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  • #31
    Consult the maintenance manual for the proper rudder cable tension, it does warn of a possible high speed flutter if not correct.

    Also, because of how the ELA rudder pedals are linked to the nosewheel stepping hard on both pedals has no effect on rudder cable tension.

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    • #32
      Rdalcanto, I have used the iPhone for vibration measurments on many instruments, but not a gyro. I would recommend that you choose a location that specifically reflects what you are trying to measure. That is kind of a vague answer. I am sure that Jean-Claude would have more insight into a suitable location. Reguardless of location, it is important that the phone be firmly mounted so that the measured movement reflects the vibration from that component. I want to make clear the "Vibration" app I use on the iPhone measures on three axis, and you can calibrate the axis. It does not provide you with, for example, radial vibration modes, not give you a solution as to mass and radial location for balance. The data is exportable, so you could solve for such a solution.

      Cheers,
      Dave

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      • #33
        I think I have discovered the cause of the annoying shake in my gyro. While flying yesterday evening, in very still air, I discovered that the shake gets noticeably stronger when yawing to the right, and diminishes when yawing to the left... I knew already that the shake was absent when flying with the engine at idle, either in vertical descent or when gliding at any speed...

        I believe now that the shake is caused by some sort of oscillating turbulence caused by the interaction of the prop flow with the (big) fixed trim tab installed on the rudder. It gets transmitted to the body, and from there to the control rods, so it's felt in the stick...

        Any comments are welcome...

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        • #34
          Lots of really good information,many thanks to all or you.

          I noticed that after looking at the ELA gyros that the rudder is not balanced,unblanced control surfaces will cause all sorts of problems, a balanced rudder will

          have a portion of it forward of the hinge line,that arangement allows balancing and the forward portion makes the rudder earier to push on.

          However at the slow speeds gyros fly unbalanced control surfaces are usually good and do not cause problems,but the rudder on gryos are

          guite large and could cause the vibration.
          Last edited by eddie; 12-07-2017, 08:29 AM.
          Best Regards,
          Eddie Sigman,Polvadera,nm
          (575) 835-4921

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          • #35
            As I understood it, the rudder vibrates not because of intrinsic flutter but because it is exposed to vortices shed by some upstream structure. Balancing the rudder will not help in such a situation.

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

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            • #36
              It's called buffeting. I think the upstream swirl of the prop may assist keeping the flow attached to the right side of the fuselage while promoting unnattached flow on the left. The vortices or bubbles that are shed then react with the rudder downstream. I had a similar problem on my aircommand CLT with a wide modified fairing at around 60mph cruise. Also the original Xenons with their wide cabin and bluff rear would not so much buffet but had improved climb when flown with some some slip maybe because the prop was now seeing cleaner flow because it interacted favourably with the swirl. All this is speculatiion but might explian what's going on. If so vortex generators on the left of the fairng should help The power settings may also have an effect as they change the angle of attack of the fairing on some gyros.

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              • #37
                Xavier
                I've just seen a newish ELA in a hanger where I'm working I couldn't talk to the owner but remember he complained about the rudder buffeting the last time I was thereHe even talked about cutting the rudder and tail to make a balanced rudder.
                The guy I was working with told me that ELA had supplied him with a new rudder that had some sort of offset hinges. I looked at it and couldn't see anything that was obvious to me but did see the old rudder in the corner of the hanger so that part of the story is true.

                I was also told that the owner found a crack in the welds in the tail boom and had to weld the strengthening piece that ELA are quietly offering to anyone who finds cracks in the tail boom. We've had at least one fayality in France with the tail coming off due to bad welding.

                I left a voice mail with the owner asking him to ring me, if he does I'll let you know what I find out.

                It seems to me that ELA have a problem, they know about it and have a solution but aren't telling anybody about it. This seems to be typical of them hiding problems from their customers. I've given up trying to work with them, they're the worst vendor I've come across so far and I wouldn't recommend them to anybody.

                You speak Spanish so should be able to communicate with them ask them about the ELA at Lens in France. They speak very little English and non at all once you have a problem they just stop answering your emails.

