Tall tail

[aussie_paul]

West Oz,The subject of this thread, the "Tall Tail" is about the only good thing(dynamically) on that gyro. My initial reaction when I saw the photo was all that power so high above the COG and nothing to stop it from continually trying to tip over forwards.(Apart from Max"s steady hand,and thats assuming he"s not flying over a nudey beach)The fact that the whole layout is inefficient,HS pushing nose up/engine pushing nose down is immaterial.Placing the HS 4 Inches higher would achieve nothing. Placing it 18 inches higher would achieve lots. Placing a suitably sized

[Disco]

Mm, sounds like you"re talking about induced drag which is greater at high angle of attack. It has nothing to do with a or is it reduced by having a gearbox over a belt or direct drive.

[WEST OZ FLYER]

Its a lot easier just taking the thrustline/ COG problem out of the equation. - TrueThe fact that the whole layout is inefficient - AgreeMurray can you explain to me why in "AIRWORTHINESS DIRECTIVE AD 2002.02" the HS volume is a percentage of the rotor volume? It"s got me baffled for awhile now. Birdy, no need to try again I understand completely. The key word I used was "perceived" not actual torque roll. Was only really trying to explain MadMuz"s theory better. Maybe I should have used "feels like".

[gyroo]

C"mon guys -It"s back to High School time for some of you!!Newton"s 3rd Law: For every action there is an equal and opposite reaction.We all know that a chopper needs a tail rotor to stop the fuselage turning in the opposite direction to the rotor. Any propeller driven flying machine behaves the same way, regardless of whether the prop is speeding up, or is in a steady state, or is slowing down. The combined induced and parasite drag from each propeller blade (action) results in a torque that is absorbed into the fuselage attached to the engine (reaction). The reaction is always present but because of the much greater mass of the airframe (in a plane, for instance) the rolling tendency is not particularly noticeable and is usually compensated-for by a slight rigging bias in the aileron or aileron trim tab setup. Of course, a gyro doesn"t have fixed wings with ailerons on them, but what they do have is a rotor way up high which can be considered the virtual equivalent of chopper"s tail rotor if you imagine that as the prop spins in one direction (action) the gyro frame wants to spin in the opposite direction (reaction), but the rotor up top stops the gyro frame from rolling because the pilot is "flying the rotor" straight and level and subconsciously adding in a very slight additional lateral stick input (a minute one) to offset any torque generated by the prop.Its when a pilot does something that causes the rotor to approach zero-g and the rotor is unloaded that a real risk of propeller torque rolling the gyro frame in the opposite direction comes into play. What I mean by that is - for instance - with the Gyroz that turned sideways at Nowra earlier this year, the Gyroz "rolled over" astonishingly quickly into the relative airflow coming from the left hand side. When viewed from behind, the Gyroz propeller spins clockwise, and in the fatality video taken by a GoPro mounted on the Gyroz, the fuselage rolled suddenly to the left in an anti-clockwise direction, with the engine running at a high power setting.My personal hypothesis after viewing the video about 30 times is that it is likely that the rate of the anti-clockwise fuselage roll was probably hastened by torque from the propeller, and because the rotor was "unloaded" by the turning sideways the rotor was no longer able to generate any moment to counteract the prop torque.Of course, one must also not overlook the fact that when the Gyroz turned sideways, it presented an awful lot of side-on surface area to the relative 40 to 50 knot relative airflow, and most of the surface area was below the centre of gravity, which therefore would have also exacerbated the left roll.So, which was the predominant influence on the roll? Airframe drag, or propeller torque? I don"t know, but I reckon both forces were in play.Cheers,Mark ReganMelbourne

[asra]

West Oz,The Rotor size/ Tail volume is a Cierva formula.The smaller the HS the further back it needs to be.The Cierva"s were CLT, not sure why rotor diameter even comes into it,his original patent may hold a clue? Having said that, rotor thrust or lack of can be the start of all sorts of nasties so maybe he wanted to cover all bases with the biggest HS to cover what he thought could be the lowest RT he could encounter?Another clue may be that the original Autogiro"s were controlled by ailerons and elevators and had a fixed rotor.Its a good ballpark figure for the type of gyro"s we build but very ambiguous.The only gyro I can think of that comes close to reaching that formula would be the Little Wing, and only because the tail has such a big moment arm.The Sparrow Hawk maybe another.

[birdy]

It"s back to High School time for some of you!!I was thinkn preschool. >Torque roll has nuthn to do with engine rotation, redrive type, frame drag, rotor speed , slippery cab or draggy open frame , force= mass x acceleration or wot colour joks you got on, if any,and theres no perception, its real.Torque roll is simply the circular drag ( wing resistance) on the prop blades transfern a torque force on the frame.Very simple.Higher the prop rpm, ( ona fixed pitched prop) higher the drag, higher the torque transfered over the frame, through the prop axis.

