Boeing Vertol BV-360 or "Boeing 360"

[F-14D]

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.

Hey, your art skills are better than mine!. With the tandem, you are going to run into some complex issues wherein the aft proprotor has to change from a tractor to a pusher and vice versa during the transition. And you do run into the situation in hostile terrain that your rotors extend ahead of the nose and more importantly aft of the rear (where they aren't visible), but you do gain the width benefit. The V-22's less than optimum rotor size does not cause it to be only be able to stagger into the air, but it does reduce efficiency in powered lift flight.

Your point on the 360 is well taken and one I totally agree with, BTW. That's why I was reacting to the referenced statement that the 360 almost broke Boeing Helicopters-- if it was really that bad, they'd just stop it; there was no gov't development contract that forced them to keep going. They clearly felt the technology gain was worth it...

 

[Abraham Gubler]

Hey, your art skills are better than mine!. With the tandem, you are going to run into some complex issues wherein the aft proprotor has to change from a tractor to a pusher and vice versa during the transition. And you do run into the situation in hostile terrain that your rotors extend ahead of the nose and more importantly aft of the rear (where they aren't visible), but you do gain the width benefit. The V-22's less than optimum rotor size does not cause it to be only be able to stagger into the air, but it does reduce efficiency in powered lift flight.

And that's just the start of the list... Having the entire nose of the aircraft within the propeller wash is going to create all sorts of problems. Then there is engine maintained, cross shafting (forget about it), etc.

Which raises the next inter-related point. Why is the tail wagging the dog? In this case why is the LHA proscribing the dimensions of the JVX?

It’s like the crazy idea that Army ground combat vehicles need to fit into a C-130 for airborne tactical manoeuvre. Of course with a maximum load a C-130 can fly from here to nowhere significant and how do you offload a battalion or company at an austere airport from C-130s in anything less than a few days and since when is the air force going to through away C-130s to deliver a single tank? The solution is to design the tank tactical airlifter to the needs of the optimum ground combat vehicle. Something like the Boeing ATT Super Frog able to carry a ~50 ton vehicle and offload it on a field ~2,000km away from your base rather than offload a 18 tone vehicle at an austere airport ~500km from your MOB.

The same applies to JVX. The V-22 should have been designed with the >43 foot rotors that the mission required and the next classes of amphibious ships designed to support this width (>100 feet rather than >80 feet). Sure this may have limited your operation of V-22 from island side flight decks of the LHAs and LPHs. But they could always revert to original style flight deck operation with the V-22s spotted forward and aft of the island along the centreline. Which would probably enable at least six to launch and land simultaneously per LHA/LPH. The new LHDs would be designed with the flight deck width to enable the full length to be covered by V-22 spots offset to port.

That’s the dog wagging the tail. The dog being the thing that engages the enemy rather than the supporting complex.

 

[F-14D]

Hey, your art skills are better than mine!. With the tandem, you are going to run into some complex issues wherein the aft proprotor has to change from a tractor to a pusher and vice versa during the transition. And you do run into the situation in hostile terrain that your rotors extend ahead of the nose and more importantly aft of the rear (where they aren't visible), but you do gain the width benefit. The V-22's less than optimum rotor size does not cause it to be only be able to stagger into the air, but it does reduce efficiency in powered lift flight.

And that's just the start of the list... Having the entire nose of the aircraft within the propeller wash is going to create all sorts of problems. Then there is engine maintained, cross shafting (forget about it), etc.

Which raises the next inter-related point. Why is the tail wagging the dog? In this case why is the LHA proscribing the dimensions of the JVX?

It’s like the crazy idea that Army ground combat vehicles need to fit into a C-130 for airborne tactical manoeuvre. Of course with a maximum load a C-130 can fly from here to nowhere significant and how do you offload a battalion or company at an austere airport from C-130s in anything less than a few days and since when is the air force going to through away C-130s to deliver a single tank? The solution is to design the tank tactical airlifter to the needs of the optimum ground combat vehicle. Something like the Boeing ATT Super Frog able to carry a ~50 ton vehicle and offload it on a field ~2,000km away from your base rather than offload a 18 tone vehicle at an austere airport ~500km from your MOB.

