US Joint Heavy Lift

[LowObservable]

Yasotay,
Downwash depends on context. If you want to fast-rope, perform a rescue or hook on/release a slung load, then your requirements are tighter than if you just want to land.

 

[AeroFranz]

By the way, how does Lockmart propose to power those fans? three ninety degrees shafts?!? and the high bypass ratio engines in the back are the wrong engine cycle to extract gobs of mechanical power. Never mind the one-engine inoperative scenario, and hover control devices that I can't see...
This is likely something an intern did over the summer using spare parts from other solid models. I could be wrong on the last conjecture, but you can't convince me that this concept stands a prayer of achieving VTOL.

 

[yasotay]

Yasotay,
Downwash depends on context. If you want to fast-rope, perform a rescue or hook on/release a slung load, then your requirements are tighter than if you just want to land.

I don't disagree at all but it has been a huge concern for the JHL program both for the Army (please don't pick up fist sized rocks and throw them at my troopers) and the Navy (please don't blow my sailors and aircraft into the sea).

As to how tantalizing a B-2 Stealth transport is, as a practical tactical transport, at two or three times the cost of an obscene transport sized tilt-rotor, you will never convince me. All but one service have signed onto the need for a JHL. Can you guess which one it might be.

 

[flateric]

By the way, how does Lockmart propose to power those fans? three ninety degrees shafts?!? and the high bypass ratio engines in the back are the wrong engine cycle to extract gobs of mechanical power. Never mind the one-engine inoperative scenario, and hover control devices that I can't see...
This is likely something an intern did over the summer using spare parts from other solid models. I could be wrong on the last conjecture, but you can't convince me that this concept stands a prayer of achieving VTOL.

Key words is *prototype*, *technology demonstrator*. Image source is LM

 

[F-14D]

Wednesday, April 9, 2008
"The Program Formerly Known as Joint Heavy Lift"
Say farewell to Joint Heavy Lift, the U.S. Army's aspiration to a multi-service, next-generation heavy-lifter. The program, spearheaded by the Army Aviation Technology Directorate, seems to have been overcome by requirements creep and inter-service rivalry. It was aimed at satisfying intra-theater lift requirements of the Army's Future Combat Systems. But that program's target payload ballooned, most recently from 20 to 30 tons. That, in turn, dictated an aircraft on the order of a Lockheed Martin C-130, which tread dangerously close U.S. Air Force turf. Today, briefing at the annual gathering of the Army Aviation Assn of America outside Washington, a top Army requirements official referred to "the program formerly known as Joint Heavy Lift." The new name, said Col. Rick Stockhausen, director of concepts and requirements at the Aviation Warfighting Center, is Joint Future Theater Lift. It is a concept, he added, and is looking at lifting a 28-ton payload

Hmmm

When Army was developing the HLH which became the XCH-62, it originally was a joint venture with the Marines. When deployment date got pushed further and further out and the aircraft grew so large, Marines got permission to develop their own "interim" aircraft. This was the CH-53E, which was the only thing to enter service.

Now, date of the aircraft formerly known as JLH is pushed back and the aircraft has grown way large. Marines have received permission and are developing an "interim" aircraft, the CH-53K.

Deja Vu all over again..

 

[hesham]

Hi,

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070017930_2007016664.pdf

 

[hesham]

Hi,

anther ATRH.
http://www.gizmag.com/go/4646/

 

[zbvhs]

According to what I read, JHL is dead and the services are getting together on the Joint Future Theater Lift concept. The VTOL people are, unfortunately, still wedded to the tilt rotor concept. Seems to me that, having been through a development cycle with a tilt rotor, now would be a good time to reevaluate the various VTOL heavy-lift concepts particularly the tilt wing.

The tilt rotor design for Boeing’s JCALS concept, for example, would be mechanically simpler and better performing if it was redesigned as a tilt wing configuration.

The choice of the tilt rotor configuration for advanced VTOL aircraft is the result of a prejudice that goes back to early tilt wing experiments that used high-disk-loading prop-rotors for propulsion. Since then, the tilt wing concept has been inextricably linked with high disk loading and the tilt rotor concept with low disk loading.

