheight achieved - controlling position Turtle mode is waiting for the throttleTurtle: raise throttle to arm ZigZag mode: storing the two ends of the line and flying between them…: moving to … (line N/N)

Motors, ESCs and outputs

Full throttle and still sinking: a motor may have failedPotential Thrust Loss (N)The engine stopped by itself, or would not startEngine max crank attempts reached FRAME_CLASS names a helicopter, but this is multicopter firmwarePreArm: Invalid MultiCopter FRAME_CLASS The motor setup is not completePreArm: Motors: …The throttle was high at power-on: ArduPilot waits for a restartESC calibration: Restart board The FETtec OneWire ESCs are not readyN of N ESCs are not sending telemetry The board's output co-processor is not working properlyPreArm: IOMCU is unhealthy The motor test was refused: the copter is not ready for it…: Board initialising The motor test was refused: the outputs are blocked…: Motor Emergency Stopped The motor test was refused: the radio is not calibrated…: RC not calibrated ArduPilot does not know what frame this isCheck frame class and type A motor of this frame has no outputno SERVOx_FUNCTION set to MotorN The motor output range is not validCheck …PWM_MIN and …PWM_MAX The armed idle speed is above the in-flight minimum…SPIN_ARM > …SPIN_MIN The minimum motor speed in flight is set too high…SPIN_MIN too high N.N > 0.3 The tricopter's tail servo has no outputno SERVOx_FUNCTION set to Motor7 for tail servo A PiccoloCAN ESC or servo is missing or inhibitedESC N not detected A command to start the engine was refusedEngine: start control disabled Reboot refused: it would start an automatic ESC calibrationReboot rejected, ESC cal on reboot A servo command was refused: that output belongs to something elseServoRelayEvent: Channel N is already in use A PWM device is on an output that DShot or an LED strip has taken overPreArm: SERVON_FUNCTION=N on disabled channel An output's trim lies outside its minimum and maximumPreArm: SERVON_MIN is greater than SERVON_TRIM Take-off is held back until the motors are seen to spin… ESC RPM out of range The flight controller is in ESC calibration, not in normal operationESC calibration: Passing pilot throttle to ESCs These outputs cannot produce DShot or drive an LED stripChan N to N, …: …The engine went above its maximum RPMEngine: Above redline RPM The copter is using most of its yaw authority only to hold its headingYaw Imbalance N.N%An ESC bus driver reported at start-upFTW using Half-Duplex A test of the configuration link to one ESCESC: Test …The motor test started, finished or was cut shortstarting motor test The combustion engine is being started or stoppedTakeoff height set to N.Nm

Missions, fence, rally points, terrain

No route around the fences could be worked outDijkstra: …RTL is set to fly above the terrain, and has no way to measure itPreArm: no rangefinder The fence's altitude limits contradict each otherInvalid FENCE_ALT_MIN value The fence is switched on, but no fence existsFences enabled, but none selected The fence margin or a circle's radius is wrongInvalid FENCE_MARGIN value The drawn fence stored on the aircraft could not be loadedPolygon fence(s) invalid The fence is on, but there is no position to check it againstFence requires position The aircraft refused the fence the ground station sentReceived incorrect type (want=N got=N)The aircraft is already outside the fence on the groundVehicle breaching …The mission lacks an item that is required for armingPreArm: Missing mission item: …The mode is Auto, but there is no mission to flyPreArm: No mission library present A rally point is required, and none is close enoughPreArm: Can't check rally without position The mission or fence file on the SD card could not be openedPreArm: Failed to open fence storage Path planning around obstacles needs a reboot to startOA requires reboot The mission has a landing marker, but RTL is not told to use itPreArm: DO_RETURN_PATH_START set and RTL_AUTOLAND disabled No memory for the terrain databaseTerrain: Allocation failed The terrain files on the SD card are from before a correctionterrain data expired, possible errors The flight needs terrain heights, and the terrain database is offTERRAIN_SPACING can't be <= 0 Terrain heights for this flight have not all arrived yetwaiting for terrain data The mission was changed while the copter was flying itAuto mission changed but failed to restart command The mission holds a command this firmware cannot carry outSkipping invalid cmd #N A mission command needed the ground height, and it was not availablebad do_loiter_to_alt A navigation target could not be used (ERR NAVIGATION)ERR NAVIGATION (Subsys 22)This way of switching the fence on by itself is being retiredFENCE_AUTOENABLE is N, will be removed in 4.7, use 3 The aircraft is close to a fence… in N.Nm A ground station is using the old way of sending fencesInvalid fence point, bad count (N vs N)An upload of a mission, fence or rally points did not finishFence upload timeout The mission has no landing approach to jump toUnable to start find a landing abort sequence Payload place gave up without releasing the load… PLDP_RNG_MAX set and rangefinder not enabled The terrain data and the aircraft disagree about the height of the take-off spotTerrain: clamping offset N.N to N.N The mission is moving onDelaying N sec A fence was switched on or offMin Alt fence enabled (auto enable)The whole mission arrived and was storedFlight plan received The stored mission was erased at start-upClearing Mission A mission command has startedMission: N … N The mission jumped to its landing approach or its way backReturn path started A resumed mission repeats the last stretch of its routeMission: Returned to interrupted WP A failsafe let the mission go on, because the landing is closer that wayRejecting RTL: closer land if mis continued Payload place: the stages of setting a load down… payload release thrust threshold: N.N A loiter command in the mission is finishedLoiter orbits complete The mission ran out of commands: the plane returns homeReached RTL location A change-speed command was appliedSet throttle N A mission waypoint is donePassed waypoint #N dist Nm

