Plane on conveyor belt

[HarvesteR]

Agreed.

The only real hindrance to the plane on the treadmill would be the added drag from the extra wheel friction, which would take only a small amount of thrust to overcome, leaving plenty of power for forward roll and takeoff.

Another eternal mystery solved by the Mythbusters 

Cheers

[TacitBlue]

I never understood why this was even a valid discussion. It seems so obvious to me that the airplane would still take off. To turn it around, imagine a stationary aircraft with a headwind of 70mph, it would try to lift off the ground, that's why we tie them down.

I've heard of people trying this with small R/C planes, and of course the planes took off. Unfortunately there were still people saying that it proves nothing because it wasn't a "real" airplane.

I am without cable and stuck with a slow internet connection, so I didn't get to see myth busters and can't watch the video. Did they actually use a real airplane and a huge conveyor belt?

[ApplePie]

I am without cable and stuck with a slow internet connection, so I didn't get to see myth busters and can't watch the video. Did they actually use a real airplane and a huge conveyor belt?

They used a tarp pulled by a truck as a conveyor belt. And a Rans S-5 as the airplane.




[edit]Also, it looked like the plane was going about 25-30 knots when it took off, if it matters.[/edit]

[TacitBlue]

Ah, thanks for the reply. Just from looking at the pic I would have guessed that the take-off speed of that airplane is about 30 - 35 knots. Neat looking little airplane too.

[DaveSims]

I guess I misunderstood what they were trying to do.  I thought the point was to use the plane's power to hold the aircraft still while the treadmill moved, in which case airspeed is zero and the plane won't fly.  If the point is that the airplane will fly regardless of ground speed, then true.

[ApplePie]

Here is the myth according to the video

If a manned airplane is on a conveyor belt, and both are going at the airplane's takeoff speed but in opposite directions, will the plane be held where it is or will it takeoff?

[DaveSims]

Here is the myth according to the video

If a manned airplane is on a conveyor belt, and both are going at the airplane's takeoff speed but in opposite directions, will the plane be held where it is or will it takeoff?

See, I take that to mean the airplane is moving (ground speed) the same speed as the conveyor belt, not that the aircraft is accelerating beyond the speed of the conveyor belt.  Which is why I say the aircraft will not takeoff, because airspeed is zero. 

[H]

The only difficulty I see in this is in regard to the (powered) plane's weight, thus friction (which has to be overcome by any object to move), on the conveyor belt; once that point is exceeded, the plane moves forward until lift-off velocity -- the conveyor belt can then go to as fast as it wishes while the plane passes wind above it. Actually, the movement of the conveyor belt might alleviate some of the initial friction.

8-)

[Jeff.Guo]

[quote]See, I take that to mean the airplane is moving (ground speed) the same speed as the conveyor belt, not that the aircraft is accelerating beyond the speed of the conveyor belt.

[Steve M]

You said it all earlier, Jeff.Guo, the aircraft is freewheeling.
An extreme example is yanking a table cloth out from under dishes. If the conveyor belt started suddenly the aircraft would not move untill mechanical friction takes presidence. (As H just said). To compensate for friction some throttle should be added to keep the aircraft stationary. Enough throttle applied cancels friction and begins foward movement no matter the speed of the conveyor belt.

[OVERLORD_CHRIS]

This same questioned was asked by another guy 2 years ago, but he specifically said jet aircraft, not crop duster like the one in Myth Busters, and he showed a Boeing 777.

And my response was: Maybe because:

Yes
A prop plane suck air towards the wings or over like in a C-130, and as long as you are giving it gas, it will pull it self through the air ultimately producing lift so it can take off. Witch is why they are used for short field take off's and landing's.

NO
Now A heavy turbofan powered wide body  on the other hand, like a 777 or A380, has to overcome its own weight first before it can start moving, once it does that it has to pick up enough speed so it generate lift for the wings to lift the weight off the ground. And if there is a conveyor belt then it will take alot of thrust to over come the backwards motion and keep it stationary, and then even more to brake free and get enough speed to lift off.

But as the 2nd test can not be accomplish, this is were the debate starts back up. 

[machineman9]

The wheels will spin twice as fast but the plane should still move forwards and thus take off.

[TacitBlue]

[quote]This same questioned was asked by another guy 2 years ago, but he specifically said jet aircraft, not crop duster like the one in Myth Busters, and he showed a Boeing 777.

And my response was: Maybe because:

Yes
A prop plane suck air towards the wings or over like in a C-130, and as long as you are giving it gas, it will pull it self through the air ultimately producing lift so it can take off. Witch is why they are used for short field take off's and landing's.

NO
Now A heavy turbofan powered wide body

[beaky]

[quote]This same questioned was asked by another guy 2 years ago, but he specifically said jet aircraft, not crop duster like the one in Myth Busters, and he showed a Boeing 777.

And my response was: Maybe because:

Yes
A prop plane suck air towards the wings or over like in a C-130, and as long as you are giving it gas, it will pull it self through the air ultimately producing lift so it can take off. Witch is why they are used for short field take off's and landing's.

NO
Now A heavy turbofan powered wide body

[DaveSims]

I don't disagree, the aircraft can accelerate and takeoff regardless of what the conveyor belt is doing.