1.3 Class C2 UAS Technical Standards & Airspace Rules

Class C2 UAS Technical Standards & Airspace Rules

Class C2 Technical Architecture (Regulation (EU) 2019/945)

Part 3 of the Annex to Regulation (EU) 2019/945 (as amended by Regulation (EU) 2024/1108) lists the requirements a drone must meet to carry the Class C2 identification label. The points most relevant to A2 operations are:

1. Mass Threshold (point 1): An MTOM of less than 4 kg, including payload (gimbals, sensors, beacons, spotlights and any other attached equipment all count);
2. Height Limitation (point 2): Maximum attainable height above the take-off point limited to 120 m, or a height-limiting system set to 120 m or a pilot-selected value, with clear height information shown to the pilot;
3. Safe Design (points 4 and 6): Enough mechanical strength, no sharp edges unless technically unavoidable, and propellers designed to limit the injury they can inflict;
4. Loss-of-Link Behaviour and Link Security (points 7 and 8): Unless tethered, a reliable and predictable method to recover the command and control (C2) link or, if that fails, to terminate the flight in a way that reduces the effect on third parties. The C2 link must also be protected against unauthorised access;
5. Low-Speed Mode (point 9): Unless fixed-wing, a pilot-selectable low-speed mode limiting ground speed to no more than 3 m/s;
6. Noise (points 10 and 11): Unless fixed-wing, a guaranteed A-weighted sound power level ($L_{WA}$) within the published limits, with the value shown on the UA and/or its packaging;
7. Electric Power and Serial Number (points 12 and 13): Powered exclusively by electricity, with a unique serial number to ANSI/CTA-2063-A-2019;
8. Direct Remote ID and Geo-Awareness (points 14 and 15);
9. Low-Battery Warning (point 17): A clear warning when the battery reaches a low level, giving the pilot enough time to land safely;
10. Lights (point 18): Lights for controllability, plus at least one green flashing light so people on the ground can tell the drone apart from a manned aircraft at night;
11. Manufacturer's Instructions (point 19): Including the MTOM, allowed payloads, loss-of-link behaviour and operational limitations (including meteorological conditions).

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The Low-Speed Mode: Technical & Kinetic Dynamics

A defining technical mandate for Class C2 aircraft is the inclusion of a pilot-selectable low-speed mode.

Regulatory Velocity Limit

Under point (9) of Part 3 of Delegated Regulation (EU) 2019/945, a C2 aircraft (unless it is fixed-wing) must have a low-speed mode, selectable by the remote pilot, that limits its ground speed to no more than 3 m/s (approximately 10.8 km/h). A fixed-wing C2 aircraft has no such mode, so it cannot use the reduced 5 m distance and must keep at least 30 m.

The Physics of Kinetic Energy Reduction

The logic behind letting remote pilots close the distance to uninvolved bystanders from 30 m down to 5 m rests on basic Newtonian mechanics. Kinetic energy ($E_k$) is governed by the equation:

$E_k = \frac{1}{2} m v^2$

Because velocity ($v$) is squared, even a modest decrease in flight speed yields an enormous reduction in impact energy:

• Consider a Class C2 drone close to the 4 kg limit (use 4 kg to keep the numbers round) cruising at 15 m/s (54 km/h): $E_k = \frac{1}{2} \times 4\text{ kg} \times (15\text{ m/s})^2 = 2 \times 225 = 450\text{ Joules}$ An impact energy of 450 J from a hard airframe can cause severe or fatal injuries.

• Now consider the same 4 kg drone operating with low-speed mode active at 3 m/s: $E_k = \frac{1}{2} \times 4\text{ kg} \times (3\text{ m/s})^2 = 2 \times 9 = 18\text{ Joules}$

$\text{Energy Reduction} = \frac{450\text{ J} - 18\text{ J}}{450\text{ J}} = \frac{432}{450} = 96\%$

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Direct Remote Identification (DRI)

Every Class C2 unmanned aircraft must have a Direct Remote Identification (DRI) system (Part 3, point 14). Direct Remote ID is a local radio broadcast, using an open and documented protocol, that existing mobile devices nearby can receive directly. UAS.OPEN.030(3) requires it to be active and updated for A2 operations.

Mandatory DRI Data

In real time, throughout the whole flight, the aircraft must broadcast at least:

1. UAS Operator Registration Number: The operator's registration number, uploaded by the operator after a consistency (checksum) check. The 3 secret digits are used for that check and are not displayed;
2. UAS Serial Number: The unique serial number compliant with ANSI/CTA-2063-A-2019;
3. Time Stamp, Position and Height: The geographical position of the UA and its height above the surface or take-off point;
4. Route Course and Ground Speed: Course measured clockwise from true north, and ground speed;
5. Pilot Position: The geographical position of the remote pilot or, if not available, the take-off point;
6. Emergency Status: An indication of the emergency status of the UAS.

