PPL(A) Theory

Aerodrome control and visual separation near aerodromes

Page ID
010-07-02
Syllabus (AMC1 FCL.210; FCL.215)
Visual separation in the vicinity of aerodromes; Procedures for aerodrome control services
Syllabus anchor
ICAO Annex 11; Doc 4444
Rule in force
Reg. (EU) 2017/373 (ATM/ANS); SERA
Regulatory baseline
SERA EAR August 2025; ATM/ANS EAR March 2025; ICAO Annex 11 (2018) and Doc 4444 (2016) for comparison
Reading time
26 min
Revising? Key concepts ↓ Test yourself ↓

Learning objectives

The idea

Near an airfield many aircraft share a small space. Some are in the air, some are rolling on the ground, some are crossing the runway. A tower exists to stop them meeting. It does this by deciding who goes next, giving permission one step at a time, and passing on what it can see. Your part is to do only what you have been cleared to do, and to keep looking outside, because the tower does not always keep you apart from everybody. Sometimes the separation is something you and the other pilot create by sight.

Who the tower controls

Aerodrome control service is the air traffic control (ATC) service given to aerodrome traffic, and the aerodrome control tower is the unit set up to give it.

"Aerodrome traffic" is wider than "aircraft on the ground". It means all traffic on the manoeuvring area plus all aircraft flying in the vicinity of the aerodrome, including those entering or leaving the traffic circuit. The circuit is the specified path flown by aircraft near an aerodrome. The manoeuvring area is the part used for take-off, landing and taxiing, excluding aprons; adding the aprons gives the movement area. Definitions: 010-05-01.

Who controls what around an aerodrome Left: the circuit and vicinity above, then the movement area containing the manoeuvring area (runway and taxiways) and, outside the manoeuvring area, the apron. Right: the aerodrome controller handles the runway and aircraft flying in the tower's area, the ground controller handles the manoeuvring area except runways, and clearance delivery passes start-up and ATC clearances to departing IFR flights. Circuit and vicinity Aircraft flying in the tower's area Movement area Manoeuvring area Runway Taxiways Apron Not part of the manoeuvring area Aerodrome controller Runway and aircraft flying in the tower's area Clearance delivery IFR departures: start-up and ATC clearances Ground controller Manoeuvring area except runways Tower aim: no collisions in its area
Figure 2. The tower's work may be split between positions. The apron is part of the movement area but not of the manoeuvring area. Original diagram
Describe this figure

On the left, a dashed box holds the circuit and vicinity above a larger movement-area box. Inside the movement area, the manoeuvring area holds the runway and taxiways, and a separate dashed apron box lies outside the manoeuvring area. On the right, the aerodrome controller handles the runway and aircraft flying in the tower's area, and the ground controller handles the manoeuvring area except runways. A dashed box shows clearance delivery, which passes start-up and ATC clearances to departing IFR flights. A last box says the tower's aim is no collisions in its area.

The figure shows the tower at the centre of two zones. The inner zone is the manoeuvring area: runway and taxiways. Around it is the airspace of the circuit, which the tower also controls. The apron is drawn outside it, as part of the movement area only.

The tower's objective is collision prevention on and near the aerodrome: between aircraft in its area including the circuits, aircraft on the manoeuvring area, landing and departing aircraft, aircraft and vehicles, and aircraft and obstructions.

It watches by looking out of the window or through a visual surveillance system such as a remote tower, and by an ATS surveillance system where available. In a busy tower the work is split: the aerodrome (runway) controller handles the runway and aircraft flying in the tower's area, the ground controller handles the manoeuvring area except runways, and clearance delivery passes ATC clearances to departing IFR flights.

Following a flight through the tower's hands

The tower gives permission at six places on your journey. The figure is an aerodrome plan with a left-hand circuit and the six positions numbered.

Six places where the tower gives clearances Plan of an aerodrome with a runway, a parallel taxiway, an apron, a tower and a left-hand circuit. Six numbered badges mark the places where the tower normally gives clearances, from the taxi call at the apron to parking. Tower Runway Apron Taxiway Left-hand circuit 1 2 3 4 5 6 1 Taxi call: runway information, taxi clearance 2 Runway-holding position: hold; run-up 3 Take-off clearance, if not given at 2 4 Landing clearance, in the circuit or on final 5 After landing: clearance to taxi to the apron 6 Parking information
Figure 1. An invented aerodrome with a left-hand circuit. The tower normally gives its clearances at these six places, and where practicable it does not wait for the pilot to call. Original diagram
Describe this figure

A plan shows a runway, a parallel taxiway with two links, an apron with a tower beside it, and a dashed left-hand circuit around the runway. Six numbered badges mark where the tower normally gives clearances: 1 on the apron for the taxi call, 2 at the runway-holding position where the aircraft holds for traffic or runs up, and 3 on the runway for take-off clearance if it was not given at 2. Badge 4 is on final for the landing clearance, 5 is at the exit link for the clearance to taxi to the apron, and 6 is on the apron for parking information.

