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AR-1 N923DJ Texas 15-12-18

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  • Originally posted by Kolibri View Post
    This would help: disavow any inference that a descending column of air can make 90 degree radial turns above ground without having first hit the ground.

    Such would clarify a proper mental picture, thank you.

    Air moves because of pressure differential.

    Air moves from a higher pressure to a lower pressure.

    Air stops moving when the pressure equalizes.

    In my opinion a column of air doesn't need to hit something to change directions.

    It appears I can't help you with your mental picture of a world without boundary layers.

    I can accept that.
    Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

    Comment


    • I'm certainly aware of air pressure differentials.
      I think you know what I'm asking and why, but won't answer.
      And I can accept that.

      ____________
      I've little time for any thread where simple facts won't be given their due, evidently because of who presents them.

      Others are welcome to defend the existence of in-ground-effect cushioning/increased lift, or generally decreased turbulence/gusts very near the runway vs. dozens of feet above it.

      I've got to get back to work; good day.


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

      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


      • Originally posted by Kolibri View Post
        True, loftus, but remember that we're mostly talking about moderate downdrafts vs. extreme ones.
        And, I thought it important to clarify the notion that horizontal transference requires the descending column of air to have first hit the ground.
        Vance many times has written that
        "downdrafts don't (or don't usually) reach the ground" and I disagreed with that as a blanket statement.
        Rather, I think they often reach the ground.


        A tautology of "downdrafts don't reach the ground, unless they do" doesn't seem very helpful.
        I think the point is ( and Vance has a different way of putting it) is that the full vertical component of a downdraft (or the major bulk of it) does not go all the way to the ground, whether it's a weak one or a strong one. Imagine the downdraft as a moving 10 foot wide fluid stream that turns horizontally as it approaches the ground. There is obviously a transitional distance over which that stream turns with the outer edges of the stream turning more gradually and the central part of the stream more abruptly - effectively these outer components will never reach the ground, hence 'do not go all the way to the ground' whereas the central component will possibly go all the way to the ground, but at ground level will have 0 vertical component as it turns more abruptly. There will also effectively be a 'cushion' of horizontally moving air from this transitioning downdraft. All of this is well diagrammed and also shown with radar images in the links I posted. I think the most illustrative images are the radar images showing wind from a downdraft or microburst moving vertically in the higher levels then horizontally at the lower levels. This implies that at the lower levels, closer to the ground, the downdraft no longer accurately describes the direction of air movement. Obviously there are other aspects such as turbulence etc going on as this process occurs, but I think it's pretty clear what Vance means - so yes strictly speaking at least part of the downdraft airmass does reach the ground, but in practice because of the change in vector to a horizontal component no longer acts in a downward fashion on the aircraft. So from the viewpoint of the aircraft and pilot I think Vance is correct that the 'down' part of the draft does not go all the way to the ground, as it becomes a 'sidewaysdraft'.
        So I think you are just arguing semantics now. Vance's concept is descriptive from a practical standpoint as the 'down' part of the draft will be much weaker, possibly insignificant to the pilot closer to the ground. One could apply differential equations to this of course but the reality is that a good portion of the downdraft never reaches the ground, and the part that does has 0 velocity downwards as it hits. If I were to only show you the lower level radar images of a body of air that started as a downdraft, you would not be able to differentiate these from radar images of a strong wind blowing horizontally across the surface. I think the fact that these images are easily obtained would indicate that this body of horizontally moving air (that used to be a downdraft) extends significantly up from the surface. I will see if I can find info on just how high up this may extend above the surface, but I imagine it's proportional to the size and strength of the downdraft. I don't think the fluid dynamics as applied to a normal downdraft are any different to those of a microburst except in magnitude. All easy to understand by looking at the simple diagrams which I am not able to post but you can see in those links.

        Comment


        • Originally posted by Kolibri View Post
          I'm certainly aware of air pressure differentials.
          I think you know what I'm asking and why, but won't answer.
          And I can accept that.
          ____________
          I've little time for any thread where simple facts won't be given their due, evidently because of who presents them.

          Good day.
          I have done my best to answer the questions you have asked Kolibri.

          I don't know why your asking or have a reason for not answering because I have answered your questions; most several times.

          I don't know why you imagine a world that does not have boundary layers.


