How does a VDGS show the stopping position and distance?
The second half of docking guidance. The display shows where this aircraft must stop, how far there is still to go, and when it has arrived.
The stopping position indicator answers the second docking question: how far is there still to go? It shows the pilot where the aircraft must stop, how quickly it is closing, and when it has arrived. Azimuth guidance, in the previous entry, handles the lateral half.
1The stop point depends on the aircraft
The indicator shows the stopping position for the aircraft it is guiding. Aircraft differ in length and in where the nose gear and doors sit, and the stop point has to put the doors where the boarding bridge and ground equipment can reach them. The information also has to allow for the range of eye heights and viewing angles expected, so it reads correctly from different cockpits.
2Distance and closing rate
The system measures the remaining distance and shows it as a bar or number that shortens as the aircraft closes. Annex 14 asks for closing-rate information so the pilot can slow gradually and stop at the intended point, over a distance of at least 10 m. The pilot should see the stop coming, not meet it suddenly.
3Green to proceed, red to stop
Where colour change is used, green shows that the aircraft can proceed and red shows that the stop point has been reached. A third colour may be used for a short distance before the stop point to warn that it is close.
4What goes wrong
The wrong aircraft type selected gives the wrong stop point, so the aircraft stops short or long. Closing-rate information that is too short or too late forces hard braking. A dirty or blocked sensor, glare, or a display that cannot be read together with the azimuth unit leaves the pilot guessing in the last few metres.
| Item | Principle | Why |
|---|---|---|
| What it shows | Stop point, distance to go, closing rate | Gradual, planned deceleration |
| Closing rate | Shown over at least 10 m before the stop point | Time to brake smoothly |
| Colour, where used | Green proceed; red stop point reached; optional third colour just before | Read at a glance |
| Stop point | Set for the aircraft type, allowing for eye height and viewing angle | Doors meet the bridge |
| Location | With or close to the azimuth unit | Both read without turning the head |
| Aircraft type | Shown to pilot and supervisor where selected for the stand | A wrong selection is caught early |
Frequently Asked Questions
Q1What is the stopping position indicator?
It is the second half of a visual docking guidance system. Where azimuth guidance tells the pilot whether the aircraft is on the stand centreline, the stopping position indicator shows where the aircraft must stop, how far it still has to go, and when it has arrived.
Q2How does the pilot know how far there is to go?
The display shows the remaining distance to the stop point, usually as a bar or number that shortens as the aircraft closes. ICAO Annex 14 asks for closing-rate information so the pilot can slow gradually and stop at the intended point, over a distance of at least 10 m before it.
Q3Why is the stop point different for each aircraft type?
Aircraft differ in length and in where the nose gear and doors sit, and pilots sit at different eye heights. The stop point has to put the doors where the boarding bridge and ground equipment can reach them, and the display has to read correctly for the range of eye heights and viewing angles expected.
Q4What does the third colour mean?
Annex 14 says that where colour change is used, green shows the aircraft can proceed and red shows the stop point has been reached. A third colour may be used for a short distance before the stop point to warn that it is close. The exact colour and distance depend on the system, so take them from the manufacturer's data.
Q5Why should the azimuth and stopping displays be close together?
So the pilot can read both at once without turning the head. The stopping position indicator is located in conjunction with, or close to, the azimuth guidance unit, because the pilot is steering and slowing at the same time.
Q6What happens if the wrong aircraft type is selected?
The stop point shown is wrong for that aircraft, so it can stop short or long. Where the system has to be set for a type, Annex 14 asks that the selected type is shown to both the pilot and the person supervising, so a wrong selection can be caught before the aircraft arrives.
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