  1. Taxi call: you receive runway information and your taxi clearance.
  2. Holding point: you hold if there is conflicting traffic, or do an engine run-up.
  3. Take-off clearance, if it was not practicable at position 2.
  4. Landing clearance, in the circuit or on final.
  5. After landing, clearance to taxi to the apron.
  6. Parking information. Where practicable, clearances come without waiting for your call.

Before you taxi, the tower gives you, unless you already have it: runway, surface wind, QNH (QFE on request or by local arrangement), visibility if it is below 10 km (or RVR), and the correct time. The tower selects the runway-in-use from wind and other local factors, and aircraft normally land and take off into wind. If a clearance does not suit you, tell ATC and ask for an amended one.

Rule SERA.8015(b)(7)

At a controlled aerodrome you must not taxi on the manoeuvring area without clearance from the tower, and you must comply with its instructions.

In the circuit

A clearance to enter the circuit is used when the tower wants you to approach in accordance with the circuit but cannot yet give landing clearance. You may be cleared to join at any position in the circuit. When the controller so instructs, pilots should obtain approval before turning onto any circuit leg (good practice).

A landing aircraft normally has priority over a departure. Landing priority goes first to an aircraft expecting to be compelled to land, then to medical-urgency aircraft, then to search and rescue aircraft, then to others as the competent authority decides.

Runway separation

For a departure, the tower does not let an aircraft start its take-off until the preceding departure has crossed the end of the runway-in-use or started a turn, or until all preceding landing aircraft are clear of the runway. For an arrival, the tower does not let a landing aircraft cross the threshold until the preceding departure has crossed the end of the runway or started a turn, or all preceding landing aircraft are clear of the runway.

Take-off clearance is issued when there is reasonable assurance that runway separation will exist when you start the take-off, when you are ready and at or approaching the runway, and when traffic permits. Landing clearance may be given when there is reasonable assurance that runway separation will exist when you cross the threshold, but not before a preceding landing aircraft has crossed the threshold.

Reduced runway separation minima

Some aerodromes shorten these gaps for light propeller traffic: reduced runway separation minima (RRSM). The ATS provider may prescribe them after a safety assessment for each runway. They apply only in daylight, from 30 minutes after local sunrise to 30 minutes before local sunset.

Three categories are used, by maximum certificated take-off mass (MCTOM). Category 1 is a single-engine propeller aeroplane of 2 000 kg or less. Category 2 is a single-engine propeller aeroplane over 2 000 kg but under 7 000 kg, or a twin-engine propeller aeroplane under 7 000 kg. Category 3 is everything else.

The conditions are strict and come from an AMC. RRSM are not applied between a departure and a preceding landing aircraft, and wake minima still apply. Visibility must be at least 5 km, the ceiling not lower than 1 000 ft, the tailwind component not above 5 kt, and braking unaffected by contaminants. The controller needs landmarks or similar to judge distances, the succeeding aircraft gets traffic information, and two departures must still be separated right after the second gets airborne.

For landing, a following Category 1 may cross the threshold when a preceding Category 1 or 2 has passed at least 600 m from the threshold. A following Category 2 needs the preceding Category 1 or 2 at least 1 500 m along. Behind any preceding Category 3, any landing aircraft needs it at least 2 400 m along. For departure, the same three distances apply, measured from the succeeding aircraft's position to the preceding aircraft once it is airborne.

Runway separation: standard positions and reduced distances A runway seen from above with the following aircraft at the threshold and marks at 600 m, 1 500 m and 2 400 m. Below it, the reduced distance for each category pairing, the standard positions, the conditions for reduced minima and the three aircraft categories. Following aircraft 0 m 600 m 1 500 m 2 400 m Leader Runway continues 600 m: Cat 1 behind Cat 1 or 2 1 500 m: Cat 2 behind Cat 1 or 2 2 400 m: any aircraft behind Cat 3 Cat 3 behind Cat 1 or 2: none listed Standard position, before the follower goes Departed leader: crossed the runway end or started a turn Landed leader: clear of the runway Landing clearance: not before a preceding landing aircraft has crossed the threshold Reduced distances need all of these Prescribed by the ATS provider Daylight: from 30 min after sunrise to 30 min before sunset Visibility 5 km or more Ceiling 1 000 ft or higher Tailwind 5 kt or less Wake minima still apply Never: leader landed, follower departs Categories, by maximum take-off mass Cat 1: single-engine propeller, 2 000 kg or less Cat 2: single-engine propeller over 2 000 kg, or twin-engine propeller; both under 7 000 kg Cat 3: all other aircraft
Figure 3. Choose the leading and following aircraft to read the position the leader must reach. Without scripts, the picture and lists show every reduced distance. Original interactive
Describe this figure

A runway is drawn from above with the following aircraft at the threshold (0 m) and dashed marks at 600 m, 1 500 m and 2 400 m. The standard rule is that the leader has crossed the runway end or started a turn if it departed, or is clear of the runway if it landed. Reduced distances are 600 m for a Category 1 behind a Category 1 or 2, 1 500 m for a Category 2 behind a Category 1 or 2, and 2 400 m for any aircraft behind a Category 3. They need the ATS provider's prescription, daylight, visibility of 5 km or more, a ceiling of 1 000 ft or higher and a tailwind of 5 kt or less, and wake minima still apply. They are never used for a departure behind a landing aircraft. In the interactive version, four selects choose each aircraft's category and movement, and the leader moves to the matching mark.

