When a 747 is taking off, how fast is it moving down the runway?
On average, about 220 miles per hour. Interestingly, the Concorde takes off at the same speed.
According to my Microsoft Flight Simulator, the V_r of a 737 is around 143 knots, or appx 1.1*143 miles per hour. I think for a 747 it is pretty close (maybe a little more, like 10 knots). This is the speed to begin rotating the nose up for takeoff. You should be off the ground by about 150-155 knots. For a 777, rotate speed is 153 knots and 160 knots is takeoff safety speed.
The Concorde rotate speed is 190 knots, with takeoff safety speed of 210 knots.
I believe the number I gave above was off. I’ve flown in two 747’s and one 777 that gave the speed and altitude on the inflight screens and the takeoff speed for the 777 was about 180mph. The 747’s were a little slower than that, maybe 170 or so? Sorry that’s not more specific as I’m about as far from a pilot as one can get.
R-n-R, who is now anticipating a collective reaming from all the pilots out there… =-)
This is what British Airways have to say on the matter:
Series 200 - 206 mph (332 kph);
Series 100 - 191 mph (306 kph).
I’m assuming here that this is the speed where the plane actually becomes airborne.
Oh, darn it. This is the measure for the latest incarnation, the Series 400.
Take-off speed: 207 mph (334 kph).
For years, I had a office that overlooked Washington Nat’l Airport.
I was rather amazed at the 757’s that took off from there going north. Once they got to take off speed, they have to change their angle to about 45[sup]o[/sup], I guess because the runway’s so short, or because of airspace restrictions just north of the airport (White House, Pentagon, etc.).
I looked through my books on planes and they have a small section on take-off performance tables. In short it depends on the the size of the plane, weight, lenght of runway, altitude of airport, wind speed, pressure. Headwinds decrease the amount of distance quite a lot, while tail winds are add to it by even more. I don’t have a speciffic chart for any planes though. but it says that pilots are required to know all of the chart for every type of plane they fly.