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The MD-90 And UHB Fans  
User currently offlineBoeingmd82 From United States of America, joined Jun 2001, 238 posts, RR: 1
Posted (12 years 11 months 1 day 4 hours ago) and read 3797 times:


I remember that early in the MD-90 development they were going to use an ultra-high bypass unducted fan engine to power it. I think I remember seeing it installed on a B727, it looked pretty vicious. I wonder if there were any jets built that utilize this and who owns the technology now? Would it be a good alternative to power todays jetliners?

Thanks in advance for any repsonses.


9 replies: All unread, jump to last
User currently offlineZiggy From United States of America, joined Jun 2001, 178 posts, RR: 0
Reply 1, posted (12 years 11 months 1 day 2 hours ago) and read 3695 times:

P&W has a PW4000-112" with a BP ratio of 5.8-1 to 6.4 to 1. They state that such A/C 777 is what it is being installed on. I however do not know anything about he MD-90. I hope this is what you were asking.  Smile

User currently offlineTwotterwrench From , joined Dec 1969, posts, RR:
Reply 2, posted (12 years 11 months 1 day 1 hour ago) and read 3686 times:

I work with a guy who worked flight test on that MD you are talking about. The problem they had was vibration from the fan. It was incredibly efficient and would be an ideal solution, except that the vibration problem couldn't be solved. I will ask him for more details tomorrow. Interestingly, the aircraft MD used as a test bed for that was an aircraft that had been crashed and had the tail torn off during flight testing of another kind. My buddy was on it when it crashed that time. They beat it back together and since it wasn't good for sale to anyone, it go sent to the unducted fan flight test program. Like I said, I'll try to get details tomorrow from Scott. Maybe pics too.

User currently offlineWilcharl From United States of America, joined Jun 2000, 1165 posts, RR: 3
Reply 3, posted (12 years 11 months 1 day 1 hour ago) and read 3678 times:

An Aerospace Enginnering professor @ Embry Riddle once commented that just prior to them stoping the program, one of the enginners an ER graduate had left a maglite in the cowling when one of the UDF engines was in the test cell. They started it up and clank clank we all know how it goes, the engine had severe FOD damagae, and the cost to replace the engine, plus the excessive noise and vibration, brought the program to a hualt. This is unverified, anyone out there that can verify this?

User currently offlineDelta-flyer From United States of America, joined Jul 2001, 2676 posts, RR: 7
Reply 4, posted (12 years 11 months 1 day ago) and read 3670 times:

Whoa, Wilcharl, that is a bit far-fetched. What brought it to an end was the drop in fuel prices in the early 90's, making the efficiency improvement less attractive in view of the cost of developing the technology. If the program were truly viable, they would have replaced the broken parts.

The other problem is as Twotterwrench mentioned - the vibration. This would have made it expensive to refit existing aircraft.

I worked on the GE36 propfan which was test flown on the 727 someone mentioned above. I designed the hydraulic motor that controls propellor pitch. It was a fun project, I got to know some GE engineers. We were all sorry to see the project cancelled just when we were about to see some results.

By the way, just as an aside, the president of Airbus called this technology the "whirling bananas".

User currently offlineFBU 4EVER! From Norway, joined Jan 2001, 998 posts, RR: 7
Reply 5, posted (12 years 11 months 7 hours ago) and read 3647 times:

I remember SAS was quite interested in the unducted fan possibilities during the mid-late 80's.What we learned was that the unducted fan had to be certificated as a turboprop engine with the resulting demands on design as to a blade coming loose.
Jets seem to have more lenient certification criteria on this matter as there is a cowling that would contain a blade coming loose and the resulting unbalance vibrations would be manageable.On the UDF it could be hell.Thus the demise?

"Luck and superstition wins all the time"!
User currently offlineWilcharl From United States of America, joined Jun 2000, 1165 posts, RR: 3
Reply 6, posted (12 years 11 months ago) and read 3643 times:

I figured it was pretty far fetched, but it made a good story to tell, and i know of times when programs that are not doing well get mothballed when one of the prototypes are destroied so hey...

User currently offlineAeroguy From United States of America, joined Aug 2001, 69 posts, RR: 0
Reply 7, posted (12 years 11 months ago) and read 3656 times:

It's too bad about the UDF engines not having any commercial success, they were a really neat design. I guess the public is a little wary of engines that are or resemble turboprops though. I think the GE/NASA team actually received the Collier Trophy in 1987 for their work on UDF development.

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Photo © Paul Dopson

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User currently offlineBoeingmd82 From United States of America, joined Jun 2001, 238 posts, RR: 1
Reply 8, posted (12 years 10 months 3 weeks 6 days 2 hours ago) and read 3626 times:

Thanks to all for the great information and pictures. What an awesome looking powerplant! Too bad the technology turned out not to be viable. It would have been so cool to see those little B717s buzzing around with UDF engines!



User currently offlineCritter592 From , joined Dec 1969, posts, RR:
Reply 9, posted (12 years 10 months 1 week 5 days 6 hours ago) and read 3566 times:

The MD95 looks good without it, Don't make a pretty bird look so ugly

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