The figure is interactive: choose the leader's and follower's category and whether the leader departs or lands, and it shows the position the leader must reach and, under RRSM, the distance. The static drawing shows a runway strip with 600 m, 1 500 m and 2 400 m marks.

Rule AMC9 ATS.TR.210(c)(2)(i)

Reduced runway separation distances are 600 m, 1 500 m or 2 400 m depending on the categories, in daylight only, and only if the prescribed conditions are met.

Wake turbulence for a light aeroplane

Heavier aircraft leave rough air behind them, and the minima give it time to decay. ATC applies wake minima in approach and departure when an aircraft is directly behind another at the same altitude or less than 1 000 ft below, on the same runway or parallel runways less than 2 500 ft (760 m) apart, or crossing behind.

There are four wake categories by MCTOM. SUPER (J) is a list of types. HEAVY (H) is 136 000 kg or more. MEDIUM (M) is under 136 000 kg but over 7 000 kg. LIGHT (L) is 7 000 kg or less, which covers many twins as well as small singles.

As a LIGHT departing behind a MEDIUM or a HEAVY, you are separated by 2 minutes from the same runway, from close parallel runways, or where flight paths cross. From an intermediate part of the runway it is 3 minutes. Behind a SUPER it is 3 minutes, or 4 from an intermediate part. These minima apply to VFR departures too, because the exemption covers arrivals only.

For arrivals, the time minima are 3 minutes for a LIGHT behind a HEAVY or MEDIUM and 4 minutes behind a SUPER. They are not applied to an arriving VFR flight that has reported the preceding aircraft in sight and been told to follow and maintain its own separation. ATC then issues a caution for wake turbulence.

Wake turbulence time minima for a LIGHT aeroplane that follows another aircraft
LIGHT behind a… Departure: same runway, parallel runway under 760 m, or crossing paths Departure from an intermediate part of the runway Displaced threshold, or opposite-direction low or missed approach, paths expected to cross Arrival, not VFR and not a visual approach Arrival, VFR or visual approach, with the leader reported in sight
MEDIUMover 7 000 kg, under 136 000 kg 2 min3 min2 min3 min No time minimum. ATC gives a wake turbulence caution.
HEAVY136 000 kg or more 2 min3 min2 min3 min No time minimum. ATC gives a wake turbulence caution.
SUPERtypes in the ICAO list 3 min4 min3 min4 min No time minimum. ATC gives a wake turbulence caution.
LIGHT means 7 000 kg or less. Wake minima apply when the following aircraft is directly behind, or crosses behind, at the same altitude or less than 1 000 ft below. The departure columns apply to VFR departures too.
Figure 4. What a LIGHT aeroplane waits for behind a heavier one. A VFR arrival that has the leader in sight gets a caution instead of a time. Original table
Describe this figure

One row for each heavier category, MEDIUM, HEAVY and SUPER, gives the wait for a LIGHT aeroplane. A departure from the same runway, a close parallel runway or a crossing path waits 2 min behind MEDIUM or HEAVY and 3 min behind SUPER. A departure from an intermediate part of the runway waits 3 min behind MEDIUM or HEAVY and 4 min behind SUPER. The displaced-threshold and opposite-direction missed-approach cases give 2 min, or 3 min behind SUPER. An arrival that is not VFR and not a visual approach waits 3 min behind MEDIUM or HEAVY and 4 min behind SUPER, while a VFR arrival with the leader in sight gets no time minimum and a wake turbulence caution.

The table lists what a light aeroplane meets: departure times from the runway start and from an intermediate part, the 2 minute displaced-threshold and opposite-direction cases, and, for VFR arrivals, a caution instead of a time.

A caution is information, not separation. The pilot-in-command remains responsible for acceptable spacing behind a heavier aircraft, and should tell ATC if more is needed. Times here do not replace ATO instruction or your aircraft's POH/AFM.

Visual separation near aerodromes

ATC separation is normally vertical or horizontal. The exceptions include parallel runway operations and "when a reduction in separation minima in the vicinity of aerodromes can be applied". The conditions for that reduction are in an EU AMC, and ICAO states the same ones, so there is no EU-ICAO difference.

Near aerodromes the lateral and longitudinal minima may be reduced if any one of three conditions holds. First, each aircraft is continuously visible to the aerodrome controller, who can provide adequate separation. Second, each aircraft is continuously visible to the crews of the other aircraft concerned, and the pilots report they can maintain their own separation. Third, one aircraft follows another, and the follower's crew reports the other in sight and that separation can be maintained.

A related EU tool: In Class D and E airspace below 10 000 ft, in climb or descent, by day in VMC, a flight may be cleared to maintain its own separation for a specific portion of flight if the pilot requests it, the other pilot agrees and the competent authority has prescribed it. For a VFR flight, a clearance to maintain own separation and remain in VMC only signals that ATC is not providing separation for that time. You must still avoid creating a collision hazard.