Those early tilt wing aircraft suffered from high noise levels and controllability problems in hover because propeller technology of the day wasn't up to the task. High disk loading required more power for hover than comparable low disk loading designs. Not surprisingly, high disk loading lost out to low disk loading, which in the evolution of things had become wedded to the tilt rotor concept.

There is no reason, however, why a tilt wing design couldn’t use low disk loading rotors like those developed for the V-22. Tilting the wing would reduce hover losses associated with the presence of the wing in the rotor downwash field. Adding wing outboard of the engine nacelles would improve range and climb performance. Technology groundwork laid down in the development of current tilt rotor aircraft would be directly applicable to a tilt wing design.

The tilt wing concept would allow designers to play with higher disk loadings and four prop-rotors instead of two. Smaller rotors would provide a better match between hover and cruise. Mechanical monstrosities like Sikorsky's variable-diameter rotor should be avoided (kiss).

Current propeller and rotor technology is considerably advanced over that available forty years ago. I think it’s time to reconsider the tilt wing concept and higher rotor disk loading for the next generation of theater lifters.

 

[yasotay]

A name change and getting two services to work together does not of necessity spell the end of a program. JHL was itself the third name for an effort the U.S. Army has been working on for at least eight years. In fact the lineage of the JHL effort goes back to the beginning of Army Aviation efforts in the 1950’s. There has been a tremendous amount of work in the last five years by the Army with the USMC, USN and SOCOM. The USAF is now coming to the table.

As to the tilt wing. At the appropriate time there will be more analytical effort on the best way to proceed, however I will tell you that it was certainly not ignored due to prejudice in the initial analytical efforts. However your discussion about disk loading was a consideration.

Personally I am excited at the idea of the JCALS concept as it provides an opportunity to meet a diverse set of mission needs with a significant amount of commonality. I am under no illusions that it is as simple as deciding which wing to slap onto a fuselage, but the economies with sub components could be a significant factor for the services, not to mention the ability to reduce overhead with the potential of commonality of components.

 

[Schorsch]

I having followed the reports in the Flight International and I agree with LowObservable on this point: a tilt-rotor of that size is not really realistic. Although technically feasible it may end as an operationally undesirable aircraft. The USAF&Army may be better off with a conventional aircraft and helicopters.
Another way to pursue may be to go for a very short take-off aircraft that gets in&out of a 1000ft strip. The technical problems are proportional to (2000ft - Required Landing Distance)².

 

[sferrin]

There's an AIAA report out there (don't have the number off the top of my head) that shows that above a certain weight things like transmissions start to become too big of a weight hit and tip-jet driven rotors become the better option.

 

[LowObservable]

Sferrin - you may be talking about a DSB report of a few years back. It's a besetting problem with large rotors - max and min tip velocity being pretty much constant (stall retreating, shock advancing) then rpm has to decline with greater size, so greater power and less rpm means more torque. Ever seen the tranny on an Mi-26? It's the size of a bloody Volkswagen.

That's where tip drives come into their own, and if you could sort out the various problems a Rotodyne-type solution might be attractive for this kind of requirement. But 30 tons, long range, high speed and VTOL are going to be expensive whatever happens.

Tilt wings have their own advantages, although Yasotay's right to mention some of the drawbacks of downwash (fist-size rocks and 100-knot blasts across the deck...). Maybe the tilt-rotor's the right compromise, but I have my doubts.

 

[mz]

A fixed wing biplane seems the most logical solution to me. Faster than a helo, still slow landing and takeoff speed and thus good short field performance, and agile on the ground because of short wingspan.

 

[F-14D]

A name change and getting two services to work together does not of necessity spell the end of a program. JHL was itself the third name for an effort the U.S. Army has been working on for at least eight years. In fact the lineage of the JHL effort goes back to the beginning of Army Aviation efforts in the 1950’s. There has been a tremendous amount of work in the last five years by the Army with the USMC, USN and SOCOM. The USAF is now coming to the table.

