1487

Item 1487

OTHER: Helicopter - Inside - Single Rotor - Rotor X Wing - Random Notes:

Unsymmetrical Blades:

There is the consideration that the blades need not be symmetrical. If the were unsymmetrical it could be arrainged that the rotor stopped for cruise with the all blades the correct way up. This might cause a vibration problem in hover but perhaps something could be done to minimize it.

Thicker Blades:

In cruse the flow across the blade will be at 45º off of the chord line. This will cause the airflow to act as if it was flowing about a thinner but larger airfoil then it actually is. This means that the spar can be larger and the blade can be thicker. During hover the airflow will be parrallel the the chord.

Wide Chord ~ Low Tip Speed Rotor:

This will for a larger area at the spar and the lower speed will mean that centrifugal forces will be lower and cyclical speed of the device(s) in the blades will be slower.

Undercambered Airfoil;

This may allow the spar (pitch axis) to be located at 0.5 C. See; Sharp Leading & Trailing Edges Near Blade Root ~ Undercamber

Somewhat Related Craft:

Sikorsky S-72 X-Wing:

Sikorsky S-72 X-Wing
X-Wing

Notes:

"Instead of controlling lift by twisting its blades as more conventional helicopters do, the craft used compressed air fed from the engines and expelled from its blades to generate a virtual wing surface, similar to blown flaps on a conventional platform. Computerized valves made sure the compressed air came from the correct edge of the rotor, the correct edge changing as the rotor rotated." ~ Wikipedia

S-72 was built to flight test experimental rotor systems that would not, by themselves, support the aircraft's weight.

My understanding is that the craft never flew with the X-wing

Canard-Rotor-Wing (CRW) ~ Boeing_X-50:

More information from an outside web site

Both of the experimental craft crashed.

OTHER: Helicopter - Outside - Single (large) - Sikorsky's Reverse Velocity Rotorcraft Proposal

Sikorsky S-61F / NH-3 1965:

A craft with a pivoting tail rotor that was experimental. It was a compound with wings.

PPRuNe, Toolguy ~ It was a highly modified S61 that had a pivoting tail rotor gear box mechanism that could swing 90 degrees form normal position into a pusher prop. I have a picture of it, but no means to scan it. My guess is that the flapping loads on the spindles and stops was pretty high in the pusher mode, but it never caught on.

PPRuNe, NL ~ It was flown extensively back in about 1970, as a modification to the experimental S-61F test bed aircraft, which was flown to explore all kinds of high speed concepts, such as jet compounding, lifting wings. The "swing-tail" was a moderate success, but its speed gain was modest, and its weight and cost never justified itself, I think.

A picture of it can be found at Vertiflite ~ Summer 06 - page 48

General Comparison with the Sikorsky S-72 X-Wing:

Concern about the S-72 X-Wing: The blade at 270º azimuth will loose all lift when the craft's tip speed ratio [mu] is near 0.7. This is because the lift on the outer advancing portion of the blade will be offset by the negative lift on the inner portion, which is subjected to reverse velocity.

Idea: Perhaps the ducting of the air out of the blade could be segmented along the span of the blade so that the blade is able to work with air coming at it from both directions. In addition the wing located under the retreating blade will provide lift.

This Rotor-X-Wing concept has the advantage of having a conventional airfoil, which is optimized for airflow from one direction only. This is true when the blade is experiencing airflow from either side, due to its ability to twist 180º.

This Rotor-X-Wing concept has the disadvantage in that the twist results in a pair of blades that both have a small aspect ratio. In addition, the airspeed over this 'double blade' is quite slow.

As with the S-72 X-wing, the blades at 180º and 360º will be carrying a portion of the load. However, the lift of the blade at 90º must be reduced so that the lateral symmetry of lift is maintained.

Outside information:

The Effects of Aeroelastic Deformation on the Unaugmented Stopped-Rotor Dynamics of an X-Wing Aircraft Have hard copy.

Introduction of the M-85 High-Speed Rotorcraft Concept ~ Stroub, NASA Technical Memorandum 102871, Located in E-drive. Have hard copy.

Low-speed wind-tunnel test of an unpowered high-speed stoppable rotor concept in fixed-wing mode. (An experimental investigation of the M85, a High Speed Rotor Concept) Located in E-drive.

Related Subjects at this Web Site:

OTHER: Rotor Concept - Reverse Velocity Utilization

OTHER: Rotor Concept - Reverse Velocity Utilization - Sharp Leading & Trailing Edges Near Blade Root

OTHER: Rotor Concept - Reverse Velocity Utilization - Traversing Root Pitch Axis

DESIGN: UniCopter ~ Rotor - Disk - Advancing Blade Concept (ABC)
UniCopter - UAV

Patent and Patent Application Search:

Search on "stopped rotor" AND (rotorcraft OR helicopter OR VTOL OR rotary-wing) The following may be of little interest.

US 7,434,763, Rotor/wing dual mode hub fairing system

US 5,405,104, Stopped rotor aircraft utilizing a flipped airfoil X-wing

Initially displayed: September 21, 2004 ~ Displayed on PPRuNe and on Rotary Wing Forum: April 9, 2006 ~ Last Revision: August 18, 2009

The above application of reverse velocity utilization in the main rotor(s) of a helicopter is openly and publicly disclosed on the Internet to negate an entity from patenting it, to the exclusion of all others whom may wish to use it. ~ Reference patent law 35 U.S.C. 102 A person shall be entitled to a patent unless - (a) the invention was known ... by others in this country, ..., before the invention thereof by the applicant for patent.