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"Arerodynamics of Gyroplanes"

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  • Chopper Reid
    started a topic "Arerodynamics of Gyroplanes"

    "Arerodynamics of Gyroplanes"

    Are any of you familair or know anything of this extensive 356 page study released by the UK CAA. Its a joint research between the University of Glasgow and the UK CAA. The good Professor "Houston" man behind the report.

    I would be interested in those who know anything about Professor Houston and this 'extensive' report. If its already been discussed here then please forgive me for missing it.

  • Chopper Reid
    replied
    Originally posted by Graeme Monro View Post
    I had to have a couple just to help cool my brain down ( I think I broke it), and it is all Brian's fault.

    Graeme.
    I'm soo sorry.

    Leave a comment:


  • Jean Claude
    replied
    Thank you Chuck. With Google I can understand simple sentences. When they are more complicated, so I'm not always sure that the translation is your thoughts.

    Leave a comment:


  • C. Beaty
    replied
    JC, your English is much superior to my machine translations of French to English.

    When I use Google or Yahoo for translation: French in = gibberish out (Google says gibberish = charabia).

    I expect the reverse is also true.
    Last edited by C. Beaty; 10-24-2010, 03:44 AM.

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  • Resasi
    replied
    Now I feel bad for obviously introducing someone who had it all ass-backwards.

    I'm off for a beer.

    Leave a comment:


  • Jean Claude
    replied
    Originally posted by kolibri282 View Post
    Your sketches easily bridge any gap in comprehension that might occure due to the fact that we communicate via a lingua franca.
    Thank you, Juergen. My morale goes up and I feel better!
    Jean Claude

    Leave a comment:


  • Graeme Monro
    replied
    Another beer.

    Originally posted by bones View Post
    Damn i just wish i could get my head around half of this stuff, need another beer me thinks :)
    I had to have a couple just to help cool my brain down ( I think I broke it), and it is all Brian's fault.

    Graeme.

    Leave a comment:


  • kolibri282
    replied
    JC->My English is so bad?
    Your sketches easily bridge any gap in comprehension that might occure due to the fact that we communicate via a lingua franca.
    Thanks for your insisting on clarifying the matter!
    Last edited by kolibri282; 10-23-2010, 09:08 PM.

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  • bones
    replied
    Damn i just wish i could get my head around half of this stuff, need another beer me thinks :)

    Leave a comment:


  • Jean Claude
    replied
    He was able to convince you with sketches false, and I could not convince you with sketches correct. Boo ... It's not fair ... My English is so bad ?
    Jean Claude
    Last edited by Jean Claude; 10-23-2010, 03:36 PM.

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  • kolibri282
    replied
    Most modern day trainee gyro pilots have experienced the brutality of the forces developed when they mess up their rotor starting and their little 22 foot (6.7 m) rotor decides to start flapping.
    To me this sentence seems to state very clearly that the author sees flapping as the source of the rotor force component which the pilot has to control (or may no longer be able to control) or do I get the meaning of the sentence wrong?

    He uses the term "Drag" for the force component in the negative x direction which is consistent with using lift for the upward component. If you carefully study the drawing you see that this "Drag" force is almost as large as the lift force and the resultant is not aligned with the axis of rotation but inclined backwards. So his "Drag" force includes the component of rotor flapping. I feel that the confusion comes from the fact that in rotor work "Drag" is not the inplane force component that is perpendicular to thrust but sums up all force contributions along the x axis. That inplane component of a rotor wich lays in the tip path plane is called H-force therefore the L/D ratio of the rotor alone is thrust devided by H-force (thrust/H-force).

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  • C. Beaty
    replied
    Mr. Lovegrove also states that rotor drag increases with airspeed. That’s also backwards.

    Cyclic flapping angle increases with airspeed.

    So we now have a rotor-head and the machine which dangles from it, in beautiful balance. it will happily fly 'hands off' in that situation. If we want to fly faster and still 'hands off', the rotor drag may increase, so we will have too much effort trying to pull the torque-beam into the 'climb' mode. But, Hey , presto! we simply relax the tension on the trim spring with our inflight pitch trimmer, and its contribution to the rearward moment is reduced and the head system comes nicely back into balance.
    Last edited by C. Beaty; 10-23-2010, 07:41 AM.

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  • Jean Claude
    replied
    Juergen, I agree with you: difference on value is negligible. But difference on the lever arm is basic, as shown in my sketch post #24
    A good engineering practice is certainly having an understanding of basic phenomena and, better yet, secondary phenomena. Chuck thinks like me : "Rotor lift/drag ratio has nothing to do with it", contrary to the reasoning of Peter Lovegrave and yours.
    Last edited by Jean Claude; 10-23-2010, 07:04 AM.

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  • kolibri282
    replied
    JC->The thrust or the lift? is not the same thing. Difference 10 is not negligible.
    The cosine of 10 is 0.9848 the difference between lift and thrust is therefore 1.5%, that is why the so called small angle assumptions are almost invariably used in rotorwork since the errors in calculating the forces are usually much larger unless you use a numerical rotor model that takes into account a plethora of variables.

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  • Jean Claude
    replied
    Originally posted by kolibri282 View Post
    I didn't forget lift, I just set the lever arm to zero since it is very small anyway
    No very small. About 1/5 lever arm to Drag

    Originally posted by kolibri282 View Post
    the thrust would counteract the moment generated by the drag force .
    The thrust or the lift? is not the same thing. Difference 10 is not negligible.

    Originally posted by kolibri282 View Post
    so you err to the safe side.
    I did not say not to shift the axis of bearing. I said that the cause is not the ratio Lift / Drag. The real cause is the flapping angle, which can reach 8 degrees in certain flight conditions. The safety offset is therefore that indicated by Lovegrove, but for an entirely different reason.

    Jean Claude

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