Username or Email Address
Do you already have an account?
Forgot your password?
  • Log in or Sign up

    VWVortex


    Results 1 to 14 of 14

    Thread: Question for those who know about MD's

    1. Senior Member .LSinLV.'s Avatar
      Join Date
      Nov 13th, 2009
      Location
      Vegas Bitches!
      Posts
      29,009
      Vehicles
      00' VR6T 12' V6 TDI 72' 914-6
      03-30-2012 10:14 AM #1
      of all the AC I see on a daily basis, only one has the engines tilted down, the MD series. If anyone knows as to why, I'd like to know as this is a curious design. I'll have to check on the 95's and the 717's as I don't think these AC with the larger BR700 engines have this like the older AC with the JTD's.

      in fact, if the AC is horizontal in flight, the nacel's AOA seems like it might mitigate smooth flow into the engine, let alone vectored thrust out the back (which is down).

      anyway....just curious.

      TIA
      Larry

      Demokratikally Elekted Minister of Shekels of the Independent People's Republik of Offtopikstan

    2. 03-30-2012 10:21 AM #2
      Quote Originally Posted by .LSinLV. View Post
      of all the AC I see on a daily basis, only one has the engines tilted down, the MD series. If anyone knows as to why, I'd like to know as this is a curious design. I'll have to check on the 95's and the 717's as I don't think these AC with the larger BR700 engines have this like the older AC with the JTD's.

      in fact, if the AC is horizontal in flight, the nacel's AOA seems like it might mitigate smooth flow into the engine, let alone vectored thrust out the back (which is down).

      anyway....just curious.

      TIA
      I'm no engineer, but it would seem to me that it might have something to do with the way the air flows over the tops of the wings in a curved fashion (assuming you're just talking about aircraft with tail mounted engines).

    3. Senior Member .LSinLV.'s Avatar
      Join Date
      Nov 13th, 2009
      Location
      Vegas Bitches!
      Posts
      29,009
      Vehicles
      00' VR6T 12' V6 TDI 72' 914-6
      03-30-2012 11:15 AM #3
      maybe...but look at these images to better see what I am talking about:

      MD-80 Series


      MD-90 Series


      Boeing 717


      Here is the Boeing 727 Series, note the engines and their AOA, no noticable angle difference from fusalage.


      Llyshin II-62
      Larry

      Demokratikally Elekted Minister of Shekels of the Independent People's Republik of Offtopikstan

    4. 03-30-2012 02:57 PM #4
      Quote Originally Posted by joness0154 View Post
      I'm no engineer, but it would seem to me that it might have something to do with the way the air flows over the tops of the wings in a curved fashion (assuming you're just talking about aircraft with tail mounted engines).
      this or better takeoff performance?

    5. Member B3sat16v's Avatar
      Join Date
      Jan 23rd, 2002
      Location
      Around the world
      Posts
      7,403
      Vehicles
      MH-60R
      03-31-2012 06:33 PM #5
      It is PBFM! Most likely due to airflow, CG (Vectoring the thrust slightly downward keeping the nose down with low loads up front), to get the best answer you would have to ask an Engineer that designed these aircrafts. Any of our answers are going to be pure speculation.

      And the IL-62 has a downward tilt as well as the VC-10, and so does the 727. Your picture does not show it too well.



      And as we know the 727 has a nose low attitude with WOW.

    6. Member
      Join Date
      Dec 11th, 2002
      Location
      PNW
      Posts
      4,883
      Vehicles
      TDI Golf, CBR1000F
      03-31-2012 06:54 PM #6
      Here's what the original DC-9 manual says:
      "The nacelle axis and pylon have been set at 3 degrees angle of attack relative to the fuselage to align them with the local flow conditions prevalent at cruising conditions. This is necessary to eliminate the interference and high induced drag that they would otherwise be subjected to. The nozzle is then canted upward relative to the engine axis, thus eliminating the pitching effects due to thrust.
      The air coming of the back of the wing is headed down just a bit after following the camber of the top surface.
      If it's not foggy
      and you have your fog lights on
      you are a doofus.
      "Pro Tip: Don't **** with people who've been trollin' longer than you've been alive." - OOOO-A3

    7. Member Zombiee313's Avatar
      Join Date
      Apr 27th, 2011
      Location
      Bay Area, CA
      Posts
      250
      Vehicles
      Old Ford Truck
      03-31-2012 07:17 PM #7
      A-10's are like that also

      Quote Originally Posted by Elbows View Post
      You should instead be praising the fact that life is so good, and safe that you can be afforded the luxury to be outraged by the death of one civilian, at the other end of the world. That's phenomenal.
      Quote Originally Posted by Jim Harbaugh
      Who's got it better then us?!? ...... Nooooo-body!!!

