Sikorsky X2 coaxial heli developments.

[IFMU]

Originally Posted by heli1

Have they actually connected the airscrew drive yet ? This was going to be the next stage as I recall ?

From aero-news network:

Sikorsky Conducts First X2 Pusher Prop Ground Runs

-- IFMU

[Graviman]

Hey, that's great news! So X2 still active.

Any flight testing intended for later on this year?

[Graviman]

Everything whirling away! Exciting times....

Thanks, CEFOSKEY. Fingers crossed there are no setbacks.

[Rigid Rotor]

Viewing the photos of the flight (which were accompanied by all of the "best ever" required comments to get the bonus) I would suggest move the pilot station to the back cockpit and use vertically challenged pilots to avoid a decap during maneuvers.

The Sultan

@The Sultan (post 333) - what sort of flapping hinge equivalent offset are we looking at ? Would it be in the region of about 50% of rotor radius given the fact that the designers appear to be sufficiently confident of seating the Chief Test Pilot so far upfront !!

Notwithstanding all that, the X-2 is definitely promising - will hopefully prove to be the long overdue bootstrap for chopper designs from its present stagnant state.

[ramen noodles]

Rigid,
You are right on, the Sultan yet again shows how little he knows about rotorcraft when he applies zero-offset thinking to a high offset rotor.

He is, however, quite correct when he reminds us of the differences between demonstrated high speed capability (609) versus promised (X2).

[SASless]

How many 609's in the commercial fleet?

It one thing to talk of demonstrated speed and all that but the Sikorsky ABC already proved that long before the 609 test flights occurred.

What is the difference between the ABC and the X-2....similar concept are they not and one builds on the earlier technology?

[Dave_Jackson]

What is the difference between the ABC and the X-2....similar concept are they not and one builds on the earlier technology?

There is extremely little difference between the X2 and what was recommended at conclusion of the XH-59A ABC thirty years ago.

IMHO, the main concern for the X2 (and for the Unicopter for that matter) is the essential requirement for a blade that can obtain lift from the reverse velocity airflow region, which is greater than any resulting loss of lift from the forward velocity airflow.

The 5.300 GW X2 may achieve 250 knots with its 1,450 SHP, but 3.6 lbs / HP is far from efficient.

The V-22 is 4.3 lbs / HP.

[The Sultan]

Sasless,

You forgot the XV-15 tilt rotor demonstrator kicked the ABC to the curb 20+ years ago. What concept is in production, what concept is doing operational deployments. It sure is not the ABC.



The Sultan

[Graviman]

Guys, lets keep a nice peace-ible debate!

Both tilt-rotor and advancing-blade have their reasons for being, and fascinating history of concept development. To my mind the advantage of ABC is a very compact configuration, and the ability to autorotate from any flight regime without relying on stored hydraulic energy - i'm not sure what the system is in V-22 during transition.

Dave, are you sure about those figures? If you mean HP/lb then it makes sense. Advancing-blade should have a lower disc loading over tilt-rotor.

Both concepts will lose out to a conventional because they must carry extra mass to accomplish cruise speed. Also the blade radius, planform & twist will be suited to a higher cruise speed.

I've no problem with argueing the merits, but let X2 step up to the mark first. Another perfectly good flying machine, Space Shuttle, is being grounded because the Columbia accident review board thought it would be a good idea to force re-certification on a 30 year old design. I'd hate to see a good concept like X2 quashed because the engineers weren't given the opportunity to get everything just so...

[JohnDixson]

V-22 Height-Velocity Flight Testing

Anyone know if this testing has been completed and if the data is available?

Thanks,
John Dixson

[Dave_Jackson]

Hi CEFOSKEY,

Think control systems.

Research & Development, IMHO, is that of advancing technology. Was not the flight control system already developed for the Comanche?

The CEO of Sikorsky said that their next project is to be Individual Blade Control. Developing IBC on a test stand, then in a wind tunnel, and finally on a craft (perhaps the X2) would be R&D.

One unknown is the technique and specifics on the rotor-propulsor integration, particularly during transitioning. This may be new and interesting.


Dave

[Dave_Jackson]

Risk mitigation is still a part of things I would think.

Agreed.

However, a couple of years ago the Coaxial-ABC was Sikorsky's proposal for the Joint Heavy Lift requirement. Apparently it was rejected. Then Sikorsky changed horses and started to promote the Variable Diameter Rotor system.

With cynicism, I suspect that the X2 craft, its Design Patents, and its promotion, collectively suggest that the craft may have originated in the Marketing department and not the Engineering department.


