Boeing CH-47 ULOR

hesham

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Hi,

http://www.aviationweek.com/aw/blogs/defense/index.jsp?plckController=Blog&plckScript=blogScript&plckElementId=blogDest&plckBlogPage=BlogViewPost&plckPostId=Blog%3A27ec4a53-dcc8-42d0-bd3a-01329aef79a7Post%3Afbf422c7-8568-41f8-87e2-2b3e5c5f806a
 

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SteveO

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Fascinating, but does this arrangement have advantages over a fuselage mounted set of wings?
 

Abraham Gubler

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SteveO said:
Fascinating, but does this arrangement have advantages over a fuselage mounted set of wings?

Structurally yes. If you were to mount wings on the fuselage you would need to add a structure so the wings could support the weight of the helicopter when they generate lift. By adding the wings to the blade hub the structure is already there to support the weight. So when the helicopter starts to move forward the wings start to generate lift the pilot can unload the rotors yet the hub will keep on 'holding' up the aircraft.
 

yasotay

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Abraham Gubler said:
SteveO said:
Fascinating, but does this arrangement have advantages over a fuselage mounted set of wings?

Structurally yes. If you were to mount wings on the fuselage you would need to add a structure so the wings could support the weight of the helicopter when they generate lift. By adding the wings to the blade hub the structure is already there to support the weight. So when the helicopter starts to move forward the wings start to generate lift the pilot can unload the rotors yet the hub will keep on 'holding' up the aircraft.

Also no down force on the wings if they are mounted above the rotor system. A classic issue for winged helicopters. Although I have to wonder if there are any issues with the induced flow or any issues with tip vorticies from for forward wing on the aft rotor?
 

Abraham Gubler

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yasotay said:
Also no down force on the wings if they are mounted above the rotor system. A classic issue for winged helicopters. Although I have to wonder if there are any issues with the induced flow or any issues with tip vorticies from for forward wing on the aft rotor?

Good point about the downwash on the wings. The wings would very rapidly take up the bulk of the lift duties over the rotors. The AH-56A originally had the rotor completely unload to its wings but during development a 20% load on the rotor was restored to improve stability. The rotors would be in the main just windmilling along during cruise flight. So I'm not sure if turbulence from the forward wing would be of too much worry on the aft rotor.

Also the wings mounted above the hub don’t impinge too much on the H-47's footprint. Adding conventional wings like on the Boeing Model X347 creates a very different footprint making for new taxying, loading, hangar, etc demands. The above hub wings consume space already occupied by the rotors and could be very easily folded 90 degrees to reduce width to that of the fuselage (they would have some sort of slip ring arrangement to stop them spinning with the rotors so rotating them for storage would be a piece of cake).

Also again said wings can be very high aspect ratio (and they are) for minimal drag at speed without being unwieldy on traditionally narrow helicopters. Because the rotors provide lift for takeoff/landing and slow speed flight there is no need for the better lift of low aspect ratios at slower speeds and their higher drag

Any other advantages?
 

AeroFranz

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I still think those wings have a negative effect on lift, regardless of the fact that they are not in the exhaust of the rotor. If we look at the hover case (which defines maximum power requirements) half the thrust is being generated by accellerating the flow before the rotor disc and the other half after. At least this is true with propellers in axial flow, but a rotor in hover should be the same. My point is that those wings still present some blockage to the flow, which has to go around pretty much a flat plate to get to the rotor. Then you get into issues of non-uniform flow to the rotor disc, giving you a lower figure of merit/efficiency.
Still, it's probably not as bad as if they were in the exhaust. If they can, they should tilt up the wing (V-22 lowers the flaps in a similar bid) according to flight regime, but that adds complexity.
 

yasotay

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Abraham Gubler said:
The rotors would be in the main just windmilling along during cruise flight.

This assumes auxillary propulsion I think. Does not look like there is any on the model. So I think the rotors will still have to provide thrust. I agree that in forward flight there would be no issue of interference, however in transition I have to think, as AeroFranz points out, that there could be some interference. Probably not enough to be overwhelming, nor something a fly by wires systems could not deal with.

