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By: 27th September 2005 at 19:36 Permalink - Edited 1st January 1970 at 01:00
-People need to stop being scared of something just because it isn't easy.
By: 27th September 2005 at 19:53 Permalink - Edited 1st January 1970 at 01:00
-People need to stop being scared of something just because it isn't easy.
If cost and development times weren't an issue, I'd agree. But unfortunately they are. It's not even clear that the Osprey is worth the money the U.S. military will pay for it, but already the army is dreaming of a bigger version.
By: 27th September 2005 at 19:54 Permalink - Edited 1st January 1970 at 01:00
-From the looks of it the "Super Chinook" looks a far more realistic proposal than the quad rotor
By: 27th September 2005 at 20:29 Permalink - Edited 1st January 1970 at 01:00
-People need to stop being scared of something just because it isn't easy.
But why do something that's hard when the easier option is good enough?
I'd go for the Advanced Tandem Rotor Helicopter (ATRH), greater capability without the hassle.
By: 28th September 2005 at 00:24 Permalink - Edited 1st January 1970 at 01:00
-I'm not necessarily in the Tilt-rotor camp. I still wonder why they didn't pursue the X-22 concept. Or maybe an X-Wing configuration (no not Star Wars for the young 'uns). Back to the X-22, you could use four F135s driving the four ducted propellers/impellers/fans whatever like they do at takeoff with the F-35 and then switch to forward flight and use jet thrust with the props feathered. As for the upscaled Chinook Boeing's had dozens of them on the drawing boards over the years and one of them almost made it to testing before it was cancelled.
By: 28th September 2005 at 08:51 Permalink - Edited 1st January 1970 at 01:00
-Are we aware of the fact, that the JHL programme is almost duplicated in the HLR programme? I see trouble on the horizon.
- Boeing (with the one hat) is touting a warmed up Chinook for the Army's JHL
- Bell/Boeing (with the other hat) clones a Quad-Osprey for the Army's JHL
- and Sikorsky squeezes the Stallion into yet another derivate for the Marines' HLR
In my view the Chinook based proposal will have to go. Never been of any use to build the Chinook and the Stallion in parallel anyway. Tribalism only it was.
I don't like the Osprey, it's massively overengineered, but propably the Quad-Osprey is the only solution (if done properly and not as a mere enlarged Osprey) to get the speed they want.
Only thing I ask is, why they didn't go all the way and use four VTOL-JSF engine modules instead of four turboprops.
By: 28th September 2005 at 18:51 Permalink - Edited 1st January 1970 at 01:00
-I don't like the Osprey, it's massively overengineered, but propably the Quad-Osprey is the only solution (if done properly and not as a mere enlarged Osprey) to get the speed they want.
Only thing I ask is, why they didn't go all the way and use four VTOL-JSF engine modules instead of four turboprops.
I would have thought that a tandem-fan power plant would be more suitable for a transport than a JSF style lift-fan.
Pic of Vought V-530 concept from French site http://prototypes.free.fr/vtol/vtol-9.htm
By: 28th September 2005 at 20:06 Permalink - Edited 1st January 1970 at 01:00
-I like that concept, SteveO.
But IMHO, it would suit more a stealthy CSAR STOVL programme than in the HLR programme.
By: 28th September 2005 at 22:36 Permalink - Edited 1st January 1970 at 01:00
-SteveO,
I love it! Straight out of Aliens! I sure hope they build that.
By: 29th September 2005 at 08:34 Permalink - Edited 1st January 1970 at 01:00
-I would have thought that a tandem-fan power plant would be more suitable for a transport than a JSF style lift-fan.
By using the VTOL-JSF-assembly they wouldn't have to design something new. Wrap a nice nacelle around it, but the front enignes on shorter wings, the aft engines on somewhat wider wings to prevent hot-gas problems.
Could vertilift about 50.000lbs and do 450kts. Wouldn't have problems with CTOL ops, and could shut down two engines in cruise or when empty.
Problems with VTOL ops on unprepared ground is an argument, heavy dust and debris, but that will be a severe problem for that Quad-Osprey concept as well.
That ducted-fan is nice but complex, and in the arrangement your drawing shows is sensitive to CoG shifts.
One of the big no-nos Bell is going to repeat on the Quad-Osprey concept as it seems, is that mechanical crosslink between the enignes on one wing. That doesn't work on the Osprey in real life, but is utter rubish on a Quad, since even if you can keep that rotor on the other side turning via this crosslink, the power will be far less than what is produced on the other wing, so you will either drop your nose or drop your ass in case of engine failure. (Can't believe they'd do a crosslink between the wing pairs, that would be ...).
By: 29th September 2005 at 17:32 Permalink - Edited 1st January 1970 at 01:00
-Distiller,
I don't think the JSF lift-fan system is suitable for a heavy transport as the lift-fan is only needed for V/STOL operations and becomes dead weight during cruise, this isn't very efficient in my opinion.
