Whenever I see an explanation about how airplanes can fly, I see that the shape of the wing is different on the top side to create a dragging force that pushes the airplane up. The top is curved and the bottom is flat. If a airplane turn upside down, should it fall faster because it’s dragging down ? I saw airplanes doing acrobatics on air , and some of them looks impossible because of this.
In: Engineering
the wings provide force in relation to the angle in relation to the direction of airflow. just like when you put your hand outside the window in a moving car and the air forces your hand up or down depending on what angle you hold it at. if the plane is upside down but pointed above the horizon, then it’s still going to be pushed up
The shape of the wing has more to do with being aerodynamic than creating lift. The vast majority of lift comes from the angle of attack, which is the angle of the wing relative to its motion through the air. You can create lift with a flat wing, it just won’t be very efficient and will have a higher stall speed.
There are several different wing shapes depending on the needs of the aircraft, like how fast it is designed to cruise at, how low the stall speed is, etc. They might have more curve underneath, which creates more lift but also more drag, or even diamond shaped to reduce the negative effects of supersonic flight.
Acrobatic planes that are designed to spend an unusual amount of time upside down have wings that are symmetrical from top to bottom. They are more of a teardrop than most wings, which are more like a flattened teardrop.
The symmetrical wing is less efficient in normal, level flight but is equally efficient when flying upside down.
If upside down, for example, some of those surfaces are movable and will be adjusted to counteract the natural tendency to “float” towards the ground. If you look closely, you’ll also notice that the engine is pushing in a direction that forces the plane to *not* move towards the ground. We call this orientation angle of attack.
Acrobatic airplanes are not very fuel efficient. The angle of attack, the orientation of the wing to the path of motion, is also a major contributor to lift. The shape provides fuel efficiency, as that’s what the airplane is usually optimized for.
The shape of the wind is not the most relevant part for the lift it is primarily relevant to reduce the drag when you travel through the air.
You can make a wing that is flat on both sides jus look at [this rubber](https://www.shelllumber.com/resize?po=https%3a%2f%2fimages.orgill.com%2flarge%2f9734773.JPG)[ band toy aircraft](https://www.shelllumber.com/resize?po=https%3a%2f%2fimages.orgill.com%2flarge%2f9734773.JPG)[.](https://www.shelllumber.com/resize?po=https%3a%2f%2fimages.orgill.com%2flarge%2f9734773.JPG) A wing-like that can fly but is is very inefficient. What you need to do is to turn it relative to the air you pass through and if the front point up it will create life. This is called the angle of attack.
Stick your hand out of the window the next time you travel as a passenger in a car. Depending of how you turn your hand you get a force up or down. There is also a force back and that is the drag. The engine if an airplane is there to counteract the drag so the speed remains constant so a more efficient wing
So an aerobatic aircraft has quite symmetrical wings so quite full inefficient but high maneuverability. A fighter jet also has quire symmetrical wing [the profile of an](http://airfoiltools.com/airfoil/details?airfoil=naca64206-il)[ F-16 wing](http://airfoiltools.com/airfoil/details?airfoil=naca64206-il) for maneuverability and supersonic performance.
If you look at it close it the more complex where the max angle of attack you can have before the airflow detaches from the wind and you have no more lift and you stall depends on the wing shape. Lift a certain speed vill depend not on the shape of the wing.
This is because the lift that a wing generates is also impacted by the [angle of attack](https://www.skybrary.aero/images/8/8d/AoA.jpg), or how the plane’s wing is angled towards the oncoming wind. In the picture that I linked, you can see that it has a positive angle of attack (the wing’s leading edge is pointed slightly upwards) and most airplane wings are optimized to generate lift in in this configuration. However, if you gave the wings a negative angle of attack (so they’re pointing downwards) they would actually generate lift downwards. This is what airplanes do when they fly upside down. Aerospace engineers can use something called a [lift curve](https://upload.wikimedia.org/wikipedia/commons/2/22/Lift_drag_graph.JPG) to examine the relationship between the angle of attack and the lift that a wing generates. In this image, you can see that a negative lift can be generated at a negative AoA.
Most explanations of aerodynamic lift vastly overstate the effect of Bernoulli’s Principle, leading to your confusion. Wings generate most of their lift by pushing air down, not by pressure differentials.
An acrobatic airplane has a less efficient wing shape to make it useable in regular and inverted flight, and then typically makes up for it with raw power.
Or if doing a loop, use gravity to build up more speed. More speed, more airflow over the wing, more lift.
> I see that the shape of the wing is different on the top side to create a dragging force that pushes the airplane up. The top is curved and the bottom is flat. If a airplane turn upside down, should it fall faster because it’s dragging down
You probably heard some variation of the [equal transit time](https://www.grc.nasa.gov/www/k-12/airplane/wrong1.html) fallacy, which is bullshit. Wings do not have to be curved on the top and flat on the bottom – in fact, aerobatic airplanes often have a symmetrical airfoil, which works just as well when flying inverted as it does upright.
The direction of the lift on an airfoil depends on the *angle of attack*, which is the angle the wing makes with the oncoming airstream. The pilot can control the angle of attack with the elevator. If the plane rolls inverted while maintaining a constant angle of attack then the lift would indeed point towards the ground; if the pilot intends to maintain level inverted flight then he must push forward on the stick until the lift balances the weight again.
Also note that an aircraft can be upside down while still maintaining positive G loading. [Here’s a nice demonstration of that fact](https://www.youtube.com/watch?v=DjHD1U-QWv4). In this case, the lift on the wings never changes direction and does point towards the ground at the apex of the maneuver.
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