PhilB From Ireland, joined May 1999, 2915 posts, RR: 14 Reply 5, posted (12 years 5 days 18 hours ago) and read 1850 times:
Except, of course the average day, in reality, rarely exists and other factors come into play.
Start with the weight, then the temperature, the pressure, any runway slope, wind speed and direction, altitude of the runway and any variables the airline ops manual may throw in for the particular runway.
Nowadays the computer does it all, back in the 1970s it was a set of graphs and a circular slide rule....happy days.
B744 From New Zealand, joined Dec 1999, 491 posts, RR: 0 Reply 6, posted (12 years 5 days 18 hours ago) and read 1845 times:
When I used to fly CX to HKG a fair bit, they used to have their 'air show' running during take-off at AKL. Pretty much every time, the ground speed was ~200kts at rotation. This was for a 742 by the way.
PhilB From Ireland, joined May 1999, 2915 posts, RR: 14 Reply 8, posted (12 years 5 days 16 hours ago) and read 1825 times:
762er,
You are not grasping the concept. It may be possible to give a take off speed on the "average day" at empty and full, but what does that tell you? Flap settings will also vary.
Calculating take off speed is a very exact science. It isn't a case of "at around 120 we'll call it V1 a bit faster V2 and the book says we could be at VR at around 160.
Each take off is individually calculated and the flap settings (which, I grant you are more likely to fall into a "typical" band) are determined by the performance those calculations call for.
762er From United States of America, joined Feb 2001, 540 posts, RR: 2 Reply 10, posted (12 years 4 days 21 hours ago) and read 1794 times:
I'm well aware of all the factors you have to take into account to calculate take off speed. However, there are fairly consistent knots indicated airspeed velocities for an aircraft at full weight. It doesn't vary that much with temperature and altitude. All I'm looking for here is a rough estimate for the rotation velocity of fully loaded 764 at sea level and 70 degrees absent winds give or take a few kias. Why you gotta be so picky and technicl all the time?
PhilB From Ireland, joined May 1999, 2915 posts, RR: 14 Reply 11, posted (12 years 4 days 21 hours ago) and read 1792 times:
Because being picky and technical and ACCURATE is what a sensible answer to a question is all about.
If you wanted to know the question you have finally asked then you should have asked it. If you think take off speed doesn't vary much with temperature and altitude, you need to do more reading.
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