The Mythbusters bit was so flawed I'm surprised they aired it.....they used an ultralight aircraft that became "light" after about two seconds, hence started to develop lift and wasn't even in constant contact with the "conveyor belt" being towed behind the truck.
jonsad: You are correct in your statement that the plane gains it speed through the prop; however, the wheels are on the plane to roll the plane until it develops enough speed for lift to carry it off the ground. With the speed of the "conveyor" and the speed of the planes forward motion matched, it will not develop the needed airspeed to lift off the ground.
This guy does a great job of explaining....
http://www.airplaneonatreadmill.com/
Read the entire explanation...The answer to the question, THE WAY YOU ASKED IT, is NO, it will not fly. If the treadmill or conveyor ALWAYS MOVES AT THE SAME SPEED, THE PLANE CANNOT DEVELOP LIFT.
The reason so many people say it will fly is because they are conceding the fact that no conveyor/treadmill in the world can accomplish the feat of exactly matching a planes forward rolling speed. The question is inherently flawed, but to answer it in the spirit of the way the question is intended....NO!!
P.S. I love it when someone gives a "thumbs down" to a correct answer....
Thank you jttexas!!! I imagine the people that think it willl fly also feel a strong 20 mph wind on their face when they are at the gym "going 20" on a stationary bike!!.....Or when they put their car on blocks and rev the engine until it says 100 mph, they put their arm out the window and expect it to blow back!!
Good job, Louis!!!
You can lead the horse to water.....
Again, those of you that belong to "the plane doesn't need friction on the ground" camp; you are correct, but there IS friction and it is not a factor in the question you can choose to ignore. It's like asking someone "How fast could a Nascar car go?" I answer aproximately 210 mph....you reply: "No, I'm saying with no friction in the wheels, no energy loss in the conversion of fuel to h.p., no wind resistance, no ground resistance, etc." Friction IS a part of the equation; if anything, the question shows how much actual energy it takes to overcome it's effects in everything we do.
You are changing the question to suit your answer....if the "conveyor" belt exactly matches the speed that the plane would normally achieve during run-up...IT SIMPLY WILL NOT FLY. (It doesn't move) A plane cannot fly until it builds up enough speed ON THE GROUND to develop lift. I guess I'm wondering why in the world we have 8,000 foot long runways if all we need to do is put a 747 on a football field-size belt and flip a switch? (It really wouldn't be that hard to engineer and build, just expensive..) The hundreds of millions of dollars saved in real estate would surely be enough for airports to lower ramp fees and save money for airlines, thus saving the airline industry. All of you in the "it will fly" camp should get together and make some money!! Why do aircraft carriers use a launching system to get jets off the short carrier jets? According to your theory they don't need any friction on the ground do they?
A boat doesn't need friction on the ground to move either, does it? So if a boat is moving nicely along a river at 10 kts and suddenly a current of 10 kts in the opposite direction develops; according to you the boat will keep going at 10kts, right?.?.?.? (Remember, the boat doesn't need friction from the ground to move)
Dennis (below) also explains nicely...but again, in the question the "asker" never says "imagine a plane with 100% efficient wheels, bearings, (they don't exist) and a conveyor belt that has unlimited speed and a 100% frictionless surface".
So I now will add to my previous statements; According to the laws of physics as we know them, and the physical and mechanical limitations of technology we have available to us, it is impossible for the plane to fly off the conveyor belt, as the question is posed.....If you are able to develop a totally frictionless (100% efficient) wheel/bearing and a conveyor belt coated with Clark Griswold's cooking spray (think Christmas Vacation), not only will you be a ga-billionaire, I will admit defeat!!
Anyway...great question, great answers (wrong or right), I'm moving on to the "chicken or the egg"!!!!:)Can a plane fly on a conveyor belt?
The plane will fly. the reason is because the plane gains speed through the propeller not the wheels. say the plane needs to reach 150mph to take off. if the conveyor belt is moving at 150mph the wheels(only the wheels) are moving at 300mph. The plane itself,excluding the wheels, is moving at 150mph. which is what it needs to take off.Can a plane fly on a conveyor belt?here's the deal: the conveyor belt is moving at the same speed but opposite of the aircraft, then the aircraft will be stationary.
If the aircraft is stationary, then the conveyor belt (moving at the same speed) will be stationary as well.
No movement, no flight.Can a plane fly on a conveyor belt?
Absolutely not!
