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Chris Lord October 31, 2018

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  • #76
    Originally posted by Kolibri View Post

    loftus, they've not even announced an In Memorium that their USA COO died in one of their products.
    I doubt they'll "
    chime in with anything they know".

    But they sure were busy revising the Cavalon POH at about the same time.
    Yeah agreed but not surprised. At the same time I know Autogyro have tended to stay off the forum because as you know it can become a ****show.
    I'd still like to know the mechanism of a runaway pump etc. Clearly electrical, just don't understand quite how it happens.

    Comment


    • #77
      It is not hard for me to imagine one of the little wires to the buttons on the cyclic shorting out or the buttons themselves sticking.

      In my opinion the brake to flight switch seems pretty bullet proof with the most likely failure being to lose pressure altogether.

      If the detent failed and it switched from "flight" to "brake" in flight it would be disquieting rather than catastrophic.

      It is hard for me to imagine enough force generated by the trim system for it to be a problem for an experienced pilot.


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

      Comment


      • #78
        I'm wondering what max air pressure would be if the limiting valve/device failed and the compressor never cycled off.
        That pitch trim cylinder is quite large, and reportedly quite powerful.



        8 December 2018___________________

        The Calidus, MTOsport, and MTOfree POHs do not have the new Emergency Procedure items of Trim runaway, Pitch oscillation recovery, and Vibration.
        Seems odd since they also use the pneumatic trim system with FLIGHT/BRAKE switch, and would require such text in their POH.

        However, the MTOsport 2017 (POH-M17_1.1_EN.pdf) does have them.
        AutoGyro_POH_MTOsport-Model2017 Revision 1.1 – Issue Date 13.04.2018

        What's interesting, however, about the Cavalon POH 3.1 is although it does have the same verbiage, it hasn't the MTOsport 2017 POH's careful layout.
        The text looks very sloppily copied/pasted. Also, the Cavalon POH 3.1 in German has the better layout, however, the concurrent English version seems rushed.
        This reinforces my hunch that it was done consequently to Chris's crash, and hurriedly so.



        ___________
        If the detent failed and it switched from "flight" to "brake" in flight it would be disquieting rather than catastrophic.
        Perhaps some curious yet brave AutoGyro owner could take off from a long runway, maintain 5' AGL and try it.

        Nevertheless, what I'm postulating is a much different scenario than the Cavalon POH's 3.8.4(ii) where the compressor popped a breaker and the pitch trim cylinder had little/no pressure.
        Rather, not only is there "BRAKE" pressure on the up-actuator, but it also refuses to dissipate.

        I've recently carefully inspected an AutoGyro rotorhead, and talked to some folks.
        When the "BRAKE" mode is active, the actuator arm is pressurized to slide up, and moves the pair of hinged levers flush with
        the underside of the inner torque tube to hinge up the rotor brake. These levers are about 35mm long, providing significant leverage.
        As it pushes up the rotor brake, it simultaneously pushes the rotorhead forward to the stop.

        If Chris added nose-up trim, in "BRAKE" mode (accidental or failed) this would have been backwards and moved the actuator further up.



        Click image for larger version  Name:	AutoGyro rotor brake.png Views:	1 Size:	744.3 KB ID:	1140662



        If that pitch trim actuator arm had been pressurized up, even if overcame by muscled aft-cyclic the actuator would still be braking the rotor.
        Furthermore, as I understand the mechanism, increasing aft-cyclic would also increase the braking force by pulling the rear of the torque tube into the actuator. (This was not described in any AutoGyro POH.)

        Again, I don't know if the pneumatic selector (or switch) failed and locked up the actuator, but it would explain a lot.
        Such a malfunction would have presented a very confusing in-flight situation, with little time to diagnose it.

        I think it a bad idea to combine trim and rotor braking under one switch and valve. IMO, they should be separate controls and systems.
        As Einstein once quipped, "
        Everything should be made as simple as possible, but not simpler."


        ____________
        N198LT dropped out of the air from 150' AGL.
        That has never been adequately explained.

        The only thing that seems to make sense of this NTSB witness statement:


        In an interview and a written statement, a witness stated he was driving southbound on the highway that paralleled the shoreline of the lake at the time of the accident.
        He said the gyrocopter was travelling northwest bound, about 300 feet above ground level "with very little airspeed" and appeared to be turning to the east.
        The gyrocopter then "entered an autorotation" then, when it reached "… about 150 feet the nose of the aircraft dropped immediately turning toward [the] east then back toward the north."
        The gyrocopter descended from view [and crashed].
        . . . is decayed rotor rpm.

        And what so far seems to me the most plausible reason for decayed rotor rpm is that the rotor brake was engaged.

