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Classic aviation fans - Fairey Rotodyne

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marcus:
On the way back to London from a festival about 5 years ago I saw two Bell V 22 Ospreys flapping across London, and after doing my usual research it seems to me that the Rotodyne is a much better package, particularly for military operations. Any damage or failure of either V22 engine is basically a total loss scenario, whereas the Rotodyne can land and take off safely in auto-rotate. Even total loss of one engine is survivabe, and could still leave you with several chances of making an emergency landing, whereas even with a helicopter you only get one chance at most.

At Farnborough Air Show Brazilian plane builder Embraer announced plans for a VTOL airliner, and the suggestion is that it could be like an updated Rotodyne. Modern engines, props and rotors are far cleaner, quieter and more fuel-efficient, and after seeing these films I am convinced that the Rotodyne concept was way ahead of its time and likely to reappear in an up-dated form, so I look forward to seeing more details from Embraer. If they DO follow that model, I am sure the US Marines will instantly switch allegiance from the V 22 which is exceptionally expensive and has serious doubts about its suitability for ops.

Chris Thomas:
Dear Marcus

I know nothing about aircraft but one thing that strikes me about the rotodyne was the restriction on top speed due to the helicopter type rotor blades. We know that due to the speed of the tips of the blades on a helicopter, added to the forward motion of the craft, the blades create a small sonic boom, and getting faster than that becomes a problem. Therefore why have an aircraft that can not go any faster than a helicopter. The B22 Osprey with the tilting wing does allow for the plane to take off almost vertically and then turn to become a conventional typle plane that can presumably go at twice the speed of a helicopter, but also very slowly when needs require.

As a kid I can remember reading a copy of Popular Mechanics or a similar American magazine dated about 1956 in which both designs were being showcased as being the future of passenger aviation. Now 60 odd years later they are used by the military and other specialist agencies, and not for main stream passenger use.

Chris Thomas

Big Al:
There has been talk of a autogyro with ramjet powered main rotor thus avoiding the complication of gearbox, large engine, extra weight and so forth. Thus to hover it functions as a helicopter but in flight acts as an autogyro without the additional power. However there is a drag issue on all these spun rotor jobs. There is an issue with blade going supersonic to. Of course you can design for supersonic rotors but that is heading into reusable space craft really.

marcus:
It's true that any rotary wing aircraft has limited speed, but the Rotodyne was exceptionally fast in its day, I think 190 knots. The V22 is almost twice as fast, but also has speed limitations and noise/fuel issues due to the large size of its propellers. It also has no forward-firing gun so it is very vulnerable in close support ops/Marines use.
But speed is only one aspect of any craft's capabilities, and it is not necessarily important for lots of situations, like shortish flights (City to City), military use, and activities in remote regions: mining, forestry/logging/firefighting, medical/food/drought/flood, as well as special events like getting people to festivals and sporting events. The Rotodyne concept allows VTOL, safe transition to forward flight similar to autogyros or helicopters plus a much better degree of safety in the event of engine failure. With sufficient fuel it can also hover.

Certainly it would serve in niche markets rather than mass transport, but these niche markets exist and can be profitable

marcus:
Some RAF Hercules transports are fitted with Rotol props with six scimitar/crescent shaped blades which are far more efficient at higher tip speeds, and also a LOT quieter. If these can be scaled up to rotary wing size performance will increase.

I did notice a standard Police helicopter hovering over Guilfest, Guildford, Surrey a few years ago and it was far quieter than other helis, just a fan-like "wash" of sound without the clatter, presumably these are specially shaped blades, but I could not really make out their shape, but the tips of rotors are crucial to aerodynamics.

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