Manuvers in HTL/CLT/LTL gyros

[Greg Mitchell]

"Either that or the stab is effective enough, and rips the rear of the machine up so fast it out runs the rotors, and gets chopped off."I used to think the stab could be oversized and do just that Birdy. That's why when some say the bigger and the further back the better, you cant help but think about that scenario.Interesting that my instructor tells people the Raf when trimmed will fly itself, must be that it to, is stable with its aftermarket HS fitted. Haven't heard from any experienced guys with time in CLT or slightly LTL craft.Starting to think I should have got myself a slightly HTL craft with no HS!!!!!Cheers,Mitchwww.thebutterflyllc.com

[Brian]

Hi Mitch, just to clarify one point, my gyro has a HS. Have never flown a gyro without one. The only thing I can tell you is that back when I started flying Gyros, I was privalaged enough to see David Jackson do a few "demos" in his gyro, I remember well being in awe of what he was able to do and I tried to model my flying on his. Naturally, I fell well short.I have seen a quite few "demos" since but none have compared to Jacko's !Brian

[asra]

quote:Originally posted by TimReal CLT, and to a worse extent LTL gyros drop the nose very quickly and to quite a steep attitude on cutting the throttle. I think we have some confusion here about what the thrustline is measured relative to.Indeed, true CLT (relative to CofG) should be totally throttle neutral AS FAR AS TORQUE AROUND THE CoG is concerned.There is the attendand problem of thrustline position relative to Centre of Drag.Machines should be built neutral to both.If a machine is CLT wrt CofG, but not wrt CofD, then it may well behave as described.

[Greg Mitchell]

G'Day Don,Well said, I was waiting for someone else to jump in. That's exactly right. The Key is to have the thrust line and centre of drag, COAXIAL with the C of G OR nearly so AND if the HS is in line with the thrust, (Both in line with the keel), then there should be no torquing moment around the C of G with power changes or airspeed changes.I believe this is why my gyro is such a sweet flyer and presents non of the problems Tim speaks of.So why wouldn't such a craft be as capable or more so (given its inherent stability) of performing as well or better than a slightly high thrustline craft in the avbove scenarios????Cheers,Mitch.www.thebutterflyllc.com

[Greg Mitchell]

Hey Brian,How have you been Mate. When are you and Rosey?? planning a holiday down this way?Brian you indicated youd been entered a down sheer, then an updraft, such as Birdy had described. Did you find the HS Over reacting to realigning itself with the relative airflow? Was it a very sudden reaction with major 'pucker value' attached?There is a lot of use of the word "ADEQUATE" when manufacturers talk about vertical fins and HS'sWhilst some say that a Rosco HS is small, it should be noted it is on a fairly long moment arm and would in my opinion be more that adequate. In other words, weathercock appropriately, in the correct direction. Did you ever fly your craft as open frame, before installing a pod? If so was it the same HS, in the same position? And did you find it was still adequate?Hope you got all the rain you needed over the last couple months.Cheers,Mitch.www.thebutterflyllc.com

[Tim]

quote:I think we have some confusion here about what the thrustline is measured relative to.Indeed, true CLT (relative to CofG) should be totally throttle neutral AS FAR AS TORQUE AROUND THE CoG is concerned.There is the attendand problem of thrustline position relative to Centre of Drag.Machines should be built neutral to both.If a machine is CLT wrt CofG, but not wrt CofD, then it may well behave as described.G'day Don. There is no confusion. CLT means that the thrustline passes through the C of G. I do agree with you though in that the centre of drag (C of G)is important and is not given enough consideration when talking stability. The C of D though has little effect on abrupt power changes because the pitch changes that I am talking about take place with power changes, not with airspeed changes. If it happened with airspeed changes then C of D would be a factor, but this is a whole new kettle of fish and would warrent a new discussion.Tim McClure

[asra]

Image Insert: 13.95

[Tim]