Visual separation near aerodromes: the three conditions EU rules: normal separation is vertical or horizontal, with an exception for reduced minima near aerodromes. That reduction is allowed when any one of three conditions holds: the controller sees each aircraft, the pilots see each other and can keep their own separation, or the follower has the leader in sight. ICAO states the same three conditions. Also shown: own separation in Class D or E, the wake caution for VFR arrivals, and ICAO circuit spacing. EU rules Normal separation vertical or horizontal (longitudinal or lateral) except Exceptions parallel runway operations; reduced minima near aerodromes Reduced minima: any one is enough (a) The controller sees each aircraft all the time and can separate them (b) The pilots see each other and report they can keep their own separation (c) The follower reports the leader in sight and can keep separation ICAO states the same three conditions Own separation, Class D or E below 10 000 ft, climb or descent, day VMC; the pilot asks, the other pilot agrees, the authority has prescribed it VFR arrival, leader in sight: no wake time minimum, ATC gives a caution ICAO Circuit spacing Aircraft are spaced in flight so runway and wake minima can be met
Figure 5. Near aerodromes the normal separation may be reduced if any one of three conditions holds. ICAO states the same three conditions. Original diagram
Describe this figure

The EU rules panel says normal separation is vertical or horizontal, with exceptions for parallel runway operations and for reduced minima near aerodromes. That reduction is allowed when any one of three conditions holds: (a) the controller sees each aircraft all the time and can separate them, (b) the pilots see each other and report they can keep their own separation, or (c) the follower reports the leader in sight and can keep separation. A note says ICAO states the same three conditions. Two more EU boxes show own separation in Class D or E (below 10 000 ft, climb or descent, day VMC, pilot asks, other agrees, authority prescribed it) and the VFR arrival rule: no wake time minimum, only a caution. A last box, labelled ICAO, says circuit aircraft are spaced in flight so runway and wake minima can be met.

The figure has two halves. The top half is the EU legal hook: the exception for reduced minima near aerodromes, and the own-separation clearance. The bottom half shows the three conditions, which the EU AMC and ICAO state alike: the controller sees both, the pilots see each other, and the follower has the leader in sight.

Taxiing and runway incursion

A runway incursion is any occurrence where an aircraft, vehicle or person is incorrectly present on the protected area of a surface designated for landing and take-off. A runway-holding position is a designated place that protects a runway, an obstacle limitation surface or an ILS/MLS critical area, where taxiing traffic stops unless the tower authorises otherwise. On the radio it is the "holding point". A hot spot is a place with a history or risk of collision or runway incursion.

If the taxi limit is beyond a runway, the taxi clearance contains an explicit clearance to cross or an instruction to hold short of that runway. You stop and hold at all runway-holding positions unless explicitly cleared to enter or cross. You stop at all lit stop bars and must not cross one; you may continue, per the clearance, when the bars are switched off. Stop bars are rows of red lights across a taxiway, used only where aerodrome control service exists.

Read-back is mandatory for clearances and instructions to enter, land on, take off from, hold short of, cross, taxi and backtrack on any runway, and for the runway-in-use. The tower guards the runway too: aircraft are not held closer than a runway-holding position, and not allowed to line up at the approach end of a runway-in-use while another aircraft is landing, until the lander has passed the point of intended holding. If, after a take-off or landing clearance, the controller becomes aware of an actual or imminent runway incursion or an obstruction, the controller cancels the take-off clearance or instructs the landing aircraft to go around, and tells you what and where.

If unsure of your position on the manoeuvring area, stop and tell ATS at once with your last known position. If you recognise you are on a runway, notify ATS, vacate onto a nearby suitable taxiway as quickly as possible unless told otherwise, then stop.

Runway incursion barriers as layers A taxiing aircraft heads for the runway through eight layers, each with a hole. Layers 1 to 7 are rules: holding-position marking, lit stop bar, explicit clearance, read-back, controller holding and line-up limits, the controller's last defence, and the pilot's action when in doubt. Layer 8 is good practice. An incursion needs every layer to fail. Taxiing aircraft heading for the runway 1 Holding-position marking Taxiing aircraft stop and hold here RULE 2 Lit stop bar Lit: stop. Off: proceed as cleared RULE 3 Explicit clearance Enter or cross only when cleared RULE 4 Read-back Read back runway clearances and instructions RULE 5 Controller: holding, line-up Held at the holding position; no line-up while another lands RULE 6 Controller: last defence Cancels take-off or orders a go-around; says what and where RULE 7 Pilot in doubt Stop and tell ATS. On a runway, say so, vacate, then stop RULE 8 Good habits Brief the route, note hot spots, scan before entering, listen out PRACTICE Runway: every layer must fail
Figure 6. Each layer can fail, so there are several. Layers 1 to 7 are rules; layer 8 is good practice and is marked as such. Original diagram
Describe this figure

A taxiing aircraft at the top heads towards the runway through eight stacked layers, each with a hole, and a dashed arrow threads through every hole. Layers 1 to 4 are the holding-position marking, the stop bar (lit means stop, off means proceed as cleared), the explicit clearance to enter or cross, and the read-back of runway clearances and instructions. Layers 5 and 6 are the controller's limits on holding and lining up, and the controller's last defence: cancel the take-off or order a go-around and say what and where. Layer 7 is the pilot in doubt, who stops and tells ATS, or on a runway says so, vacates to a taxiway and then stops. Layers 1 to 7 carry a RULE tag; layer 8, brief the route, note hot spots, scan and keep listening, carries a PRACTICE tag. The runway bar says an incursion needs every layer to fail.

