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Chris Lord October 31, 2018

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  • #91
    Minimum flight rotor rpms are listed in both gyros' POHs. Pilots should consult those figures.
    Sink will be experienced below those RRPMs.
    In my opinion.
    PP - ASEL complex (C172RG, Piper 180, C206, RV-7A), SP - Gyro (Calidus, RAF, SC2), 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


    • #92
      Originally posted by Kolibri View Post
      Thanks for your thoughts on this point, Phil. While you were descending in the pattern for a PAN landing, airspeed was sufficient to maintain flight RRPM.
      What I'm wondering here in relation to N198LT was if they had descended from 900 feet to about 150 feet and then found themselves over the trailer park.
      Chris may have been naturally reluctant to then add power with such strong nose-down pitch. As you explained, "
      any small lapse or relaxation on the stick will see the aircraft bunt."
      This trepidation could have allowed his airspeed to decrease, thus decaying RRPM and resulting in that plummet.

      Regards,
      Kolibri
      Kolibri please help me to understand the relationship you feel there is between airspeed and rotor rpm that you feel could cause Chris Lord to plummet due to insufficient rotor rpm caused by low indicated airspeed.

      The Cavalons I have flown would not plummet because of a lack of rotor rpm even in a prolonged vertical descent at zero indicated airspeed.
      Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

      Comment


      • #93
        The Cavalons I have flown would not plummet because of a lack of rotor rpm even in a prolonged vertical descent at zero indicated airspeed.
        You're assuming normal cyclic control of the rotorhead, and the full availability of normal angle of attack range.
        In this case of N198LT, I am not assuming that.

        Rather, I'm postulating a full (or nearly so) forward rotor because of (air pressure reversed) aft trim applied in BRAKE mode.
        Phil just described how extremely difficult it was to not bunt over, even while using both hands to pull back.
        Fortunately for him and his student, they'd never climbed above pattern altitude, and they were able to descend at the rate forced upon them by the malfunction.
        Had the student not switched to FLIGHT at 2-3 feet AGL over the runway, Phil may have difficulty flaring and could have wheelbarrowed in. (Phil, comments on that?)

        Chris, however, seemed experience his trouble at 900-1000 feet, and not next to a runway.
        He was probably trying to finesse airspeed, rrpm, and altitude into a manageable totality, while quickly identifying possible landing spots.
        Not having full aft stick (while the rotor brake was simultaneously decaying rrpm) would have been a very tricky problem.


        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 before a large fireball was seen.


        The "with very little airspeed" I read as Chris flying with reduced power at 300 AGL to avoid bunting over from the flattened rotor disk.

        In my opinion, with what we so far know, he ran out of normal flight rrpm ("
        about 150 feet the nose of the aircraft dropped")
        and no vertical descent was possible for him because of the very rigid forward rotor attitude.


        _____
        Phil, in your Calidus incident, after you'd input (reversed) aft trim and your disk was flattened, could you have hauled back on the stick
        sufficiently for a vertical descent? I don't infer that possibility from your account.

        Regards,
        Kolibri

        PP - ASEL complex (C172RG, Piper 180, C206, RV-7A), SP - Gyro (Calidus, RAF, SC2), 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


        • #94
          Originally posted by Kolibri View Post
          You're assuming normal cyclic control of the rotorhead, and the full availability of normal angle of attack range.
          In this case of N198LT, I am not assuming that.

          Rather, I'm postulating a full (or nearly so) forward rotor because of (air pressure reversed) aft trim applied in BRAKE mode.
          Phil just described how extremely difficult it was to not bunt over, even while using both hands to pull back.
          Fortunately for him and his student, they'd never climbed above pattern altitude, and they were able to descend at the rate forced upon them by the malfunction.
          Had the student not switched to FLIGHT at 2-3 feet AGL over the runway, Phil may have difficulty flaring and could have wheelbarrowed in. (Phil, comments on that?)

          Chris, however, seemed experience his trouble at 900-1000 feet, and not next to a runway.
          He was probably trying to finesse airspeed, rrpm, and altitude into a manageable totality, while quickly identifying possible landing spots.
          Not having full aft stick (while the rotor brake was simultaneously decaying rrpm) would have been a very tricky problem.




          The "with very little airspeed" I read as Chris flying with reduced power at 300 AGL to avoid bunting over from the flattened rotor disk.

