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Dubai - WAG - Gyro down 9.12.15

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  • I have built some enclosed machines that I had to put a fin around the mast to tame a really nasty slip roll that tried to kill me before I got it sorted out. Gyro boats need these and lots of horizontal stabilizer to stabilize the hull which is a lot of drag in a slip.
    Norm

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    • We had to demonstrate that no uncontrollable slip-roll coupling exists in the ArrowCopter by applying full rudder deflection in either direction while flying at 160 km/h (top of green arc).

      Greetings, -- Chris.
      Read about my trip across the USA in an MT03 gyro here.

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      • Here is the final investigation report and findings. Torque roll ... not so much. More like a 20 hour gyroplane pilot distracted by his helmet coming off in a WAG race. What do we expect.

        https://www.gcaa.gov.ae/en/ePublicat...XblgY6QpO04XeM

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        • https://www.gcaa.gov.ae/en/ePublicat...XblgY6QpO04XeM

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          • Thank you for posting that link Abid.

            It gives me a place to direct clients when they inquire about why "helmet secure?" is on the pre-takeoff checklist for The Predator.

            This is not the only mishap involving a helmet not being secure; it is the most recent and best reported that I am aware of.

            I feel there is a lot of good information available in the report.

            Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

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            • I found it interesting that the last paragraph in Section 1.17.1 states that the normal takeoff airspeed of a gyrocopter at Maximum Take Off Mass is 30 km per hour.
              ​​
              Maybe the FAI supplied that figure for this accident report, but I seriously doubt anyone flying gyros can lift off @ under 19 mph.

              My experience is I was lifting off around 32-33 mph when I was powered by a Rotax 503 in a single place gyro. As my personal weight got heavier and additionally, when I switched to a four stroke engine that added about an additional 65# to the gyro's weight, that my lift off speed is around 46-48 mph.

              Another gyro pilot I know flying a single place Rotax 912 states he lifts off also in that upper 40's mph range. A two place machine likely lifts of @ an even higher airspeed, especially when two people are on board.

              I was struck how this accident had such a continuous stream of mistakes on the part of the pilot to make it a chain made up of several links. It does appear that his cyclic movements did cause the rotors to slow too much, and seems to indicate a severe flapping to have caused one rotor blade to break off. It also appears to have been a torque roll situation.

              Also, striking is the lack of oversight of the race officials, such as allowing a pilot w/ only 20 some hrs. of PIC (way below their 45 hrs. of PIC time minimum).

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              • We had a scary loss-of-helmet incident at a flyin in New Hampshire some years ago. A passenger taking a ride in a SxS Air Command lost a helmet on takeoff. It hit the prop and the rotor on the way out. The pilot, just climbing out with a wooded swamp ahead, managed to turn off track and squeeze the gyro into a backyard. No injuries.

                When hopping students I took to pulling on the passenger's chin strap myself (and to hell with personal space) before taking off.

                But here the aircraft design is not off the hook. An aircraft is safer it if does not execute an uncommanded snap roll if/when the pilot is distracted. Sure, a good pilot won't allow himself/herself to BECOME distracted (first rule: fly the aircraft). In the real world, however, fallible human beings are a part of the aircraft-pilot system. Recreational gyros should not be all-out widowmaker racers like the Gee Bee.

                The system should be designed to employ available. cost-effective fail-safe measures. Torque compensation in gyros has been around since the Cierva era. IMHO, every designer should design for torque- and slip-roll compensation, and then test to verify it.

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                • Torque roll it seems to me was later. He made plenty of errors including going to low G with his cyclic actions. He was toast right there flying so low. Wish they would consider safety as the #1 priority at such events and only allow experienced pilots to do this type of event. 45 hours for a pylon race is also a joke

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                  • Our long custom in the gyro world (dating back to Igor Bensen) is to blame every crash in which low G may have been involved on the low G itself. If low G is usually or always lethal, then the autogyro itself is a fatally flawed design concept, and has been so from Cierva's time. This is exactly what a great many non-gyro fliers have believed all along.

