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  • #16
    Originally posted by Gabriel View Post
    I don't know or care. I don't look at number of posts
    I have always wanted to ask him about that!

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    • #17
      Originally posted by Evan View Post
      The 737-Max struggles to handle 69" fans. They must be mounted forward of the wing in a configuration that compromises stability at the edge of the envelope.
      Is that the case? This is one thing that never was clear throughout all this MCAS debacle.

      Engines under the wing cause a nose-up pitching moment when thrust is applied.
      Thrust creates a perpendicular force when flown at an angle of attack, which works just like lift (this is because when the engine is not aligned with the airflow it not only accelerates the air but it also deflects it. And just like lift, when it is back of the CG it is stabilizing and when it is ahead it is distabilizing. That by itself doesn't make a plane unstable. (The main wing of almost every plane is distabilizing, that's why there is a "stabilizer" at the back).

      These 2 "nose-up under thrust" effects are true of all modern underslung twin engine jets. While the Max has the engines more forward that others, others have the engines further down.

      Boeing states that the MCAS is there to provide a similar feel than the NG.
      The EASE in their MAX re-certification asserted that the MAX is stable and controllable in all its envelope even with the MCAS off.

      At this point, since pilots will need to go through a more extensive training anyway including simulator time, I wonder if, in hindsight, it wouldn't have been better not to have a MCAS at all and just train the pilots for the effects of high thrust at low speed and high angles of attack so they familiarizare with the extra push down required (compared with the NG) and are not caught by surprise (that, assuming that the plane was certifiable without MCAS). Now they have to undergo training regarding the MCAS, their failure modes, and how to fly MCAS on and MCAS off.

      --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
      --- Defend what you say with arguments, not by imposing your credentials ---

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      • #18
        Originally posted by BoeingBobby View Post

        Where did you come up with this B S.?
        The C-5 originally had GE TF-39 engines. All left flying have now been converted to GE CF6-80's
        Yes. In production they carried the TF-39 (military version of the CF-6), but the initial design was formed around the JT9D.

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        • #19
          Originally posted by Gabriel View Post

          Is that the case? This is one thing that never was clear throughout all this MCAS debacle.
          It still isn't really clear. The way I understood it, the nacelle tucked high up in front of the wing creates aerodynamic lift in a way that, at high AoA, increases the pitch rate, so when flying in that regime (due to an upset or brain damage) it might unexpectedly 'pull up' into a stall. So, an added danger for unusual attitude recovery. You could argue that pilots just need to be retrained to know this but I would counter that you don't want to count on pilots who get there in the first place.

          That's how I understood it.

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          • #20
            Originally posted by Evan View Post

            Yes. In production they carried the TF-39 (military version of the CF-6), but the initial design was formed around the JT9D.
            Show your data please. According to the 3 dozen ex C-5 guys I know, you are wrong.

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            • #21
              Originally posted by Evan View Post

              Yes. In production they carried the TF-39 (military version of the CF-6), but the initial design was formed around the JT9D.
              More specifically, the JT9D came from a development contract issued for the C5, but the contract eventually went to GE and the TF39.

              The point is that the high-bypass revolution started with the C5 and begot the 747 and everything turbofan-powered thereafter. The 737 airframe precedes this revolution.

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              • #22
                Originally posted by Evan View Post

                More specifically, the JT9D came from a development contract issued for the C5, but the contract eventually went to GE and the TF39.

                The point is that the high-bypass revolution started with the C5 and begot the 747 and everything turbofan-powered thereafter. The 737 airframe precedes this revolution.
                You are quoting crap from AVGEEKS! Guess you think the election was rigged too!

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                • #23
                  http://all-aero.com/index.php/contac...t-whitney-f105

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                  • #24
                    All Aero.com. Another real aviation information site. Find me something from Pratt and Whitney's site.

                    Comment


                    • #25
                      Originally posted by BoeingBobby View Post

                      All Aero.com. Another real aviation information site. Find me something from Pratt and Whitney's site.
                      I'd love to but, alas, they are more interested in selling their current products than wallowing in historical bric a brac.

                      But the story goes like this: The 747 is essentially a USAF transport aircraft initiative repurposed as a passenger jet.


                      - In 1963 the USAF commissioned design studies for a jumbo jet transport designated CX-HLS. The military-industrial complex leaped into action.

                      - Both Pratt & Whitney and GE had high-bypass turbofans on the drawing board. The commission enabled them to fast track these designs.

                      - Meanwhile, Boeing, Douglas and Lockheed had favorable airframe designs which they presented.

                      - P&W proposed the JT9D. GE proposed the TF39.

                      - Boeing's proposal utilized the JT9D. Lockheed's utilized the GE TF39.

                      - The commission selected Lockheed and GE to build what would become the C5 Galaxy.