          In my opinion, with what we so far know, he ran out of normal flight rrpm ("
          about 150 feet the nose of the aircraft dropped")
          and no vertical descent was possible for him because of the very rigid forward rotor attitude.


          _____
          Phil, in your Calidus incident, after you'd input (reversed) aft trim and your disk was flattened, could you have hauled back on the stick
          sufficiently for a vertical descent? I don't infer that possibility from your account.

          Regards,
          Kolibri
          I am not assuming anything Kolibri.

          I am suggesting that there is not the relationship between indicated airspeed and rotor rpm that you appear to imagine Kolibri.

          Originally posted by Kolibri View Post
          Thanks for your thoughts on this point, Phil. While you were descending in the pattern for a PAN landing, airspeed was sufficient to maintain flight RRPM.
          What I'm wondering here in relation to N198LT was if they had descended from 900 feet to about 150 feet and then found themselves over the trailer park.
          Chris may have been naturally reluctant to then add power with such strong nose-down pitch. As you explained, "
          any small lapse or relaxation on the stick will see the aircraft bunt."
          This trepidation could have allowed his airspeed to decrease, thus decaying RRPM and resulting in that plummet.
          Regards,
          Kolibri
          In all the gyroplanes I have flown the rotor rpm takes care of itself once I am airborne and unless I am performing a flight maneuver that unloads the rotor; the rotor will maintain flight rpm.

          In the Cavalons I have flown lowering the nose (cyclic forward) is how to ask her to go faster.

          If I was fighting to keep the cyclic from going full forward as you postulate I don't know how I would slow down.

          In my opinion I would not slow down by reducing power.

          I reduce throttle to ask the Cavalon to descend and increase power to ask her to ascend.
          Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

          Comment


          • #95
            In all the gyroplanes I have flown the rotor rpm takes care of itself once I am airborne and unless I am performing a flight maneuver that unloads the rotor;
            the rotor will maintain flight rpm.
            Sure, and if one has normal control of the rotor disc angle of attack, rrpm can be maintained in level flight with steady power. We all know this.

            However, I don't believe that N198LT was flying normally in its last moments.
            If the rotor disc had been flattened out (or nearly so) as I suspect, then level flight was very difficult at best, if not impossible.

            I'd say that N198LT was in an involuntary descent, as Chris certainly wouldn't have have chosen to pleasure fly below legal minimum altitude over congestion.
            While N198LT was in descent, flight rrpm was maintained (even with rotor braking), but at some point Chris could not safely descend further.
            He may have hesitated at that altitude (i.e., 150 feet) by hauling back on the stick, and unloaded the rotor beyond the ability to restart it.


            If I was fighting to keep the cyclic from going full forward as you postulate I don't know how I would slow down.

            In my opinion I would not slow down by reducing power.
            If the rotorhead was firmly forward as Phil described because of the trim reversal, what else is left but to reduce power?
            That's what Phil had to do.

            Regards,
            Kolibri


            PP - ASEL complex (C172RG, Piper 180, C206, RV-7A), SP - Gyro (Calidus, RAF, SC2), 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


            • #96
              Originally posted by Kolibri View Post
              Sure, and if one has normal control of the rotor disc angle of attack, rrpm can be maintained in level flight with steady power. We all know this.

              However, I don't believe that N198LT was flying normally in its last moments.
              If the rotor disc had been flattened out as I suspect, then level flight was very difficult at best, if not impossible.

              I'd say that N198LT was in an involuntary descent, as Chris certainly wouldn't have have chosen to pleasure fly below legal minimum altitude over congestion.
              While N198LT was in descent, flight rrpm was maintained (even with rotor braking), but at some point Chris could not safely descend further.
              He may have hesitated at that altitude (i.e., 150 feet) by hauling back on the stick, and unloaded the rotor beyond the ability to restart it.



              If the rotorhead was firmly forward as Phil described because of the trim reversal, what else is left but to reduce power?
              That's what Phil had to do.

              Regards,
              Kolibri


              In a Cavalon Rotor RPM takes care of itself unless I do something to unload the rotor. I do not need to do anything to maintain Rotor RPM.

              In a Cavalon "hauling back on the stick" (aft cyclic?) in a descent will load the rotor and increase rotor RPM rather than decrease it.