Interesting idea, however without new engines, it is adding weight to an already weight challenged aircraft. The loads for the CH-47 are getting heavier. If this gives a huge boost to the aircrafts overall efficiency, then it might get some traction.
 

yasotay

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Re: Boeing Future Transport Rotorcraft for European requirement?

And then there was this interesting proposal on the opposite wall.
 

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Matej

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Re: Boeing Future Transport Rotorcraft for European requirement?

yasotay said:
Found this on a side wall at the Boeing pavillion at AHS. Note the German markings.

It was said before that the Boeing is very active since France and Germany refused to develop all new design (Eurocopter HTH) to replace the aging CH-53.
 

fightingirish

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Re: Boeing Future Transport Rotorcraft for European requirement?

Note the German markings.
Yes, it seems that the HTH/FTH program (CH-53G successor for the Heeresflieger / German Army Air Corps) is going more forward to a tandem rotor heavy-lift helicopter.
Even EADS/Eurocopter is promoting a tandem rotor helicopter.
See thread "Eurocopter HTH".
 

turboshaft

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Now available in Apache flavor (low-res image from AAAA Annual Convention c/o Flight International's Steve Trimble).
 

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Triton

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Boeing Unloaded Lift Offset Rotor (ULOR) configuration features

Source:
http://www.aofs.org/wp-content/uploads/2012/11/121122.18-Rotorcraft-Back-to-Future-Davis.pdf
 

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Triton

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Model of Boeing ULOR on display at the AHS International 69th Annual Forum & Technology Display, May 20-23, 2013, Phoenix Convention Center, Phoenix, Arizona.

Source:
http://vtol.org/qr/forum-69-photos
 

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SteveO

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Weird cockpit window layout. I thought pilots preferred horizontal and vertical lines on the frames.
 

SpudmanWP

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After seeing that and all you can say i the windows are weird? ;)
 

F-14D

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Gee, you'd have thought that they'd have shown a KC-46 as the refueler!
 

SteveO

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SpudmanWP said:
After seeing that and all you can say i the windows are weird? ;)
;D Yeah, it's been shaped by an ugly stick from the look of it. I was hoping for something that looked more like the Boeing 360 http://www.secretprojects.co.uk/forum/index.php/topic,4095.0.html
 

yasotay

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Likely that it is a necessity of a higher speed rotorcraft that does ~200 knots on a regular basis.
 

Triton

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Should this topic be named "Boeing CH-47 ULOR"? It appears to be a new helicopter with a family resemblance to the CH-47 Chinook rather than a modification of the existing design.
 

Avimimus

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Yes - hard to bill this as a mid-life upgrade...

Btw, I take it the ULORs are used to shift CG at low speed?

Interesting.
 

yasotay

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Avimimus said:
Yes - hard to bill this as a mid-life upgrade...

Btw, I take it the ULORs are used to shift CG at low speed?

Interesting.
It could be but I also think that the focus is to off load the rotor system at high speed flight.
Given all the tilt shown of the wing, the rotor hub, transmission and everything associated with the dynamic components would be very interesting.
 

Kartek

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The prop-fans indicate the wings are there to unload the rotor and increase speed, but they are going to introduce turbulence to the downflow which will increase rotor fatigue.
They definitely fail the "if it looks right it will fly right" maxim, but damn interesting anyway.
 

jsport

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Thank you Kartek for pointing out the rotor fatigue issue. :)
 

aeroengineer1

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Fatigue will not be much of an issue especially in the age of composites. Composite rotor blades are stiffness designed, not strength. Many times the factors of safety are >>1.5. The areas around the attachment points are the areas that are strength designed, and most of these are governed by Ground Air Ground (GAG) cycles. This is just a generalization, and each design can have its areas that are governed by strength.
 

jsport

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thank you for even more information aeroengineer1.
 

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