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C31 Agricultural Drone Troubleshooting Manual (V1.0)

Avionics System

IMU Reporting Abnormalities

Fault Symptoms:

  1. Audible alert from the remote controller: “IMU not calibrated”
  2. Remote controller display shows IMU1 / IMU2 not calibrated

Possible Causes:

  1. Typically occurs after replacing the avionics assembly or interface board
  2. May also occur if the aircraft has not been powered on for an extended period

Troubleshooting Procedure:

  1. Place the aircraft on a level surface
  2. Ensure the environment is free of vibration and strong magnetic interference
  3. On the remote controller, navigate to:
    Aircraft Settings → Advanced Settings → IMU Calibration, and perform IMU calibration

GNSS Reporting Abnormalities

Fault Symptoms:

  1. Audible Warnings:
    1. Remote controller voice alert: “Dual-antenna heading abnormal”
  2. Visual Warnings:
    1. Weak GPS signal indication
    2. Satellite icon turns red or yellow
    3. Low number of satellites detected
    4. Positioning status icon flashing (e.g., green → red)
  3. Before Takeoff:
    1. The Applicator View App by Ceres Air indicates “Insufficient satellites, unable to take off” or “GPS not ready”
  4. During Flight:
    1. Aircraft drifting
    2. Unstable altitude
    3. Tendency toward loss of control

Possible Causes:

  1. Environmental Factors:
  2. Signal obstruction around the aircraft (e.g., high-rise buildings, indoor environments, dense forest canopy)
    1. Weather Interference:
      1. Thunderstorms or ionospheric disturbances affecting signal transmission
    2. Electromagnetic Interference:
      1. Operation near high-voltage power lines, communication base stations, radar installations, or other strong electromagnetic sources
    3. Hardware Factors:
      1. Physical damage to antennas (e.g., impact damage from a crash)
      2. Loose antenna connectors or damaged antenna cables

Troubleshooting Procedure:

  1. Before flight, confirm the operating area is open and unobstructed
  2. Pause flight operations and wait for weather conditions to stabilize
  3. Fly away from known interference sources
  4. Inspect antenna condition and cable connections; replace damaged components as necessary

Avionics Indicator Light Definitions

Propulsion System

Motor and Mechanical Failures

Fault Symptoms:

  1. Rough or restricted rotation, accompanied by a grinding or scraping noise
  2. Severe vibration during motor startup, with the motor unable to rotate normally
  3. Visible motor housing deformation, leading to bearing wear or damage

Possible Causes:

  1. Sand, dust, or foreign objects entering the motor interior
  2. Impact, compression, or collision during flight or transportation, causing motor housing deformation
  3. Troubleshooting Procedure:
    1. Promptly clean foreign objects from the motor interior
    2. Replace the motor if mechanical damage or deformation is detectedCauses of failure:

Motor Overheating

Fault Symptoms:

  1. Motor housing is too hot to touch, with the remote controller indicating a temperature exceeding 140 °F (60 °C)
  2. Presence of a burnt or scorched odor from the motor

Possible Causes:

  1. Prolonged operation under overload conditions, such as heavy payloads, high RPM, or high ambient temperatures

Troubleshooting Procedure:

  1. Land immediately and allow the motor to cool down
  2. Inspect the motor windings for discoloration or deformation
  3. Reduce payload and monitor motor temperature during subsequent flights

Propeller Faults

Fault Symptoms:

  1. Severe vibration during flight with a noticeable increase in noise
  2. Unstable hover with irregular lateral drift
  3. Visible propeller damage, including cracks, delamination, or deformation
  4. Possible Causes:
    1. Impact or compression during operation or transportation, resulting in propeller deformation
    2. Improper installation, such as insufficient tightening of propeller clamp bolts, causing centrifugal imbalance
    3. Surface contamination, including mud, pesticide residue, or corrosive chemical buildup

Troubleshooting Procedure:

  1. Replace propellers with new units

⚠️ C31 propellers must be replaced in matched pairs

  1. Verify propeller clamp bolt torque
  2. Clean propeller surfaces to remove dirt and chemical residue

Power Unit Communication Failure

Fault Symptoms:

  1. After power-on, the ESC status LED on the affected arm displays a purple color
  2. On the remote controller interface, under Propulsion System Status, the affected arm is shown as “Not Recognized”
    1. (Example: Arm No. 2)

Possible Causes:

  1. The flight controller is not receiving communication signals from the ESC

Troubleshooting Procedure:

  1. Verify that all related wiring harnesses are properly connected, fully seated, and undamaged
  2. Check connectors for looseness, bent pins, or corrosion
  3. If the issue persists, replace the motor and/or ESC on the affected arm

Loose or Disconnected Wiring Harness Conditions

This section describes typical fault symptoms caused by loose or disconnected wiring harnesses. Different harness faults may result in specific LED indications, system status messages, and subsystem recognition failures.