Stan, its good to see you join in on the discussion. The more input we have on any subject, the more we can learn. Thanks for posting those diagrams - there is some good information there for all of us interested in reducing drag. quote:If the C of D is not on the same line as CG and CT the torque force will have a great effect on pitch stability changes especially if you play with the power setting maintaining the same air speed. If you decease the power then you also decrease the thrust vector but drag will stay the same also the torque force from the drag will increase but depending on the distance of C of D to CG the torque moment may dramatically change.You got me on that one! The center of drag does not change, but the thrust vector force does - yes I can see that. Maybe this is one of the reasons why theoretical CLT gyros do pitch somewhat with power changes. You may have the answer to my earlier dilemma. Hang on, a higher C of D as in a CLT machine should then cause the nose to come up under power reduction, but this is not the case.O ****, back to the drawing board. "Hang on, a higher C of D as in a CLT machine should then cause the nose to come up under power reduction"Please read correction to this statement in my next post below,Tim McClure

[Brian]

Hi Mitch,Been really busy here on the farm, yes, we have had beautiful rain and now have green grass, not very high but its the best its looked for many a year. Rosie and I had a couple of weeks holiday but headed to Sydney for Hillsong, the Christian Conference so we are still looking to get Tassie way but we might give it a go this summer.Yes, had a big downdraft followed by a bigger updraft, the downer happened just as I was trying to climb and I found myself very close to the ground with a lot of throttle on then when only about 20 ft off the ground up we hit the upper going up at the velocity of a missile for approx 600 feet before being dropped down about 50 ft where we leveled out!! Can remember the nose dropping a little in the updraft but I cant remember what it did in the downdraft, I know I had backstick and was feeling the rotors, making sure they werent slowing down ! Did reduce throttle to idle on the way up.Can remember a lot of "pucker" factor present going both up and down as it was very sudden and the air had been pretty good untill that moment.I have no idea how the HS fared in the event Mitch except to say the whole thing was more of a nuisance than anything else. My personal opinion is that the Rosco designed gyro is a pretty good gyro, NOW PB for example will tell you its not a good gyro because it isnt CLT, I have never flown a CLT gyro so I cant say its better or worse. The only thing I can say is that the Rosco design gyros have accumalted many thousands of hours and HTL gyros would have a huge number of hours up in working conditions, some flown by pilots who have taught themselves many years ago .No, never flown this gyro as an open framed gyro, my first gyro was an open framed Max Peters design and was a great bush bus, very slow but extremely tough, very underpowered as well [4200 revs cruise and 4400 max !!] so I learnt to fly very smoothly at tree top level!! I reckon I owe this gyro lots in getting me ready for when I did eventually get a more powerfull gyro !!I would agree with you in regard to Roscos HS being adequate, I'm going to try a bigger one if he ever gets around to making it just so I can se what if any diference it makes.Thanks for all the photos you have done over the last few months on your trip away, I'm envious !! PS, I not making fun at PB or CLT gyros, just telling as I know it.Brian

[asra]

BirdyInteresting example of shltty weather flying, answer is dont fly In that type of weather.You would find that a CLF or LFL machine would nose up regardless of the size of the HS.This is because the C of G is located forward of the rotor thrust vector.If a down draft slightly unloads the rotor it will raise the nose.If there was an up draft it would again load the rotors and lower the nose.I see these things as positives, but in the case of a HTL machine you are totaly reliant on the HS in a down draft.(Or pilot skills and reaction time)Regards Sam.

[Brian]

Sam, some of us have to work in those and worse conditions to do a job and its not dangerous once you know whats happening , just a nuisance.Interestingly enough Sam is that so many bush pilots learnt in and flew theses same HTL gyros and are still alive to tell the tale.Brian

[asra]

Birdy, Just curious as to why do you think that a CLT H stab gyro will make large pitch change in a updraft or downdraft. I have only flown gyros with this configuration. I have probably 380 hrs in this type. It has been my experience that the machine will ascend or descend with virtually no pitch change. Kind of like riding an elevator. The rotor sees the same wind change that the horizontal and thus works to keep the craft level.Brad KingN6372KMad Max II LTCImage Insert: 34.31

