BS: The Mythbusters airplane takeoff problem

Subject: RE: BS: The Mythbusters airplane takeoff problem
From: Little Hawk
Date: 02 Nov 12 - 08:53 PM

Hmmm. Well, the propellors on the airplane don't make it go "up", they make it go forward. The fact that it is going forward causes air to flow more and more rapidly over the airfoil (the wings). The airfoil generates "lift" when air is passing rapidly over it from front to back, and that lift causes the wings to be pushed upward and the plane to rise up after a bit and take off from the ground...while the propellors continue to provide forward thrust.

Seems to me that the plane wouldn't be able to generate any lift if it was, in effect, standing relatie to the surrounding air. It would certainly generate thrust (forward movement), but not lift.

You normally take off into the wind if you can, because that provides more lift and a shorter takeoff run.

How am I doing so far?

Subject: RE: BS: The Mythbusters airplane takeoff problem
From: gnu
Date: 02 Nov 12 - 04:10 PM

I would have appreciated one of those conveyor belts in Makkovik, Labrador one day. An overloaded Otter that has to get back on the water after only lifting 20 feet and then having problems with stability is a tricky and dangerous situation.

The pilot debited a lot of cargo but didn't need to lose as much as he did because I am sure there was at least 20 gallons of piss that when over the side of the dock before the next takeoff.

Hehehehe... he asked me what was in the burlap sacks. I told him they were soil samples of gravel for building the new runway. He looked at me in shock and said, "Ye mean fookin rocks.", whereupon they both sank 20 feet into the salt water dockside. And I really didn't care about the fookin rocks at that point. >;-)

Subject: RE: BS: The Mythbusters airplane takeoff problem
From: Jeri
Date: 02 Nov 12 - 03:49 PM

What 999 said. It depends on windspeed. The MPH serve to generate the wind. There's that song "you are the wind beneath my wings" (but you need wind over them too).

The gliding that prop planes can do is not usually generally done by jets, which do not glide so much as they do plummet. But that's because of weight, wing shape and the amount of lift needed...I think.

Subject: RE: BS: The Mythbusters airplane takeoff problem
From: GUEST,Lighter
Date: 02 Nov 12 - 03:19 PM

Even I figured this one out.

It works with jet engines too.

Subject: RE: BS: The Mythbusters airplane takeoff problem
From: Bettynh
Date: 02 Nov 12 - 01:52 PM

My son and I watched that one with fascination. If the plane normally gained speed due to the action of the wheels, it couldn't take off. But the wheels are passive, simply reducing friction for the moving force - the propeller(s), which can do its job, no problem.

Subject: RE: BS: The Mythbusters airplane takeoff problem
From: GUEST,999
Date: 02 Nov 12 - 01:47 PM

The airplane will be able to take off when the wind over and under the wings provides the lift it needs to get off the ground.

Subject: BS: The Mythbusters airplane takeoff problem
From: Jim Dixon
Date: 02 Nov 12 - 01:33 PM

Those of you who loved arguing about the Monty Hall problem might enjoy this one.

This one was tested in one of the episodes of Mythbusters. I don't know where they heard of the problem, but I assume it had been in circulation earlier.

Suppose you have an airplane ready to take off, but instead of standing on an ordinary airport runway, suppose it is standing on a monster conveyor belt. Suppose the airplane is headed west. At first, both the airplane and the conveyor belt are motionless. Then the pilot revs up the engine, such that the airplane would normally begin moving west. At the same moment, the conveyor belt begins moving the opposite direction. The conveyor belt accelerates at the same rate as the normal acceleration of the airplane, such that, for instance, by the time the airplane would normally be moving westward at 50 mph, the surface of the conveyor belt is moving eastward at 50 mph, and so on.

So the question is: would the airplane be able to take off, or not?

Unlike the Monty Hall problem, this is not "pure" logic, but it requires some rudimentary knowledge of how airplanes work. If you lack that knowledge, I suppose someone will supply it as soon as you have shown your ignorance by guessing wrong!

I know this problem has been discussed and argued about at great length in the forum pages of the Mythbusters website. I would have posted a link, but I can't get through to the forum right now.