          Originally posted by Kolibri View Post
          Antony, we're all pilots. None of us has the luxury of being wrong.
          All of us have the desire to be "Right". It keeps us alive.
          Now, how we do so on this forum is another matter, and worthy of discretion, courtesy, and respect.
          I've not always comported myself well there, and neither have others.

          Look, it's the first week of a brand new year, 2019. I actually do not revel in discord.
          I apologize for any that I've created or kept energized.
          Shall we all begin anew?
          May I be the first to offer across the miles a handshake of friendship and solidarity to my fellow gyronauts?

          I believe that we owe a respectfully growing knowledge base to those aviators yet to come, and a professionalism probably not yet seen in the gyro community.
          I am keen to lean my shoulder into that common mission.

          Safe flying and best wishes to you all,
          Kolibri
          Your new cordial approach to interacting with pilots didn't even last two days.

          In my opinion if you placed less importance on making other people wrong you would learn more on the Rotary Wing Forum Kolibri.
          Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

          Comment


          • Originally posted by loftus View Post

            I think the point is ( and Vance has a different way of putting it) is that the full vertical component of a downdraft (or the major bulk of it) does not go all the way to the ground, whether it's a weak one or a strong one. Imagine the downdraft as a moving 10 foot wide fluid stream that turns horizontally as it approaches the ground. There is obviously a transitional distance over which that stream turns with the outer edges of the stream turning more gradually and the central part of the stream more abruptly - effectively these outer components will never reach the ground, hence 'do not go all the way to the ground' whereas the central component will possibly go all the way to the ground, but at ground level will have 0 vertical component as it turns more abruptly. There will also effectively be a 'cushion' of horizontally moving air from this transitioning downdraft. All of this is well diagrammed and also shown with radar images in the links I posted. I think the most illustrative images are the radar images showing wind from a downdraft or microburst moving vertically in the higher levels then horizontally at the lower levels. This implies that at the lower levels, closer to the ground, the downdraft no longer accurately describes the direction of air movement. Obviously there are other aspects such as turbulence etc going on as this process occurs, but I think it's pretty clear what Vance means - so yes strictly speaking at least part of the downdraft airmass does reach the ground, but in practice because of the change in vector to a horizontal component no longer acts in a downward fashion on the aircraft. So from the viewpoint of the aircraft and pilot I think Vance is correct that the 'down' part of the draft does not go all the way to the ground, as it becomes a 'sidewaysdraft'.
            So I think you are just arguing semantics now. Vance's concept is descriptive from a practical standpoint as the 'down' part of the draft will be much weaker, possibly insignificant to the pilot closer to the ground. One could apply differential equations to this of course but the reality is that a good portion of the downdraft never reaches the ground, and the part that does has 0 velocity downwards as it hits. If I were to only show you the lower level radar images of a body of air that started as a downdraft, you would not be able to differentiate these from radar images of a strong wind blowing across the surface. I think the fact that these images are easily obtained would indicate that this body of horizontally moving air (that used to be a downdraft) extends significantly up from the surface. I will see if I can find info on just how high up this may extend above the surface.
            Thank you Jeffery; as always your post is well written and on point.

            I work at providing clear, applicable explanations to my clients.

            I want them to have the tools in their tool box to manage unexpected challenges.

            If I get stuck on some point face to face with a client it is easy to work it out.

            My wife says I cannot communicate without my hands.

            The Rotary Wing Forum is a challenge because people of all backgrounds and levels of understanding are reading the answers to questions they didn't ask and I can't use my hands.

            In training there is a syllabus and I can speak to that level of experience.

            I know what mistakes they have made and what their lifeís experiences are.

            On the Rotary Wing Forum I am dropped into the middle of a lot of peoples experience and donít know much about their background.

            If I donít address something posted that is incorrect someone could get hurt or killed.

            I share my opinions when I feel there may be value in my experience.
            Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

            Comment


            • Has anyone been caught under Virga?
              https://en.wikipedia.org/wiki/Virga

              In a trike it took us down from 3000 feet AGL to 50 foot AGL with full power before the trike could fly out of it.
              That's new underwear territory

              Comment


              • In my opinion flying under or around virga is a very bad idea.

                The rain evaporates before it reaches the ground and the evaporation cools the air sending it down.

                I have flown around virga in California in the high desert and in Nevada, Utah and Arizona.

                If I can see virga it is too close.
                Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

                Comment


                • If a gryo's rotor blades are no lower than 9+ feet off the ground, that's plenty high enough to be subject to the force of a downdraft.

