A Chopper Prototype of Sikorsky S-97 Raider

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Helicopter technology | Chop-Chop; Strange new rotor-blade arrangements make for faster helicopters. Economist, Jun 6, 2015.
www.economist.com/news/science-a ... licopters-chop-chop

Note:
(a) "The fastest [helicopters, so far,] struggle to exceed about 320kph (200mph)—less than the cruising speed of a second-world-war-era propeller plane. * * * There are two striking things about the Sikorsky S-97 Raider. The first is its set of two rotors, mounted one on top of the other and turning in opposite directions around a central shaft—much like the radio-controlled helicopters sold in toy shops. The second is the absence of a tail rotor. In its place sits a backwards-facing 'pusher' propeller. Start with the rotors. Such a 'coaxial' arrangement has been found in a few helicopters over the years. [Take the first maker for example:] Kamov, a Russian company"
(i) coaxial rotors
en.wikipedia.org/wiki/Coaxial_rotors
(section 2.2 Dissymmetry of lift)

Read the Wiki page up to that. Then click to read the introduction and the first illustration (about advancing and retreating blades). Then come back to this (coaxial rotors) Wiki page to read section 2.2. Still you will NOT understand, unless you see a diagram next.
(ii) Jay Chandler, Advanced Rotor Designs Break Conventional Helicopter Speed Restrictions; A fast future awaits for rotorcraft with coaxial rotor systems and pusher propellers. Professional Pilot (magazine), September 12, 2012 (according to the URL),
www.propilotmag.com/archives/2012/September 12/A3_Rotor_p1.html
(A) This article discussed

Sikorsky X2 (table: First flight 2008, Retired 2011; using most of the power in forward flight for the pusher propeller rather than the rotor; With the end of development, the X2 will be followed by its first application, the S-97 Raider)  Wikipedia
(B) View the diagram (where the “potential” lift refers to a helicopter WITHOUT a swashplate) and the discussion that followed.
(C) The following is the most important part of the discussion:

“This phenomenon—termed dissymmetry of lift—is compensated for by a mechanism called a swashplate, which miraculously corrects for this and a host of other aerodynamic issues caused by a rotor system which exhibits the characteristics of a gyro—but that would require another article.

“On conventional helicopters with 1 rotor system, dissymmetry of lift is compensated for by decreasing the angle of attack (AOA) on the advancing side and increasing the AOA on the retreating side to keep the lift equal across the rotor disc in forward flight. (This has to be done, because otherwise the helicopter would roll uncommanded to the retreating blade side

(D) swashplate (aeronautics)
en.wikipedia.org/wiki/Swashplate_(aeronautics)

In section 4 Animations, pay attention to the third --and last--animation, whose caption reads, “A tilted swashplate giving cyclic blade control. Note the change in pitch of the blades during rotation.”

* blade pitch
en.wikipedia.org/wiki/Blade_pitch
(Blade pitch or simply pitch refers to turning the angle of attack of the blades of a propeller or helicopter [as well as wind turbines] rotor into or out of the wind)
(E) But, where is--or what is--the swashplate in the animation?

Marshall Brain and William Harris, How Helicopters Work. HowStuffWorks, undated.
undatedscience.howstuffworks.com/transport/flight/modern/helicopter5.htm

View the scheme only--no text: The “upper swash plate” rotates, while the “lower swash plate” stays stationary.
(F) About the etymology of "swash plate" (two words), merriam-webster.com says "fr[om]. obs[olete]. swash slanting, of unknown origin."  I am telling you, because the term is in Merriam Webster Unabridged Dictionary, which one can access for a 14-day free trial.

(b) “In forward flight an advancing blade moves faster, relative to the surrounding air, than a retreating one. That creates uneven lift that tries to roll the chopper over. To deal with the problem, helicopters can tilt the blades themselves, and thus vary the amount of lift they generate, as they spin—but only up to a point.”
(i) “In forward flight an advancing blade moves faster, relative to the surrounding air, than a retreating one.”

This statement applies to helicopters of both a single main rotor and a coaxial rotor.
(ii) The term “tilt the blades themselves” means “change angle of attack.”


