Header Overview

There is an Emergency Mode implemented in your AscTec UAV. It is activated whenever there is no proper connection to the remote control. The idea of the emergency mode is, to let the UAV do an emergency procedure in the event, that the safety pilot can not control it anymore. This prevents an uncontrolled flight of the UAV.

*Please take note of the following general information:*

  • The home position is set automatically to the position where you start the motors. If no GPS lock is available at that time, there is no possibility to set the home position, therefore the flight system automatically sets the Emergency Mode to “Direct Landing”.
  • When there is no valid GPS lock available while the Emergency Mode is active, the system will immediately start descending at 1 m/s, keep itself leveled and starts drifting with the wind.
  • Flying back to home position does not mean the system flies in a perfectly straight line. Especially when there is wind, the flight path might be curved.
  • When the Emergency Mode is activated and you reestablish connection to the flight system, the system will stop the emergency procedure and switches into the flight mode selected on your remote control.
  • Each time you switch on your AscTec UAV, the emergency procedure is reseted to "Direct Landing".

According to your flight mission, you need to choose the emergency procedure of the emergency mode. There are several procedures selectable, which cover most flight situations.

Available emergency procedures

Direct landing: Your AscTec UAV takes a horizontal attitude and sinks at its actual position with 1m/s. If the GPS Mode was active in the event of the data link loss, it will also keep its actual GPS position while sinking.

Wait and land (only if GPS Mode is used during loss of reception, else Direct landing is set): Your AscTec UAV first waits at its actual position and height for 5 seconds and then sinks with 1m/s at its current position.

Come home (GPS and compass used): Your AscTec UAV automatically switches to GPS Mode and holds its position and height for 5 seconds. Then it keeps its actual height or climbs up to 20m if below 20m. Then it flies approx. in a direct line to the home position. When it arrives at the home position, it keeps this position and sinks with 1m/s.

Come home high (GPS and compass used): Your AscTec UAV automatically switches to GPS Mode and holds its position and height for 5 seconds. Then it climbs up to the highest altitude obtained during this flight mission (max. height resets after turning off the motors). It waits for 5 seconds on the max. height and then flies approx. in a direct line to the home position. When it arrives at the home position, it keeps this position and sinks with 1m/s.

Choose your emergency procedure

Before selecting an emergency procedure, try to find out which procedure is matching your planned flight mission best. To help you in this decision, please read through the following examples. They give you an idea, what the advantages but also disadvantages of the procedures can be.

As default, Direct landing is selected, because it also works without a fully working GPS Mode. If you select a procedure which uses the GPS Mode, an erroneous compass (e.g. disturbed by magnetic field) would lead to problems in keeping its position or flying to a requested waypoint (home position). In the worst case, your UAV might just fly away without any chance of stopping it. Hence, make sure the GPS Mode of your AscTec UAV is working correctly, before selecting such an procedure.

The Direct landing mode can lead to problems, if your UAV flies above non-landing areas (e.g. forest, building, lake, river, etc.). If you can find a proper home position, you can avoid an unwanted landing e.g. in the water or on objects by choosing a Come home mode.

Both Come home modes will let the UAV try to come back to its home position even if there is only a too short flight time left. Hence, we recommend not to use these emergency procedures for flight missions with large distances from the home position.

The Come home high mode can be used to prevent your UAV from hitting any objects while it is flying back to the home position (e.g. if you are flying a shallow circle around a high tower >20m). In this mode you can define a safety height at the beginning of your flight by flying above the highest surrounding object. In case of a data link lost, the UAV will then first climb up to that safety height (max. height during this flight) and then will come home and land. A disadvantage of this mode is, that even when there is only a too short flight time left, the UAV will climb to the max. height. Hence, we recommend not to use this emergency procedure for flight missions in high altitudes (>50m).

To change the procedure, you can use the AscTec AutoPilot Control software.

  1. After connecting your AscTec UAV successfully to the software, click on "System Info" in the menu bar.
  2. In "System Info" click on "Change EM".
  3. You will first see a warning, which tells you, that the emergency mode will be reseted to Direct landing every time you switch off your AscTec UAV. Click on "OK".
  4. In the next pop-up you can choose the desired emergency procedure. Select it by marking one of the four white dots on the left side. Then click on "Transmit to UAV" to tell the AscTec UAV the selected procedure.

Choose your home position

The home position should be chosen to allow the automatic landing of your AscTec UAV. It is automatically set by the flight system, when the motors are started the first time after switching on your UAV. To be able to set the home position, the UAV needs to have a valid GPS lock.

If the motors are switched on before the UAV got a valid GPS lock, no home position can be set. -> Automatic selection of the "Direct Landing" procedure!

We recommend that the area around the home position should have a soft ground (e.g. grass), a radius of approx. 10m clear of objects and should provide a good GPS reception at the ground.