Personally I am excited at the idea of the JCALS concept as it provides an opportunity to meet a diverse set of mission needs with a significant amount of commonality. I am under no illusions that it is as simple as deciding which wing to slap onto a fuselage, but the economies with sub components could be a significant factor for the services, not to mention the ability to reduce overhead with the potential of commonality of components.

I too hope that we get something out of this. I, though, am not so sanguine about the Joint Future Theater Lift program, especially since it is an Air Force led program. Experience on aircraft programs tends to indicate that Air Force has its vision of its roles and missions and other services need to adapt. Maybe it'll be different this time but I have concern that with the merger of the Speed Agile requirements into this program, VTOL and other needed Army (and eventual possible USMC) capabilities will be sacrificed. USAF is demanding, stealth (In a tactical airlifter-Why?) and Mach .8 cruise (In a tactical airlifter-Why?). I'm not sure that those requirements can be affordably accommodated in an aircraft that can also do VTOL, sustained powered lift and external crane, key JHL requirements. Of course, USAF sees no need for VTOL anyway, so from their point of view this is a non-issue. There was some speculation when USAF started talking up Agile Airlifter before the JFTL merge that USAF announced those needs because they new JHL couldn't do them and that would insure they didn't have to be in a subordinate program. I have no knowledge of the veracity of those claims, but based on history I don't discount them out of hand.

The JCALS concept is an exciting one, as long as its goal is to get the maximum commonality and cost savings consistent with meeting mission requirements and not just shoehorning everyting into one size fits all. The shadow of the TFX extends all the way to today.

Keeping my fingers crossed...

 

[F-14D]

I having followed the reports in the Flight International and I agree with LowObservable on this point: a tilt-rotor of that size is not really realistic. Although technically feasible it may end as an operationally undesirable aircraft. The USAF&Army may be better off with a conventional aircraft and helicopters.
Another way to pursue may be to go for a very short take-off aircraft that gets in&out of a 1000ft strip. The technical problems are proportional to (2000ft - Required Landing Distance)².

Please expand. With the advances in blade technologies since the '80s and the development of a 15,000 shp turboshaft why would such a Tilt-Rotor be unrealistic and undesirable, as opposed to other advanced concepts. I'd agree if one was talking a V-22 scale-up, but not for a new design.


As far as Super STOL goes, I would opine that what's involved in designing and developing a C-130 or larger size craft for operating safely and repeatedly from a 305 meter strip is at least as complex as a VTOL and would lack the versatility. Also, it would be more difficult to operate, be more vulnerable to weather, not able to use as many locations, would introduce some cargo stowage and securing issues and you couldn't get as many into a given size area. But that's just me.. .

 

[F-14D]

According to what I read, JHL is dead and the services are getting together on the Joint Future Theater Lift concept. The VTOL people are, unfortunately, still wedded to the tilt rotor concept. Seems to me that, having been through a development cycle with a tilt rotor, now would be a good time to reevaluate the various VTOL heavy-lift concepts particularly the tilt wing.

The tilt rotor design for Boeing’s JCALS concept, for example, would be mechanically simpler and better performing if it was redesigned as a tilt wing configuration.

The choice of the tilt rotor configuration for advanced VTOL aircraft is the result of a prejudice that goes back to early tilt wing experiments that used high-disk-loading prop-rotors for propulsion. Since then, the tilt wing concept has been inextricably linked with high disk loading and the tilt rotor concept with low disk loading.

Those early tilt wing aircraft suffered from high noise levels and controllability problems in hover because propeller technology of the day wasn't up to the task. High disk loading required more power for hover than comparable low disk loading designs. Not surprisingly, high disk loading lost out to low disk loading, which in the evolution of things had become wedded to the tilt rotor concept.

There is no reason, however, why a tilt wing design couldn’t use low disk loading rotors like those developed for the V-22. Tilting the wing would reduce hover losses associated with the presence of the wing in the rotor downwash field. Adding wing outboard of the engine nacelles would improve range and climb performance. Technology groundwork laid down in the development of current tilt rotor aircraft would be directly applicable to a tilt wing design.

The tilt wing concept would allow designers to play with higher disk loadings and four prop-rotors instead of two. Smaller rotors would provide a better match between hover and cruise. Mechanical monstrosities like Sikorsky's variable-diameter rotor should be avoided (kiss).

