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Boeing Vertol BV-360 or "Boeing 360"

LowObservable

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I really ought to know more about this, but we seem to have a couple of people with some rotorcraft experience around these parts, but who knows what about the Boeing 360? It seems to have been discussed here only in passing.

Some stuff from Interavia, 1987...

Because of its origins, the 360 is very similar in size, inside and out, to the CH-46. However, its engines and transmission system are based on those of the much larger CH-47 - the powerplants are commercial AL5512s - so its ultimate lifting capacity is much greater than that of the CH-46. Although design gross weight is only 30,500lb (13835kg) at 3 g, sized to the HXM mission, tests will explore its performance at weights up to 46,000lb (20865kg)....

The 360 is designed to cruise smoothly and efficiently around 200kt (370km/h), compared with a typical maximum cruise speed of 160kt (300km/h) for current helicopters. The keys to this performance are reduced drag and advanced blade aerofoil sections...

An incidental benefit of a high-speed rotor blade, with its low stalling speed (essential because the airspeed of the retreating blade falls as the helicopter goes faster, not an obvious point to fixed-wing aviators), is that rotor RPM can be reduced at low-to-moderate forward speeds. At 90kt (167km/h), for example, this can significantly reduce noise, whether one is sneaking a special-operations team over enemy lines or using a city-centre heliport...

As it starts to demonstrate its performance, the 360 will make an interesting comparison to the V-22, particularly as the helicopter shares one of the tilt-rotor's baseline missions. At a constant empty weight, Boeing engineers conclude, the tilt-rotor has a longer range and higher speed, but the helicopter has a greater payload; the productivity of the two is roughly equal, but the tilt-rotor is better for long-range missions such as ASW or special operations, while the helicopter will be the best solution for a requirement such as ACA.


How much of this potential was ever realized? (Clearly some technology made its way into Comanche.) This paper:

http://endo.sandia.gov/AIAA_MDOTC/sponsored/Tarzanian.pdf

says it achieved 210 kt in level flight. And note that it was supposed to do the CH-46 replacement mission at a gross weight that's 3,000 pounds less than the empty weight of the V-22.
 

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LowObservable said:
I really ought to know more about this, but we seem to have a couple of people with some rotorcraft experience around these parts, but who knows what about the Boeing 360? It seems to have been discussed here only in passing.

Some stuff from Interavia, 1987...

Because of its origins, the 360 is very similar in size, inside and out, to the CH-46. However, its engines and transmission system are based on those of the much larger CH-47 - the powerplants are commercial AL5512s - so its ultimate lifting capacity is much greater than that of the CH-46. Although design gross weight is only 30,500lb (13835kg) at 3 g, sized to the HXM mission, tests will explore its performance at weights up to 46,000lb (20865kg)....

The 360 is designed to cruise smoothly and efficiently around 200kt (370km/h), compared with a typical maximum cruise speed of 160kt (300km/h) for current helicopters. The keys to this performance are reduced drag and advanced blade aerofoil sections...

An incidental benefit of a high-speed rotor blade, with its low stalling speed (essential because the airspeed of the retreating blade falls as the helicopter goes faster, not an obvious point to fixed-wing aviators), is that rotor RPM can be reduced at low-to-moderate forward speeds. At 90kt (167km/h), for example, this can significantly reduce noise, whether one is sneaking a special-operations team over enemy lines or using a city-centre heliport...

As it starts to demonstrate its performance, the 360 will make an interesting comparison to the V-22, particularly as the helicopter shares one of the tilt-rotor's baseline missions. At a constant empty weight, Boeing engineers conclude, the tilt-rotor has a longer range and higher speed, but the helicopter has a greater payload; the productivity of the two is roughly equal, but the tilt-rotor is better for long-range missions such as ASW or special operations, while the helicopter will be the best solution for a requirement such as ACA.


How much of this potential was ever realized? (Clearly some technology made its way into Comanche.) This paper:

http://endo.sandia.gov/AIAA_MDOTC/sponsored/Tarzanian.pdf

says it achieved 210 kt in level flight. And note that it was supposed to do the CH-46 replacement mission at a gross weight that's 3,000 pounds less than the empty weight of the V-22.
The Boeing 360 was based on a concept that Boeing originally submitted as one of its proposals for HXM, which became JVX, which became the V-22. It got dropped early on because it couldn't meet the Marines' requirements. While the concept could do part of what a Tilt-Rotor could do, it could not do all of what a Tilt-Rotor could do. This was one of the reasons that the original proposal didn't go forward. Boeing eventually joined with Bell on the V-22 (by 1987 the V-22 program was well on its way).

