The main emphasis in the regulations and guidelines set by the Civil Aviation Safety Authority (CASA) is safety. The aim is to prevent accidents, injuries and damage to property by ensuring drones are flown in a particular way.
External factors, particularly the weather conditions, can affect the safe and effective operation of a drone and increase the risk of injury and damage. High winds, heavy rain, extremes of temperature and other conditions can all make drones more difficult to fly and can also affect the pilot’s ability to fly them.
An unstable drone will also make it more difficult to capture clear images and will make collected data less accurate.
Before starting any flight, you need to check the local weather forecast and, if conditions are expected to be bad, delay the take-off until they improve sufficiently. Also, always consult your drone’s operating instructions, which should include the extremes of weather in which the drone can safely be flown.
Clear skies with light winds are ideal conditions for flying a drone. However, these are not always available so being aware of the likely weather conditions and taking necessary precautions will reduce the risks and help to prevent accidents.
Wind
This is one of the main factors affecting the stability of a drone and its range. These are affected not only by the sustained wind speed but also by gusts of wind that can be unexpected and can jolt the drone off its course.
All drones are affected by wind, but a small and light drone is more severely affected while a large and heavy model can better withstand higher speeds. Similarly, the various styles of drone are affected in different ways.
A helicopter or multi-rotor style drone that is hovering will be swept along by winds and will require steering commands to keep it in place, and even this may not be possible in very strong winds. A fixed wing drone will need more power when flying into the wind and may be difficult to keep on course.
All these manoeuvres require more power, which will deplete the battery quicker and reduce the drone’s range. In these cases, a drone may not be able to return to its starting location, even if the automatic Return to Home function is activated due to a low battery charge. This is made worse by the drone not being able to account for wind speed when calculating the distance it can travel and so this may be estimated incorrectly.
The result may be that the drone is forced to land in an unsuitable location that cannot be selected, with the likelihood of an uncontrolled landing. This can sometimes be avoided by flying at a higher altitude, so the drone is above the worst of the wind.
If the drone is carrying a payload, such as a cargo or communications equipment, this must be securely attached to prevent it coming loose in the wind. It may also change the centre of gravity, which makes the drone more difficult or impossible to control, and may increase air resistance so it is more unstable in high winds and may mean the manufacturer’s recommendations are no longer applicable.
With practice, you can use the wind to your advantage. Although a head wind will slow the progress of the drone, a tail wind will speed it along and mean less power is needed to fly. Nevertheless, you need to monitor your battery carefully when flying in wind since power needs are more variable.
Rain
Most drones do not have an IP rating that indicates how well it is protected against moisture. Unless it is specifically rated for wet conditions, its electrical components can be damaged by water.
Water ingress during a flight can lead to a partial breakdown of the system or even a complete failure that will bring the drone down. Any part of the drone’s structure may be adversely affected by moisture, causing weaknesses that may not be revealed immediately but can cause a malfunction later.
Flying in heavy rain is a real risk and must be avoided at all times. The drone manufacturer will generally state permitted conditions for flying.
Extreme Temperatures
Both very high and low temperatures can affect a drone’s performance. Very high temperatures can result in overheating, can drain the battery faster than normal and will eventually reduce battery capacity so that flight times and performance are decreased.
Extreme cold is more of a problem, causing motors to work much harder so that batteries drain more quickly and flight times are reduced. It can also cause ice to form on propellers and wings, increasing the overall weight and changing their profiles so that lift may be decreased. This is sometimes so severe that helicopters and multi-rotor models cannot stay in the air.
Cold batteries have a lower storage capacity and a reduced ability to release charge so that power is less. This situation can be helped by warming the battery to room temperature before a flight. Also, do not underestimate the effect of cold on the operator, who needs to wear appropriate clothing to be able to withstand the cold but also has to have sufficient dexterity to be able to operate the controller.
Cold weather causes plastic to become brittle so it is likely to break more easily and needs careful handling. A radiator transmitter and camera screens will also not work as well in cold conditions. The transmitter has relatively low battery use, which means the battery is not warmed as much as in higher temperatures and so may stop working.
Temperature generally decreases as altitude increases, and the recommendation is that drones should be flown at between 0⁰C and 40⁰C.
Visibility
Maintaining a clear line of sight to your drone is essential for its safe operation. However, fog and smoke from bushfires will limit the distance you can see, which means that your line of sight to the drone can be reduced significantly.
To comply with CASA guidelines, you will not be able to fly the drone as far as when visibility is clear. Also, if you are using the drone to take photographs or to capture video, the quality of the images will be reduced if visibility is not good.