A tandem-fan or even a Pegasus type engine would provide constant power for both V/STOL and cruise without any extra fairings and doors like a lift-fan system would need.
However, I do think that a couple of JSF lift-fan systems would make a excellent powerplant for a smaller V/STOL aircraft suitable for CSAR/special operations and aircraft carrier AEW, ASW, ASuW and COD missions.
Something like this concept http://www.afapo.hq.af.mil/Presentation/Common/artcollection.cfm?MAIN_ID=2&CAT_ID=355&GROUP_ID=389&IMAGE_ID=7822
By: 29th September 2005 at 21:40 Permalink - Edited 1st January 1970 at 01:00
-Distiller and SteveO, Both of those ideas have merit, but the drawing SteveO posted shows the front fan providing forward thrust which the JSF liftfan wouldn't. Plus the SteveO Design (is there another name for it?) wouldn't need the clutch for the front fan since it's constantly in operation. Granted, it's yet to be seen if the clutch will be the achilles heel of the JSF lift fan.
Theoretically, would you need that large a conventional wing with high power jet lift? I'm thinking a typical airlifter style fuselage ~C-130 size with 2 ducted fan/swivel nozzle engines close to the fuselage on either side and a thick one piece, high camber, ovoid wing over the fuselage (If you will...picture the radome off a S-2/E-1 Tracker, but larger, slightly wider and not quite as thick)
By: 30th September 2005 at 03:57 Permalink - Edited 1st January 1970 at 01:00
-Or they could buy Mi-26s...
that's why the tandem rotor heavy Chinook doesn't fly, it merely provides a heavier payload. A better investiment is in something that flies twice as fast for the same payload (like the purpose of the quad tilt). I don't think going from the SStallion to a Mi-26 class is going to provide you a whole new set of capability in terms of lifting a specific vehicle/platform. But, if you can fly twice as fast and high for the same payload and range....that's a significant leap. As to using the powersystem of the F35...i always loved that idea. Two of those engines should provide a supersonic capable transport with a GTOW of ~100kblf. As to dead weight of the fan in forward flight...think of it this way can anything out there offer this performance? When a 747 cruises, the engines are throttled down to its most efficient settings thermodynamically, but aerodynamically that oversized fan (of any HBP) is "dead weight and drag" where something a lot smaller could've done the job better. It obvious there why it is the way it is.
By: 30th September 2005 at 07:07 Permalink - Edited 1st January 1970 at 01:00
-Personally,I think the Army would be better off with a CH-53E/X type chopper for heavy lift and some regular V-22s for medivac,EW,and Special Ops.
By: 30th September 2005 at 12:33 Permalink - Edited 1st January 1970 at 01:00
-Sikorsky JHL concepts
Sikorsky's efforts will focus on applying coaxial rotor X2 Technology for two platforms:
1. Sikorsky X2HSL (X2 Technology High Speed Lifter)
This concept looks like a C-130-style cabin with a X2 coaxial rotor and 2 Fans at the sidie. Max speed will be 245 knots.
2. Sikorsky X2C (X2 Technology Crane).
This concept is a super heavy-lift coaxial rotor crane that can cruise at 165 knots and carry up to 25 tons external. It looks unmanned.
I made a picture of those concepts in a german aircraft magazine.
By: 30th September 2005 at 15:18 Permalink - Edited 1st January 1970 at 01:00
-Distiller and SteveO, Both of those ideas have merit, but the drawing SteveO posted shows the front fan providing forward thrust which the JSF liftfan wouldn't. Plus the SteveO Design (is there another name for it?) wouldn't need the clutch for the front fan since it's constantly in operation.
It's the Vought V-530 concept from French site http://prototypes.free.fr/vtol/vtol-9.htm
By: 30th September 2005 at 15:27 Permalink - Edited 1st January 1970 at 01:00
-I thought that tandem rotor and co-axial rotor helicopters were more efficient than tail rotor helicopters, as all the power goes to lifting rotors?
2. Sikorsky X2C (X2 Technology Crane).
This concept is a super heavy-lift coaxial rotor crane that can cruise at 165 knots and carry up to 25 tons external. It looks unmanned.
There are manned and unmanned versions of the crane concept.
By: 30th September 2005 at 18:58 Permalink - Edited 1st January 1970 at 01:00
-I thought that tandem rotor and co-axial rotor helicopters were more efficient than tail rotor helicopters, as all the power goes to lifting rotors?
I know that's one of the design advantages of the Kaman interlocking rotor. A relatively small helicopter with powerful engines can carry a lot of weight.
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By: fightingirish - 27th September 2005 at 19:29
I presume, the Advanced Tandem Rotor Helicopter (ATRH) would be the better solution for the US Army.
After the V-22, how much more problems would a QuadTiltrotor have?!
The QTR-concept has no T-Tail anymore.
Source: Boeing.com - Boeing receives two study contracts from U.S. Army for Joint Heavy Lift