This page is for sharing my knowledge of Aerodynamics on a simple scale, with no math. Note: this will be continuously updated.
Types of forces on airplanes
As you probably know, there is Lift, Weight/Gravity, Thrust, and Drag. When all of these forces are in balance, the airplane flies without any acceleration in any direction.
Lift
Lift is what keeps the aircraft in the air. This is usually achieved with wings, though there is other ways of lift, such as the magnus effect, and sometimes with jets or propellers, like in Vertical Takeoff and Landing aircraft, or VTOL for short.
Wings
Wings are simple things, but also very complex. There are also multiple theories that cause wings to generate lift. Note that both of these ways of lift are used in most wings. The first one is Newton’s third law of motion. When incoming air hits a plate or a flat surface at an angle (the angle of attack, which is the angle the wing is relative to incoming air) the air would be deflected downwards, which pushes the wing up. Another theory is pressure difference. Before I explain how wings create pressure difference, I will explain why the difference in pressure would push the wing up. The wing is designed to have lower pressure on the top, and higher pressure on the bottom. Air wants to stay in equilibrium, so the wing is “sucked” up. This is actually what causes induced drag, when the higher pressure on the bottom flows around the wingtip to the lower pressure. But I’ll talk about that later. The wing creates this pressure difference because of Bernoulli’s principle. It states that faster moving fluid (in this case, air) will have a lower pressure. On a wing, the stagnation point is where the air splits to go over and under the wing. If the surface on top from the stagnation point to the trailing edge where the air rejoins is longer than the bottom, the top air must travel faster, creating less pressure.
Types of Wings (Basic)
Picture of all 4
Under-Camber
Under-Camber airfoils have high amounts of curvature in the wing. They produce lots of lift (especially at low speeds) but with that, lots of drag.
Flat-Bottom
Semi-Symmetrical
Symmetrical
Angle of Attack
Surfaces on the Wing
Terms-
Chord
Leading Edge
Trailing Edge
Top Camber
Bottom Camber
Dihedral
Anhedral
Airfoil- The airfoil is the shape of the cross section of the wing
Ways of lift
Propellers, Wings, Lighter than air gasses, and the Magnus effect. All of these create lift. Normally, propellers create lift perpendicular to the wing to create forward thrust, though sometimes they can be pointed upward to create lift that counteracts gravity, like in a helicopter or in a quadcopter. The magnus effect is not very practical in airplanes, though it has been done, like in RC planes. Peter Stripol made a video on this, which you can see here. The reason is that it cause great amounts of drag, and is much more complex than a wing. There are sailboats (no sails) that use the magnus effect to move forward, though. Lighter than air gasses are one of the most efficient ways to get around, but to do so is slow, and to lift a decent amount of weight requires huge amounts of gas.
Weight/Gravity
This is what makes everything fall down. Aircraft counteract this force with lift to stay in the air. There is not much to this factor of flight.
Thrust
Thrust is what makes the aircraft go forward. Because there is no way of using wheels like a car to go forward, most aircraft either use lift or Newton’s third law. Sometimes even both. By lift I mean a propeller, and by Newton’s third law of motion, (For every action there is an equal and opposite reaction) jets will blast out air behind them, pushing the plane forward.
Propellers
Propellers are wings. Normally, a power source rotates the propellers at a high speed, and the wings (Propeller blades) will generate lift, pushing the aircraft forward. The reason for the different angles on the blades is that they are moving at different speeds. Near the center of the propeller, the blades are moving slower, so the angle of attack is higher. On the outside, the blades are moving faster, so the angle of attack is less. The goal of this is to even out the lift along the propeller blade.
The slower and the less blades you have, the more efficient the propeller is.
The downside is that an aircraft can’t out fly it’s propeller. They sort of meet a speed limit (Unless it has a variable speed propeller, but that is different and has it’s flaws). This is because a propeller can only spin so fast. At slower speeds, the relative air to the propeller is sideways, pointing at the blades. As the plane gets faster, the relative incoming air (Angle of attack for the propeller blades) gets moved from sideways to the front of the plane, as the speed of the aircraft and the spinning of the propeller both affect the angle of attack. Eventually, the angle of attack for the blades becomes perfectly in line with the angle of the blade and it can’t generate any more thrust.
Jets
Jets are not as efficent
More specific types of thrust (Turbofans, Turbojets, and Rockets)
Drag
Drag is air resisting the craft from going in any direction. To move through air, the air must be pushed aside, which takes energy. There are many places and reasons why drag occurs.
Induced Drag
Induced drag happens in the wingtips. Below the wing, there is high pressure air, and above, low pressure air. Remember, air wants to stay in equilibrium (the same). So, high pressure air flows up around the wingtips to the low pressure zone, creating these spiral patterns in the air. It creates drag, and decreases lift at the wingtips. Wingtips help to prevent this, and decrease it’s effects.
Parasitic Drag
Parasitic Drag is simply drag when an object moves through a fluid (in this case, air). It is the combination of many types of drag.
Skin Friction. Air is a fluid, so it sticks to things. When an object moves through the air, the air sticks to it and pulls it back.
The LiPo Projects 