Boeingmd82 From United States of America, joined Jun 2001, 236 posts, RR: 1 Posted (12 years 3 months 3 weeks 2 days 6 hours ago) and read 3337 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?
Ziggy From United States of America, joined Jun 2001, 178 posts, RR: 0 Reply 1, posted (12 years 3 months 3 weeks 2 days 4 hours ago) and read 3235 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.
Twotterwrench From , joined Dec 1969, posts, RR: Reply 2, posted (12 years 3 months 3 weeks 2 days 3 hours ago) and read 3226 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.
Wilcharl From United States of America, joined Jun 2000, 1158 posts, RR: 3 Reply 3, posted (12 years 3 months 3 weeks 2 days 3 hours ago) and read 3218 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?
Delta-flyer From United States of America, joined Jul 2001, 2676 posts, RR: 7 Reply 4, posted (12 years 3 months 3 weeks 2 days 2 hours ago) and read 3210 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".
FBU 4EVER! From Norway, joined Jan 2001, 998 posts, RR: 7 Reply 5, posted (12 years 3 months 3 weeks 1 day 9 hours ago) and read 3187 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?
Aeroguy From United States of America, joined Aug 2001, 69 posts, RR: 0 Reply 7, posted (12 years 3 months 3 weeks 1 day 2 hours ago) and read 3196 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.
Boeingmd82 From United States of America, joined Jun 2001, 236 posts, RR: 1 Reply 8, posted (12 years 3 months 2 weeks 5 days 4 hours ago) and read 3166 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!