Posted: Sun Feb 10, 2008 1:10 pmAfter reading some comments in another post to this effect recently, I decided to sit down and try to figure out why FS just won't allow the use of Runways 11/29 at Christchurch. It appears FS has a formula for working out which runway should be designated as active, based on the wind direction (possibly derived from crosswind/tailwind components for each runway) and the ratio of length of longest to length of next longest runway.
At Christchurch, I set the wind to 110 degrees at 8 knots. Needless to say, it gave me runway 02/20. This is the behaviour we all hate and are trying to quash. So I increased the wind up and up and up. Still had RWY 02/20 at around 60 knots of crosswind. Then I tried playing with the AFCAD and lengthened RWY11/29 so it was longer than 02/20. Set wind to 110@8 and the runway in use became runway 11! It seems that as you shorten runway 11/29, the amount of wind necessary for it to be advertised as the duty runway increases considerably, since it's always compared to 02/20 at nearly 3300m.
I guess the behaviour they are TRYING to model is that "A shorter runway is always less desirable than a longer runway. Strong crosswinds render a longer runway unsafe, so under those circumstances, it's safer to land into a head wind on a shorter runway than land with a strong crosswind on a long runway." What's silly is the threshold. With runway 11/29 extended out to 2050m, the wind speed necessary for it to become the duty runway was 110@40. And to think there are airports like Gisborne with just over 1300m of runway that will happily become the duty runway with 1 knot of wind since there is nothing else longer. It seems a little silly really.
It also makes sense why New Plymouth is always so keen to dish out the grass vectors, since it's 1200m which is only 110m shorter than the seal runway. In this case, the wind would only have to favour the grass slightly in order to be classed as 'safer' than the seal. Remember, FS cares nothing about surfaces. A runway is a runway in it's opinion.
Anyway.... Can anyone think of any creative way we could exploit this and get our beloved Runway 11/29 to work at Christchurch?
At Christchurch, I set the wind to 110 degrees at 8 knots. Needless to say, it gave me runway 02/20. This is the behaviour we all hate and are trying to quash. So I increased the wind up and up and up. Still had RWY 02/20 at around 60 knots of crosswind. Then I tried playing with the AFCAD and lengthened RWY11/29 so it was longer than 02/20. Set wind to 110@8 and the runway in use became runway 11! It seems that as you shorten runway 11/29, the amount of wind necessary for it to be advertised as the duty runway increases considerably, since it's always compared to 02/20 at nearly 3300m.
I guess the behaviour they are TRYING to model is that "A shorter runway is always less desirable than a longer runway. Strong crosswinds render a longer runway unsafe, so under those circumstances, it's safer to land into a head wind on a shorter runway than land with a strong crosswind on a long runway." What's silly is the threshold. With runway 11/29 extended out to 2050m, the wind speed necessary for it to become the duty runway was 110@40. And to think there are airports like Gisborne with just over 1300m of runway that will happily become the duty runway with 1 knot of wind since there is nothing else longer. It seems a little silly really.
It also makes sense why New Plymouth is always so keen to dish out the grass vectors, since it's 1200m which is only 110m shorter than the seal runway. In this case, the wind would only have to favour the grass slightly in order to be classed as 'safer' than the seal. Remember, FS cares nothing about surfaces. A runway is a runway in it's opinion.
Anyway.... Can anyone think of any creative way we could exploit this and get our beloved Runway 11/29 to work at Christchurch?