[Greg Mitchell]

Good stuff Guys,Now this is getting interesting with lots of good info..Like to Welcome Brad King ( Gyro Instructor and Co-Pilot Carter Copter) to the forum. Nice pic Brad. Is the new engine up and running in your Mad Max II. ??Brian,You know I have the greatest respect for the Rosco ships and the bloke/blokes behind them. I am only looking to generate some discusion and Rosco's craft are so prolific it seemed a good local example to draw experiences from. Good to hear from you again.Stan, Mate....and in perfect English, good stuff. About time you poked your technical head in, Thanks Mate.Tim,Not sure why the higher C of D should cause the nose to come up on power reduction if the C of D is coaxial with C of G and thrustline??Sam,Brian and Birdy and all the other guys mustering, fence and bore running, will fly in all sorts. I think this is where they get most of their FEEL for the AIR and what it does. This is why I am very interested in feedback from these high hrs pilots(in high thrustline gyros)to compare notes against others experiences in CLT or LTL: Hows your Dragonfly going Mate?, hope your having a blast. Whats CLF and LFL???Thanks Gents.Mitch. www.thebutterflyllc.com

[Tim]

quote:Originally posted by Greg MitchellNot sure why the higher C of D should cause the nose to come up on power reduction if the C of D is coaxial with C of G and thrustline??I agree totally with you Mitch. If all the forces are coaxial, there should be no pitching moments whatsoever with either power changes or gusts. Following up further on Stan's point on how the centre of drag placement in relation to the thrustline can cause pitching moments. I think we will have to take this as a stand alone reaction and discount the C of G and the H/stabilizer for the sake of clarifying the point.Assuming 2 machines are in level flight, one with the thrustline below the C of D, the other with the thrustline above the C of D. With the thrustline below the C of D, the gyro has a torque tendency to nose up under power, so forward stick must be used to keep the gyro S & L. (forward stick moves the rotor thrust vector back adding "weight" to the nose to counteract the nose up torque). A cut in thrust would then cut the nose up torque. As the gyro is trimmed for flight with that torque, then it stands to reason that the gyro will drop its nose when that nose-up torque is removed.With the thrustline above the C of D, the opposite would happen and the gyro would nose up when the power is reduced. quote: Tim, Not sure why the higher C of D should cause the nose to come up on power reductionSorry Mitch - I was back to front on that one, as explained above. quote:Starting to think I should have got myself a slightly HTL craft with no HS!!!!! Personally I would not go without the H/S - you will have to discuss that one with Birdy. It obviously has some disadvantages when doing some of the manouvers that he does. Slightly high thrustline is only my preference. Many of the intelligent practical theorists prefer the nose to drop under power reduction, to maintain a safe airspeed. My preference is to have no avoidable sudden uncommanded reactions in the airframe.Maybe the ideal would be to start with CLT, and adjust the C of D to get the desired reactions for flying personal preference. Tim McClure

[Greg Mitchell]

Cheers Tim,This is good stuff and appreciate your input. Of course I am more than happy with my gyro and would not contemplate flying even a CLT type craft without a HS. I'll leave that to blokes like Birdy, who know what the nature of the beast is.Whilst I realise everyone will have preferences for one type or another, it is the theoreticals and the hands on experience in type that I am hoping to draw out here. I reckon Larry did a top job on configuring the Butterfly/Monarchs. When I get the test peice back (instrument tube painted Metallic Baltic Blue) I'll be keen as mustard to get cracking on the repaint/rebuild.Agree with your comments above when you brake it down so.My preference to, is to have no avoidable sudden uncommanded reactions in the airframe and with Drag, Thrust and C of G coaxial OR NEARLY SO, there should be minimal/nil pitching moments with change in power or gusts. ""Maybe the ideal would be to start with CLT, and adjust the C of D to get the desired reactions for flying personal preference.""That makes good sense to me.Cheers,Mitch.www.thebutterflyllc.com