Manual page 62 :(

[Kianoni]

Instead, here’s a quick test to determine whether you should read this chapter.
If you’ve been on the internet in the past ten years, I’m sure you’ve heard this
riddle. There’s a plane on a magical threadmill runway. The threadmill defies
the laws of physics and can rotate as fast as the plane’s wheels while going
in the opposite direction. If the plane rolls forward at 10 mph, the runway
underneath rolls backwards at 10 mph. The plane’s wheels spin up to 200 mph
and the runway rolls back at 200 mph. The question is, will the plane move
forward and take off or remain stationary?
If you had to think about it for even a second, you need to read this chapter.
The answer of course is yes, the plane will take off as normal.

WTF :confused: :grin:

..and if you didn't get it then think.

http://www.scribd.com/doc/51503478/IL2CoD-MANUAL-UK

[Kianoni]

now I didn't read it correctly before postin :D

[DD_crash]

Sounds like it was written by RAAAID :)

[PeterPanPan]

This really jarred with me too. I have re-read it many times and I still don't get it. Surely if the plane's speed over the ground is 'x' and the runway is moving at 'minus x', the aircraft's position is stationary. If so, how can there be any airflow over the wing. Surely the aircraft cannot fly?

Can someone please explain to me why I am wrong?

[Biggs]

This really jarred with me too. I have re-read it many times and I still don't get it. Surely if the plane's speed over the ground is 'x' and the runway is moving at 'minus x', the aircraft's position is stationary. If so, how can there be any airflow over the wing. Surely the aircraft cannot fly?

Can someone please explain to me why I am wrong?

if u read the rest of that section of the manual it explains it... the engine and propeller pull the plane... the plane will accelerate down the "conveyor belt" as though it was a normal runway.

the contact with the ground as no impact on the speed of the plane on takeoff.

[norulz]

Rotfl

[addman]

This really jarred with me too. I have re-read it many times and I still don't get it. Surely if the plane's speed over the ground is 'x' and the runway is moving at 'minus x', the aircraft's position is stationary. If so, how can there be any airflow over the wing. Surely the aircraft cannot fly?

Can someone please explain to me why I am wrong?

Well, the propeller drags the plane forward and pushes air along the plane and that's why it lifts right? Anyone who have flown a RC airplane should know this at least.

[major_setback]

This was a very much discussed topic a couple of years ago at the UBI forums.


Mythbusters addressed it too:

http://www.google.se/#q=mythbusters+plane+on+a+conveyor+belt&hl=sv&safe=off&prmd=ivns&source=univ&tbm=vid&tbo=u&sa=X&ei=wyWOTbumN8PMswbV1YyBCg&ved=0CC0QqwQ&fp=3ebf0d08cabcd111



The wheels have no drive! They will freely roll if the prop pulls the aircraft through the air, no matter what direction the ground is moving.

.

[Alien]

Instead, here’s a quick test to determine whether you should read this chapter.
If you’ve been on the internet in the past ten years, I’m sure you’ve heard this
riddle. There’s a plane on a magical threadmill runway. The threadmill defies
the laws of physics and can rotate as fast as the plane’s wheels while going
in the opposite direction. If the plane rolls forward at 10 mph, the runway
underneath rolls backwards at 10 mph. The plane’s wheels spin up to 200 mph
and the runway rolls back at 200 mph. The question is, will the plane move
forward and take off or remain stationary?
If you had to think about it for even a second, you need to read this chapter.
The answer of course is yes, the plane will take off as normal.

No, because plane flies when WIND is moving under and above WINGS. Wheels are just to protect propeller from the ground impact.

[BadAim]

It's a joke guys, it's just a joke.