              If the cyclic was trimmed full forward as you postulate because somehow the trim inputs were reversed and there was so much pressure in the system that the two of them could not manage enough back stick to stay below VNE and Chris had not figured out how to correct the problem he would have flown into the ground at high speed. In my opinion the throttle would only control the rate of descent and not the indicated air speed or rotor RPM in your scenario.
              Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

              Comment


              • #97
                Originally posted by HighAltitude View Post
                I just completed my MTO 2017 build on Monday and I took the time to run through some scenarios:

                1. You cannot pre rotate in brake mode. There is a micro switch on the control shaft that prevents the prerotator from engaging until you move the stick back. The prerotator only engages when the stick is within range. Too far back or forward and prerotation stops. There is also a pressure switch to prevent prerotation with any pressure in the system. You must have the stick in the correct position AND no pressure in the system so you cannot prerotate in brake mode. You can learn it with engine off and key on. I don't understand the comment that it is not understood and involves guessing.


                2. Switching to brake on takeoff roll. The pressure switch is set at about 2 bars. It will allow pre rotation at 2 bars or less but at that low pressure there is no braking pressure and the stick is easily pulled back. This is likely what happened to Phil. The PIC may have put it in brake mode but didn't build pressure. If he was trimming on climb out, it was poor technique.

                2. Nothing happens immediately and suddenly when you engage brake mode in flight. The "Brake" position is really "Brake Armed". You have to take a second action to apply the brake. Rather than asking "Can you prerotate in brake mode?" the question should be "If a student engaged brake mode in flight, what would happen?". You do not fall out of the sky, nor does the stick go full forward with maximum force. Absolutely nothing happens. You would never know it was in brake mode if you never needed aft trim during your flight. Until you take the second step and build pressure use the trim switch, you wouldn't know the switch was in brake mode. If and when you trim aft in flight you will start to feel forward stick pressure when trimming aft. Again, with the engine off, it can easily be simulated. I imagine that if I pulsed aft trim in flight and the result was more forward pressure instead of less, I would notice it and probably bump the trim again. It would get slightly heavier and responding the opposite of what I intended so I imagine that I would try forward trim. I hope I would not panic and hold the aft trim button until stick forces required two hands but I can see how that scenario would cause confusion. However, a student could/should be taught not to mess with any trims during take off. Level off and then set trim. I will practice today in the hanger with engine off by switching to brake mode and then applying aft trim to get a feel for it and practice switching back to flight mode to feel the instant release of forward stick forces.

                I have a brand new MTO sitting here that I know very well having just built it so if anyone wants me to test other scenarios that I may have not covered above, I would be happy to run through them in an effort to keep us all safer. I encourage everyone with an autogyro to sit in the seat, flip on power without starting the engine, and run through the scenarios that I did. I have a much better understanding of what to expect. We are all here to learn and help each other.
                I'm sorry but this post is both confused, misleading and ultimately contradictory.

                You absolutely CAN pre-rotate in brake mode and you say so yourself having told everyone in point 1 that you can't! That is misleading, in the context of what we are trying to explain dangerous and proves the point I was trying to make initially. People are confused on the issue.

                SO TO BE CLEAR YOU CAN PRE-ROTATE IN BRAKE MODE.

                The point I was making had nothing to do with the stick position - and therefore the micro switch has no effect on the issue I was describing.

                Your own point 2 contradicts your point 1.

                Regards point 3. Is nothing about selecting the BRAKE mode in flight and everything to do with the fact you think you are in FLIGHT mode because the switch has been selected incorrectly from take off.

                The confusion comes like this....

                You have just built a brand new MTO 2017 and at some point you perhaps do some flying with an instructor or maybe you read these forums. The question is made about the BRAKE / FLIGHT switch and the answer is given "no you can not pre-rotate in brake mode". So now for ever and a day you are flying around in the belief that you can not do what you absolutely can do! So when it happens why do you look? You didn't even think it could happen never mind what the function of it happening actually are!!

                YOU CAN PRE-ROTATE in BRAKE mode. 100% I've been sat in an aircraft that has done just that. Am I dumb I didn't figure it out in the air? Perhaps. Was that where my thinking was? No because when I did a check ride for the aircraft it was never mentioned. The POH didn't mention and in my case [perhaps in this accident too??] I was a passenger until it got too much for the pilot flying. So you get handed a poor situation. Yes you can fix as you describe by simply dumping trim pressure BUT that is not what your brain is telling you is wrong. You expectation is that it is something else causing an issue and you want to get on the ground. That working out well depends on where and how you fly i.e. airmanship not flying over congested areas etc.

