4.1 Site Selection, Segregation & Pre-Flight Briefing

Operational Mitigations Sit Beside the Distance Floors

Chapter 3 gave you the statutory horizontal floors (30 m normal, 5 m with low-speed mode after evaluation for UK2/C2; 50 m for legacy sub-2 kg A2) and the 1:1 height–distance practice. Those rules only work if the site can support them for the whole task—including take-off, transit, hover work, return, and contingency. Operational ground-risk mitigations are the planning and human-control measures that keep uninvolved persons out of the volume where the aircraft will fly and where it might go if control is degraded.

On the A2 CofC syllabus this is not soft “good practice” colour. UAS.OPEN.030 explicitly couples reduced separation (the 5 m privilege) to segregation of the overflown area, and the official self-practical training competencies expect a remote pilot who can show a coherent plan: where people are, how they will be kept clear, who is involved, and where the aircraft will land if the primary zone fails. Exam stems often describe a pretty façade job beside a busy path and ask whether 5 m (or even 30 m) is lawful and safe; the credited answer almost always starts with site selection, not stick skill.

Choose Sites That Protect the Flight and Failure Footprint

Think in two footprints, not one circle drawn around a tripod:

1. Flight footprint — the ground area under the planned path, hover positions, and camera angles for the whole sortie (including repositioning).
2. Failure footprint — where the aircraft could go if you lose link, lose GNSS hold, suffer a flyaway, experience a strong gust, or must descend immediately: downwind drift, residual energy after low-speed mode, RTH track, and emergency descent cone.

Uninvolved people must stay outside both footprints to the extent reasonably practicable for Open-category operations. Selecting a courtyard that is empty at 07:00 but flooded with school traffic at 15:30 is not “the same site.” Selecting a rooftop with only a 12 m yard between the façade and a public pavement may work for UK2 normal mode only if you can keep walkers beyond 30 m (and beyond 1:1 at height)—often you cannot, so the honest choice is another time, a different stand-off angle, an A3-compatible location, Specific-category authorisation thinking, or a lighter A1-class aircraft for true overflight tasks (A1 rules, not A2 overflight).

Practical site-selection questions

• Can I maintain the statutory floor and a sensible 1:1 buffer for every uninvolved person who might appear, not only those visible at take-off?
• Are approach routes (paths, gates, car parks, shop doors) controlled or predictable?
• Is there a natural barrier (fence, water, locked site, height difference) that supports segregation?
• Where will I put take-off and landing so that the first and last metres of flight do not overfly the public?
• If I must land now, is there a clear contingency patch that is still free of people and vehicles?

If the answer to several of these is “only if nobody walks by,” the site is wrong for A2 Near People work at the planned proximity.

Segregation of the Overflown Area

Segregation means the overflown (and near-overflown) ground is effectively kept free of uninvolved persons for the duration of the risk. It is not a single cone; it is a managed area. Methods that training materials and examiners recognise include:

• Physical control — closed site, locked gates, temporary barriers, vehicle road closures arranged with the right authority.
• Temporal control — fly when the park is closed, the street is empty, or the client has cleared the yard.
• Human control — marshals, spotters, or crew watching approach routes and stopping the public (politely, lawfully) from entering the buffer.
• Procedural control — only involved persons (briefed and accepting risk) inside the work zone; everyone else treated as uninvolved with full separation.

Segregation is critical for 5 m low-speed operations. The regulation does not let you engage low-speed mode in a crowded high street and declare 5 m because the aircraft is slow. Without segregation, the evaluation required before 5 m fails (Section 4.3). Even at 30 m, poor segregation turns a legal floor into a continuous series of emergency manoeuvres—which itself is a ground-risk and VLOS/attention problem.

Pre-Flight Briefing of Involved Persons

Involved persons are those who participate in the operation and have been informed of the risks so they can decide to accept them (typical examples: camera assistant, property manager standing in a defined safe zone, client representative who stays where instructed). Uninvolved persons have not accepted those risks and are not under the remote pilot’s operational control.

