Header Overview

Reaction to warnings

Whenever your AscTec UAV is giving a warning signal, the pilot needs to find out why this warning occurred and then should react accordingly. Please have a look at the Status information section for further information about the warning signals.

The next list shows the recommended reaction, if the following warnings occur:

  • Battery warning: The acoustic battery warning starts when the battery reaches a critical voltage level. In this situation, please stay calm and land as soon as possible. Since the battery level is low, there are no big power reserves for fast maneuvers. Therefore you should not give hectic or strong commands and sink slowly and constantly.
  • GPS warning: This warning will occur if there is no valid GPS lock and the pilot switches the flight mode stick to GPS Mode. Please note, that the flight system will automatically activate the Height Mode, when the GPS Mode is selected and there is no valid GPS lock!
  • System initialization: As long as you hear the double beep shortly after switching on your flight system, you must not move the flight system. During the first seconds, it will initialize the gyroscopes. After the double beep stopped, you can move the flight system again.
  • HL status undefined: This warning occurs if there is a problem with the code on the high level processor. This might happen after updating your AscTec AutoPilot or using the AscTec SDK. Try to re-flash the HLP processor again. Therefore you can use the AscTec Research Upgrade tool, the AscTec SDK or Flash Magic.
    Another problem might be, that two pins of a connector on the AscTec AutoPilot are accidentally connected (short circuited). If so, switch off your system, bend back the pins and start your system again.
  • Gyro calibration error: This error usually occurs, when the system was moved during the initialization process. In this case, put the UAV on a fix ground and restart it. Then do not move it for approx. 5 seconds or until the double beep stops. After that, it is okay to pick it up and move it again.
  • Accelerometer calibration error: This warning occurs, if the accelerometers are not calibrated correctly. In this situation you should first try to restart the system and see if it was a problem during the initialization. If the warning still occurs, you can try to re-calibrate your accelerometers. To do that, please use the AscTec Research Upgrade tool.

  • System startup problem: If this warning occurs, check your AscTec AutoPilot for defects and restart your system. If it still occurs, please contact team@asctec.de.
  • Compass magnetic field strength warning: The measured magnetic field is stronger than the usual earth magnetic field strength. This indicates, that there is an external magnetic field close to the flight system. Please note, that external magnetic fields can disturb the compass of your AscTec UAV. This disturbance might lead to flight problems while using the GPS Mode. If you are in an outdoor environment and this warning occurs, it is recommended to search for a different starting spot where this warning stays off. For further information how to recognize if there are problems with the compass, please have a look at Disturbed behavior in the GPS Mode.

  • Compass magnetic inclination warning: The earth magnetic field has a fix direction, which can be measured by the compass. The magnetic inclination can only be checked, if there is a valid GPS lock, because you need to know your location on earth to have a reference earth magnetic field inclination. If the measured inclination does not fit this reference, this error occurs. This might be due to an external magnetic field, or due to a compass calibration at a far away location on earth. In most situations, this warning is not critical, but you should be careful using the GPS Mode. It can help to re-calibrate your compass.

  • Compass error: This error occurs, if your compass is not connected or is defect. Please first check the connection of your compass. If the error still occurs with the compass plugged-in, please contact team@asctec.de. It is still possible to fly, without the compass connected, in the Height Mode and Manual Mode.

Disturbed behavior in the GPS Mode

  1. faulty, disturbed or mis-calibrated compass can lead to massive flight problems in the GPS Mode. If an unusual behavior of the flight system (while flying in the GPS Mode) occurs, the safety pilot needs to take control over the UAV by switching to the Height Mode or Manual Mode and control the UAV position manually.

You can recognize a faulty compass before the flight by looking at the telemetric data with the AscTec AutoPilot Control software. The compass measurement is displayed in Calculated IMU Data. You can find the measured angle under Yaw Reference. This value should not change more than ±5°, while the UAV is not moving around the yaw axis.

You can recognize a problem with the compass by looking at the behavior of your AscTec UAV while flying in the GPS Mode. If the pilot switches to the GPS Mode (no serial interface activated!) and leaves both control sticks in the center positions, the UAV is supposed to stay at its actual height and position. If you see, that the UAV starts moving on a circular path, this indicates a problem. In this situation, the pilot needs to switch out of the GPS Mode immediately.

The mentioned behavior might also come from an external magnetic field. So if this behavior happened close to a magnetic source (e.g. windmill, power line, etc.), you should also switch out of the GPS Mode and fly further away from this source. Then you can switch back to the GPS Mode again, to see if the same behavior occurs. If not, you can continue flying in the GPS Mode. If it still occurs, you should not use the GPS Mode anymore and check your compass.

UAV drifts sideways in Height Mode or Manual Mode

Due to unavoidable measurement errors or the unbalance of mechanical parts it is perfectly normal that an AscTec UAV is not always 100% leveled during flight with the control sticks in centered position. A slight tilt can easily be compensated by the trimmers on your remote control. To do that follow the next steps:

  1. Make sure there is no wind which can cause a drift.
  2. Hover in Height Mode or Manual Mode and check in which direction the UAV drifts.
  3. Push the trim switches on your R/C stepwise in the opposite direction of the drift until the drift stops.
  4. After switching off the UAV, it might be necessary to re-adjust the trimming.