        Chris seemed to be ruddering around in those last moments.


        when it reached "… about 150 feet the nose of the aircraft dropped immediately turning toward [the] east then back toward the north."
        This portion may be telling.
        An engaged rotor brake would cause the Cavalon to yaw left, so he may have been fighting that with right rudder.
        If the rotor rpm had decayed sufficiently, and the Cavalon began to fall, he may have then had too much right rudder, which swung the nose east.
        As he quickly corrected, the nose swung left back north.
        I think during those very last seconds, all he had was power and rudder, and neither one could help him by then.
        PP - ASEL complex (C172RG, Piper 180, C206, RV-7A), SP - Gyro (Calidus, RAF, Sport Copter II, M912), soloed in gliders

        "
        When an honest but mistaken man learns of his error, he either ceases to be mistaken -- or he ceases to be honest."

        Comment


        • #79
          Sometimes "stupid simple" is not so stupid.

          For comparison: The original Wunderlich rotor brake was quite fail-safe. It was/is engaged by manually pushing a plastic puck up against the forward edge of the rotor head. It would only stay there (and stay engaged) as long as full forward stick held it there. Back off stick pressure, and it simply dropped down and disengaged. If worse came to worst, the casting that held the actual brake pad pivoted on the forward end of the torque bar on two rather thin ears of cast pot metal. If engaged hard, the ears it would just break off, again disabling the brake.

          Comment


          • #80
            I think it was Einstein who quipped, "Things should be made as simple as possible, but not simpler."
            PP - ASEL complex (C172RG, Piper 180, C206, RV-7A), SP - Gyro (Calidus, RAF, Sport Copter II, M912), soloed in gliders

            "
            When an honest but mistaken man learns of his error, he either ceases to be mistaken -- or he ceases to be honest."

            Comment


            • #81
              The problem with simple, straightforward designs Doug, is that they don’t sell. The general public likes to think their expensive toy is high tech, state of the art; therefore, all the superfluous bells and whistles.

              Comment


              • #82
                I've been pondering further my theory of in-flight rotor rpm degradation.
                Another possible cause of that in N198LT could have been an involuntarily engaged prerotator.
                It's happened before in a Cavalon (although without causing a crash), as Desmon Butts described in 2016:


                I know of a Cavilon in the states that the pneumatic system kept the pre rotator engaged and got so hot the shaft turned blue. The whole system had to be replaced.

                This gyro is one that was built with issues. When I was asked to look at it the pre-rotator would engage at random times while on taxi. I told the owner not to fly it until it was fixed. It however had been flow that way by the building organization and dealer then delivered that way to him. They had the flights like that .
                PP - ASEL complex (C172RG, Piper 180, C206, RV-7A), SP - Gyro (Calidus, RAF, Sport Copter II, M912), soloed in gliders

                "
                When an honest but mistaken man learns of his error, he either ceases to be mistaken -- or he ceases to be honest."

                Comment


                • #83
                  Whether or not the pneumatic system contributed in this case, I must admit the brake and prerotator system design were significant factors in my decision to go with a Magni. The rotor brake is simple: off a Vespa scooter, I understand, with a cable activation, panel warning light, and connection to the RRPM gauge (which doesn’t come on until the brake is off). The prerotator is also cable activated so you have a good sense of the force being applied (vs. a pneumatic system, where you have no sense of this and I’ve seen several broken prerotator brackets on MTOs). Also, the flex cable for the prerotator means there’s no restrictions on pulling the stick back (and certainly no locking mechanism to hold/keep the stick forward) while the prerotator is engaged.

                  Magni isn’t the only one with these attributes (seems to me the AR-1 has similar features). This is not at all to say I’m speculating this was involved in this accident; only that, to me, these design features have their advantages over the pneumatic systems and rigid prerotators beyond the potential of this type of possible in-flight failure.

                  /Ed

                  Comment


                  • #84
                    A Magni would be my second choice of gyro, and it's a good machine.
                    I also prefer the flex-shaft prerotator for those reasons.
                    No 90° drive-shaft linkage to prevent prerotation with the rotor fully back.
                    (The AR-1 does not have a flex-shaft, but an ELA/AutoGyro/etc. type drive-shaft.)
                    PP - ASEL complex (C172RG, Piper 180, C206, RV-7A), SP - Gyro (Calidus, RAF, Sport Copter II, M912), soloed in gliders

                    "
                    When an honest but mistaken man learns of his error, he either ceases to be mistaken -- or he ceases to be honest."