    8. Member B3sat16v's Avatar
      Join Date
      Jan 23rd, 2002
      Location
      Around the world
      Posts
      7,403
      Vehicles
      MH-60R
      03-31-2012 07:21 PM #8
      Quote Originally Posted by Gern_Blanston View Post
      Here's what the original DC-9 manual says:
      "The nacelle axis and pylon have been set at 3 degrees angle of attack relative to the fuselage to align them with the local flow conditions prevalent at cruising conditions. This is necessary to eliminate the interference and high induced drag that they would otherwise be subjected to. The nozzle is then canted upward relative to the engine axis, thus eliminating the pitching effects due to thrust.
      The air coming of the back of the wing is headed down just a bit after following the camber of the top surface.
      After reading that, I went and looked and some pics and damn the nozzle is canted quite a bit upwards in the DC/MD aircrafts, but the above one from the 727 it is not canted at much upwards.

    9. 03-31-2012 09:00 PM #9
      Quote Originally Posted by B3sat16v View Post
      After reading that, I went and looked and some pics and damn the nozzle is canted quite a bit upwards in the DC/MD aircrafts, but the above one from the 727 it is not canted at much upwards.
      The quiet kits that are installed make it look like they are at a less severe angle than 3 degrees.
      Plus the angle of the picture makes it seem weird too.
      But the pitch of the engine in relation to the rest of the fuse can be noticed.
      This post was monitored and approved by the NSA

    10. Member B3sat16v's Avatar
      Join Date
      Jan 23rd, 2002
      Location
      Around the world
      Posts
      7,403
      Vehicles
      MH-60R
      03-31-2012 09:29 PM #10
      Quote Originally Posted by dubraycer36 View Post
      The quiet kits that are installed make it look like they are at a less severe angle than 3 degrees.
      Plus the angle of the picture makes it seem weird too.
      But the pitch of the engine in relation to the rest of the fuse can be noticed.
      We are talking about the Nozzles right? Because the engines are tilted, and what Gern posted talks about the Nozzle being canted upward to maintain the thrust at linear as possible to avoid a moment causing a nose down attitude.

      Let me maker sure I explain. The Inlet (Diffuser) is canted upwards to take advantage of a more straight flow due to the downward flow coming from the top of the wing. The nozzle is also canted upwards to cancel any angle with relation to the longitudinal axis of the aircraft, thus providing a thrust vector that wont cause any moments. This can be seen very well on the DC/MD pictures, but I know for a fact that the IL-62 does not do this (Also seen in photos), as well as the VC-10 and if you look at the 727, the upward canted nozzles still have to angled thrust (Downward).
      Last edited by B3sat16v; 03-31-2012 at 09:31 PM.

    11. Senior Member .LSinLV.'s Avatar
      Join Date
      Nov 13th, 2009
      Location
      Vegas Bitches!
      Posts
      29,009
      Vehicles
      00' VR6T 12' V6 TDI 72' 914-6
      04-03-2012 09:32 PM #11
      thanks guys! I appreciate all of the help/input.
      Larry

      Demokratikally Elekted Minister of Shekels of the Independent People's Republik of Offtopikstan

    12. 04-04-2012 09:10 AM #12
      Quote Originally Posted by Gern_Blanston View Post
      Here's what the original DC-9 manual says:
      "The nacelle axis and pylon have been set at 3 degrees angle of attack relative to the fuselage to align them with the local flow conditions prevalent at cruising conditions. This is necessary to eliminate the interference and high induced drag that they would otherwise be subjected to. The nozzle is then canted upward relative to the engine axis, thus eliminating the pitching effects due to thrust.
      The air coming of the back of the wing is headed down just a bit after following the camber of the top surface.
      This image is somewhat exaggerated, but gives a good idea of the effect they're talking about:


    13. Geriatric Member ATL_Av8r's Avatar
      Join Date
      Oct 17th, 2002
      Location
      Gapiana
      Posts
      40,464
      04-04-2012 09:20 AM #13
      Come on Larry, you've been in the MKIV forum. it's all about the reverse rake
      MemeGate 2012 - First Responder, post #2

      Quote Originally Posted by .skully.
      Mike, quote me in your signature

    14. Senior Member .LSinLV.'s Avatar
      Join Date
      Nov 13th, 2009
      Location
      Vegas Bitches!
      Posts
      29,009
      Vehicles
      00' VR6T 12' V6 TDI 72' 914-6
      04-18-2012 06:51 PM #14
      Quote Originally Posted by ATL_Av8r View Post
      Come on Larry, you've been in the MKIV forum. it's all about the reverse rake


      so is that why 757's have such a sharply angled cockpit/front of the fusealge??
      Larry

      Demokratikally Elekted Minister of Shekels of the Independent People's Republik of Offtopikstan

    Posting Permissions

    • You may not post new threads
    • You may not post replies
    • You may not post attachments
    • You may not edit your posts
    •