Current propeller and rotor technology is considerably advanced over that available forty years ago. I think it’s time to reconsider the tilt wing concept and higher rotor disk loading for the next generation of theater lifters.

I don't think there has been that much prejudice against the Tilt-Wing, it's been studied and concepts proposed for years (Boeing's proposal for the AAFSS which became AH-56 was a Tilt-Wing). Tilt-Rotor turned out to be more successful and a better fit so far.

I suspect the higher disk loadings on Tilt-Wing earlier incarnations was a design choice based on the profiles expected of them that emphasized the cruise portion of the mission rather than the engine borne portion (that and smaller disks were closer to conventional props which were more familiar to designers). Another consideration was that the blades wouldn't impact the ground even full forward. It took quite a while for Tilt-Rotor advocates to convince people the advantage of their larger proprotors outweighed their disadvantage there. The smaller disk meant less drag in the cruise which allowed for designs that could cruise at noticeably higher speeds and with somewhat more efficiency than classic Tilt-Rotor. The powered lift portion was just for a short period at takeoff and landing. In one sense you could consider a Harrier as a powered lift aircraft with an extremely high diskloading, but it cruises really fast! On the other hand a Tilt-Rotor, while not quite as good in the hover as a conventional rotorcraft, with its lower disk loading performs better in the powered lift portion of flight than a Tilt-Wing.

The XC-142 was actually seriously consider for production, but it was decided that it didn't have the sustained powered lift performance that was needed. It's certainly true that current propeller and rotor technology is considerably advanced over that available 40 years ago, but that technology would benefit both Tilt-Wing and Rotor, so that's a wash.

The Tilt-Wing does offer the advantage of far less downwash in the hover position than a Tilt-Rotor's wing. On the other hand, you have to have fairly heavy and robust systems carried to tilt and hold not just the engines, but also the entire wing structure, a penalty not imposed on Tilt-Rotor. Further, because the entire wing tilts, I suspect fuel feed mechanisms would be more complex if you wanted to use a wet wing. Regarding wingspan for both concepts, one of the advantages of all powered lift (including the Harrier) is that you can optimize for more efficient cruise since a higher wing stall speed is acceptable since the wing won't be solely responsible for lift at the low end. Tilt-Wing also suffers from the disadvantage that during transition or enginebonre flight your have a partially or fully stalled wing, with resultant control considerations. With a Tilt-Rotor, as long as there's forward motion, there's wing lift. I don't know if there are any maneuver limitations imposed on Tilt-Wing during transition, but there aren't any of significance imposed by the Tilt-Rotor concept. And of course, when the wing's up on a Tilt-Wing, you have to deal with pushing the world's largest airbrake through the air.

I would think that the Tilt-Wing's optimum niche would be similar to that of the Harrier (but with a bigger cargo box, natch): Powered lift only for a small portion of the flight. Use the higher disk loading to get higher, more efficient cruise.

 

[LowObservable]

The ATTT in its various incarnations has been the only serious tilt-wing study in the 1990s, and was aimed at SSTOL rather than VSTOL for the reasons discussed earlier (by the time you're handling a lot of big VTOLs you've got enough space for a runway).

Historically, TWs were first explored at a point where TRs looked very dicey from the aeroelastic/vibrational standpoint. They also represent a different point on the disk-loading continuum that does, essentially, extend from the Boeing X-32, through the JSF and LockMart's fan-in-wing transports, through TRs to the TW. Better at high-speed cruise, less basically efficient in the hover.

The TR advocates have made several points. Downwash on the wing is a big penalty for the TR. The TW can also carry a bit more wingspan, which is useful in the cruise. There is also weight involved in a very stiff wing and high-torque (see above) transmissions.

On the other hand, the TW has control and control-authority issues in the transition and most designs shown to date have needed a tail rotor for pitch control, which adds weight, complexity and a critical system.

Way back in 1984 I sat down over lunch with some of the Canadair guys who had worked on the CL-84. They argued at the time that the '84 had shown equivalent performance (at least) to the XV-15, that TW was a better solution than TR and that the enthusiasm for the JVX (as it then was) was misplaced.

