Fairey Rotodyne

[kitnut617]

Nick, Simon,

What I can hear is the very deep throb the props put out, if you've heard a C-130 or a DHC-5 Buffalo you'll know what I mean. It is like Simon says, only for about 30 seconds to a minute in duration, so I'm assuming it must be directly west of me when I hear it.  I can never see them though, even on a clear day.

Same thing happens when a Huey comes by (or the MBB aero-ambulance), I can hear it for miles, then all of a sudden it goes quite, I know then it has just passed me so I look in that direction and usually I can spot it quite quickly after that.

[Mossie]

This sounds about right, IIRC it's something to with standing waves.  It'll be a certain wavelength your getting & why it'll be limited to certain types that give off just the right frequency.

[kitnut617]

On the cover of this quarter's Air-Britain's Aviation World, is a photo of the Eurocopter X3 taking off on it's first flight.  I've not seen (or heard) of anything about this helicopter but it is very interesting that it's layout is a lot like a Rotodyne.  Googling it I find it works much the same.

[Mossie]

I think there was a thread on it a litle while back.  Eurocopter have basically whiffed a Dauphin in 1/1 into a compound helicopter demonstrator.  It's kind of like a Rotodyne in reverse.  Whereas in the Rotodyne the prop engines provided the main thrust & compressed gas to the tip jets, the X3 has a driven rotor in the manner of a conventional helicopter that also provides power to the props.  I'm not sure if the props in the X3 are shaft driven or by compressed gas.

[apophenia]

... I'm not sure if the props in the X3 are shaft driven or by compressed gas.

The X3 props are shaft-driven. There's a pair of power take-offs at the front of the modified EC175 gearbox.

[rickshaw]

On the cover of this quarter's Air-Britain's Aviation World, is a photo of the Eurocopter X3 taking off on it's first flight.  I've not seen (or heard) of anything about this helicopter but it is very interesting that it's layout is a lot like a Rotodyne.  Googling it I find it works much the same.

There was nothing wrong with either the concept or the practicality of the Rotodyne.  It was the lack of political and financial will which destroyed it in the end.

I've been thinking lately about an AEW version with fore and aft radomes (and perhaps extended undercarriage to raise the fuselage sufficient so that the pilot can see over the forward radome ).

[PR19_Kit]

There was nothing wrong with either the concept or the practicality of the Rotodyne.  It was the lack of political and financial will which destroyed it in the end.

The noise didn't help, and I wish I'd heard it after they'd allegedly sorted the problem out. Unfortunately every time I see the word 'Rotodyne' I always hear that HORRENDOUS noise! 

[rickshaw]

There was nothing wrong with either the concept or the practicality of the Rotodyne.  It was the lack of political and financial will which destroyed it in the end.

The noise didn't help, and I wish I'd heard it after they'd allegedly sorted the problem out. Unfortunately every time I see the word 'Rotodyne' I always hear that HORRENDOUS noise! 

Thing is, the V-22 is apparently just as if not even more noisy than the "sorted out" Rotodyne but we don't hear any criticism of it in that department.  The Chinook was/is bloody noisy as well.   The difference is of course they are operating in a military environment where you can just hand out earplugs to satisfy Occ. Health and Safety regulations about noise.  Civilian operators couldn't or rather wouldn't.  I'm looking forward to seeing how the civilian operators of the various planned tiltrotors will handle the problem.

[PR19_Kit]

Having heard all three, Rotodyne, Chinook and V-22, albeit with the 'dyne in LOUD mode, I'd be pretty impressed if Fairey/Westland had managed to quieten it enough to be competitive with the latter two!

The characterstics of the tip jet noise were totally different to the low frequency 'Whump - Whump' you get from a Wokka or a V-22. The tip jets roared, and I do mean ROARED! I could hear them light up from over a mile away, and they'd have had to do some serious work to alleviate that. I wish there were some sound tracks of the quietened 'dyne still around, but it looks as if all those records were lost.

We'll just have to build another one and find out! 

[Mossie]

Well, it'll still have been noisy, but Fariey/Westland had done enough to get it within regulations of the time & still had some more tricks in the bag.  A modern 'Rotodyne' would have much more stringent regulations to comply with & although more is understood about noise reduction, it'd probably still be a significant develomental hurdle to get over.

I'm hoping we see something of the Groen Brothers project, it's been a little quiet since the DARPA program was announced.  The X3, although looking similar in layout uses a different approach with a directly driven rotor.  The GBA proposal is the only one that would fully ressurect the Rotodyne tip jet technology, if it ever goes ahead.

[rickshaw]

Of course the other difference between the 'dyne and the V-22 is that the 'dyne only used its tip-jets during take-off and landing whereas the V-22 uses its rotors the whole damn time.  Also as I've pointed out and as Mossie has reminded us, a civil aircraft faces very different regulations compared to a military one.

Is Gibbings' book on the Rotodyne any good?

[Hobbes]

What was the reason to use tip jets on the Rotodyne? I'm guessing weight issues?

[rickshaw]

What was the reason to use tip jets on the Rotodyne? I'm guessing weight issues?

Simplifies the rotor head and alleviates the need for a heavy, complex transmission between the engine and the rotor.  Yes, saves considerable weight and reduces torque as well - no torque, no need for a tail rotor.

[kitnut617]

There was nothing wrong with either the concept or the practicality of the Rotodyne.  

I didn't say there was, I for one, like the concept and have no doubt that a solution to the tip jets would have come about.  

What I like about the V-22 is that it does use it's engines 100% of the time, my pet pieve is aircraft designs that have equipment that only serves one purpose and for the rest of the time is just dead weight being hauled around.  To me it just doesn't make sense.

The reason I brought the X3 up, is it answers a number of things to solve a very large transport type.  I've been thinking about a converted C-130 or C160 Transall, only I would use the engines in the nacelles for the power (so they're used 100% of the time) and have a disconnect for the main rotor when it goes into auto-rotation.

I had noticed when I looked at a Sikorski X2 website, that their transport design goes the same way as the X3 only it still has co-axial rotors.

[PR19_Kit]

Is Gibbings' book on the Rotodyne any good?

Yes, well recommended, see my quickie review in post #17 above.