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hotzenplotz
31st Oct 2006, 15:53
Sikorsky Validates 4th Generation Rotor Blade Concept

Oct. 30, 2006 - STRATFORD, Conn. - Sikorsky Aircraft has submitted better than projected performance test results of its latest testing on the 4th generation rotor blade to the US Marine Corps. Sikorsky is a subsidiary of United Technologies Corp. (NYSE:UTX).

The 4th Generation™ blade follows in a long chain of innovations in the area of rotor systems. It builds on the work done for Sikorsky's state-of-the-art Growth Rotor Blade (GRB™) currently used on the UH-60M and S/H-92™ helicopter in a long chain of innovation in the area of rotor systems. The CH-53K model wind tunnel testing performed late this summer has shown a significant improvement in forward flight efficiency over the GRB. Earlier in the year, similar model rotor hover testing indicated large gains in hover efficiency. Together, the two tests further validate the large investments that Sikorsky has made in 4th Generation blade aerodynamics.

"This is tremendous improvement in the rotor system. The performance of the advanced blade compared to our current technology translates directly into increased payload range. For example, based on model rotor test results, we expect range improvements of up to 90 nautical miles over the GRB blade for similar S-92A applications. Also, for certain hot-high conditions, the aircraft Max Cruise Speed will increase from 135 knots to 146 knots," said Bob Moffitt, Sikorsky's Manager of Flight Sciences and a 38-year veteran in rotor system design.

Currently used by the US Marine Corps, the three-engine Sikorsky CH-53E SUPER STALLION™ helicopter is the largest, most powerful marinized helicopter in the world. It is deployed from Marine Corps amphibious assault ships to transport personnel and equipment, and to carry external (sling) loads.

The CH-53K will maintain virtually the same footprint as the CH-53E, but will nearly double the payload to 27,000 pounds over 110 nautical miles under "hot high" ambient conditions. The CH-53K's maximum gross weight will increase to 84,700 pounds versus 73,000 pounds for the CH-53E.

The upgrades slated for the CH-53K including the 4th Generation, high-efficiency rotor blade are: joint interoperable glass cockpit fly-by-wire flight controls; low-maintenance elastomeric rotorhead; gross weight expansion; upgraded engine system; cargo rail locking system; external cargo handling improvements and survivability enhancements; and reduced operation and support costs.

This significant improvement in technology and the efficiency of the rotor system is also directly applicable to Sikorsky's HH-92 SUPERHAWK, which it is currently offering for the United States Air Force Combat Search and Rescue Replacement (CSAR-X) program. A contract decision is expected in November.

"Our current S/H-92 blade flying on production aircraft today more than satisfies the Air Force's Block 0 requirements. We are very pleased that the 4th generation rotor blade technology that will be integrated on the future Block 10 aircraft, is already being proven today," said John Pacelli, Sikorsky's CSAR-X Senior Business Acquisition Manager. "The successes achieved to date with this technology will allow us to provide the Air Force with an even more capable, and fully risk reduced solution to meet its future mission needs."

Designed and built using rugged and proven BLACK HAWK technology, the HH-92 advanced weapons system offers the best combination of survivability, performance, interoperability, safety and cost for the vital CSAR-X mission.

The Canadian government has contracted for 28 H-92 helicopters, designated the CH-148 Cyclone, to conduct a variety of missions including search and rescue, passenger and cargo transfer, medical evacuations and tactical transport. http://www.sikorsky.com/details/0,9602,CLI1_DIV69_ETI2379,00.html

Graviman
2nd Nov 2006, 16:50
Anyone know what this 4th generation rotor technology actually is?

Since CH-53K is fly-by-wire, and has elastomeric bearings i will hazard a guess: 4th generation involves either the use of accelerometers in the control system to minimise vibration, or uses a computer prediction to generate higher harmonic control. These accels would be vertical for collective, and pitch & roll for cyclic. By having a smoother helicopter, it means blades are producing less turbulence so offer higher efficiency.

The blades are likely to have a higher effective hinge offset than the CH-53E too. This means that variable Nr, increasing with airspeed, will be on the menu. It's also not inconcievable that the carbon fiber layup has been developed to allow torsional compliance, allowing tips to force nearer optimum twist in both hover and high speed. Smart fellas...

Any other thoughts?

Mart

i4iq
2nd Nov 2006, 17:40
Anyone know what this 4th generation rotor technology actually is?

Since CH-53K is fly-by-wire, and has elastomeric bearings i will hazard a guess: 4th generation involves either the use of accelerometers in the control system to minimise vibration, or uses a computer prediction to generate higher harmonic control. These accels would be vertical for collective, and pitch & roll for cyclic. By having a smoother helicopter, it means blades are producing less turbulence so offer higher efficiency.