Flight Controller / CAN Bus Harness is loose

Fault Symptoms:

  1. Navigation LEDs on Arms 1–4 remain solid purple
  2. Control signals lostRemote controller cannot connect to
  3. the aircraft

Troubleshooting Procedure:

  1. Verify that all related wiring harnesses are properly connected, fully seated, and undamaged
  2. Check connectors for looseness, bent pins, or corrosion

Battery Signal Harness – Loose

Fault Symptoms:

  1. Navigation LEDs on Arms 1–4 remain solid purple
  2. Remote controller cannot connect to the aircraft

Troubleshooting Procedure:

  1. Verify that all related wiring harnesses are properly connected, fully seated, and undamaged
  2. Check connectors for looseness, bent pins, or corrosion

Downward Radar Harness – Loose:

Fault Symptoms:

  1. Remote controller connects normally
  2. Radar System displays “Downward Radar Not Recognized”

Troubleshooting Procedure:

  1. Verify that all related wiring harnesses are properly connected, fully seated, and undamaged
  2. Check connectors for looseness, bent pins, or corrosion

Arm No. 1 Harness – Loose

Fault Symptoms:

  1. ESC LED indicators:
    1. Arm 1: Purple
    2. Arm 2: Red
    3. Arms 3 & 4: Green
  2. Power System displays Motors No. 1 and No. 5 Not Recognized:

Troubleshooting Procedure:

  1. Verify that all related wiring harnesses are properly connected, fully seated, and undamaged
  2. Check connectors for looseness, bent pins, or corrosion

Arm No. 2 Harness – Loose

Fault Symptoms:

  1. ESC LED indicators:
    1. Arm 2: Purple
    2. Arm 1: Red
    3. Arms 3 & 4: Green
  2. Power System displays Motors No. 2 and No. 6 Not Recognized

Troubleshooting Procedure:

  1. Verify that all related wiring harnesses are properly connected, fully seated, and undamaged
  2. Check connectors for looseness, bent pins, or corrosion

Arm No. 3 Harness – Loose

Fault Symptoms:

  1. ESC LED indicators:
  2. Arm 3: Purple
  3. Arms 1 & 2: Red
  4. Arm 4: Green
  5. Power System displays Motors No. 3 and No. 7 Not Recognized

Troubleshooting Procedure:

  1. Verify that all related wiring harnesses are properly connected, fully seated, and undamaged
  2. Check connectors for looseness, bent pins, or corrosion

Arm No. 4 Harness – Loose

Fault Symptoms:

  1. ESC LED indicators:
    1. Arm 4: Purple
    2. Arms 1 & 2: Red
    3. Arm 3: Green
  2. Remote controller connects normally
  3. Power System displays Motors No. 4 and No. 8 Not Recognized

Troubleshooting Procedure:

  1. Verify that all related wiring harnesses are properly connected, fully seated, and undamaged
  2. Check connectors for looseness, bent pins, or corrosion

Front camera harness - Loose

Fault Symptoms:

  1. Remote controller connects normally
  2. Vision System displays “Front Camera Not Connected”

Flight Controller PWM1 Harness - Loose

Fault Symptoms:

  1. ESC status:
    1. Arms 1–3: ESC fault
    2. Arm 4: ESC normal
  2. ESC LED indicators:
    1. ESCs No. 1–6: Purple
    2. ESCs No. 7 & 8: Green
  3. Remote controller connects normally
  4. Power System displays Motors No. 1–6 Not Recognized

Troubleshooting Procedure:

  1. Verify that all related wiring harnesses are properly connected, fully seated, and undamaged
  2. Check connectors for looseness, bent pins, or corrosion

Flight Controller PWM2 Harness – Loose

Fault Symptoms:

  1. ESC status:
    1. Arm 4: ESC fault
    2. Arms 1–3: ESC normal
  2. ESC LED indicators:
    1. Arms 1 & 2: Red
    2. Arm 3: Green
    3. Arm 4: Purple
  3. Remote controller connects normally
  4. Power System displays Motors No. 7 and No. 8 Not Recognized

Troubleshooting Procedure:

  1. Verify that all related wiring harnesses are properly connected, fully seated, and undamaged
  2. Check connectors for looseness, bent pins, or corrosion