The figure shows barriers as layers, each with gaps: holding-position marking, stop bar, explicit crossing clearance, your read-back, and the controller's cancel or go-around. An incursion happens when the gaps line up.

Good practice

Your own barriers: brief the taxi route with the chart and note hot spots; write down and read back the clearance; ask if in doubt; scan the approach path before entering a runway; and keep listening to the tower to build a picture of who is landing and departing.

Conditional clearances on the runway

A conditional clearance only takes effect when a stated condition is met, for example "behind the landing aircraft". On the active runway it must not be used unless both the controller and the pilot can see the aircraft or vehicle concerned. The aircraft causing the condition must be the first to pass in front of you, and the order is call sign, condition, clearance, then a brief reiteration of the condition. Phrases: 010-07-05.

Rule SERA.8015(ec)

Conditional clearances must not be used for movements affecting the active runway unless the controller and the pilot both see the aircraft or vehicle concerned; the condition aircraft must be the first to pass in front.

Receiving one obliges you to identify the aircraft causing the condition before you act. A typical form: "CS-ABC, behind the Cessna on short final, line up behind."

Traffic, vehicles and conditions

The tower gives essential local traffic information, known to it, without delay to the departing and arriving aircraft concerned. That means any aircraft, vehicle or person on or near the manoeuvring area, or traffic in the climb-out or final approach area, that may be a hazard to you. If safety requires, the tower, approach or the competent authority may suspend VFR operations on and near the aerodrome.

Worked examples

Worked example

Example 1: reduced runway separation on landing. Given: CS-ABC, single-engine propeller, 2 400 kg MCTOM, follows a single-engine aeroplane of 1 100 kg. RRSM are in use, all conditions met. The preceding aeroplane is 1 000 m from the threshold. Method: CS-ABC is over 2 000 kg and under 7 000 kg, so Category 2. The preceding one is 2 000 kg or less, so Category 1. A following Category 2 needs the preceding Category 1 or 2 at least 1 500 m from the threshold. Working: 1 500 m minus 1 000 m = 500 m. Answer: the preceding aeroplane must travel a further 500 m before CS-ABC may cross the threshold. This is a regulatory exercise and does not replace ATO instruction or your aircraft's POH/AFM.

Worked example

Example 2: earliest departure behind a MEDIUM. Given: a MEDIUM aeroplane departs at 0941. CS-ABC is LIGHT and departs from an intermediate part of the same runway. Simplification: count the minimum from the preceding take-off time. Method: a LIGHT behind a MEDIUM from an intermediate part needs 3 minutes. Working: 41 + 3 = 44 minutes past the hour. Answer: 0944 at the earliest, one minute later than from the runway start.

In the real world

Real world BEA2023-0004

On 31 December 2022 at Bordeaux-Mérignac, a Robin DR400 (F-GTZY) was lined up at the threshold and told to wait because of the wake of a departing A321. One controller was working several combined positions with dense VFR traffic. The controller cleared an Airbus A320 (OE-INE) to land while forgetting the DR400 was on the runway. The DR400 pilot reported being at the threshold, the A320 was sent around, and it passed over the DR400 at a height of 178 ft. The A320 crew never saw it, and the controller realised only when the DR400 pilot called. The investigation pointed to divided attention and insufficient staffing. Listening to the frequency is one of your own barriers. Report: https://bea.aero/fileadmin/user_upload/OE-INE_EN.pdf

Exam traps

Exam trap

"The tower separates me from every other aircraft in the circuit." In most control zones (Class D), a VFR aeroplane is not separated from other VFR or IFR traffic. It gets traffic information, while the tower's overall aim remains collision prevention.

Exam trap

"Cleared to land means the runway is clear right now." Landing clearance can be issued with reasonable assurance that separation will exist when you cross the threshold, and only after the preceding lander has crossed the threshold.

Exam trap

"A conditional clearance can be used whenever ATC wants." Not for runway movements unless controller and pilot both see the traffic, and the condition aircraft must be the first to pass in front of you.

Exam trap

"If no stop bar is lit, or my route crosses a runway, I may cross." At a holding position an explicit clearance to enter or cross is always required, and a taxi clearance beyond a runway must say cross or hold short.

Exam trap

"If I can see the other aircraft, I may decide the separation myself." Reduced separation near aerodromes needs one of the three conditions: the controller sees both, each crew sees the other and reports it can keep own separation, or the follower reports the leader in sight. And VFR departures are not exempt from wake minima: the exemption is for arrivals only.

Explain it back

Explain it back

Explain to a fellow student who is separating whom when you follow an aircraft you have in sight in the circuit of a controlled aerodrome. Which of the three conditions applies, who keeps the separation, and what is the tower still doing for you?

Self-check

  1. Which of these is part of 'aerodrome traffic' at a controlled aerodrome?
    mcq · easy
    Show answer

    Aerodrome traffic is all traffic on the manoeuvring area plus all aircraft flying in the vicinity of the aerodrome, including those entering or leaving the traffic circuit. The first option leaves out aircraft flying near the aerodrome. The third makes the definition depend on radio contact, which it does not. The fourth wrongly limits it to IFR flights; the service covers all aerodrome traffic.

