3. Emergency Procedures

This Section contains checklists as well as descriptions of the recommended procedures in case of an emergency.

Emergencies caused by motor or system malfunctions are extremely rare if pre-flight inspections and maintenance are performed properly.

3.1 Motor Failures

Operation is not possible with one motor, electronic speed control, or propeller failure.

In case a motor fails, you will see a 'Potential Thrust Loss' message on the GCS.

In any instance that the aircraft experiences failure to one or more of these critical flight components, immediately warn bystanders that an aircraft is coming down and clear the area. No specific electronic user interface indicator is currently available; however; aircraft attitude control will be lost, accompanied by altitude loss.

3.2 Electric Power Failures

3.2.1 Excessive Current Consumption

How to Diagnose: Monitor the Current through Mission Planner, if the current readings start to spike unexpectedly.

In case of excessive current spikes, please land the drone as soon as possible and check hardware connections, check the frame for any imbalances and defects.

3.2.2 Battery Exhaustion

The SIGMA25G will automatically enable Return-to-Launch (RTL) if the battery voltage falls below 13.5V. If there is not enough battery capacity to make it to the original launch point, the aircraft will land immediately.

3.3 Avionics System Failures

3.3.1 Pilot Loss of Aircraft Orientation

If the pilot loses the visual orientation of the SIGMA25G, then Enable Return-to-Launch until you can verify the orientation of the aircraft. An avionics system failure will result in the aircraft triggering an RC Failsafe error and the aircraft will Return-to-Launch.

3.3.2 Unexpected Flight Controller Behaviour

If the aircraft ever acts unexpectedly, immediately enable the Return-to-Launch flight mode.

To enable RTL Flight Mode, flick RC Switch 6 to the bottom position (RTL Stick).

3.3.3 Compass-Related Errors

In the case of major Compass-related issues like 'red compass variance', switch the FlightMode to AltHold (abort mission) and proceed to land the drone in a suitable location nearby. Otherwise, in case of any minor compass-related issues, you can switch FlightMode to RTL and after landing, calibrate the compass (Setup> Compass> Start calibration).

Compass Calibration

In the case of a 'Mag Anomaly', change the take-off location and restart the drone.

3.3.4 Vibration/IMU-Related Errors

If you are getting excessive vibration readings from the drone (in the red range), switch the flight mode to AltHold and land the drone ASAP.

Vibration Ranges: 0-30 -> low 30-60 -> mid >60 -> high

3.3.5 GPS-Related Errors

If the drone loses its GPS Signal for any reason, it goes into 'Land' FlightMode and descends downwards at whatever location it is flying in. Do not panic if this is the case, it should be able to land itself on the spot.

3.4 Control Station Failures

​Control Station Battery

Check battery levels.

Make sure to charge them sufficiently before flights.

Control Station Antenna

Reposition Antennae to Regain Telemetry Link.

Make sure to place the antennae in a position that maximises signal strength.

Flight Mode

Switch to RTL in case of emergencies.

In case of a Radio Failsafe, the drone will continue normal operation (auto mission).

A Loss of Signal (LOS) can occur if the radio controller stops transmitting a signal, or if the aircraft is too far away to receive it.

In the event the vehicle detects a LOS, it will automatically execute either Return-to-Launch or Continue Auto mission depending on the radio failsafe setup in the Mission planner. While the aircraft includes these emergency control modes, it is always recommended to attempt to regain signal link with the vehicle to keep the pilot in control of the aircraft.

Try the following steps:

• Adjust the antenna orientation for the best signal strength while ensuring that the radio antenna matches the direction of the receiver antenna.

• Move the radio away from objects to get a clear visual line of sight to the SIGMA25G.

• Set the Mode switch to Return-to-Launch so the SIGMA25G will continue to approach the launch point if the signal is momentarily regained, resulting in a higher likelihood of regaining full signal reception.

• If all above doesn’t work out, try to restart the radio/control unit.

3.6 Geo-Fencing

ArduCopter supports failsafe generated by several types of Fences (boundaries described by latitude/longitude and/or altitude) to prevent the vehicle from traveling higher or further than desired, or into unwanted areas. Upon Fence breach, selectable actions are taken.

Fences are enabled by default on Sigma25G, but they need to be defined manually and the drone will RTL in case a fence is breached.

To set up a GeoFence, Follow the procedure below:

1. Go to the 'Plan' screen on the GCS, and click on the 'Polygon' symbol on the left of the screen.

1. Draw a polygon around the area you want to be fenced.

2. Next, Select the type of fence as inclusion/exclusion as per your requirements.