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Post Info TOPIC: The X-Wing program


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Date: Jul 18, 2011
The X-Wing program
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http://www.globalsecurity.org/military/systems/aircraft/x-wing.htm

 

Vertical takeoff and landing (VTOL) and short takeoff and landing (STOL) aircraft offer the possibility for landing in and taking off from downtown areas of cities, if appropriate sites can be found at reasonable cost. Passengers on the V/STOL aircraft could be transported directly to their final destination, or to a remote airport for a flight on a subsonic or supersonic airliner. The helicopter is one example of a V/STOL aircraft, but its current speed and fuel efficiency limitations prevent economic use for routine passenger service. Efforts to improve on the basic helicopter design to provide high-speed V/STOL travel has resulted in two practical designs: the tilt-rotor and the X-wing. Both designs were in R&D for military applications with civilian certification criteria in mind.

The X-wing aircraft accomplishes vertical or short takeoff with helicopter blades, and uses the blades as an X-shaped wing when cruising. The blades must stop in order to cruise, and the conversion from takeoff to cruise configuration has not yet been mastered. If successful, the X-wing aircraft could achieve higher cruising speeds than the tilt-rotor.

The science fiction X-Wing fighter was famous in the Star Wars movies. The actual X-Wing rotor flight test project was sponsored by NASA, the Defense Advanced Research Projects Agency (DARPA), and Sikorsky Aircraft. Developers of X-Wing technology did not view the X-Wing as a replacement for either helicopters (rotor aircraft) or fixed-wing aircraft. Instead, they envisioned it as an aircraft with special enhanced capabilities to perform missions that call for the low-speed efficiency and maneuverability of helicopters combined with the high cruise speed of fixed-wing aircraft. Some such missions include air-to-air and air-to-ground tactical operations, airborne early warning, electronic intelligence, antisubmarine warfare, and search and rescue.

The X-Wing project was a joint effort of NASA-Ames, DARPA, the U.S. Army, and Sikorsky Aircraft, Stratford, Connecticut. One of the two RSRA aircraft was later modified to the X-Wing and received limited testing at Dryden. The modified X-Wing aircraft was delivered to Ames-Dryden by Sikorsky Aircraft on 25 September 1986. The X-wing concept was under development by Sikorsky Aircraft, following R&D by NASA, the Army, and Sikorsky, and as of 1986 the first flight of a demonstrator was planned for 1990.

During high-speed taxi tests at NASA's Ames-Dryden Flight Research Facility (later redesignated Dryden Flight Research Center), Edwards, California, on 4 November 1987, the vehicle made three taxi tests at speeds of up to 138 knots. On the third run, the RSRA/X-Wing lifted off the runway to a 25-foot height for about 16 seconds. This liftoff maneuver was pre-planned as an aid to evaluations for first flight. At the controls were NASA pilot G. Warren Hall and Sikorsky pilot W. Faull. Following taxi tests, initial flights in the aircraft mode without main rotors attached took place at Dryden in December 1997. Ames research pilot G. Warren Hall and Sikorsky's W. Richard Faull were the pilots.

The contract with Sikorsky ended that month, and the program ended in January 1988. The X-wing stopped rotor concept was cancelled because of its extreme complexity when it was being readied to start flight development testing. During development, analysis and testing indicated that the X-wing design encountered high transient aerodynamic loads during the conversion from rotary to fixed-wing flight. Work on the X-wing indicated that the most severe loadings occurred during the last few revolutions of the rotor when it turns relatively slowly. Under these conditions, the rotation time-scale is much smaller than that of the flow, making a sequence of steady measurements at fixed rotor azimuthal positions an efficient and viable method to measure and predict the loads.