Plane: take-off, landing, QuadPlane

The VTOL takeoff was abandoned: airspeed above the takeoff limitFailed to complete takeoff, excessive wind The automatic VTOL takeoff took too long and was abandonedFailed to complete takeoff within time limit The lift motors are at full power and the aircraft is still sinkingPotential VTOL Thrust Loss (N)The aircraft did not reach flying speed in the time allowedTransition failed, exceeded time limit The landing type is one this firmware cannot flyLanding configuration error, invalid LAND_TYPE The launch was felt and then rejected: the motor stays stoppedTimeout AUTO The take-off was given up: the plane never reached 4 m/sTakeoff timeout: N.N m/s speed < 4m/s Q_ANGLE_MAX is outside 10° to 80°PreArm: Check Q_ANGLE_MAX The airspeed for lift-motor assistance has not been chosenPreArm: Q_ASSIST_SPEED is not set AUTO will not arm: the mission is not at a VTOL takeoffnot in VTOL takeoff Q_ENABLE is on, but the VTOL code has not startedPreArm: Quadplane enabled but not running The lift-motor layout in Q_FRAME_CLASS is not supportedConfig Error: Unsupported Q_FRAME_CLASS N Forward throttle in Q modes is switched on for a tailsitterPreArm: set Q_FWD_THR_USE to 0 The takeoff command from the ground station was refusedUser Takeoff only in GUIDED mode The last waypoint is too close to the VTOL landing pointPreArm: VTOL land too short, min N.Nm The main loop is too slow for a QuadPlanePreArm: quadplane needs SCHED_LOOP_RATE >= 100 The lift-motor test was refusedMust be disarmed for motor test A VTOL function was asked for, but the VTOL code is not runningVTOL not available Too little free memory to start the QuadPlane codeConfig Error: Not enough memory for quadplane Two settings both decide how RTL endsPreArm: unset one of RTL_AUTOLAND or Q_RTL_MODE Tailsitter or tiltrotor was enabled after start-upPreArm: tailsitter setup not complete, reboot Tailsitter and tiltrotor are both enabledPreArm: set TAILSIT_ENABLE 0 or TILT_ENABLE 0 Takeoff is waiting for the rudder stick to be centredTakeoff waiting for rudder release The VTOL transition command was refusedVTOL transition only in AUTO The landing was broken off: the plane goes aroundLanding aborted, climbing to Nm The landing could not be started again; the plane goes to RTLUnable to restart landing sequence The lift motors started because the aircraft was too lowAlt assist N.Nm The lift motors started because the aircraft was badly out of attitudeAngle assist r=N p=N The landing approach was cut short: the aircraft could not hold its speedVTOL pos1 low speed as=N.N at=N.N Lift-motor ESC calibration is running: stabilisation is offStarting ESC calibration The aircraft flew past the landing point, or is pointing away from itVTOL Overshoot d=N.N cs=N.N yerr=N.N A tailsitter's transition was cut short by roll or by timeTransition VTOL done, roll error Disarmed by itself after the automatic landingAuto disarmed Automatic take-off: the launch was felt, then the motor was releasedTriggered AUTO. GPS speed = N.N FBWA take-off help for tail-wheel planes switched on or offFBWA tdrag off The automatic landing has begunLanding approach start at N.Nm The flare began, and where the plane ended upDistance from LAND point=N.Nm The rangefinder took over, or gave up, the height for landingRangefinder engaged at N.Nm The landing will be flown again, and from whereRestarted landing via DO_LAND_START: N A switch changed reverse thrust, crow flaps or terrain followingNON AUTO TERRN: …A switch changed QuadPlane assistanceQAssist: Force enabled The soaring system reports what it is doingSoaring: Enabled, automatic mode changes.TAKEOFF mode says what it is going to doClimbing to TKOFF alt then loitering Steps of an automatic take-offHolding course N at N.Nm/s (N.N)The QuadPlane code started, with this motor layoutQuadPlane initialised, …Leaving the circle to fly the approach line into the windStarting VTOL land approach path The stages of the approach to a VTOL landingVTOL position2 started v=N.N d=N.N h=N.N The aircraft has detected that it is on the groundLand complete The vertical descent has begun, then its slow last partLand descend started The mission switched between multicopter and fixed-wing flightEntered VTOL mode A tailsitter has finished turning nose-up to hoverTransition VTOL done, zero throttle The transition to flying on the wing has finishedTransition airspeed reached N.N The lift motors are carrying the aircraft while it gains airspeedTransition started airspeed N.N

