will it take off?

[hosejockey2002]

If this conveyor belt is moving backwards at 60 mph, friction between the belt and the tires of the plane will move the plane backwards at 60 mph. It will take the same thrust to keep the plane from moving backwards as it would take to move the air plane forward at 60 mph on a non-moving runway.

That's only if the wheels were locked. Since they will spin freely, there will be much less friction. The plane will move backwards, but not at anywhere near 60 mph, because an object at rest tends to stay at rest. The thrust from the planes engines would overcome that inertia and the plane would accelerate. The key here is that that thrust from the engines propel the plane, not torque from the wheels.

To move forward the thrust would have to increase beyond that point. What's your ground speed when your indicated airspeed is 120 mph and you are into a 60 mph headwind. How about your ground speed with the same ISA of 120 mph and a tailwind of 60 mph?
If you find that moving runway, I'm taking all bets and then getting myself that new tactor!

The plane doesn't care at all what the ground speed is. It's airspeed that makes it fly. Now, if you could throw in a tailwind that increased at the same rate as the conveyor belt, then you would have a really tough time getting that plane off the ground.

 

[ovrszd]

Sense we were having so much fun debating the finner points of tire pressure in the other thread....

i thought this would be kinda fun...

a plane is standing on a movable runway( something like a conveyor).as the plane moves the conveyor moves but in the opposite direction.the conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction.

the question is

will the plane take off or not?

(ps its been debated to death on other forums, its always fun to see how people present the theory behind there answer)

Now this is funny!!!! And I'm amazed by some people's answers!!!

There is no answer because you did not state how the plane is moved?? If you start the engines and move the plane with it's own propulsion system it will definitely acquire the necessary forward speed and take off normally. If you move the plane with a ground driven force such as my B2910 or a ground driven vehicle capable of reaching the appropriate ground speed necessary for this particular plane to normally lift off, it will never take off or move forward.

This is funny though and truly amazing at the depth of "logical" discussion to try to prove points. The best one is that the moving runway will create airspeed and lift!!! Thanks Schism!!!

 

[schmism]

Now this is funny!!!! And I'm amazed by some people's answers!!!

heheheh

i know i get a kick out of the answers 2. well not so much the answers as yes/no isnt that intresting... its some of the explinations that crack me up.

 

[rback33]

LMAO I knew this would take off overnight. Pun intended Now, I still think the plane will take off at some point. The treadmill example must be valid like Iowa said. The engine and props cause forward thrust to propel the plane forward through the air mass, just like the car engine and tranny propel the car forward. They both move through the mass not the mass coming to them. (unless there is headwind, which I think for arguments sake here does not exist when everything is stationary at the beginning) They just do it in very different ways. Now I am no pilot, but I did sit next to one two weeks ago on my Continental flight into Kansas City. Does this qualify me for anything? And while we are at it.. why do we park on a driveway and drive on a parkway?

 

[LeadPoison]

Anyone ever see a float plane take off going up river?

So the answer is yes the plane will take off.

 

[WVBill]

Bingo!

I've been racking my brain trying to think of a real-life corrolary to the treadmill and you've nailed it!
You will take off when the airflow over the wings creates enough lift. regardless of how fast the river flows.

WVBill

 

[TheKid]

Yep, it's going to fly. It's the engines that move the plane not the wheels. With no head or tail wind the wheels will be moving twice as fast as the plane when it takes off.

For those of you who say the plane won't take off because there is no forward motion and thus no lift, think about this.

The conveyor belt only moves if the plane does. Since you're saying the plane is not moving, then neither is the conveyor belt.

 

[MossRoad]

If a bear poops in the woods and no one is around to hear it does it still smell?

 

[AlanB]

The corrollary for me with the treadmill was a mixture of that and earlier posts.

Picture the treadmill, now start riding an Impossible wheel (this is an impossible wheel by the way Unicycle.com :: Products :: Impossible Wheel )

Now for forward thrust, grab from someone else's post that we are not pulling ourselves forward by the wheel, we are pulling forward by our prop biting the air. Lets make the jump again and consider this the winch hooked to the wall on one side, your beltloop on the other.

Now, no matter how fast that treadmill turns (up to that point where bearing's fail etc.) That winch will still drag you forward, (at which point if you were an airplane you would fly)

Great post by the way, makes me really think.

I just keep wanting to say that we just need to lean to the right during this so gyroscopic precession can occur and we can fly forward....

That, and I figure everything else had been covered so had to get a Uni in there somewhere.

 

[rback33]

OK so the consensus is flight will occur. Now was someone right? And I know it wasn't me... at least not for the right reason....