Surface Movement Guidance Control System
The SMGCS is a type of control system which is designed to enable safe movement of aircraft and other vehicles on the taxiway infrastructure, the use of advanced visual aids and by establishing rigorous control procedures.
Standard operating procedures are adopted by Aircraft operators which include operational guidelines conforming to standard SMGCS movement criteria. There are currently two levels of SMGCS – from 1,200- 500ft RVR, and <500ft RVR. The <500ft level is obviously stricter, with more airport equipage and recurrent maintenance cost needs.
The key elements of SMGCS are the enhanced visual aids which include taxiway centreline lighting, markings, and signage, stop bar lighting, runway guard lights, along with the provision of visual cues for vehicle operators. When installed, these visual aids establish a mechanism in which monitoring, routing, guidance, and control or surface manoeuvres in low visibility conditions may be achievable. An indicative list of the requirements of SMGCS enhanced lighting is summarised, but other lighting systems may also be considered.
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Stop bar lights
For operations less than 600 feet RVR, it is a necessity for stop bars to be installed at intersections where the taxiway centreline is illuminated, as well as a lighted taxiway and an active runway intersection. These types of inset fixtures (in-pavement lights) are red in colour, generally unidirectional and installed along the holding position markings. Clearance for a pilot or other ground vehicle to proceed is visually achieved when the stop bar is extinguished by the controller. Stop bars located at runway intersections are interlocked with green centreline lead-on lights, which extend from the stop bar location onto the runway.
Normal operation of stop bars include:
- Clearance by air traffic control to a pilot or ground vehicle operator to enter the runway. The deselection of the lights causes the red stop bar to be extinguished and the green lead-on lights to illuminate.
- After a predetermined time or after traveling approximately 100 meters beyond the stop bar, the aircraft or vehicle activates a runway incursion sensor. This sensor automatically relights the stop bar and extinguishes the first segment of the lead-on lights between the stop bar and the sensor. These actions provide added protection for the runway against any inadvertent entry by a trailing aircraft or vehicle.
- The aircraft then activates a further sensor at approximately 120 meters which extinguishes the remaining lead-on lights.
- If for some reason either runway incursion sensor is not activated within a specified time limit, the stop bar will default automatically to “on” and both sections of lead-on lights will be turned “off.”
Runway Guard Lights
Runway guard lights are installed at all taxiways which provide access to the runway in use. These lights consist of alternately flashing yellow lights and can either be elevated of inset fixtures. The guard lights identify the presence of an active runway and indicate the location of a runway holding position marking.
Taxiway centreline lighting
For the guidance of aircraft and vehicles around the taxiway infrastructure under low visibility conditions taxiway centre line lighting is used. These consist of inset fixtures, that emit green light and are usually bidirectional. Taxiway Centreline. When the taxiway system passes through the ILS protected area the lights are alternate green yellow.
Clearance Bar Lights
To denote holding positions for aircraft and ground vehicles, three yellow in-pavement clearance bar lights are installed.
Airfield guidance signs have two purposes.
- Mandatory Signs – These give the pilot instructions that they must obey at all times. Before proceeding past this type of sign, they must receive permission from air traffic control.
- Information Signs – These give the pilots direction to a certain location by the use of arrows and taxiway names. It also provides a clear indication as to the precise location where an aircraft or vehicle is located and the names of the taxiway which it is travelling.