Sikorsky S-97 First Flight

There have been several articles regarding the Sikorsky S-97 Raider, which achieved first flight this week. The Sikorsky S-97 Raider prototype takes to the air for the first time

FoxtrotAlpha’s got a good backgrounder on this aircraft, its history and future.

There were some nay sayers in quite a few comments that I hit on a couple of the articles that pooh poohed the coaxial rotor as a limited solution for high speed vertol aircraft.

I think the mistake these folks have is confusing this machine with the older coaxial rotor machines like the Kamov KA-50 below (“Russian Air Force Kamov Ka-50” by Dmitriy Pichugin)

Russian Air Force Kamov Ka-50.jpg

A quick scan of the two pictures, focusing on the rotor mast and then the blades, will show you that there are a lot of differences in the aerodynamics.

Helicopters are speed limited because the blades are moving in respect to the air passing the aircraft. On one side the advancing blade adds to the air speed and at the tip can easily move towards the supersonic where air becomes in-compressible and aerodynamics change radically (which is why the blade tips on high performance helicopter blades are swept like a fighter wing) On the retreating side the blade can quickly reach stall speed and loose lift..

Coaxial rotors have the advantage of putting more energy into the air in a smaller rotor disc. Because the length of the rotor blade has a large impact on the tip speed this reduction means that the aircraft can fly faster before hitting the above limits.  Also since one blade on each side is advancing and the other retreating lift is symmetrical even if the retreating blade looses lift, meaning the aircraft can fly faster.  And indeed the X-2 demo aircraft Sikorsky built as a tech demo before the S-97 hit something like 300 miles per hour while a conventional chopper maxes out at about 150.

The principal difference between the KA50 and S-97 is the type of blade control. The S-97 has a so called rigid blade, which does not have a flapping hinge at the rotor head. The hinge is part of the  conventional blade control system allowing the blades to flutter somewhat as the lift changes through the blades rotation (you can see in the picture of the KA50 that the blades are at various incidences to the path of flight, partly because of the turn but also because of this ‘flapping.’)  The more advanced though simpler and more rugged rigid blade system on the S97 is based on advance composites and aerodynamic control theory.

So why does it matter, why do we need faster helicopters?

Simply put speed up to a certain point is always a winner because it means that for the same cargo load you can move more material in a shorter period of time. It also means you spend less time in any particular point in space which in a military context means you’re less of a target. Fast and being able to land anywhere and hover behind cover are all very interesting to the military.

Harrier jump jets

The other fast vertical take off aircraft, the jump jets like the F35 and the Harrier or the tilt rotor V22 Osbrey are really optimized for vertical take off and landing and fast transit, the jump jets have no real hover capability and the Osprey is a big and somewhat clumsy helicopter. The S97 is much more of a blended capability and its simpler and cheaper than a jump jet or tilt rotor. Sikorsky is hoping that they can convince the DoD to forgo doing too much specmaniship and competitive development and move forward with the coaxial rotor machine for the next generation of vertical lift air mobility platforms.

Of course right now the outlook for anything new is pretty bleak and Sikorsky is probably struggling to figure out where to take the technology they have developed. A typical ‘innovators dilemma the world of modern military acquisition.

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An Electric Air about them

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Flying hybrid: This two-seater electric-gas airplane may be the first of many to take to the skies

Read more at MIT TR :Once a Joke, Battery-Powered Airplanes Are Nearing Reality20130709-183958.jpg

UVa’s Sustinere design for a 50-seat jet eschews batteries in favor of a turboelectric distributed propulsion (TeDP) concept – two 2,500shp turboshaft engines under the wing generating electrical power to drive six 3,300lb-thrust fans arrayed in a duct that wraps around the upper fuselage.

Read more at AWST: Battery or Superconductor – FAA Picks Hybrid Winners20130709-184659.jpg

The EADS IW concept uses a single large turbine engine to generate electricity to power six ducted fans that provide thrust. This allows propulsive and thermal efficiency to be optimized separately. The turbine engine can be optimized for thermal efficiency (turning fuel into shaft power) while the ducted fans increase effective bypass ratio and therefore propulsion efficient (turning shaft power into thrust).

Read more at AWST : eConcept – EADS’s Hybrid-Electric Airliner20130709-185351.jpg

Two years after Honeywell and Safran announced plans to develop an electric-drive system, the team is preparing to demonstrate a proof-of-concept system on an Airbus A320 at this year’s Paris air show.

Read more at AWST : Electric Taxi Puts On A Show At Paris By Guy Norris20130709-190343.jpg

The result of close collaborations with Finmeccanica companies – Selex ES, Ansaldo Breda, and Ansaldo Energia – and partner companies from Italy, UK, U.S. and Japan, the aircraft embeds some unuque features: aesthetically pleasing styling and aerodynamically unique tiltrotor configuration; carbon graphite exterior surfaces; High-Integrity Flight Control Computer and Actuator Control Unit; custom produced electric motor inverter and motor control algorithm; axial flux permanent magnet electric motors.

Read more at : http://theaviationist.com/2013/03/21/project-zero-images/

From The ENGINEER // What a Beauty! A Bugatti designed aircraft could soon fly

The ENGINEER :In the wings: recreating the Bugatti 100P
20130629-184925.jpg20130629-184939.jpgAlmost eighty years ago aircraft design was still more art than science and what science there was revolved around slide rules and mechanical, even human, calculators, but they took chances and pushed boundaries.

This aircraft used the period’s (late ’30’s early ’40’s) advanced composite, plywood, made of hardwood and balsa wood as well as sophisticated aerodynamics to achieve a remarkable projected performance, 500 MPH, at a time when 300 was fighter fast. This aircraft had a cooling system similar to the breakthrough one in the P51 mustang, a half decade earlier, and the composites were used in the famous British strike bomber the Mosquito, also a half decade later. But the original of this remarkable aircraft never flew, being shipped out of the path of the oncoming Nazi army and ending up as decayed parts in the Experimental Aircraft Associations museum in Oshkosh WI. Now a team of enthusiasts are building a replica they expect to fly soon.

EADS eFan electric training aircraft

From: http://www.wired.com/autopia/2013/06/e-fan-electric-airplane20130619-072229.jpgA tiny ducted fan aircraft, only about 40 hp and it can do aerobatics, 1 hour touring around or about 30 min of loops etc.

People still say that battery technology is throttling eTech but I see huge amounts of work based an nano tech, material tech, graphene / carbon tech, etc which points to continued significant improvements in battery energy density etc for many years to come. Along with the rapid improvement in light strong structures, much of it fueled by carbon fibre technology, the improvements in electric propulsion, electronics, sensors, etc one wonders if the Jetsons are really all that far off…