Runway separation

Runway separation

Runway management is the main task of every tower controller. Without a runway, an airport obviously makes no sense. Not only do we have to use our runway as efficiently as possible in order to fully utilize the airport's capacity, but we also have to protect it accordingly, as the critical flight phases of take-off and landing take place there. Runway separation was introduced for this purpose. But what actually is runway separation? It's actually quite simple:

The runway may only ever be occupied by one user at a time.

Now we just have to deal with a few more questions to clearly define the concept.

Who is considered a runway user?

How long is a user considered to be an active user of a runway and when is the runway free again for the next user?

ATD_Pistenstaffelung.png


An aircraft that is cleared for line-up (i.e. taxiing onto the runway, but without take-off clearance) does not count as a runway user. A line-up clearance can therefore be given in the following cases, even though the runway is still occupied according to the above criteria:

The procedure described on this page is also called “full” runway separation. Does this mean that there is a “half” runway separation, too? Not quite, but almost. There is also “reduced” runway separation (RRS), which is taught in the specific tower textbooks. A brief teaser: with reduced runway separation, under certain conditions the runway may be used more efficiently.


Intersecting runways

Many airports have intersecting runways either to compensate for prevailing weather conditions or to increase efficiency due to a lack of space. In Germany, Hamburg and Cologne are particularly well known for their intersecting runways.

As always, there are rules and regulations that must be observed when using the two runways simultaneously.

In this chapter, we will consider all possible combinations for using the runways.

Departure - Departure

In the case of two departures on intersecting runways, the second aircraft may only begin the take-off run if one of the following conditions is met:

The other aircraft is taking off and

Intersecting Runways 1.pngArrival - Departure

The situation is different if we have a preceding inbound, in which case the second aircraft on the intersecting runway may only begin the take-off run if one of the following conditions is met:

The other aircraft lands and

Intersecting Runways 2.png

Abflug - Anflug

Bei einem abfliegenden Luftfahrzeug gefolgt von einem anfliegenden Luftfahrzeug auf der kreuzenden Piste, darf das folgende Luftfahrzeug den Anfang der Piste erst überfliegen, wenn eine der folgenden Bedingungen gegeben ist::

Das andere Luftfahrzeug startet und

Intersecting Runways 4.png

Arrival - Arrival

The last possibility is a landing aircraft followed by another landing aircraft on the intersecting runway. The following aircraft may only fly over the runway threshold if one of the following conditions is met:

The other aircraft is landing and

Intersecting Runways 3.png

Simultaneous use of intersecting runways

The simultaneous use of intersecting runways may only be authorized for two landing aircraft under the following conditions:

Intersecting Runways 5.png

All of the following conditions must additionally be met:

Reduced runway separation (RRS)

Reduced runway separation is not a mandatory part of S1 training.

Requirements

ATCOs can only use Reduced Runway Separation if the following aspects are fulfilled:

Aircraft categories

For the Reduced Runway Separation procedure, aircraft have been divided into three categories.

These three categories are:

CAT 1 CAT 2 CAT 3
Single-engine propeller-driven aircraft with a maximum take-off weight of up to 2 tons.

Single-engine propeller-driven aircraft with a maximum take-off weight greater than 2 tons but less than 7 tons.

Twin-engine propeller-driven aircraft with a maximum take-off weight of less than 7 tons.

All other aircraft
ATD_RRS_LFZ_KAT1.png ATD_RRS_LFZ_KAT2.png ATD_RRS_LFZ_KAT3.png

The following registrations apply in Germany:

  • D-E

  • D-K

  • D-M

The following registrations apply in Germany:

  • D-(up to 7 tons)
  • D-F
  • D-G
  • D-I

The following registrations apply in Germany:

  • D-(over 7 tons)
  • D-B
  • D-A

Examples: C152, C172, P28A, A210, DA40, DR40, DV20, SR22

Examples: DA62, PA34, TBM9, BE58, B350

Examples: AT75, DH8D, C25C, CRJ9, B738, A359

Possible constellations

There are four different possible constellations of these categories on a runway. We will now look at these step by step with a focus on Reduced Runway Separation.

Departure behind departure

Preceeding
Suceeding
Requirement
CAT 1 / CAT 2
CAT 1
airborne and at a distance of 600m
CAT 1 / CAT 2
CAT 2
airborne and at a distance of 1500m
CAT 3
all
airborne and at a distance of 2400m
Arrival behind arrival
Preceeding
Suceeding
Clearance before
Requirement
CAT 1 / CAT 2
CAT 1
aircraft crosses runway threshold
vacating runway and at least 600m from threshold
CAT 1 / CAT 2
CAT 2
vacating runway and at least 150m from threshold
CAT 3
all
vacating runway and at least 240m from threshold

This situation may seem somewhat strange, as a landing clearance is issued even though there is another pilot still on the runway. However, if the distances are maintained, this is actually legal and is practiced in reality.

Arrival behind departure
Preceeding
Suceeding
Clearance before
Requirement
CAT 1 / CAT 2
CAT 1

aircraft crosses runway threshold


airborne and at least 600m from threshold
CAT 1 / CAT 2
CAT 2
airborne and at least 1500m from threshold
CAT 3
all
airborne and at least 2400m from threshold
Departure behind arrival

Reduced runway separation may not be used in this constellation.

Phraseology examples

German English
G: VERKEHR C172 FLIEGT *VON PISTE 25* AB G: TRAFFIC C172 DEPARTING *ON RUNWAY 25*
G: VERKEHR A320 IST *AUF PISTE 25* GELANDET G: TRAFFIC A320 LANDED *ON RUNWAY 25*
G: VERKEHR PA34 LANDET *AUF PISTE 25* G: TRAFFIC PA34 LANDING *ON RUNWAY 25*

Miscellaneous and example

Example of the procedure
We issue a take-off clearance, the next approach is on a 3NM final. In this situation full runway separation is not so likely, so we give traffic information to the landing traffic about the departing traffic. As soon as this is done and the meteorological conditions are suitable, we can apply RRS. The traffic info can read: “DLH414, TRAFFIC A320 DEPARTING RUNWAY 26R”. Theoretically, the traffic information can also be given when the aircraft is cleared to land. However, as RRS is quite tight, it is advisable to give the traffic information as early as possible so you only have the landing clearance left to give and can keep it brief and concise later. As soon as the departing traffic has taken off and passed the prescribed distance from the runway threshold, the landing clearance can be given: “DLH414 WIND 170 DEGREES 6 KNOTS RUNWAY 26R CLEARED TO LAND”.
Marker in the sector file
Of course, you do not have to estimate the distances in meters. Depending on the runway direction selected in Euroscope, you will find green markers on the runway (design may vary depending on the FIR). These describe the distances for the various combinations of aircraft CATs from the start of the runway. The first marker is at 600m and the following ones at 1500m and 2400m. The picture shows an example of these markings for runway 08L in Munich. The representation may differ depending on the FIR.

ATD_RRS Marker.png
Article about Reduced Runway Separation

Anyone interested in the topic of RRS beyond the content mentioned above will find an interesting article on the subject in an issue of “Flugleiter”, the magazine of the air traffic controllers’ union. It can be found from page 48 onwards.
Flugleiter 04/22