Sikorsky's Experimental Aircraft

[SASless]

Saw this today.....interesting concepts but I am sure there are some issues to be worked through with such new concepts.


https://www.defensenews.com/land/2020/02/20/defiant-raider-and-sara-fly-together-in-first-public-demo/

[Ascend Charlie]

The bait is out there, waiting for Sultan to leap in........

[The Sultan]

AC,

The article says it all. Neither design exhibited performance exceeding that of traditional helicopters which are cheaper and do not have the risk of the rotors colliding in aggressive maneuvers.

[SASless]

Dang....you can't keep the pin fish off the line long enough to land a trophy!

[IFMU]

Cool videos - thanks for the post!

[SansAnhedral]

such new concepts.

https://books.google.com/books?id=FzCnbu4xM0YC&lpg=PA1&pg=PA68#v=onepage&q&f=false

[Lonewolf_50]

Saw this today.....interesting concepts but I am sure there are some issues to be worked through with such new concepts.


https://www.defensenews.com/land/2020/02/20/defiant-raider-and-sara-fly-together-in-first-public-demo/
The only two vids I saw were Raider and Defiant.
Was there a SARA video as well?
FWIW, the Army had an actual UH-60 Blackhawk flying about using a remote control kit a few years ago.
Part of an R&D effort, but I don't know what became of it.

[SASless]

Sans....I was at West Palm Beach back when the ABC was flying.....that is where I first met Nick Lappos who was one of the Test Pilots.....that was back in 1979 or so.

If Sultan can claim the V-22 as new concepts despite all that went before it clear back to the 1950's.....I would suggest you can give me pass on this.

The ABC did not have a pusher prop.....that came from Piasecki which had that on a Blackhawk airframe a few years back.

[Al M]

It did have a couple of J60's.

[SASless]

Externally mounted and independent of the Transmission system too.....unlike the Pusher Prop.

[Al M]

Yes. They were left over from the S-61F (NH-3A) and were available. There was talk at the time that a prop would be desirable.

[SansAnhedral]

Sans....I was at West Palm Beach back when the ABC was flying.....that is where I first met Nick Lappos who was one of the Test Pilots.....that was back in 1979 or so.

If Sultan can claim the V-22 as new concepts despite all that went before it clear back to the 1950's.....I would suggest you can give me pass on this.

The ABC did not have a pusher prop.....that came from Piasecki which had that on a Blackhawk airframe a few years back.

Notice in that PopSci article the illustration on page 70. XH-59B was supposed to have that ducted pusher, dreamed up all the way back in the late 1960s. After seeing the A model in action, the Army was uninterested in pursuing the concept further.

As far as the rigid rotor coax in general? The Hiller boys were way ahead of the curve in '45 (and apparently the X2 moniker as well)

http://www.aerofiles.com/hiller-x2235.jpg

[SASless]

Progress in the helicopter world is an interesting tale.

Think back to the Cessna single piston engine "Sky Hook" that was certified for IFR flight by the FAA a very long time ago... and where are we today on that?


Collect Air (http://collectair.org/cessna.html)

[JohnDixson]

Sikorsky can successfully argue that they flew a pusher tail-prop long before the Piasecki pusher. Recall the Roto-Prop testing on an S-61A in the mid 1960’s. Pics are in the SA archives.

[roscoe1]

Deleted, entered in error

[rrekn]

https://cimg8.ibsrv.net/gimg/pprune.org-vbulletin/551x456/s_66_x_5_9c29fcd942b42de53f938a5759cd3ee15bb1430b.jpg

More details available at: https://www.sikorskyarchives.com/S-66%20AAFSS.php

[PDR1]

Or Lockheed with the AH56 Cheyenne.

PDR

[JohnDixson]

Thanks,rrekn,that pic reminded of something: one of the plans for the S-67 future,was to reinstall the fenestron tail we had already flown on it,but adding both a controllable rudder and a declutch mechanism for the fenestron rotor.

Historical note re the S-67 fenestron. The highest speed I see quoted for the 67 happened by coincicidence with the fenestron test program.The high speed limit was 200 Kias but on that day ( it was winter, cold and somewhat turbulent due to a just passed cold front ) we did it around 6000 ft and were watching the tip path closely, remembering that the standard rotor on the S-61F had gone unstable at a Mtip of .94 ( freestream ). That day the 200 KIAS resulted in a freestream Mtip of .96 and without any rotor stability issue.

[SplineDrive]

Thanks,rrekn,that pic reminded of something: one of the plans for the S-67 future,was to reinstall the fenestron tail we had already flown on it,but adding both a controllable rudder and a declutch mechanism for the fenestron rotor.

Historical note re the S-67 fenestron. The highest speed I see quoted for the 67 happened by coincicidence with the fenestron test program.The high speed limit was 200 Kias but on that day ( it was winter, cold and somewhat turbulent due to a just passed cold front ) we did it around 6000 ft and were watching the tip path closely, remembering that the standard rotor on the S-61F had gone unstable at a Mtip of .94 ( freestream ). That day the 200 KIAS resulted in a freestream Mtip of .96 and without any rotor stability issue.

I've always liked the S-67 and I think Bell did a good job hitting it with the "shrink ray" with the Model 360... not an unreasonable configuration for the mission. Did the S-67 have the ability to slow down the rotor rpm to control tip speed? Or at ~200 knots, was it at the limits of the system's ability to do so?

