Simultaneous Operations on Intersecting Runways

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Simultaneous Operations on Intersecting Runways

27TH ANNUAL CONFERENCE, Rio De Janeiro, Brazil, 26-29 April 1988

WP No. 61

Simultaneous Operations on Intersecting Runways


Growing airport capacity problems are being discussed lately in many international aviation organisations. One way to increase airport capacity is to operate simultaneously on intersecting runways. On request of the Australian Guild at the Nairobi Conference, this subject was put on the work program of SC 1 for 1987/88. The intention of this paper is to compare different local procedures on this subject. With ICAO – documents and to study and if necessary develop IFATCA policy.

Simultaneous operations on intersecting runways consists of 3 kinds of conflicting situations:

a. departure and departure

b. departure and landing

c. landing and landing

ICAO documents only cover separation criteria to be used during simultaneous operations on crossing runways, situations A and B. (Doc. 4444, IV 14, V 15)

In these situations (A and B) normal separation criteria can be used by ATC, and the only conflicting situation point, the crossing position of the intersecting runways, can be controlled by timing the departure. Also wake turbulence conditions restrict these situations.

During simultaneous landing/landing operations on intersecting runways there are two critical points, the crossing point of the relevant intersecting runways and the “go around” crossing points. As there are no specific ICAO criteria or guideline for these kind of operations, some local authorities are introducing their own local procedures and instructions (which may differ from airport to airport). In other cases there are no procedures or instructions at all on this subject, and then it is the judgement of the controller.

One way to separate in these situations is to “stagger” the approaches to the two intersecting runways. Radar separation exists between aircraft A in the final approach, and aircraft B at the moment of passing the crossing point of the intersecting runways . The increase in landing capacity is mostly in these situations not great.

The other way is that the aerodrome controller applies visual separation, this is reduced radar or procedural separation. According Doc. 4444 IV 1, reduction in separation minima is allowed in the vicinity of an aerodrome if: “ a. Adequate separation can be provided by the aerodrome controller when each aircraft is continuously visible to this controller; or b. Each aircraft is continuously visible to the pilots in command of the other aircraft concerned and the pilots thereof report that they can maintain their own separation,….” In these situations the workload of the controller and the frequency congestion will increase. The increase in landing capacity is greater than the situation above in 2.5.

Because the moment, in which collision hazards occur, is the most critical phase of the flights concerned, only visual monitoring by the aerodrome controller alone is not sufficient. In this situation it is essential that each aircraft is continuously visible to the pilots concerned and that both pilots have the conflicting runways in sight.

Is, in this situation adequate separation provided by the aerodrome controller, when he is only giving essential traffic information and monitoring the situation? Or is the responsibility of avoiding collisions, left to much to the pilots? No statistic studies are available that describe collision risk models for this kind of operations.

In order to minimise the risk of collisions, it is necessary to define general conditions, under which these kind of operations can be carried out, if aerodrome lay-out and performances of new generation aircraft allow an acceptable level of safety.

Factors to be taken into account when developing general conditions and procedures for simultaneous operations on intersecting runways should include:

  1. weather conditions , to allow visual monitoring by the aerodrome controller and the pilots concerned;
  2. Available runway length in relation to the aircraft’s performance, if only a part of a runway is available, procedures must read clearly for which types of aircraft an approach to this (shorter) runway is available;
  3. Temporary runway conditions and other runway characteristics which may influence stop distances;
  4. Visual markings that indicate displaced runway end in these procedures should be available;
  5. Jet blast and wake turbulence situations can restrict these operations;
  6. Essential traffic information, to be given by ATC;
  7. Controllers workload and frequency congestion are essential factors.

To Conclude

On more and more aerodromes simultaneous landing operations on intersecting (crossing) runways are being carried out, in order to solve airport capacity problems.

One of the main objectives of ATC is to prevent collisions between aircraft. It is an unsatisfactory situation when some of the responsibility of ATC is put onto the pilots by giving only essential traffic in possible hazard situations.

The establishment of procedures for these kind of operations is essential to :

  1. minimise workload of ATC;
  2. minimise frequency congestion;
  3. provide ‘adequate’ separation instead of traffic information.

Separation criteria for simultaneous landing operation on intersecting runways could be based on better characteristics, performances and advanced navigational equipment of aircraft together with better use of airfield lay-out, and those separation criteria should be controlled with better surveillance equipment(i.e. terminal radar’s with quicker returns).

It is recommended that:

Where procedures are developed to allow simultaneous operations on intersecting runways, these procedures must take into account of ATC workload; the number and effects of any procedural restrictions and the possible need for improved radar systems.

Last Update: September 20, 2020  

December 2, 2019   135   Jean-Francois Lepage    1988    

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