The system must also be designed to reduce the possibility of tampering with its functionality.

+-------------------------------------------------------------+
|               DIRECT REMOTE ID BROADCAST PACKET             |
+-------------------------------------------------------------+
| 1. Operator ID:       FIN87astrdge12k8 (16-char number)     |
| 2. Serial Number:     1581F45AB67890123 (ANSI/CTA-2063-A)   |
| 3. Current Position:  48.8584° N, 2.2945° E, Height: 84 m   |
| 4. Ground Vector:     Track: 142°, Ground Speed: 2.8 m/s    |
| 5. Pilot / Base Pos:  48.8579° N, 2.2938° E                 |
| 6. Timestamp:         2026-10-05T14:32:00Z                  |
| 7. System Status:     NORMAL (No Failsafe / Emergency)      |
+-------------------------------------------------------------+

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Onboard Geo-Awareness Systems

Class C2 aircraft must include a geo-awareness function (Part 3, point 15), and UAS.OPEN.030(3) requires it to be active and updated in A2:

• Data Loading: An interface to load and update data on the airspace limitations set by UAS geographical zones (Article 15 of Regulation (EU) 2019/947). Member States publish these zones in a common digital format based on the EUROCAE ED-269 data model;
• Warning: A warning alert to the remote pilot when a potential breach of an airspace limitation is detected;
• Status Information: Information on the UA's status, and a warning when its positioning or navigation systems cannot ensure that geo-awareness works properly.

Geo-awareness is a warning function. Some drones also have a function that actively blocks entry into certain zones (point 16); if fitted, it must interact smoothly with the flight controls and tell the pilot when it is preventing entry.

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Open Category Airspace Limits: The 120-Meter Height Ceiling

Under Article 4(1)(e) of Regulation (EU) 2019/947, all Open category operations are subject to a maximum flight height of 120 m (400 ft) above the nearest point of the surface of the earth.

The Surface-Following Measurement Rule

The 120-meter limit is not measured from the pilot's take-off location; it is measured perpendicularly from the nearest point of the terrain. When flying over undulating ground, hills, or valleys, the remote pilot must actively adjust aircraft altitude to remain within a 120-meter vertical bubble relative to the ground surface directly below.

                           120 m Maximum Vertical Clearance
                 <--------------------------------------------------->

                       Drone Flight Path (Max 120 m AGL)
           . - - - - - - - - - - - - - - - - - - - - - - - - - - - - .
          /                                                           \
         /   ^                                                         \   ^
        /    | 120 m                                                    \  | 120 m
       /     v                                                           \ v
______/   Hilltop   _________________________________ Valley ___________\__________
Terrain Surface Profile

The Artificial Structure Exception (UAS.OPEN.010(3))

The regulation itself provides an exception to the 120-meter limit near tall infrastructure:

• Eligible Structures: Artificial obstacles taller than 105 m (e.g., radio communication towers, wind turbines, industrial cooling towers, high-rise buildings);
• Request of the Responsible Entity: The increase applies only at the request of the entity responsible for the obstacle. GM1 UAS.OPEN.010 says that entity must explicitly give the operator permission;
• Horizontal Constraint: The aircraft must remain within a horizontal distance of 50 m from the artificial obstacle;
• Vertical Ceiling: The maximum flight height may be increased up to 15 m above the highest point of the obstacle.

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Visual Line of Sight (VLOS) and Visual Observers

All operations in the Open Category must be conducted within Visual Line of Sight (VLOS) at all times:

• Definition (Article 2(7)): A type of UAS flight in which the remote pilot is able to maintain continuous unaided visual contact with the unmanned aircraft, allowing the pilot to control the flight path to avoid collisions with other aircraft, people, and obstacles.
• Permitted Visual Aids: Remote pilots may wear corrective eyeglasses and contact lenses. However, the use of optical magnifying devices—such as binoculars, monoculars, telescopes, or viewing the aircraft solely through a video screen—is strictly prohibited for maintaining VLOS.

First Person View (FPV) Operations

When flying using First Person View (FPV) goggles or monitors where the remote pilot does not look directly at the aircraft:

• Article 4(1)(d) allows the UA to be kept in VLOS by an unmanned aircraft observer. GM explains that the observer is situated alongside the remote pilot, and UAS.OPEN.060(4) requires clear and effective communication between the two;
• The VO must maintain continuous, unaided visual contact with the unmanned aircraft;
• The VO continuously scans the surrounding airspace for approaching manned traffic, birds, and ground hazards, providing immediate verbal warnings to the remote pilot;
• The visual observer is not permitted to use optical magnification (binoculars).