In Boeing, as in many other companies there are different project teams working on different concepts, some they're quite passionate about, and in are a sense "competitors" to other internal projects. . Part of Boeing has continued ever since to try and refine and interest the world in new tandem rotor designs. In fact, one of their proposals for JHL was a tandem rotor design that owed a lot to the 360, but it was rejected because it couldn't do as much as the various Tilt-Rotor proposals (Boeing also teamed with Bell again on the Quad Tilt-Rotor proposal, which is one of the finalists) and may have been considered higher risk. In any case, by the time the 360 flew, it was way too late to be considered. I'll try and include a picture

As for the 360 being able to the CH-46 replacement mission, that depends on how you define "CH-46 replacement mission". It definitely couldn't do the JVX/V-22 mission. To draw a parallel, the F/A-18E/F is able to perform the Navy's strike and fighter missions because once the Department of Defense ordered the Navy to buy the plane, the Navy's strike and fighter missions were redefined to what the Super Hornet could do.
 

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Some of this is familiar. The 360 was designed to meet HXM when it looked as if HXM was fairly imminent (82-83). It couldn't meet JVX because JVX was written around the tilt-rotor and included lots of other missions that called for the speed and range... of course, whether the V-22 meets JVX is another question. But you are right - it was never a JVX competitor.
Boeing pursued the 360 as a demo for rotor aerodynamics - a step beyond the Model 347 - and composites. What would be interesting is how close they got to the performance that they were aiming for.
 

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LowObservable said:
Some of this is familiar. The 360 was designed to meet HXM when it looked as if HXM was fairly imminent (82-83). It couldn't meet JVX because JVX was written around the tilt-rotor and included lots of other missions that called for the speed and range... of course, whether the V-22 meets JVX is another question. But you are right - it was never a JVX competitor.
Boeing pursued the 360 as a demo for rotor aerodynamics - a step beyond the Model 347 - and composites. What would be interesting is how close they got to the performance that they were aiming for.

An earlier version of what would become the Boeing 360 was one of the proposals for HXM. It couldn't match the performance of a Tilt-Rotor, but would probably meet the USMC minimum requirements for HXM. By 82-83, though, HXM was dead as USMC requirements had been folded into US Army and USAF requirements, the result being JVX. It's not so much that JVX was written around Tilt-Rotor as much as when the JVX requirements were finalized the choice became either use a Tilt-Rotor, the only technology that could meet them, or abandon part of the mission so that other technologies could meet the reduced specifications.

As to whether V-22 meets all of JVX, it doesn't. Part of the reason was that once the Gov't specified the Allison engine, some of those performance requirements were no longer achievable. Another reason was that after four year of being a dead program (thanks to Cheney) and eight years of not being funded realistically to actually complete R&D (thanks to Clinton), the costs had risen dramatically (inflation and other reasons caused by the delay) and some requirements were eliminated n order to lower production cost and also because some were no longer deemed necessary (the ability to fly its missions in an NBC environment, for example). Even so, its doubtful that any other technology has demonstrated the ability to meet all of the present capabilities.
 

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I was watching from the bleachers, rather than being personally involved, but my sense of it was that HXM was moving (not very decisively - I don't think I ever saw Sikorsky or Bell ideas for HXM) and then the TR advocates came on board, arguing that with economies of scale, the tilt-rotor would do HXM and much more, plus the SOF, Army and Navy (SV-22 ASW) missions, for not much more money.

So my recollection is that JVX was always written around tilt-rotor, and that there was never any other candidate for JVX.
 

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LowObservable said:
I was watching from the bleachers, rather than being personally involved, but my sense of it was that HXM was moving (not very decisively - I don't think I ever saw Sikorsky or Bell ideas for HXM) and then the TR advocates came on board, arguing that with economies of scale, the tilt-rotor would do HXM and much more, plus the SOF, Army and Navy (SV-22 ASW) missions, for not much more money.

So my recollection is that JVX was always written around tilt-rotor, and that there was never any other candidate for JVX.
Not quite how it happened. HXM survived multiple attempts to kill it or to have its requirements rewritten around the H-60. It was finally approved as a program, Bell did propose a Tilt-Rotor design, Boeing proposed a tandem rotor helo that could be considered the "father" of the Boeing 360, I can't remember what Sikorsky proposed once they couldn't convince people to write the requirements around the H-60. Then the new Reagan Administration saw a way to combine multiple service requirements into one program, JVX It also encouraged teaming. In response to DoD's preference for teaming, Bell and Boeing, the two companies with the most Tilt-Rotor experience, teamed. It wasn't that JVX was written around Tilt-Rotor, it was that Tilt-Rotor was the only technology that was mature and capable enough to have a chance at meeting the requirement of all the programs that became JVX in one basic vehicle. became apparent that since other potential bidders were not willing to bid a Tilt-Rotor and DoD was not willing to reduce its requirements just so someone else could bid, Bell-Boeing became the only bidders. The question was which was more important, the mission or the desire to have more than one bidder (if DoD hadn't pushed for teaming, Bell and Boeing probably would have bid against each other).

