Plane on a conveyor belt

[JacksonDean]

I'm 100% with you, if they can build a conveyor that can make the plane stay in place. That's the crux of the problem. Since the wheels are free-spinning and the propulsion comes from the prop (or jet engines), wheel bearing friction and a small amount of angular momentum are the only forces that the conveyor can exert to keep the plane from going forward, so it will require a conveyor belt that can accelerate almost indefinitely.

I think the guys on Mythbusters will fail to build a conveyor belt that can do this (if it can even be done at all, ever, by anyone, with an unlimited budget), and therefore their plane will move forward on the conveyor and take off. Like I said before, I think the whole problem either relies on a failed premise (that you can build a conveyor belt that makes it stay in place), or was a trick question.

Out of curiosity (and not animosity! ) did you watch the video/trailer? I believe they plan to make a conveyor out of something and pull it behind a truck.

Of course, this is far from infinite, I realize. They also look like their using a plane that needs a minimal speed for take off, probably around 45-55 KIAS, so it appears that the truck pulling the conveyor will actually be able to match the necessary backwards force/speed... whichever it is. ( Forty five - 55 KIAS is about 52 - 64 mph ).

[Bengal]

It's a 3000 foot tarp that they are going to park the plane on. That's the belt they are using. Not a belt at all. Just a long tarp pulled under the wheels of the plane from a truck heading the oposite way...

The test itself, along with the question, is failed. I think...

[dg]

Out of curiosity (and not animosity! ) did you watch the video/trailer? I believe they plan to make a conveyor out of something and pull it behind a truck.

Of course, this is far from infinite, I realize. They also look like their using a plane that needs a minimal speed for take off, probably around 45-55 KIAS, so it appears that the truck pulling the conveyor will actually be able to match the necessary backwards force/speed... whichever it is. ( Forty five - 55 KIAS is about 52 - 64 mph ).

Yeah, I did check out the trailer. One of the reasons I think it's going to fly was when one of the guys said, "We know how fast the plane needs to go, so ..." The problem with that is it that sounds like he thinks all he needs to do is set the conveyor to reach that particular speed. It's going to have to go a heck of a lot faster than that (let alone keep on accelerating continuously) to keep the plane standing still.

[SeventhSon]

The original brain teaser asked whether IF you could pull the tarp (or run the conveyor belt) at a speed exactly EQUAL to the forward ground speed that the jet/prop plane needs to reach to achieve lift, would you prevent the jet/prop plane from taking off.

The answer is that at that SPEED, the backwards FORCE you are imparting on the plane is hardly significant to negate the forwards FORCE generated by the jet/prop.

Where most people (including myself at first...yes, i was a doubting thomas!) make the mistake is in thinking that the conveyor belt (or tarp) moving at that backwards speed somehow makes the forward speed of the plane equal 0, which is not the case at all.

[Axewielder]

Four pages of Mythbusters talk, and not one mention of that hot redhead Kari. Am in still in the JCF, or did I wander into the J.R.R. Tolkien forums?!?

[RobRR]

Tell me where to put my money... that fucker IS taking off! Its simple laws of physics that Im guessing most people just dont understand. Let me maybe try it this way:

Say you are in a swimming pool. A conveyor belt is on the bottom of the pool. You start walking on the conveyor belt, underwater. You stay in the same place. Then you take your arms and start paddling, and you start moving forward.

Your arms = the planes jet engines. They will move you forward. As long as your legs can keep up, you can go as fast as you can paddle.

[slayer32390]

Say you are in a swimming pool. A conveyor belt is on the bottom of the pool. You start walking on the conveyor belt, underwater. You stay in the same place. Then you take your arms and start paddling, and you start moving forward.

Your arms = the planes jet engines. They will move you forward. As long as your legs can keep up, you can go as fast as you can paddle.

Or you can just swim to the other side of the pool I'm not here to argue but for the record i put my money on the not taking flight side

[LouSiffer]

The original scenario was that if you put a plane on a conveyor belt ith the jets set to "take off thrust" with the belt moving in the opposite direction, will the plane take off or will it just sit there motionless.

It will take off as the wheels are a neutral way to remove friction allowing the plane to leave the ground easier.

If a plane could not do this, then no plane could possiblely fly taking off the ground on a East to West direction since the earth is rotating at 3600 miler per hour.-Lou

[finnman]

won't work.

You need relative wind across the wing for lift.

In the case of an aircraft wing, pressure regions turn the passing flow of air downward towards the ground. These pressure regions exert an equal and opposite force on the wing, called lift, that supports the aircraft in the air.
The lift generated by an airfoil depends on such factors as the speed of the airflow, the density of the air, the total area of the airfoil, and the angle of attack.

[JACKSONFREAK]

no

If this was possible, then vertical takeoff planes would have been much easier to design, & we would've had them 60 or 70 years ago.

does the Hawker Harier ring a bell? if my time line is right it was developed at the end of WWII but scraped due to expense in non war time. But then redisenged with jet engines later and became the Corsair II. during Vietnam. But like i said my time line may be a bit off. It may not be 70 years ago but. It is at least 40 years.

[Stinkbug]

As others have said the wings will not generate lift standing still. Thus, the plane won't fly. It is possible that the prop wash could generate some life, but it is unlikely that it would be enough for most real planes to fly.

[toejam]

What happens if it lands in water; will it float? :ROTF:

Of course it will goofy, the forward thrust from the engines, along with the upward push of the air in the wheels (unless they are still spinning backwards from the conveyor) will push it up AND propel it forward, which eventually will even lead to dry land :ROTF:. The downside of course is if the dippy pilot reversed thrusters and lowered tire air pressure to compensate for the conveyors actions..in which case it will sink like a rock.

so, I've had a beer or twelve...

Good answer. Beer makes everything make sense. :ROTF:

[guitarsjb]

glad you understood that

[Bert]

As others have said the wings will not generate lift standing still.

Who says the plane will be standing still? The conveyor belt does not impose any significant backwards force to keep the plane from moving forward. Plane moves forward & flies.

I can't believe we're discussing this *again* :ROTF:.

[El_Kabong]

This video is stupid. There are no nekkid chix.