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Chris Lord October 31, 2018

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  • #46
    Originally posted by Kolibri View Post
    It's an odd facet of the crash. My thinking about it is this:
    Since the impact caused a near instantaneous explosion and fire, the prop blades severing (without fire exposure) seems to have happened in the air.
    I don't see the likelihood of the prop blades fully striking either the power pole or the wires, which, to me, leaves the rotor blades as what sheared off the prop blades.
    We don't know what the rotor rpm was in those last seconds, so they could have been coning significantly.




    Perhaps, but that's what two or three witnesses reported seeing. Estimated altitude varied from 150-300' AGL.



    Well, you're nearly alone on that.



    Even if were turbo wastegate surging, Chris could have easily shut off the engine over the lakeshore and landed safely.
    If it were such surging, which I'm not convinced it was.

    Regards,
    Kolibri


    Agreed, a surging engine would not likely have been an uncontrollable event, particularly in Chris's hands. Also the words 'lean back' in his transmission would also be evidence of a control issue with an attempt to control the aircraft by weight shift, something that would not be necessary or even considered with an engine problem. Much more likely any surging was purposeful throttle input by the pilot to help control airspeed in an unstable situation in conjunction with trying to shift weight. When I had my loss of control in my MTO at about 700 feet, I was fortunately able to maintain the aircraft in a controlled glide to land with the stick fully back as far as it could go. Holding it in a normal position resulted in a sharp nose down pitch with little or no control of roll unless the stick was fully back as well. Fortunately I was in the pattern at a grass strip. Had I been anywhere else over a built up area I would not have had any possibility of pulling off a safe controlled landing. Possibly I could have tried to control altitude with throttle input, fortunately I did not need to try.

    Comment


    • #47
      Based on my experience flying a Cavalon it would seem unlikely to be able to manage the pitch by the passenger leaning further back.

      I had a friend have a stroke and he collapsed forward unable to control his body. It was much worse than just dead weight and was difficult to straighten him out. If someone was having a medical emergency and collapsed forward on the cyclic I might ask them to lean back and I might have difficulty controlling the aircraft. I know it would reduce my situational awareness.

      I have had a surging engine and it made the choice of landing zones difficult. I wondered if the engine would keep running or quit altogether.

      In my opinion an emergency landing in a gyroplane is not as simple as people make it out to be. As the ground rushes up to meet me I see things I didn't see from higher up.

      Wires have brought down a lot of rotorcraft.

      I am not suggesting I am as good a pilot as Chris; I am only sharing what I have learned from experience.

      I do not have enough information to know what happened and am not suggesting I do.

      I feel a little short of information to assume it was a control system failure.

      The maneuvering Chris was doing seems elaborate to me for a gyroplane with a control system failure.

      Radar contact was lost at nine hundred feet so we have to rely on witnesses for pre-impact track and speed. I would have a lot of trouble estimating the height and speed of a gyroplane.

      I don't know how tall the pole they hit was but it seems unlikely it was a hundred fifty to three hundred feet tall.
      Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

      Comment


      • #48
        Chris's "back, lean back" seems to me directed at his passenger who was somehow in the way.
        I didn't have the sense that it was for auxiliary pitch.


        Nobody is suggesting that mobile home park power poles are 150+ feet tall.

        However, if N198LT had somehow lost cyclic and pitch trim, the rotor would have dumped forward. Thus, the witnessed nosedive from 150' AGL.
        In the Cavalon, is there a common bracket, bolt, or part which if failed would have severed or catastrophically compromised cyclic authority and pitch trim?



        The maneuvering Chris was doing seems elaborate to me for a gyroplane with a control system failure.
        From the totality of witness reports, and in conjunction with the Mayday call, my sense of it is that the failure proceeded gradually at first, and then fully failed in the last seconds. I.e., for maybe 30-60 seconds he had some control, although it was decreasing.
        PP - ASEL complex (Piper 180, C206, RV-7A), SP - Gyro (Calidus, RAF, SC2), soloed in gliders; checkride soon

        Wasn't happy with my RAF's pitch instability, so I installed a Boyer H-Stab to my great satisfaction!

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

        Comment


        • #49
          Every gyroplane rotor control system I have seen has several points of failure that would severely compromise rotor control except for an overhead stick.