The blades are likely to have a higher effective hinge offset than the CH-53E too. This means that variable Nr, increasing with airspeed, will be on the menu. It's also not inconcievable that the carbon fiber layup has been developed to allow torsional compliance, allowing tips to force nearer optimum twist in both hover and high speed. Smart fellas...

Any other thoughts?

Mart

I was thinking something along these lines...

"Mac's recent work has involved the use of shape memory actuators for new concepts in lock nuts, the use of shape memory rings to control the tip clearance in the compressor section of gas turbines, and the application of shape memory torsion devices as the control element in helicopter "smart" rotor blades."

Article can be found here:

http://www.intota.com/viewbio.asp?bioID=603188&perID=108301&strQuery=shape%2Dmemory+plastic

Ian Corrigible
2nd Nov 2006, 17:59
Anyone know what this 4th generation rotor technology actually is?
SAC's previous comments on its 4th-gen blades have indicated that they'll incorporate a multi-angled 'cathedral' swept tapered tip design. This technology was originally supposed to have been utilized for the 53K, but recent CGIs of the type have lacked this feature.

I/C

Dave_Jackson
2nd Nov 2006, 18:19
Mart, you ask;
"Anyone know what this 4th generation rotor technology actually is?"The Press Release is only 3 days old, and ["4th Generation Rotor Blade Concept"] already lists 597 sites on Goggle. One 'known' is that the blade moves 'hot air'. :)

Seriously, From the press release; "The 4th Generation .... builds on .... Sikorsky's .... Growth Rotor Blade (GRB™)." Some information on the GRB. (http://halfdome.arc.nasa.gov/publications/files/Bousman_AHS02.pdf) This GRB blade has also been referred to as the Wide Chord Blade (WCB). As you know, the advantage of a wide chord is currently being discussed on another PPRuNe thread.


Dave

Graviman
2nd Nov 2006, 20:27
I was thinking something along these lines...

If Big Sky are already putting these techniques into production then they are megasmart fellas! I take it shape memory devices use current to control their temp? This would mean the blades adjust twist for different airspeeds & climb rates. We are not talking full azimuth dependent twist yet.


This GRB blade has also been referred to as the Wide Chord Blade (WCB). As you know, the advantage of a wide chord is currently being discussed on another PPRuNe thread.


Dave, i'm still not seeing how a wide chord blade benefits a rotorcraft. As Nick comments, blades work best when running just below stall (also my conclusion looking up 0012 performance curves). Variable Nr helps to achieve this condition for retreating blade across the flight envelope, while counterrotating avoids the constraints imposed by the retreating side.

This means that blades operating at high pitch are the way to go. The drag "bucket" produced by laminar flow aerofoils of high camber can improve lift/drag, until insect splatter and wear upsets the laminar flow. What am i missing in your simulations? :confused:

BTW any chance you could email a copy of the Prouty's 'Combined Momentum and Blade Element Theory with Empirical Corrections' simulation? It looks pretty useful. :ok:

Mart

Dave_Jackson
2nd Nov 2006, 22:18
Mart,

This has been commented on, in the other thread.
~ Nick is 100% correct, when discussing current rotorcraft.
~ Wider chords will be an essential part of future high speed rotorcraft. The wider chord is not optimal for hover, but, it is essential for significantly faster forward flight.

As you know, rotors must be slowed in forward flight so that the advancing tip does not brake the sound-barrier 5 or 6 time a second. Centrifugal force is significantly reduced on these slowed rotors, therefor additional strengthening is required. Hence a smaller aspect ratio.

Low tip speed and wide chord is explained in this book;

http://www.unicopter.com/Image60.gif

Alternatively, let's wait and see the specs on Sikorsky's X2 blade.


Prouty's 'Combined Momentum and Blade Element Theory with Empirical Corrections' is on pages 69-72 of his major book, which you appear to have. This information was integrated with other data and programs in a large Microsoft Access database. Unfortunately, there is no simple way of extracting it.

Dave

Graviman
3rd Nov 2006, 10:41
Low tip speed and wide chord is explained in this book;

Right got it - apologies Dave. I thought you were trying to justify lower pitch, but am completely agreed with you about lower tip speed for counterrotators. Naturally this then requires Wide Chord Blades, still operating just below stall (with margin for manouvre).

Since CH-53K is conventional i imagine it not to have GRB/WCB, but yes X2 probably does.


This information was integrated with other data and programs in a large Microsoft Access database. Unfortunately, there is no simple way of extracting it.

Shame, it looks like a nice bit of homework. At some point i'll probably Excel-ise Prouty's Combined Momentum and Blade Element Theory.

Mart