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Dubai - WAG - Gyro down 9.12.15

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  • The angle of attack stability of the Magni results from the over balanced (nose heavy) rotor blades. An upward gust causes the rotor to pitch in a nose down direction, keeping the machine headed into the relative wind.

    The downside of an over balanced rotor is a heavy stick.


    • yes ... the trim cable needs not to break ...


      • Good old British poet John Donne wrote that no man is an island. Donne died 200 years before the theory of natural selection, but he was correct as a practical matter.

        When poorly-designed machines, and pilots with bad judgment, cause fatal gyro crashes, the rest of us get punished. I wish I had a dollar for every time I showed up at an airport with a gyro, only to be kicked out for "safety" reasons, or to receive a torrent of abuse about "them things killed three of my friends...."

        An FAA inspector told me, with a straight face, that the pilot of a tilt-spindle gyro "really has no control." I guess he didn't realize that a rotorhead employing a tilting spindle with flap hinges is the EXACT mechanical equivalent of a swashplate cyclic.

        Our reputation hurts all of us.

        Awhile ago, we tried to get the FAA to allow factory-built Light Sport Aircraft. The FAA refused. The basis for their denial (I am paraphrasing here) was that the gyro community didn't have its s**t together regarding stability and design standards.

        It's interesting that the Magni derives from Jukka Tervamaki's ATE-3 and ATE-5. Jukka is a real engineer. In fact, he's the first person that I can recall writing up a narrative of PPO, around 1973-4, in a letter to the PRA magazine. He prescribed a large H-stab as the solution to what he called the "residual moment about the autogyro CG" during low-G maneuvers. He was speaking of pitching moments, but rolling moments can be just as deadly.

        The FAA was only partly correct about us. There are plenty of people in our community who do understand airframe stability. The knowledge isn't universal, though, and so we still have $100,000 "sophisticated" gyro designs with various "residual moments about the CG." These can kill even pilots who don't make stupid mistakes. But it's all avoidable.


        • In addition to torque roll elimination via tailplane differential, Cierva eliminated throttle-yaw coupling by carefully balancing dorsal fin area vs belly fin area.

          I well remember the rudder pedal toe dance during takeoffs and landings in my Bensen B-8. A Dominator tall tail accomplishes the same thing as Cierva’s dorsal-belly fin balance.
          Click image for larger version  Name:	cierva_c-30.jpg Views:	1 Size:	65.5 KB ID:	1141399


          • In my experience with both 1- and 2-place Dominators, Chuck, you're right. There' s not much rudder work to do in these gyros, except for intentional slips and twirls.

            Some ultralight gyros, notably the Gyrobee, have smaller vertical fin areas than the Bensen (the 'Bee had 4 or so sq. ft. instead of Bensen's six). I used to get leg cramps mashing my 'Bee's left pedal against the stop doing 18 mph takeoffs. Things got more reasonable as you picked up airspeed.

            Dr. Bensen was exquisitely calibrated as to what informalities he could get away with in a small, light, low-powered gyro (his original engine was the 40 hp. direct-drive Nelson). The list of shortcuts includes minimal accommodation of 2/rev mast shake, no pre-coning angle in the metal blades, no roll-torque compensation (well, if the side-mounted gas tank was empty), torque-yaw effect, the infamous scrub brake, rigid axle, and on and on. These little shortcuts have not worked out as well in heavier/enclosed gyros, hence some of the problems we're talking about.

            Interestingly, though,one thing that a stock Bensen doesn't have much is slip-roll coupling. There's not enough side area below the CG to create it. The Umbaugh/Air&Space, inspired by Bensen but a radically different design, has it, however.


            • Bensen came up with a design that any teenager with a paper route could afford and was able to build with a minimum of tools; mainly an eggbeater drill, a file and a hacksaw.

              The B-7 had a horizontal tail which was dropped on the B-8 for reasons I don’t understand. Perhaps the offset gimbal rotor head along with over reflexed and over balanced wood blades provided what Bensen believed was adequate stability. The over reflexed, torsionaly flexible rotor blades limited top speed to ~60 mph. Also, a direct drive Mac engine didn’t apply gobs of torque to the prop.

              But times have certainly changed in the internet age; no more teenagers with paper routes, disappearing newspapers and $100K Bensen derivatives.


              • Here's what Cierva said about torque compensation:

                US patent 2098320 Juan de la Cierva
                Filed March 6, 1934 (UK patent application filed March 13, 1932)


                …The problem of torque reaction correction therefore assumes great importance. In fact, it has been found (in machines employing tilting of the rotor for control purposes) that a greater amplitude of lateral control movement of the rotor is required to compensate the torque reaction in all conditions of flight from engine-off to full throttle than is required for the purpose of lateral control. Further, if the torque reaction is compensated by displacement of the rotor, or by an equivalent (such as modification of the periodic pitch variations of the blades thereof) a continual adjustment is necessary during flight, since, while at a constant throttle setting the reaction torque is substantially invariable, the couple opposing it is the resultant of aerodynamic forces (for which the rotor is principally responsible), inertia forces and gravity; the aerodynamic forces being subject to fluctuations on account of wind gusts and changes of attitude of the aircraft while the inertia forces vary with the accelerations to which the aircraft is subjected. The couple opposing the airscrew reaction torque thus depends on the momentary values of the aerodynamic forces and of the accelerations….