My question and that of others has been; Assuming that the aerodynamic and aeromechanical features of the Coaxial-ABC configuration are potentially viable, why wasn't there a low-budget and low-profile continuation of research and development on the Advancing Blade Concepts during the past 30 years, since the XH-59A ABC.


Dave

[Rigid Rotor]

Any reason why the ducted pusher-prop variant XH-59B (which was a natural follow-up to the 59A) was abandoned ?
We have lost about 35 years as a result of that decision !

- And now we have even the Russians hopping onto the 'ABC boat' with their Ka-92 project -I believe that the Kamov Design Bureau has sufficient expertise in production of coaxials - they had some serious fleet reliability problems in their coaxial swashplates and linkage controls which they have largely overcome. They have progressively increased the flapping hinge offset in the Ka-50 (although as of yet nowhere near the 'true ABC' requirements). Its quite possible that they will be able to evolve their coaxial designs into the Russki ABC. In fact they have declared their intent to productionalise the ABC Ka-92 (or its derivative) by 2020.

[Ian Corrigible]

Actually the army reversed course on JHL again last time I heard.

AATD's focus is squarely on the High-Efficiency Tilt-Rotor (HETR), but the $15+ billion development cost (and $40+ billion acquisition price tag) probably represents a bigger hurdle than the technical and operational challenges. A Variable Diameter Tilt Rotor (VDTR) study was one of the 13 risk reduction studies performed using FY-08/09 drip feed funding, hence SAC's revisiting of the TRAC VDR study.

Originally Posted by Rigid Rotor

Any reason why the ducted pusher-prop variant XH-59B was abandoned?

From Ray Robb's article in AHS Vertiflite, Summer 2006: "A proposal for the development and flight test of the XH-59B was submitted to the Army, but Sikorsky’s refusal to share costs (in part due to the resource strains on the company that resulted from the simultaneous development of the UH-60 Black Hawk, SH-60 Seahawk, CH-53E Super Stallion, and civil S-76) resulted in the Army not awarding a contract. As a result, the XH-59B was never built."

I/C

[Dave_Jackson]

Rigid Rotor,

Any reason why the ducted pusher-prop variant XH-59B (which was a natural follow-up to the 59A) was abandoned ?

Here is more information related to your question.


Perhaps the larger question might be; What developmental work has Sikorsky done that was not funded by the government?

Perhaps a related question might be; Would the helicopters have been Intermeshing-ABCs if Charles Kaman had not been told "Charlie, we have our inventor at United Aircraft. His name is Igor Sikorsky. We don't need another one."

Dave

[JohnDixson]

Sikorsky Funded dDevelopment

Hello David Jackson.

I believe you wrote the following:

"Perhaps the larger question might be; What developmental work has Sikorsky done that was not funded by the government? "

My memory is far from perfect, but here are a few items that were funded with Sikorsky/UTC money:

1. S-61F. High speed reaearch aircraft with twin J-60 tourbojets. Took a basic SH-3 airframe, added a wing, ailerons, an entire new tail ( vertical and horizontal, with a rudder experiment ).
2. SH-3 Pusher tail rotor. Tail rotor/tail rotor gear box was gimbaled to rotate 90 degrees in flight so as to obtain forward propulsive thrust from the tail rotor. Incorporated a rudder.
3. S-67 Blackhawk. Took various S-61 drive components, built a totally new airframe, added a wing and horizontal stabilizer ( was a stabilator for awhile ), Incorporated wing-mounted speed brakes. Had an aerobatic envelope.
4. S-67 Fan-in-fin. Incorporated a Hamilton-Standard fenestron-fan in a new tail structure. Had a rudder but this was never fully developed.
5. S-61R. This was a company funded S-61 derivative that won the competition with the Vertol 107 for the USAF contract that turned it into the original HH-3C. But, the S-61R was a company funded design and flight tested aircraft.
6. The ABC. This one you seem to have been aware of.
7. S-60 Skycrane. A crane designed using S-56 components, but in a totally new conceptual heavy lifter.
8. S-64 Skycrane. The original S-64 was designed and flown on Sikorsky /UTC funds. By the way, that included a UTC investment in having Pratt & Whitney design and test the original JFTD-12 engines ( taking a J-60 turbojet and adding a power turbine assembly to make it a turboshaft engine ). The US Army contract came later.
9. Canted tail rotors. Company funded and originally developed and flown on a company owned S-61R.
10. S-76. All models were company funded and developed.
11. S-92. Ditto as for the S-76.
12. S-76 Fantail. Risk reduction for the Comanche Program

There is another category of development, wherein the company could bail an aircraft from the government, and then do development programs using its own money for that engineering work. I am thinking of the CH-53 IRB ( improved main rotor blade ) work and the S-70 composite blade development.

