Fabo From Slovakia, joined Aug 2005, 1111 posts, RR: 1 Reply 1, posted (6 months 2 weeks 3 days 17 hours ago) and read 1989 times:
As long as it know the relative positions of nose, engines and relative reference spot for parking (be it nose itself, nose gear, doors...), the rest is simple trigonometry and FWIW you could measure the distance of tail....
Regarding measuring method, I know some types use laser equipment, but that can be different model to model.
The light at the end of tunnel turn out to be a lighted sing saying NO EXIT
strfyr51 From United States of America, joined Apr 2012, 488 posts, RR: 0 Reply 2, posted (6 months 1 week 3 days 22 hours ago) and read 1663 times:
Most accupark systems are guided from sensors embedded in the ground or a light system that aligns when properly parked. United had an ingenious system where 2 lights were aligned on the terminal to give nose alignment and 2 were on the speedway to the left for distance. when both were a single light the pilot stopped it never failed. the sensor system worked if the pilot looked at it and was careful. I saw accidents where the crews did not use good judgement upon arrival.
I remember a European 747 crew arriving at SFO went to the wrong gate and taxied into the jetway after claiming that the sun was blotting out the accupark lights. The Lights were NEVER ON! So it only works if you're where you're supposed to be and careful about it. These guys hit the jetway with #2 engine before they stopped. The fur flew for 2 weeks after that when they claimed we gave them bad gate information. But the gate they tried to park at wasn't USED for a 747. It was set up the Aeroflot's IL62 that couldn't use accupark. American and Pan AM had a parking system years ago that used rails. where the pilot nosed the airplane in until the rail touched the window. I thought that was pretty good too even if low tech. Many of the newer systems do not require a ramper or mechanic to be present except to chock the nose. I still favor the hand held Dead man switch because it requires a second set of eyes on the ground.
Pihero From France, joined Jan 2005, 3598 posts, RR: 72 Reply 3, posted (6 months 1 week 3 days 11 hours ago) and read 1580 times:
As a matter of fact we have gone very far from simple practical trig devices into Fresnel /moiré optics cum laser beams distance measuring down to one centimetre accuracy.
One has to remember that an aircraft is to be poisitioned precisely in a gate position so it can have a safety perimeter and be placed at the best position for the boarding door relative to the moving gate.
On this subject, Wiki takes a good part of a CAA paper, with more info and less technical explanations on the most common devices this side of the Atlantic... basically the most popular outside the US : Visual Docking guidance Systems