I think they might have had a point...

 

[F-14D]

The ATTT in its various incarnations has been the only serious tilt-wing study in the 1990s, and was aimed at SSTOL rather than VSTOL for the reasons discussed earlier (by the time you're handling a lot of big VTOLs you've got enough space for a runway).

Historically, TWs were first explored at a point where TRs looked very dicey from the aeroelastic/vibrational standpoint. They also represent a different point on the disk-loading continuum that does, essentially, extend from the Boeing X-32, through the JSF and LockMart's fan-in-wing transports, through TRs to the TW. Better at high-speed cruise, less basically efficient in the hover.

The TR advocates have made several points. Downwash on the wing is a big penalty for the TR. The TW can also carry a bit more wingspan, which is useful in the cruise. There is also weight involved in a very stiff wing and high-torque (see above) transmissions.

On the other hand, the TW has control and control-authority issues in the transition and most designs shown to date have needed a tail rotor for pitch control, which adds weight, complexity and a critical system.

Way back in 1984 I sat down over lunch with some of the Canadair guys who had worked on the CL-84. They argued at the time that the '84 had shown equivalent performance (at least) to the XV-15, that TW was a better solution than TR and that the enthusiasm for the JVX (as it then was) was misplaced.

I think they might have had a point...

I associated with some of the folks in the XV-15 program and, like their Canadian counterparts, were quite proud of their achievement. One of the things that they had to work with was that due to funding a lot of their program had to be kludged together from other aircraft which held back what they could achieve. For example, art of the landing gear from an OV-10, ejection seats borrowed from another grounded aircraft, engine tilt mechanism actually taken from the flap extension gear of a commercial airliner. In fact, the engines used were, I believe, the engines that had flown previously on the CL-84 because they were already modified and certified to operate in the vertical mode. They freely admitted that the aeroelastic issues plagued the XV-3 and weren't really solved until the XV-15

Still, it turned out the XV-15 was faster and also had more range than the CL-84, and operated better in the powered lift mode. Transition flight was simpler, as was operating the the intermediated positions (for example, for NoE). They acknowledged that downwash on the wing was always going to be a penalty for the TR. While this was somewhat compensated for by not having to divert power for an anti-torque system, like a conventional helo, that advantage went away when comparing with twin rotor helos or Tilt-Wing. As with everything, there are always tradeoffs.

As you might be able to tell, I think they made the right choice for JVX, but that's what makes a world.

 

[yasotay]

A name change and getting two services to work together does not of necessity spell the end of a program. JHL was itself the third name for an effort the U.S. Army has been working on for at least eight years. In fact the lineage of the JHL effort goes back to the beginning of Army Aviation efforts in the 1950’s. There has been a tremendous amount of work in the last five years by the Army with the USMC, USN and SOCOM. The USAF is now coming to the table.

Personally I am excited at the idea of the JCALS concept as it provides an opportunity to meet a diverse set of mission needs with a significant amount of commonality. I am under no illusions that it is as simple as deciding which wing to slap onto a fuselage, but the economies with sub components could be a significant factor for the services, not to mention the ability to reduce overhead with the potential of commonality of components.

I too hope that we get something out of this. I, though, am not so sanguine about the Joint Future Theater Lift program, especially since it is an Air Force led program. Experience on aircraft programs tends to indicate that Air Force has its vision of its roles and missions and other services need to adapt. Maybe it'll be different this time but I have concern that with the merger of the Speed Agile requirements into this program, VTOL and other needed Army (and eventual possible USMC) capabilities will be sacrificed. USAF is demanding, stealth (In a tactical airlifter-Why?) and Mach .8 cruise (In a tactical airlifter-Why?). I'm not sure that those requirements can be affordably accommodated in an aircraft that can also do VTOL, sustained powered lift and external crane, key JHL requirements. Of course, USAF sees no need for VTOL anyway, so from their point of view this is a non-issue. There was some speculation when USAF started talking up Agile Airlifter before the JFTL merge that USAF announced those needs because they new JHL couldn't do them and that would insure they didn't have to be in a subordinate program. I have no knowledge of the veracity of those claims, but based on history I don't discount them out of hand.