The same applies to JVX. The V-22 should have been designed with the >43 foot rotors that the mission required and the next classes of amphibious ships designed to support this width (>100 feet rather than >80 feet). Sure this may have limited your operation of V-22 from island side flight decks of the LHAs and LPHs. But they could always revert to original style flight deck operation with the V-22s spotted forward and aft of the island along the centreline. Which would probably enable at least six to launch and land simultaneously per LHA/LPH. The new LHDs would be designed with the flight deck width to enable the full length to be covered by V-22 spots offset to port.

That’s the dog wagging the tail. The dog being the thing that engages the enemy rather than the supporting complex.

Couple of thoughts, although we are getting away from the Boeing 360.

When JVX was first mooted, no one guessed that Cheney would cancel it and Clinton would delay it. So, said vehicle was designed to operate from existing platforms. Since there were provisions in the design for the other services (including the stillborne Army version), you ended up with a heavier vehicle than you would have had for pure HXM, and on a lighter aircraft you could have smaller proprotors. However, although JVX was heftier, it still had to meet the Marines' requirement for shipboard compatibility. You see this in other multi-service aircraft: F-35, CH-53, F-111 (ooooo, bad example), etc. The F-14 would have benefitted from being two feet longer, but that would have an impact on how many you could park and move on the flight and hangar decks The V-22 is not as efficient with the 38 foot discs as it would be with 43, but it's good enough to meet the need. As I said, there may have been different proprotors on the Army V-22 (I'm not sure), but that version didn't happen.

 

[yasotay]

I'm sure that F-14D has far more information on the issue, but the Army JVX did have larger prop-rotors and was not near as complex having no need for all of the folding apparatus that has to go on the MV-22 and CV-22. I am sure that there are ongoing efforts to make the next Block of CV-22 better. I would bet on new rotors, changes to hydraulics and electrical systems.

As to tandem rotor helicopters, I don't think that Boeing has completely tossed it. Remember that they promoted a tandem for the JHL effort originally. I suspect as a core competence it will remain one of their first considerations for any new rotorcraft, at least cargo rotorcraft. So, much of what they learned from the 360 effort remains available to Boeing if a conventional tandem rotor aircraft is called for in the future.

 

[F-14D]

I'm sure that F-14D has far more information on the issue, but the Army JVX did have larger prop-rotors and was not near as complex having no need for all of the folding apparatus that has to go on the MV-22 and CV-22. I am sure that there are ongoing efforts to make the next Block of CV-22 better. I would bet on new rotors, changes to hydraulics and electrical systems.

As to tandem rotor helicopters, I don't think that Boeing has completely tossed it. Remember that they promoted a tandem for the JHL effort originally. I suspect as a core competence it will remain one of their first considerations for any new rotorcraft, at least cargo rotorcraft. So, much of what they learned from the 360 effort remains available to Boeing if a conventional tandem rotor aircraft is called for in the future.

I believe the Army was going to have different proprotors, at least in the SEMA birds, because of the requirement to cruise at 30,000 feet. You can see a similar situation if you look at the rotors of Army AH-1s vs. Marines AH-1Ws. They Army birds can HOGE at a much greater altitude than the Whiskey. Marines didn't care about HOGE at high altitude, that's not their environment. What they needed was to be able to continue to lift their full load at lower altitudes as the temperature rose and the -1W's rotor was optimized for that.

My understanding is that the wing would be mounted similar to the Marines' version, for cost reasons, but would not fold, which would save weight and a lot of maintenance (of course larger proprotors would also be an issue here). This is like USAF F-4s. On the C/D models, the wing folds and mechanisms were the same as on Navy Phantoms. The hydraulic actuators were removed on the F-4E/G, but the folds remained the same.

