Mythbusters tonight

[fleaofsc]

Originally Posted by Mainerunr

agreed, somewhere in this thread, someone added a twist that the plane's wheels were moving the same speed as the treadmill which of course changes everything.

You guys don't understand what Mainerunr is trying to say. Both he and I understand what all you are trying to say. Someone else said "Can a plane take of if its wheel speed equals the speed of the treadmill." The answer to that question is NO.

[Zeek]

Originally Posted by fleaofsc

You guys don't understand what Mainerunr is trying to say. Both he and I understand what all you are trying to say. Someone else said "Can a plane take of if its wheel speed equals the speed of the treadmill." The answer to that question is NO.

Actually, it is still yes. If the plane were to throttle up, and reach the specific speed at which takeoff can occur, but does not have flaps set to make the plane take off, they could continue along the treadmill. Stay at that speed, at a constant, they could then change flap position, and take off. Wheel speed and treadmill speed would be equal - they were no longer accelerating. Yet they'd be able to take off as they'd be moving forward at the plane V1 speed. The wheels and treadmill would simply be traveling faster than the plane relative to the ground. That's all. So the answer is actually "Yes, if..." If the plane is taxiing on the tradmill runway at 10mph relative to the ground, of course it won't take off.

[CT_Nismo]

Originally Posted by fleaofsc

You guys don't understand what Mainerunr is trying to say. Both he and I understand what all you are trying to say. Someone else said "Can a plane take of if its wheel speed equals the speed of the treadmill." The answer to that question is NO.

This is an incorrect statement. The plane will take off.

The incorrect theories that abound in this thread have three types of errors.

First is reading comprehension. The statement: "Will the plane take off" implies that the pilot has engaged the engines at take-off thrust. No half throttle, no partial throttle; full take-off power.

The second error is basic physics. The propulsion system on an airplane is by momentum balance. The momentum of high velocity gases exiting the engines is counterbalance by forward momentum. The observed motion of a balloon caused by a sudden release of air is but one example of this principle. You can put wheels on the balloon and put it on a moving conveyor. But the balloon acts on the expulsion of air and will ignore the wheels.

The third error is assuming the conveyor can move the plane. There is only a frictional coupling to work with. This is poor at best. We can compare this with an open differential. In a situation where one wheel has no traction, how much torque is delivered to the other wheel? Not much. The internal friction in the open diff is not sufficient to transmit torque. This is why we have lockers.

If the pilot applies full take-off power to the plane, it will take off. The conveyor can go backwards, forwards, same speed, half speed, twice speed, or any speed, and the plane will take off. There is nothing the conveyor can do to prevent take off because the plane is driven by the forward momentum created by the engines.

[fleaofsc]

Originally Posted by CT_Nismo

This is an incorrect statement. The plane will take off.

The incorrect theories that abound in this thread have three types of errors.

First is reading comprehension. The statement: "Will the plane take off" implies that the pilot has engaged the engines at take-off thrust. No half throttle, no partial throttle; full take-off power.

The second error is basic physics. The propulsion system on an airplane is by momentum balance. The momentum of high velocity gases exiting the engines is counterbalance by forward momentum. The observed motion of a balloon caused by a sudden release of air is but one example of this principle. You can put wheels on the balloon and put it on a moving conveyor. But the balloon acts on the expulsion of air and will ignore the wheels.

The third error is assuming the conveyor can move the plane. There is only a frictional coupling to work with. This is poor at best. We can compare this with an open differential. In a situation where one wheel has no traction, how much torque is delivered to the other wheel? Not much. The internal friction in the open diff is not sufficient to transmit torque. This is why we have lockers.

If the pilot applies full take-off power to the plane, it will take off. The conveyor can go backwards, forwards, same speed, half speed, twice speed, or any speed, and the plane will take off. There is nothing the conveyor can do to prevent take off because the plane is driven by the forward momentum created by the engines.

I am well aware that the pilot could just go ahead and give it enough throttle to take off without the plane being effected what so ever. I was answering a question that one of the guys had about half way through this thread. If you only give it enough throttle to counter balance for the friction and make your speed 0 mph relative to the ground, there is no way the plane is going to take off.

[Chris M]

Originally Posted by fleaofsc

I am well aware that the pilot could just go ahead and give it enough throttle to take off without the plane being effected what so ever. I was answering a question that one of the guys had about half way through this thread. If you only give it enough throttle to counter balance for the friction and make your speed 0 mph relative to the ground, there is no way the plane is going to take off.

I think we all get that, but that has nothing to do with the original question.

[Zeek]

Originally Posted by fleaofsc

I am well aware that the pilot could just go ahead and give it enough throttle to take off without the plane being effected what so ever. I was answering a question that one of the guys had about half way through this thread. If you only give it enough throttle to counter balance for the friction and make your speed 0 mph relative to the ground, there is no way the plane is going to take off.

The plane wouldn't be going fast enough to take off on normal ground in that instance.

BTW: the conveyor most certainly CAN move the plane. Turn the conveyor without having the plane on, and it will move backwords. However the maximum potential for any treadmill to affect the plane is far exceeeded by an engine.

[fleaofsc]

Originally Posted by Zeek

The plane wouldn't be going fast enough to take off on normal ground in that instance.

Exactly and someone didn't understand that. They though that if you made the treadmill go faster and then counterbalance that the plane could take off. I was trying to prove that fact false. You don't need to prove anything to me, I know a plane can't take of going 0.8 mph. I also realize that the plane is driven by a jet engine and not the wheels. The treadmill has ABSOLUTELY NOTHING TO DO WITH THIS SCENARIO!

[CT_Nismo]

Originally Posted by Zeek

The plane wouldn't be going fast enough to take off on normal ground in that instance.

BTW: the conveyor most certainly CAN move the plane. Turn the conveyor without having the plane on, and it will move backwords. However the maximum potential for any treadmill to affect the plane is far exceeeded by an engine.

Put your Frontier on a dyno and spin it up. Does the truck move forward? A moving conveyor is the same as a dyno.

[Mainerunr]

We all agree that the plane could take off if the treadmill speed equals -plane speed, the details of the real wording have been hashed out. Wheel speed is only relevant here if you're using wheel speed to set the speed fo the treadmill because that will set the speed of the plane relative to air. The plane must still reach liftoff speed to get into the air and, if wheelspeed = treadmill speed, the plane is not moving relative to the air...plane velocity relative to air is the only thing that matters for takeoff.

I'm done with this one. Group A not understanding the subtle difference in details being discussed by group B is not getting anywhere.

[s10bowrider]

Yo, someone should try this with a remote control plane and a treadmill, tape it and put the video on you tube. Case closed