[Ed Dantes]

From the New York Times:

As an instrument-rated, commercial licensed pilot, I’ll go out on a limb and say that the plane will not take off, as long as the airplane is motionless with respect to the air. Airflow over the wings create the necessary lift to overcome the force of gravity. Now if you had giant fans blowing over the wings in this situation, you might be able to generate enough airflow to exceed the stall speed of the wings, thus generating lift. However, once the airplane climbed out of the fan-generated wind, you would have the mother of all wind shears, the airflow over the wings would quickly drop below stall speed, and the plane would hit the deck hard.

With regard to the comment that if the engines produce thrust, the plane will take off, ignores the fact that pilots can hold the brakes, spool up the engines, and not fly. Also, on takeoff, the engines are producing maximum thrust, but until the airplane accelerates to an AIRSPEED that exceeds the stall speed, the airplane will not fly.

— Posted by Norm Cohen


The plane can’t take off.
I was Chaplain in the Portuguese Air Force, and had long talks about flight with the best pilots of the world.
Any pilot know that the most important thing is airspeed, and the pressure diferences above and below the wing.
In the treadmill the thrust of the propeller or the jet engine only compensates the velocity os the treadmill, the air aroud tha plane is static, so it can’t generates lift.
Tha air speed is so important in aviation, that when a plane takes off, it does so always agains the wind direction and when it’s fliing we measure the air-speed and not the plane speed

[olldflame]

That's not the case though. In the case of your jet pictured above, the engines on the tail are pushing the plane forward. Lets assume for a second that you start out on sold ground. As soon as the plane crosses over onto the moving treadmill, the plane will continue to move forward at that same rate but the wheels on the tread will now move twice as fast. The ground movement doesn't affect the engines pushing it.

I concurr. Since the wheels of the plane are not powered, but free-spinning, they would simply turn faster when the treadmill is moving in the other direction, and the force of the engine would continue to move the plane forward at almost exactly the same speed as on solid ground. Friction will have some effect, but not a lot.

[LUconn]

The net force of a plane going forward and the conveyor belt going backward is zeroed out. At that point, you're left with a plane on runway, not going anywhere. Those don't fly, you know.

I understand that portion of aviation. But I don't think that the plane would be at a stand still. It would continue to be thrust forward as if there wasn't a conveyor belt there. Think of you pushing a matchbox car on a solid floor using constant force. Now if you pushed it on a treadmill with that same force would it be going any slower? No. The wheels may be spinning twice as fast as a result of the treadmill, but the speed of that car would still be the same.

[Ed Dantes]

The net force of a plane going forward and the conveyor belt going backward is zeroed out. At that point, you're left with a plane on runway, not going anywhere. Those don't fly, you know.

I understand that portion of aviation. But I don't think that the plane would be at a stand still. It would continue to be thrust forward as if there wasn't a conveyor belt there. Think of you pushing a matchbox car on a solid floor using constant force. Now if you pushed it on a treadmill with that same force would it be going any slower? No. The wheels may be spinning twice as fast as a result of the treadmill, but the speed of that car would still be the same.

I think I know where we differ.

- You say that the plane can't be a stand-still because of thrust and all that fun stuff.
- I say that a plane at a stand-still won't fly.

Do I have this right at least?

[LUconn]

From the New York Times:


With regard to the comment that if the engines produce thrust, the plane will take off, ignores the fact that pilots can hold the brakes, spool up the engines, and not fly. Also, on takeoff, the engines are producing maximum thrust, but until the airplane accelerates to an AIRSPEED that exceeds the stall speed, the airplane will not fly.

— Posted by Norm Cohen

I hate that you're making me argue with a pilot. But if he's talking about the brakes on the wheel, then it's obvious the plane won't go anywhere. That's like trying to take off with no wheels at all. Too much friction, and obviously if the wheels aren't turning than there is also too much friction. If he's talking about airbrakes, well than I don't really know. I think those just create drag but I don't see what that has to do with this.

[LUconn]

The net force of a plane going forward and the conveyor belt going backward is zeroed out. At that point, you're left with a plane on runway, not going anywhere. Those don't fly, you know.

I understand that portion of aviation. But I don't think that the plane would be at a stand still. It would continue to be thrust forward as if there wasn't a conveyor belt there. Think of you pushing a matchbox car on a solid floor using constant force. Now if you pushed it on a treadmill with that same force would it be going any slower? No. The wheels may be spinning twice as fast as a result of the treadmill, but the speed of that car would still be the same.

I think I know where we differ.

- You say that the plane can't be a stand-still because of thrust and all that fun stuff.
- I say that a plane at a stand-still won't fly.

Do I have this right at least?

That is exactly right. I agree with you that a plane at a stand still will not fly. But I think that it would be moving forward in this case.

[Ed Dantes]

- You say that the plane can't be a stand-still because of thrust and all that fun stuff.
- I say that a plane at a stand-still won't fly.

Do I have this right at least?

That is exactly right. I agree with you that a plane at a stand still will not fly. But I think that it would be moving forward in this case.

Oh. I'm arguing the second point, the one we both agree on. The first one -- I figured that the conveyor belt aspect to the question was a way of saying that the plane has no net movement.

