Airplane on a conveyor belt

[Cage]

I need to ask a question before I can give an answer... is the pilot wearing a kilt? If so - yes the airplane will take off... Never Underestimate The Power of the Kilt!

Of course, he's "The Kilted Flyer"

Actually the plane will take off even if the pilot is wearing... gasp... p**ts. Even with the slightly greater resistence of a moving conveyor belt the thrust will get the plane in the air. Cars are driven by their wheels, an airplanes wheels just help it overcome ground resistence and inertia. Even planes without wheels - Seaplanes can take off either going with or against a current.

The Seaplane takes off because the thrust is greater than the drag of the water/current moving the plane forward to increase airflow for lift, correct ? Same with a boat moving upcurrent. The thrust is overpowering the drag. If the current were stronger than the thrust you'd not be able to go upstream (memories of a long paddle boat experience).

So if the thrust is unable to overpower the ground drag it wouldn't be able to move forward, correct?

[pdcorlis]

Of course, he's "The Kilted Flyer"


The Seaplane takes off because the thrust is greater than the drag of the water/current moving the plane forward to increase airflow for lift, correct ? Same with a boat moving upcurrent. The thrust is overpowering the drag. If the current were stronger than the thrust you'd not be able to go upstream (memories of a long paddle boat experience).

So if the thrust is unable to overpower the ground drag it wouldn't be able to move forward, correct?

Its not really drag its friction that has to be overcome - the airplane in this example is sitting on wheels and those wheels have bearings - so just how much friction or drag - if you must - do you think has to be overcome by the thrust? Put on a pair of roller blades - attach a rope to the wall and stand on a moving treadmill. You will be able to pull yourself forward with the rope with just a bit more effort than if you were standing on the floor.

By the way, if you want to see airplane propellers overcoming a moving conveyor belt - just drop by youtube. There are several examples there.

[Alaskan Kilted Guy]

I have taken off in a small aircraft, (Cessna 185 equiped with floats) from a swiftly moving river. Even going against the current, equivelent to going against the conveyor belt, the propeller was able to generate the thrust to overcome the current and gain enough speed to create lift. Same idea. People do it on floats all the time.

[hallmarktex]

But what you have done is generate enough thrust to overcome the movement of the river and also the necessary movement through the airstream. That's why you'll get off with less power going with the river but against the "wind". You must overcome the effects of momentum in order to move the airfoil through the airstream sufficiently to create lift.

If your river was moving along at 70 knots and you needed 70 knots of airspeed to have sufficient lift for flight, you would need your propeller to generate enough thrust to counteract the river and then also the movement through the air; 140 knots. The question is not can you overcome the forces in order to achieve flight but, rather, can you achieve flight if the surface the weight of the aircraft rests on moves back at the same rate your forward thrust moves you forward.

[Cage]

I have taken off in a small aircraft, (Cessna 185 equiped with floats) from a swiftly moving river. Even going against the current, equivelent to going against the conveyor belt, the propeller was able to generate the thrust to overcome the current and gain enough speed to create lift. Same idea. People do it on floats all the time.

Exactly. The thrust is overpowering the current and you are able to move forward to gain lift.
I think the object of the test is that the thrust of the airplane (engines) and the ground drag with the conveyor belt are the same.

At any rate, it wouldn't be the first time I've been wrong.

[demobud]

Does this hypothetical conveyor increase its speed relative to the thrust created by the planes engines? If that is the case, then we need to look at whether this action does cause air to move over the wing. If the craft cannot achieve forward motion it will not create enought lift to fly. If the air is static and the conveyor spins fast enough to keep the plane in the same spot, would there be lift? Also would prop vs jet have a difference? pusher vs puller?

[Robinhood]

Originally Posted by BonnieT100 View Post
I just want to point out that the aircraft would never get any air flowing over the wings until it's speed relative to the belt exceeds the belts speed relative to the airplane.

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This is not true.

The propeller or jet will push against the air around
the plane. This will cause the plane to move through the air.
The conveyor will have no effect on the engine's thrust. It only
pushes against the plane's wheels, and they turn freely like the
wheels on an skateboard. If the conveyor was like a walking
treadmill, the plane would simply move forward through the air
and right off the end of the conveyor no matter how fast the
conveyor was going. The conveyor is not pushing the plane back.
It is just spinning the wheels.

If the conveyor was many miles long the airplane still move
through the air. The conveyor still would not prevent the
airplane from moving through the air, since the wheels
would still turn freely. When the airplane moves through
the air fast enough it will lift off of the conveyor.

The liberal arts major says "What work should it do?"

[sdc]

African or European?

To the meat of the matter, if an aircraft needs to have a forward speed of 100 mph in order to fly, and the conveyor belt is moving it BACKWARDS at 100 mph, I believe the aircraft would have to attain a forward speed of 200 mph (relative to the conveyor belt) in order to fly, otherwise the wings wouldn't be generating enough lift.

[The Wizard of BC]

Yaish, You tried, and very well I might add, to explain the facts of aircraft flight. Some people just don't get it. And some never will.

sdc, You are absolutely correct. Conveyor speed = -100mph, Wheel speed = +200mph, Therefore aircraft airspeed = +100mph, FLIGHT!!!!!!!!!

So, can an unladen swallow's little tiny feets go 200mph? Can you say blisters? There for a 747 with 200 souls on board cannot be true and must be a digital enhanced pipe dream to make us believe that the Mythbusters is real science.

I am so glad Don Herbert died before this subject ever came up.

I shall now go to contemplate important subjects like "if Teflon is so non-stick how do they keep it stuck to the pan?"

[Mr. Kilt]

I shall now go to contemplate important subjects like "if Teflon is so non-stick how do they keep it stuck to the pan?"

That is a good question.
I also wonder about: If you have 24 odds 'n' ends sitting on a table and 23 of them fall off, what's left, an odd or an end?