The JCALS concept is an exciting one, as long as its goal is to get the maximum commonality and cost savings consistent with meeting mission requirements and not just shoehorning everyting into one size fits all. The shadow of the TFX extends all the way to today.

Keeping my fingers crossed...

Your analysis is spot on. Frustration with the USAF (which is just as capable of myopia as any service) over not listening to their customer base (USAF term) has become "warm" again. Ironically it was not the Army that canned the ATT concept, they were in fact very enthused by it. USAF would have nothing to do with it. 1. complex 2. It had propellers!!! Army types surmised there was concern that that would not look good on a pilots logbook when trying for the big bucks.

Yes that last is very parochial, but "Blue" has yet to provide ANY reasoning why landing at the most documented bits of real estate in any country is not operational stupidity in the Information/Precision Weapon Age.

 

[F-14D]

Your analysis is spot on. Frustration with the USAF (which is just as capable of myopia as any service) over not listening to their customer base (USAF term) has become "warm" again. Ironically it was not the Army that canned the ATT concept, they were in fact very enthused by it. USAF would have nothing to do with it. 1. complex 2. It had propellers!!! Army types surmised there was concern that that would not look good on a pilots logbook when trying for the big bucks.

Yes that last is very parochial, but "Blue" has yet to provide ANY reasoning why landing at the most documented bits of real estate in any country is not operational stupidity in the Information/Precision Weapon Age.
[/quote]


Actually, the answer to this is quite simple and has been discussed elsewhere at this site before: If you don't have everything land at a decent-sized airfield, where are you going to put the golf course?

 

[yasotay]

Your analysis is spot on. Frustration with the USAF (which is just as capable of myopia as any service) over not listening to their customer base (USAF term) has become "warm" again. Ironically it was not the Army that canned the ATT concept, they were in fact very enthused by it. USAF would have nothing to do with it. 1. complex 2. It had propellers!!! Army types surmised there was concern that that would not look good on a pilots logbook when trying for the big bucks.

Yes that last is very parochial, but "Blue" has yet to provide ANY reasoning why landing at the most documented bits of real estate in any country is not operational stupidity in the Information/Precision Weapon Age.

Actually, the answer to this is quite simple and has been discussed elsewhere at this site before: If you don't have everything land at a decent-sized airfield, where are you going to put the golf course?
[/quote]

LOL - Army actually at one point showed how they could use a golf course as a fantastic JHL landing location. Par 5 is actually about a MOG 6. The USAF in the audience were mortified and made signs and chanted incantations at the Army as they left the room after seeing the heresy. ;D

 

[robunos]

...The USAF in the audience were mortified and made signs and chanted incantations at the Army as they left the room after seeing the heresy.

and these are the guardians of the free world... ;D

cheers,
Robin.

 

[fightingirish]

Boeing is looking at Chinook-based designs, including an almost entirely new aircraft, to meet emerging European and US requirements for a heavy-lift helicopter. A model of the Future Transport Rotorcraft study design is on show for the first time at the Eurosatory defense show in Paris this week.

Hal Rosenstein, chief engineer for advanced rotorcraft at Boeing, says that the company has been looking at Chinook derivatives since 2005, when it received one of a number of design contracts from France's DGA defense procurement agency. Initially a Franco-German initiative, the effort has not been joined by a NATO advisory group. Rosenstein also notes that the US Army is likely to need an improved Chinook-class aircraft now that its planned successor, the Joint Heavy Lift program, has turned into the much larger, 30-ton-payload Joint Future Tactical Lift project.

