A friend piqued my curiosity ... we got into a discussion regarding flying and he asked about what speed does a plane takeoff at. We tried the internet but couldn't find an answer so I thought I'd try here. Any answers.

Thanks.

Different aircraft achieve take-off at different speeds. Wind speed and weight (probably) come into play. Did you try www.ask.com

Or go to http://aviation.about.com/hobbies/av...tm?PM=69_837_T


[This message has been edited by Comicwoman (edited 09-28-2000).]

"Takeoff speed" can mean a lot of different things...

First of all, when we're talking about speeds in an aircraft, the speed that matters is airspeed, not ground speed. It is the movement of air over the wings that generates lift, not the movement over the ground. In fact, if you had a strong enough headwind, you could fly "backwards" because even though you're going 100 knots airspeed, you are heading into a 110 knot headwind. In this case, you'd be moving 10 nautical miles backwards every hour along the ground.

Vmu, Velocity miminum unstick, is the slowest airspeed at which a given aircraft under a given load can take off. Determining this speed involves putting a tail skid on the test aircraft, and rotating up so the tail skids on the runway until enough speed is achieved to lift off. It is a rather spectacular test.

However, airline pilots would get into quite a bit of trouble with management if they attempted this. Most people have a misconception that there is a magic number called "takeoff speed" which is the speed at which the aircraft wheels lift off the ground. In reality, there are three speeds which are of importance during takeoff, V1, Vr, and V2. V1 is decision speed, which is the fastest speed at which a rejected takeoff (abort) can be performed safely on the remaining runway length. Vr is rotate velocity, the speed at which the pilots pull back on the yoke to rotate the aircraft nose up for takeoff, but the main wheels are still on the ground. V2 is minimum takeoff safety speed, which is the mininum safe flying speed if an engine should fail. By the time V2 is achieved, the wheels have left the ground.

These speeds are determined, for a given aircraft type, by the weight of the load, air density and temperature, and other factors. Air density and temperature are important because the less dense and hotter the air, the less lift it will be able to generate, thus increasing the speeds necessary to achieve lift.

I imagine this is already more complicated an answer than you were hoping for, but this doesn't even begin to break the ice. A "simple" answer to your question may be:

For a fairly typical configuration on an average day, A B777 sets V1 about 150 kts, Vr at maybe 154 kts, and V2 at about 160 kts. I suppose some may want to know that a knot is a nautical mile per hour, or approx. 1.12 statute miles per hour.

Yeah, what Jet said!

jet, that was a really great answer! gave me insight to questions i had regarding take-off! thanks!

Buy Microsoft's Flight Simulator and you can get a good feel of takeoff speed range for a number of aircrafts including the 766 and the Concorde.

V2 on the 734 is generally around 150 kts. This would be in terms of standard temperatures and a full pax load (but not a full cargo load). This would not be in terms of KIAS. So I understand, 737s are not the best aircraft for hot temperatures, and you'll be rolling for a lot longer in Phoenix in the middle of the summer.

A 767-600 would definitely be quite a "stretch"

[This message has been edited by West Coast Flier (edited 09-28-2000).]

One thing I always wonder when taking off is what would happen if the back of the plane did hit the ground, I know test jet's have large wooden blocks attatched but how about a regular one? Would it be catastrophic or just make a load of sparks on the runway?

[b]jet[b], that's gotta be one of my all-time favorite posts on FT. Great stuff!!!

Thanks jet ... I knew a lot went into the takeoff formula, but now I realize what some of those factors are. Your answer couldn't be more perfect!

Jet:
Your technical response is a breath of fresh air. It's what this forum is supposed to be about. Thanks for reminding us.

An interesting thread . . . Thanks