With no airflow over the wings of an airplane

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C

Crono

Lifer
Aug 8, 2001
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Well, technically you could have flight if it's a VTOL aircraft.

But "lift" is generated by air moving across the wings in traditional aircraft. You could keep one in the air without wings, but then you would essentially have a missile without some means of controlling height and banking in addition to forward thrust.
 
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C

Crono

Lifer
Aug 8, 2001
23,720
1,502
136
coldmeat said:
wtf if that's 2009, then why don't I have a jetpack now?
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Fuel limitations, safety and cost.

Jetpacks have existed for a long time, but they aren't practical anywhere except for the limited propulsion ones they use in space.

What I do want to see sometime in the next 15 years is a fully working hoverboard available to buy :) Hopefully something in other than pink...
 
B

bignateyk

Lifer
Apr 22, 2002
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You need air flowing over the wings to generate lift. This is why the plane wouldn't take off from a treadmill (unless it were moving forward relative to the ground while on the treadmill).
 
sdifox

sdifox

No Lifer
Sep 30, 2005
100,466
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GuitarDaddy

GuitarDaddy

Lifer
Nov 9, 2004
11,465
1
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bignateyk said:
You need air flowing over the wings to generate lift. This is why the plane wouldn't take off from a treadmill (unless it were moving forward relative to the ground while on the treadmill).
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It would most certainly move forward relative to the ground. The flaw in logic that hangs up so many people in this stupid theoretical problem is the method of forward propulsion used by aircraft. So many fail to realize that a jets method of propulsion is pressure against an air mass as Endro points out and has nothing to do with the wheels or their contact with the ground like an automobile. An automobiles forward thrust could be offset by a treadmill(think dyno) because the auto's method of propulsion depends on the power imparted through the wheels to the ground. A plane does not rely on traction applied to the ground to move forward. All the plane needs to take off is for the jet to impart force against the airmass causing the plane to move forward causing air to flow over the wings causing lift, all a treadmill would do is make the wheel rotate at twice the normal speed until the plane lifted off.
 
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edro

edro

Lifer
Apr 5, 2002
24,326
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GuitarDaddy said:
It would most certainly move forward relative to the ground. The flaw in logic that hangs up so many people in this stupid theoretical problem is the method of forward propulsion used by aircraft. So many fail to realize that a jets method of propulsion is pressure against an air mass as Endro points out and has nothing to do with the wheels or their contact with the ground like an automobile. An automobiles forward thrust could be offset by a treadmill(think dyno) because the auto's method of propulsion depends on the power imparted through the wheels to the ground. A plane does not rely on traction applied to the ground to move forward. All the plane needs to take off is for the jet to impart force against the airmass causing the plane to move forward causing air to flow over the wings causing lift, all a treadmill would do is make the wheel rotate at twice the normal speed until the plane lifted off.
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Correct, but if the treadmill is infinitely long, the plane's propeller would pull it forward and it would take off.
I think most people understand the basics of flight.
The problem comes when a hypothetical question is visualized differently.

If you imagine a regular sized treadmill and assume the question is whether or not the plane will take off vertically, it will not take off.
If you imagine a super long treadmill and assume the question is whether or not the plane will move forward, and eventually take off (after the propeller overpowers the treadmill/wheel friction), then the plane will take off.

Only morons think the plane will lift vertically off of a treadmill without moving forward through the air volume first.
 
GuitarDaddy

GuitarDaddy

Lifer
Nov 9, 2004
11,465
1
0
@ Endro


I fail to see how the size of the treadmill makes any difference. If the treadmill is short the thrust of the engine pushes the plane forward off of the treadmill and it takes off. The point is the plane will move forward and take off regardless of the size or speed of the treadmill unless there is some obstacle at the end of the treadmill like a brick wall but that would be adding an additional variable not in the original problem.

But I agree that under no schenario would the plane take off vertically without moving forward, unless of course its a harrier jump jet :)
 
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edro

edro

Lifer
Apr 5, 2002
24,326
68
91
GuitarDaddy said:
@ Endro


I fail to see how the size of the treadmill makes any difference. If the treadmill is short the thrust of the engine pushes the plane forward off of the treadmill and it takes off. The point is the plane will move forward and take off regardless of the size or speed of the treadmill unless there is some obstacle at the end of the treadmill like a brick wall but that would be adding an additional variable not in the original problem.

But I agree that under no schenario would the plane take off vertically without moving forward, unless of course its a harrier jump jet :)
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Yeah, you're right about the treadmill... but most planes need >6ft (normal treadmill length) of ground to take off from.
 
Pray To Jesus

Pray To Jesus

Diamond Member
Mar 14, 2011
3,622
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Crono said:
Well, technically you could have flight if it's a VTOL aircraft.

But "lift" is generated by air moving across the wings in traditional aircraft. You could keep one in the air without wings, but then you would essentially have a missile without some means of controlling height and banking in addition to forward thrust.
Click to expand...

How would this work? There has to be something generating lift for the missile to stay in the air if it flis horizontal. I am thinking cruise missiles have small wings on them?
 
IcePickFreak

IcePickFreak

Platinum Member
Jul 12, 2007
2,428
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I watched this program a month or two ago about bush pilots up in Alaska. This one guy had to wait a day to land at this little air strip due to weather, and on the second day it was barely within what they considered safe since it was so windy. It looked so odd when the guy was about 5 feet over the run way, and moving maybe 5mph ground speed coming in for a landing.
 
ElFenix

ElFenix

Elite Member
Super Moderator
Mar 20, 2000
102,402
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GuitarDaddy said:
It would most certainly move forward relative to the ground.
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no, only needs to move forward relative to the air mass. there are RC planes that can fly backward relative to the ground if they're headed into a stiff breeze.



Pray To Jesus said:
How would this work? There has to be something generating lift for the missile to stay in the air if it flis horizontal. I am thinking cruise missiles have small wings on them?
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regular air to air missiles are ballistic.
 
Ichinisan

Ichinisan

Lifer
Oct 9, 2002
28,298
1,235
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ElFenix said:
no, only needs to move forward relative to the air mass. there are RC planes that can fly backward relative to the ground if they're headed into a stiff breeze.




regular air to air missiles are ballistic.
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They have guidance. If they're capable of flying horizontally, I assume there's enough thrust that those tiny movable fins work as flaps and provide lift.
 
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