rmh

Even Libby saw thru this one -

air mail rcu

If the plane would take off then we can have smaller airports. No catapults on carriers. And the Japanese didn't need to build and entire Inland for a airport. All we need are some large belt sanders. And they really don't need to be that big. Just one under each wheel.

One question: If we are walking on a people mover in the opposite direction and the people mover is matching our forward speed do we ever get to where we are going?

Phlip

No fair changing the rules of the puzzle! The original didn't say anything about belt sanders! If you sand a hole in the tires, how will the plane roll? And how will you keep from ruining the CV joints and ball joints as the plane falls down off the sanders?
Just put it in 4WD and gun it. It'll go!

Liberator

That makes me more nervous than you can imagine. The watching part that is.

3dbob37n

OK, Hanson, you can't figure it out either and are copping out.

Why don't we meet at O'Hare and we'll borrow an L-1011 and face it in the direction the planet turns and see if it will take off? I'll take the left seat. Hanson, you run the computer to record our progress. Bent Wings, since you started all this, you get your butt back in the galley and get the food ready.

This is the only way we can solve this problem because it seems no one knows the answer.
So much for all you aeronautical genius's. Bah Humbug!


3dbob

air mail rcu

Sometimes you have to rock it back and forth.

rmh

Sure -I answered it 3 time --Libby also said you guys are barking up the wrong tree - (always watching )
the answer -- the wheels on the belt mean -Zippo- nada - keine-nothing - the question is simply a trick question --- the aircraft taking off has nothing to do with the wheels rotation
The ONLY reason land based aircraft have wheels is to reduce the friction from forward motion.
sheesh---
first aircraft had skids -I remember helping Wil and Orvie back there at the big sandhill---

David Cutler

Yep!

[8D]

-David C.

bentwings

3dbob

this is going to be a long flight with you guys driving. I was thinking of a load of Omaha Steaks and Idaho potato steak fries.. Think this will affect the take off??

BTW I'm doing some durability testing involving needle roller bearings at work. They might work pretty well in the conveyor rollers. They will probably need them with the ground speed we'll need to get off with all those steaks aboard.

I wonder if we should bring along some "black crow" for those unbelievers. I heard slightly rare is the preferred temp.

bentwings

David Cutler

It only teases the brain if the difference between airspeed and groundspeed isn't understood.

It's airspeed that provides lift, and the prop is working on the air to increase airspeed not the ground.

Groundspeed, however it is looked at, doesn't enter into it.

In fact, I am sure there are a lot of people here who have landed a plane at a negative groundspeed (that is, travelling backwards) when the windspeed exceeds the required landing airspeed.

-David C.

Tall Paul

The motor pushes the plane.
F=ma.
The plane flies.

rmh

FMA - I thot was an electric motor sales group.
This "quiz" is more in the nature of a basic IQ test than a question of aerodynamics.

air mail rcu

I see a lot of opinions here. But I don't see anyone proving anything. Opinions are just like a!@#$% everyone has one. Just because you have an opinion doesn't make it right. I think some of the poster here need to realize that. This is a question with no answer till someone proves something.

If everyone here looked at a bumble bee half would say it can't fly and half would say it can. I still say they can't.

Flyfalcons

The problem is for the airplane to take off, it needs to be moving forward (no wind). If the plane is moving forward, then the belt would not be spinning at an equal rate to the tires.

Kind of a PITA question. Sort of like asking, if God is capable of doing or creating anything, can He create a rock so big that He can't move it?

rmh

OK-what do the wheels turning have to do with the plane moving forward?
On an airplane - wheels do one thing - reduce friction /resistance-that's it
If the wheels were simply made of ice and had NO friction/resistance to the belt/ground/grass what have you-what would the effect be?
You can study this one as much as you want but -there is simply no involvement with the wheels -except removing friction
The "question" is simply an exercize in logic- no math - no formulas required

David Cutler

The speed of the belt, the revolving speed of the wheels, and anything else that doesn't take part in the change in airspeed has nothing to do with whether the plane flies or not. As soon as V1 speed is achieved, however it's achieved, the plane will fly.

Moving belts, spinning wheels have nothing to do with it. If there's enough air passing over the wing to provide lift it flies. If there isn't, it doesn't. End of subject.

-David C.

David Cutler

100% agree.

-David C.

David Cutler

The belt could be travelling at 1,000,000 mph or zero, and the wheels spinning at 1,000,000,000 rpm or zero. It makes no difference to the airspeed of the plane, and therefore the air passing over the wing.

You are confusing groundspeed with airspeed still.

-David C.

Flyfalcons

The problem is the way this question is worded. It is a trick question. Assuming there is no bearing friction on the wheels and calm winds, the airplane doesn't care what is going on with the wheels. The engine will push the air, the plane moves forward relative to the air. Because of this, the belt will be unable to match the speed of the turing wheels. However, the problem states that the belt will match the speed of the wheels. If that is the case, then for every knot the plane moves forward, the belt will move one knot in the other direction. It will never allow the plane to accelerate, because for it to do so, its wheels must turn faster than the belt (which is not allowed in the question).

If the question were worded so that the belt moves in the opposite direction of the plane at the same speed the plane is moving, it would be much more cut and dry. However, the part about it matching the speed of the wheels turns it into a trick question.

Hopefully I've made things more confusing for everyone.

David Cutler

I agree this is where the confusion lies.

However, it assumes that the belt has some input into the forward motion of the plane, and, apart from a very small amount of friction in the wheel bearings, it simply doesn't. It could be travelling 'backwards' at any speed it likes and the wheels will follow suit BUT the plane will still accelerate as much as the engine and prop can make it accelerate.

The original statement assumed that the engine thrust is on the belt and the motion of the belt will affect this thrust. It isn't, it's on the air.

-David C.

Flyfalcons

That is correct, no matter how hard it tries, the belt physically cannot equal the speed of the tires (assuming no friction). The question states that the belt will always equal the speed of the tires, and that is what makes it a trick question.

Now onto that God question.

3dbob37n

Ah, gentlemen, but the belt does match the speed of the wheels. Now what?
Magic, but nevertheless, it does.
We all know that our modern over powered models will just take a leap forward and go.
But that is not what the question is about.

3dbob

air mail rcu

This might answer the question.

http://www.avweb.com/news/columns/191034-1.html

David Cutler

So what? I doesn't matter if it matched the color of Einstein's eyes, your underwear or Florence Nightingales hat, the wheels / ground interface has nothing to do with the lift.

I confess there are no other ways to say this without repetition.

[sm=bananahead.gif]

-David C.

3dbob37n

But, without forward movement, which the belt prevents, one cannot get lift.

I hope after all this discussion that we will finally get a formal answer to the question.

I sent this question out to my club and got all kinds of answers.

3dbob