                    The plain fact is that low G is inevitable in an aircraft, thanks to thermal and mechanical turbulence. These natural, normal atmospheric disturbances simply cannot be avoided. IOW, you are going to encounter low G most times you fly a gyro. If, every time you do, you are dancing on the edge of a fatal crash, then the critics are right -- you (we) are idiotic.

                    Fortunately, things aren't (or don't have to be) that dire. When a gyro goes haywire in a short-duration low G event, it's not the low G, but fuselage instability in the face of loss off rotor thrust, that usually causes the splat. The airframe must be designed to track straight, and not execute uncommanded aerobatics, when rotor thrust gets low. This requirement means that the frame must not have uncompensated HTL, divergent slip-roll coupling or uncompensated torque roll.

                    Cierva and his immediate successors worried about all these low-G stability problems, and designed to prevent them. They used CLT engine placement, large H-stabs, differential stab incidence, wings with tremendous dihedral and large dorsal fins (and/or mast fairings). We should do at least as well.

                    Yes, there's obviously pilot error involved in this crash. In fact, never mind the helmet, it's pilot error to fly that fast and aggressively with such low hours in the aircraft in question.

                    Still, the behavior of the gyro once things began going south also reveals some needless crashiness, traceable to slip-roll and/or torque roll. These problems can be eliminated by design.

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                    • Originally posted by Doug Riley View Post
                      Our long custom in the gyro world (dating back to Igor Bensen) is to blame every crash in which low G may have been involved on the low G itself. If low G is usually or always lethal, then the autogyro itself is a fatally flawed design concept, and has been so from Cierva's time. This is exactly what a great many non-gyro fliers have believed all along.

                      The plain fact is that low G is inevitable in an aircraft, thanks to thermal and mechanical turbulence. These natural, normal atmospheric disturbances simply cannot be avoided. IOW, you are going to encounter low G most times you fly a gyro. If, every time you do, you are dancing on the edge of a fatal crash, then the critics are right -- you (we) are idiotic.

                      Fortunately, things aren't (or don't have to be) that dire. When a gyro goes haywire in a short-duration low G event, it's not the low G, but fuselage instability in the face of loss off rotor thrust, that usually causes the splat. The airframe must be designed to track straight, and not execute uncommanded aerobatics, when rotor thrust gets low. This requirement means that the frame must not have uncompensated HTL, divergent slip-roll coupling or uncompensated torque roll.

                      Cierva and his immediate successors worried about all these low-G stability problems, and designed to prevent them. They used CLT engine placement, large H-stabs, differential stab incidence, wings with tremendous dihedral and large dorsal fins (and/or mast fairings). We should do at least as well.

                      Yes, there's obviously pilot error involved in this crash. In fact, never mind the helmet, it's pilot error to fly that fast and aggressively with such low hours in the aircraft in question.

                      Still, the behavior of the gyro once things began going south also reveals some needless crashiness, traceable to slip-roll and/or torque roll. These problems can be eliminated by design.

                      An airframe to track straight with no wing on, with thermals, gusts, thrust of varying degree that is still in pilot's control, rudder input still effective and a pilot flailing the stick to its very stops trying to catch his flying helmet behind him? Show me a gyro that will handle that please.
                      His accident started when he decided he could with 20 hours PIC go to World Air Games and do gyroplane pylon racing. It came much closer when he started flying with unbuckled helmet chin strap, his fast un-coordinated turns to one side inched him closer, his helmet flying off his head and his reaction to it, sealed his fate. Unfortunately, no amount of money or any other thing comes in between Mr. Darwin and aviation. Aviation applies Darwin's theory to all of us really quickly.

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                      • My point, Abid, was not that no crash would have occurred in this case with better frame stability. I don't know that.

                        The Dubai accident, however, turned out to be an unintended test of the aircraft's frame stability. Frame stability might make a difference in other cases. We have had crashes in which frame stability WAS the culprit. We've had lots and lots of PPO's traceable to HTL, for one thing. There also have been crashes in which divergent slip-roll coupling was pretty clearly at fault. Torque roll contributes to many low-G crashes,as various photos and videos attest.

                        A gyro must respond to the pilot's control inputs, obviously. If the pilot's control inputs are wrong but the craft responds faithfully, that's pilot error, not a design problem.