                Mike G

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                • #38
                  Originally posted by Mike G View Post
                  Xavier
                  I've just seen a newish ELA in a hanger where I'm working I couldn't talk to the owner but remember he complained about the rudder buffeting the last time I was thereHe even talked about cutting the rudder and tail to make a balanced rudder.
                  The guy I was working with told me that ELA had supplied him with a new rudder that had some sort of offset hinges. I looked at it and couldn't see anything that was obvious to me but did see the old rudder in the corner of the hanger so that part of the story is true.

                  I was also told that the owner found a crack in the welds in the tail boom and had to weld the strengthening piece that ELA are quietly offering to anyone who finds cracks in the tail boom. We've had at least one fayality in France with the tail coming off due to bad welding.

                  I left a voice mail with the owner asking him to ring me, if he does I'll let you know what I find out.

                  It seems to me that ELA have a problem, they know about it and have a solution but aren't telling anybody about it. This seems to be typical of them hiding problems from their customers. I've given up trying to work with them, they're the worst vendor I've come across so far and I wouldn't recommend them to anybody.

                  You speak Spanish so should be able to communicate with them ask them about the ELA at Lens in France. They speak very little English and non at all once you have a problem they just stop answering your emails.

                  Mike G
                  Whoa !!!! Tail came off due to bad welding? You sure?
                  We had resonance issue in testing when we had lightened our tail and also changed tubing vendor to a US mill manufactured tubing. For some reason when the tail got side gust load its frequency matched a harmonic of the welded frame tail boom. We obviously caught it and changed both internal structure of the tail in manufacturing and tail boom stiffness to change their frequencies so it would not resonate. Just this week one of the customers compliant about vibrations in his new gyroplane that was being test flown, trying to work with the rotor wasn't helping much and we noticed that vibration is very high frequency and you could feel it even on the ground. Eventually we figured out that one of the engine mount rubbers was not inserted into the ring all the way. Of course by this time we had dynamically balanced a prop already which is good but probably was not completely necessary (0.28 IPS down to 0.08 IPS). Its always interesting when some of these happen what turns out to be the reason.
                  Last edited by fara; 12-08-2017, 09:43 PM.

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                  • #39
                    Lots of thanks to all of you for the very valuable comments and suggestions. I'll try some some possible solutions and hope to report back soon. Anyway, I have a pending appointment with the people at the ELA factory in order to solve the problem. It means, however, a 400+ km flight, and I'm reluctant to do that in the winter. Perhaps next spring...
                    Concerning the cracks in the tail boom, my gyro was the first ELA factory-reinforced for that contingency. The delivery was delayed for some months because the civil aviation authority had first to approve the mod.
                    Mike: please give my e-mail to that ELA pilot at Lens. I'm very interested to exchange opinions with him, as it appears that we have exactly the same problem. He may write in French. I know the language well enough.

                    Comment


                    • #40
                      XXavier, when was your ELA manufactured? Also, if it’s not too much trouble could you post some pictures of the tail boom reinforcements the factory installed, I would like to compare them to a ELA we have here.

                      Comment


                      • #41
                        Originally posted by Alan_Cheatham View Post
                        XXavier, when was your ELA manufactured? Also, if it’s not too much trouble could you post some pictures of the tail boom reinforcements the factory installed, I would like to compare them to a ELA we have here.
                        It was delivered to me on June 2017. I'll make the photos soon. I think that ELA has already informed of all this, through maintenance bulletins...

                        Comment


                        • #42
                          The tail failure in France was in 2015. Here CN 2017-ULM-01 - ELA07.pdf
                          is the DGAC (French FAA, CAA) directive that instructs all owners of ELA 07 type gyros to carry out an inspection of the tail boom at the welds under the prop before the next flight or the aircraft is grounded, it then says to carry out the inspection every 4 months or 100 hours afterwards.

                          And here BEA2015-0318.pdf is the French BEA (Bureau of investigation) report into the fatal crash in June 2015. The conclusion is pretty damning.

