Why did this idea never "take-off"?

Yes TTP the British were the first but the Russian were the first to perfect it and take it to max. speeds.

Kabir,

Did a quick search concerning the contra-rotating props, the TU-95 first flew in the early 1950’s the British were fitting contra-rotating props to Shackeltons and Fairy Fireflys in the mid to late 1940’s also tthe American Northrop XB-35 Flying Wing was originally powered by contra-rotating props in the late 1940’s and eventually jets. My guess is the British were the first to use them.

Kabir,

The double prop idea is not of Rusian origin, the Brits used this on the Shackleton’s Griffon engines, after WWll The Unducted Fan, has the props on the rear of the engine, and the props themselves are vastly different from normal propellers, Thats like saying if an airplane has 2 wings its a copy of the Wright Flyer. If you could see the props on the unducted fan engine they are very “Twisted”
compared to a regular propeller.

TTP, the idea indeed of the double propellers was taken from the TU 95.

Kabir

The engine was nowhere akin to the TU-95, They were designed originally in the late 70’s early 80’s as a more fuel -efficient powerplant, others have mentioned the various drawbacks these type engines had, but ultimately it was the price of fuel staying stable that caused the death of these engines. Boeing had a 727 rigged with one of these as well,

Oh yes definitely. With such progression on the jet engine it would be a backwards step to start relying on turboprop aircraft again, even internally for MD it would of been a step backwards.

efficient yes but i think if this was succesful it would have been seem like aviation technology going backwards instead of forward.

Well the aircraft would have been an ideal solution and was extremely efficient in terms of fuel. However, it never would have met the requirements for noise plus the problems with vibrations could never be solved. Also there were limitations to its speed as it could never run efficiently at jet speeds but more like a turboprop’s. Generally it would have been good in the times of high fuel prices but as they were reduced airlines were not interested.

sad….but even like that it will look good in my backyard.

And here it is today… rotting! 🙁

Cheers for all the info guys. 🙂

These engines were made or inspired by the engines of the Russian TU 95.

ahh they operate at more efficient speeds, arent required to burn as much fuel to get the requisite air through(supposedly!).

The very fact that the air isnt chanelled directly at the blade faces doesnt help matters.

they are probably loosing energy a fair amount by turning those hubs, overcoming friction in the bearings for the hubs etc etc, whilst also driving the compressor system inside the engine. (although there is less of a ‘high’ pressure section.)

its just not that much more efficient than anything else. I would imagine that there would be serious vibration problems requiring weighty props, and xtra padding in the fuselage walls, as the tips of the blades are probably reaching the speed of sound (even though the blade is allowed to go that much faster by sweeping the blade tips scimitar fashion. This vibration sensitivity would hold the blade to ransom on occasions such as turbulence.

coanda

How exactly did these engines work – in what ways were they more efficcient than a turbofan?

This particular aircraft was last seen hanging by the tail from a bridge in some action movie, the name of which escapes me at the moment. It was supposed to represent a crash of an airliner.

The unducted fan project has been dropped, as it was not giving the resaults hoped for.

Looks very interesting. Was it lack of funds/orders etc. as with most ideas?