4 ms·

I think it's quite easy to understand how planes fly. I figured out this as a kid when I pushed my hand out of a car window and tilted it at different angles. T

by Geee 7y ago

I think it's quite easy to understand how planes fly. I figured out this as a kid when I pushed my hand out of a car window and tilted it at different angles. This way you can feel the pressure differential and the how the air pushes the hand upwards or downwards.

o_nate 7y ago
A scientific explanation though would explain why those regions of high and low pressure get created.
- baq 7y ago
  Depends. Newton’s third law is scientific enough to explain what’s going on. Bernoulli and Navier-Stokes and all the hard equations are needed when you need to optimize the system or understand the micro scale, but they’ll simplify into conservation of energy or momentum in the macro limit.
  - o_nate 7y ago
    Newton's law doesn't do a good job of explaining why airplane wings have the shape they do. Why not just use a flat wing at a 45 degree angle?
    - baq 7y ago
      Exactly what I had in mind when I said Navier-Stokes. It isn't the job of Newton's third law to explain that. It's job is to say that if you have 200 ton aircraft and want to keep it in the air, it has to push 200 tons of air down no matter if it does that with a carbon-fiber CFD-optimized wing or a barn door nailed to the airframe.
copperx 7y ago
So, if a plane wing is like a tilted hand pushing air down, how come a plane can fly upside down with no change to its wings?
- GuB-42 7y ago
  tl;dr just point the nose up. The thing is that what really matters is the orientation of the trailing edge. And in airplanes the trailing edge points downwards. It is not always obvious because of the way wing profiles are designed but it is almost always the case. We could have it level, but that would mean the plane will need to always fly nose up in order to create lift, it would be uncomfortable, and most likely not ideal from an aerodynamic perspective. When you are flying upside down the natural orientation of the wing goes the opposite way, so the leading edge points up, and indeed you can't fly level with the nose pointing straight ahead. You need to point the nose up in order to compensate the natural wing orientation, and then point up even more to create actual lift. Of course, there are some more advanced considerations. Performance will generally be reduced when flying upside down, because the wings are not designed to do so. However some wings have a symmetrical profile, and in theory, they could be flown equally well in any orientation.

by Geee 7y ago

o_nate 7y ago

A scientific explanation though would explain why those regions of high and low pressure get created.

baq 7y ago
Depends. Newton’s third law is scientific enough to explain what’s going on. Bernoulli and Navier-Stokes and all the hard equations are needed when you need to optimize the system or understand the micro scale, but they’ll simplify into conservation of energy or momentum in the macro limit.
- o_nate 7y ago
  Newton's law doesn't do a good job of explaining why airplane wings have the shape they do. Why not just use a flat wing at a 45 degree angle?
  - baq 7y ago
    Exactly what I had in mind when I said Navier-Stokes. It isn't the job of Newton's third law to explain that. It's job is to say that if you have 200 ton aircraft and want to keep it in the air, it has to push 200 tons of air down no matter if it does that with a carbon-fiber CFD-optimized wing or a barn door nailed to the airframe.

copperx 7y ago

So, if a plane wing is like a tilted hand pushing air down, how come a plane can fly upside down with no change to its wings?

GuB-42 7y ago
tl;dr just point the nose up. The thing is that what really matters is the orientation of the trailing edge. And in airplanes the trailing edge points downwards. It is not always obvious because of the way wing profiles are designed but it is almost always the case. We could have it level, but that would mean the plane will need to always fly nose up in order to create lift, it would be uncomfortable, and most likely not ideal from an aerodynamic perspective. When you are flying upside down the natural orientation of the wing goes the opposite way, so the leading edge points up, and indeed you can't fly level with the nose pointing straight ahead. You need to point the nose up in order to compensate the natural wing orientation, and then point up even more to create actual lift. Of course, there are some more advanced considerations. Performance will generally be reduced when flying upside down, because the wings are not designed to do so. However some wings have a symmetrical profile, and in theory, they could be flown equally well in any orientation.