The Unducted Fan

[ammorman]

Hello all. This is my first post so go easy on me I was wondering if anyone has any other information on the Unducted Fan engine?

http://www.youtube.com/watch?v=4lip8lPWFLo

[CAPFlyer]

It was a horrible failure. It was LOUD, it was a maintenance nightmare, it didn't save as much fuel as they wanted it to and when the fuel prices went down again, it was dead. However, Carbon Fiber technology, once developed more, allowed even better fuel efficiency with even more power produced per pound of engine with the GE90 actually burning less fuel per pound of thrust created than even the most fuel efficient turboprops.

[ammorman]

Ok thank you. I saw it in my A&P turbine book but it didn't say too much about it. Now I know why...

[CAPFlyer]

It was an interesting concept, basically being an oversized turboprop, it just failed because they didn't realize how many problems building an aft-fan turbine would be woth the fan exposed. I think they thought they could use the experience from the aft-fan turbofan they developed for the CV-990 from the J79 and it would scale up without problems.

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[ammorman]

It seems like the RPM of the fan would be one of the biggest issues. How did they control it? Was it just like a constant speed prop?

[pilotgod]

Here is some good reading on the Unducted Fan and its sibling the Propfan.

http://www.airspacemag.com/history-of-f ... p-fan.html

http://en.wikipedia.org/wiki/Propfan

http://www.britannica.com/EBchecked/top ... an-engines