Mythbusters to take on - PLANE ON A TREADMILL!!!

[NickH]

Some people, I think, misunderstand the question.

If you visualize a plane on an enlarged treadmill, but only long enough to fit the wheels of the airplane. Can the airplane build up speed, just as a car would, before taking off vertically?

No, of course not!

What us pilots see, is one huge treadmill the length of a runway, with the airplane accelerating along it for a normal take-off with the wheels spinning merrily away.

The debate is more about the nature of the question, rather than the answer.

 

[taseal]

It's already been discussed ad nauseum:

Stupid plane on a treadmill question
can the plane fly if...
airplane riddle (taken from another board)

I just wanted to point out that Mythbusters is finally going to tackle this question.

oh i'm sure.... its on every forum that speaks english lol

 

[taseal]

Some people, I think, misunderstand the question.

If you visualize a plane on an enlarged treadmill, but only long enough to fit the wheels of the airplane. Can the airplane build up speed, just as a car would, before taking off vertically?

No, of course not!

What us pilots see, is one huge treadmill the length of a runway, with the airplane accelerating along it for a normal take-off with the wheels spinning merrily away.

The debate is more about the nature of the question, rather than the answer.

yeah exactly..... it really depends how they perform the 'experiment'

but anyways, I thought all we needed was ground speed to take off?

 

[derg]

Aye yi yi. Even Charro could figure this one out but nooooOooOOOO!

 

[Fly4Pay]

The debate is more about the nature of the question, rather than the answer.

And Nick wins the $64,000 question!!! The entire debate is a red herring because of the way the "puzzle" is phrased. It presents an impossible situation since the way the treadmill is supposedly moving relative to the plane isn't grounded in reality. (treadmill speeds up at the same time plane moves forward--by the time the plane "moves forward", you're already behind, and therefore, can't DO it...)

This whole thing smells of the "what happens if an irresistible force meets an immovable object" silliness...

 

[Lefty]

All that happens is that the wheels rotate at twice their normal takeoff speed.

You could get into issues with bearings overheating, and an excess of rotational kinetic energy. But remember an airplane produces thrust with respect to the air and the wing produces lift with respect to the airflow.

The whole thing was to fool people that think airplanes work like cars where the engine drives the wheels.

btw I LOVE mythbusters

The wheels do not have to spin at twice their normal speed, what if the treadmill is only moving at 10 kts, then the wheels would only be travelling at 10 kts over liftoff airspeed....

 

[caliginousface]

The debate should not rest on whether or not the plane takes off while on a treadmill, but rather will the treadmill take off with an airplane inside it.

 

[OldTownPilot]

The wheels do not have to spin at twice their normal speed, what if the treadmill is only moving at 10 kts, then the wheels would only be travelling at 10 kts over liftoff airspeed....

.....and the belt is matching that speed in the opposite direction, .....

wheel speed = 2 X plane speed, only because of how the problem is worded.

But in other situations you are right.

 

[gevo]

ummm.. i dont think you can phrase the question in any way and make this complicated. The plane's speed is with respect to the atmoshpere, not the ground, not farmer john (as my dynamics professor would say)... so, if the atmosphere is the 'treadmill' part of this, where it accellerates to match the ground speed of the plane, then, AND ONLY THEN! will the plane not lift, becuase obviously there would be no airflow over the wings.. soooo.. unless mythbusters is after proving this, then this is a pointless non-myth myth.

perfect example! I was flying my RC trainer at my families Ranch, and it got really windy very quickly as soon as i took off the third time.. when i was doing ovals in the sky, i would have to open up to 3/4 throttle to stay aflot when i travelled in the same direction as the wind, else it would start to dive.. simply because the wind was high enough that the airspeed over the wings of the plane vs the speed of the plane itself were almost the same.. on the other hand, i landed it into the wind, ofcourse, and the darn thing was nearly floating! later on that day the wind 'gusts' were up to 70mph..

 

[skidz]

Mythbusters should try the wind tunnel myth

 

[Milesar]

Yes.... no...... well, yes it will... wait... no... yes! hold on, no I dont think so.... yes?no?yes?no?yes? ahhhhhhhhhhhhhhhh

{insert overly complicated reasoning here}

 

[gevo]

Mythbusters should try the wind tunnel myth

GENIUS!

while they're at it, they can try to proove that the Lambo Murc II has enough downforce at whatever given speed that it can drive upside down :-D!!!!
and the Koheness... owever you spell it
the Zonda
F450i.. so on... that would be an episode to watch!