In 1992 a low-speed wind tunnel test was completed in support of ongoing conceptual design studies of the Stopped Rotor/Disk rotorcraft concept. A one-fifth scale model was tested in the NASA Ames Low-Speed 7- by 10-Foot Wind Tunnel #1 to evaluate the low-speed cruise performance. The primary test objective was to compare performance characteristics for three possible conceptual designs of the Stopped Rotor / Disk cruise configuration: the large hub fairing (disk) alone, the disk/extended blades configuration, and the disk/conventional wing configuration. Results showed that the disk/extended blades configuration was the most efficient in low-speed cruise. Other test objecives included making parametric changes by varying the geometry of the disk and by varying the extended blade incidence angles. Studies were also conducted to examine the aerodynamic interaction between the disk and a conventional wing. An examination was made into the effects of the disk on static longitudinal stability. The wake generated by the disk impinged on a T-tail of the model and thus degraded longitudinal stability. Alternative tail geometries are required in order to improve the concept's static stability.



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Former Deputy Administrator

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Date: Jul 18, 2011
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Lockheed also had an entry in the X-Wing program. I have attached a photo of the testing rig Lockheed used to test the feasability of the X-shaped blades.



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Uhuh, so did AvPro and Bell.



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Matt L. Webber


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Sikorsky's design work on the X-wing was quite a trippy little adventure. I've seen some artist's impressions depicting X-wings with a fighter fuselage with transitional blades, and I believe some corrisponded with their efforts in the LHX stealth program.



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Sikorsky and Boeing-Vertol submission.

http://www.flightglobal.com/FlightPDFArchive/1982/1982%20-%200655.pdf



-- Edited by Pepper on Tuesday 19th of July 2011 05:28:39 AM

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Sidewinder wrote:

Sikorsky's design work on the X-wing was quite a trippy little adventure. I've seen some artist's impressions depicting X-wings with a fighter fuselage with transitional blades, and I believe some corrisponded with their efforts in the LHX stealth program.


 

"Trippy" yes, corrisponding to LHX, no. They were separate programs. The X-Wing would've failed every requirement there was, up to weight limit and stealth. You simply cannot stealth-modify this kind of configuration, which is purely for developing a high-speed configuration in a standard rotorcraft.



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Alan Dallas


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Are you sure? Because if I remember correctly, there were supposed to be 3 major classes for the LHX; utility and transport, close support and attack, and a high-speed (almost supersonic!) version incorporating NOTAR. Hughes did a take on the last, doubling with the attack role. 

The X-wing I think was one of Sikorsky's (and many others') entries into the class of high-speed vehicles, but in itself could venture from the battlefield to civil use, being an effective low-speed VTOL aircraft which could achieve what basic airliners have with higher-speed and efficiency.



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There were two, utility and attack. Hughes's little supersonic was just an idea that was rejected with Bell's BAT tilt-rotor when they changed the requirements.



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Date: Jul 19, 2011
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failcopter67 wrote:

Uhuh, so did AvPro and Bell.


 

Some of AvPro's concepts, the first from Amazon and the other is a drawing by Jens:



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Unknown civil airliner version:



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Northrop's scout-attack X-Wing can be found here:

http://stingraysrotorforum.activeboard.com/t43703465/the-lhx-program/?page=2&sort=oldestFirst



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DARPA X-Wing concept:



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Stingray wrote:
failcopter67 wrote:

Uhuh, so did AvPro and Bell.


 

Some of AvPro's concepts, the first from Amazon and the other is a drawing by Jens:


 

http://www.freeimagehosting.net/uploads/476e1aeaad.jpg

http://www.freeimagehosting.net/uploads/9a394ec7c3.gif



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Lockheed CL-1608 X-Wing flying-boat:



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failcopter67 wrote:

Uhuh, so did AvPro and Bell.


 

Not Bell, not according to Stingray's list. Sikorsky and all these others did, by the way why are we all forgetting Sikorsky's RSRA X-Wing in this thread? I wanna see some piccies of that beaut.



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https://sites.google.com/site/stingrayslistofrotorcraft/sikorsky-s-72-rsra--x-wing

wink



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...