Flight Controller Perception / Ethernet Harness – Loose

Fault Symptoms:

  1. Remote controller connects normally
  2. Vision System and Radar System not recognized
  3. Vision System displays “Front Camera Not Recognized”

Troubleshooting Procedure:

  1. Verify that all related wiring harnesses are properly connected, fully seated, and undamaged
  2. Check connectors for looseness, bent pins, or corrosion

Rear Radar Harness – Loose

Fault Symptoms:

  1. Remote controller connects normally
  2. Radar System displays “Rear Radar Not Recognized”

Troubleshooting Procedure:

  1. Verify that all related wiring harnesses are properly connected, fully seated, and undamaged
  2. Check connectors for looseness, bent pins, or corrosion

Payload Control (Lifting Module) Harness – Loose

Fault Symptoms:

  1. Remote controller connects normally
  2. Lifting System displays “Not Recognized”

Troubleshooting Procedure:

  1. Verify that all related wiring harnesses are properly connected, fully seated, and undamaged
  2. Check connectors for looseness, bent pins, or corrosion

Front Radar Harness – Loose

Fault Symptoms:

  1. Remote controller connects normally
  2. Radar System displays “Rotating Radar Not Recognized”

Troubleshooting Procedure:

  1. Verify that all related wiring harnesses are properly connected, fully seated, and undamaged
  2. Check connectors for looseness, bent pins, or corrosion

Front / Rear Power Distribution Board Signal Harness – Loose

Fault Symptoms:

  1. Battery cannot detect load
  2. Aircraft cannot power on
  3. Red indicator LED flashes briefly and then turns off

Troubleshooting Procedure:

  1. Verify that all related wiring harnesses are properly connected, fully seated, and undamaged
  2. Check connectors for looseness, bent pins, or corrosion

Front Power Distribution Board Front/Rear Power Harness – Loose

Fault Symptoms:

  1. ESC indicators on the affected ports do not illuminate
  2. Power System displays corresponding motors as “Not Recognized”

Troubleshooting Procedure:

  1. Verify that all related wiring harnesses are properly connected, fully seated, and undamaged
  2. Check connectors for looseness, bent pins, or corrosion

Vision system

Image Transmission (Video Link) Failure

Fault Symptom:

  1. The remote controller displays a warning: “Vision System Fault – Image Transmission Not Detected.”

Possible Causes:

  1. Damaged image transmission antenna (bent, broken, or physically damaged)
  2. Loose antenna connection or poor electrical contact

Troubleshooting Steps:

  1. Inspect the image transmission antenna for damage
  2. Tighten the antenna connection securely
  3. Replace the image transmission antenna if damage is found

Front Camera Failure

Fault Symptoms:

  1. The remote controller displays a vision system warning: “Front Camera Not Detected.”
  2. Blurred image, black screen, or snow/noise artifacts
  3. Gimbal cannot rotate normally or video image shakes excessively

Possible Causes:

  1. Physical damage caused by collision (loose or broken wiring harness)
  2. Scratched lens or water ingress
  3. Abnormal connection between the image transmission module and the camera
  4. Ethernet connection failure

Troubleshooting Steps:

  1. Inspect the connection path: front interface board → signal cables → camera
    Replace the front interface board and/or camera if necessary2
  2. Gently wiggle the camera cable connectors (power off before operation) to check for looseness. Replace the front camera if the issue persists
  3. If hardware damage is confirmed (e.g., cracked lens or broken cable), replace the affected components immediately

Lifting system

Lifting System Reporting Abnormality

Fault Symptoms:

  1. After a crash, the lifting system is displayed as “Not Detected” on the aircraft or remote controller.

Possible Causes:

  1. High-altitude crash resulting in damage to the lifting system or lifting module.

Troubleshooting Steps:

  1. Inspect the payload control wiring harness and lifting module wiring connectors for abnormal conditions.
  2. If looseness or poor contact is found, power off the aircraft before tightening the connectors.
  3. If the issue cannot be resolved after reconnection, it is recommended to replace the lifting control wiring harness or the lifting module.

Anti-Sway System Reporting Abnormality

Fault Symptoms:

  1. During lifting operations, the payload shows no anti-sway effect and continues to swing violently.

Possible Causes:

  1. Power supply failure to the anti-sway module, preventing normal operation.
  2. Software malfunction in the anti-sway module, causing failure to execute the anti-sway algorithm.