A short pre-flight briefing for involved persons should cover, in plain language:

• What the aircraft will do and roughly where it will fly.
• Where they must stand (and where they must not walk).
• How you will communicate (radio, phone, hand signals).
• What “stop / freeze / land now” means and who can call it.
• What to do if the aircraft approaches them unexpectedly (do not grab props; move clear laterally if safe).
• That they may leave the operation if they no longer accept the risk—and that leaving the briefed role may change how you treat their position.

Without briefing, people on site default to uninvolved for separation purposes. On the exam, a “client standing under the hover because they want a better view” is uninvolved (or at least not lawfully treated as a briefed involved person) until risk has been explained and accepted and they remain in the controlled plan.

Map FRZs, Obstacles, and Public Interfaces

Before you commit to A2 work near people, integrate airspace and ground picture:

• Flight Restriction Zones (FRZs) and other restricted or notified airspace around aerodromes—permission may be required; Near People privileges do not override FRZ rules.
• Obstacles — buildings, cranes, trees, power lines, glass façades that affect line of sight, GNSS multipath, and emergency landing options.
• Public interfaces — paths, parks, streets, school exits, shop fronts, bus stops. These are the usual places uninvolved people appear without warning.
• Take-off / landing zones — flat, clear, free of loose FOD, with room to approach without overflying heads; preferably inside the segregated area.
• Contingency landing areas — alternate patches if the primary pad is compromised by people, vehicles, or aircraft state (low battery, control issue).

A2 theory often pairs a separation question with an FRZ or obstacle distractor. The correct priority is: comply with airspace and Open-category rules first, then apply person-distance and segregation. You never “trade” FRZ compliance for a closer façade shot.

Document the Mental or Written Plan

Whether you keep a brief written site plan or a disciplined mental checklist, the official practical competencies and good professional practice call for the same elements:

1. Task objective and aircraft identity (class mark / legacy status, MTOM, mode plan).
2. Subcategory (A2 Near People) and applicable person floors (30/5 or 50 m).
3. Site layout: TO/L, contingency L, work volume, public approach routes.
4. Segregation method and who is involved vs uninvolved.
5. Weather and performance go/no-go (expanded in 4.3 for 5 m).
6. Abort triggers and recovery actions.
7. Airspace / FRZ / local restrictions checked.

You do not need a Specific-category operations manual for Open A2, but you do need to show that separation numbers were planned into a real site, not recited from memory after take-off. Exam options that praise “launch first, sort people later” are always wrong.

Worked Site Patterns

Pattern A — Private garden, fence intact, quiet morning. Client and one assistant briefed as involved; public path 40 m beyond the fence. UK2 normal mode façade work at 20 m AGL: statutory floor 30 m from uninvolved persons on the path; 1:1 wants ≥20 m—use ≥30 m to the path. Segregation of the garden itself is strong. Suitable for A2 if path users stay outside the buffer.

Pattern B — Urban street elevation, continuous footfall. No realistic segregation; low-speed mode will not unlock lawful 5 m ops. Even 30 m may be intermittent. Postpone, use elevated opposite stand-off if safe and legal, change aircraft/category concept, or seek different authorisation pathways—do not invent involvement for strangers.

Pattern C — Park at dawn for a film plate. Temporal segregation works until dog-walkers arrive. Brief crew; define a hard abort if anyone enters the 30 m (or 1:1) bubble. Contingency landing on the open grass away from the path.

Pattern D — “Just a quick 5 m product shot outside a shop.” Unless the pavement is controlled and low-speed evaluations pass, this is a classic fail. Shoppers are uninvolved; segregation is weak; 5 m is a privilege, not a default.

Memory Hooks for Section 4.1

1. Plan both footprints — flight path and failure path.
2. Segregate the area — especially before any thought of 5 m.
3. Brief involved persons — unbriefed people stay uninvolved for separation.
4. Map FRZs, obstacles, public routes, TO/L, contingency L.
5. Wrong site → change plan; do not hope the public cooperates.

Site selection is how statutory metres become real-world safety. Section 4.2 covers what to do when people still enter the bubble; Section 4.3 formalises the weather–performance–segregation gate before 5 m operations.