                  _____
                  Your new cordial approach to interacting with pilots didn't even last two days.
                  Cordial means cordial, which I've been.
                  It doesn't mean wholesale acquiescence to another's opinion.
                  It certainly doesn't mean that I ignore an obvious evasion of truth.

                  Speaking of which, does flying in ground effect increase lift, or merely reduce induced drag as WaspAir claimed?

                  I notice an absolute silence from everyone on this, after I'd quoted an aeronautical paper.

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

                  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


                  • Originally posted by Kolibri View Post
                    If a gryo's rotor blades are no lower than 9+ feet off the ground, that's plenty high enough to be subject to the force of a downdraft.

                    _____

                    Cordial means cordial, which I've been.
                    It doesn't mean wholesale acquiescence to another's opinion.
                    It certainly doesn't mean that I ignore an obvious evasion of truth.

                    Speaking of which, does flying in ground effect increase lift, or merely reduce induced drag as WaspAir claimed?

                    I notice an absolute silence from everyone on this, after I'd quoted an aeronautical paper.

                    Regards,
                    Kolibri
                    If you actually read and understood what you posted a link to: "Wing in Ground Effect Craft Review" you would understand how off point it is in relation to landing a gyroplane..

                    You notice absolute silence because people here are tired of feeding the troll.
                    Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

                    Comment


                    • Thanks for information on Virga Fara and Vance. I was not aware of this, but have seen it before flying.

                      Comment


                      • You are welcome Dave.

                        It is not unusual for the descending air beneath virga to exceed 2,000 feet per minute and can reach over 4,000 feet per minute.

                        The National Weather says "In certain cases, shafts of virga may precede a microburst."

                        Virga can also turn quickly into Instrument Meteorological Conditions because of the rapidly cooling moist air.

                        More than a few pilots have wandered under virga and typically only do it once.
                        Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

                        Comment


                        • Originally posted by DavePA11 View Post
                          Thanks for information on Virga Fara and Vance. I was not aware of this, but have seen it before flying.
                          Did you finally move out west, Dave? I understand the phenomenon is more common out there, where there is often dryer air under the clouds.

                          Comment


                          • If you actually read and understood what you posted a link to: "Wing in Ground Effect Craft Review" you would understand how off point it is in relation to landing a gyroplane..
                            I did read it. I did understand it. I simply disagree with you.
                            There is increased lift in ground effect for a gyroplane.

                            To claim that there isn't is to believe that the boundary layer prevents the full formation of wingtip votices (which reduces induced drag),
                            while not also increasing air pressure underneath the rotor. This would be a rather amazing proposition. Good luck in defending it.
                            It's just easier to call me a troll instead. Fine, Vance, have it your way.

                            I trust that some readers of all this will have a look into it for themselves.

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

                            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


                            • Tyger - Yes. I had to move to Colorado for work, and sold my plane and gyro. Once I buy a house will look into buy another plane or gyro. Thinking I will buy a Husky so I can fly to some of the other states around Colorado. Itís a big change from outside Boston area so just starting to get use to it. Really bored not being able to fly. Probably should have kept my gyro or plane... :-)

                              Comment


                              • Originally posted by Vance View Post
                                In my opinion flying under or around virga is a very bad idea.

                                The rain evaporates before it reaches the ground and the evaporation cools the air sending it down.

                                I have flown around virga in California in the high desert and in Nevada, Utah and Arizona.

                                If I can see virga it is too close.
                                The VIRGA-effect was experienced by Greg Gemminger ...when a group of Magni fliers did a tour out to Southern Utah several years ago! Great trip as narrated Ö..but above ALL ...I remember the experience that one pilot ( ???maybe Greg??) had when flying under a cloud shedding virga ...the scary experience as narrated IMPRESSED upon me ...NEVER fly under VIRGA! ...On my flights in FL two years ago & in Australia April 2017 Ö I was very careful to give the innocent-looking little grey clouds with the pretty virga-veils of evaporating moisture ...a WIDE berth!
                                Chris T.
                                3Rs - Rotors rock & rule!

                                "Blessed are the flexible for they shall not be bent out of shape." Buck B.

                                Time flies if you can but only the slowest.

                                PRA# 4212
                                EAA# 1126845
                                AOPA#08888697

                                Comment

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