Originally posted by sonhouse I considered that direction also but it seems to be trivial, the plane would be at least partially forced to go tail first, no way anything like takeoff could happen unless the plane was somehow turned around and that was not in the question so it is a no-brainer to see nothing would happen. If a jet catapult on an aircraft carrier happened to grab the figh ...[text shortened]... strong engine. So I considered the other direction as being more conducive to an actual liftoff.
I really don't think you understand the problem the mythbusters are trying to address.
Originally posted by LemonJello I really don't think you understand the problem the mythbusters are trying to address.
Enlighten me then. I think the whole thing would be a lot clearer with some kind of anime to show just what they are talking about but with just a one sentence outline, I assumed one thing and maybe its really another.
Originally posted by sonhouse Enlighten me then. I think the whole thing would be a lot clearer with some kind of anime to show just what they are talking about but with just a one sentence outline, I assumed one thing and maybe its really another.
The airplane turns on it's engine and attempts to take off. The conveyor belt also turns on and begins spinning in such a way that the plane would be thrown backward if it's propeller weren't spinning.
However, the propeller is spinning. Can the conveyor belt keep the plane from taking off by moving backwards and using the friction in the wheels to "pull" the plane backwards as it tries to take off?
Here's a pretty good quick and dirty demonstration of the idea:
Originally posted by AThousandYoung The airplane turns on it's engine and attempts to take off. The conveyor belt also turns on and begins spinning in such a way that the plane would be thrown backward if it's propeller weren't spinning.
However, the propeller is spinning. Can the conveyor belt keep the plane from taking off by moving backwards and using the friction in the wheels ...[text shortened]... er it?
At least in case #1, the belt could be doing a thousand miles per hour but it couldn't stop the plane from taking off, the only thing happening here is the wheels would think the plane is going very fast, thats a no-brainer. Not sure what you mean saying IF the propellers have wings. They ARE wings. Look at the Osprey, it uses giant moveable propellers to put them horizontal to the ground like a helicopter and take off like a helicopter then tilt the props back to the normal orientation to fly forward. They would be totally screwed if that tilting mechanism stopped working after going to normal flight mode!
Originally posted by sonhouse At least in case #1, the belt could be doing a thousand miles per hour but it couldn't stop the plane from taking off, the only thing happening here is the wheels would think the plane is going very fast, thats a no-brainer. Not sure what you mean saying IF the propellers have wings. They ARE wings. Look at the Osprey, it uses giant moveable propellers to p ...[text shortened]... be totally screwed if that tilting mechanism stopped working after going to normal flight mode!
The propeller in the demonstration was simply a propeller on wheels. We're talking about an airplane, not a fan. We all know a fan will not fly under these circumstances.
You correctly understand the physics behind the question and have given the right answer.
An Osprey could glide, either as an airplane glides or as a helicopter does, depending on the orientation of the wings. But yes, I can easily see how disaster could result.
Oh, I see. They'd simply need a landing strip instead of a V/STOL carrier to land if the tilt mechanism stopped working but the propellers didn't. Or are the propellers too big for standard landing strip landings? Will they hjt the ground?
Originally posted by AThousandYoung The propeller in the demonstration was simply a propeller on wheels. We're talking about an airplane, not a fan. We all know a fan will not fly under these circumstances.
You correctly understand the physics behind the question and have given the right answer.
An Osprey could glide, either as an airplane glides or as a helicopter does, dependi ...[text shortened]... Or are the propellers too big for standard landing strip landings? Will they hjt the ground?
You should google an osprey video, the propellers are HUGE, much to big to land anyway but VTOL. They would definitely whack in pieces if they tried to land like a normal airplane. My guess is they allowed for that by having extendable struts or something but that is just a guess.
Originally posted by sonhouse You should google an osprey video, the propellers are HUGE, much to big to land anyway but VTOL. They would definitely whack in pieces if they tried to land like a normal airplane. My guess is they allowed for that by having extendable struts or something but that is just a guess.
Well, they can do an STOL by using a 45 degree tilt, but I see your point.
Originally posted by AThousandYoung Well, they can do an STOL by using a 45 degree tilt, but I see your point.
When I was in the Air Force, tech school in Denver, I started to build a model airplane. I carved a body out of a piece of balsa wood, maybe a 3X3 inch by one foot long. I carved it to look like the body of a small plane, and put on a set of wheels. I was going to put on wings and such but just for kicks, I got the engine going, one of those 1/2A jobs and found the thrust was way more than the drag of having nothing in the back but the wood. So we had this huge playing field that had several basketball courts around the perifery, and I took it to the middle of the field, started the engine and just let it go. Man, what a shock! The thing took off like a rocket but when it got maybe 25 feet down the road, the back end started to lift up. Apparently I had carved the body in a shape that gave it a bit of lift. So what happened is the back end lifted about an inch off the ground but a neat thing happened then. The tourque of the propeller flipped the whole thing around at some random angle and that slowed the thing down enough to put the back end back on the ground. So it shot off at an unpredictable angle at a tremendous speed, cavorting around the playing field till the fuel ran out a few minutes later. We were all laughing our assses off, it was the hit of the month. People were jumping out of the way of the thing flying towards them, only to have it flip in a random angle and take off again. What fun! I keep promising to build another one but to do it now, I would probably get the snot sued out of me for scaring a 4 year old or something!
Originally posted by sonhouse When I was in the Air Force, tech school in Denver, I started to build a model airplane. I carved a body out of a piece of balsa wood, maybe a 3X3 inch by one foot long. I carved it to look like the body of a small plane, and put on a set of wheels. I was going to put on wings and such but just for kicks, I got the engine going, one of those 1/2A jobs and f ...[text shortened]... o do it now, I would probably get the snot sued out of me for scaring a 4 year old or something!
For what it's worth, I'm going with "the plane launches", based on the argument that it isn't the wheels on the ground propelling the plane forward (in which case it wouldn't get the needed lift), but rather the jet engines pushing air through that pushes the plane forward.
I'm not precisely sure what happens on or to the conveyor, but I would think that however the conveyor behaves, it won't act to counter the forward thrust on the plane from the jet engines, because it is unable to cause substantial drag on the plane.
The plane takes off no problem at all. 200 hundred feet of backward moving treadmill, then 200 feet of asphalt, then 200 feet of forward moving treadmill, then 200 feet of concrete. The difference to the forward thrust is negligible in each case surely.
Mythbusters to take on - PLANE ON A TREADMILL!!...
26 Dec '07 16:50
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