In response to a request elsewhere, I posted a more complete tale of the birth of JVX here: http://www.secretprojects.co.uk/forum/index.php/topic,1309.msg28164.html#new
 

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So it's more correct to state that JVX was a non-helicopter solution (with more performance than a helo could provide) but that the only compliant offer was a TR from Bell/Boeing.

The 360 could not meet JVX (as opposed to HXM) and became a tech demo.
 

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LowObservable said:
So it's more correct to state that JVX was a non-helicopter solution (with more performance than a helo could provide) but that the only compliant offer was a TR from Bell/Boeing.

The 360 could not meet JVX (as opposed to HXM) and became a tech demo.

That's a good description. JVX did not specifically exclude a helicopter, but at the time (and still true today) there was no conventional or advanced helicopter technology that had demonstrated sufficient promise to make a credible proposal. ABC might have theoretically been able to do it, but would have been such an extremely high risk it wouldn't have had a chance of being selected. The relative results of the XH-59 and XV-15 programs would have pushed towards a Tilt-Rotor solution even if an ABC had been bid.

Again, the reason there was only one bid was that the two companies with the most Tilt-Rotor knowledge formed a team in response to Gov't pressure for teams on JVX. Just as an aside, all the data from the XV-15 program while it was under NASA sponsorship was available for free to anyone who wanted it. Even after the program came under partial Army sponsorship, the later data would have been made available to any bidders for JVX. Only the data generated by Bell when it later was totally funding one of the XV-15s would have been considered proprietary.
 

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To oversimplify, but I was there, the HXM became a tiltrotor because Marines flew the XV-15. It turned skeptics into supporters and supporters into zealots. The deputy program manager, who was hard over for the Boeing 360, came to Bell at our invitation to fly the XV-15. He had only one extra request, which was to walk under the XV-15 while it was in a 50-ft hover. He flew it and then we swapped a pilot for him. He walked under it while it was hovering and back out. While the XV-15 was shutting down, I asked him what he thought, and he simply said, "I was wrong." He went back to Washington, helped make the specification require a tiltrotor, retired from the Marine Corps, and joined Boeing working on the V-22 program (if there was any hanky panky involved, I'm a terrible judge of character - he was one of the straightest of arrows).

Of course, the requirements that they came up stretched the state of the art a bit too much and their procurement plan - fixed price, teaming for development, competition for production - was seriously flawed, but that's another story...
 

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I saw the XV-15 fly at Paris in 1981 and I was impressed, too. It was quiet, agile and smooth in transition. But what was not generally realized was that the JVX was another kettle of fish completely, just as helicopters change their nature as they get bigger; greater torque, higher disk loading, bigger vibrational loads, much higher control loads. So the XV-15 was remarkable, but it was also misleading.
 

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Tailspin Turtle said:
To oversimplify, but I was there, the HXM became a tiltrotor because Marines flew the XV-15. It turned skeptics into supporters and supporters into zealots. The deputy program manager, who was hard over for the Boeing 360, came to Bell at our invitation to fly the XV-15. He had only one extra request, which was to walk under the XV-15 while it was in a 50-ft hover. He flew it and then we swapped a pilot for him. He walked under it while it was hovering and back out. While the XV-15 was shutting down, I asked him what he thought, and he simply said, "I was wrong." He went back to Washington, helped make the specification require a tiltrotor, retired from the Marine Corps, and joined Boeing working on the V-22 program (if there was any hanky panky involved, I'm a terrible judge of character - he was one of the straightest of arrows).

Of course, the requirements that they came up stretched the state of the art a bit too much and their procurement plan - fixed price, teaming for development, competition for production - was seriously flawed, but that's another story...
I totally agree that the procurement plan was flawed. We never seem to learn from our mistakes. Every advanced technology R&D program that was done fixed price, all the way back to the '60s, came unglued. Yet they still try and do them because it makes the PMs look good up front ("Yes, we have determined it'll take exactly $3,652,291,045.87 to develop antigravity").


Say, you aren't Shorty or Cliff, are you? If you are, I might know you.
 

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Hi,

early design to Boeing Vertol Model-360,was strarted to
meet a Marine Crops medium-lift requirement.
http://www.flightglobal.com/pdfarchive/view/1983/1983%20-%201292.html
 

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Model 360 vs V-22: same payload, 1/2 the gross weight, 3/4 the speed, 1/10 the cost. Another one for the 'What If' file...

NASA Contractor Report 181766
"GROUND SHAKE TEST OF THE BOEING MODEL 360 HELICOPTER AIRFRAME"

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19890014549_1989014549.pdf

Also has airframe subsystem modules, primary structure, transmission and engine support structure imagery.
 

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Abraham Gubler said:
Model 360 vs V-22: same payload, 1/2 the gross weight, 3/4 the speed, 1/10 the cost. Another one for the 'What If' file...

