Wake turbulence separation

Leader and follower both matter

Wake separation is not determined by the following aircraft alone.

ICAO categories

Under the traditional ICAO scheme, SUPER applies to designated aircraft types, HEAVY to types of 136,000 kg or more excluding designated SUPER, MEDIUM to types above 7,000 kg and below 136,000 kg, and LIGHT to types of 7,000 kg or less. Use maximum certificated take-off mass rather than today’s actual landing mass. HEAVY or SUPER is included after the call sign on initial radiotelephony contact as required.

Wake strength, persistence and encounter risk depend on aircraft and conditions. RECAT-EU and other locally authorised schemes can use different groupings and pairwise minima. They do not universally replace the traditional ICAO matrix at every aerodrome. Read the AIP and the regime stated in an examination question.

Traditional surveillance distance examples

For the traditional distance scheme, a HEAVY behind HEAVY uses 4 NM, MEDIUM behind HEAVY 5 NM, LIGHT behind HEAVY 6 NM and LIGHT behind MEDIUM 5 NM when the wake application conditions are met. Behind SUPER, the traditional values are HEAVY 6 NM, MEDIUM 7 NM and LIGHT 8 NM. Other pairs still need the applicable ordinary surveillance separation.

These minima apply under specified same-path, crossing/vertical and runway situations. A table cell is not a permission to use that value under every geometry. The model explicitly labels the selected traditional regime and distinguishes it from the local RECAT option, whose actual published values must be consulted.

Time minima at the runway

A short intersection departure changes the wake problem.

Arriving and departing time minima

For traditional non-surveillance arrivals, MEDIUM behind SUPER needs 3 minutes, LIGHT behind SUPER 4 minutes, MEDIUM behind HEAVY 2 minutes and LIGHT behind HEAVY or MEDIUM 3 minutes. The specified exceptions, including some visual approaches with accepted own separation, must be read with the rule.

For full-length departures in the specified same/close-parallel or crossing-path cases, LIGHT/MEDIUM behind HEAVY and LIGHT behind MEDIUM ordinarily need 2 minutes; HEAVY behind SUPER 2 minutes and LIGHT/MEDIUM behind SUPER 3. For an intermediate departure point, LIGHT/MEDIUM behind HEAVY, or LIGHT behind MEDIUM, ordinarily need 3 minutes; behind SUPER, the intermediate-point value for LIGHT/MEDIUM is 4 minutes. Displaced-threshold and opposite-direction situations have dedicated provisions.

The pilot still assesses exposure

An ATC wake warning or an accepted visual own-separation arrangement does not make the wake disappear. Consider the preceding flight path, touchdown/rotation point and wind drift. Avoid relying on a tailwind or an apparent lateral offset as a guarantee that the wake is harmless.

If unable to accept the proposed interval, state unable and request additional spacing or a different departure arrangement. The time model shows why changing an intersection can place the following aircraft behind the leader’s airborne wake even when the runway is physically clear.

Displaced thresholds and opposite-direction movements

Where a displaced-threshold arrival/departure combination produces crossing paths, the traditional time minimum is three minutes for LIGHT/MEDIUM behind SUPER, or two minutes for LIGHT/MEDIUM behind HEAVY and LIGHT behind MEDIUM in the specified situations. The opposite-direction and missed-approach cases also have specific minima and geometry conditions; identify the leading/following category, direction and path intersection before selecting a value.

Can you apply the rules?

Four original questions. Choose from the facts, then review the explanation.