You know, if the 360 had somehow been developed to meet another need, unlike the CH-47 it might have made a great CSAR bird.

 

[fightingirish]

Cutaway Boeing Vertol 360 @ Flight Global

 

[Stargazer]

The Model 360 as photographed a few years ago:

 

[Mark Nankivil]

Hi All -

Boeing Vertol Model 360 display model in USMC markings....

http://www.ebay.com/itm/Boeing-Vertol-360-Marines-Helicopter-Desk-Model-/251278045881?pt=LH_DefaultDomain_0&hash=item3a8156b2b9

Enjoy the Day! Mark

 

[RAP]

Boeing 360 helicopter display model

http://www.ebay.com/itm/OLD-BOEING-MODEL-360-EXPERIMENTAL-TANDEM-ROTOR-HELICOPTER-CONTRACTOR-DESK-MODEL-/371971743495?hash=item569b3e5f07:g:d3oAAOSwcgNZM7wN

 

[Pioneer]

Can anyone direct me to more in depth info re the actual HXM program please?, whether on this forum or others.

Regards
Pioneet

 

[Mark Nankivil]

A recent donation to the Museum from the widow of a Boeing-Vertol/Boeing St. Louis engineer netted this cut sheet on the 360.

Enjoy the Day! Mark

 

[TomS]

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.

I know this is going back quite a ways, but is there any chance the image at the link below was the Sikorsky HXM? It's labeled as a 1970s design for an ABC helo in Marine colors and looks like it would be about the right size for an H-46 replacement. Not much in the way of details, though.

https://www.secretprojects.co.uk/threads/sikorsky-advancing-blade-concept-abc-projects.6241/page-2#post-247386

 

[VTOLicious]

Can someone knowledgeable explain why the front rotor has a greater forward-tilt than the rear?

 

[TomS]

FWIW, the CH-47 does the same thing.

 

[yasotay]

Can someone knowledgeable explain why the front rotor has a greater forward-tilt than the rear?
View attachment 676803

Notice that the 360 (and CH-46 and 47) are tail heavy and hoover tail low. Because of the weight and CG the forward pylon/rotor is angled forward to remedy this. Also the thrust vector in forward flight helps compensate for the aft CG and reduces the stress on the forward module and rotor hub. Hopefully one of the more aero-savvy types will confirm or correct me.

 

[VTOLicious]

My understanding is that both rotor shafts are tilted forward by design so that the fuselage can be horizontal in cruise flight (for drag reduction). Consequently, the tail must be low during hover (rotor shafts vertical)*.
So far so good, I'm just wondering why the rotor shafts are not designed parallel to each other.

*Of course tandem helicopters can be trimmed by cyclic AND collective pitch input. However, if the CG is at its optimal position no cyclic input is required and collective pitch is equal on both rotors during hover.

 

[Yellow Palace]

My understanding is that both rotor shafts are tilted forward by design so that the fuselage can be horizontal in cruise flight (for drag reduction). Consequently, the tail must be low during hover (rotor shafts vertical)*.
So far so good, I'm just wondering why the rotor shafts are not designed parallel to each other.

I thought it might be a stability thing, but it seems (based on a simple understanding) like canting the rotors in the opposite direction would work better for that. It does seem to be repeated on other twin-rotor helicopters - but not all, the V-12 doesn't do it - so there's presumably an advantage.

 

[TomcatViP]

The lift generated by the rotor is a function of the speed of the airflow. The part of the front rotor that is overlapped by the rear one generates two times the lift generated by each rotor as seen independently.

The lift is the cosinus part of the thrust generated on the shaft.

To banlance the lift generated on each shaft, the front one must be angled further than the rear one. Hence the aggravated angle

 

[VTOLicious]

Thinking about it I came to the following conclusion:
In forward flight the rear rotor catches a lot of "dirty air" from the front rotor, hence the lift of the rear rotor is reduced (equal collectIive pitch settings).
To equalize the vertical lift components (without increasing the collective pitch at the rear), the front rotor is designed with a greater forward-tilt.