Welcome back to Helicopter Lessons in 10 Minutes or Less!

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This video's topic covers part 1 of 2 of the Lift Equation. This subject can get pretty detailed if you ask an aerodynamicist. But for this video I want to keep it to just the basics. It's important to understand where Lift comes from so that pilots can understand what they can and cannot affect, either directly or indirectly. The lift equation itself is made up of 4 key elements. The first one being the Coefficient of Lift (CL). CL is a measure of the amount of lift a particular airfoil shape can produce. This is determined specifically by the shape of the airfoil itself and the Angle of Attack (AOA). Shape of an airfoil includes factors like blade span, camber, whether it's symmetrical or nonsymmetrical, etc. Obviously this cannot be affected while in flight. But the second part, AOA can be. As the flight controls are manipulated the Angle of Incidence (AOI) changes. These changes in AOI combine with induced flow velocities which result in Angle of Attack. So although AOA is an aerodynamic angle which we don't directly control, it is affected by AOI, a mechanical angle that we control directly with cyclic and collective inputs. For a better look at this I'd recommend checking out my Compensation for Dissymmetry of Lift video (   • Compensation for Dissymmetry of Lift ...  ).

The next element of the Lift Equation is surface area. This refers to the general surface area of the airfoil or rotor disk. The larger the area, the more lift (considering all other parts of the equation remain the same) and vice versa. This is generally thought to be unchanged,purely a factor of blade design, and unaffected by the pilot. However, consider blade coning and its effect on surface area. As the rotor cones, it's surface area decreases. During normal rotation the rotor system usually stays relatively horizontal and sometimes cones slightly about 25 degrees. This indicates more centrifugal force than lifting force. If lifting force begins to exceed centrifugal force, coning angle increases, surface area decreases, and lift is reduced. Some factors that affect rotor coning are: low rotor RPM, high gross weights, and excessively high Gforces. As a pilot you can directly affect all 3 of these which reduce blade surface area.

That wraps up part 1 of 2 if the Lift Equation. Thanks for watching and don't forget to check out Part 2 (   • The Lift Equation  Part 2  )! As always, safe flying!


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If you're just getting started and want more information, pictures, and more explanations, I'd recommend reading the Rotorcraft Flying Handbook http://amzn.to/2ifPlnZ

If you've already got a basic understanding, and want to further your professional helicopter education with advanced helicopter concepts, I'd recommend reading Cyclic and Collective, by Shawn Coyle http://amzn.to/2ifQGLx