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Overhead Console for the RAF

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  • #16
    Re: Overhead Console for the RAF

    The second problem is that any time the gyroplane is flying with the RTV forward of the gyro CG, it's like a fixed wing flying with the CG behind the center of lift. *The reason this is an unstable condition is because the aircraft reactions to G forces are opposite from what you want them to be. *<br><br>Example: *The gyroplane is flying straight and level. *It flies into a strong thermal. *The thermal is pushing the rotor up, creating more lift, which means a greater than 1 G situation. *In a situation like this, you want the gyro to pitch down into the updraft, in order to return to a 1 G flight. *Every stable aircraft does that hands off. *In an RAF, since the RTV is forward of the CG, a high G situation is causing a nose up pitching moment (the rotor is pulling the nose up and the weight of the gyro is pulling down). *The nose is pitching up, which causes the rotor to pitch up, and there's even a higher G situation. *This is an unstable condition that feeds upon itself. *It requires a pilot intervention or the machine will get out of control.<br><br>The above explanation is why the RAF is statically unstable. *What makes this situation even worse, it that the RAF is also dynamically unstable. *I don't want to go into dynamic stability, but I will just say that the reason the RAF is dynamically unstable is because it has no horizontal stabilizer. *Being dynamically unstable makes the RAF very susceptible to porpoising, which I assume you've heard about. *Briefly, it means that, unless the pilot is well tuned to the gyro rate of pitch and control response timing, pilot corrections may cause the gyro to overshoot back and forth until it self destructs.<br><br>This is where Larry's (or any other) stab is coming into the picture. *Larry's stab has two functions. *The first function is to create a nose-up moment to counter the engine nose down moment. * If the stab were 100% effective, it would completely cancel out the engine nose down moment, and provide just a little more nose up moment. *This would prevent a bunt over when the rotors are unloaded, and it would also move the RTV closer, and preferably, behind, the gyro CG and the gyro will become stable.<br><br>The second function of the stab is to provide dynamic stability. *Larry's stab, due to the vertical winglets, is also providing some additional yaw stability.<br><br>Larry may disagree with me on this one, but I don't think any stab, including Larry's, can offset the huge engine thrust offset moment that is inherent to RAF. *There is no doubt that Larry's stab is making the RAF much safer to fly but I don't believe that it accounts for more than a band-aid. *You can search the threads on the other forum for calculation that Doug Riley made for how much down lift is required in order to cancel out the RAF engine pitching moment. *His numbers show that even if you placed the stab inside the prop wash, you would still need a huge stab to generate the required moment. *<br><br>This is why Jim Mayfield at AAI has decided to really solve this problem by making the RAF a true centerline-thrust machine. *Actually, Maxie Wildes has done that before with his famous &quot;easter egg&quot;, but Jim has optimized this design with his engineers. *A large stab may be used to balance the moments in a gyro in which the engine thrust offset is not too great. *In the RAF the offset is so great that the only practical way to make it truly stable is to move the engine down.<br><br>Bob, this is a long answer for a short question, but, as I said at the top of this thread, I am sick of seeing people getting killed in their RAFs. *I think the RAF manufacturer is criminal, and I hope they go out of business very soon. *I am very worried for all the un-suspecting RAF pilots who are not aware of the death traps they are flying. *Just two weeks ago, as you know, an un-suspecting ATP-rated airline pilot plummeted to his death in his brand new RAF (which had a stab, I don’t know who’s).<br><br>Udi-

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    • #17
      Re: Overhead Console for the RAF

      Udi, the Raf keel is 4&quot; X 2&quot; with 1/8&quot; wall thickness. It is very strong compared to what is normally used for keels.<br><br>Aussie Paul.

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      • #18
        Re: Overhead Console for the RAF

        Udi, you are so right about the &quot;bandaid fix&quot;.<br><br>Even if the stab was effective enough to compensate for the Raf 10&quot; thrust offset it would be of no use at all in a zero or almost zero airspeed unloading of the rotors with lots of power.<br><br>Having the Stabs on my Raf was a much needed improvement but having CLTon Hybrid was a much larger improvement and then having stabs as well as CLT made it the most pitch stable machine that I have flown.<br><br>Aussie Paul.

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        • #19
          Re: Overhead Console for the RAF

          &quot;A pitch stable aircraft is one that tends to return to its previous trim condition after being upset (push your plane's stick and let go; it will oscillate a little and then return to trimmed flight)&quot;. *<br><br>That was a perfect description of what a RAF does with the Ultimate stab. *Except it doesn't &quot;tend to return&quot;, it returns.<br>One customer actually complained in a joking way because *every time (before stab) he would fly by his mom's house he would make a few circles to get her attention. *Now he has to manually hold the circle. *When he takes pressure off the stick, his RAF straightens up to it's trimmed position.<br><br>Here's that picture I was trying to get to work and I messed around with the profile thing and got it to work. *Just requires keyboard time. *<br><br>P.S. removed the N-Number because I haven't gotten an answer from the owner yet. *Some people don't check e-mail very often. *Larry
          Larry Martin, stab sales, www.gyrostabs.com

