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Item 1375

OTHER: Rotor Concept - Independent Root & Tip - Aerodynamic Tip Method

Overview:

The pitch at the root of the blade is physically moved by a root pitch horn.

The pitch at the tip of the blade is change by aerodynamic pitching forces. (trailing-edge flap etc.)

The Kaman flap at the tip. See below Servo Flap: ~ As of November 27, 2002, I have been unable to find any patent or Internet reference to the use of a device to control the pitch at the root and a separate device to control the pitch at the tip. Rick has mentioned that perhaps Kaman had a patent on this idea. Note that this idea entails a large amount of twist, from positive to negative.

Idea: Leading and trailing flaps on a tip segment, which has a large chord and small span. Moving both flaps up may impart a positive twist at the tip and moving both flaps down may impart a negative twist at the tip.

Note:

Servo Flap Method:

The skin of the blade is firmly attached to the spar at all locations along the span. The skin and the spar twist in unison. The root of the blade is controlled by the root pitch horn. A leading &/or trailing flap is located near the tip. A push-pull rod, located in the center of the spar, activates the flap(s) to change the pitch of the spar and skin at the tip of the blade. This tip control is somewhat similar to Kaman's servo tab.

Morphable Tip Method:

A modifiable tip, which can be bowed upward and downward, will aerodynamically impart a pitching action to the tip of the blade. This method is very similar to method 2. The aerodynamic action of both # 2 & 3 are very dependent on the moment arms of the "flap(s)" and the torsional flexibility of the blade etc.

1. Servo Flap Tip Method:

Performance of Swashplateless Ultralight Helicopter Rotor with Trailing-Edge Flaps for Primary Control ~ Have hard copy.

A Parametric Design Study for a Swashplateless Helicopter Rotor with Trailing-Edge Flaps ~ http://www.brazd.ru/books/b0005/book/58af127.pdf

There supposedly is a patent by Kaman on independent root and tip control.

Would the greater chord of a BERP type of tip provide leverage for pitching the blade?

I suspect that twisting the blade tip by servo-flap will have less authority than the torque tube method in overcoming the blade's resistance to twisting.

Related Patents:

Rick Andrew thinks that Kaman has a patent on a rotor blades control where a swashplate sets the root pitch and his servo-flap sets the 75% of span pitch. He is going to look up his copy of this and send it to me. I could not find anything relevant by doing a patent search on 'Kaman Aerospace' and by reviewing the Kaman folder. September 13, 2002

He came across the article. It was 'CTR Control System', on the Seasprite, in Aviation Week & Space Technology ~ Aug 5, 1968 ~ March 31, 2004

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Results of search on; ("active twist" OR "variable twist") AND blade AND (helicopter OR rotorcraft OR "rotary wing")

5,505,589 ~ Controllable variable twist rotor blade assembly ~ Have hard copy.

5,137,228 ~ Rotary wing with torsionally flexible blades ~ Have hard copy.

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Title: Individually Blade control by servo Flap and Blade root control - A Collaborative Research and development of programs. Author: Schimke, D. *) Author: Jaenker, P. * *) Author: Blaas, A.***) Author: Kube, R. Author: Schewe, G. Author: Kessler, CH * * * *) *)Eurocopter Germany Author: **)dasa Author: ***)zf aviation technology GmbH Author: ****)tu Braunschweig Title: Individually Blade control by servo Flap and Blade root control - A Collaborative Research and development of programs. Conference: 23rd European Rotorcraft forum, 16.-18 September 1997, Dresden Organ: Proceedings OF the 23rd European Rotorcraft forum Feature year: 1997 Key words: servo flap, rotor aerodynamics, individually blade control Language: English Type of publication: Proceeding (possibly in book form) Organizational unit: Institut for aeroelastic material

3. Morphable Tip Method:

Have a BERP type blade tip. Its leading and trail edges have the ability top flex up together or flex down together. The upward flexing of both edges will want to pitch the BERP tip up. Because the tip is firmly attached to the blade, it will want to increase the pitch on the outward portion of the blade's span. Conversely, the outer span of the blade could have its pitch decrease buy flexing both the leading and trailing edges of the tip downward.

The above method might provide enough force to change the tip pitch, or this idea may simply assist with a physical means of varying the tip pitch.

It should be noted that the changing velocity of the tip will affect the pitch changing force.

Related Information?: Have not read either yet.

Wind-tunnel research comparing lateral control devices, particularly at high angles of attack IV : floating tip ailerons on rectangular wings , NACA Report 424 , 1933 , pp. 23 ~ http://naca.larc.nasa.gov/reports/1933/naca-report-424/

Have Wind tunnel research comparing lateral control devices, particularly at high angles of attack XI : various floating tip ailerons on both rectangular and tapered wings ~ Weick, Fred E Harris, Thomas A ~NACA TN-458 ~ May 1933 ~ http://naca.larc.nasa.gov/reports/1933/naca-tn-458/

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Initially displayed: April 17, 2003~ Last Revised: May 27, 2005

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