Flying-boat tiltrotor catamaran design wins NASA compo Engineering students in America have won a NASA competition with their design for a combination aeroplane/helicopter/catamaran rescue craft. Students from Blighty worked on the runner-up design, a quadruple-rotor version of the famous V-22 "Osprey" craft. The RAFT civil ops tiltrotor concept. Credit: Michael P Creaven Two …
Neither White Knight or any catamaran sail boats have quite the levels of torque way outboard of the hulls. Those rotors will put as much torque through the outer wing, hulls, and inner wings as they put into the air to create lift, which could potentially be quite a lot. And since the rotors clearly spin in the same direction (Judging from the picture, anyway, could just be lazy CAD not lining up with the specs on paper) there's basically no way that you could achieve torque balance with the engines on. So as the original poster said, it probably won't be able to sit in one place even on the ground, has nothing to do with whether the structure will hold up, though that center wing does look a bit on the lean side.
I love the way that the props on that first one are clearly much too large to allow a 'normal' landing without them fouling the ground / water - that is going to catch out lots of pilots, like the way that the Harrier requireing greater power when coming in to land, has caught out quite a few pilots who are used to throttling back.
Seems to have rather large propellors. If I had been involved, I would have made sure the thenengine was sufficiently high above the ground to allow the prop to rotate. Perhaps this is the HP approach to selling stuff - capital outlay is low but you spend a fortune replacing the props after every take-off and/or landing.
In open oceans, one typically sees long wavelength waves (sorry), of varying heights. Wave height usually isn't a problem, as the change is smooth.
Well, that is until you stick massively long wings on the aircraft and add heavy weights to the ends. The impact of a wave against this structure may be minimal, but the impact of cold water against a hot engine would not be ideal. The impact of a barely subsonic spinning rotor blade hitting the sea would be phenomenal: destroying blades, gearbox, engine, wing and most of the aircraft too.
Bring back the PBY Catalina - or the Short Sunderland...
but with modern more powerful engines. They can do the rescues where legs are needed otherwise it's the jolly old Sea Kings or Merlins etc.
Mmm Catalina....there's a beautiful aircraft.
Needs propellors ...and fifty cal guns....never have too few fifty cal guns.
Its the same reason as the V-22... Get there fast, hover, get out fast...
When you have people in the water, you have a limited amount of time before they either a)drown, b) die of hypothermia or c) get eaten by a shark. Going there in a regular helicopter is time consuming and not good. The idea behind this project is you fly there at 300knots (about 3+ times regular rescue helicopter speed), hover, pull off your rescue and then get back to the nearest hosptial (again at 3+ speed). Time savings would be immense.
Only real problem i can foresee with these types of solutions is that since our rescue services are increasingly operating on shoe string budgets (thank your lovely goverment for that), the additional maintenance costs and requirements of a tilt rotor may actually render it uneconomical pretty quickly (the cost of saving x number of extra people per year v additional maintenance costs) Lets hope the beancounters dont get to decide this one!
This is why engineering students design planes and commentards don't. Dealing with your comments in turn:
Re: Richard Cartledge (oh dear): there've been a few planes with some sort of dual-fueselage concept, Rutan's WK2 as James Hughes 1 points out, Boomerang (also Rutan), North American F-82 off the top of my head.
Re: The First Dave (untitled) - and you don't think the fact you have to land in what is called "helicopter mode" might be covered in the conversion course before pilots are allowed to fly this type of aircraft?! Re your Harrier comment its actually quite common for planes to require more power on the approach due to how the drag curve works out, Harrier crashes are probably more due to them just being damn hard to fly.
Re. the above and AC (Two Hulls Better Than One?): The reason for the large props is probably to give either acceptable performance (fuel economy or hover weight capacity) or an autorotation capabiltiy, i.e. the ability to land vertically after total engine failure. Which helicopters can do, but the V-22 can't, which is clearly a major safety risk during helicopter-mode operation. Being able to land in "conventional mode" (i.e. props forward) might give a payload improvement but might not be an acceptable trade-off for this. Clearly you don't replace the props after every take off and landing, what on earth are you on about?!