                        Pushing the stick forward should reduce the rotor disk's angle of attack, and can be expected to cause the nose to drop to some extent. Nose drop is NOT necessary with forward stick in a direct-control rotor, and it's better if the drop is quite limited and is aerodynamically "snubbed" (as it will be if the craft has an adequate HS). What should NOT happen when the stick is pushed forward, no matter how fast, hard or far, is a roll. This is an uncommanded maneuver.

                        Ditto divergent slip-roll coupling. Uncoordinated flight in a gyro is mostly a novelty; we can steepen our glide as much as we want without slipping, by simply slowing down. Still, there is no reason why, if the craft enters a slip, the slip ought to grow and grow UNCOMMANDED until the gyro rolls over in the air. We all know that FW planes are designed with the opposite trait -- they exhibit dihedral effect. When slipped, the FW plane tries to level itself and point in the direction it's travelling.

                        A gyro can and should be designed with the same healthy behavior.

                        The Dubai accident report suggest that the aircraft in question had one or more of these issues. The issues came to the fore when the pilot committed his control errors.

                        We should press our designers to do better.

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                        • Originally posted by Doug Riley View Post
                          My
                          We should press our designers to do better.
                          The problem Doug, is that they don’t know how since most designers of modern hobbycopters aren’t engineers and are simply following the Bensen pattern. The originator of the Eurotub, Vittorio Magni, was a helicopter mechanic who learned how to “design” gyros by having built a Bensen from plans.

                          The shame of it all is that Cierva had solved most of the stability problems of gyroplanes in the 1930s, resulting in a machine that had a safety record far better than contemporary FW aircraft.


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                          • chuck let natural sellection do it's work

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                            • Originally posted by jm-urbani View Post
                              chuck let natural sellection do it's work
                              JM, I don’t mean to disparage Italian products or Italian designs.

                              My favorite wife was an Italian design, having been born in Italy and brought to the US at age 6 when her parents emigrated.

                              My favorite automobile was a 1959 Alfa Romeo Giulietta Sprint Veloce. My Italian wife was ticked; she said: “$4300 and it doesn’t even have a cigarette lighter!”

                              Unfortunately, both had flaws.


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                              • I am Italian Rooted too, but unlike your wife we only travelled 30 km in my familly, but I would have been fun if they had chosen to get to america instead ot france, I have never come but i am going to start my exploration in April ( my son is a stock car fan and we are going to Rchmond to see a nascar race)

                                I fly a Magni M16 on a regular basis, I have flown it in the worsts turbulent conditions I could not even have imagined before and I always felt safe ( feeling is not safety of course), rotors are fantastic, 3000+ M16 that are in my hangar are still flying safely with the same rotors that when they were built, there is nothing to say about those products except they work perfect, tervamaki ( engineer) and vittorio magni have done a succefful job and won the match

                                Ernie did not but I think he never tried to win anyway, his clients belong to those who had understood what was the good design, low profile client don't think they are consummers

                                it is like linux vs windows, windows won , but linux is better ... that's life

                                on the other hand it is really easy to find that the majority of airplanes have it's prop center, it's engine ( big mass) it's pilot and passenger located on the same line ... and it is not rocket science to find out, thous who say the opposit have something to sell

                                when I have drawn my gyro, I took rotax engine CAD's, I did all the CAD's of the other main components ( wheels, landing gear, tubes, rotor, rotor head etcetc) I simply put the tall tail, prop center, engine center of mass, passenger nostril, pilot nostril , fairing center of drag on the same line ( it is nearly a cylinder) , then I put the rotor where it had to be, and the tubes in order to out all of those components alltogether and when i calculated the center of mass vertical location : magic in was 10 cm under the prop line ... belive me I am the most average man possible and I managed to do the job ...

                                event without any calculations it is so simple to draw a ctl gyro ...


                                makers don't want to do the same because Dom's like gyro are uggly for customers, and because it is so easy to get in a hang, mesure a MTO3 and to copy it and to say they have designed a flying machine... anyway customer have had the possility to read of what you, Jean Fourcade,Ernie etc said it they make an other choice then Demanding ctl machine it means they are ready to risk their life ... natural sellection

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