[JohnDixson]

Spline Drive the Bell 360 looks exactly like the Boeing-Sikorsky RAH-66, very different from the S-67. It had GE T-58-5 engines and the NR could be controlled thru a limited range.Now, the Sikorsky S-97 Raider and Defiant have a broader capability in that area, necessitated by the increased speed capability. Running a rotor up near free stream Mach one creates a real noise issue. We did run a short test program one time,at the request of the Army,to evaluate the UH-60 up to a free stream Mtip of 1.0,and the rotor was stable at that condition. Was not a stealthy audible situation however.

[SplineDrive]

John, I do recognize the obvious similarity between the Model 360 and RAH-66, but in particular I was referring to an aerodynamically significant wing on both the M360 and S-67. The S-67 wing was quite large and I assume could offload the main rotor in high speed flight so that the rotor could still be effective at producing horizontal force at a lower thrust level at high Mu. The M360 doesn’t look quite as significant but the renderings make it look more purposeful than simply as weapon storage and I assume rotor offload is part of how it will cruise at the claimed 185 knots. RAH-66 obviously looks similar but that’s a distinct difference.

Thanks for the info on the S-67 rotor rpm, I suspected that might be the case.

[SASless]

Was not a stealthy audible situation however.

Bah! What's this youngest generation coming to....acoustic stealth!




https://www.youtube.com/watch?v=CdmG7eQXJEc

[IFMU]

Bah! What's this youngest generation coming to....acoustic stealth!


I had not realized John Dixson was a millennial!

[JohnDixson]

SD, some further comment re the 67 and wings on helicopters. NASA commissioned a maneuverability test program on the S-67, to include maximum G capability, wings on and wings off. We were a bit surprised that the G advantage with wings ON was less than some aerodynamic predictions. They add extra weight, and they produce vertical drag thus reducing hover performance, thus for any new design, there are puts and takes to weigh ( no pun ) before deciding.

As for responding to the subject of acoustic stealth to SAS and IFMU,I cannot. Other than my lovely spouse accusing me ( correctly so ) of having very selective hearing,I am deaf on the subject.

[SansAnhedral]

Spline Drive the Bell 360 looks exactly like the Boeing-Sikorsky RAH-66, very different from the S-67.

I see this repeated ad nauseum.....and it really makes absolutely no sense. If you actually look at 3-views of the RAH-66 and 360 they look almost nothing alike outside of the fenestron assembly and the fact that it has a chine.

The 360 is far closer to a Z-10+Z-19 or a Tiger in overall shape.

https://i.ibb.co/KbYdQ6z/Untitled.png

[henra]

The 360 is far closer to a Z-10+Z-19 or a Tiger in overall shape

Just a bit nitpicking but your last picture shows an Agusta A-129 Mangusta, not a Tiger

[SASless]

Brother Dixson got to do some very interesting flying at Sikorsky.

I am thinking he knows a thing or two about the S-67.

The lucky Sod!


Sikorsky S-67 helicopter - development history, photos, technical data (http://www.aviastar.org/helicopters_eng/sik_s-67.php)

[SansAnhedral]

Just a bit nitpicking but your last picture shows an Agusta A-129 Mangusta, not a Tiger

I couldn't find a decent 3D silhouette of the Tiger that matched the rest, but the AW was even closer with its slightly lower pylon

[noneofyourbusiness]

deleted for being stupid.

[rotormatic]

Sikorsky X2 - T800 engine, free power turbine
Sikorsky Raider - T700 engine, direct drive from engine to rotor
Sikorsky/Boeing Defiant - T55 engine, free power turbine
Sikorsky Raider X - new GE single spool engine, direct drive

Conclusion - Sikorsky Raider and Raider X will never fly fast, because they lose the slowed rotor technology with a single spool engine. X2 and SB-1 have free power turbines, so the drive to the rotor is decoupled from the engine central shaft.

Single spool engines refers to the gas producer section of the engine, and does not effect the power turbine section. Still a free turbine engine....

https://www.geaviation.com/sites/default/files/single-vs-dual-spool.pdf

[noneofyourbusiness]

You are correct. The dual spool P&W/Honeywell engine would allow for better performance at a reduced power turbine speed.

[SplineDrive]

Sikorsky X2 - T800 engine, free power turbine
Sikorsky Raider - T700 engine, direct drive from engine to rotor
Sikorsky/Boeing Defiant - T55 engine, free power turbine
Sikorsky Raider X - new GE single spool engine, direct drive

Conclusion - Sikorsky Raider and Raider X will never fly fast, because they lose the slowed rotor technology with a single spool engine. X2 and SB-1 have free power turbines, so the drive to the rotor is decoupled from the engine central shaft.

Since all of the FARA competitors are using the new GE ITE engine, are you saying none of them will use variable rotor rpm to avoid advancing blade Mach effects?

[noneofyourbusiness]

Since all of the FARA competitors are using the new GE ITE engine, are you saying none of them will use variable rotor rpm to avoid advancing blade Mach effects?

I said I was wrong. Although the competitors engine would have been a better choice. Karem has unique speed reduction technology.

[JohnDixson]

The OEM producing a Nr command as a fn of speed/alt/temperature is a relatively trivial task. The main point is having an engine whose control system produces all the engine limiting and stall-free transient response characteristics throughout the Nr range required by the rotor/aircraft. That can be anything but trivial.