          A Cavalon is no exception.

          In my experience when a gyroplane is trimmed properly; it needs no rotor control input to fly straight and level at whatever airspeed is desired.

          A Cavalon is no exception and has a particularly good trim system.

          I take off without trim in a Cavalon and it does not nose dive (rotor dumped forward?) and flies with very little cyclic back pressure.

          The trim on a Cavalon is right at the top where the FAA reported things were still connected.
          Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

          Comment


          • #50
            FWIW; when I had my control failure, I was alone, and I had to pull the stick all the way back into the seat, possibly Chris had to do the same and the passenger was obstructing this effort. Of course the control mechanism does not use cables in the MTO, but with a failure of the pitch connection between the stick and the head at some point, I imagine the tendency to pitch down would be the same, and the instinctive attempt to correct it by pulling back on the stick would be the same. My ability to retain some control in my case was only because the horizontal control rod only partially came out of it's retaining bracket. The rear bolt holding it had become completely loose but was prevented from falling out completely by the lower part of the vertical mast.

            Comment


            • #51
              Originally posted by loftus View Post
              My ability to retain some control in my case was only because the horizontal control rod only partially came out of its retaining bracket. The rear bolt holding it had become completely loose but was prevented from falling out completely by the lower part of the vertical mast.
              I am curious what method was supposed to be in place to prevent that evidently critical bolt from coming loose.

              Comment


              • #52
                Originally posted by Tyger View Post

                I am curious what method was supposed to be in place to prevent that evidently critical bolt from coming loose.
                The bolt was supposed to be torqued during the build, I can't be sure that was done. That is the only requirement in the MTO build manual. The standard bolt is a hex drive with very little working room between the head and the base of the mast - which actually saved my life as it did not fall out completely. It was very difficult (impossible actually with my tools) to access and torque with standard tools. I replaced the bolt with a standard flat head bolt that was easy to tighten properly and I of course made sure it was torqued, The bolt had the head drilled and a safety wire to the frame as well.

                Comment


                • #53
                  Originally posted by loftus View Post

                  The bolt was supposed to be torqued during the build, I can't be sure that was done. That is the only requirement in the MTO build manual. The standard bolt is a hex drive with very little working room between the head and the base of the mast - which actually saved my life as it did not fall out completely. It was very difficult (impossible actually with my tools) to access and torque with standard tools. I replaced the bolt with a standard flat head bolt that was easy to tighten properly and I of course made sure it was torqued, The bolt had the head drilled and a safety wire to the frame as well.
                  It seems ludicrous that the only requirement for an essential bolt in something that vibrates as much as a gyro was a certain torque spec. Even had it been correctly torqued, vibration could be expected to loosen it eventually, absent some other method of keeping it from spinning. You're smart to wire in a new, drilled bolt.

                  Comment


                  • #54
                    The FAA way to do thing (AC43.13-1B) is if it pivots it needs a secondary form of retention. Safety wire or a castellated nut and a cotter pin are preferred because these methods are easy to inspect.

                    "Do not use self-locking nuts on parts subject to rotation."
                    Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

                    Comment


                    • #55
                      On controlling the aircraft in the pitch axis with throttle: Pilots with failed control systems do try it (who wouldn't?). AFAIK it has never worked. One example from years ago is LeRoy Hardee, who had a failure of his Brock-style joystock system while flying a passenger in a tandem Snowbird. Witnesses described throttle "cycling," as I recall the story.

                      A "graveyard spiral" as such is most unlikely in a rotorcraft. FW planes generally have spiral instability to some extent: In a turn, the outside wing goes faster, lifts its side of the plane and tightens the bank in an uncommanded way. Hence the need for "high sticking" FW craft in turns. Our flapping hinges eliminate this issue -- or, really, turn it into extra rotor flapping in a turn. No need to "high stick" a gyro to hold a given bank angle.

                      Comment


                      • #56
                        As I tried to clarify, "graveyard spiral" was just my rough visual metaphor for what the witness described (going round and round, and descending).
                        It's reassuring, however, that gyros are not prone to the phenomenon.


                        ________
                        In my experience when a gyroplane is trimmed properly; it needs no rotor control input to fly straight and level at whatever airspeed is desired.
                        Well, yes, Vance, that's what trim is for.
                        But the scenario I'm musing about assumes not only compromised pitch authority, but possibly trim as well.