(c) Sikorsky's S-97 prototype "may face competition from the V-280 Valor, which is being developed by two other American firms, Bell and Lockheed Martin. This is a smaller version of the V-22 Osprey, which is already used by American forces. Both [V-280 and V-22] are 'tilt-rotors,' which means they use rotors mounted on the end of a pair of stubby wings that tilt through 90 degrees."

See next posting.

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(1) Bell Boeing V-22 Osprey (table: First flight 1989, Introduced 2007, Primary Users  US Marine Corps and Air Force, Produced 1988–present; Number built 200+ as of 2014, Program cost $35.6 billion after planned procurement of 408 aircraft, Unit cost: $72.1 million (flyaway cost for FY2015); section 2 Design, section 2.1 Overview: [a] three-bladed proprotor [on each wing], "Composite materials make up 43% of the airframe, and the proprotor blades also use composites;"  section 2.1 Propulsion: The V-22's two Rolls-Royce AE 1107C engines [one for each proprotor] are connected by drive shafts to a common central gearbox so that one engine can power both proprotors if an engine failure occurs;  section 8 Specifications (MV-22B): a crew of four, 24 troops (seated), 32 troops (floor loaded), or 20,000 lb (9,070 kg) of internal cargo/ wingspan 14 m, height 6.73 m, empty weight: 33,140 lb (15,032 kg, maximum speed: 275 knots (509 km/h, 316 mph) at sea level / 305 kn (565 km/h; 351 mph) at 15,000 ft (4,600 m), [maximal] range: 879 nmi (1,011 mi, 1,627 km),
combat radius: 390 nmi)
en.wikipedia.org/wiki/Bell_Boeing_V-22_Osprey

Do go to the Wiki page, if only to view the TAIL, which is different from that of V-280.


(2)
(a) Bell V-280 Valor
en.wikipedia.org/wiki/Bell_V-280_Valor
(being developed by Bell Helicopter and Lockheed Martin; US Army; a projected first flight in 2017)

section 2 Design: "The V-280 is reported to be designed for a cruising speed of 280 knots (320 mph; 520 km/h), a top speed of 300 knots (350 mph; 560 km/h), a [maximal] range of 2,100 nautical miles (2,400 mi; 3,900 km), and an effective combat range of 500 to 800 nmi (580 to 920 mi; 930 to 1,480 km). Expected maximum takeoff weight is around 30,000 lb. * * * A driveshaft runs through the straight wing, allowing both prop rotors [each with its own engine] to be driven by a single engine in the event of engine loss. * * * a V-tail configuration. The wings are made of a single section of carbon fiber composite, reducing weight and production costs. The V-280 will have a crew of 4 and be capable of transporting up to 14 troops. * * * The fuselage is visually similar [in shape] to that of the UH-60 Black Hawk medium lift helicopter. * * * GE Aviation will manufacture the engines for the V-280

(b) the official website for
Bell V-280 Valor
bellv280.com/
(i) Pay attention to its “V tail.”  
(ii) Bharat Verma, Indian Defence Review. Atlanta: Lancer Publishers, 2013, page number not displayed
books.google.com/books?id=EMxoy7zuBFUC&pg=PT140&lpg=PT140&dq="V-280+Valor"+"v+tail"+difference&source=bl&ots=DoYbwJfLkO&sig=ObCDChN5i-KdxKEBB6zsJPFkSCM&hl=en&sa=X&ei=-iNzVb-8J4m9ggTm5oPgBw&ved=0CF4Q6AEwCw#v=onepage&q="V-280 Valor" "v tail" difference&f=false
(“With a V-tail configuration that will help to improve the aircraft's [V-280's] overall stability * * * The V-280 Valor stands for the following -- V = vertical; 280 for the aircraft's cruise speed and Valor as a tribute to the [military] services")
(ii) Click "DOWNLOAD  FACT SHEET" at the bottom of the home page. The fact sheet--plus “Useful load of 12,000+ lbs.” --confirms what is said in (a): cruising speed, maximal range, combat range, 4 crew and 14 troops.