                      - Boeing then opted to redevelop their proposed transport into a jumbo commercial passenger / cargo aircraft, designated the 747.

                      - Boeing chose the JT9D, rejected for the C5, to power the 747.

                      - The 747 became a clean-sheet airframe design, but the JT9D was carried over from the CX-HLS (C5) development stage.

                      - The high-bypass engine technology developed for the C5 made the 747 possible, and other widebody airframes that followed.

                      - Behold: https://www.google.com/search?q=Boei...=1920&bih=1071


                      And that is the point I'm making. It seems to evade you. Both the JT9D and the TF39 (CF6) were originally developed for the C5.

                      The 737 is precisely problematic today because it was developed for a preceding turbojet era that became obsolete by the 1970's.

                      Yet somehow, it's still around.

                      And it is still around precisely because the greed and cynicism of short-term shareholder value over progress innovation and long-term value, which should have become obsolete in 1929, is somehow still around.

                      You can bandage the broken parts of the 737-Max and make it fly again, but you can't bandage that toxic culture. It has to go the way of the turbojet if Boeing wants to survive.


                      Comment


                      • #26
                        "But the story goes like this: The 747 is essentially a USAF transport aircraft initiative repurposed as a passenger jet."

                        I spent the last 20 years of my 47 in aviation flying every model of the 74 built except the SP, and the modified NASA bird that carried the Space Shuttle. You are going to tell me about the aircraft? You aren't even close on this one young man!

                        You might want to read up on Juan Trippe!

                        Comment


                        • #27
                          Originally posted by BoeingBobby View Post
                          "But the story goes like this: The 747 is essentially a USAF transport aircraft initiative repurposed as a passenger jet."

                          I spent the last 20 years of my 47 in aviation flying every model of the 74 built except the SP, and the modified NASA bird that carried the Space Shuttle. You are going to tell me about the aircraft? You aren't even close on this one young man!

                          You might want to read up on Juan Trippe!
                          Yes, as I said, the 747 became a clean-sheet design with a great deal of input from PanAm. You seem to be entirely confusing the point. The developments set in motion by the CX-HLS resulted in the 747. They made it possible. Industry cannot invest massive sums of money for technology that has no useful purpose. In the early 1960's. there was no useful purpose for a large, turbofan engine. The USAF commission provided that purpose.

                          This was an unprecedented age of optimism and imagination and Boeing expected supersonic transport to replace the 747 as a passenger jet in the 1970's. Therefore great design emphasis was placed on the 747's ability to perform as a transsonic cargo jet in a supersonic age. The design considerations first employed on the CX-HLS, most notably the raised cockpit and hinged nose section for straight-in container loading dictated the 747 design.

                          But I'm sure you knew all that.

                          Comment


                          • #28
                            Ok back to the 737 and it's MCAS.

                            After 14 years flying the DC-8 and 747 I went to a new employer to fly the Hawker 1000. One of the first things you do in the sim was stall recoveries. Prior to this it was, max power and pitch down. Well guess what happened to me in the sim with that old response, woooo!!

                            Back in the day, I'm sure some of you also experienced this, I was taught the recovery for a runaway nose up trim or miss trimmed, nose up, recovery was to roll off on a wing. This roll off on the wing can also be accomplished with the rudders but only us old guys would try that.

                            Comment


                            • #29
                              Originally posted by Gabriel View Post
                              I think that, in general, people in this forum knows better.

                              I will take Evan as an example, he was relentless cristianizan Boeing, their MCAS design (or that they upgraded the 737 again at all instead of doing a clean-sheet modern design), their business approach, strategy and culture, not to mention their top leadership for whom he wished jail time.

                              However, even he recognizes the scrutiny that this plane has gone through during the last 2 years, that the technical problems are solved, that the manuals and training issue has been resolved, and that the plane will be (and is now) as safe as any.

                              I do not think that many people in this forum is in the "MAX no-fly" team.

                              That said, I think that many of us still think that Boeing did not do a real deep transformation of its culture and leadership as it was needed. It is not clear at this point that they moved the focus back to great engineering and real innovation even if it means looking a bit away of the short-sighted view of the Wall Street bull.

                              So we can be happy with the MAX going back to operation, willing to take a MAX flight any day, and still unhappy with Boeing.
                              Why do you think the culture hasn't changed? They have overhauled their executive team. The old guard is gone. Is there evidence the new crew is not safety minded?

                              Comment


                              • #30
                                Originally posted by Schwartz View Post
                                Why do you think the culture hasn't changed? They have overhauled their executive team. The old guard is gone. Is there evidence the new crew is not safety minded?
                                Yes. They remain committed to previous practices. They are still bean counters and managers for the shareholders. They did changes and improvements but because they had no choice, not because of conviction and culture.

                                --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                                --- Defend what you say with arguments, not by imposing your credentials ---

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