<snip>
Not really sure you can make this comparison quite so directly. 360 was a technology demonstrator which, if a derivative had gone into production, would certainly have weighed more (as virtually all aircraft do when they go into production). Even so, the 360 was half the gross of the V-22 only if you compare the weight of the V-22 at its weight for the rolling takeoff self-deployment mission vs the normal gross weight of the 360. As for 1/10 the cost, while the cost rise in the Osprey was ridiculous, we can't assume that a 360 would have fared any better. The desired engine choice would still have been overruled and a heavier, somewhat thirstier engine would still have been imposed. It's likely Cheney still would have canceled the program and tried to force H-60s in its place, and in the '90s, the program still would have been on life support as it was rescheduled so that the big expenses wouldn't show up until after the 2000 elections. Both of those factors would serve to dramatically drive up costs.
 

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I think I know you F-14D ;D
 

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yasotay said:
I think I know you F-14D ;D
Then you have my sympathy...you must have ticked off the gods in a previous life that they would inflict that on you! :D
 

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More about the Model 360 and other Boeing Vertol developments from the 1980s:

ROTORCRAFT TECHNOLOGY AT BOEING VERTOL: RECENT ADVANCES
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19880007275_1988007275.pdf

F-14D said:
Not really sure you can make this comparison quite so directly.
I think I could go further, of course being speculative:

Sure the Model 360 (aka CH-46X) as flown was a test bed so not weighed down with operational equipment. But the design of the airframe and the power-rotor system are both considerably lighter than that of the V-22 and its tilt rotors. All other things being equal the M360 is going to have significantly less weight across all states (empty, operating empty, typical mission, gross takeoff, etc) than the V-22 for same payload and mission radius. Lower empty weight means lower unit cost and less fuel burn.

The M360 would also be significantly easier to develop than the V-22 being as it is still a conventional helicopter evolutionary from the existing Boeing tandem families. The only ‘new’ aerodynamic feature was the rotor shape and tips. The task of maturing them to production level pales into insignificance compared to the tilt rotor system of the V-22. This would significantly lower the development cost. The only thing that could really stop or hold back the M360 is the politicians and the V-22 which had to face them AND its own complex technology.

Then the performance? They both carry the same payload but the M360 cruises at 200 knots and the V-22 at 250. The M360 has far superior takeoff and landing performance to the V-22 making it a much safer plane to fly into combat and use in hot and high environments. It is also far more accessible and ship friendly with a rotor diameter of only 50 feet versus 80 feet. The M360 would have been much cheaper to develop, to buy and to operate it would also be much easier to operate at sea and ashore. All for a 20% reduction in cruising speed.

And if 250 knots cruise speed was a goal that had to be reached you could always add a block 2 development to the M360. You could add the Boeing concept of above rotor wings combined with a thrust propeller enabling a composite helicopter in which the rotors can be unloaded in forward flight like the Cheyenne. This would require a minimal change to the M360 because its rear engine/main gearbox configuration is very friendly to a propeller. Such a design would also improve hover control, autorotation and provide rapid acceleration and deceleration (thanks to the tail propeller): all things that aren’t the V-22’s strong point and of very high importance in combat.

Achieving high speed via evolving the tandem helicopter as in the M360 and even taking it further to a composite would have been a far better approach than the dramatic new technology of tilt rotors. But the customer is always right...
 

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What's worse than the drag of one rotor? The drag of two rotors...

You can make a helicopter go "fast", i.e. 200 knots. What you can't do is make it go "fast" for very long (and therefore very far) because of the very poor lift over drag ratio of a rotor at even moderately high speeds. Unloading the rotor with a wing and adding a thruster might make it a bit better but not much, and you'd be eating into the payload with the wing and the thruster.

Politicians didn't pick the tiltrotor over the 360. Knowledgeable Marines looked at Boeing's claims for the 360 and flew it and the XV-15; they decided that they wanted a tiltrotor because they sometimes needed both speed and range for their missions. If Boeing had really believed in their 360 claims, they would have stood their ground. Instead they opted to team with Bell on what became the V-22.
 

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Abraham Gubler said:
More about the Model 360 and other Boeing Vertol developments from the 1980s:

ROTORCRAFT TECHNOLOGY AT BOEING VERTOL: RECENT ADVANCES
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19880007275_1988007275.pdf

F-14D said:
Not really sure you can make this comparison quite so directly.
I think I could go further, of course being speculative:

Sure the Model 360 (aka CH-46X) as flown was a test bed so not weighed down with operational equipment. But the design of the airframe and the power-rotor system are both considerably lighter than that of the V-22 and its tilt rotors. All other things being equal the M360 is going to have significantly less weight across all states (empty, operating empty, typical mission, gross takeoff, etc) than the V-22 for same payload and mission radius. Lower empty weight means lower unit cost and less fuel burn.

The M360 would also be significantly easier to develop than the V-22 being as it is still a conventional helicopter evolutionary from the existing Boeing tandem families. The only ‘new’ aerodynamic feature was the rotor shape and tips. The task of maturing them to production level pales into insignificance compared to the tilt rotor system of the V-22. This would significantly lower the development cost. The only thing that could really stop or hold back the M360 is the politicians and the V-22 which had to face them AND its own complex technology.