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          • #20
            Re: Overhead Console for the RAF

            <br><br>Having the Stabs on my Raf was a much needed improvement but having CLTon Hybrid was a much larger improvement <br>
            <br><br>Paul, and guys -- <br><br>That is exactly what the studies at University of Glasgow concluded -- the single best thing you can do for pitch stability is to get the thrustline to run through the centre of mass. <br><br>The next best thing is to have sufficient horizontal stab (area, arm, and interaction with the rotor wash are all factors) to provide real-world pitch damping. <br><br>And having the two together can prevent or delay pitch excursions (depending on the cause of said excursions). <br><br>Glasgow had an instrumented gyro where they could move the motor up and down on the mast between flights. Lots of very good experiments went on there. It all started with a CAA grant to study why a certain brand of gyro ras reverting to kit form inflight due to PPO. (Not what you think -- Fetters-era Air Command). If you remember, Air Command hit hard with (1) complete kits, (2) effective marketing(=many sales), (3) the Rotax motor (=more thrust than Macs or VWs), and (4) longer props (=higher thrustlines). <br><br>Unintended consequences.<br><br>Air Command wound up banned in Britain (although I think the CLT machines are permitted again. Current Air Commands are a good and safe design). <br><br>Anyway, that other vendor of high thrustline machinery (the one that says a stab is a hazard), their rep told me that there had been no academic research on Gyro stability and control since NACA. Do they really believe that? They must. They couldn't sell their machines unless they believed them to be safe. <br><br>cheers<br><br>-=K=-
            Kevin 'Hognose' O'Brien, PRA 40016 (L), EAA 785699 (L), SOA 2333-GL
            Pontificating for 1,000 posts and counting

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            • #21
              Re: Overhead Console for the RAF

              &nbsp;But, Scooter/Larry ...........says<br> &nbsp;Here's that picture I was trying to get to work and I messed around with the profile thing and got it to work. &nbsp;Just requires keyboard time. &nbsp;<br> <br>P.S. removed the N-Number because I haven't gotten an answer from the owner yet. &nbsp;Some people don't check e-mail very often. &nbsp;Larry<br><br> ******** &nbsp;I DID answer you, both in this Instant messaging here and to your Private e-mail.<br>Just send Royalties check to the photographer.......Me!<br>Dennis<br> ::)
              Dennis

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              • #22
                Re: Overhead Console for the RAF

                I don't have or use instant messaging and nothing has ever appeared in my pm from a Dennis unless it was spam. *And, Dennis who? &nbsp;Never sold a stab to a Dennis that I remember. &nbsp;Sorry no check.<br><br>Anyone sending me e-mail, whatever the method, best be very specific in the subject area or they go to the automatic delete folder in la-la land.
                Larry Martin, stab sales, www.gyrostabs.com

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                • #23
                  Re: Overhead Console for the RAF

                  Quote:<br>-----------------------------------------------------------------------<br><br>You can build an extremely safe machine.... and still have it look sharp.<br><br>-----------------------------------------------------------------------<br><br>How true.... Thats why im going to build a two place Little Wing with a Radial engine.<br><br>I just may finally decide to start offering gyro training....maybe the time has come for me to do it.<br><br>However something new just just came up that may delay me for another year before I am ready to actually start a school.<br><br>At least I have ordered the plans so I am now committed to the project.<br><br>Chuck E.
                  The hardest thing about flying is knowing when to say no.

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                  • #24
                    Whats with all the *<br><br> &nbsp ???still think the new site is poor
                    I thought I had put it in the profile, guess not. *It is now. *<br><br>The guy is concerned about safety. &nbsp;He bought the &nbsp;Ultimate stab before his RAF kit even arrived. &nbsp;Plus he he going to train with Menzie. &nbsp; Safety is certainly the most important, but some people appreciate beauty/craftsmanship also.<br><br>Larry Martin

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                    • #25
                      the stab that larry martin designed is the one being sold as the ultimate stab by larry boyer.

                      This one piece has saved more RAF lifes that any thing else.
                      Best Regards,
                      Eddie Sigman,Polvadera,nm
                      (575) 835-4921

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                      • #26
                        Never did see the overhead console picture which is the subject of this thread!
                        CFI-ASMEL-IA, A&P
                        @ 6450' MSL in W. Colo.

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                        • #27
                          I have pics of Larry Martin's creations somewhere. I first saw them at the PRA convention when it was held in Waxahachi, TX.

                          What year was that ?

                          He was making the Bad Stab, overhead console & external fuel tanks that allowed you to fit racing bucket seats. RAF was also there with their machine & demo rides given. I got a ride with Dolfin in a yellow RAF.

                          That is also where I had my first & only ride in a Magni with 914. Show price from Gregg G. was $35,000 back then !
                          Happy Flying, Chris S.

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                          • #28
                            You should have bought it, eh? Still have the pictures?
                            CFI-ASMEL-IA, A&P
                            @ 6450' MSL in W. Colo.

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