The design on show here represents a 13- to 15-ton payload helicopter with a large cabin; France and Germany favor internal rather than sling loading. Some of its design features, including buried engines and four-blade rotors, echo Boeing's late-1980s Model 360 demonstrator, which cruised at more than 200 knots. Possible powerplants include the GE38 from the Sikorsky CH-53K or the AE 1107 from the V-22, and Boeing is talking to potential transatlantic partners about the project. According to Rosenstein, France and Germany are planning to fund some risk-reduction efforts in the next three years.
Pic and text by Bill Sweetman

Source: Ares - A Defense Technology Blog - SuperWokka Aimed At Europe

 

[Woody]

Anyone know why nearly all of these new tilt rotor designs seam to be excused the need for a reasonably sized tail plane and/or fin? I don't see why putting big props at your wing tips suddenly gives you fantastic attitude control.

Anyway a blind man could see fan wings are the way to go, stealth, speed and range wise - just bury the engines and simplify the drive train, At least that way you could still land horizontally when something went wrong. Lets see a tilt rotor do a heavy payload STOL takeoff and landing. ;D

Cheers, Woody

 

[sferrin]

Anyone know why nearly all of these new tilt rotor designs seam to be excused the need for a reasonably sized tail plane and/or fin? I don't see why putting big props at your wing tips suddenly gives you fantastic attitude control.

You could probably get a measure of control actively using the pitch ability of the rotor blades while in forward flight.

 

[AeroFranz]

Anyway a blind man could see fan wings are the way to go, stealth, speed and range wise -

Installation of wing-buried lift fans requires relatively thick airfoils, ad allows only smaller fan diameters compared to rotors. Discloading goes up. Power required shoots through the roof as a result. Exhaust dynamic pressure becomes too high for many unprepared surfaces.
Also, the doors for the fans are a pain in the butt, they need to be really strong and add a discontinuity that increases RCS (even when closed).

 

[yasotay]

Anyway a blind man could see fan wings are the way to go, stealth, speed and range wise -

Installation of wing-buried lift fans requires relatively thick airfoils, ad allows only smaller fan diameters compared to rotors. Discloading goes up. Power required shoots through the roof as a result. Exhaust dynamic pressure becomes too high for many unprepared surfaces.
Also, the doors for the fans are a pain in the butt, they need to be really strong and add a discontinuity that increases RCS (even when closed).

Disk Loading is a significant concern with this program. As to STOL performance, the TR designs claim even better performance using STOL take off and or landing.

 

[F-14D]

Anyway a blind man could see fan wings are the way to go, stealth, speed and range wise -

Installation of wing-buried lift fans requires relatively thick airfoils, ad allows only smaller fan diameters compared to rotors. Discloading goes up. Power required shoots through the roof as a result. Exhaust dynamic pressure becomes too high for many unprepared surfaces.
Also, the doors for the fans are a pain in the butt, they need to be really strong and add a discontinuity that increases RCS (even when closed).

Disk Loading is a significant concern with this program. As to STOL performance, the TR designs claim even better performance using STOL take off and or landing.

Another issue is that fan in wing is a powered lift technology aimed at requirements that only do non-wingborne flight for limited periods at takeoff and landing. One of Army's requirements (assuming USAF doesn't kill it) is for sustained powered lift flight, something for which lift fan is not the best choice.

 

[sferrin]

Gyrodyne. If the program doesn't die the DARPA heliplane is suppose to demonstrate 400 mph flight and VTOL.

 

[yasotay]

Gyrodyne. If the program doesn't die the DARPA heliplane is suppose to demonstrate 400 mph flight and VTOL.

Indeed it might be worth looking at. Unfortunatley I read that the program is in trouble because the airframe company that was to support Groen Brothers has gone bankrupt. Think I saw that Scaled Composites has been asked to assist... that would be interesting. Also rumor that there are some technical issues as well.

 

[robunos]

Another issue is that fan in wing is a powered lift technology aimed at requirements that only do non-wingborne flight for limited periods at takeoff and landing. One of Army's requirements (assuming USAF doesn't kill it) is for sustained powered lift flight, something for which lift fan is not the best choice.

isn't this the problem with 'joint' programs? sometimes there just isn't enough common ground in the various services' requirements to make a single solution possible.
in this this case, it seems to me that the Army wants a C-130 sized V-22, whereas the AF wants a 'white world' version of 'senior citizen'.

cheers,
Robin.

 

[sferrin]

Gyrodyne. If the program doesn't die the DARPA heliplane is suppose to demonstrate 400 mph flight and VTOL.