                Once again to be clear. Pilots are generally casual with the BRAKE/FLIGHT switch. In so far that they are happy to switch from one mode to the next without it being part of a planned "checklist" style action or point. Indeed you can find YouTube footage of the accident pilot and his use of this switch and it is clear that it is not part of a lining up or departure fixed process.

                The issue I had was [in my opinion] was caused because the pilot had flicked modes prior to lining up, got delayed and went into "auto-pilot" and flicked the switch again without actually reading or focused on what he was doing. With system pressure low - because it is very common with many Auto-Gyro Calidus and Calavon pilots to relieve stick forces to trim fully forward [i.e. dump any rearward trim pressure] once they go to FLIGHT mode. The problem is if distracted and they end up back in BRAKE mode you can pre-rotate.

                Is it a problem? Well with good awareness arguably no more than having retractable undercarriage. BUT like all systems it is good to understand them and people in general believe you can not do something I know [and the system knows] is possible. Worse in a Cavalon both the switch and the pressure gauge are located in a position where the leg covers both so neither are visible with a casual scan.

                Do I think it is relevant to the accident? Whilst I do not know what has caused the accident and will wait for the report I do feel it has the potential to have been a factor and I highlight to you guys here because of the confusion over what happens etc in the scenario.

                Ultimately aircraft do not end in a fatal accident with experienced crew without reason and if you look at the time from take off to accident then something went wrong that wasn't engine related if you read the interim NTSB report so this is one possible control issue, which due to the unknown nature and my experience when it happened the only thing that stopped us from a similar situation was we were not flying over wires or a congested area. At 100ft AGL we still had not figured out our issues and had power lines been in our path we would have possibly hit them too.

                Regards Rotor RPM as you all may know the rotor is in auto rotation and so RRPM is a function of loading. I closed the throttle in order to descend and maintain best glide speed and keep the disc loaded. Vance has explained the point well. I have a YouTube set of videos on gyroplane technique under my flying school name The Gyrocopter Flying Club for general flying stuff.

                Any issue I would have had in the landing phase - had it come to that - would have been the fact it would have been a downwind landing and in a field. Turns were not going to be accurate and we had few options with the initial height. It is likely had we had to land the aircraft may have been damaged but I was confident we would likely have walked away. However in the grand scheme I was happy to take that given the situation moments before.

                Please don't get confused with the issue. The BRAKE/FLIGHT mode is not something that causes RRPM to decay because of the mode being BRAKE (other than if you genuinely do bunt and then its low g and not the rotor brake that is causal). Stick force is the issue and the fact the aircraft is in a state that has maximum forward stick and you are not only working as if there was no trimmer but also against the pneumatic system pressure forcing it the other way. All this while stressed and trying to figure what is happening. Its ok for a minute but as you get tired the stress increases for obvious reasons.

                Ultimately regardless of its application to this accident it is worth knowing - fore warned etc.

                Comment


                • #98
                  Vance, you're the one repeatedly mentioning excessive speed and Vne, not me.
                  As I've consistently written, Chris's issue was trying to maintain altitude, and his speeds were not reported to be high.
                  He was not witnessed to have dived into the ground at anywhere near Vne.

                  While N198LT was in descent, flight rrpm was maintained (even with rotor braking), but at some point Chris could not safely descend further.
                  He may have hesitated at that altitude (i.e., 150 feet) by hauling back on the stick, and unloaded the rotor beyond the ability to restart it.

                  In a Cavalon "hauling back on the stick" (aft cyclic?) in a descent will load the rotor and increase rotor RPM rather than decrease it.

                  Yes, but only a little bit, and only momentarily.
                  The context of my description was that he "may have hesitated at that altitude" -- meaning somewhat arrested his descent, thus slowing his airspeed.
                  That would have unloaded his rotor, perhaps critically.


                  If the cyclic was trimmed full forward as you postulate because somehow the trim inputs were reversed and there was so much pressure in the system that the two of them could not manage enough back stick to stay below VNE and Chris had not figured out how to correct the problem he would have flown into the ground at high speed.
                  I disagree. His involuntary descent did not have to reach anywhere near Vne.
                  A control-induced descent into terrain could happen at many angles and speeds.
                  For example, one could mimic a locked cyclic at any descent angle, and fly it into the ground at any 50mph or Vne or anything in between.
                  The Cavalon which Phil described here nearly did so at Vg.