Then the performance? They both carry the same payload but the M360 cruises at 200 knots and the V-22 at 250. The M360 has far superior takeoff and landing performance to the V-22 making it a much safer plane to fly into combat and use in hot and high environments. It is also far more accessible and ship friendly with a rotor diameter of only 50 feet versus 80 feet. The M360 would have been much cheaper to develop, to buy and to operate it would also be much easier to operate at sea and ashore. All for a 20% reduction in cruising speed.

And if 250 knots cruise speed was a goal that had to be reached you could always add a block 2 development to the M360. You could add the Boeing concept of above rotor wings combined with a thrust propeller enabling a composite helicopter in which the rotors can be unloaded in forward flight like the Cheyenne. This would require a minimal change to the M360 because its rear engine/main gearbox configuration is very friendly to a propeller. Such a design would also improve hover control, autorotation and provide rapid acceleration and deceleration (thanks to the tail propeller): all things that aren’t the V-22’s strong point and of very high importance in combat.

Achieving high speed via evolving the tandem helicopter as in the M360 and even taking it further to a composite would have been a far better approach than the dramatic new technology of tilt rotors. But the customer is always right...
Adam,

You might want to re-look at two of my posts on April 4, 2008 and Tailspin's on April 7, especially his last sentence. The point is that V-22 (as opposed to a Tilt-Rotor in general) was designed to meet the more stringent (some may opine too stringent) requirements of JVX while Boeing 360 was really geared for the simpler HXM (for one thing HXM only required a 170-180 knot cruise). I don't think you give Boeing enough credit, as the 360 was more than just an evolutionary Boeing tandem. That largely composite fuselage was a major and impressive advance, although we'll never know how it would have worked out in FSD and production, given the mid 1980s technology involved. Of course, one could also say that a Tilt-Rotor that only had to meet HXM would have been lighter, simpler and cheaper than the V-22.

While it's true that the V-22 rotor arc is wider than that of a 360, the 360's rotor disk extends further forward and aft from the fuselage, which could be a consideration in tight terrain. Regarding the fuel burn, the 360 would unquestionably burn less than the V-22 in rotor borne flight, but how would it compare once the V-22 becomes partially or totally wingborne? One of the principles behind the Tilt-Rotor concept is that normally only a small percentage of your flight is pure powered lift.

I question whether adding wings and a pusher prop (especially reversible) to the 360 would be all that simple and cheap, it hasn't proven to be that so far with any other program. Just for the record, the AH-56 never achieved the cruise speeds it originally promised, the requirements were lowered during the program (in fact, Sikorsky's S-67 could meet the final speed requirement). Doing this kinda thing safer in combat is a complex thing, since both are going to be particularly vulnerable during the departure/arrival phase. Here's a slightly different perspective: On the V-22, if enemy fire takes out the cross shaft, it is a major problem if it occurs during lower altitude rotorborne flight with one engine already out. On the 360, loss of the shaft for any reason at any portion of the flight means loss of the aircraft.

Don't want this to devolve into a V-22 vs____debate. If we are going to use the Boeing 360, then we'd have to wonder what a Tilt-Rotor that only had to meet HXM would have been like, another entry in the "What if" file...
 

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There are three issues here: my hypothetical about evolving the Model 360 into a composite helicopter, the comparative effectiveness of the M360 versus the V-22 and the program issues associated with what the Marines wanted and HXM/JVX. The first issue is mostly irrelevant but I would suggest that the speed limitations applied to the Cheyenne during testing had a lot more to do with ironing out the issues with its “rigid” rotor system rather than the pusher prop, composite helicopter design.

Helicopter rotors may be draggy but one of the major aims of the M360 project was to develop advanced helicopter and rotor low drag and beneficial aerodynamic conditions. The ‘Advanced High Speed Rotor’ blades of the M360 were designed for high Mach number penetration as they advanced. Testing by Boeing showed that the blades were still useful at up to 231 knots (the limit of the wind tunnel). From Boeing’s NASA report:

Developed with the support of 4,720 hours of wind tunnel testing, the blade incorporates the VRI2/VRI5 airfoils, the latest step in transonic airfoils, together with a tapered tip planform. Model rotor tests substantiated the significant performance improvement, shown in Figure 29, available from the rotor. As shown, the hover efficiency is improved by 6 percent and the cruise efficiency by 23 percent relative to current rotor systems. This rotor, in combination with the low drag Model 360 fuselage, will provide a cruise speed capability of 200 knots.
This is perhaps the biggest loss of the V-22 go ahead that technology development to get the most out of conventional helicopter rotor configurations was consigned to another 20-30 years in the R&D shed rather than fielded in a production system. So rather than a niche of high speed tiltrotors we could see the benefits of >200 knot cruise speed across ALL helicopter applications.