All that matters to an airplane is the speed (well, and density but lets ignore this fact for purposes of this discussion) of the air moving over the wing and other control surfaces.
Lets start this from the beginning to see a clear example of why.
1) The airplane is completely stopped and sitting on the stationary conveyor belt.
Total tire speed: 0 MPH
Total air speed: 0 MPH
2) The conveyor belt starts to move (in reverse, compared to the direction the airplane is facing.) It accelerates to the flying speed of the airplane (lets say 120 MPH)
Total tire speed: 0 MPH
Total air speed: -120 MPH
3) The airplane starts to move under it's own power and accelerates to it's normal flying speed (120 MPH). The speed of the conveyor is now offset by the speed of the airplane.
Total tire speed: 120 MPH
Total air speed: 0 MPH
The airplane is now completely stationary compared to the air around it and objects beside it. With no air flowing over the wing, it can not fly. You could stick your hand out the window and feel nothing (but it would be pretty loud between the engines and the conveyor belt! :-) ).
4) Add more power! The airplane accelerates to 240 MPH and could lift off the conveyor belt at "normal" flying speed, and would then start to accelerate beyond the 120 MPH once it lifted off the conveyor because of the excess power.
Total tire speed: 240 MPH
Total air speed: 120 MPH
Liftoff!
Now, there is a similar question (not asked here but many people consider it when pondering the answer to this question) about what happens if an airplane is pointed into a 120 MPH wind. Will it fly now, even if the engines are off? Absolutely, but not for long! The reason is that as soon as the airplane lifts off (it has the required air moving across the wings, so it will get airborne easily) it is not developing it's own thrust and is not being held in place by the ground anymore, so it will start to drift with the wind. As it does this, the "relative wind" going over the wings drops to zero (imagine a kite that got loose: it is moving WITH the wind, not THROUGH it anymore.) and the airplane drops (quite firmly) back to the ground.Can a plane fly on a conveyor belt?This question cracks me up every time I hear it. The only way the plane would remain stationary is if the pilot applied barely enough throttle to overcome the friction in the wheels. Any more throttle, the propeller/jet would move him forward, allowing it to attain the required airspeed for takeoff. It doesn't matter how fast the belt is moving underneath, unless it got so fast that the wheels started breaking apart.
How the wheels are moving have nothing to do with being able to take off. All that matters is the air flowing over the wings.
Read the link the person above posted. It explains well why it would take-off.
edit: In your question, I'm measuring the speed of the plane with relation to the earth that the belt is sitting on, and not in relation to the belt itself, or else the plane would just be stationary and never take-off.Can a plane fly on a conveyor belt?
When on a treadmill, you move by pushing your feet against the treadmill, you need friction... same thing with a car. A plane, however, doesn't need friction on the ground to fly, the wheels need not spin...
Think about it...That is why we have muscles in our feet/legs, cars have power applied to their wheels but all that planes have is brakes on their wheels...Can a plane fly on a conveyor belt?
This exact same question was asked on the AOPA forums. A forum of pilots, and there was a huge debate as to weather or not the airplane could fly.
The answer is maybe. If the friction of the wheel bearings and tires is low enough then the airplane will be able to fly. Remember Newtons first law, an object at rest will stay at rest. So If an airplane were sitting on a conveyor, and the belt was turned on, with perfectly efficient wheels and bearings the airplane would not move. Any thrust from the engine(s) would move the airplane just as it would on solid ground. There would be no effect of the conveyor belt in an absolutely perfect world.
We do not live in a perfect world. Tires are not 100% efficient, neither are their bearings. The extent of the inefficiencies and the available thrust will determine the outcome of the experiment. If there is enough thrust available to overcome the drag, and still propel the aircraft forward to a speed needed for flight, then the airplane will fly. If the drag from the wheels and tires is so great the engine cannot overcome the drag by takeoff speed, then the airplane will not fly.
The short answer. In theory, absolutely. In reality, maybe but probably not.
Some of you guys forget.
It's not how fast the aircraft moving in relative of the conveyor belt. It's how fast the winds are moving through the wings. That's what make airplanes fly. Not the speed of the tires.
So no matter you put 500knots conveyor belt moving backwards and the airplane is moving 500kts forward relative to the conveyor belt, as long as the aircraft speed in relative to ground is 0 (aka no wind moving through the wing), it won't fly.
Let's change the question a bit;
How if I put a cessna 172 in front of a huge fan, blowing 90kts, and the cessna engine is set at an rpm that would normally fly it at 90kts. How will it fly?
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