                          Two failures at the welds due to fatigue.
                          Click image for larger version  Name:	ELA tail boom failure 1.jpg Views:	1 Size:	103.7 KB ID:	1127931

                          Click image for larger version  Name:	ELA tail boom failure 2.jpg Views:	1 Size:	196.5 KB ID:	1127932




                          « Les examens visuels et métallographiques ont mis en évidence de nombreux défauts de soudure : irrégularités, surépaisseurs, excès de pénétration, manque de pénétration, rochage, projections métalliques. Les défauts les plus pénalisants (manque de pénétration, rochage et excès de pénétration) se situent à la racine, c'est‑à-dire à l'intérieur des profilés. La majeure partie des longueurs soudées en zone A et en zone B présentent un ou plusieurs de ces défauts.”
                          Unofficial Translation
                          The visual and metallurgical examinations showed evidence of numerous welding defects:
                          Irregularities, over-thickness, excessive penetration, lack of penetration, root porosity (also called sugaring or cauliflowering), metal spatter. The weld defects that penalise the most (lack of penetration, root porosity and excessive penetration) were situated at the root, i.e. on the inside of the tubes. The major parts of welds in zone A and B included one or many of these defects.
                          The report goes on to say that in July 2015 there was another ELA involved in an accident where the tail boom failed. A subsequent investigation of the tail boom showed the same weld defects. Spontaneously another ELA owner sent pictures of his failed tail boom. (the welds in this photo are a disaster, I doubt if they were done by ELA).

                          ELA issued a Service bulletin 19 ( Service-Bulletin-Nº-07-019-ENG.pdf ) in Dec 2015 stating:

                          "It is difficult to know the reason of the apparition of that crack. We think it could happen due to bad
                          operation, modification of the original configuration, rudder flutter events or high rotor vibrations.
                          Whether for whatever reason, we have decided to issue this “Service Bulletin Nº19” to alert all
                          users to inspect the area in question and thus ensure the safety of our gyroplanes."

                          If it wasn't so tragic, their "it is difficult to know the reason" would be laughable. They knew only too well what the cause was, lousy welding, no backing gas when TIG welding stainless and non-existent quality control.

                          ELA quietly put this on their website and say it is up to the owners to remain informed. Their website hasn't functioned correctly since at least July 2017 when I asked why I couldn't download copies of the Bulletins and I still can't download all of them today. So how are owners supposed to stay informed?????

                          Mike G CN 2017-ULM-01 - ELA07.pdf BEA2015-0318.pdf
                          Attached Files
                          Last edited by Mike G; 12-12-2017, 04:22 AM.

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                          • #43
                            And another issue

                            ​​​​​​http://www.seguridadaerea.gob.es/med...a_01_13_en.pdf

                            Here's the description from the Spanish Authorities:

                            ​​​​​​"As a result of breakage of the hub bar in the area of blade attachment in a microlight gyroplane manufactured by ELA AVIACIÓN S.L., model: ELA-07 R-100 during flight broke away a blade together with a part of the hub bar to which was attached. The "Comisión de Investigación de Accidentes e Incidentes de Aviación Civil" (CIAIAC), has established that the cause for which the blade was broke away in-flight, has been produced by a fatigue process, favoured by some holes counterbores on the underface of the piece. It also has joined the fact that the piece has not manufactured with the material detailed in the drawings of project, specified by the manufacturer."

                            ELA put out Bulletin SB 16 regarding this, but this SB states in its description:

                            "The CIAIAC (civil aviation accident and incident investigation commission) in collaboration with AESA (Spanish agency for aviation safety) have determined that: In the case of non-proper use, storage, inspection and maintenance of the gyro, there is an area in the hub bar where some cracks can appear during operation. This area is located in the lower face of the hub bar, where the bolts heads are inserted in a machined groove. Non-compliance with this service bulletin may cause the total collapse of the rotor in flight and therefore the loss of life of the pilots."

                            My highlighting in red.

                            Reading the above looks like two parallel realities.

                            And we haven't even touched on the subject of the melting fuel tanks..

                            Comment


                            • #44
                              helipaddy: that problem of the hub bar was solved with a new design. Most (if not all) ELA gyros have been fitted (or retrofitted) with the new hub bar, that has been standard issue for at least five years.

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                              • #45
                                XXavier
                                Yes it has been sorted with the new 145C hub bar. But after buying a 154B bar for a different SB, and then buying a 145C hub bar for our machine, I'm hoping this hub bar and teeter block is made correctly with the material specified in the type approved drawings

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