Lastly, there was some discussion about the X2 being just a version of the XH-59. Possibly so, in the same sense that the Wright Flyer and the B-777 are both airplanes. The similarity ends there, however.

Thanks,
John Dixson

[IFMU]

To add to what John said, is not the X2 Sikorsky funded? Thought I saw that in the press somewhere. The original Cypher UAV was company funded too, I believe.

-- IFMU

[Dave_Jackson]

Thanks John. Your knowledge and recollection of Sikorsky is impressive. That is quite a list.

Out of curiosity I did a little research and found this on the first item #1. "Officially listed as an HSS-2, the U.S. Navy's BuNo. 148033 was actually a Sikorsky S-61F compound research helicopter sponsored by the Army and Navy."

As to the last item, the original Cypher mentioned by IFMU was Sikorsky funded, where as with the later Cypher II Sikorsky is currently [was]under a $5.46 million contract to deliver 2 prototypes and 4 ground stations

________________________

Lastly, there was some discussion about the X2 being just a version of the XH-59. Possibly so, in the same sense that the Wright Flyer and the B-777 are both airplanes. The similarity ends there, however.

Interesting, but it misses the essence of the discussion. The discussion related to why the ABC concept was not pursued back then; and why it is [or was] being pursued now.

IMHO the esential question has always been; ~ Is the fundamental ABC concept viable, or is it not viable?

They stated very clearly back then what the aerodynamic and dynamic improvements should be and they have now incorporated them, 30 years later. Today's new abilities, to fly-by-wire, fly-by-light, or fly by mental-telepathy represent an improvement for all aircraft. They are not unique to the ABC helicopter.


Dave

[JohnDixson]

X2/ABC

As to the S-61F, I was told upon arrival at SA in 1966 that the 61F was an internally funded design. Of course there were US Gov't. funds involved later. Anyway, I have two inquiries going to former SA people who may ( or may not ) confirm my belief on that subject.

US Gov't. funding sometimes is obtained after a concept is designed and flown with internal company funding. An example not in my previous list is in that category: Two engineers, Sean O'Connor and Don Fowler, with SA money, designed an automatic sling load stabilization system in the late 60's/early 70's that we flew on a bailed CH-54A. Low density/high volume loads like mil-van type containers were always among the worst actors, stability-wise, and this system enabled the Crane to fly quite well at 70 kts with these containers, vice about 40 without the system. Thus it enabled IFR capability and a terrific safety improvement. The Army was ambivalent, but then gave some support and we did a simulation study with them to prove the systems value. End of story was that they still didn't incorporate the system in the Crane, but now the technology was in the public domain, and a few years later the system showed up down in Philadelphia on a CH-47 variant. As I recall it didn't make it to production there either.

On the subject of why the ABC was not supported thru the 80's, I confess to only knowing part of the story. I do know that there was a substantial number of the tech community at SA who favored this concept for the LHX, but I do not know the background as to why the SA/Boeing team decided on the concept that became Comanche. Obviously their assessment ( and the Army's ) was that speed wasn't of prime importance. So there wasn't a good idea of where an ABC product would fit in. At that time, the S-76 was absorbing all of our efforts in the small civil market, and while there were some who appreciated what an ABC could do in that market, the decision to build the S-76 essentially closed that opportunity. These are just my personal guesses.

I am curious, Dave: have you ever seen the ABC up close, in person?

Thanks,
John Dixson

[JohnDixson]

S-61F

Received the following note from a former collegue at SA who was in a position to know at the time:

"Not dead certain, but I do not believe so. S-61F was one of four contracts for compound and aux propulsion research issued in the mid 1960s by Ft Eustis - whatever they were calling themselves at the time. The other three were Kaman -modified UH-2A -, Lockheed - modified XH-51, and Bell 533 which was a modified YH-40 (original Huey bought under Air Force contract). I remember us being faster than Kaman but not near Lockheed and Bell. It was a real lesson in interference between wings and stub wings for the J-60s. One thing that rarely gets remembered is that the Bell machine could easily have come apart (mainly tail rotor} when they hit 300 mph. A point they never dared repeat."


I was therefore wrong in stating that the 61F was a company funded design.


Thanks,
John Dixson