Dense cloud cover can also make images darker while even strong sunlight can create shadows that make details not as clear. The best time to film is early in the morning or late in the evening when the angle of the sun is lower and shadows are less prominent.
Thunder
Thunder is one of the most difficult weather conditions to predict but can also be the most threatening. It can be very local and can develop quickly, almost without warning, or may be part of a large weather front that is impossible to avoid.
A lightning strike from a thunderstorm can severely damage or destroy your drone. The storm may also bring heavy rain, hail and strong winds that can be extremely hazardous, not only for the drone but for the pilot also. You should, therefore, avoid flying if thunder is forecast.
Humidity
High humidity is difficult to predict but can affect the performance of your drone. If the drone does not have an IP rating, indicating its ability to resist moisture, its electrical systems can be badly affected by humidity and cause a lack of stability so that keeping a steady position is difficult.
Many drones have infrared sensors that are sensitive to water so high humidity can result in incorrect measurements being reported. Condensation on a camera lens will also result in blurred images being captured. It is best to fly your drone only when humidity levels are between 30% and 70%.
Turbulence
The air can become turbulent when the steady movement of the air is disturbed. A common cause of this is the radiant heat from the sun, which heats the ground and the air above it, causing the air to rise. Dark areas warm quicker than lighter ones and the warm air above them rises and causes thermals, the air rotating as well as rising quickly.
Flying a drone into a thermal causes it to rise by soaring, saving on battery power to achieve greater height. In general, any loss of stability caused by thermals is fairly minor and can be easily dealt with by a drone’s flight stabilisation system.
Mechanical turbulence can occur when the wind flow is altered due to it coming up against an obstacle such as a building or the edge of a forest. The strength of the turbulence depends on the size and shape of the obstacle and, although most disturbances can be handled by a drone’s flight stabilisation system, strong and sudden winds can cause a loss of control.
Mechanical turbulence tends to decrease as you go higher and generally doesn’t apply above fifty metres, although wind speeds can be greater.
Turbulence can also occur due to a rapid temperature change. Sometimes, at a certain altitude, a boundary layer is present and the wind speed above it is much stronger than below. This is most common in winter and can cause a temporary loss of control. Turbulence is difficult to predict so you always need to be alert.
Air Density
If the air is thin, resistance is lower, but a drone’s wings or rotors will generate less lift and thrust. This reduces the drone’s ability to take off and also limits its carrying capacity.
Standard air density is found at sea level and when the temperature is 15⁰C and the air pressure is 1,013.25 hPa. Air density falls at lower temperatures and rises in hot conditions and is also changed in inverse proportion to air pressure.
Knowing the air density is important if you need your drone to take off at altitude. The user manual should indicate the maximum take-off altitude.
Minimising the Risks Caused by Weather
In order to operate your drone safely, you should ensure you take certain steps for every flight:
- Always check the weather forecast before starting. There are apps and websites specifically for drone flyers and these will be the most relevant and dependable. Check the forecast wind speed and direction, minimum and maximum temperatures, likely humidity levels and the possibility of rain, cloud cover and storms.
- CASA promotes the use of drone safety apps that tell you whether or not it’s safe to fly based on weather conditions.
- Never fly in conditions that are beyond the limitations of your drone. Refer to the manufacturer’s instructions and recommendations to check against expected conditions such as wind speeds and temperature.
- If you are likely to fly in adverse weather conditions frequently, acquire a drone that has good weather resistance. Get one that is particularly robust and has a high IP rating.
- If the weather is worse than you anticipated or deteriorates during the flight, land the drone safely while you can. It is better to do this than to risk losing control and crashing the drone.
- Be alert to changes in weather conditions during the flight. You can use tools to measure wind speed and direction so will be aware if the situation becomes worse.
- Always be particularly aware if you fly near bodies of water or an obstacle such as a building. These can cause sudden increases in wind speed that can affect stability.
- Practice as much as possible flying in different weather conditions, gradually increasing your exposure to conditions that are less than ideal. This will give you the necessary experience and confidence to deal with any challenges the weather brings.
Safety is the highest priority when flying your drone and weather conditions can make this more difficult to achieve. They may also render captured images and collected data unsuitable for use and mean that the work has to be done again, which spoils the purpose of a flight.
However, if you are properly prepared and stay alert at all times, you will be able to complete each flight successfully.
At Global Drone Solutions, we can help to ensure you are prepared for all conditions by providing comprehensive training in all aspects of drone flying. If you need advice or want to be completely ready for all eventualities, get in touch now.