[Space Communist]

ahaha That's awesome that they included that old chestnut. That problem has been argued about for years and years. I swear physics majors have written PH. D's on it. Anyway yes it will take of as normal if you assume the wheel's bearings are frictionless. If they are not frictionless it becomes more complicated, and becomes a balancing act between opposing forces. Even then it would likely take off unless the wheels seized from internal friction, since they would be rotating much faster than they normally would. I am no expert on landing gear design but i suspect they have a lot of lee-way.

[Tomahawko]

Instead, here’s a quick test to determine whether you should read this chapter.
If you’ve been on the internet in the past ten years, I’m sure you’ve heard this
riddle. There’s a plane on a magical threadmill runway. The threadmill defies
the laws of physics and can rotate as fast as the plane’s wheels while going
in the opposite direction. If the plane rolls forward at 10 mph, the runway
underneath rolls backwards at 10 mph. The plane’s wheels spin up to 200 mph
and the runway rolls back at 200 mph. The question is, will the plane move
forward and take off or remain stationary?
If you had to think about it for even a second, you need to read this chapter.
The answer of course is yes, the plane will take off as normal.

The reason it is so confusing is because they don't talk about the plane creating thrust. They only state that the wheels are spinning at 200mph and the 'magic' conveyor is moving in reverse at 200mph. In that sense the plane would stand still.

So they are INCORRECT. As far as I can tell.

If the wheels are spinning 400mph forward and the conveyor is moving in reverse at 200mph then the plane is moving forward at 200mph.

See the discrepancy?

The only way they can make the wheels and the conveyor spin at the same rate, while creating lift, would be if the entire conveyor system was maintaining lateral position with the plane.

[BigPickle]

The aircraft would loose an undercarrage leg and vere wildly out of control and flip upside down trapping the pilot inside the burning wreck..... why?

Because the the tires would burst and shred traveling at 400mph :-P

[choctaw111]

The only thing that will happen is the wheels will be spinning at 2x the speed at takeoff.
If the plane can take off at 80mph, then the wheels will be spinning at revolutions for 160mph.
As long as the wheel and tires can handle it, the plane will take off like nothing is happening.

[Tomahawko]

The aircraft would loose an undercarrage leg and vere wildly out of control and flip upside down trapping the pilot inside the burning wreck..... why?

Because the the tires would burst and shred traveling at 400mph

Touché salesman!
Lucky me, I begin with the hypothetical 'if' :grin:

The funny thing is now they have all of these manuals with this statement
If you had to think about it for even a second, you need to read this chapter.

[DoolittleRaider]

The way I see it:

As noted previously, the aircraft wheels have no "Drive"...they are irrelevant to the forward progress of the aircraft 'on the ground'. If the aircraft thrust is 'equivalent' to 200MPH, it will take off at it's normal rotate point/speed. The Wheels will be spinning/rotating (furiously) at twice their normal 'speed'...but, again, irrelevant to the aircraft's taking off.

Now, with an Automobile, the wheels are Essential because they are transferring the engine drive(thrust, if you will) to the ground and the car thus rolls forward along the ground surface. Thus, the forward progress of the wheels along the ground moves the rest of the car (Chassis) forward. If no wheel rotation 'forward', no movement of the car.

Think of a Drag race start, or pre-start. When the wheels are spinning but not gripping, you get a lot of burning rubber but no forward progress. Think "traction".

So, if the auto on the treadmill surface is turning its wheels with instantaneous point-of-contact traction at the 'equivalent' of 200MPH...but that point of contact of the treadmill surface is moving at 200MPH in the opposite direction...the Auto will not move forward. (There might be a nasty smell of burning rubber or fire)

[Letum]

ok...here is the confusion.....