AutoTune and control

The Acro levelling rate is larger than the angle gainPreArm: Check ACRO_BAL_ROLL/PITCH The maximum lean angle is outside 10° to 80°…_ANGLE_MAX must be >= 10 and <= 80 An attitude controller gain is zero or negative…_…_D must be >= 0 AutoTune gave up: it could not find a gainAutoTune: Angle P Gain Determination Failed AutoTune gave up: the aircraft would not settle levelAutoTune: Failed to level, please tune manually AutoTune did not startAutoTune: failed yaw allocation Saving the trims from the switch was refusedtrim failed, large roll and pitch input A position controller gain is zero or negative…_POSZ_P must be > 0 SystemID mode would not startAxis requires switch from Loiter AutoTune could not measure D on this axis and left it at the minimumAutoTune: Min Rate D limit reached Quicktune stopped, or would not startQuicktune: attitude error N.Ndeg - ABORTING The QuikTune script stopped, or would not startTuning: attitude error N.Ndeg - ABORTING The system identification test stopped before its endSystemID Parameter Error AutoTrim was started by holding the yaw stick while armingAutoTrim start AutoTune finished an axis: the gains it foundAutoTune: … Angle P:N.N, Max Accel:N.N AutoTune's gains were saved, tried or put backAutoTune: must be complete to test gains AutoTune is paused because a stick is off centreAutoTune: Paused: Pilot Override Active What AutoTune is testing right nowAutoTune: Updating Gains AutoTune began its tests, or stopped themAutoTune: Started AutoTune finished every axisAutoTune: Success Fixed-wing AutoTune started, finished an axis, or stoppedStopped autotune The stick and servo trims were savedtrim complete Plane's in-flight tuning knob changed, saved or reverted a valueTuning: reverted Quicktune is tuning the QuadPlane's hover gainsQuicktune: Saved The QuikTune script is tuning the hover gainsTuning: starting tune A system identification test started or finishedSystemID Starting: axis=N The aircraft is turning itself into the windWeathervane Active: …

Logging and storage

A log download is in progressPreArm: Downloading logs The flight log cannot be writtenPreArm: No SD card No log file could be opened at the moment of armingPreArm: Logging not started LOG_BACKEND_TYPE asks for logging this board cannot doConfig Error: Too many logger backends A request to download logs was refusedDisarm for log download The firmware expects a parameter that is not in this buildConfig Error: param deflt fail:…The logging code found its own books out of orderInternal errors 0x1 (logger_mapfailure)One log has filled the whole on-board flash chipChip full, logging stopped A dump of an earlier firmware crash was savedSaved crash_dump.bin The folder for the logs could not be created on the cardFailed to create log directory … : …The on-board log chip is being erased or repairedChip erase complete The part of ArduPilot that writes the log is stuckAP_Logger: IO thread died All stored parameters were erasedAll parameters reset, reboot board A parameter could not be changed from outsideParam write denied (…)The mission kept on the microSD card could not be savedMission storage failed An error subsystem that Copter and Plane do not writeERR MAIN (Subsys 1)Notes ArduPilot writes at the start of a logNew mission The card or the on-board flash is being formattedFormat flash: Failed (N)