    Reference: SERA Article 2(9); SERA.8001(d)

  2. Near an aerodrome, which statement about reducing the normal lateral or longitudinal separation minima is correct?
    mcq · medium
    Show answer

    Any one of the three conditions is enough: the controller continuously sees each aircraft and can separate them; each crew continuously sees the other and the pilots report they can keep own separation; or a follower reports the leader in sight and that separation can be maintained. The EU AMC and ICAO agree. All three together is too strict. The EU AMC does list the conditions, so the third option is wrong. A bare pilot report without the other elements of a condition is not enough, so the last option is wrong.

    Reference: SERA.8005(c); AMC3 ATS.TR.210(c)(2)(b); ICAO Doc 4444, 6.1

  3. You are holding short of the active runway. The tower says: 'CS-ABC, behind the landing Cessna on short final, line up behind.' You cannot see any Cessna. What is the correct response?
    mcq · medium
    Show answer

    A conditional clearance affecting the active runway must not be used unless both controller and pilot see the aircraft causing the condition. You must identify it before acting. If the clearance does not suit you, tell ATC so an amended clearance can be given. The first option ignores that you must see it too. The second acts before the condition is met. The fourth passes the holding position without an explicit clearance.

    Reference: SERA.8015(ec); ATS.TR.235(f); SERA.8015(b)(4); SERA.3210(d)(2)

  4. Reduced runway separation minima are in use in daylight and all conditions are met. CS-ABC, a single-engine propeller aeroplane of 1 200 kg, is on final behind an 8 000 kg twin-engine propeller aeroplane that has landed and is now 1 800 m from the threshold. How much further must the preceding aeroplane travel before CS-ABC may cross the threshold?
    mcq · hard
    Show answer

    The 8 000 kg twin is over 7 000 kg, so it is Category 3, and behind a Category 3 any landing aircraft needs it at least 2 400 m from the threshold: 2 400 m minus 1 800 m is 600 m. Zero would apply only if the 2 400 m were already reached. 300 m and 1 200 m do not follow from the 2 400 m minimum; 600 m is also the Category 1 behind Category 1 or 2 distance, which does not apply here.

    Reference: AMC9 ATS.TR.210(c)(2)(i)(c); AMC9 ATS.TR.210(c)(2)(i)(f)(1)

  5. A MEDIUM aeroplane takes off at 1032. CS-ABC, a LIGHT aeroplane flying VFR, will depart from an intermediate part of the same runway. What is the earliest take-off time under the time-based wake minimum?
    mcq · hard
    Show answer

    A LIGHT departing behind a MEDIUM from an intermediate part of the same runway needs 3 minutes: 1032 plus 3 minutes is 1035. 1034 would be the 2 minute value from the runway start. 1036 would be 4 minutes, which applies behind a SUPER. The last option is wrong because the VFR exemption covers arrivals only, not departures. Assumption: the minimum is counted from the preceding take-off time.

    Reference: AMC3 ATS.TR.220; SERA.8012(b)

Key concepts

Written with ASD-STE100 writing principles: short sentences, one topic per sentence, active voice, one word for one meaning.

01

Aerodrome collision prevention

The tower issues information, instructions and clearances to prevent collisions near the aerodrome. Its area covers the aerodrome traffic circuit, the manoeuvring area and the runway.

Rule: AMC1 ATS.TR.205(c)(a)

02

Visual separation near aerodromes

Near an aerodrome, the normal vertical and horizontal separation minima can be reduced. SERA allows this reduction, and an AMC lists the conditions.

Rule: SERA.8005(c); ATS.TR.210(c)

AMC3 ATS.TR.210(c)(2)(b) lists three conditions. The minima can be reduced when any one of them holds, and ICAO Doc 4444 states the same three conditions.

Rule: AMC3 ATS.TR.210(c)(2)(b)

  1. The aerodrome controller sees each aircraft continuously and can provide adequate separation.

  2. The pilots see each other continuously and report that they can keep their own separation.

  3. One aircraft follows another, and its crew reports the other in sight and can keep separation.

Do not: Treat the AMC conditions as mandatory text.

03

VFR flights in a control zone

A VFR flight in a control zone (CTR) receives traffic information, not separation, from the tower. The tower does not separate VFR flights from other VFR flights in Class D airspace.

A VFR arrival that reports the preceding aircraft in sight can be told to follow and maintain own separation. The wake minima do not apply to that arrival, and the tower gives a wake turbulence caution instead.

Rule: SERA.8012(b)

Do not: Assume that a VFR flight gets separation from other VFR traffic in Class D.

04

Conditional clearance

A conditional clearance links one movement to the action of another aircraft or vehicle. The tower must not use a conditional clearance on the active runway unless both the controller and the pilot can see the aircraft involved.

Rule: SERA.8015(ec)

The aircraft that causes the condition must be the first one to pass in front of the other aircraft.