Troubleshooting Steps:

  1. First, check whether the anti-sway module wiring harness is properly connected.
  2. If the connection appears normal, power off the aircraft and re-plug the wiring harness to attempt recovery.
  3. If reconnection does not resolve the issue, reinstall or update the anti-sway module software, or replace the anti-sway module if necessary.

Weighing Sensor Reporting Fault-Weighing Sensor Not Detected

Fault Symptoms:

  1. After power-on, the system displays: “Operation System – Weighing Sensor Not Detected.”

Possible Causes:

  1. High-altitude crash resulting in weighing sensor damage.
  2. Water ingress causing sensor failure.

Troubleshooting Steps:

  1. Replace the weighing sensor with a new unit.

Weighing Sensor Reporting Fault-Weighing Not Calibrated

Fault Symptom:

  1. The system displays a weighing calibration error.

Possible Cause:

  1. Weighing calibration was not performed after replacing the anti-sway module.

Troubleshooting Steps:

  1. Perform empty-load calibration or full-load calibration in the operation system interface.

Weighing Sensor Reporting Fault-Measured Weight Does Not Match Actual Load

Fault Symptom:

  1. The displayed weight value does not match the actual payload weight.

Possible Causes:

  1. Calibration-related error.
  2. Weighing sensor malfunction.

Troubleshooting Steps:

  1. Perform empty-load calibration with no lifting rope or payload attached.
  2. If the weight value remains incorrect after calibration, replace the weighing sensor.

Radar system

Radar Hardware–Related Faults

Fault Symptom:

  1. The remote controller displays “Radar System Not Detected – Rotating Radar ESC.”

Possible Causes:

  1. Radar ESC failure

Troubleshooting Procedure:

  1. Replace the rotating radar assembly

Fault Symptom:

  1. The remote controller displays: “Radar System Not Detected – Rotating Radar Altitude Hold.”

Possible Cause:

  1. Failure of the radar internal PCB

Troubleshooting Procedure:

  1. Replace the rotating radar assembly

Fault Symptom:

  1. The remote controller displays: “Radar System Not Detected – Rotating Radar Obstacle Avoidance.”
  2. Abnormal noise is heard during rotation, and intermittent radar errors are reported.

Possible Cause:

  1. Loose radar mounting cover

Troubleshooting Procedure:

  1. Replace the rotating radar assembly

Fault Symptom:

  1. The remote controller displays: “Radar System Not Detected – Rear Obstacle Avoidance Radar.”

Possible Cause:

  1. Rear obstacle avoidance radar failure

Troubleshooting Procedure:

  1. Replace the rear obstacle avoidance radar module

Fault Symptom:

  1. The remote controller displays: “Radar System Not Detected – Downward Radar.”

Possible Cause:

  1. Downward-facing radar failure

Troubleshooting Procedure:

  1. Replace the downward radar module
Software Version–Related Faults

Fault Symptoms:

  1. After powering on the aircraft, the system displays: “Radar System Fault – Radar Not Rotating.”

Possible Causes:

  1. Firmware version mismatch between the aircraft and the newly installed radar module

Troubleshooting Procedure:

  1. Upgrade to the latest firmware version
  2. Ensure the remote controller firmware version matches the aircraft firmware version
Other Radar-Related Faults

Fault Symptoms:

  1. Intermittent radar faults with various abnormal error reports

Possible Causes:

  1. Excessive aircraft vibration causing unstable radar connections

Troubleshooting Procedure:

  1. Adjust propeller clamp tightness to ensure consistency
  2. Secure radar connectors using adhesive (yellow glue)

Fault Symptom:

  1. Radar system not detected, accompanied by a front camera fault

Possible Cause:

  1. Excessive aircraft vibration causing Ethernet communication instability

Troubleshooting Procedure:

  1. Inspect and secure Ethernet connections

Fault Symptom:

  1. The remote controller announces: “Radar System Fault – Rear Obstacle Avoidance Not Detected.”

Possible Causes:

  1. Firmware version mismatch between the radar and aircraft
  2. Radar malfunction

Fault Symptom:

  1. Rear radar hardware failure

Possible Cause:

  1. Possible causes include incompatible radar firmware, a poor connection to the rear radar, or a faulty radar unit.

Troubleshooting Procedure:

  1. Inspect rear radar connections
  2. Verify aircraft firmware and remote controller firmware versions
  3. Upgrade to the latest firmware
  4. If the rear radar is still not detected, replace the rear radar assembly

Frame Module

Front Interface Board Faults

Fault Symptoms:

  1. After the battery is powered on, the flight controller does not power up (wiring harness connections are confirmed to be normal)

Possible Causes:

  1. Battery communication failure on the front interface board

Troubleshooting Procedure:

  1. Inspect the battery communication wiring
  2. If wiring is normal, replace the front interface board

Fault Symptom:

  1. After powering on the aircraft, the propulsion system is not recognized, and the ESC indicator lights display purple

Possible Causes:

  • ESC signal interface damage (e.g., bent or broken connector pins)

Troubleshooting Procedure:

  • Replace the front interface board
Barometer Faults

Fault Symptom:

  1. After powering on the aircraft, the system displays: “Frame Module Fault – Barometer Error.”

Possible Cause:

  1. Barometer malfunction or failure within the frame module

Troubleshooting Procedure:

  1. Inspect barometer connections
  2. Replace the barometer module or the affected frame module component if necessary

Communication Faults

Fault Symptom:

  1. The propulsion system is not recognized, and the ESC indicator lights display purple

Possible Causes:

  1. Communication failure in the corresponding arm module

Troubleshooting Procedure:

  1. Inspect the communication wiring harness of the affected arm
  2. If the wiring is normal, replace the front interface board

Fault Symptom:

  1. After powering on the aircraft, multiple faults are reported simultaneously, such as:
    “Vision System Fault,” “Radar System Fault,” and other related errors

Possible Cause:

  1. CAN bus short circuit within the aircraft

Troubleshooting Procedure:

  1. Disconnect all external payloads and accessories
  2. Retain only the following connections:
    1. Avionics (flight controller)
    2. Ethernet
    3. Battery communication
    4. Power distribution board (PDB) signal harness
  3. Power on the aircraft:
    1. If the aircraft powers on normally, reconnect additional devices one by one until the shorted device is identified
  4. If the aircraft still fails to power on with only the above connections:
    1. Troubleshoot sequentially following this order:
      Front interface board → wiring harness → avionics
    2. Continue troubleshooting until the aircraft powers on normally, then resume the above isolation procedure

Fault Symptom:

  1. After powering on the aircraft, the status LED flashes red slowly and then turns off

Possible Causes:

  1. Battery load not detected
  2. Load detection module failure

Troubleshooting Procedure:

  1. Inspect the battery signal wiring connection
  2. Attempt to power on using Battery No. 2
  3. If the aircraft powers on normally, replace the upper cover assembly of Battery No. 1
  4. If the issue persists:
    1. Inspect the PDB signal wiring
    2. If wiring is normal, replace the power distribution board assembly

Power System

Battery Faults

Fault Symptom:

  1. The remote controller announces: “Power System Fault – Battery Cells Not Detected.”

Possible Cause:

  1. Battery communication failure
  2. Power distribution board (PDB) communication failure

Troubleshooting Procedure:

  1. Replace the battery and attempt to power on the aircraft
  2. If the issue persists, replace the power distribution board

Fault Symptom:

  1. The remote controller announces: “Power System Fault – Abnormal Cell Voltage Difference, Please Land Immediately.”

Possible Cause:

  1. Excessive voltage imbalance between battery cells

Troubleshooting Procedure:

  1. Upload the battery log
  2. Await analysis results from engineering support

Fault Symptom:

  1. Abnormal voltage jumps occur during charging or discharging
    (e.g., voltage suddenly increases during charging, or drops suddenly when installed on the aircraft)

Possible Cause:

  1. Excessive voltage imbalance between battery cells

Troubleshooting Procedure:

  1. Upload the battery log
  2. Await analysis results from engineering support

Flight Authorization

Fault Symptom:

  1. The remote controller displays “Flight Authorization Error”

Possible Cause:

  1. The remote controller is logged in with a non-owner aircraft account
  2. Aircraft unlocking is restricted

Troubleshooting Procedure:

  1. Log in to the Ceres Aviation platform
  2. Grant control authorization to the relevant account under Flight Control Authorization

Pilot Authorization

Fault Symptom:

  1. The remote controller displays “Pilot Authorization Error”

Possible Cause:

  1. The pilot has not completed official Ceres training
  2. Pilot credentials have not been approved or verified

Troubleshooting Procedure:

  1. Contact the authorized dealer or Ceres technical support
  2. Complete required pilot training and certification review

Drone status

Fault Symptom:

The remote controller displays: “Aircraft Status Error”

Possible Cause:

  1. The current operating area does not permit aircraft unlocking (e.g., restricted or no-fly area outside the dealer’s authorized operating region) outside the dealer’s authorized operating region)

Troubleshooting Procedure:

  1. Submit required documentation to request area unlocking
  2. Coordinate with Ceres technical support to add an approved test flight zone for the aircraft