Board, internal errors, CAN, scripting

The main loop stopped for 2 secondsERR CPU (Subsys 19)The log recorded an internal errorERR INTERNAL_ERROR (Subsys 30)An IMU keeps sending damaged dataInternal errors 0x1000000 (imu_reset)The board's second processor restarted or stopped answeringInternal errors 0x1000 (iomcu_reset)The main loop stood still for half a secondInternal errors 0x8000 (main_loop_stuck)A calculation produced something that is not a numberInternal errors 0x400 (constraining_nan)The firmware stopped itself: it could not go onInternal errors 0x20 (panic)A chip on the board did not answer in timeInternal errors 0x4000 (spi_fail)A part of the firmware almost ran out of its own memoryInternal errors 0x800000 (stack_overflow)The processor was restarted by its watchdogForcing logging for watchdog reset The board restarted itself while armed; arming checks are skippedWatchdog: resume WP N A Lua script has to allow arming, and has notPreArm: Too many auxiliary authorisers A device on the CAN bus stops armingPreArm: DroneCAN: …The firmware crashed earlier and left a crash dumpCrash Dump incomplete, dumping what we got!No memory was left at start-up for terrain data or ADS-BPreArm: ADSB out of memory An input pin is flooded with pulses and has been switched offPin N disabled (ISR flood)ArduPilot caught itself in a state that should never happenInternal Errors 0x0x…The processor cannot keep up with the main loopPreArm: Main loop slow (NHz < NHz)The parameters cannot be savedPreArm: parameter storage full Two different CAN devices claim the same node numberDuplicate Node …../N!A CAN device says it is not healthyNode N unhealthy!A calibration was asked for while armedDisarm to allow calibration An orientation parameter holds a number that is not an orientationInternal errors 0x400000 (bad_rotation)The scripts on board are not the ones that were approvedScripting: loaded CRC incorrect want: 0x0x…Lua scripting reports a problem and blocks armingScripting: …A serial option has moved to the MAVLink link in 4.7SERIALN_OPTIONS bit 10 ('no forward mavlink') must not be set; use MAVn_OPTIONS bit 1 instead The table of CAN node numbers is full, or was clearedDroneCAN DNA allocation failed; database full File transfer over the telemetry link is not availableFTP disabled The ground station speaks an older dialect of MAVLinkgot MISSION_REQUEST; use MISSION_REQUEST_INT!A message was asked for more often than ArduPilot can send itRequested rate for message ID N too fast. Increase SCHED_LOOP_RATE The MAVLink signing key could not be setERROR: Won't setup signing when armed A pin or a data channel of the processor misbehavedInternal errors 0x2000000 (gpio_isr)An I2C bus was flooded with interruptsInternal errors 0x80000 (i2c_isr)The parameters were restored from the backup copyInternal errors 0x10000000 (params_restored)The code reached a place it should never reachInternal errors 0x100000 (flow_of_control)ArduPilot found no place to load scripts from, or no scriptsLua: open directory (…) failed A Lua script stopped with an errorError: …A script uses something this 4.7 firmware does not offerWarning: userdata creation does not take arguments, will be fatal in future The Lua scripts do not have enough memoryInsufficent memory loading …The Lua script engine stopped, restarted or could not startScripting: …A Lua script ran for too long in one go… exceeded time limit A health flag, put into words for the transmitter's screenBad GPS Health Main loop timing, printed because SCHED_DEBUG is onPERF: N/N [N:N] F=NHz sd=N Ex=N A message from a CAN device itselfCAN[N] …A serial port now works as an adapter to the CAN busCANManager: Starting SLCAN Passthrough on Serial N with CANN High-latency telemetry was switched on or offHigh Latency …Two serial ports are joined straight throughPassthru disabled Lines from the network connectionNET: Failed to allocate buffers The fast attitude loop changed its rateRate CPU …, rate set to NHz Stand-by was switched on or offStand By Enabled Toy mode: messages of the SkyViper toy coptersTmode: throttle arm