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hannetonIII wrote:
Not Bell, not according to Stingray's list. Sikorsky and all these others did,


Agreed. I have never seen or heard of a Bell X-Wing design. Their RSRA proposal (Model 646) featured a regular type of four-blade rotor.


hannetonIII wrote:

by the way why are we all forgetting Sikorsky's RSRA X-Wing in this thread? I wanna see some piccies of that beaut.

Forgetting?? How could we possibly forget such a wonderful design? Here's some goodies for you...


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Stéphane



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Rockwell flying boat version.



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Matt L. Webber


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failcopter67 wrote:

Rockwell flying boat version.


 

Beat me to the post button. aww



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Thanks! Wow I have never seen most of these befgore!biggrin



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Stargazer2006 wrote:
hannetonIII wrote:
Not Bell, not according to Stingray's list. Sikorsky and all these others did,


Agreed. I have never seen or heard of a Bell X-Wing design. Their RSRA proposal (Model 646) featured a regular type of four-blade rotor.

 

Should we add RSRA designs here too? Because I have scans of Bell's submissions.



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Darn! Since Stingray beat me to it, I've got to provide you with something different now... How about some more pics of projected X-Wing helos from Sikorsky?



-- Edited by Stargazer2006 on Wednesday 20th of July 2011 12:07:42 AM

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Stéphane



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Is the flying-boat not a Sikorsky? Are you positive? Just put it in a series of Sikorsky projects!! I didn't even know that Rockwell had participated in that program.

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Stéphane



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Stingray wrote:
Should we add RSRA designs here too? Because I have scans of Bell's submissions.

 I don't think so. The topic is "X-Wing", not RSRA... Otherwise you may as well add any helicopter that has four blades in this topic!!!



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Stéphane



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Twice in a row someone beat someone to posting here? I find it amusing how we are all jumping to this one thread. biggrin



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Alan Dallas


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Stargazer2006 wrote:
Stingray wrote:
Should we add RSRA designs here too? Because I have scans of Bell's submissions.

 I don't think so. The topic is "X-Wing", not RSRA... Otherwise you may as well add any helicopter that has four blades in this topic!!!


 

Ah, well you see, there's where my confusion is. Sikorsky's X-Wing effort also had in mind specific RSRA requirements.



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Date: Jul 19, 2011
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Stargazer2006 wrote:

Is the flying-boat not a Sikorsky? Are you positive? Just put it in a series of Sikorsky projects!! I didn't even know that Rockwell had participated in that program.


 

According to Scott Lowther it is, unless he's steered us wrong.



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Former Deputy Administrator

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Stingray wrote:
Stargazer2006 wrote:

Is the flying-boat not a Sikorsky? Are you positive? Just put it in a series of Sikorsky projects!! I didn't even know that Rockwell had participated in that program.


 

According to Scott Lowther it is, unless he's steered us wrong.


 

Okay. Removed it from my post. And now that I come to think of it, the unidentified airliner project further up in the page is most likely to stem from the same design team:

967689?AWSAccessKeyId=1XXJBWHKN0QBQS6TGPG2&Expires=1311811200&Signature=B0z6CsaVodqdeNUCok2P%2BXSFkRU%3D



-- Edited by Stargazer2006 on Wednesday 20th of July 2011 12:11:21 AM

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Stéphane



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Stingray wrote:
Stargazer2006 wrote:
Stingray wrote:
Should we add RSRA designs here too? Because I have scans of Bell's submissions.

 I don't think so. The topic is "X-Wing", not RSRA... Otherwise you may as well add any helicopter that has four blades in this topic!!!


 

Ah, well you see, there's where my confusion is. Sikorsky's X-Wing effort also had in mind specific RSRA requirements.


 

I vote yes, as it was a key part of the X-Wing program. It was to study an aircraft designed for high-speed flight, in which it utilized stoppable rotors that acted as sort of fixed-wings.

Sikorsky's prototype was the only one ever built and flown, except it was without the rotor system designed for the X-Wing program's requirements.



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