                  In my opinion the throttle would only control the rate of descent and not the indicated air speed or rotor RPM in your scenario.
                  Throttle does not affect airspeed? Never heard that one before.


                  ______
                  Phil, thanks for your continued comments about all this.
                  Your experience may have been eerily similar to that of N198LT.
                  It is good for AutoGyro owners to be aware this issue, which can be much more than merely "
                  disquieting".

                  Assuming your student had not at the last moment noticed the BRAKE position and switched to FLIGHT:
                  Do you think you could have rounded out and flared for a normal landing, or would you have pancaked in at Vg?
                  It seems more like the latter, but I don't want to misread your account.


                  ______
                  Agreed: In a descent, the rotor is loaded.
                  Agreed: Increasing angle of attack sufficiently for a vertical descent will load the rotor.
                  Agreed: In level flight with power, the rotor is loaded.

                  HOWEVER, where I think Chris got to was the rotor disk just below level flight AoA, and with the rotor brake actuated through reversed aft trim.
                  He had apparently slowed his descent with some aft cyclic, but hadn't enough to either vertically descend or mush in with power.

                  The witness report bears this out: very little airspeed at 300 feet, followed by a nose down fall at 150 feet.
                  Sounds like rotor rpm decay to me, via a combination of unloading the rotor while braking it.

                  Remember, with the rotorhead trimmed full forward, the brake is actuated.
                  Pulling back on the stick only forces the rear of the torque tube even harder against the rotor brake pad.

                  I think it an unwise design for a system to possibly allow the cyclic to act as a rotor brake.

                  Regards,
                  Kolibri
                  PP - ASEL complex (C172RG, Piper 180, C206, RV-7A), SP - Gyro (Calidus, RAF, SC2), 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


                  • #99
                    "Remember, with the rotorhead trimmed full forward, the brake is actuated.
                    Pulling back on the stick only forces the rear of the torque tube even harder against the rotor brake pad."


                    Kolibri, you are incorrect on the operation of the Autogyro rotor brake system! Pulling back on the stick simply moves the trim cylinder and removes the front brake pad from the system. Believe me, when we were doing tracking and balancing, I would have loved to be able to increase brake pressure by moving the stick. I don't take any comments on the net as gospel. I cross check for myself.

                    One brake pad is on the front of the rotor head and one is on the back. (Assuming that Chris was flying the current rotor head). Building pressure in the cylinder engages the rear pad and pushes the rotor forward to engage the front pad. Even the slightest rear pull on the stick pulls the rotor away front the front brake pad, cutting the brake force in half. Phil already verified through his experience that the rotor brake would not cause the RRPM to decay.


                    In the spirit of providing facts, I just did another test. I put it in brake mode and built pressure to 8 bars. Then I attached a scale to the stick and pulled it back. Anyone wanna guess what stick force is needed to oppose the rotor pressure? It's only adding 23 pounds to normal stick forces. (I say adding 23 pounds because someone here will undoubtedly try to tell me the forces in flight are different). DUH, but the full "runaway" trim adds 23 pounds to whatever normal in flight forces are there.

                    Any other tests that you guys want me to run?

                    Click image for larger version  Name:	stick pull 2.jpg Views:	4 Size:	812.0 KB ID:	1141786







                    Attached Files

                    Comment


                    • Originally posted by Kolibri View Post
                      Throttle does not affect airspeed? Never heard that one before.
                      As Langewiesche succinctly put it, "The stick is the speed control" and "The real elevator is your throttle".
                      "If you hold the stick in a certain position, forward or backward, you thereby force the airplane to fly at a certain speed; a correctly behaved airplane with then fly at that certain speed regardless of the amount of power used. If you feed it a lot of power, it will climb at that speed; if you feed it less power, it will fly level at that speed. If you cut the power entirely, it will glide at that speed."

                      Comment


                      • Originally posted by HighAltitude View Post
                        "Remember, with the rotorhead trimmed full forward, the brake is actuated.
                        Pulling back on the stick only forces the rear of the torque tube even harder against the rotor brake pad."


                        [COLOR=#000000]Kolibri, you are incorrect on the operation of the Autogyro rotor brake system! Pulling back on the stick simply moves the trim cylinder and removes the front brake pad from the system. Believe me, when we were doing tracking and balancing, I would have loved to be able to increase brake pressure by moving the stick. I don't take any comments on the net as gospel. I cross check for myself.

