Airlinercafe Home Page

Stop being a lurker - join our community and get involved. Sign up and start a conversation!
 

      Author Message

      the PRIDEbird


      Members

       Online status  

       
      Add As Buddy
      Posts: 900
      Location: south of FRA close to RWY 18
      Occupation: window seat or aisle seat?
      Age: 52

      Post #54336, posted on 08-08-2014 GMT-5 hours    
      I wonder 'cause the new NEO engines are praised as something completely new.
      Already 30 years ago, back in the 80ies, they were called PropFan.

      New packaging - same content?

      Think it's the same: both have a fan with a gearbox!
      All major engine manufacturer worked on several projects at that time - russians as well.
      Some test flights were made. A 727 and a MD-80 flew with an unducted propfan.
      As far as I remember research and development were suspended
      due to lack of interest of airline industry.
      The NEO engine is a ducted propfan.

      Or needed development almost 30 years up to serial maturity and market launch?

      Sven

      Author Message

      727flyer


      Members

       Online status  

       
      Add As Buddy
      Posts: 135
      Location: Appalachian Mountains
      Occupation: Kerosene-burner
      Age:

      Post #54339, posted on 08-09-2014 GMT-5 hours    
      I thought one of the issues with the UDF was that it caused significant vibration on the pylon and rear fuselage... Or am I remembering that incorrectly??

      Mike

      "Looks like I picked the wrong week to quit sniffing glue!"

      Author Message

      aro757


      Administrators

       Online status  

       
      Add As Buddy
      Posts: 1864
      Location: San Ramon, CA
      Occupation: Software Engineer
      Age:

      Post #54342, posted on 08-09-2014 GMT-5 hours    
      I thought the UDF was much, much larger than these engines?

      Regards,

      ahmed

      Author Message

      jabrokaw2


      Upper Deck Member

       Online status  

       
      Add As Buddy
      Posts: 13
      Location: Brunswick, Maine
      Occupation: Retired computer programmer
      Age:

      Post #54343, posted on 08-09-2014 GMT-5 hours    
      This 2005 piece from Air & Space provides some interesting background. Incidentally, at some point in the early '80s I toured NASA Lewis and heard quite a bit about unducted fan research. Seems to me at that point they were experimenting with achieving noise reduction in the cabin via (among other things) external loudspeakers that would produce a noise cancellation field.

      Author Message

      Jennings


      Contributors

       Online status  

       
      Add As Buddy
      Posts: 3955
      Location: The great desert southwest, USA
      Occupation: Nurse Anesthetist
      Age: 116

      Post #54345, posted on 08-09-2014 GMT-5 hours    
      A geared turbofan isn't remotely the same thing as a UDF engine.

      Author Message

      LH707


      Upper Deck Member

       Online status  

       
      Add As Buddy
      Posts: 1016
      Location:
      Occupation:
      Age:

      Post #54364, posted on 08-12-2014 GMT-5 hours    
      I think there's some confusion here. The A320ceo has either CFM56-5Bs (early ones had -5As with shorter intakes) or V2500s, both with a fan diameter around 65". The neos have either the CFM Leap-1A (78" fan) or the PW1130G-JM (81" fan), both of which are turbofans, not UDFs. The PW has a 3:1 fan gearing, which lets the LP shaft spin faster. Because power=torque*RPM, the LPT does more work per stage, so they can put fewer stages in. Also, the fan spins slower, which helps at greater diameters, because the blade tip speeds can be kept under control.

      In a very basic sense, the Leap engine has a hotter core with more unobtanium, while the GTF uses the gearing for a more efficient LP shaft. There are a couple articles on the topic you may want to read:
      http://airinsight.com/2011/11/09/comparing-the-new-technology-narrow-body-engines-gtf-vs-leap-maintenance-costs/