                    Comment


                    • #85
                      Originally posted by Kolibri View Post

                      (The AR-1 does not have a flex-shaft, but an ELA/AutoGyro/etc. type drive-shaft.)
                      True but IIRC the rigid drive on the AR-1 is able to accept a good amount of back-stick with the prerotator engaged. If I recall it’s from a combination of a spline-type joint (or two) on the shaft(s) plus universal joint(s). I recall Abid saying there’s no problem keeping the stick back but it did shorten the life of the u-joint to several hundred (500?) hours. But the end result is attributes I found acceptable and seeming to be better than the fixed systems.

                      /Ed

                      Comment


                      • #86
                        Hi just found this thread and in particular the comments around the operation of the BRAKE/FLIGHT switch and the effect on trim or rotor brake whilst in flight. I’ve no idea on this accident and if this is even relevant to it but I thought I’d share my own experiences, for context I’m a UK gyroplane instructor.

                        Around 2 years ago I made a flight with a reasonably experienced gyroplane pilot who had recently purchased a Calidus. I say reasonably, he had circa 500hours from 15 years of flying one. He had just over 10 hours in the Calidus and just wanted someone in the aircraft to act as safety pilot / critique / help him with the navigation / local procedures on a flight to a new airfield. Fairly unremarkable stuff.

                        During the climb out from the airfield I was generally aware that our rate of climb was poor and I commented to the pilot, with an additional comment about airspeed verse Vy, we were quite fast.

                        Some seconds later, certainly less than minute the situation hadn’t improved significantly, we were still slightly fast and now it wasn’t only the rate of climb that was on my mind but our overall height. Things weren’t so dramatic as needing to get involved just yet but I did say to the pilot, that he needed to remedy the situation PDQ.

                        This time the pilot replied that he had been trying to fix things but the aircraft just wouldn’t climb. I checked the throttle position from the rear seat and confirmed that we had full throttle and said to him I suppose a little despairingly “Set pitch attitude to give the airspeed we want and trim…” to which he replied that he couldn’t. At this point I said “I have control”.

                        Faithful to my instruction to him and with a 15-20mph higher airspeed than required I pulled some back stick to give a high nose up attitude. On reflection, with that initial irritation that a pilot whom I had a level of expectation with couldn’t climb accurately, my stick force was probably higher than normal and with the pitch attitude set to that I wanted I trimmed. Now my trim process is usually a couple of second rearwards trim at a time with aircraft operating normally, i.e. to account for student errors, laziness or even leaky pneumatics etc. It was after that initial trimming that I remember thinking “Wow this aircraft is trimmed miles away! (heavily nose down).” Of course with the conversation that had taken place before it simply re-enforced a view that the pilot was rusty and couldn’t climb away accurately and now my thinking that his problem was he just hadn’t trimmed the aircraft.

                        By now we are crosswind and our intention was to depart the circuit to enroute broadly in that direction. With the pitch attitude as I wanted I set about trimming but with the thinking that it was so far out it would need 5-6 seconds of rearwards trim. As I was trimming the stick force became very large indeed to the point that it was not manageable with one hand anymore and even with 2 hands with the more relaxed and unplanned way I had been sat it wasn’t easy.

                        I am confused to be honest and of course with hindsight I could have just tried to reverse the inputs but I guess that’s confusion for you.

                        Back in the aircraft I said to the pilot that something wasn’t correct and I would continue flying the aircraft if he could look and see if there was anything obviously wrong, bearing temperature perhaps?

                        I made a PAN call and turned downwind in the circuit with the intention to get back on the ground but at this point I have to say I was struggling with the stick forces, even two handed. We were circa 5-600ft and I was not clear on the issue, it felt like a control restriction and not being clear on how that would develop I thought it would be sensible to get on the ground sooner than later and I cut the throttle to idle and intended to land in a field. At about 2-3ft the front seat now passenger exclaimed “I’ve found it” and flicked the BRAKE/FLIGHT switch to FLIGHT and the high control forces went away and we climbed away.

                        In our subsequent discussion it became apparent how this had happened. The runway in use made a reasonable taxi necessary and on reaching the hold board the pilot was going to line up when I stopped him, suggesting it would be better to wait for landing traffic as we would be less rushed. However he had already flicked the switch to FLIGHT. Then when we actually lined up he went through his lining up process mechanically and flicked the BRAKE/FLIGHT switch, except this time it was now back in the BRAKE position. Of course in the Calidus that is not an easy spot from the rear.

                        In summary, the aircraft will pre-rotate in this state, and will fly, except that when you trim you are now forcing the trim piston up into the rotor brake and stick forces are too high to maintain controlled flight for very long, worse there is a lot of confusion around what the problem actually is. I articulated the above to UK hierarchy at the time not being a Calidus owner and not flying one often I’ve no idea how that has been feed back and actually in the UK the process of wider communication has room for improvement.