While the M360 is longer than the V-22 and has more rotor overhang to the front this is nowhere near as important for the Marines as width. The Marines do not routinely operate helicopter/tilt rotors from platforms suspended on the sides of cliffs. They do routinely operate from LHA/LHD flight decks where 80 foot wide rotors is pushing the boundaries of risk appetite.

As to why the Marines selected tilt rotors and the JVX over advanced rotors and HXM or a more challenging JVX like specification, I would suggest this had a lot to do with non operational factors. While on an operational level the managers where impressed with the sweetness of the XV-15 the strategic decision making was in a very different space. For example the very survival of the Marines as an independent force and their discovery of a procurement method that enabled them to get their own, new, aircraft rather than Navy hand me downs.

In the post Vietnam Era the Marines developed the concept of over the horizon amphibious assault as a way to stay relevant in the face of enhanced air-sea defences, well they had been working on it since the 50s but what emerged in te 70s has stayed with us since. This concept required a specially tailored force with high speed landing craft (LCAC), amphibians (EFV) and VTOL transports (V-22). This meant only the specially tailored USMC could be trusted with amphibious assault not just an Army light infantry division with some familiarisation training in running down LCM8 ramps. The air mobility part of this triad had to be something unique to help promote the independence of the force. Therefore an additional 70 knots of cruise was needed even though it’s very hard to support a parametric based argument that such a difference is significant for over the horizon amphibious assault.

The last element was what the Marines discovered with the AV-8 program. If they specify something completely different to the other services they can run the project themselves and actually get new aircraft rather than Navy hand me downs. With the same “PR as the Devil” they could get the Congressional approval and as long as what they needed was different enough to the Navy and Army they could run it themselves. This is why they backed the A-18 (AW) (shame no image surfaced for “Strike From the Sea”) when Navy went for A-6F/A-12A. Sure they just got a tandem seat F/A-18 but that was much better than being at the end of the line for A-6F/A-12A. This is also a good reason why they wanted a V-22 rather than a advanced helicopter that Army and Navy might have been more motivated about.
 

Stargazer2006

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Very interesting analysis. The USMC's will to be different here makes a lot of sense.
 

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Abraham Gubler said:
There are three issues here: my hypothetical about evolving the Model 360 into a composite helicopter, the comparative effectiveness of the M360 versus the V-22 and the program issues associated with what the Marines wanted and HXM/JVX. The first issue is mostly irrelevant but I would suggest that the speed limitations applied to the Cheyenne during testing had a lot more to do with ironing out the issues with its “rigid” rotor system rather than the pusher prop, composite helicopter design.

Helicopter rotors may be draggy but one of the major aims of the M360 project was to develop advanced helicopter and rotor low drag and beneficial aerodynamic conditions. The ‘Advanced High Speed Rotor’ blades of the M360 were designed for high Mach number penetration as they advanced. Testing by Boeing showed that the blades were still useful at up to 231 knots (the limit of the wind tunnel). From Boeing’s NASA report:

Developed with the support of 4,720 hours of wind tunnel testing, the blade incorporates the VRI2/VRI5 airfoils, the latest step in transonic airfoils, together with a tapered tip planform. Model rotor tests substantiated the significant performance improvement, shown in Figure 29, available from the rotor. As shown, the hover efficiency is improved by 6 percent and the cruise efficiency by 23 percent relative to current rotor systems. This rotor, in combination with the low drag Model 360 fuselage, will provide a cruise speed capability of 200 knots.
This is perhaps the biggest loss of the V-22 go ahead that technology development to get the most out of conventional helicopter rotor configurations was consigned to another 20-30 years in the R&D shed rather than fielded in a production system. So rather than a niche of high speed tiltrotors we could see the benefits of >200 knot cruise speed across ALL helicopter applications.

While the M360 is longer than the V-22 and has more rotor overhang to the front this is nowhere near as important for the Marines as width. The Marines do not routinely operate helicopter/tilt rotors from platforms suspended on the sides of cliffs. They do routinely operate from LHA/LHD flight decks where 80 foot wide rotors is pushing the boundaries of risk appetite.

As to why the Marines selected tilt rotors and the JVX over advanced rotors and HXM or a more challenging JVX like specification, I would suggest this had a lot to do with non operational factors. While on an operational level the managers where impressed with the sweetness of the XV-15 the strategic decision making was in a very different space. For example the very survival of the Marines as an independent force and their discovery of a procurement method that enabled them to get their own, new, aircraft rather than Navy hand me downs.

In the post Vietnam Era the Marines developed the concept of over the horizon amphibious assault as a way to stay relevant in the face of enhanced air-sea defences, well they had been working on it since the 50s but what emerged in te 70s has stayed with us since. This concept required a specially tailored force with high speed landing craft (LCAC), amphibians (EFV) and VTOL transports (V-22). This meant only the specially tailored USMC could be trusted with amphibious assault not just an Army light infantry division with some familiarisation training in running down LCM8 ramps. The air mobility part of this triad had to be something unique to help promote the independence of the force. Therefore an additional 70 knots of cruise was needed even though it’s very hard to support a parametric based argument that such a difference is significant for over the horizon amphibious assault.