                        I take off without trim in a Cavalon and it does not nose dive (rotor dumped forward?) and flies with very little cyclic back pressure.
                        At something near cruise AS, I can see how rotor blowback effect can negate the need for trim (at that particular AS).

                        But N198LT was not flying anywhere near cruise AS in its last 20 seconds.
                        In fact, witnesses reported very little forward speed. Winds were light. Thus, AS was low.

                        We all know that slow flight requires considerable back cyclic (or nose-up trim) in comparison to cruise.
                        If control authority were compromised at a low AS, it would present a real challenge.
                        Trim may not provide enough compensation.

                        I don't know the strength and length of arm of the Cavalon pitch trim cylinder rod.
                        Would it be sufficient to, for example, pull back the torque tube for a vertical descent? Or is it less powerful than that?
                        I'm trying to explore the limits of what Cavalon pitch trim could do in the event of loss of cyclic.


                        _______
                        loftus, thanks for your description of that personal incident.
                        I'm wondering if something like that happened onboard N198LT.


                        _______
                        It would helpful if pictures of the Cavalon control system were posted, especially of the lower area.

                        Regards,
                        Kolibri
                        PP - ASEL complex (Piper 180, C206, RV-7A), SP - Gyro (Calidus, RAF, SC2), soloed in gliders; checkride soon

                        Wasn't happy with my RAF's pitch instability, so I installed a Boyer H-Stab to my great satisfaction!

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

                        Comment


                        • #57
                          Originally posted by Kolibri View Post
                          As I tried to clarify, "graveyard spiral" was just my rough visual metaphor for what the witness described (going round and round, and descending).
                          It's reassuring, however, that gyros are not prone to the phenomenon.


                          ________

                          Well, yes, Vance, that's what trim is for.
                          But the scenario I'm musing about assumes not only compromised pitch authority, but possibly trim as well.


                          We all know that slow flight requires considerable back cyclic (or nose-up trim) in comparison to cruise.
                          If control authority were compromised at a low AS, it would present a real challenge.
                          Trim may not provide enough compensation.

                          I don't know the strength and length of arm of the Cavalon pitch trim cylinder rod.
                          Would it be sufficient to, for example, pull back the torque tube for a vertical descent? Or is it less powerful than that?
                          I'm trying to explore the limits of what Cavalon pitch trim could do in the event of loss of cyclic.[/COLOR]

                          _______
                          loftus, thanks for your description of that personal incident.
                          I'm wondering if something like that happened onboard N198LT.


                          _______
                          It would helpful if pictures of the Cavalon control system were posted, especially of the lower area.

                          Regards,
                          Kolibri
                          That is why I mentioned the pneumatic trim was at the top where the FAA confirmed the controls were in place.

                          The Cavalons I have flown could be trimmed for a vertical descent.

                          Somehow Chris was able to go from near VNE to slow flight.

                          Pictures of nearly every part of the Cavalon are available on line from AutoGyro GMBH.
                          Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

                          Comment


                          • #58
                            Pictures of nearly every part of the Cavalon are available on line from AutoGyro GMBH.
                            Not that I've been able to so far find. Please post some links, thanks.


                            That is why I mentioned the pneumatic trim was at the top where the FAA confirmed the controls were in place.
                            I'm not talking about the pitch trim arm connecting to the torque tube (and rotor brake).
                            I've been wondering about something in the cabin.

                            Question: In "Brake" mode, is the pitch trim cylinder pressurized to force the rod up, thus moving the rotorhead forward and activating the rotor brake?
                            Or, does "Brake" mode completely depressurize the pitch trim cylinder, and the rotorhead falls forward all on its own?

                            Regards,
                            Kolibri



                            ______
                            5 Dec 2018 UPDATE: Due to forum snags, new posts sometimes do not go through, but I'm able to edit previous ones.