 

[ORDinary]

How has that question "baffled pilots," as they claim? Airspeed 0 = no fly, no matter the wheel speed.

 

[tgrayson]

open up to 3/4 throttle to stay aflot when i travelled in the same direction as the wind, else it would start to dive.. simply because the wind was high enough that the airspeed over the wings of the plane vs the speed of the plane itself were almost the same

Steady wind has no aerodynamic effect on an airplane. If your a/c started to dive turning downwind, it would have to be due to some other effect, such as a steepening bank.

 

[gevo]

Steady wind has no aerodynamic effect on an airplane. If your a/c started to dive turning downwind, it would have to be due to some other effect, such as a steepening bank.

I believe it is for the reason as I described above, with wind the local atmosphere is moving, if the speed of the local atmosphere matches that of the ground speed of the plane, there will be no air flowing over the wings. Ex.. An observer from the ground will see the plane moving, but if there were someway to see a particle of the atmosphere, it would be moving at the same speed as the plane; meaning there is no air flowing over the wings.. you must go faster than the local atmosphere around the plane in order for lift on the wings... yes, hard to picture.. but this is the case.

Also, keep in mind that I am speaking about a scale aircraft, not travelling 100+ knotts, so it IS possible for the wind to catch up to it.

 

[tgrayson]

I believe it is for the reason as I described above

That's a great misconception. An airplane flying in a circle at 100 knots IAS will see 100 knots all the way around the circle. The ground speed with change with any wind, but that's irrelevant. This is a basic principle of physics.

The aircraft is maneuvering in a fluid which is moving at a constant velocity across the ground, but as far as the airplane is concerned, the fluid is at rest and the only speed "visible" to the airplane is the speed that it generates. This is why we don't perceive wind 600 knot wind produced by the rotation of the earth.

A steady wind cannot "catch up" to an airplane. We can take a C172 and fly it downwind inside the jet stream travelling at 150 knots, and the aircraft will still have an IAS of 120 knots, but it will be going 270 knots ground speed. By your logic, we'd have a -30 knots airspeed. Doesn't happen.

Only a change in wind (as in gust) can produce a change in our IAS, and it's temporary.

 

[moxiepilot]

the wheels of the bus go round and round, round and round, round and round....the wheels of the bus.....

 

[gevo]

That's a great misconception. An airplane flying in a circle at 100 knots IAS will see 100 knots all the way around the circle. The ground speed with change with any wind, but that's irrelevant. This is a basic principle of physics.

The aircraft is maneuvering in a fluid which is moving at a constant velocity across the ground, but as far as the airplane is concerned, the fluid is at rest and the only speed "visible" to the airplane is the speed that it generates. This is why we don't perceive wind 600 knot wind produced by the rotation of the earth.

A steady wind cannot "catch up" to an airplane. We can take a C172 and fly it downwind inside the jet stream travelling at 150 knots, and the aircraft will still have an IAS of 120 knots, but it will be going 270 knots ground speed. By your logic, we'd have a -30 knots airspeed. Doesn't happen.

Only a change in wind (as in gust) can produce a change in our IAS, and it's temporary.

MY FAULT!!! you are right, i wasn't taking into account that the airplane is producing its airspeed by pulling itself through the local atmosphere..
I guess what I explained would only go for gliders :-D

I feel dumb, Ishoulda caught that!!!! :banghead:

 

[gevo]

If an error is corrected whenever it is recognized as such, the path of error is the path of truth

--Hans Reichenback

hahah.. funny how your signature caught my eye at this very moment!

 

[tgrayson]

I guess what I explained would only go for gliders :-D

I should quit while I'm ahead. What I said goes for gliders as well, because they're also pulling themselves ahead through the air, but just using gravity to do so. However, their angle of descent with respect to the ground would steepen when the groundspeed decreases. The IAS would remain the same, because the airplane isn't aware of the groundspeed. If you were inside the airplane and couldn't see the ground, you'd have no way to know whether there was a wind or not.