                • Bingo! Translation from techno-speak: Using the rotor to stabilize the airframe against torque is a bad idea -- because the rotor's thrust varies constantly with gusts and maneuvers.

                  Using the rotor to stabilize against PPO moments is equally a bad idea, and for the exactly the same reason. Either get rid of the moment by design, or neutralize it with fins.


                  • Doug , in europe, and more precisely in France our reputation in hugely bettering, the reason for this is that general aviation is loosing new pilots because of it's great cost.
                    for the price of a 100.000 euros brand new gyro ( enclosed like a DTA) you would only get an old certified FW aircraft that needs to put an other 100.000 to keep it legaly usable

                    Among the ultraligths aftc available more and more people are buting gyros coz they look good and because they take fewer space in hangars

                    in the us you have cheap certified planes and large hangars coz your country is huge, there for FW pilots ans industry is powerfull and they can criticize gyros saying lots of things

                    In france most of the serial accidents took place long ago in the home builders community where guy's don't want to spend enough time and money fabricating proper HS with airfloils , they dont want to build ctl gyro because they have the reputation of flip down while taxing ( which is stupid but peole are stupid)

                    most of the home builder where making low profiles gyro with small plywood HS ... add to this that they did not want to pay for training it gave many many fatalities and a bad reputation

                    I love home building but we need a rutan to make plans of safe a tandem gyro

                    since magni , ela, autogyro started offering gyro and since trinning was possible ( on those 2 seats gyros) the biggest piloting errors and it put and end to fatalities and bad reputation, there are 600 gyros ( and mabye more) gyros in this small country and reputations is getting better

                    but accidents still happend ( but rarely)

                    I think that one of my hangars fellow died because because of roll torque ( this my theory)

                    he was nervous this day because he had to be on time at a familly lunch and because he wanted to perform a fligth test of his gyro with doors on ( a dta jyro), he took off without fastening his seat belt,

                    he climbed 50 ft and the the gyro overtured and falled rotor first on the ground staying on the stripe axis

                    for me he pushed the stick and entered in zéro G at fulll trottle,

                    Last edited by jm-urbani; 01-16-2019, 04:25 AM.


                    • JM -- I hope that, if we keep the pressure up, the promoters of these new gyros (whether $15,000 gyros or $100,000 gyros) will design out any slip-roll and torque-roll characteristics.

                      It's perfectly possible. Such design improvements do not necessarily make the aircraft either ugly or unstable on the ground.

                      Look at corporate jets. They all have fairly high cockpits and nose-gear legs. They are designed to look sexy and fast, the better to sell to their rich customers -- and they succeed.


                      • if tandem doms gyros had both a retractable front gear ( like Long EZEs) and a fuselage they would look better.
                        for the moment they look like a Tour Effiel
                        monoseats dom's are "nice" but tandems are uggly
                        high profile gyros are not unstable on the ground, it is a legend ... rising the Cog by 10 inch compared to a low profile gyro won't make to gyro unstable
                        those who say this are talking just to say something, or because their gyro are low profile gyros
                        people should learn to land a gyro like a gyro ( with nearly zéro roll) instead of landing it like a FW aircraft,


                        • Beauty is in the eye of the beholder.

                          Having flown two seat Dominators I find them beautiful just as I find a woman with curves beautiful when some prefer thin and scrawny.

                          You may have noticed that most of my pictures are taking while flying because that is how I spend most of my time in a gyroplane despite the mile taxi to the run-up area for runway three zero at KSMX.

                          I think this picture of The Predator is beautiful despite her high stance and lack of retractable landing gear. I have a client in the back seat with vast aviation experience that loves the way she flies without power-pitch-yaw coupling.

                          I don’t see the value in retractable landing gear on a ninety knot aircraft and I see weight, complexity and having to remember to put the landing gear down as serious negatives.
                          Regards, Vance Breese Gyroplane CFI


                          • Vance ,
                            precisely unlike doms, the predator looks like a conventional flying machine with it's fuselage, it does not look like a Tour Eiffel
                            Your predator looks nice,
                            safe, reliable, nice ..
                            as for the gear it was just an idea, certainly not adapted to gyros you'r rigth


                            • Vance beat me to it. The Predator seems to me to have nearly an ideal layout for a semi-enclosed tandem gyro. And CLT tandem is the way to go for (relative) efficiency, especially in a pusher gyro.

                              Note that Ernie Boyette knows perfectly well how to build a CLT, full enclosed, side-by-side pusher gyro. His LFINO was just such a craft.

                              I read that the Eiffel Tower was controversial when proposed and built. Some thought it an ugly celebration of soulless iron industrialism. Many more, however, thought (and think) that it is an elegant giant sculpture.

                              Now, the George Washington Bridge in NYC is seriously industrial-functional, lacking the grace of, say the Golden Gate Bridge, built in the same era. I read also that the GW's criss-cross girder structure was supposed to be covered, but it was left exposed to save money. IOW, it's the Dominator of suspension bridges. Or the Dom. is the George Washington Bridge of gyros.


                              • Hi Doug,
                                I am not thinking the dom is a soul less piece of iron.
                                I simply fear folks prefer more conventionnal looking gyro's