RE: Can It Take Off??

RE: Can It Take Off??
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RE: Can It Take Off?? - 12/8/2005 11:25:06 PM

dick Hanson

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I saw it as a logic question - not one of mechanical interplay etc. involving a belt and friction and traction
The bottom line - aircraft act independently from the earth surface .
the propulsive system simply ignores movement of the plate(earth/belt) it may be resting on.
That satisfies the original "trick" question.

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Post #: 176

RE: Can It Take Off?? - 12/8/2005 11:38:11 PM

Crash90

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If it's an OS engine then it would probably take off. If it is a MDS then it probably wouldn't.

Sorry. I just had to.

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RE: Can It Take Off?? - 12/14/2005 5:47:49 AM

Semi Retired Aviator

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Lift is generated by forward movement of the wing. If the conveyor belt speed matches the potential speed of the aircraft, thereby keeping it stationary on the belt, then there is no lift generated, regardless of how much power you use, therefore no flight. This is with a jet engine.

Now for a propeller driven aircraft. If the power is increased to a ridiculous level, and the prop diameter enlarged to a point where it can generate enough airflow over the wings, then it MAY fly, but in that case it would also fly from a stationary position with no conveyor belt.

The difference is why a propeller driven aircraft is easier to pull out of a stall than a jet engine; the airflow with propellers is a large diameter, relatively low velocity airflow, allowing it to generate lift over the wing, as well as making the control surfaces more efficient with low forward speed, whereas the airflow from a jet engine is relatively small diameter, not allowing it to generate airflow over the wings. There is another reason, of course, that jet efflux doesn't flow over control surfaces; it would melt them, a typical exhaust gas temperature being close to 900 degrees C on take off.

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Post #: 178

RE: Can It Take Off?? - 12/14/2005 12:58:26 PM

CHassan

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If the belt is moving 5mph backwards how fast is the plane moving? .....5mph forward. Inrelation to what?

If the plane is moving 5mph forward in relation to the conveyor surface they are both moving at 2.5 mph in oposite directions. Therfore you have 2.5 mph of airspeed. Speeds must match!!!

If the plane is moving 5mph in relation to the ground next to the conveyor surface (the stationary ground) you have 5mph airspeed.

Can you stop the plane with the conveyor, yes but not if both are moving at the same speed.

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Post #: 179

RE: Can It Take Off?? - 12/14/2005 2:40:19 PM

dick Hanson

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The belt could have a surface speed of 100,000,000 MPH-either direction-and it means NOTHING to the plane
wheels are just little anti friction rollers not driven by the plane -they just reduce friction- replace them in your minds eye with zero friction skids

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RE: Can It Take Off?? - 12/14/2005 4:49:30 PM

3dbob37n

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Well, I kept putting bigger and bigger props on there and nothing happened. I even souped the engine up to 25,000 RPM and still nothing.
On my last try, the prop was so large that it cut the conveyor belt and the entire machine just exploded in millions of pieces. Sorry, fellas, I screwed up the conveyor.

3dbob

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Post #: 181

RE: Can It Take Off?? - 12/14/2005 4:51:52 PM

dick Hanson

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These logic questions will do that to you

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RE: Can It Take Off?? - 12/14/2005 4:59:08 PM

air mail rcu

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quote:

ORIGINAL: dick Hanson

The belt could have a surface speed of 100,000,000 MPH-either direction-and it means NOTHING to the plane
wheels are just little anti friction rollers not driven by the plane -they just reduce friction- replace them in your minds eye with zero friction skids

These little anti-friction devices let the plane move forward. If the little anti-friction devices don't move forward with the plane the plane will not move forward. The treadmill will not let the anti-friction devices move forward.

< Message edited by air mail rcu -- 12/14/2005 5:13:39 PM >

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RE: Can It Take Off?? - 12/14/2005 5:55:35 PM

Liberator

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Umm err, of course it will move forward. Here we go again.