                        One brake pad is on the front of the rotor head and one is on the back. (Assuming that Chris was flying the current rotor head). Building pressure in the cylinder engages the rear pad and pushes the rotor forward to engage the front pad. Even the slightest rear pull on the stick pulls the rotor away front the front brake pad, cutting the brake force in half. Phil already verified through his experience that the rotor brake would not cause the RRPM to decay.


                        In the spirit of providing facts, I just did another test. I put it in brake mode and built pressure to 8 bars. Then I attached a scale to the stick and pulled it back. Anyone wanna guess what stick force is needed to oppose the rotor pressure? It's only adding 23 pounds to normal stick forces. (I say adding 23 pounds because someone here will undoubtedly try to tell me the forces in flight are different). DUH, but the full "runaway" trim adds 23 pounds to whatever normal in flight forces are there.
                        Thank you for taking the time and making the effort to quantify the force Tim.

                        I feel it is useful to quantify force required and facts are more useful than fantasy.

                        I am not able to see in the picture how far aft you were pulling the stick.

                        I was wondering if the force increased as the cyclic is moved full aft at full pressure.

                        Have fun my friend.

                        Hope to fly with you again.


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

                        Comment


                        • So we accept that you can pre-rotate with the aircraft in brake mode. Regarding stick force it would need to be rotors running, per g and of course in a Cavalon.

                          yes you could round out to land and the rotor brake element is not relevant.

                          Comment


                          • Originally posted by Kolibri View Post
                            Vance, you're the one repeatedly mentioning excessive speed and Vne, not me.
                            As I've consistently written, Chris's issue was trying to maintain altitude, and his speeds were not reported to be high.



                            I disagree. His involuntary descent did not have to reach anywhere near Vne.
                            A control-induced descent into terrain could happen at many angles and speeds.
                            For example, one could mimic a locked cyclic at any descent angle, and fly it into the ground at any 50mph or Vne or anything in between.
                            The Cavalon which Phil described here nearly did so at Vg.



                            Throttle does not affect airspeed? Never heard that one before.

                            Agreed: In a descent, the rotor is loaded.
                            Agreed: Increasing angle of attack sufficiently for a vertical descent will load the rotor.
                            Agreed: In level flight with power, the rotor is loaded.

                            HOWEVER, where I think Chris got to was the rotor disk just below level flight AoA, and with the rotor brake actuated through reversed aft trim.
                            He had apparently slowed his descent with some aft cyclic, but hadn't enough to either vertically descend or mush in with power.

                            The witness report bears this out: very little airspeed at 300 feet, followed by a nose down fall at 150 feet.
                            Sounds like rotor rpm decay to me, via a combination of unloading the rotor while braking it.

                            Remember, with the rotorhead trimmed full forward, the brake is actuated.
                            Pulling back on the stick only forces the rear of the torque tube even harder against the rotor brake pad.

                            I think it an unwise design for a system to possibly allow the cyclic to act as a rotor brake.

                            Regards,
                            Kolibri
                            In my opinion if the cyclic in a Cavalon was jammed full forward the aircraft would exceed VNE at any throttle setting.

                            In my opinion Kolibri's hypothesis that you can slow a Cavalon down with the cyclic jammed full forward by reducing the throttle is demonstrative of his lack of understanding of how a gyroplane flies.

                            I feel Kolibri's understanding of managing rotor rpm is sufficiently divergent to preclude communication.

                            I was reluctant to let this go because of a concern for this misinformation causing a safety issue.

                            I see now it gives Kolibri an opportunity to expand the misunderstandings as though it was an actual discussion.
                            Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

                            Comment


                            • As Langewiesche succinctly put it, "If you hold the stick in a certain position, forward or backward, you thereby force the airplane to fly at a certain speed; a correctly behaved airplane with then fly at that certain speed regardless of the amount of power used. If you feed it a lot of power, it will climb at that speed; if you feed it less power, it will fly level at that speed. If you cut the power entirely, it will glide at that speed."
                              Yep, true, Tyger, and I've read his book often.
                              Langewiesche is speaking of a
                              "correctly behaved airplane" which N198LT arguably was not.

                              If Chris could have remained level from a flattened (or nearly so) rotor disk (i.e., without sufficient AoA for level flight) by simply adding power, he'd have done so.
                              Conversely, he may have been more concerned with bunting over by adding power. (Phil mentioned this as his concern.)



