Rotorcraft history book?

[RotaryWingBob]

Does anyone know of a book (or article) which documents how Sikorsky and others figured out how to make rotorcraft fly, and in particular, how they figured out blade flapping would compensate for dissymmetry of lift?

I'm curious about this because flapping seems like such an elegant solution to an otherwise knotty problem...

 

[Chris Connor]

Bob,
Have you been to www.helis.com?
Chris

 

[Nav8tor]

It was actually Juan de la Cierva, the inventor of the autogyro, who developed many of the methods to overcome dissymmetry of lift in a rotor system.

I have a series of articles about it, but hard copies only. One in particular is from Air & Space magazine, December 1989, January 1990.

 

[RotaryWingBob]

Bob,
Have you been to www.helis.com?
Chris

Yes, and it's an interesting site. But I couldn't find anything that gave any insight into how they figured out that flapping would work.

 

[RotaryWingBob]

It was actually Juan de la Cierva, the inventor of the autogyro, who developed many of the methods to overcome dissymmetry of lift in a rotor system.

I have a series of articles about it, but hard copies only. One in particular is from Air & Space magazine, December 1989, January 1990.

I had forgotten that autogyros would have the same problem. Do your articles give any insight into how he figured out that flapping would do the trick?

 

[Robert]

Bob,
If you have not yet seen them, I would recommend the books from Ray Prouty on helicopter aerodynamics:

http://www.amazon.com/exec/obidos/ISBN=9991992162/paulcantrellshelA/103-4365248-3723801

http://www.amazon.com/exec/obidos/ISBN=9999414192/paulcantrellshelA/103-4365248-3723801

http://www.amazon.com/exec/obidos/ISBN=9990067503/paulcantrellshelA/103-4365248-3723801

They may not go into all of the history, but they will give you a firm hold on what happens.
Robert

 

[Chris Connor]

Try this Bob
http://centennialofflight.com/history/helicopter.html
about half way down the autogyro.
Chris

 

[RotaryWingBob]

Try this Bob
http://centennialofflight.com/history/helicopter.html
about half way down the autogyro.
Chris

Interesting article, thanks Chris.

 

[RotaryWingBob]

From:

http://www.enae.umd.edu/AGRC/Aero/history.html

[size=-1]De la Cierva built two more full-scale machines with single rotors before he achieved final success in January 1923 with the C-4[/size][size=-1].[/size][size=-1] Based on his tests with small models, this fourth machine incorporated blades with mechanical "flapping" hinges at the root, which de la Cierva used as a means of equalizing the lift on the two sides of the rotor in forward flight. This novel solution to the problem of asymmetric aerodynamic forces allowed the blades to flap up or down about these hinges, responding to the changing airloads during each blade revolution. Although the principle of flapping propeller blades had actually been suggested by [/size][size=-1]Charles Renard in 1904 and the idea of flapping hinges was also patented by Louis Breguet in 1908, Juan de la Cierva is credited with the first successful practical application to a rotating-wing aircraft[/size]






Found this image while doing a web search. Delft University of Technology is developing a tail rotor-less helo using this for the main rotor hub:

Thanks, Steve. I still haven't found out what made these guys figure out that blade flapping might work.

That picture looks like every pilot's nightmare to preflight!

 

[ausrere]

Does anyone know of a book (or article) which documents how Sikorsky and others figured out how to make rotorcraft fly, and in particular, how they figured out blade flapping would compensate for dissymmetry of lift?

I'm curious about this because flapping seems like such an elegant solution to an otherwise knotty problem...

According to this article: http://www.vtol.org/History.htm Sikorsky didn't figure it out, a Spaniard named Juan de la Cierva did for the Autogyro in 1920 and it was adopted by Sikorsky and the others later..

"The Breakthrough of the Autogyro"

"In 1920, Spaniard Juan de la Cierva built the C.1 autogyro, but it rolled over while taxiing, due to the destabilizing effect of the rotor blades which were rigidly attached to the mast. The airspeed of the advancing blade was higher than that of the retreating blade. This caused a dissymmetry of lift resulting in a rolling moment. No helicopter had encountered this problem, as the forward flight speed was still painfully slow. [10,23]

In 1922, Cierva built a scale model with articulated hinges that allowed the blades to move about the hinge point. Each retreating blade could therefore flap downward as the advancing one's airspeed lifted it up, so that the lift forces were more closely balanced. This minimized the aircraft's tendency to roll over while accelerating in flight. Later, Cierva added a drag hinge to the blade/mast junction, allowing the blade to pivot forward or rearward slightly during rotation. This fully articulated hub relieved the stress on the blade root. Problems with ground resonance led Cierva to fit drag dampers to the hinges. This is the basis for the modern fully articulated rotor head. [10,23]"