Rangefinder, optical flow, camera, OSD and other devices

A device that is switched on in the parameters is not readyPreArm: FETtec: …The proximity sensor sees something within 0.6 mPreArm: Proximity N deg, N.Nm (want > N.Nm)The pin of a button or an RPM sensor cannot be usedBTN_PINN=N, set SERVON_FUNCTION=-1 The hydrogen fuel cell is not running, or stopped answeringGenerator: IE using … protocol A Loweheiser or Cortex generator is not ready for flightLH: Generator warming up (waiting for data)The RichenPower generator is not ready for flightrequested state is not RUN The generator is switched on or off in the parameters, but not in the running systemGenerator: No serial port found A gimbal type is set, but its driver did not startcheck TYPE A menu is open on the video screenIn OSD menu Two OSDs are set, but only one could startOSD_TYPE2 not compatible with first OSD The parachute has been released since power-onChute is released The parachute is enabled, but nothing is set up to release itChute has no relay A proximity sensor is not sending distancesPRXN: Not Connected A rangefinder's driver is running, but no readings arriveRangefinder 0x…: Not Connected A rangefinder is switched on in the parameters, but no driver started for itRangefinder 0x…: Not Detected The rangefinder's input pin is not set, or cannot be usedRNGFNDN_PIN=N, set SERVON_FUNCTION=-1 A relay's pin cannot be used, or two relays share one pin…=N invalid The RunCam camera has not answered yetRunCam device not found Surface tracking has no rangefinder pointing that waySurfaceTracking: no upward rangefinder The tracking camera (visual odometry) is not ready or disagrees with the attitudeyaw diff N.N deg (>10)The winch is enabled, but not workingwinch unhealthy The ADS-B receiver's driver could not startADSB: Unable to initialize ADSB driver The ADS-B unit stopped answering or reports a failureADSB: Transceiver heartbeat timed out A pulse input cannot be read on the pin you chose…: Failed to detach interrupt from N The camera did not start or stop recording when the aircraft armedCamera: failed to … recording The engine's fuel-injection type is not one this firmware knowsUnknown EFI type The optical-flow calibration rejected its result… scalar…:N.N too low (<N.N)The optical flow calibration ran out of time A Topotek or XFRobot gimbal camera could not do what was asked… tracking failed The gimbal driver refused a commandMount: …The point the camera looks at could not be worked outPOI: distance > 5km: N.N m A Siyi gimbal camera could not record, or its firmware is oldSiyi: can't start recording: No Card A Xacti gimbal camera reports an error… time …set The store of obstacles for path planning was not set upDB init failed . Sizes queue:N, db:N The digital OSD has no serial port to talk throughMSP backend not available The OSD font could not be loadedOSD: Failed to load font N A manual parachute release was refusedParachute: Too low The landing target is sent in a coordinate frame ArduPilot does not acceptPlnd: Frame not supported Precision landing saw its target: the first lock failed, or succeededPrecLand: Init Complete The copter is trying again to find the landing target, or has given upPrecLand: Retry Completed Precision landing can no longer see its targetPrecLand: Target Lost A DroneCAN proximity sensor has no range setConfigure PRXN_MIN and PRXN_MAX A Benewake lidar on I2C answered, but cannot be usedTFS20L: No response from sensor The radar altimeter reports a fault of its ownRangeFinder: Temperature alert An I2C temperature sensor did not answer at start-up… reset failed The winch was told to move, and the line is not moving… unstuck The ADS-B unit was found, or its settings changedADSB:Detected … vN.N.N SN:N …A button wired to the flight controller did its jobButton N: executing (… …)A camera answered and described itselfCamera: … … fw:N.N.N.N A rangefinder or proximity sensor was foundRPLidar: (…)The optical-flow calibration is running or has finishedFlowCal: Started The gripper was told to close or openGripper load grabbing The landing gear was told to go down or upLandingGear: RETRACT A mission command closed or opened the gripperGripper Released The gimbal camera reports what it is doing… get/set … res:N The gimbal answered and reported its model and firmwareMount: Siyi zoom fw vN.N.N The gimbal's point-of-interest lock changed statePOI: Cleared Precision landing has picked up its targetPrecLand: Target Found The video transmitter was found; these are its settingsVTX: …N NMHz, PWR: NmW The winch reports what it is doing… move state unknown