The 120 metres, and the trap of terrain
The maximum height in the ‘open’ category is 120 metres. The figure is easy; measuring it is not, and that is exactly where the examination waits for the candidate.
Key points
- The 120 metres are measured from the closest point of the surface of the earth: so from the terrain under the aircraft, not from the take-off point.
- Flying down a slope, the altimeter on the controller stays reassuring: it shows the height above the take-off point, while the real clearance above the ground has already been exceeded.
- Flying up a slope, the same altimeter alarms for nothing: the ground rises with the aircraft, and the distance to the surface stays within limits.
- Two derogations, not one. Within a horizontal distance of 50 metres from an ARTIFICIAL obstacle taller than 105 metres, the maximum height of the UAS operation may be increased up to 15 metres above the height of the obstacle, at the request of the entity responsible for the obstacle (UAS.OPEN.010(3)). And an unmanned sailplane with an MTOM, including payload, of less than 10 kg may be flown at a distance in excess of 120 metres from the closest point of the surface of the earth, provided it is never flown at a height greater than 120 metres above the remote pilot (UAS.OPEN.010(4)).
- The obstacle derogation opens no general right to climb higher: it is attached to the obstacle, to its 50-metre radius and to the request of the body responsible for it.
The trap. Most consumer controllers display a height relative to the take-off point, not to the ground being overflown: over broken terrain the conversion is the pilot’s job. Do not assume it impossible for all that: the Delegated Regulation opens to classes C1, C2 and C3 the alternative of a system that limits the height above the surface and then provides the remote pilot with clear information about it. Check what your machine really measures.
A diagram goes with this card: see it in the We Drone app.
Source
Implementing Regulation (EU) 2019/947 (CELEX 02019R0947, consolidated on 01/05/2025), Article 4, paragraph 1, point e), and Annex Part A, points UAS.OPEN.010(2), (3) and (4)