Can the plane take off?

[tc410]

Can’t believe you got sucked into this

No shit. Me either. I’ve sworn off all the vitriol back and forth nonsense down in the basement. At least no one has blamed this airplane theory on trump, biden or the vaccine. Yet. Of course the captard @El Capitan oughta be coming up for another bag of Doritos soon so I’m sure he’ll change all that.

 

[Fill Ess]

Can’t believe you got sucked into this

C'mon, you're only here because someone mentioned Tom Selleck

 

[mrsrobinson]

There’s no mention of headwind in the OPs proposition. Where are you getting this headwind theory from?

THIS

As it's written, exactly, the plane will not take off.

 

[Stee6043]

There’s no mention of headwind in the OPs proposition. Where are you getting this headwind theory from?

Acknowledging the effects of a headwind across a wing that is stationary relative to the ground will fully illustrate that these plans we're talking about will absolutely, without a doubt, fly.

I'm actually surprised so many of you guys actually think this plane won't take off. Yall gotta stop thinking about those wheels....and ground speed. There's a reason that planes will generally take off AND land going into the wind...and it's got nothing to do with the wheels/SOG but everything to do with lift/stall...

 

[mrsrobinson]

My good friend, Google, says otherwise:

 

[Stee6043]

My good friend, Google, says otherwise:

That's funny, you should read the comments. He's wrong. And comparing a car to a plane in this scenario couldn't be more silly.


Mythbusters actually did it:

 

[tc410]

The better question would be.
If the plane were sitting perfectly still in a perfect straight on 200 mph head wind would it take off while sitting perfectly still.
Yep, it would.

I agree. But that’s NOT the question.

 

[Great Lakes]

New twist..

 

[Blueone]

C'mon, you're only here because someone mentioned Tom Selleck

……and phuck Tom

 

[Woody]

I can see some of you aren't ready to find out why your boat steers left or right when you turn the rudders.

 

[Woody]

Acknowledging the effects of a headwind across a wing that is stationary relative to the ground will fully illustrate that these plans we're talking about will absolutely, without a doubt, fly.

I'm actually surprised so many of you guys actually think this plane won't take off. Yall gotta stop thinking about those wheels....and ground speed. There's a reason that planes will generally take off AND land going into the wind...and it's got nothing to do with the wheels/SOG but everything to do with lift/stall...

Back in school, the the dreaded word problems, the teacher would always say, 'read the problem carefully'.

 

[Henry Boyd]

Matched the speed of the wheels. If the thrust of the engines is moving the aircraft down the conveyor (which is the length of a runway) who cares what the wheels are doing? Unlike a boat the thrust isn't using the conveyor (water).
Now if the thrust is normally rotating the wheels by moving down the runway then therefore as the conveyor is countering the wheel movement the wheels are not rotating even though the aircraft is moving down the runway (conveyor). Now, read another way the conveyor is operating opposite the aircraft moving down the runway then the wheels will spin double normal.
spinning the wheels has nothing to do with the aircraft moving under it's own power.

Almost right. The wheel rotation speed is a function of thrust: as thrust increases plane moves forward (if the ground provides friction) and the wheels spin faster and faster. As the plane moves forward lift is created and it flies. But if the ground under the wheels always matches speed in the opposite vector of the wheel rotation the plane stays stationary. The plane wings need to be moving fast enough through the air to generate lift, or as it was put to us in aero 101 the air has to be moving over and under the wing fast enough to do the job.

Now we get back to deceptive wording, a “plane” by definition does not generate enough thrust to leap instantly into flight because it relies on sub sonic aerodynamics, or the difference between the air pressure on the top and bottom of a wing. If it had been talking about a missile or rocket, which is a ballistic process, your argument holds up. If you look at supersonic aircraft, they have two configurations, one for sub sonic flight and one for supersonic. The Concorde had a fixed wing configuration but barely managed sub sonic flight; only enough to get the nose pointed up and then it went into guided missile mode.

 

[tc410]

Almost right. The wheel rotation speed is a function of thrust: as thrust increases plane moves forward (if the ground provides friction) and the wheels spin faster and faster. As the plane moves forward lift is created and it flies. But if the ground under the wheels always matches speed in the opposite vector of the wheel rotation the plane stays stationary. The plane wings need to be moving fast enough through the air to generate lift, or as it was put to us in aero 101 the air has to be moving over and under the wing fast enough to do the job.

Now we get back to deceptive wording, a “plane” by definition does not generate enough thrust to leap instantly into flight because it relies on sub sonic aerodynamics, or the difference between the air pressure on the top and bottom of a wing. If it had been talking about a missile or rocket, which is a ballistic process, your argument holds up. If you look at supersonic aircraft, they have two configurations, one for sub sonic flight and one for supersonic. The Concorde had a fixed wing configuration but barely managed sub sonic flight; only enough to get the nose pointed up and then it went into guided missile mode.