The clearance has four elements, in this order:

  1. Call sign.

  2. Condition.

  3. Clearance.

  4. Brief reiteration of the condition.

The pilot identifies the aircraft that causes the condition before the pilot acts on the clearance.

Do: Identify the aircraft that causes the condition before you act.

05

Runway-holding position and stop bar

A taxiing aircraft stops at every runway-holding position unless the tower explicitly clears it to enter or cross the runway.

Rule: SERA.3210(d)(2), (3)

The pilot stops at a lit stop bar. The pilot must not cross it until the lights are switched off and the clearance allows it.

The pilot must read back every clearance to enter, land on, take off from, hold short of, cross, taxi and backtrack on a runway.

Rule: SERA.8015(e)(1)(ii), (iii), (e)(2)

The tower normally gives an explicit clearance to cross, or an instruction to hold short, when the taxi route passes a runway.

Do not: Cross a lit stop bar.

06

Landing clearance

The tower can give a landing clearance when there is reasonable assurance of runway separation at the threshold. The tower does not give the clearance before the preceding landing aircraft has crossed the threshold.

Rule: AMC18 ATS.TR.210(a)(3)

Normally, the tower does not let a landing aircraft cross the threshold until the preceding departure has crossed the runway end or started a turn.

The landing aircraft can also cross the threshold when all preceding landing aircraft are clear of the runway.

Rule: AMC8 ATS.TR.210(c)(2)(i)

07

Wake turbulence category

The tower sorts aircraft into four wake turbulence categories by maximum certificated take-off mass (MCTOM). LIGHT is 7 000 kg or less, and HEAVY is 136 000 kg or more, except SUPER types.

Rule: AMC1 SERA.8012

The tower applies a 2 min time-based minimum when a LIGHT or MEDIUM aircraft departs behind a HEAVY aircraft on the same runway. The minimum rises to 3 min when the lighter aircraft starts from an intermediate part of the runway.

Rule: AMC3 ATS.TR.220(c), (d)

The time-based arrival minima do not apply to arriving VFR flights or visual approaches.

Rule: AMC2 ATS.TR.220

Do not: Apply the arrival time-based minima to a VFR arrival.

08

Essential local traffic

The tower gives essential local traffic information without delay to the aircraft it concerns. Essential local traffic is traffic on or near the manoeuvring area, or in the climb-out or final approach area, that can be a hazard.

Rule: ATS.TR.250(b)

Before an aircraft taxis for take-off, the tower gives these items in order, unless the pilot already has them:

  1. Runway.

  2. Surface wind and significant variations.

  3. QNH, or QFE on request or by local arrangement.

  4. Visibility for take-off or initial climb, if less than 10 km, or RVR.

  5. The correct time.

Rule: AMC12 ATS.TR.210(a)(3)(a)

Flashcards

Print them: A6 landscape cards (PDF, front and back) · 4 cards per A4 landscape sheet (PDF, cut lines) · Key figures deck (PDF, 35 figures)

Print double-sided, flip on the short edge.

  1. 010-07-02-01What is the main purpose of the tower near the aerodrome?

    To prevent collisions between aircraft, vehicles and obstructions on and near the aerodrome.

  2. 010-07-02-02Where are the conditions for visual separation near aerodromes set out?

    In AMC3 ATS.TR.210(c)(2)(b), which lists the same three conditions as ICAO. The AMC is acceptable means, not hard law.

  3. 010-07-02-03What are the conditions for reduced minima near an aerodrome?

    Any one of three: (a) the controller sees each aircraft and can separate them; (b) the pilots see each other and can keep own separation; (c) a follower sees the leader and can keep separation.

  4. 010-07-02-04Does a VFR flight in a Class D control zone get separation from other VFR traffic?

    No. It gets traffic information about other VFR and IFR traffic, not separation.

  5. 010-07-02-05What happens to the wake minima for a VFR arrival that follows the preceding aircraft?

    They do not apply once the pilot reports the preceding aircraft in sight and the tower says to follow and maintain own separation. The tower then gives a wake turbulence caution.

  6. 010-07-02-06When can the tower use a conditional clearance on the active runway?

    Only when both the controller and the pilot can see the aircraft involved.

  7. 010-07-02-07Which aircraft must pass first when a conditional clearance applies?

    The aircraft or vehicle that causes the condition. It must be the first one to pass in front of the other aircraft.

  8. 010-07-02-08What does the pilot do before acting on a conditional clearance?

    The pilot identifies the aircraft or vehicle that causes the condition.

  9. 010-07-02-09How many elements does a conditional clearance have, and in what order?

    4 elements: call sign, condition, clearance, then a brief reiteration of the condition.

  10. 010-07-02-10Does a taxiing aircraft stop at a runway-holding position?

    Yes, at every runway-holding position, unless it has an explicit clearance to enter or cross the runway.

  11. 010-07-02-11What does a lit stop bar mean for a taxiing pilot?

    Stop and hold. The pilot must not cross a lit stop bar. The pilot continues only when the bar is switched off and the clearance allows it.

  12. 010-07-02-12Which clearances need a read-back on a runway?

    Clearances to enter, land on, take off from, hold short of, cross, taxi and backtrack on a runway, and runway-in-use.

  13. 010-07-02-13What does a taxi clearance normally say when the route passes a runway?

