Who's right?
- Thread starter gurusan
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My answer depends:
1. If the movement of the treadmill is such that it keeps the plane stationary relative to a fixed point on the ground then it will not take off. The wheels will not 'freewheel'. Imagine the plane is sitting still with no thrust from the engines. The tradmill it is sitting on starts moving backwards. The plane will move backwards with it. The wheels will not spin under it and keep it in the same place relative to a fixed point. Therefore when it is trying to move forward using its engines the backward moving treadmill CAN keep it stationary relative to the fixed point.
2. If the movement of the treadmill still allows the plane to move forward relative to this same point then it will take off. However it will take more thrust to overcome the backward force provided by the treadmill.
1. If the movement of the treadmill is such that it keeps the plane stationary relative to a fixed point on the ground then it will not take off. The wheels will not 'freewheel'. Imagine the plane is sitting still with no thrust from the engines. The tradmill it is sitting on starts moving backwards. The plane will move backwards with it. The wheels will not spin under it and keep it in the same place relative to a fixed point. Therefore when it is trying to move forward using its engines the backward moving treadmill CAN keep it stationary relative to the fixed point.
2. If the movement of the treadmill still allows the plane to move forward relative to this same point then it will take off. However it will take more thrust to overcome the backward force provided by the treadmill.
Surely if the thrust were coming from the wheels though, and the treadmill matched the speed, but in the opposite direction, then the aircraft would remain stationary? If so there would be no airflow over the wings, and therefore no lift. Unless I'm missing something?Jokester said:
This is assuming there is no wind as well.
Jotun said:
If it was on a treadmill it won't take off, but if it wasn't there's no reason why it can't if it can generate sufficient forward speed so that the airflow over the wings generates sufficient lift.
There was a good example of this when a race car spun off backwards, but it was travelling sufficiently fast that the rear wing actually generated enough lift that the car actually glided through the air.
Jokester
Scuzi said:
In a german accent - but the principle is the same
If a full size plane has a silly amount of thrust, and a quick blip at 100% is enough to take off within 5 metres, it's not speed via lift under the wing that is causing it to fly, but thrust from the prop over the wings and thrust in a VTOL like manner, it doesn't have to be VTOL planeto have incredibly short take off speed if the engines provide enough thrust.
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Lift is dependent on air moving over and under the wings. If the plane stays stationary relative to the air, then it will not take off.
Anyone arguing otherwise doesn't understand physics.
Don't even try to argue. You are wrong.
Now about this sandwich...
Anyone arguing otherwise doesn't understand physics.
Don't even try to argue. You are wrong.
Now about this sandwich...
But the wings aren't flying, they are stalled in such an instance. Very few aircraft can perform such manoeuvres, usually very powerful and very light SEP/Turbine aerobatic aircraft and only in ideal conditions.squiffy said:In a german accent - but the principle is the same
If a full size plane has a silly amount of thrust, and a quick blip at 100% is enough to take off within 5 metres, it's not speed via lift under the wing that is causing it to fly, but thrust from the prop over the wings and thrust in a VTOL like manner, it doesn't have to be VTOL planeto have incredibly short take off speed if the engines provide enough thrust.
True but the function of the wings at this point doesn't matter, getting off the ground is what is what the OP asks. Rockets don't have wings, but they have thrust, and lots of it.
The lift from the wings occurs when a high enough airspeed is reached, helped but the take off from the powerful engine. ie prop-hang (wings provide no lift here) pulling up and accelerating from the prop-hang, and/or levelling off and accelerating again.
The question was "will it take off" the method wasen't stated down how, depending on the plane design.
The lift from the wings occurs when a high enough airspeed is reached, helped but the take off from the powerful engine. ie prop-hang (wings provide no lift here) pulling up and accelerating from the prop-hang, and/or levelling off and accelerating again.
The question was "will it take off" the method wasen't stated down how, depending on the plane design.
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Taking off without lift from the wings would have the aircraft in an uncontrollable state. It would be inherently unstable due to no airflow over the wings, and no fin/rudder authority. On such a powerful aircraft, the torque effect from the engine would flip the aircraft upside down.squiffy said:
It is possible once airborne and performing aerobatic manoeuvers at a sufficient height, but to depart with no lift from the wings is nigh on impossible and extremely dangerous/careless.
It might be possible with your toys but with the real thing I'm afraid it isn't the case
This is easy once you know it, heh/
@big_white_dog84 -- the wheels will 'freewheel'. Everybody who still cant understand it, think of it like this..
How easy is it to push a shopping trolley on a conveyer belt? Very easy. Now think of this. That trolley is a plane, and your force is now the plane's engines. The plane will move forward. Easy. Done. End of debate.
The wheels dont cause any major resistance to the plane moving forward because they 'freewheel'. Essentially, the conveyer belt makes no difference. The plane will move forward pretty much as normal, and eventually take-off.
@big_white_dog84 -- the wheels will 'freewheel'. Everybody who still cant understand it, think of it like this..
How easy is it to push a shopping trolley on a conveyer belt? Very easy. Now think of this. That trolley is a plane, and your force is now the plane's engines. The plane will move forward. Easy. Done. End of debate.
The wheels dont cause any major resistance to the plane moving forward because they 'freewheel'. Essentially, the conveyer belt makes no difference. The plane will move forward pretty much as normal, and eventually take-off.