What is a drone, and what are drones used for?

Balance a broom upright on the palm of your hand. It will not stay there by itself. You have to keep sliding your hand under it, correcting again and again, and you have to do it fast.

A drone with four propellers does the same trick in the air. It is not steady on its own either. A small computer on board reads its own tilt hundreds of times a second and changes the speed of each propeller to hold it level. That computer is the real invention here, and propellers and batteries were the easy part.

A drone is an aircraft with nobody on board. That is the whole definition, and everything else is a detail. In aviation paperwork you will see the longer name, uncrewed aerial vehicle, shortened to UAV.

How a drone stays in the air

Look at a common four-propeller drone. Two propellers spin one way and two spin the other way. Why bother? Because a spinning propeller tries to twist the whole aircraft the other way, and pairs that turn in opposite directions cancel that twist out.

Steering is done by changing speeds, not by moving flaps. Speed up the two rear propellers and the nose dips. The push of the propellers now points forward as well as up, so the drone moves ahead. Speed up the pair on one side and it rolls and slides sideways. Speed up the two that spin the same way and the whole aircraft turns on the spot.

Sensors keep it honest. A drone usually carries a gyroscope and accelerometer to feel tilt, plus a barometer to sense height by air pressure. It also carries a satellite receiver to fix its place. Many add a downward camera to hold still over one patch of ground. This is robotics in the sky, with the same loop of sense, decide, act.

The main kinds of drone

• Multirotor. Four, six or eight propellers. It hovers, it takes off from a small clearing, and it is easy to fly. However, it also empties its battery quickly.
• Fixed wing. It looks like a small aeroplane. The wings carry the weight once it is moving, so the motor only has to push it forward. It flies much further, but it cannot hover, and it needs room to launch and land.
• Hybrid. It lifts off on rotors, then tips forward and flies on its wings. However, you pay for that with weight and cost.
• Tethered. It hangs above one spot on a cable that feeds it power, so it can stay up for hours. Useful over an event or an accident scene.

The word hover explains most of the trade, because hovering means holding your whole weight up with moving air, every second, with no help. Therefore, it is the most expensive thing a flying machine can do.

What drones are used for

Filming is the use everybody knows, but it is not the biggest one.

Mapping and survey work may be the most valuable. The drone flies a grid and takes hundreds of photos that overlap. Software then lines up the overlaps and builds a map and a three-dimensional model of the ground. Surveyors use it to mark plot boundaries, and builders use it to check progress each week. Mines use it to measure the size of a stockpile.

Farming is close behind. A camera that sees a little beyond what your eye can see will show stressed crops before you notice them from the road. Spray drones carry a tank and cover a field far faster than a person with a knapsack sprayer. Nobody walks through the chemical.

Inspection saves lives. Telecom masts, power lines, roofs, bridges and water tanks all need looking at. A drone with a good camera does the looking, so nobody climbs.

Then there is delivery of small urgent loads, and search and rescue after a flood or a collapse. Add counting wildlife in a park, and military use for watching ground and striking targets. Military demand is one reason the parts became cheap and good.

What drones are bad at

Weight is the first limit. Lift costs energy, and every extra gram costs more. A drone that carries a heavy load flies for a short time, so most useful drones carry very little.

Weather is the second. Wind pushes a light aircraft around, rain gets into motors, and heat thins the air so the propellers bite less. Radio is the third. Hills, buildings and other transmitters all cut the link, and a lost link means the drone has to decide for itself what to do.

Indoor flying is harder than it looks, because satellite signals do not reach inside a building. Then there is noise, which annoys neighbours, and cameras, which worry them. Both are real problems and neither is solved by better engineering alone.

The rules you have to follow

Rules differ by country, but the shape of them is similar nearly everywhere. Register the aircraft. Keep it where you can see it with your own eyes. Stay low, since many countries cap you at about 120 metres. Stay away from airports and from crowds. Get a permit or a pilot licence before you fly for money.

In Kenya and Nigeria the civil aviation authority requires drones to be registered. Commercial flying needs both a licensed remote pilot and permission for the job. Do not guess at this. Read the rules on the authority’s own website, because fines and confiscation are common where people do not.

What drones changed in Africa

The clearest example is blood. In Rwanda and Ghana, fixed-wing drones fly blood and medicines from a central store to rural clinics and drop them by small parachute. A road trip of hours becomes a flight of minutes. That matters most for blood, because it does not keep well and is needed without warning.

The wider lesson is about roads. Where a road is bad, seasonal or long, a light aircraft with no pilot starts to make sense for small and urgent loads. The same logic holds for mapping land where no recent survey exists. It holds for checking the telecom masts that sit far from any town.

What is coming next, and what to check

Two changes are worth watching. The first is flying beyond the sight of the pilot, which regulators are opening up slowly, route by route. The second is autonomy, and drones are getting better at seeing other aircraft and moving out of the way. They are also better at flying a whole job with nobody on the sticks. Some of that skill is learned from practice rather than written out by hand, which is where reinforcement learning comes in. A drone is a robot that happens to fly. It needs no arms and no legs to be useful, which is worth remembering when you read about a humanoid robot.

Do this before you buy anything. Open the website of your national civil aviation authority and find the page on uncrewed aircraft. Write down three things: the weight above which you must register, the maximum height, and what a commercial permit costs. Therefore, those three numbers decide what you can actually do with a drone where you live.

Just Out Tech explains new research in plain language. This article was drafted with AI assistance and checked by a human against the original source.