                            I researched my above question, and found the answer in an AutoGyro maintenance manual.
                            When switched to "BRAKE" the pneumatic trim is pressurized, but with reverse effect:


                            63-51-00 Rotor Brake System

                            The rotor brake system consists of a brake pad mounted to a bracket which is hinged to the rotor head
                            bridge. With the pneumatic mode selector in BRAKE position the operation of the pneumatic trim
                            actuator is reversed so that increased pressure causes the actuator to push the rotor head up (or
                            level) and presses a brake pad against the rotor head disc.
                            In order to increase brake pressure,
                            move the 4-way trim switch to aft. Note that this action will also push the control stick forward. At full brake
                            pressure the control stick will be maintained in its full forward position.
                            IF . . . the pneumatic mode selector in N198LT somehow failed and went into "BRAKE" mode in flight,
                            then Chris would have involuntarily lost altitude from a flattening rotor disk.

                            More alarming (and confusing) would have been decaying rotor rpm from the engaged rotor brake.

                            This may explain the odd power fluctuations heard in the Mayday call.
                            Chris may have been trying to maintain altitude and rotor rpm via the throttle.

                            Those who may be skeptical of my "trim runaway" theory may be interested to learn that AutoGyro's
                            latest Cavalon POH is version 3.1, announced on 5 November 2018 (several days after the crash).

                            SECTION 3 - EMERGENCY PROCEDURES has some apparently new material (my emphasis is in bold):


                            SECTION 3 - EMERGENCY PROCEDURES
                            3.8.4 Trim runaway


                            Failure of a trim selector switch or pneumatic valve may result in trim runaway (where the
                            trim system runs to one extreme and pushes the control stick accordingly).
                            Although the
                            average pilot is able to resist the out-of-trim stick force and continue to fly the aircraft it may
                            be possible to reduce the stick load by intervention:

                            (i) High forward stick load required to prevent aircraft nose rising (this will be
                            coincident with a high air-pressure reading) – briefly turn the Flight/Brake selector
                            to “Brake” to deplete system air pressure. If the air compressor is heard to start
                            and the pressure rises again then pull the circuit-breaker marked “Comp” to stop
                            the compressor. Repeat the brief selection of “Brake” to deplete system air
                            pressure as required.

                            (ii) High aft stick load required to prevent aircraft diving (this will be coincident with
                            low or zero air pressure) – check “Comp” circuit breaker, if activated push to reset
                            then try to trim aircraft nose-up. If unsuccessful then continue to expedited
                            landing. Note: reset the circuit-breaker once only.
                            Not a word was mentioned in scenario (ii) about the rotor brake engaging.

                            Also new in this Cavlon POH version 3.1 SECTION 3 - EMERGENCY PROCEDURES is:

                            3.9 Pitch oscillation recovery
                            3.10 Vibration
                            All three of these items may have been relevant for N198LT.
                            I find this very interesting.

                            Regards,
                            Kolibri


                            PP - ASEL complex (Piper 180, C206, RV-7A), SP - Gyro (Calidus, RAF, SC2), soloed in gliders; checkride soon

                            Wasn't happy with my RAF's pitch instability, so I installed a Boyer H-Stab to my great satisfaction!

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

                            Comment


                            • #59
                              My recollection is neither.

                              There is an air cylinder that pushes the rotor head forward and a rotor brake cylinder that are activated in the brake mode.

                              When the switch is made from brake to flight it dumps the pressure in the system.

                              There is a different cylinder that pulls the head back for trim in the flight mode when pressure is added to the system.

                              It has been more than a year since the last time I flew a Cavalon so hopefully someone else will confirm or correct my recollection.

                              I don't care for pneumatic trim systems.
                              Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

                              Comment


                              • #60
                                Originally posted by Vance View Post
                                My recollection is neither.

                                There is an air cylinder that pushes the rotor head forward and a rotor brake cylinder that are activated in the brake mode.

                                When the switch is made from brake to flight it dumps the pressure in the system.

                                There is a different cylinder that pulls the head back for trim in the flight mode when pressure is added to the system.

                                It has been more than a year since the last time I flew a Cavalon so hopefully someone else will confirm or correct my recollection.

                                I don't care for pneumatic trim systems.
                                There is a pneumatic cylinder that trims the roll axis and a larger cylinder that provides for pitch trim, which also engages the rotor brake and pushes the head forward in brake mode.

                                Details can be found in the Cavalon Maintenance Manual which can be downloaded here:

                                https://www.manualslib.com/manual/11...o-Cavalon.html

                                Comment

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