I am a frequent spotter at MSP and I often time my visits to catch our once-daily NW 744 flight leaving for NRT .
There's just one problem: It's often hard to guess in advance whether that flight will use MSP 's 10,000 foot Rwy 12R/30L or its 11,000 foot Rwy 4/22.
Some days (like today) it's not hard to figure it out: We had winds 220 at 19 gusting to 26 - so it was a departure on Rwy 22. (Although regular traffic was landing and taking off on 30L and 30R in spite of the 90 degree crosswind and +/- 10 knot windshear on approach - which made for an especially fun afternoon of spotting as the landing aircraft crabbed their way in).
On days where the runway choice is not as clear cut as today, I have to listen in on the ground frequency and wait until I hear that flight get its instructions on where to taxi to. That doesn't leave me enough time to reposition myself in the best place to watch the takeoff if I've guessed wrong.
So, what I'm hoping for is some help on a formula I could use to make the most educated guess possible about which runway this flight will take off on.
On any given day, the variables that I WILL know are wind direction and velocity, aircraft type (747-400) and the runway lengths of the two possible runways (4/22 11,000 feet, 12R/30L 10,000 feet). What I WON'T know is: takeoff weight - I'm guessing this varies somewhat from day to day based on many factors - and other intangibles like what that particular captain prefers to do given the conditions.
Can anyone help me out?
P.S. This is my first post on a.net. I've been visiting the site for a long time, but I finally joined up today!