The last element was what the Marines discovered with the AV-8 program. If they specify something completely different to the other services they can run the project themselves and actually get new aircraft rather than Navy hand me downs. With the same “PR as the Devil” they could get the Congressional approval and as long as what they needed was different enough to the Navy and Army they could run it themselves. This is why they backed the A-18 (AW) (shame no image surfaced for “Strike From the Sea”) when Navy went for A-6F/A-12A. Sure they just got a tandem seat F/A-18 but that was much better than being at the end of the line for A-6F/A-12A. This is also a good reason why they wanted a V-22 rather than a advanced helicopter that Army and Navy might have been more motivated about.

Abraham

Don't want this to devolve into a 360 vs Osprey situation. I do want to note that what happened to Army V-22s and why is covered elsewhere under other topics in this forum, and the Navy's total requirement had always been only 48 of whatever was bought for CSAR/COD duties, to be ordered late in the program when unit costs came down and they got the funding. We'll never know where the 360 could have gone beyond a basic technology demonstrator flying a very limited profile to something usable for the HXM mission without encountering the same problems, technological (especially in composite structure) and political, that the Osprey did. I do want to stick up for the Marines, though, and how and why they buy aircraft.

USMC aviation is unique in that unlike any other US service, and probably any other in the world, the sole reason for its existence is to provide support to troops on the ground. Everything they do is analyzed through that lens. Since the Navy, not the Marines, buy the aircraft, this has always been a balancing act, and they sometimes don't follow the party line. They don't fear hand me downs, their aircraft are usually new, although they are concerned that when the Navy runs short of funds, they'll take some of the Marines' aircraft (as has happened), but the overriding focus is what an aircraft will do for the ground troops. They did not go from the A-4 to the A-7 because even though the latter was a much better plane, the things it was better at were mostly not things the Marines needed that much, so they'll keep developing the A-4, thank you very much. They originally got into the A-6 because they needed some aircraft with more payload than the A-4, but mostly because they needed to be able to support troops in all weather. They did like the concept of the F/A-18 (AW) because, while it didn't do enough for the Navy, it did do enough for them, and they actually didn't need the greater capability of what would become the A-6F. This is why the Marines aren't interested in the Super Hornet. It costs way too much more for what, to them, is little improvement in the capabilities they need. BTW, you can find pictures of the (AW) in the November 7, 1983 issue of Aviation Week. I suspect there may have been copyright or space issues in getting it into the superb "Strike for the Sea"

Regarding the AV-8, the big driver for them was not to be different from the Navy and own it themselves. In Vietnam, they found over and over that how fast fixed wing air could get there was far more important than what the fixed wing air was and how much it carried. STOVL AV-8s offered them what they needed more , enough to overcome the penalties associated with it. The equation did not work out that way for the Navy. When the Marines went to the AV-8B they kept what was important to them and ended up with an aircraft with good payload/range and what turned out to be the finest Close Air Support fixed wing in the world.

Back to this topic: The decision to go with Tilt-Rotor over working to develop advances in tandem rotor technology was not to be different from the Navy; USN wouldn't have been a big customer no matter what was selected for HXM, but because they felt Tilt-Rotor was better at what they needed (remember, speed was not the deciding factor). In no way denigrating the 360, I happen to agree with them. Like you said, though, it'll always remain a "What if".
 

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Dear F14D,

Thanks for some more high quality input. Understanding the complex interplays and results of past projects helps us understand the same interplays and potentially predict the results of current and future projects. Certainly a much better approach than just swallowing which ever partisan commentators opinion mostly aligns with one’s own beliefs.

When it comes to the JVX and the subsequent problems with the V-22 the most crucial point would be what Bill Norton wrote as “the LHA set the maximum rotor diameter at 38 feet... a reduction from... an optimal 43 feet” (Aerofax V-22). The complex interplay in action.
 

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Abraham Gubler said:
Dear F14D,

Thanks for some more high quality input. Understanding the complex interplays and results of past projects helps us understand the same interplays and potentially predict the results of current and future projects. Certainly a much better approach than just swallowing which ever partisan commentators opinion mostly aligns with one’s own beliefs.

When it comes to the JVX and the subsequent problems with the V-22 the most crucial point would be what Bill Norton wrote as “the LHA set the maximum rotor diameter at 38 feet... a reduction from... an optimal 43 feet” (Aerofax V-22). The complex interplay in action.
Yes, that's true. It's for clearance abeam the island. Note that if the Army version as originally conceived has been built, it's quite possible there would have been different proprotors on its version, but that's another story
 

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F-14D said:
Yes, that's true. It's for clearance abeam the island. Note that if the Army version as originally conceived has been built, it's quite possible there would have been different proprotors on its version, but that's another story
Perhaps Boeing Vertol should have been in the lead for V-22 and with Bell developed a tandem tilt rotor...
 

