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  • #16
    Originally posted by mmrassi
    Hi,
    I would like to know how the propeller torque is controled in a multi-engine prop plane?

    Do the engines rotate in different directions? ( I don't think so)

    Regards
    Please keep in on topic guys, the poster is asking about multi engine types.

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    • #17
      On most conventional twins both engines turn the same direction producing torque opposite the direction of rotation (clockwise when viewed from behind in the USA).
      The engine mounts transmit the thrust and torque loads to the wing and airframe. In flight torque tends to cause the airplane roll to the left. The roll tendency is removed during cruise by (depending on the aircraft) tweaking aileron trim, drooping a left hand flap, adjusting an eccentric cam on the wing trailing edge (increases or decreases lift on one wing).

      If your are referring to an engine out condition, torque is not the major issue, yaw caused by asymmetrical thrust is corrected using the rudder.

      "P" factor (the tendency for the descending propeller blade to produce more thrust than the ascending blade, causing a yaw to the left) is controlled using rudder trim or by off setting the vertical fin slightly.
      Don
      Standard practice for managers around the world:
      Ready - Fire - Aim! DAMN! Missed again!

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      • #18
        [QUOTE=Dmmoore]adjusting an eccentric cam on the wing trailing edge (increases or decreases lift on one wing).[QUOTE]

        thanks Dmmoore!

        but could you please explain more about the term I quoted?! My english is poor to realize that! SORRY!!!

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        • #19
          [QUOTE=mmrassi][QUOTE=Dmmoore]adjusting an eccentric cam on the wing trailing edge (increases or decreases lift on one wing).

          thanks Dmmoore!

          but could you please explain more about the term I quoted?! My english is poor to realize that! SORRY!!!
          I will be happy to explain.
          First, you have no reason to apologize for your English skills. It seems to be more than adequate. I will admit your English is much better than my abilities in any language other than English.

          On high wing Cessna aircraft, the lateral trim is adjusted using an eccentric cam on the bolt attaching the rear spar to the fuselage. The eccentric cam is a bushing with a hole drilled off center. Rotating the cam causes the Trailing Edge to move up or down. Moving the TE down increases the lift on that wing. During test flights the eccentrics are adjusted to allow the aircraft to fly with wings level during cruise flight.
          Don
          Standard practice for managers around the world:
          Ready - Fire - Aim! DAMN! Missed again!

          Comment


          • #20
            Originally posted by Dmmoore
            On most conventional twins both engines turn the same direction producing torque opposite the direction of rotation (clockwise when viewed from behind in the USA).
            The engine mounts transmit the thrust and torque loads to the wing and airframe. In flight torque tends to cause the airplane roll to the left. The roll tendency is removed during cruise by (depending on the aircraft) tweaking aileron trim, drooping a left hand flap, adjusting an eccentric cam on the wing trailing edge (increases or decreases lift on one wing).

            If your are referring to an engine out condition, torque is not the major issue, yaw caused by asymmetrical thrust is corrected using the rudder.

            "P" factor (the tendency for the descending propeller blade to produce more thrust than the ascending blade, causing a yaw to the left) is controlled using rudder trim or by off setting the vertical fin slightly.
            Very god post Don! (except you keep omiting the effect of the slipstream rotation on the rudder, which when the fin(s) are washed by prop(s) wash it is a yaw factor greater than P-factor)

            I thought I'd comment the Piper Tomahawk and the Cessna 152 I used to fly had what I think was called "fleetners", or something like that. It was like a small "ground-adjustable trim tab", made of a small piece of aluminium sheet that protuded from the trailing edge and that was slightly bent one way or the other as needed to keep a hands-off coordinated stright and level cruise.

            There was one fleetner on the rudder and one on one of the ailerons.

            These fleetners were first adjusted in factory during the test flights of the individual airplanes, but the POH included a procedure to adjust them by the owner.

            It was a complex and highly technical procedure. Something like "press the fleetner with your hands between two flat piced of wood and bend".

            I don't know of any twin that has such a "system" though. (not that I know a lot about a lot of twins anyway)

            --- 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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            • #21
              The only thing I have ever heard those things called are "ground adjustable trim tabs".

              We are dealing with twins. I don't know of a twin that isn't equipped with cockpit adjustable trim tabs which render the a ground adjustable tabs unnecessary.

              As far as I know the question was not limited to propeller driven aircraft. Jets don't expel twisting air.
              Don
              Standard practice for managers around the world:
              Ready - Fire - Aim! DAMN! Missed again!

              Comment


              • #22
                Originally posted by Dmmoore
                As far as I know the question was not limited to propeller driven aircraft. Jets don't expel twisting air.
                Neither they are subject to P-factor or torque AFAIK

                --- 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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                • #23
                  Except for turboprops.

                  Have heard of couter-rotating twins like the Seminole and Navajo CR, but not a turboprop that counter rotates. But thats without the assist of Google/Wikipedia and of course the authoratative source for Aviation Information, YouTube Comments.

                  By the way not having a critical engine doesnt mean a twin wont be nasty if one goes out... sometimes for reasons unknown to inexperienced or blase pilots, as in MU-2.
                  ASMEL-IA 1978 A&P-IA 1965 First Aloft 1954 DC-4
                  Dad: B-24 Ploesti Self: U205A1 private ops Nam

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                  • #24
                    Originally posted by Dmmoore
                    Gabriel,
                    [Flyboy mode] You could have simply stated:
                    Torque causes the aircraft to roll.
                    "P" factor cause the aircraft to yaw.
                    If any one requested an explanation, go into detail[/Flyboy mode]
                    Giving Gabe some crap for being "long winded" is not flyboymode...heck we've all done it!

                    Flyboy is more like, "Oh thank you you worthless, expelitive, holiness Donald-the-wrench, but I can fend for my self, Gabe you are so expelitve worthless, have you ever flown a CRJ?"

                    And to all, I could be wrong, but I think our original poster was referring to "engine power", which is somewhat related to engine torque.

                    And that is controlled by these levers in the cockpit that through any number of mechanisms, control fuel flow (and perhaps airflow in the case of "gasoline") to the engines.
                    Last edited by Dmmoore; 2008-07-24, 15:30.
                    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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                    • #25
                      Pehaps for the unitiated like me this might help a little.

                      [photoid=5745166]


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                      • #26
                        Originally posted by 3WE
                        And to all, I could be wrong, but I think our original poster was referring to "engine power", which is somewhat related to engine torque.
                        That's the feeling I got also. I'm not sure if he is wanting to know if there are separate torque levers or what, though.

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                        • #27
                          Originally posted by cja
                          Pehaps for the unitiated like me this might help a little.

                          [photoid=5745166]
                          That would be a counter-rotating turboprop.

                          Turbofans are subject to P-factor as well. I thought I was pretty much done adjusting rudder trim continuously when I stopped flying the Dash. The X is a bit of a rudder trim hog as well courtesy of the large fans.
                          Bite me Airways.....

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