You said it much better than me

 

[ttmott]

Almost right. The wheel rotation speed is a function of thrust: as thrust increases plane moves forward (if the ground provides friction) and the wheels spin faster and faster. As the plane moves forward lift is created and it flies. But if the ground under the wheels always matches speed in the opposite vector of the wheel rotation the plane stays stationary. The plane wings need to be moving fast enough through the air to generate lift, or as it was put to us in aero 101 the air has to be moving over and under the wing fast enough to do the job.

Now we get back to deceptive wording, a “plane” by definition does not generate enough thrust to leap instantly into flight because it relies on sub sonic aerodynamics, or the difference between the air pressure on the top and bottom of a wing. If it had been talking about a missile or rocket, which is a ballistic process, your argument holds up. If you look at supersonic aircraft, they have two configurations, one for sub sonic flight and one for supersonic. The Concorde had a fixed wing configuration but barely managed sub sonic flight; only enough to get the nose pointed up and then it went into guided missile mode.

Man Henry - auger in (airplane talk).....

• The wheels are independent and have nothing to do with "lift" and taking off - that is the wing's job.
• The wheels can spin fast, slow, forwards, or backwards as long as the aircraft moves forward fast enough to create lift.
• The engine thrust moves the aircraft forward regardless what the wheels are doing on the conveyor belt. Part of the hint is the conveyor is as long and wide as a runway.

 

[spikedaddy99]

In the Mythbusters scenario, the plane is moving forward relative to ground (see the orange cones) so that scenario isn't the same.

 

[Creekwood]

It can't take off because it needs air flow over the wings to generate lift. If all it is doing is using the jet thrust to hold it in position on the conveyor, the only air flow over the wings would be what is "sucked" towards the engines that happens to flow over the wings. But that airflow will not go along the entire surface necessary for lift and the majority will run under the wings due to the position of the engines. So no, it cannot take off if the conveyor keeps speeding up to match any forward motion.

Or at least that is what it said in the Holiday Inn Express magazine.

 

[hughespat57]

View attachment 124128

I propose the following hypothesis "The airplane will certainly take off"

The key is always in the words of the "problem"...
It is truly a magic conveyor system that can automatically match the speed of the wheels exactly.
"designed to exactly match the speed of the wheels"

1. Newton’s 1st law states that a body at rest or uniform motion will continue to be at rest or uniform motion until and unless a net external force acts on it.

IF there were no forward movement of the aircraft there would be no movement of the wheels or the conveyor.
THEREFORE the aircraft MUST be moving forward and the conveyor is matching that movement.
This magical conveyor control system can match any increase in speed of the wheels. NO WHERE does it state the the wheels remain in the same location on the conveyor.

2. Newton’s 2nd law states that the acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the object’s mass.

"During take-off power, each GE engine could produce 56,000 lbs of thrust per engine: or 224,000 lbs for a few minutes." My opinion is this is more than sufficient to over come the third rule.
And the magic conveyor is under a matching constant acceleration.

3. Newton’s 3rd law states that there is an equal and opposite reaction for every action.

The reaction force is the friction loss between the tires, bearings and conveyor. Would the increased speed (approximately two times normal 130-145kts) before take is achieved cause the tires to fail? Possibly, but that's a different engineering question. FCOM Max tire speed for a 747-400 is 204kts this is the maximum normal speed.

So the science proves it will fly.

 

[Pirate Lady]

Almost right. The wheel rotation speed is a function of thrust: as thrust increases plane moves forward (if the ground provides friction) and the wheels spin faster and faster. As the plane moves forward lift is created and it flies. But if the ground under the wheels always matches speed in the opposite vector of the wheel rotation the plane stays stationary. The plane wings need to be moving fast enough through the air to generate lift, or as it was put to us in aero 101 the air has to be moving over and under the wing fast enough to do the job.

Now we get back to deceptive wording, a “plane” by definition does not generate enough thrust to leap instantly into flight because it relies on sub sonic aerodynamics, or the difference between the air pressure on the top and bottom of a wing. If it had been talking about a missile or rocket, which is a ballistic process, your argument holds up. If you look at supersonic aircraft, they have two configurations, one for sub sonic flight and one for supersonic. The Concorde had a fixed wing configuration but barely managed sub sonic flight; only enough to get the nose pointed up and then it went into guided missile mode.

 

[jmauld]

The airplane can’t overcome the speed of the conveyor since the theory addresses that the conveyor is designed to exactly match the speed of the tires.

The thrust from the engines doesnt care about the speed of the tires. Nothing on the plane cares about the speed of the tires. That number is meaningless to it taking off. Only speed over ground matters.

 

[jmauld]

Let’s bring this into context. The riddle is deceptively worded. If it said the conveyor belt matches the speed with an opposite vector of the aircraft speed (aka physicists definition of velocity) everybody would get it instantly; you don’t go anywhere when your boat only does 5 knots and you are running into an oncoming 5 knot current.

The conveyor isn’t acting on the body of the plane, the wheels are free to rotate with the conveyor.