Can the plane take off?

Woody said:
Forget the fuselage and engines, I'm talking about the tires, if they're spinning Xmph will they advance down the runway?
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not on a conveyor.
 
I mean....since we're talking turkey....how do normal planes take off from normal runways, heading west, with the earth spinning at 1,000mph west to east?
 
LTD.330 said:
Forget the treadmill.

For all of you who say the plane will fly, why doesn't the plane fly, much less move when the brakes are on and the engines go to full throttle in preparation for takeoff?
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Oh boy...
 
Those that say nay, if the wheels were friction free and the treadmill matched the speed of the plane, would the engines fan blades move to provide thrust?
 
OllieC said:
Those that say nay, if the wheels were friction free and the treadmill matched the speed of the plane, would the engines fan blades move to provide thrust?
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Depends…. Did they vote for Biden or Trump?
 
LTD.330 said:
It is a serious question.
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Mate, I have tried to answer about 5 different ways, even with an example that had Woody on a scooter with a rocket pack!! ;)

It doesn't fly in your example of brakes on because not enough force is created by the engines to overcome the force of friction between the locked tires and the pavement. It's not full throttle, by the way, more like 50% or so. This is to ensure the engines are spooling-up as expected. Once everything looks good, the brakes are released and the throttle set to take-off power. This is not done for smaller or general aviation planes as a rule...varies by pilot. I believe there are some commercial pilots on here that could give more detail. I haven't flown in a long time, and only limited GASE experience.

The difficulty you are having is visualizing what forces are at play. If you know how to draw a free body diagram (FBD), it will help.

Note the engine thrust does not act against the pavement or moving conveyor. That would be the case with a car. The wheels are powered and would be exactly matched in the opposite direction by the counter-acting conveyor. The car wouldn't move. The forward force is in the same frame of reference as the conveyor.

With an aircraft, the engines create force in a different frame of reference than the conveyor- the surrounding air. The pavement/conveyor just adds a small negative force vector on the wheels as it passed underneath that is easily overcome by the force the engines create against the air.

It's a bit abstract for sure, but the plane will definitely move in the frame of reference of someone standing beside the conveyor on non-moving ground. With enough throttle / force, the plane will accelerate, gain speed against the wind (air speed), and with enough force or distance, generate lift and take off.
 
I think it all comes down to what type of bearings are used in the treadmill and if the plane was de-iced prior to the experiment.

Everything else is just nonsense.
 
bajturner said:
It doesn't fly in your example of brakes on because not enough force is created by the engines to overcome the force of friction between the locked tires and the pavement.
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Finally, we are getting somewhere. Now suppose the brakes are released a little and the wheels slowly begin to turn. In the treadmill problem, the treadmill would match the speed of the wheels. The plane would stay stationary relative to its GPS coordinates and no air would be flowing over the wings.
 
It’s not about the wheels. Like I said this is a trick question.

The only way it will be about the wheels is if they are powered or have brakes applied. The wheels will always spin FASTER than the conveyor when thrust is applied to the aircraft.

The same would be true of a car such as THRUST SSC or a rocket scooter.
 
blaster said:
It’s not about the wheels. Like I said this is a trick question.

The only way it will be about the wheels is if they are powered or have brakes applied. The wheels will always spin FASTER than the conveyor when thrust is applied to the aircraft.

The same would be true of a car such as THRUST SSC or a rocket scooter.
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IF that's true, then how can the conveyor possibly "exactly match" the speed of the wheels?
 
LTD.330 said:
Finally, we are getting somewhere. Now suppose the brakes are released a little and the wheels slowly begin to turn. In the treadmill problem, the treadmill would match the speed of the wheels. The plane would stay stationary relative to its GPS coordinates and no air would be flowing over the wings.
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Ah, you're trying to teach me your view! Ok.

You said full throttle, right? Compare the force produced by the engines to the remaining force of the brakes and any friction / drag between the tires and the conveyor. There would still need to be a lot of brake application, I assume. You let off the brakes just enough to start the plane forward to activate the conveyor, correct?
 
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