                        As it relates to comments on this thread you would not easily over come the stick forces involved and actually it is so un-natural that you would not feel comfortable doing so because unless you know what the issue is (and in which case the remedy is very easy you just flick a switch) but without knowing you would not want to remain airborne. Closing the throttle and landing is the best option, which then depends on where you are flying to how that works out.

                        The other element of discussion seems to centre on the Teleflex control cables which can be pinched but that is a focus for trained maintenance personal. I think one snag could be loose articles restricting at this point (I have a picture but cant upload its basically the point underneath the seat of the Cavalon where the control cable runs). That would seem a more likely snag than the control cable.


                        Comment


                        • #87
                          When I started to fly German gyros back in 2009 I (it's a habit) used to study them for possible inflight problems, how to avoid them and how to sort them out. The question "what if this selector is turned to BRAKE in flight appeared in the first month of getting familiar with this brand of gyros (I met ELA years later). I've siimply tried this in flight - unpleasant but nothing serious if you know how this happens (praemontis praemunitis). After that I use to show how it goes to each my student. At least 2 or 3 times it happened in real when student for unknown reason really turned it to BRAKE. And they always don't agree that they did this! The proof is usually easy since I also use to have an action camera installed so controls and instrument panel are seen. This is very useful for student to review his/her flight soon after landing. Students were very confused when they saw them switching FLIGHT to BRAKE, usually this happened on a take-off roll.
                          One more tip for a Calidus: I'm 176 cm man and I found out that it's more comfort for instructor to sit in the back seat a bit higher. Thus I have a 8-10 cm custom made pad under me while flying back seat. This makes possible to see most of instrument panel. And I use to look at airspeed indicator mirrored image on the canopy glass - it is seen clear enough for most days.
                          Alex Lameko
                          Russian gyroforum
                          Visit my collection of gyro videos

                          Comment


                          • #88
                            Thank you for sharing your experience Phil Bennett.

                            It is a good flight instructor story well told.

                            I did not know you could pre-rotate with it in the "brake" mode.

                            It is nice to know that the Calidus was still flyable with it in the "brake" mode despite adding to the pressure in an effort to trim her out.
                            Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

                            Comment


                            • #89
                              I like the way you think Alex.

                              It had not occurred to me that someone might try to fly in the brake mode.

                              I will add that procedure to my syllabus.
                              Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

                              Comment


                              • #90
                                I have not tried to fly a Cavalon in the brake mode. I suspect it would not be a problem....Because the trim force is not very hard to overcome.
                                Well, now we know better.

                                I'm not surprised to read from Phil's account that it was indeed a physically difficult and mentally confusing event:


                                As I was trimming the stick force became very large indeed to the point that it was not manageable with one hand anymore and even with 2 hands with the more relaxed and unplanned way I had been sat it wasn’t easy.

                                I made a PAN call and turned downwind in the circuit with the intention to get back on the ground but at this point I have to say I was struggling with the stick forces, even two handed.

                                In summary, the aircraft will pre-rotate in this state, and will fly, except that when you trim you are now forcing the trim piston up into the rotor brake and stick forces are too high to maintain controlled flight for very long, worse there is a lot of confusion around what the problem actually is.

                                As it relates to comments on this thread you would not easily over come the stick forces involved and actually it is so un-natural that you would not feel comfortable doing so because unless you know what the issue is...but without knowing you would not want to remain airborne.
                                Phil, this was very illuminating, thank you for posting about your experience.

                                Do you recall what rotor rpms were? How much degradation due to rotor braking?



                                __________
                                The wisdom of AutoGyro's FLIGHT/BRAKE common switch is by now openly suspect.

                                It reminds me of this Far Side cartoon:

                                Click image for larger version  Name:	wings stay on, wings fall off.jpg Views:	1 Size:	66.5 KB ID:	1141748






                                ___________
                                The other element of discussion seems to centre on the Teleflex control cables which can be pinched but that is a focus for trained maintenance personal. I think one snag could be loose articles restricting at this point (I have a picture but cant upload its basically the point underneath the seat of the Cavalon where the control cable runs). That would seem a more likely snag than the control cable.
                                Good point to consider.

                                It's still not been confirmed if N198LT had previous tip-over or rotor strike damage which may have compromised the cables.
                                Perhaps the NTSB will be able to inspect them. Previously frayed wires inside the sheath, for example, should be discernible.

                                Regards,
                                Kolibri

                                PP - ASEL complex (C172RG, Piper 180, C206, RV-7A), SP - Gyro (Calidus, RAF, Sport Copter II, M912), soloed in gliders

                                "
                                When an honest but mistaken man learns of his error, he either ceases to be mistaken -- or he ceases to be honest."

                                Comment

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