Mythbusters Episode

[binaryterror]

Why is this shocking to anyone?

The ground has nothing to do with any characteristic of flying its all about wind/thrust/lift/loft.

[JeremyH]

Originally Posted by binaryterror

Why is this shocking to anyone?

The ground has nothing to do with any characteristic of flying its all about wind/thrust/lift/loft.

I dont think the concept of flight is the confusing aspect....I think that the introduction of the treadmill is what does it...that and the difference between a car and a plane. At least for me it was.

When people think of a treadmill they think of a person running on it (friction is overcome with the use of the feet and legs) and a car is quite similar.

[Rocksmith Eng.]

I caught it, even the pilot said it wasnt gonna take off. But lo and behold it did. The prop is what provides propulsion, not the wheels. So it didnt matter how fast the conveyor was moving, the plane would still take off.

[JamboreeTJ]

Originally Posted by JeremyH

I dont think the concept of flight is the confusing aspect....I think that the introduction of the treadmill is what does it...that and the difference between a car and a plane. At least for me it was.



When people think of a treadmill they think of a person running on it (friction is overcome with the use of the feet and legs) and a car is quite similar.

I think that's right. We're all familiar with the treadmill, but in a very different sense. Running or walking or maybe driving an R/C car on one. Despite the simple principles, it wasn't documented that anyone had actually done the experiment in real life. Not that it was completely necessary, but it made for a good 20 minutes of TV.

I like the comment on the NAXJA thread about seaplanes getting traction on water. Hey! New myth! If a seaplane is on a river pointed upstream, and the river flow speed is equal to the takeoff speed, will the seaplane take off?

[thatguy]

like most myths they screwed it up and proved nothing.

[2JSC]

But if the plane isn't moving, how is it gaining lift? The motor is there to pull the plane along so that the wings gain lift. But if the plan is stationary(as anything would be moving on a treadmill) how is it gaining lift?

Sorry, but this is still really confusing to me... or are you guys making it confusing?

When I watched the episode, it still looked like the plane was going forward when it took off.

[JeremyH]

Originally Posted by 2JSC

But if the plane isn't moving, how is it gaining lift?

That's the confusing part....the plane will move...and in the opposite direction of the air that it is pushing. The wheels will do what they want to WRT the ground/conveyor....
The "frictionless" bearings in the wheels seperate the engines of the plane from the conveyor.

[microgoat]

The plane doesn't have to move horizontally.

As long as the prop is pulling or pushing air over the wings, it'll lift.

I once flew in an old Aeronca Champ, underpowered little thing. The pilot used to get a kick out of throttling back to just over stall speed in a headwind, and fly backwards

[JamboreeTJ]

Originally Posted by microgoat

I once flew in an old Aeronca Champ, underpowered little thing. The pilot used to get a kick out of throttling back to just over stall speed in a headwind, and fly backwards

I could just about do that in a Schweizer 1-26 sailplane I used to fly. No motor/prop. In fact, it was just about impossible to have any groundspeed flying into a headwind unless you had the nose pointed at the ground.

[JeremyH]

Originally Posted by microgoat

As long as the prop is pulling or pushing air over the wings, it'll lift.

It was my understanding that the propeller does not move air over the wings, but simply provides thrust which moves the plane through the air creating the necessary lift. If your statement were true, then a jet would not fly.

[Mr. Chevy]

Originally Posted by JeremyH

It was my understanding that the propeller does not move air over the wings, but simply provides thrust which moves the plane through the air creating the necessary lift. If your statement were true, then a jet would not fly.

You are right the prop doesn't push air over the wings at all it just provides thrust to move the plane threw the air.

[microgoat]

One way or another, if air flows over the wings fast enough, the thing will fly. Doesn't matter if the prop does it, or the wind, or a wet fart.

In an ultralight like they tested, the prop moves plenty of air over the wings. Anything much larger and it acts as a thrust agent.

[Mad Scientist]

As stated above, an airplane's wings do not rely on the prop to move air over them to provide lift. All the propellor does is drive the entire craft forward. The wings then achieve lift as a result of being driven through the surrounding air. That is how a toy glider can fly with no engine - they get the forward thrust by being thrown. Or take a full-size tow-behind glider as another example - The airplane that tows the glider provides the forward motion, and it is the forward motion through the air that gives the glider's wings lift.

[RedNeck Rc]

Now in a Torque Roll or Harrier on a rc plane the propeller just moves air across the wings and no lift. It just has enough power or pull to counteract the weight of gravity and prop hang. I would have tried an auto gyro for this myth, it would just be cool.

[slobin3d]

it doesn't matter if the conveyor is going 10 or 1000mph if the engine/jet is running the plane will take off, all the engine has to do is over come the extra friction of the tires spinning and all else is normal as far as the plane is concerned.

the part that gets people is that they assume that because the conveyor is moving at X speed that the prop has to spin like normal to overcome that speed like a car would. In actuality to get the plane to stay stationary on the moving mat you would have to slow the motor down to an Idle or less, just enough to overcome the extra friction on the wheel bearings

[JeremyH]

Originally Posted by RedNeck Rc

Torque Roll or Harrier

That is a completely different ball game...

[BJoe]

Originally Posted by 2JSC

But if the plane isn't moving, how is it gaining lift? The motor is there to pull the plane along so that the wings gain lift. But if the plan is stationary(as anything would be moving on a treadmill) how is it gaining lift?

Sorry, but this is still really confusing to me... or are you guys making it confusing?

When I watched the episode, it still looked like the plane was going forward when it took off.

In cases like that and if the plane and the tarp are going 25mph in opposite directions the wheels on the plane will be spinning at a 50mph "wheel speed", which would only have an affect if the wheel bearing are in bad shape and won't spin freely. As long as the plane is moving forward fast enough (which it was) and/or have enough head wind to create required lift, it will fly. Now I would be curious if any "wind" created by the rearward movement of that tarp/belt/whatever would be enough to aid in the wings ability to lift the plane off the ground in a shorter distance..............

As for jets and ducted fans, I think the saying "Given sufficiant thrust, even pigs will fly." would apply in that situation

Now I don't know about the rest of you guys, but I find it absolutely frightening that there are people licensed to fly airplane that believed that myth

[JeremyH]

Originally Posted by BJoe

As long as the plane is moving forward fast enough (which it was) and/or have enough head wind to create required lift, it will fly.

That was the main question here....whether or not the plane will move forward....or, at least, that is what I found difficult to prove to myself.

Originally Posted by BJoe

Now I don't know about the rest of you guys, but I find it absolutely frightening that there are people licensed to fly airplane that believed that myth

There are plenty of people who have a driver's license who have no clue how to even change a tire, let alone how their vehicle interacts with the earth's surface and allows it to move.

[BJoe]

Sad but true on that last one, I one time had somebody return a slot car set to the Toy's "R" Us I worked at because the cars would fly off the track in corners. As I put the refund through the register I nicely suggested slowing down for corners was what always worked for me. After about 30 seconds of silence he somewhat gruffly told me, Well they should have fixed that problem by now!"
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Unforunetly his oldest kid is probably about driving age by now, please pray for who ever has to share the road with that kid

[kris]

I was going to bump this thread with this: flipoff:

Will it take off