UAVs are susceptible to a myriad of failures due to various complications with the system. When it comes to operating conditions, the list is quite long of ways that your drone can be impacted. We're going to talk about some of the ways heat can affect drone operations.
When is it too hot to fly my drone?
If the thermometer is reaching for the sky, and you want to fly your drone on a hot day, you should do a bit of Googling first! The maximum operating temperature of your UAV system (assuming that it is a consumer- or commercial-grade drone, and not something you built on your own) should be listed in the specs for that system. For all DJI systems, you can find their specs on their system pages on the DJI website. Just do a simple Google Search for "DJI Mavic Pro Specs" (or whatever system you're using) and it should be one of the top links:
Operating in conditions above the maximum "threshold" for heat is not a death sentence for your drone, but it is HIGHLY inadvisable. Here is why:
1. Too much heat may cause video brownout.
The camera/sensors used on UAVs have their own electronic motors and do not necessarily have adequate cooling mechanisms built in, therefore, when it gets too hot, things stop working properly. You may end up with choppy video, or black chunks where nothing has recorded. Of course, you wouldn't know about this until you're back at the office analyzing your footage...
2. Heat can cause an overloaded IMU.
The Inertial Measurement Unit is possibly the most important feature on your drone. It measures the amount of angular rotation and velocity, and sometimes the magnetic field surrounding the drone. It uses a combination of accelerometers, gyroscopes and magnetometers to essentially determine the position of the drone in space. It works in conjunction with the GPS to tell you exactly where, and which direction your drone is facing. It is especially useful when operating a UAV in "attitude mode" as the system relies nearly 100% on feedback from the IMU in order to move around. If it gets too hot, it may fail. If the IMU fails, your drone fails.
3. Excessive heat may cause battery failure.
Lithium Polymer batteries (LiPo) are relatively unstable compared to other batteries, and are favoured because of their high energy capacity and output thresholds. They can be quite volatile however, and generate quite a bit of heat when in use. You will often find when you remove a used battery that it is quite warm (almost hot) to the touch. NEVER CHARGE A BATTERY THAT IS STILL WARM FROM USE, LET IT COOL DOWN FIRST. If the outside temperature is too hot, it may cause the battery to react violently and could cause a failure during operation. You should limit use to a small portion of the "normal flight time" when the temperatures outside are scorching.
You should try to ensure that batteries are never stored in direct sunlight while on an mission on a hot day. You should try to have keep them in a shaded, or air-conditioned space, out of the sun, so that they remain at the magic temperature of between 18-22 degrees Celsius (64-72 F).
4. Heat can cause operator fatigue.
This is a very important factor to consider, which is often ignored. Heat-related illness such as heat-exhaustion or heat-stroke can be prevented. You may think that flying a drone around is a low-energy activity, and that you are at a low risk of over-exertion. However, lifting and carrying boxes, setting up flags/pylons as operational boundaries, laying ground control points and carrying around surveying equipment, and other such activities can be quite taxing on your system on a hot, hot day!
Make sure that you bring enough water with you! A 500mL bottle of water is NOT enough when the mercury reaches 35-40 degrees Celsius (95-104 F). You should bring a large water cooler with ice in it for missions, and try to drink around 3-4 cups per hour. Take frequent breaks in shaded areas or in an air-conditioned vehicle. Wear a hat and sunscreen!
Remember, if something were to go wrong (ie. you lost control of the system for ANY reason and caused an accident), if it was determined that you were suffering from heat-stress, you may be found negligent. In Canada, it is a condition of the SFOC (Special Flight Operations Certificate issued by Transport Canada) that the drone operator must not be impaired by either substances or fatigue while operating the UAV system. If that were the case, you may not be covered by your liability coverage, and you may be deemed to have violated the conditions of your SFOC.
MAKE SMART DECISIONS!
It is up to you to recognize the risk factors, and determine whether you should delay your operation until things cool down. Always consider what would happen if something went wrong - did you do everything in your power to ensure that it wouldn't? Don't rely on your insurance to defend you... if you are at fault due to negligence, you may not be covered!