                              ___________
                              Kolibri, you are incorrect on the operation of the Autogyro rotor brake system! Pulling back on the stick simply moves the trim cylinder and removes the front brake pad from the system. Believe me, when we were doing tracking and balancing, I would have loved to be able to increase brake pressure by moving the stick. I don't take any comments on the net as gospel. I cross check for myself.

                              One brake pad is on the front of the rotor head and one is on the back. (Assuming that Chris was flying the current rotor head). Building pressure in the cylinder engages the rear pad and pushes the rotor forward to engage the front pad. Even the slightest rear pull on the stick pulls the rotor away [from] the front brake pad, cutting the brake force in half.
                              High Altitude, I don't know if N198LT had the 1 or 2 pad rotor brake.
                              On the older single rear pad system, when the pitch trim arm moves up, it pushes the rotorhead forward while simultaneously engaging the rotor brake. This is indisputable.
                              It does so even in the 2 pad rotor brake (for the rear pad).



                              Phil already verified through his experience that the rotor brake would not cause the RRPM to decay.
                              Not quite. What he wrote was:

                              On the BRAKE/FLIGHT point. Rotor RPMs were not significantly affected but that would be an impression rather than an absolute recollection.
                              Since he checked the bearing rotor bearing temp (RBT) gauge, it seems he had at least a subconscious cue to reduced rotor rpm.

                              Ultimately the friction material and surface area are insignificant verse the aerodynamic forces at play.
                              And I agreed with this, as he was then in a sufficiently steep descent which would have maintained flight rrpm even with the brake engaged.
                              However, with what little aft cyclic one can muster, descent would have been retarded, and thus airspeed, and thus rrpm.
                              At that point, the engage rotor brake would have more noticeably slowed down rrpm.


                              In the spirit of providing facts, I just did another test. I put it in brake mode and built pressure to 8 bars. Then I attached a scale to the stick and pulled it back. Anyone wanna guess what stick force is needed to oppose the rotor pressure? It's only adding 23 pounds to normal stick forces. (I say adding 23 pounds because someone here will undoubtedly try to tell me the forces in flight are different). DUH, but the full "runaway" trim adds 23 pounds to whatever normal in flight forces are there.
                              You may want to ask Phil if the two-handed stick effort required to keep him from bunting over felt like only 23 pounds.
                              Things are different in the air with a live rotor system.
                              Meanwhile, I applaud your spirit of inquiry and experimentation.

                              Regards,
                              Kolibri


                              PP - ASEL complex (C172RG, Piper 180, C206, RV-7A), SP - Gyro (Calidus, RAF, SC2), 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


                              • In my opinion if the cyclic in a Cavalon was jammed full forward the aircraft would exceed VNE at any throttle setting.
                                With a high enough beginning altitude, I'd agree.
                                But, he did not start that high, and from witness reports we know that he did not make a continuous dive into the ground, much less at Vne.


                                In my opinion Kolibri's hypothesis that you can slow a Cavalon down with the cyclic jammed full forward by reducing the throttle is demonstrative of his lack of understanding of how a gyroplane flies.
                                Selective reading of my posts, Vance. As I stipulated, Chris seemed to have some aft cyclic ability, although not enough:

                                HOWEVER, where I think Chris got to was the rotor disk just below level flight AoA, and with the rotor brake actuated through reversed aft trim.
                                He had apparently slowed his descent with some aft cyclic, but hadn't enough to either vertically descend or mush in with power.
                                I feel Kolibri's understanding of managing rotor rpm is sufficiently divergent to preclude communication.

                                I was reluctant to let this go because of a concern for this misinformation causing a safety issue.

                                I see now it gives Kolibri an opportunity to expand the misunderstandings as though it was an actual discussion.
                                You have the oddest mental "lens" with me, apparently configured to assume that I must be incorrect in something that I post.
                                You readily misunderstand me, and then use that as a straw man to accuse me of error. I should start a file with excerpts.


                                However, you are the one who pooh-poohed my theory from page 1, and countered with your claim that forward trim forces would be easily overcome in BRAKE mode.
                                As Phil described, they were very difficult to resist even with both hands on the cyclic.
                                PP - ASEL complex (C172RG, Piper 180, C206, RV-7A), SP - Gyro (Calidus, RAF, SC2), 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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