Propellor
7th Feb 2002, 17:49
There is a certain error induced if the VASI or the PAPI is followed all the way to touchdown.. .Visual guidance systems like the PAPI are designed for a certain fuselage length and unlike the old VASI, there is no different view for a long body type.. .Even on the most pefect approach, say an Autoland, there is a stage when the PAPI turns 'All Red' on a smaller aircraft, and almost 'All White' on a very long airplane.. .Can somebody throw light on the subject, especially on the height at which they cease to be reliable, and where is the information to be found?
Long Range Cruise
7th Feb 2002, 18:47
I am unable to inform you of 'where' to find the information, but can 'suggest' you look on the CAA, or maybe BAA website. Must be something there.
In the 340, i use the PAPI/VASI guidance facility until i beocme comfortable with landing the aircraft by judgement. There is no set procedure, so to speak, as to how to follow the lights, except the obvious color changes.
On runway 23 at LHR(EGLL), i used the lights until about 250 feet or so, and when the landing is confirmed (no go-around), i continue with altimeter glances. . .When flying specific procedures, for example landing, it is best to and pretty much SOP, to have one set of eyes out the plane, and one set in. If preferred, lighting guidance systems when being used in larger aircrafts can still be used all the way to touchdown, but only if the light colors are accepted to be incorrect by the pilot, just different because of the size of the aircraft.
Hope this gives you a broader idea.