    An explicit clearance to cross that runway, or an instruction to hold short of it.

  14. 010-07-02-14When can the tower give a landing clearance?

    When there is reasonable assurance of runway separation at the threshold. Not before the preceding landing aircraft has crossed the threshold.

  15. 010-07-02-15When does the tower normally let a landing aircraft cross the threshold?

    When the preceding departure has crossed the runway end or started a turn, or when all preceding landing aircraft are clear of the runway.

  16. 010-07-02-16What are the time-based arrival wake minima?

    LIGHT behind HEAVY or MEDIUM: 3 min. LIGHT behind SUPER: 4 min. None for arriving VFR or visual approaches.

  17. 010-07-02-17What is the departure wake minimum for a LIGHT aircraft behind a MEDIUM or HEAVY?

    2 min from the same runway, close parallel runways, or crossing paths. 3 min from an intermediate part of the runway.

  18. 010-07-02-18What are the wake turbulence categories by MCTOM?

    Four categories: SUPER, HEAVY, MEDIUM and LIGHT. LIGHT is 7 000 kg or less. HEAVY is 136 000 kg or more, except SUPER types.

  19. 010-07-02-19When do wake minima apply to approach and departure traffic?

    When one aircraft is directly behind, or crosses behind, another at the same altitude or less than 1 000 ft below. Also when both use the same runway, or parallel runways less than 2 500 ft (760 m) apart.

  20. 010-07-02-20When do reduced runway separation minima (RRSM) apply?

    Only in daylight: from 30 min after local sunrise to 30 min before local sunset.

  21. 010-07-02-21What are the RRSM limits for visibility, ceiling and tailwind?

    Visibility at least 5 km, ceiling not lower than 1 000 ft, tailwind not above 5 kt. Never between a departure and a preceding landing aircraft.

  22. 010-07-02-22What are the RRSM aircraft categories?

    3 categories. Category 1: single-engine propeller, 2 000 kg or less. Category 2: single-engine propeller over 2 000 kg and under 7 000 kg, and twin-engine propeller under 7 000 kg. Category 3: all others.

  23. 010-07-02-23What distance past the threshold does a preceding aircraft need for an RRSM landing?

    At least 600 m behind a preceding Category 1 or 2, for a following Category 1. At least 1 500 m for a following Category 2. At least 2 400 m behind a preceding Category 3, for any following landing aircraft.

  24. 010-07-02-24What distance must a preceding airborne departure pass beyond the succeeding aircraft in RRSM?

    Behind a Category 1 or 2 that is airborne: at least 600 m for a succeeding Category 1, and 1 500 m for a succeeding Category 2. Behind a departing Category 3: 2 400 m for any succeeding aircraft.

  25. 010-07-02-25Below which visibility does the tower report take-off visibility before taxi?

    Below 10 km. Otherwise the tower gives RVR, where applicable.

  26. 010-07-02-26What does the tower give before a pilot taxies for take-off, and in what order?

    Runway; surface wind; QNH or QFE; take-off visibility or RVR if below 10 km; the correct time. Items the pilot already has are not repeated.

  27. 010-07-02-27What does the tower give without delay about other traffic?

    Essential local traffic known to the controller, given to the departing and arriving aircraft concerned.

  28. 010-07-02-28How many designated positions does the tower normally use to give clearances?

    6 positions, from the taxi call to parking information.

  29. 010-07-02-29How many landing priority categories are there?

    4 categories: (a) an aircraft expecting to be compelled to land, (b) hospital or urgent medical aircraft, (c) search and rescue, (d) others as the competent authority decides.

  30. 010-07-02-30What is the upper limit for a clearance to keep own separation in VMC?

    10 000 ft, in Class D or E, during climb or descent, by day, on request and when agreed.

  31. 010-07-02-31Which wake minimum applies after a displaced landing threshold when flight paths are expected to cross?

    2 min for a LIGHT or MEDIUM aircraft against a HEAVY, or a LIGHT aircraft against a MEDIUM.

  32. 010-07-02-32Which wake minimum applies when a heavier aircraft makes a low or missed approach?

    2 min for a lighter aircraft against a HEAVY, when the lighter one departs or lands the opposite way.

Sources

  1. Commission Implementing Regulation (EU) No 923/2012 (SERA) — via EASA Easy Access Rules for Standardised European Rules of the Air (SERA), August 2025, with the related AMC/GM.
  2. Commission Implementing Regulation (EU) 2017/373 (ATM/ANS), Annex I definitions and Annex IV (Part-ATS) — via EASA Easy Access Rules for ATM/ANS – Provision of Services, March 2025, with the related AMC/GM.
  3. ICAO Annex 11, Air Traffic Services, 15th edition (2018), and ICAO Doc 4444, PANS-ATM, 16th edition (2016): used for ICAO comparisons only.
  4. BEA, serious incident to Airbus A320 OE-INE and Robin DR400 F-GTZY, Bordeaux-Mérignac, 31 December 2022, report BEA2023-0004, April 2024: bea.aero.

This page is educational. It does not replace instruction at your ATO or your aircraft's POH/AFM. Rules change: check the regulation in force.

Glossary

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