If the conveyor is moving back at the same speed that the plane is moving forward, then the plane will take off as normal. (assuming the wheels can withstand 2x takeoff speed.)
The events look like this:

1) Throttle is applied
2) Plane moves foward
3) Conveyor moves at speed of plane
4) Wheels spin at twice the speed of the plane
5) Plane continues to accelerate and take off


If the conveyor is moving back at the same speed that the plane's wheels are moving forward, then a loops forms. The loop looks like this:

1) Throttle is applied
2) Wheels move forward
3) Conveyor moves at speed of wheels
4) As before, the wheels must move twice as fast as the conveyor for the plane to move forward, so the wheels speed up
5) Conveyor speeds up to speed of wheels
7) As before, the wheels must move twice as fast as the conveyor for the plane to move forward, so the wheels speed up
8 ) Conveyor speeds up to speed of wheels
9) As before, the wheels must move twice as fast as the conveyor for the plane to move forward, so the wheels speed up
10) Conveyor speeds up to speed of wheels

This theoretically continues until friction breaks the wheel bearings. This will happen instantly because the wheels will (theoretically) instantly try to achieve an infinite rate of spin.
This is happening because for a plane to move up a conveyor moving at 100mph, it's wheels must move at 200mph, but if the conveyor is matching the speed of the wheels, the wheels can never double the speed of the conveyor, but the wheels must travel at twice the speed of the conveyor for the plane to move forward. All the energy of the plane's forward thrust is used in the friction of the wheel bearings. Even with perfect, zero friction, bearings that don't burn out, you will just get infinite wheel spin speed.
That's hard to understand because we never see any kind of system like that in the real world. It's not possible.

The riddle should read:


"There’s a plane on a magical threadmill runway. The threadmill defies
the laws of physics and can rotate as fast as the plane [CUT] is moving
in the opposite direction. If the plane rolls forward at 10 mph, the runway
underneath rolls backwards at 10 mph. The plane [CUT] moves up to 200 mph
and the runway rolls back at 200 mph. The question is, will the plane move
forward and take off or remain stationary?
If you had to think about it for even a second, you need to read this chapter.
The answer of course is yes, the plane will take off as normal."

The problem is that this isn't much of a riddle as it tells us that the plane is moving at 200mph.

[Tomahawko]

"There’s a plane on a magical threadmill runway. The threadmill defies
the laws of physics and can rotate as fast as the plane [CUT] is moving
in the opposite direction. If the plane rolls forward at 10 mph, the runway
underneath rolls backwards at 10 mph. The plane’s wheels spin up to 200 mph
and the runway rolls back at 200 mph. The question is, will the plane move
forward and take off or remain stationary?
If you had to think about it for even a second, you need to read this chapter.
The answer of course is yes, the plane will take off as normal."

You still need to get away from "The plane's wheels spin up to 200 mph." Stick with "The plane move's forward 200 mph."
Theoretically speaking, I can make a wheel spin however fast I want. That doesn't mean the wheel itself is moving forward which is necessary when dealing with a plane. A plane needs the airflow under/over the wing to create lift. Without that it's hogwash.

[Letum]

You still need to get away from "The plane's wheels spin up to 200 mph." Stick with "The plane move's forward 200 mph."
Theoretically speaking, I can make a wheel spin however fast I want. That doesn't mean the wheel itself is moving forward which is necessary when dealing with a plane. A plane needs the airflow under/over the wing to create lift. Without that it's hogwash.


ed: yup, your right. My post will be edited.

[Tomahawko]

A better riddle would be:

If you put a magical frictionless plane in a wind tunnel where the plane moves neither forward or backward will it fly?

Something along those lines, as I didn't think through all the facets.

EDIT: Or skip the magic and attach a string.

[Letum]

If you put a magical frictionless plane in a wind tunnel where the plane moves neither forward or backward will it fly?
.

Haha! Concise!

[Kianoni]

yup precisely, the wording on the riddle is very badly put considering that the magic conveyor belt has nothing to do with the air around the plane. a much more logical question would be "if a plane sits on a runway and the wind is blowing at the speed that is required for the plane to take of.." but even that requires thinking. maybe it would have been easier to explain that groundspeed has nothing to do with lift, but take or leave - even I can be fooled by words and stumble on my own.