How dose it creat lift upside down?

Question

Due to the shape of an airfoil or wing a high pressure is created underneath, and a low pressure on the top surface, creating lift. How do the same principals apply on an inverted wing.

Answer 1

There are two factors to consider in a wing producing lift. The airfoil is one factor while the angle of attack is the other.

Lift is produced anytime the airflow over the top is faster than the airflow over the bottom. If we have a wing flying at a 0 degree angle of attack, then the airfoil shape is the only thing affecting the air flow. If it is a symmetrical wing, there is no lift at this angle of attack. If it is a semi- or non-symmetrical wing ( say a flat bottom like a Clark Y airfoil) then the airfoil itself will produce lift.

Now, if the plane flies inverted, the airfoil shape can still contribute to the lift, as can the angle of attack. If we are back with a truly symmetrical airfoil, it makes no difference if the wing is right side up or upside down. At 0 degrees, there is still no lift. If we have a non-symmetrical wing that is inverted, at 0 degrees it produces a downward thrust (lift towards the real top).

But, if we have the non-symmetrical wing we can fly at an angle of attack where the wing is producing lift towards the bottom of the wing while we are inverted. It just means the plane is not level but has the nose pointed towards the sky (or bottom of the plane). If you are sitting in the pilots seat and do this, to maintain inverted flight, you would hold down elevator control. The elevator would be trying to force the nose towards the bottom of the plane, thus creating the angle of attack needed for the lift.

I hope I explained that correctly and clearly enough to understand. If you . If you want to see it clearly demonstrated, see if you can find a club near you that flies radio controlled airplanes. Most of their trainers will have a flat bottom wing and enough power to fly inverted. It makes the angle of attack part very clear to see though.

Answer 2

The most accurate answer so far:
"If the wing can deflect enough air downwards to counter the weight of the aircraft...she'll fly! "

The big secret is that physicists found a new aerodynamic principle, and it's called the coanda effect. Mostly applied to hydrodynamics, it is the air's tendancy to adhere to the smooth surface of the wing.
That's it.
But the trick is that the air is directed downward.
Newton's laws of physics take over then, with the equal and opposite reaction stuff.
The other way to direct the air downward is to tilt the wing upward, increasing what's called the "Angle of Attack". This also directs the air downward, creating lift.
Other comments about a dual cambered wing apply to aerobatic aircraft. When the wing is level, air is not directed downward, and there is no lift.

My ground scholol instructor taught us the standard line about the air traveling faster and the pressure above the wing yada, yada, yada. But then he told us the truth about the coanda effect and the air adhering to the surface of the wing, and took that opportunity to warn us about frost and how it disrupts the flow of air - and the coanda effect - and that less air is directed downward, resulting in less lift, requiring greater take off speed and a longer runway and you can easily get into trouble needeing those last two things.
So, if your cambered wing is inverted and level, you will direct air upward, adding a downward force to the force of gravity, putting you on the ground in a hurry. But if that inverted wing is tilted upward enough, it will direct the air downward and once again you will have lift.
Happy flying.

Answer 3

The angle of attack creates a quasi air foil. I have flown non-aerobic planes upside down and you are lucky to keep about 12% nose up compared to vertical. Aerobatic planes have semi-symmetrical airfoils. But also means they always have to keep a little bit of wing angle either way to achieve good lift.

I love the Barn door answer as it is quite true. You just don't fly with the best efficiency when the airfoil isn't "tuned" for the orientation.

Answer 4

Airfoil shape is overrated as a way to understand basic flight principles. I mean 1) planes can fly upside down 2) you don't see house flies with triple-slotted Fowler flaps, leading edges slats, etc.

If you take a barn door and push it through the air at a 10 degree angle of attack, it will generate lift. (Consider the idiots who transport mattresses on their car roof using only twine). If the barn door were curved a little bit one way or the other, it would still generate lift at 10 degrees AOA.

Now, if you wanted to optimize that barn door for fuel-efficient cruise, good take-off performance and decent behavior when it starts to ice up, then you'd round off the leading edge, taper the trailing edge (but not too much), curve it up in the middle (but towards the leading edge), add slats, flaps, and maybe some vortex generators, etc. Give it a long length relative to its width (chord) and maybe put some fancy tips on it to reduce wingtip vortices. And pretty soon that barn door would be looking like a 737 wing. But it still genrate some lift when flown upside down.

Answer 5

The details of shape don't mean anything in regard to lift. When the angle of attack changes, the stagnation point (where the air splits on the nose to be either top or bottom surface air) moves toward the surface that's coming around to better see the oncoming wind. This forces a shorter flow path on the surface that's 'pushing' and a longer flow path on the opposite surface. Ergo, higher average speed over the 'top' and lower speed over the 'bottom' and the pressures corresponding to the Bernoulli theorem.....

PS: Todd, Henri Coanda was at the height of his aeronautical career in 1915. So much for the 'new' Coanda theory......

Answer 6

Same way it does right side up...
Combination of angle of attack, bernoulli, Newtonian lift

Now most aircraft designed to fly inverted will have a symetrical airfoil (same shape on upper and lower halfs) but it's not necessary. Given enough power and high enough angle of attack (AoA) just about any plane can fly upside down.
If the wing can deflect enough air downwards to counter the weight of the aircraft...she'll fly!

Answer 7

Planes that fly upside down have a double camber wing design that creates lift whilst upside down, planes with this type of wing are often called aerobats and are rated to perform aerobatic manouvers impossible in a single camber winged airplane.

Alternatively a plane with a weight to trust ratio exceeding 1:1 (such as a military jet) requires only minimal lift if any to fly upside down.

Answer 8

If you fly level right side up in a plane and flip over, the inverted wing will remain in level flight. If you try to climb, however, you will fail. The wing does not create lift, but it will allow you to fly level under power.

Answer 9

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