Re: JasonH (Erm, bolox): I'm sure wave impact on the structure wouldn't be minimal! No-one has ever operated flying boats or seaplanes in signficant waves, there's all kinds of operational limits (forces on the hull for landing/takeoff, control, spray ingestion by the engines, prop clearances etc),. I've been out in a kayak in Moderate (sea-state four) conditions and it wasn't rough.
David Evans (Fail): Glad you've done the CFD to study the prop-wash issue then. Its a valid concern, but not necessarily a "fail". There's been a few aircraft with push-pull engine configurations (e.g OV-10 Bronco) and it doens't seem to have been a killer. You have to take the "twist" the front propellor gives to the inflow to the rear propellor into consideration when selecting the pitch profile for the rear prop, but in some circumstances it can actually mean that you can actually stuff more power through the rear prop than would usually be the case for it's size. I agree though that the interaction during transition from vertical to horizontal flight would be a risk which would have to be looked at.
"""Re: Richard Cartledge (oh dear): there've been a few planes with some sort of dual-fueselage concept, Rutan's WK2 as James Hughes 1 points out, Boomerang (also Rutan), North American F-82 off the top of my head."""
Again, this Richard Cartledge never said anything about dual-fuselage, he just said """the stresses and strains would be colossal, I doubt it could even stay in one piece sat on the ground.""" which is a valid observation, given two massive props rotating in the same direction. As soon as you started powering that thing up on the ground, it would start spinning, which is sort of a catastrophic failure.
Also the Osprey, the only really similar aircraft, has some seriously reinforced wings to be able to take the vertical force from the props, and this design doesn't seem to have large enough (in cross-section) wings for that. Plus the Osprey has just the one fuselage, and shorter wings. The stresses from load in the twin fuselage combined with the rotors, not to mention potential odd torques from waves at 45 degree angles really insist on, at minimum, more structure between the hulls, if not some beefier outboard wings as well.
I applaud another effort from NASA for sponsoring innovation in engineering. However, I'm not convinced as to the actual aerial/sea/ground-based utility and necessity of such innovative vehicle designs - or whether those designs would really add so much to the features of the existing rotary-wing helicopter platforms, and without detracting too much, on basis of costs of manufacturing and maintenance.
But hey, if the pres says you can't go back to the moon, after all, have to look somewhere to keep things going, right?
Nothing inherently wrong with a twin-fuselage design - a wider footprint makes you safer in waves - but it has its limitations.
Actually having two separate passenger-containing compartments is a bit daft though. Much better to do something akin to the WWII Whirlwind - central main fuselage for people (and anything else) and booms outboard of that. That way the booms can be engineered to be structurally strong without needing a load space inside. It also resolves the problem of big torsional forces on the central wing section due to a difference in loads in the two fuselages. With suitable design you could even fill those booms with water for fire-fighting if you paid close attention to anti-slosh and loading up the booms evenly side-to-side and front-to-back.
Mind you, just having outrigger floats is a perfectly good solution, which virtually all larger flying boats used.
I'm a little confused about what the students are supposed to have been contributing though. If they're GCSE-level students on a "here's-how-to-use-a-3D-design-package" course, then fine. But if they're uni-level students who were supposed to know something about aeronautics, I'd be a bit worried. The size of props in that firs design simply ain't happening.
Remember the down wash throwing people aside and stories of buckling deck plates; and here we are working on a bigger setup, more air volume and heat AND it operates over water. The water might solve the heat problem but the down wash will kick up such a cloud of water and water vapour it will kill the engines if in fact the crew can see to fly anywhere in a permanent mega monsoon.
And another thing, sea state four; how is anything that big supposed to get off the deck with one rotor up in the air and the other in the drink?
Barking mad
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