Indeed it might be worth looking at. Unfortunatley I read that the program is in trouble because the airframe company that was to support Groen Brothers has gone bankrupt. Think I saw that Scaled Composites has been asked to assist... that would be interesting. Also rumor that there are some technical issues as well.

Eh. . .Adam Aircraft was bought up by some Russians, Groen laid off most of it's work force, but to my knowledge the Heliplane has not been cancelled. It really is a shame though because the technology is so promising.

 

[yasotay]

Gyrodyne. If the program doesn't die the DARPA heliplane is suppose to demonstrate 400 mph flight and VTOL.

Indeed it might be worth looking at. Unfortunately I read that the program is in trouble because the airframe company that was to support Groen Brothers has gone bankrupt. Think I saw that Scaled Composites has been asked to assist... that would be interesting. Also rumor that there are some technical issues as well.

Eh. . .Adam Aircraft was bought up by some Russians, Groen laid off most of it's work force, but to my knowledge the Heliplane has not been cancelled. It really is a shame though because the technology is so promising.

"IF" they have brought in Scaled Composites, then I think there is a good chance that the effort will be able to move forward. The Gyrodyne concept is very popular with some of the DARPA crowd.

 

[sferrin]

"IF" they have brought in Scaled Composites, then I think there is a good chance that the effort will be able to move forward. The Gyrodyne concept is very popular with some of the DARPA crowd.

It would certainly be better to have Scaled design an airframe specifically to the task rather than trying to use one that wasn't designed with it in mind and having to modify it. Some of the biggest Gyrodyne proponants at DARPA will soon be moving on though so. . . :-\

 

[hesham]

Hi,

Heavy Lift Replacment (HLR).
http://www.globalsecurity.org/military/systems/aircraft/hlr.htm

 

[F-14D]

Hi,

Heavy Lift Replacment (HLR).
http://www.globalsecurity.org/military/systems/aircraft/hlr.htm

That's now an ongoing program, the CH-53K
http://www.defenseindustrydaily.com/ch53k-the-us-marines-hlr-helicopter-program-updated-01724/

 

[yasotay]

Hi,

Heavy Lift Replacment (HLR).
http://www.globalsecurity.org/military/systems/aircraft/hlr.htm

That's now an ongoing program, the CH-53K
http://www.defenseindustrydaily.com/ch53k-the-us-marines-hlr-helicopter-program-updated-01724/

about 15 ton short of the JHL program. At least 5 ton if they elect to go back to 24 ton.

 

[CammNut]

Here are the official Boeing images of JCALS. The company says JCALS is its way of showing how the Army's VTOL JHL requirement and the Air Force's SSTOL AJACS requirement might be met with two versions of a common Joint Future Theater Lift (JFTL) aircraft. But it emphasises that Quad Tilt Rotor is still its solution for the VTOL requirement.

At the moment, both JHL and AJACS continue to exist as technology efforts: JHL aimed at demonstrating the viability of a VTOL solution for JFTL; and AJACS aimed at demonstrating the viability of an SSTOL solution. An analysis of alternatives is intended to decide whether JFTL is VTOL or SSTOL or, like JCALS, both. More likely it will be neither...

 

[yasotay]

The services are a ways away from agreement, although I would suspect that the Navy is more likely to fall into the Army camp (as long as it does not mean money) as the VTOL better supports the "Sea Basing" effort that the Navy/USMC are moving forward.

Personnally I think the JCAL has great merit as it gives a JSF approach to the problem. Not that that has proved to be the panecea everyone thought it would be.

 

[F-14D]

Hi,

Heavy Lift Replacment (HLR).
http://www.globalsecurity.org/military/systems/aircraft/hlr.htm

That's now an ongoing program, the CH-53K
http://www.defenseindustrydaily.com/ch53k-the-us-marines-hlr-helicopter-program-updated-01724/

about 15 ton short of the JHL program. At least 5 ton if they elect to go back to 24 ton.

The Marines know CH-53K won't meet JHL. See my post of May 07. At least they're pretty sure CH-53K will get built.