A Surface Movement Guidance and Control System (SMGCS) consists of the provision of guidance to and control or regulation of all aircraft, ground vehicles and personnel on the movement area of an aerodrome. An SMGCS is comprised of visual aids, equipment, procedures, control, regulation, management and information facilities. In 1986 the latest manual for SMGCS was published by ICAO. IFATCA was represented on the panel working group that developed the new manual. The SMGCS working group is continuing to study certain items which have not yet been included in the SMGCS manual, other ICAO documents or Annexes. The 1986 Conference tasked SC 1 with the study of four particular areas and, if considered necessary, to develop IFATCA policy on the relevant issues.

The four items that SC 1 was asked to study are :

1. Separation criteria/standards for ground movement;
2. The use of Surface Movement radar;
3. Transfer of responsibility for separation;
4. Control of Apron/Manoeuvring Area.

Separation Criteria / Standards on the Manoeuvring Area

The control of traffic at taxiway intersections in low visibility conditions demands main taxi routes with standardised visual markings and lights. Traffic should not enter or cross such routes without clearance. (Lateral separation). Decisions as to overall taxiway routeings lies with ATC. Responsibility for complying with that route lies with the pilot. (i.e. using the taxiway centreline, following standard route).

ATC should be responsible for the sequencing of traffic on the ground.

As the visibility reduces ATC will provide increasing information to assist pilots to maintain their own separation (longitudinal spacing, lateral separation). When predetermined conditions occur the availability of visual separation is withdrawn from the controller. This predetermined point may vary from airfield to airfield and must be clearly notified by ATC to the pilot. Special procedures will become active. In high traffic density operations during low visibility conditions the ability to maintain the traffic flow will require technical solutions to the problems of separation (e.g. Flightdeck interpreted equipment such as under-surface guidance systems or image intensifiers.) The role of SMR as a monitoring device is self evident. The use of a new generation of SMR as a control device is still at an evolutionary stage. The operational requirements and the technical specifications for this equipment are being developed. Separation criteria to be used with these radar’s are still under study.

Annex 11 Chap. 2 states that, under certain conditions, ATC is responsible for the separation of aircraft and of aircraft and vehicles on the manoeuvring area, but no criteria are given. The ‘appropriate ATS Authority’ is tasked with developing ground separation standards for aircraft and vehicles.

Present SMR has limitations and is only a monitoring device for the controller, it is certainly not a positive control facility. When ATC loses visual contact with the manoeuvring area and the traffic on it, SMR does not give the same instant and comprehensive information.

Together with visual aids ATC can prevent collisions and ensure smooth and efficient traffic flow during low visibility conditions. (Down to 400m.) , but controllers and pilots should be aware of thelimitationsofSMR.Whenthevisibilityfallsbelow400m.themonitoringroleofSMRbecomes more important as the ability of the pilot to observe other aircraft, vehicles and obstructions is impaired.

The operational requirements for SMR should be :

1. to provide information that will assist in preventing collisions;
2. to provide information that enables ATC to monitor aircraft and vehicle movements and to ensure that they are complying with the instructions issued;
3. to make full use of SMR capabilities, continuous aircraft identification should be available;
4. to provide information to assist ATC in the choice of runway exits, in order to reduce runway occupancy times;
5. to protect ILS critical and sensitive areas;
6. to protect against unauthorised runway penetration;
7. to observe unauthorised aircraft and vehicle movements on the manoeuvring area;
8. to provide assistance to the emergency services.

The marking and lighting of the manoeuvring area should be at such a level that pilots can comply with the routing instructions issued by ATC during low visibility operations. It is not possible to give precise navigational guidance with SMR due to the very low tolerances for obstacle clearance on taxiways and aprons.

It is impossible to separate aircraft longitudinally with only SMR as ATC is not able to precisely control aircraft speed.

Control on Apron and Manoeuvring Area

It is still difficult in many cases for pilots to find out what kind of service they are receiving (ATC or Apron Management Service) when working a certain frequency or moving on a certain part of the movement area.

Visual markings and lights can help the pilot identify the boundary of the apron and the manoeuvring area, but standardisation is required.

To Conclude

Every airfield should have a Surface Movement Guidance and Control System to enable a safe and expeditious flow of traffic on the ground.

Transfer of responsibility for separation from the pilot to ATC should take place at a clearly defined point, notified to all parties. To define this point many factors and local conditions must be examined.

The appropriate ATC authority should institute an SMGCS which includes procedures for avoidance of collision between aircraft, and between aircraft and vehicles on the ground.

ICAO should not specify the separation standards necessary to achieve the above objective.

Surface movement radar should be used as a monitoring device and should not be used for the provision of a control service unless procedures are available.

The boundary between apron and manoeuvring area should be clearly defined.