A stand guidance system is a system which gives information to a pilot attempting to park his aircraft at an airport stand, usually via visual methods, leading to the term Visual Docking Guidance System (VDGS) and also A-VDGS (the A standing for advanced) This allows them to remain clear of obstructions and ensures that jetways can reach the aircraft.
AGNIS VDGS
Azimuth Guidance for Nose-In Stand is one of the most popular forms of stand guidance. It consists of two coloured lights mounted side by side.
If the pilot is on the stand centreline they will see two green lights. If they are off centreline, one of the lights will appear red and the pilot then steers towards the green one. AGNIS alone provides only azimuth guidance, it does not inform pilots when they should stop. It is relatively imprecise but cheap to implement and reliable.
PAPA
The Parallax Aircraft Parking Aid is frequently combined with an AGNIS system, informing flight crews when to stop. The device features no electronics or moving parts; it consists simply of a large grey box (usually with one or more sides missing) with a large rectangular slot cut in to the front.
Inside the box, towards the rear, is a white stick or fluorescent tube, which appears to move from one side of the slot to the other as the viewer moves closer, although it is in fact fixed and the effect is merely due to perspective (see parallax) [1]. Above and/or below this slot will be markings in white or yellow, indicating where different types of plane should stop.
As this system relies on the position of the viewer, it will not give accurate distance information to aircraft which have deviated significantly from the stand centreline.
Stop light
This is a simple two phase traffic light with red and green lights, mounted to the side of the AGNIS lights. Typically these are round and mounted vertically, in order to avoid confusion to AGNIS lights which are also red and green but mounted side by side and usually square.
Mirror
Used in combination with AGNIS at stands which can only accept smaller airliners, it features one or two mirrors, allowing the flightcrew to see ground markings in relation to their nose wheel, when it is within the area they need to stop. Typically two mirrors are used, angled differently to suit the various heights of cockpits from the ground.
A-VDGS
Advanced Visual Docking Guidance Systems feature electronic displays which perform the functions of an AGNIS/PAPA installation, although with much greater accuracy. They may also provide collision avoidance from static objects.
A-VDGS systems will usually have emergency stop buttons located both on the stand and in the jetway/gate area, which causes the stop indication to appear immediately.
Safegate
Safegate is the most popular stand guidance systems after AGNIS and is seen at major airports throughout the world, making it the most popular A-VDGS.
The green lights on the left and right of the display will begin to appear, from bottom to top, as the aircraft gets closer to the stop line. The green centreline on the display moves smoothly left and right to accurately indicate how away from the centreline an aircraft is.
APIS
APIS display for an A340-300, which is to the left of the centreline and far away from the stop point
The Aircraft Positioning and Information System, from FMT [2],shows azimuth information on the left side of its display, using a series of parallel and black bars which kink at their midpoint. The bars will appear straight when the aircraft is on the centreline, and the angle of the kink will become more acute the further afield an aircraft strays from the centreline. It is important to note the azimuth guidance is only accurate when viewed from the left seat.
Distance information is given by a bar on the right side of the display, which “disappears” from bottom to top as the aircraft gets closer to the stop point. Across the top of the display, text will initially display the aircraft type the system has identified, and will display “STOP” when aircraft reaches the stop point. It can also display “T.FAR” and some other messages such as “O.BLK” or “OK”.
Safedock
An example of a Safedock S model display. The aircraft parking is an B757 which is left of the centreline. The vertical yellow bar in the centre disappears, from bottom to top, as the aircraft approaches the stopping point.
Safedock by Safegate, allows aircraft to park up to an accuracy of 10 cm using invisible infrared lasers to attain the aircraft’s position and type for easier docking[3],[4]. It comes in a variety of models; the T1 [5], the T2 [6] and the T3 [7]. Red and yellow arrows indicate in which direction the pilot needs to manoeuvre to be on the centreline. Each model has an S variant (e.g. T1S), which also indicates the position of the aircraft relative to the centreline. In either variant, a central yellow column disappears from bottom to top as the aircraft approaches the stop point.