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RE: Can It Take Off?? - 12/14/2005 7:27:49 PM

gtmattz

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Think about this for a bit.............

If the conveyor is set to match the 'rotational speed' of the wheels.. as the airplane moves forward.. the belt will in turn mov forward to keep the wheels rotational speed at 0rpm, as that is the 'current speed of the wheel'.........

The plane will take off as normal, but the wheels will be moving at 0rpm and the conveyor will be moving at the speed of the aircraft.

Solution?

I think so.

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RE: Can It Take Off?? - 12/14/2005 8:10:49 PM

britbrat

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quote:

ORIGINAL: gtmattz

Think about this for a bit.............

If the conveyor is set to match the 'rotational speed' of the wheels.. as the airplane moves forward.. the belt will in turn mov forward to keep the wheels rotational speed at 0rpm, as that is the 'current speed of the wheel'.........

The plane will take off as normal, but the wheels will be moving at 0rpm and the conveyor will be moving at the speed of the aircraft.

Solution?

I think so.

If you go back to the original question -- it said that the belt moved in the opposite direction to the AC --- it would be additive to the normal wheel rotation

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RE: Can It Take Off?? - 12/14/2005 8:14:42 PM

gtmattz

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I'm afraid it is YOU who need to re-read the original post....

this is a direct copy-paste (emphasis added by me)

<clip>
Imagine an airplane is on the beginning of a massive conveyor belt, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation.
There is no wind.
<clip>

Go back to page 1 if you don't belive me. I see nowhere that mentions the belt moves in relation to the aircraft. only the WHEELS.

< Message edited by gtmattz -- 12/14/2005 8:16:35 PM >

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RE: Can It Take Off?? - 12/14/2005 9:19:25 PM

britbrat

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Ooops -- you're quite right.

Doesn't change a thing though -- the plane will fly

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RE: Can It Take Off?? - 12/14/2005 11:28:51 PM

air mail rcu

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In order for the wheels to move forward THEY must rotate FASTER then the TREADMILL. Is this not true?

< Message edited by air mail rcu -- 12/14/2005 11:56:22 PM >

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RE: Can It Take Off?? - 12/15/2005 1:45:46 AM

boss2nine

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Look lets pretend that the earth is the conveyor belt and the air surrounding it is stationary if you rotate the earth 20 mph in the opposite direction of the aircraft you have the airflow over the aircraft from back to front nothing more than a 20 mph tailwind. Can you take off in a 20 mph tail wind? Well of course you can the speed that the aircraft is moving across the ground is not a simply not a factor. Aircraft propell themselves through air via the screw effect of the prop or the pushing effect of thrust from a turbine. The reason pilots do not take off in a tail wind is because at the airspeed required to lift the aircraft off the ground the ground speed is increased by the speed of the tailwind and runways are only so long. Besides it wouldn't matter wich way the conveyor belt moved the aircraft would still take off. they can take off in a headwind, tailwind or a crosswind. So the awnser to the question is yes, absolutely, without a doubt, willing to bet vital parts of my anatomy, the aircraft will take off.

just my two cents, well mabye three.

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RE: Can It Take Off?? - 12/15/2005 2:13:52 AM

air mail rcu

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In order for the plane to move forward the wheels would have to go faster then the treadmill. How can this happen if the treadmill is matching the speed of the wheels. Now the only wind generated is from the prop. The wheels are locked because of the movement of the treadmill. How do you get enough wind over the wing to fly?

Now where can we collect those body parts? My 85 year old Grandmother needs a kidney.

Simple question: I order for the plane to fly do the wheels need to go faster then the treadmill?

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RE: Can It Take Off?? - 12/15/2005 2:46:19 AM

dick Hanson

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no - forget them- the question was a logic exercize - the wheels have nothing to do with the plane taking off as long as they offer no restriction -which ever way they turn means nothing.
Libby pointed that out to me .

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