Weight classes
A 250 gram drone is one whose take off weight, battery and propellers fitted, falls below the 250 gram boundary that the Civil Aviation Authority uses to divide the lightest class of uncrewed aircraft from everything heavier. It is a single published figure, it is measured on the aircraft rather than assessed on the person flying it, and it is the specification that decides more about the ownership of a drone in the United Kingdom than any other. A machine at 249 grams and a machine at 251 grams fly almost identically and sit in different classes.
Why 250 grams was drawn there
The 250 gram figure was drawn where it was because weight is the closest simple proxy for how much harm an aircraft can do when it arrives somewhere unintended. Kinetic energy rises with mass, so a heavier machine falling from the same height hits harder. Weight is also the one specification that cannot be argued about: it is measured on a set of kitchen scales in a few seconds, whereas skill, intent and flying conditions cannot be measured at all. A boundary that a regulator can check is worth more than a boundary that describes risk more precisely and cannot be enforced.
The figure is not a British invention and it is not unique to the CAA. It appears in the equivalent schemes of several other national authorities, which is why manufacturers design to it globally rather than for one market. That is also why so many folding camera aircraft arrive weighing just a few grams beneath the line: it is a design target, not a coincidence.
What the boundary changes, and what it does not
The boundary changes three things about owning and flying a drone, and leaves a great deal untouched. What it changes is worth stating in general terms, because the detail belongs on the rules pages and not in a buying guide.
| What the 250 gram line affects | Direction of the change |
|---|---|
| Registration and competence requirements | Lighter aircraft attract a lighter set of requirements under the CAA scheme |
| How close you may fly to uninvolved people | This is the main practical difference, and it is far more permissive below the line |
| Where flying is realistic at all | A lighter machine opens up locations a heavier one effectively rules out |
| Height ceiling | Unchanged. The 400 foot ceiling, about 120 metres, applies either way |
| Keeping the aircraft in sight | Unchanged. Visual line of sight is required of both classes |
| Flying near airports and restricted airspace | Unchanged. Restrictions apply to light aircraft exactly as they do to heavy ones |
The three rows marked unchanged are the ones buyers most often get wrong. A sub 250 gram machine is not exempt from the ceiling, is not exempt from being kept in sight, and is not welcome inside a flight restriction zone. It is a lighter aircraft under a lighter set of requirements, not an unregulated one.
The exact requirements either side of the line, including how a camera on board changes the answer, are published by the Civil Aviation Authority and are revised from time to time. Under 250 grams sets out what the CAA scheme currently asks of the lightest class, and the CAA itself is the only place to confirm any of it before a flight.
How the aircraft is weighed, and how buyers get it wrong
The weight that counts is take off weight: the aircraft as it leaves the ground, with the battery, the propellers, the memory card and anything else bolted to it. Four mistakes account for most accidental crossings of the line.
- Reading the airframe weight. A specification sheet that quotes a weight without the battery is quoting a number that never flies.
- Fitting propeller guards. Guards are sold as a safety accessory and they add weight to an aircraft that was designed with almost none to spare.
- Fitting a larger pack. An extended battery sold for longer flight time is the commonest way a sub 250 gram machine stops being one.
- Adding stickers, mounts or filters. Individually trivial, collectively enough when the design margin is a handful of grams.
Weighing the aircraft yourself settles it. A set of kitchen scales reading to the gram is sufficient, and it is the only figure that describes the machine as you actually fly it.
The weight classes above the line
Above 250 grams the classes continue upward, and the further up they go the more the aircraft is treated as a serious machine rather than a light one. For a hobby buyer the relevant fact is simpler than the class structure: almost everything above the boundary in the consumer market is a larger camera aircraft, a first person view machine, or a fixed wing model.
Camera drones covers what the heavier camera class buys for its extra weight, which is chiefly wind tolerance, sensor size and transmission quality. FPV and racing drones covers the class where weight is spent on power rather than on payload, and where a builder chooses the take off weight themselves rather than accepting a manufacturer's. What a drone actually is places all of these against each other in one table, which is the fastest way to see where a given listing sits.
Is the lightest class the right first drone?
Yes, for most first time buyers in the United Kingdom, and the reason is location rather than law. A sub 250 gram aircraft can be flown in more of the places an ordinary person actually stands, which means it gets flown, and a drone that gets flown teaches its owner something. A heavier machine bought first often sits in a cupboard because every outing needs planning.
The case against it is real and should be said plainly. A light aircraft is at the mercy of wind, and the British year does not offer many still days. Below the line the machine is fighting weather that a heavier one would ignore, and in a stiff breeze it will drift, fail to hold a shot, and occasionally struggle to come home against the wind. Somebody who already knows their photographs are the point, and who is prepared to plan around the requirements, is better served above the boundary. Everybody else should start beneath it.