A.net photo

I believe its called a fanjet or propjet or something along those lines, I can't remember exactly. However, obviously, it was not a very successful design.
 
The only word that came to mind when I saw that was "painful." Looks like some kind of torture device!

J.
 
If you look at the side it says "UDF"
Stands for Unducted Fan. Basically a turbo-fan engine with no nacelle around it. I heard the design was fairly promising...
 
Yup; more efficient than a turbofan, but pax just don't like anything resembling a propeller!
 
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Would someone please tell me what I am looking at HERE? Thanks.

Ethan

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Remember that horrible video of the MD-80 Testbed landing that snaped the plane in half? Well, there she is for ya!
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Nope, it actually wasn't. I believe the video was shot in the early/mid 80s...The plane flew again after the crash though.
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I heard it was more economical (fuel savings of 15-20%) and quieter than the average turbofan, but it would cost too much to get certified with the FAA unless the potential customers helped foot the bill. (No airlines were willing to do so, because when oil prices came down, it was cheaper to buy regular turbofans than to pay to certify UDFs.)

However, the research has continued, and the Antonov AN-70 aircraft in Ukraine is the first production aircraft to use unducted fan engines.
 
Supposedly the reason that the UDF never really caught on was due to the fact that it's incredibly noisy. It's actually a bit worse than the average turboprop, because you still have the added noise of the accelerated exhaust stream. The propeller tip speeds are also pretty high, since they are basically run off a free-power-turbine stage. Overall, it was a neat design, that had a low SFC (specific fuel consumption), and great performance in comparison to other engines in competition with it. But it was just too loud and had more vibration than a pure turbofan.
 
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