Rotorcraft Composite Hubs?

[Rotor Interest]

Does anyone know if there are manufacturers of composite rotor hubs, except for Bell? Looks like Bell has developed them for the H-1, but are there other rotorcraft with all composite rotor hubs, and does Bell supply these as well?

[JDHelicopterPilot]

EuroCopter has what is called a star flex on their Astar. It is basically fiberglass.

[Rotor Interest]

Thanks JD. Is the term "fiberglass" synonymous with the term "composites", when it comes to aircraft/rotorcraft components?

[JDHelicopterPilot]

Never really thought about that. I don't really know. Just that the star flex is not your typical hub you would see.

[RkyMtnHI]

I have a timed out Starflex in my office and can post a photo of it if you like..

[ridethisbike]

I would like to see that very much, por favor.

[Rotor Interest]

Yea, that would be great. Thanks.

[Wally]

Thanks JD. Is the term "fiberglass" synonymous with the term "composites", when it comes to aircraft/rotorcraft components?

 

"Composite" is generic to describe combination materials substituted for conventional metallic construction. It used to describe the 'rubber'/stainless steel' sandwiches replacing dampers and other bearings, carbon fiber, fiber glass and various other structural materials. The idea is that by carefully combining materials with different properties in light of end engineering requirements one eliminates some of the drawbacks of metallic parts.

Never heard described as such, but the Dehavilland Mosquito of WW II is an outstanding example of a composite use- plywood.

[RkyMtnHI]

Here ya go..

 

[iChris]

Does anyone know if there are manufacturers of composite rotor hubs, except for Bell? Looks like Bell has developed them for the H-1, but are there other rotorcraft with all composite rotor hubs, and does Bell supply these as well?

 

 

Soft-in-plane rotor system. What? - Started by SBuzzkill, Jan 21 2011

 

 

As stated in the above post, the most notable is Aerospatiale/Eurocopter with the AS350 Astar, AS365N Dauphin 2, and EC 155B. MD helicopters is also in the running with the MD900N with a composite flexbeam main rotor hub that replaces the normal hinges with a fiberglass/epoxy flexbeam that twists and bends to accommodate the blade motions.

 

Other companies have undertaken composite hub programs in experimental design such as Sikorsky, Lockheed, United Technologies Corporation, Costruzioni Aereonautiche Giovanni Agusta, and Messerschmitt-Bölkow-Blohm (MBB)/Boeing to name a few. The first structural components made of composites were fiberglass rotor blades pioneered by MBB in West Germany in the early 1960s

 

The Sikorsky/Army project looked into composites for the H-60 Advanced Composite Rotor Preliminary Design. The following were some of the design goals:

 

1. Make maximum use of existing BLACK HAWK rotor head components.

 

2. Achieve an acquisition cost savings of 25% and an overall reduction in life-cycle costs.

 

3. Obtain a 15% reduction in weight.

 

4. Obtain a 98% reduction in radar cross section in the 5 to 15 GHz radar frequency range.

 

5. Improve the damage tolerance as compared to a titanium hub and design the hub to be field repairable for external damage.

 

6. Design the hub so that no in-flight testing is required to track and balance when the titanium rotor hub housing is replaced with the composite and so that no in-flight tracking is required when interchanging blades on the composite hub.

 

“The new rotor system is not without its problems, however, he admits. Several rotor components are falling far short of the original 10,000hr goal. The rotor cuff, for example, must be replaced after 1,200 flight hours. The programme will redesign the cuff and yoke to improve durability. However, Hewson adds: "It remains a very high performance rotor head with very high response rates and minimal recurring maintenance." Col Harry Hewson, H-1 upgrades programme manager for the US Naval Air Systems Command

 

http://youtu.be/PaSm3cor3wg

Edited March 10, 2013 by iChris

[Wally]

Neat animation of the Starflex.

I wonder why the spherical bearings/frequency adapter (terminology? I just point and ask the mech "Is it s'posed to look like that?") at the tips of the Starflex were ommitted. The three-pointed star installed is visually continuous from the root to the blade tip via that bit.

[iChris]

Neat animation of the Starflex.

I wonder why the spherical bearings/frequency adapter (terminology? I just point and ask the mech "Is it s'posed to look like that?") at the tips of the Starflex were ommitted. The three-pointed star installed is visually continuous from the root to the blade tip via that bit.

 

You’re correct; the animation of the Starflex doesn’t show much of the Spherical Bearings. It also doesn’t show that the points of the stars fit into the Frequency Adapters.

 

click to enlarge image

 

 

 

Edited March 10, 2013 by iChris

[Rotor Interest]

Thanks to all, for the feedback!!

[Rotor Interest]

Chris, thanks a million. I spent additional time tonight looking at all those sources you referenced, that's great info. I appreciate it!

[chris pochari]

You’re correct; the animation of the Starflex doesn’t show much of the Spherical Bearings. It also doesn’t show that the points of the stars fit into the Frequency Adapters.

 

click to enlarge image

 

 

 

 

The Star flex only flaps up and doesn't lead lag right?

[Wally]

The Star flex only flaps up and doesn't lead lag right?

The Starflex allows individual blade "hunting".

[iChris]

The Star flex only flaps up and doesn't lead lag right?

 

As stated above, it’s allowed to Hunt (Drag), Flap, and Feather (Pitch change)

 

Starflex Hub Dynamics

 

Edited May 8, 2017 by iChris

[Guest pokey]

the star actually only flaps up and down, the lead/lag is absorbed by the elastomeric bearing, as is also the feathering. It is rigid in it's 'hunting' (other term for lead/lag)

[Wally]

The star itself flexes to allow vertical movement of each blade. There were cracking issues with the early Starflex arms.

 

The laminated spherical stop bearing is at the inboard end of the blade/sleeve. Sleeves are the more or less rectangular structures that extend above and below the Starflex arms from the 'hub' area to the outboard end of the Starflex arm and blade root and carry pitch change to blade. these transmit the centrifcal forces to the Starflex and move wuth the blade. The laminated is where the bearing for the pitch horn effects. Rougly cone shaped.

 

The frequency adaptor at the ourboard end of the Starflex is where the hunting/lead-lag forces are absorbed and damped. The Starflex arm ends with a ball and socket arrangement into the frequency adaptor block, this allows the blade free pitch change and the frequency adaptor absorbs/dampens only the fore and aft movement of the blade.

 

The terminology always confused me, in that the frequency adapter has a ball and socket while the sperical stop bearing is a cone...

 

Just look for worms and cracks in the laminated rubber, and PAINT on all fiberglass. Oh yeh, check the safety pins locking the blade pins.

Edited May 8, 2017 by Wally

[chris pochari]

 

As stated above, it’s allowed to Hunt (Drag), Flap, and Feather (Pitch change)

 

Starflex Hub Dynamics

 

Oh ok I guess I got confused because it said "rigid in plane drag wise"

http://imgur.com/pa8BRDX

[Guest pokey]

Oh ok I guess I got confused because it said "rigid in plane drag wise"

 

 

The star itself is rigid in plane drag and feather/wise. Once the other parts of the rotor head are added, it becomes a fully articulated rotor system that is allowed to flap, feather & lead/lag. That being said, it is also prone to ground resonance and must use some sort of landing gear damping system also.

[chris pochari]

Porcher industries is supplying a composite hub for the new H160.

[500E]

http://www.porcher-ind.com/en/news/world-s-first-carbonpeek-helicopter-rotor-hub-at-jec-world-2017_50.html