Airfoil Characteristics in Helicopters

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This video's topic covers Airfoil Characteristics. To begin, I'd like to address some basic terminology and details associated with the lifting surfaces of the helicopter. In his book Cyclic and Collective (amzn.to/2ifQGLx), Shawn Coyle has a really good definition for an airfoil. He said that an airfoil is a surface that produces more lift than drag at a suitable angle. It is a surface that bends and manipulates the air in order to create lift. Generally when you think about airfoils you think about the main rotor and tail rotor blades. But to understand them more, we'll take a look at some basic terminology:
1. Blade Span: this is the length from the point of rotation (hub) to the tip of the blade. The longer the span, the larger the area of the rotor disk.
2. Leading Edge: this is the rounded portion of the airfoil that projects into the Relative Wind. This is the first part of the airfoil to encounter oncoming air.
3. Trailing Edge: this is the tapered Edge that trails away from the Relative Wind and is where the airflow from the upper and lower regions rejoin.
4. Chord Line: this is the imaginary straight line that intersects the leading and trailing edges. It is the reference line when looking at Angle of Attack and Angle of Incidence.
5. Camber: this is the curvature of the blade, usually broken down into the upper and lower camber.
6. Mean Camber Line: this is the line that is located midway between the upper and lower surfaces of the airfoil.
From here it is important to note the 2 types of airfoils: symmetric and asymmetric (also called non-symmetric). Symmetrical Airfoils: camber is the same on the top and bottom. The mean camber line is therefore the same as the chord line. Asymmetric Airfoils: one camber (usually upper) is larger than the other (lower camber). This means the chord line and mean camber line are different. However, both types of blades have their advantages and is advantages.
Symmetric Airfoils are simpler in design and therefore cheaper / easier to produce. These were the products of earlier helicopter airfoils and tended to made of heavier, sturdier materials that made them very stable.
Asymmetric Airfoils are a result of technological improvements in the field of composite materials. These airfoils are able to produce lift even at some negative Angles of Attack. They have better Lift to Drag ratios and better stall characteristics as well. One downside is that as the pressure changes different,y around the airfoil, its Center of Pressure (its concentration of aerodynamic forces) shifts along the chord line which causes blade flapping, leading, and lagging to a greater degree.
Keep in mind that there are more to airfoils than just the main rotor and tail rotor. Airfoils can be found in other places around the helicopter.
1. Vertical Stabilizer (vertical fin): this helps add directional stability in forward flight. Some are even cambered in order to offset or "off-load" the tail rotor above certain airspeeds.
2. Horizontal Stabilizers: these help hold the fuselage level in forward flight. They counter the nose-down tendency by pushing the nose up. This is done by pushing the tail down which pivots the nose up. In some cases you'll see an inverted asymmetric style airfoil for a horizontal stabilizer that actually increase autorotational performance as well.
3. Gurney Flaps: these are little strips of metal mounted 90 degrees perpendicular to the chord line on he trailing edge of an airfoil. The concept for these was actually discovered in auto racing by Dan Gurney and later brought to the field of aviation. While not specifically an airfoil themselves, these are modifications that increase the Lift to Drag ratio of an existing airfoil by improving boundary layer flow.
While these 3 are not exactly lifting the helicopter or thrusting it forward in flight, they are doing g a substantial amount of work to increase aircraft stability and control.
That wraps up airfoil characteristics! Thanks for watching! Don't forget to hit like and subscribe below. Be sure to like us on Facebook as well. As always, safe flying!
If you enjoyed the video or have any questions or comments, hit the like button and comment below.
If you're just getting started and want more information, pictures, and more explanations, I'd recommend reading the Rotorcraft Flying Handbook - 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 - amzn.to/2ifQGLx

[@davidwallace5738]

Thanks again,sir. I would like to see an explanation of swept tips rotor blades and the charistics of the air flow around them. Fly safe and keep up the good work.

[@spaceman152E]

great videos, I start flight school in 4 months and these are a great aid in the pre learning process

[@christopherpeters5916]

Outstanding

[@00boman]

As a beginning aviation student the videos are very helpful. Would love to see a tutorial for filling out the weight and balance sheet.

[@ahmadbems]

Thank you Jacob. great one

[@sharonburns4788]

Great lesson as usual, thanks.

[@courtneymariethompson7615]

Amazing 🎉

[@damianbarnes4277]

As someone who knew nothing about helicopters and watched five videos before this, it definetly made dots connect, could you perhaps post another vocab video?

[@charliekeyes6206]

Thank you Jacob,

[@mariojorgepiresdasilva9956]

Good vídeo 👍🏾🚁

[@elelyon555]

Thank you! 🙏🏼👍👏😃

[@christopherpeters5916]

Gurney . Adds a mile to the underside

[@mariotadeu1190]

muito bom

[@Code3Films]

Hey Jacob, can you do a video on rotor tracking?

[@helicopterlessonsin10minut10]

Mathew Kurland. I'll add it to the list. Thanks for the suggestion.

[@vlatkopopovski2685]

The authors have two wrong scientific approaches: researching the creation of Lift force and Low pressure at upper side of the wing, relative to the ground surface and Earth. I explain the aerodynamic cavitation and existence of Lee side aerocavern, and creation of Aerodynamic force.