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Abraham Gubler said:
F-14D said:
Yes, that's true. It's for clearance abeam the island. Note that if the Army version as originally conceived has been built, it's quite possible there would have been different proprotors on its version, but that's another story
Perhaps Boeing Vertol should have been in the lead for V-22 and with Bell developed a tandem tilt rotor...
Some might argue that the standard tilt rotor is a tandem rotor... turned sideways and then 90 degrees.
 

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Abraham Gubler said:
F-14D said:
Yes, that's true. It's for clearance abeam the island. Note that if the Army version as originally conceived has been built, it's quite possible there would have been different proprotors on its version, but that's another story
Perhaps Boeing Vertol should have been in the lead for V-22 and with Bell developed a tandem tilt rotor...
The original Army JVX was to handle MEDEVAC duties, but also to meet the Army's Special Equipment Mission Aircraft (SEMA) requirement. In the latter role, it would have to cruise at a higher altitude than other V-22s, which is why I speculate the proprotors would have been different. This would have been true no matter who was in the lead.
 

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yasotay said:
Abraham Gubler said:
F-14D said:
Yes, that's true. It's for clearance abeam the island. Note that if the Army version as originally conceived has been built, it's quite possible there would have been different proprotors on its version, but that's another story
Perhaps Boeing Vertol should have been in the lead for V-22 and with Bell developed a tandem tilt rotor...
Some might argue that the standard tilt rotor is a tandem rotor... turned sideways and then 90 degrees.
Well, since Phrog pilots tell me that a regular tandem rotor helo seems to want to fly sideways anyway... ;D
 

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The Model 360 was such a sleek design. What became of it? Was it scrapped, or is it still in a Boeing hangar somewhere?
 

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Stargazer2006 said:
The Model 360 was such a sleek design. What became of it? Was it scrapped, or is it still in a Boeing hangar somewhere?
this still there, but in sad condition
in Wilmington, New Castle County, Delaware, USA
http://www.airliners.net/search/photo.search?regsearch=N360BV&distinct_entry=true
some thing like this has to be in a museum :mad:

Ground shake test on Model 360 by NASA
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19890014549_1989014549.pdf

This was once the largest all composite helicopter ever built. It almost bankrupted Boeing in 1987
from the Airliner link

is that info true or had this be Vertol ?
 

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How sad... :-[ especially if that thing about it costing so much money is true... :-\
 

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Michel Van said:
Stargazer2006 said:
The Model 360 was such a sleek design. What became of it? Was it scrapped, or is it still in a Boeing hangar somewhere?
this still there, but in sad condition
in Wilmington, New Castle County, Delaware, USA
http://www.airliners.net/search/photo.search?regsearch=N360BV&distinct_entry=true
some thing like this has to be in a museum :mad:

Ground shake test on Model 360 by NASA
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19890014549_1989014549.pdf

This was once the largest all composite helicopter ever built. It almost bankrupted Boeing in 1987
from the Airliner link

is that info true or had this be Vertol ?
It might well have been the largest all composite helicopter (which may have led to extended development if there was any decision to move towards an operational vehicle), but "..almost bankrupting Boeing" seems a bit unlikely. After all, this is Boeing, and in the grand scheme of things, this wasn't a "bet the company" (as the 707 and 747 were) program. Even if it had a lot of problems, it was a company funded aircraft, and would be treated the same as similar programs in other companies. "Hey! The ______________ program is costing us way more than we'll ever get back". "Okay, stop the program". Witness the F-20.
 

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Perhaps what it means is that it almost led to the demise of Boeing Helicopters, not the Boeing group as a whole...
 

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Stargazer2006 said:
Perhaps what it means is that it almost led to the demise of Boeing Helicopters, not the Boeing group as a whole...
Same thought, given it was company funded (unless they got waaaay too carried away--always a distinct possibility, of course): "Hey! we're spending our own money, and this thing is dragging down our whole company. What do we do"? "Stop spending money". "Oh; good idea".

I don't know the truth but if one demonstrator was costing them that much with no prospect of enough technological gain to eventually bring them profits, one would think someone would slap them upside the head!
 

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On tandem tilt rotors the whole point was in context of the LHA flight deck width limit reducing the size of the V-22's side by side tilt rotors to the level where they were overloaded and subsequent enormous effort to make that aircraft fly. If said tilt rotors were tandem (one behind the other) then they could be much bigger without coming close to the width limits of the LHA (see attached picture drawn with very fine art skills...). Of course there are all sorts of other problems such a configuration would generate but the core issue of rotor lift for footprint would be solved.

On the Model 360 Boeing developed a lot of new technology that went into the RAH-66, CH-47F and the V-22 - so far. So their return on Model 360 investment has been considerable. Sure no one ordered the CH-46X (a designation sometimes associated with the M360) but as a technology test bed it was a success.
 

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