[RubberMallet]

uh...no. a planes engines don't lift the plane in the air. air moving over the plane is the only thing doing this....in relation to the ground, the plane would be either not moving at all or going backwards.

our cirrus needs to have 70 knots of air moving over it to take off...

[LUconn]

did you even read anything else in this thread or did you think you were too good for that?

[adam42381]

It'd be limper than that Red Sox poster on prom night.

Of course I went to a Christian school where we didn't have prom. We had a "junior/senior banquet" with some good old fire and brimstone preaching...

[RubberMallet]

did you even read anything else in this thread or did you think you were too good for that?

i just called my instructor....it would take off...

if this were a car what ed and i had said would be true...the problem is that the wheels move independantly of the engine. the engine is fighting air...and will go the same speed regardless of technically what the wheels are doing....the wheels are just the means to which hold the plane up..

so i was wrong..

[Fumblerooskies]

I guess we will see on next week's Mythbusters.

[olldflame]

At the risk of getting side tracked, but also hopefully illustrative, imagine this is a seaplane, and instead of a conveyer, you are going against a rapid current. Because the floats of the seaplane are in the water, which causes a huge amount of resistance, the plane would need to overcome the speed and resistance of the current in order to achieve the air speed needed to take off. With the original scenario, the free spinning wheels of the plane on the conveyer have almost no resistance, and would simply turn faster, but allow the plane to go forward at essentially the same speed as it would on solid ground.

[kel varson]

I guess we will see on next week's Mythbusters.

Yes, I'm confused but I think mythtbusters will clear this up. I will be sure and tape. Anyone have the time and day for that episode. I know it is the 30th.

Since Ed is a genius I am going to say he is correct.

[adam42381]

The schedule I posted earlier, http://dsc.discovery.com/tv-schedules/s ... x&start=10 , shows that it airs January 30th at 9pm.

[Ed Dantes]

I guess we will see on next week's Mythbusters.

Yes, I'm confused but I think mythtbusters will clear this up. I will be sure and tape. Anyone have the time and day for that episode. I know it is the 30th.

Since Ed is a genius I am going to say he is correct.

Yeah, but I have a feeling I'm going to be wrong on this because I was focusing on the wrong aspect of the question.

[RubberMallet]

I guess we will see on next week's Mythbusters.

Yes, I'm confused but I think mythtbusters will clear this up. I will be sure and tape. Anyone have the time and day for that episode. I know it is the 30th.

Since Ed is a genius I am going to say he is correct.

Yeah, but I have a feeling I'm going to be wrong on this because I was focusing on the wrong aspect of the question.

as was i initially...its not can a plane take off with no air pushing against it, its will the plane still go forward...

[LUconn]

So, it was busted last night. The plane did indeed take off. What's hilarious is on the messageboard I first read this on, and even the discovery mythbuster's board the majority of people still claim that it should not be taking off and that they must have done it wrong. They even took the time to explain the physics behind why this works.

[Fumblerooskies]

They did it wrong. The MYTH is the plane being STATIONARY on the treadmill. If you watched the show last night...the plane was simply moving in the opposite direction....thus moving FORWARD creating increased lift on the wings. I think this is one the Mythbusters will get a ton of mail on and have to revisit in a later episode.

[LUconn]

are you serious? Why would the plane stationary?? That's the myth!

[RagingTireFire]

are you serious? Why would the plane stationary??

No, the myth is that the treadmill is moving fast enough to keep the plane stationary against its engines. In this case, the plane's engines were moving the plane forward faster than the treadmill was moving against it. They did it wrong. Myth NOT busted!

[LUconn]

are you serious? Why would the plane stationary??

No, the myth is that the treadmill is moving fast enough to keep the plane stationary against its engines. In this case, the plane's engines were moving the plane forward faster than the treadmill was moving against it. They did it wrong. Myth NOT busted!

The plane will never never never never never be stationary on a moving treadmill. It will either be moving backwards, because the plane is not powered up, or it will be moving forward because it is powered up. The plane can be powered to go however slow and the conveyor belt can be going however fast and unless the wheel bearings melt together the plane will always go forward.

[RagingTireFire]

are you serious? Why would the plane stationary??

No, the myth is that the treadmill is moving fast enough to keep the plane stationary against its engines. In this case, the plane's engines were moving the plane forward faster than the treadmill was moving against it. They did it wrong. Myth NOT busted!

The plane will never never never never never be stationary on a moving treadmill. It will either be moving backwards, because the plane is not powered up, or it will be moving forward because it is powered up. The plane can be powered to go however slow and the conveyor belt can be going however fast and unless the wheel bearings melt together the plane will always go forward.

That's a completely different premise. The premise of the myth is that the plane and the treadmill are moving at the same speed in opposite directions. If the Mythbusters aren't going to bother replicating that then they haven't actually tested anything.

[LUconn]

You're either just trying to annoy me by arguing, which is your style, or I don't believe that you ever graduated from college. Did you even watch the show?

[RagingTireFire]

You're either just trying to annoy me by arguing, which is your style,

Pot, kettle. Kettle, pot. I thought pointless argument was the entire point of a thread entitled "Let's Argue Over This".

Either way, I'm right.