The ground is stationary and moves at the same speed as the wheels as well..........just sayin. I love this thread it is a fun read. One weekend I read every page of it.
A conveyor belt moving at a constant speed will not impart a net force (through frictionless wheels) on the center of mass of the plane, with jets off. But ... An accelerating conveyor belt will impart a net force (even through frictionless wheels) on the center of mass of the plane, with jets off. So ... A constant-speed conveyor cannot keep the plane stationary (relative to surrounding air), with jets on. But ... An accelerating conveyor can keep the plane stationary (relative to surrounding air), with jets on. HUGE difference between inertial, and non-inertial, frames of reference.
"frictionless wheel bearings", for clarification (above). There is, of course, friction between the tire and the belt in all cases.
So you think those hot spinning tires will have enough friction to hold back an F22 with 70,000 lb's of thrust ?
Original question said "plane", not "jet" (even though i said "jet"), did not specify a thrust level, nor specify a period of time for which the balance of force needs to work Nonetheless, my point stands : - The plane will NOT experience a net force, from a conveyor moving at a constant speed (frictionless wheel bearings). In fact, the plane will recognize and react to ALL constant-speed conveyors, as if the (constant) speed of the conveyor were identically zero. - The plane WILL experience a net force, from an accelerating conveyor (even with frictionless wheel bearings). This is not a small difference ... it's a very fundamentally different situation, quite analogous to the difference between an inertial and non-inertial frame of reference. The magnitude of the force will indeed be limited to the friction force between the surface of the conveyor and the tires ... will this be enough to hold a small prop-plane stationary for a second or two, to satisfy the original question? hmmmmm ...
poster is sucked in by the misdirection... too much information... propulsion and amount is totally irrelevant... there is great entertainment value in fictional explanations
Funny, Webster thinks a jet IS a plane: Definition of jet a :an airplane powered by one or more jet engines b :jet engine https://www.merriam-webster.com/dictionary/jet A better argument would be that the F22 is a VTOL, considering the ability to sit on it's tail and accelerate. Or that perhaps the tires would fail before the "jet plane" got off the ground. Does the original question allow us to substitute steel wheels for the aluminum alloy ?
In order for the plane to move forward whilst still meeting the requirement of spinning the wheels at the same speed as the conveyor, the tires will have to skid. So propulsion is relevant. It's question of propulsion vs. tire traction. As one who has locked up more than once, I can tell you a skidding tire doesn't have much traction.
the original post states the conveyor is there NOT to induce any forward motion, to insure that the plane remains in place motionless... as also the reference to the wheels allows for NO motion the UTube data is corrupted in the demonstration, conveyor and belt motion is NOT synchronized, there is inconsistent uncontrolled acceleration/power applications which corrupts (allows forward motion) the data necessary for flight, allowing for forward motion and some flow across the foils one should focus on the foils, they are what determine flight or no flight, no flow over the foils, no flight, as in airplane mode, best illustrated by a kite or glider... tether each and they will fly as soon as sufficient air flow is present for the foils to work... yet remain without forward motion
Agree. So, if the plane has a propeller on the front of it, then that propeller will make air flow over the center part of the wings. May or may not be enough airflow to create lift off of the treadmill, but if it does create enough airflow for some lift, then the plane will fly as it moves forward in the air (since its wheels are no longer in contact with the treadmill). But, if it is a pusher propeller on the back of the airplane, like a Rutan VariEze design, then no airflow will be created over the wings and the plane will not fly. What is needed is the building of a correct large treadmill to demonstrate this. .
Let's follow your premise, that "propulsion is totally irrelevant" ... and set propulsion to zero. We'll also set the conveyor speed, and acceleration, to zero. I think we would all agree that the plane does not take off thread closed ! Entertaining thread indeed full of fiction ...
treadmill is the misdirection, totally irrelevant, prop either push or pull will stimulate some air flow, the main force is thrust to move foils through air, which motion goes to flight... in push mode air is being sucked from in front of the prop allowing for some flow over the foils, but forward motion is the real motivator... if more is attributed to the effect of air flow over the foils from a power source as a propeller, one would be getting into perpetual motion, which as we currently know does not exist air flow over foils is the requirement for flight to occur... head wind can substitute for motion, the simple example is a kite
that is the misdirection in the original post... not my premise, it specifically states NO motion as it maintains forces in equilibrium
So, let's take the case of a small airplane like a Cessna 172. It has a front propeller and can get to about 125 knots (143 mph) airspeed as a top speed. You are saying that the airflow from the propeller at full throttle is enough to get the plane airborne if the treadmill is moving fast enough in the opposite direction to keep the wings in the same position (not moving forward or backward from a fixed position). .
"No motion" is a straw man that you created. What the original post states is that the conveyor speed matches the speed of the wheels. This does not prevent motion, because tires can, and do skid. As you can see from this video, the skidding tires do little to slow the plane.
NO, that is not being said. with only prop wash, flight needs additional flow from thrust over foils for flight
the original post makes an effort to exclude any forward motion, re read it.... carefully... you are making things up
Well then why not just ask the question - can a plane take off with no forward motion - and just eliminate any mention of the treadmill altogether ? Not much of a question there eh ? The problem with your limited thinking is that you never considered the possibility of the tires skidding.
the real problem is you are not comprehending the op, read again and you will not bring up tires again
Okay. I read it again. And I still think with a powerful plane would skid the tires and take off - as long as the tires can hold together long enough for the plane to get in the air. How about you explain why you think the plane would not move forward. In detail. And "read the op again" is not an explanation.
the op states that any motion is not part of the question... any reference to anything other than flight is misdirection away from any realities...
The coefficient of friction between rubber and asphalt is 0.5 ~ 0.8 ... let's call it 0.5. Therefore the friction force available for tires on an accelerating conveyor is about half the weight of the plane (no such force exists for a constant-speed conveyor, of course). So ... if the prop (or jet engine) is providing a thrust less than about half the weight of the plane, a backward-accelerating conveyor can indeed keep the plane stationary relative to surrounding air.
