the plane on the conveyer belt - a different question

[Admiral Valdemar]

Who thinks airplanes fly because of their speed relative to the ground, anyway?

A lot more people than you'd suspect.

Hence, I expected that to be the main point. It's probably something that the people who think a duck's quack doesn't echo would fall for.

[Dooey Jo]

A lot more people than you'd suspect.

Hence, I expected that to be the main point. It's probably something that the people who think a duck's quack doesn't echo would fall for.

But then I think the question is over-complicated. Why not just say that the plane is anchored to the ground like a kite but it's propellers or jets are at maximum power; will the plane lift? That would be unambiguous (unless we're talking about those VTOL planes)...
Or maybe: If you put wings on a fast car and drive at full speed, will it fly? To demonstrate thrust...

As the wheel rotates faster it heats up and that changes the surface of the tires; this is why drag racers intentionally use friction to heat the tires to get better performance.

And also F1 racers, but it's bad for the tires (which are very soft to begin with), which is why they have to change them all the time. But in this scenario, I think that qualifies as non-normal conditions

[Sea Skimmer]

And also F1 racers, but it's bad for the tires (which are very soft to begin with), which is why they have to change them all the time. But in this scenario, I think that qualifies as non-normal conditions

Well F1 uses tire heaters, which do no damage to the tires, while drag car use a quite destructive burnout for the same purpose.

[Dendrobius]

This is a stupid question. Assuming the landing gear can take effectively infinite speed, the plane is going to take off.

The key is that the force being applied to the aircraft comes from the engines, not from the rotation of the wheels. Draw yourself a free body diagram and it's pretty darn obvious. High school kids can and will get stumped, any first year engineering student should be ashamed of him/herself if they get this wrong.

Rolling resistance from landing gears is pretty minimal compared with engine power for most types of aircraft anyway. Although yes we do have to factor it in when we're calculating for takeoff ground roll and yes we would theoretically have to take it into account for this scenario, but it really isn't a dominating factor, and can be ignored.

[Broomstick]

But then I think the question is over-complicated. Why not just say that the plane is anchored to the ground like a kite but it's propellers or jets are at maximum power; will the plane lift?

If the airplane is anchored by, say, roping or chaining it to the ground so that it can't move, and the air is calm, then you may run the engine(s) at full throttle and it won't go anywhere and it won't lift off unless the tether breaks. If the airplane can't move at all relative to the air around it then it can't fly (unless you're talking rocket-thrust). In calm air, airspeed and ground speed are equal. No groundspeed at all means no airspeed. It's no different than holding the brakes on the airplane and running it full throttle, which (assuming the brakes hold) results in a lot of noise and maybe some shaking of the machine from engine vibration but nothing like flight.

Now, if the airplane is anchored and the wind is blowing sufficiently fast then yes, the plane will lift and "hover" (assuming there's enough slack in the tether(s) unless, again, the tether breaks). On some exceptionally windy days I've even witnessed this myself. Doesn't even require engine power - from the wing's perspective it makes no difference if it's the airplane moving through the air, or the air moving past the airplane. Airspeed is airspeed.

If you truly turn the airplane into a kite - that is, it's not chained to the ground but on a long tether like a flying kite - well, as long as the airplane is able to generate airspeed it will fly, or if it's overpowered enough to "hang on the prop" or get lift from thrust alone -- but that's certainly not your average airplane.

Or maybe: If you put wings on a fast car and drive at full speed, will it fly?

Yes, it will become airborne - briefly. It won't stay in the air because wheels spinning in the air do not generate sufficient thrust to maintain airspeed. There will also be some issues with control, as cars do not possess rudders or elevators. I hope you at least have ailerons on those wings, or you'll be trying to steer by strategic opening and closing of doors or something simillar, assuming you have time to try that before crashing back to the ground.

You probably won't even need to drive at "full speed" if there is an actual wing on the car - take-off speeds are lower than most people think they are.

[Braedley]

This is a stupid question. Assuming the landing gear can take effectively infinite speed, the plane is going to take off.

The key is that the force being applied to the aircraft comes from the engines, not from the rotation of the wheels. Draw yourself a free body diagram and it's pretty darn obvious. High school kids can and will get stumped, any first year engineering student should be ashamed of him/herself if they get this wrong.

Rolling resistance from landing gears is pretty minimal compared with engine power for most types of aircraft anyway. Although yes we do have to factor it in when we're calculating for takeoff ground roll and yes we would theoretically have to take it into account for this scenario, but it really isn't a dominating factor, and can be ignored.

I was like "shit, that's right, wheels don't matter," but I have an excuse, I'm in electrical. Thanks to Psycho Smiley for pointing me in the right direction.