[MadMuz]

Since this thread has gone completely off topic, but is still on tails and hang tests and all.... does ASRA or anyone have figures on the thrustlines and CofG of the euro clones and Calidus etc? Just so we can see what the thrustlines of the clones are and which is best/worst etc? I just saw some pics of a new arrowcopter that is coming out and it looks as HTL as all the others? I would just like to compare them all, not with their factory supposed thrustlines, but with the info that each machine has submitted for ASRA registration?Speaking of easier to build right to begin with, than build and make right.... why would this new arrowcopter be the same old HTL recipe as all of the others? I wonder why some of these manufacturers don"t decide to pay some attention to the thrust line?

[gyroo]

Hello Mad Muz,Excellent question! I don"t yet have a comparative chart of relative thrustlines for European factory built machines because (1) surprise, surprise:

[WEST OZ FLYER]

Thanks Murray.

[maulonir]

Hell Mark,The

[MadMuz]

Thanks Mark, I take it from your post that the euro clones that we see so many of these days, that looks so HTL..... in fact probably are just that, but ASRA doesn"t really know? For anyone in Aus to register a machine, especially a 2 place machine, the hang and lean back test MUST be done and photographed? Why should owners of factory machines not have to do the same thing? As you have stated, the manufacturers will have fudged figures to look ok..... surely ASRA is concerned that they don"t know the true thrustline figures of many of the 2 place machines especially as even a person very new to gyros can see the thrustline appears very high? There have been accidents overseas involving euro clones, what will ASRA tell CASA if we have an accident over here with a clone and they ask what the balance was for that model? I guess ASRA will just have to say they don"t have any idea, but the manufacturer reckons it is good? I wonder how well that will go down?This thread began as a bloke showing us the new "tall tail" he had made.... not the machine, just the tail.... for his trouble, he has had his entire machine judged by most of the top guns from ASRA, including that you Mark want to physically check its weight and balance because it "looks" HTL.... but to me it just looks about the same as any of the 2 seat tandem euro machines? If you must double check this machine, then surely you "must" double check the various brands of obviously HTL manufactured machines?Every country just accepting the manufacturers claims that their machines CofG and thrustlines are "OK" is just allowing more suspect HTL machines to be produced.... sooner or later a machine will have an accident in one of these countries and then the poop will hit the fan...... especially if subsequent investigations prove the machines are in fact as HTL as they look

[Brian]

Webbie, to be fair to Max, could we have the pages from when this topic changed & be put into the relevant topic as it seems that this could go on & on for some time yet.Thanks

[tonydenton]

always so
..........

[gyroo]

For Mad Muz,The primary purposes of the 2010/2011 Fleet Survey was to answer the questions of what the average thrustline/CofG situation was with Australian homebuilts, whether there were any gyroplanes out there that were dangerously HTL, and to generally raise the general level of awareness within the membership about the scientific work that had been done in the United Kingdom about the Thrustline to Centre of Gravity relationship.Even getting the Fleet Survey up and running caused a hell of a lot of controversy and dissension, with naysayers loudly broadcasting that in their opinion the whole process was unnecessary and a waste of time and the most trenchant critics were spreading rumours that ASRA would be moving to ground gyros thy didn"t like after the results were in.In any event, the Fleet Survey was a success and we were able to answer the most pressing question, namely that most Australian homebuilts do tend to be higher thrustline than the UK research recommends but that the variation outside the plus or minus 2 inches was not particularly worrying. Only a very small number of gyros exceeded 8 inches HTL, but a small number were beyond 12.To date, no gyros have been grounded on the basis of HTL concerns. The then Board made a decision that as long as ASRA members were made aware of the possible consequences of a machine being HTL, or even very HTL, that people would be able to make reasoned and informed decisions about whether they would buy or fly them. In the longer term it was anticipated that as awareness of Thrustline/CofG issues became more thoroughly understood, machines that were obviously very HTL would be gradually sidelined and retired. To some extent, at least, this process has occurred.The European Import SituationMost of the European machines on my "wishlist" weren"t available to us back in 2010.And, frankly, because much of my attention since 2011 has been focussed on cleaning up after a succession of fatal accidents or drafting the ASRA Technical Manual, it can probably be said that I have "dropped the ball" to some extent from being ASRA"s "resident Thrustline Policeman", a role that is controversial to say the least.In an ideal world I would love to have all of the machines in my "wishlist" in one place on one day so that we could methodically survey them all PROPERLY and ACCURATELY.You have suggested that I have powers that I don"t really have. With much of the work I have to do with ASRA I have to encourage, cajole, nudge and convince people to do what I ask. If I came down hard, or tried to come down hard on Thrustlines I anticipate 2 things would happen: (1) there would be a membership revolt; and (2) I would be tarred and feathered.We"re a voluntary organisation for Christ"s sake, manned by volunteers, and with all our processes devised by volunteers.If you Mad Muz are volunteering to be the co-ordinator of the surveying of European factory built gyros in Australia, then good luck to you.Mark Regan

[MadMuz]

Hello all,I"m getting involved in this, having only in the last few days become aware of the existence of G0023. I agree that this should not become "trial by forum", but a few observations need to be publicly noted.The first thing I"ll say to Max is that absolutely no-one is doubting your piloting skills and lengthy experience. And I very much envy your NT lifestyle.The consternation expressed by Murray - and now by me - (and also now under active Board discussion) is based on the concern that the general configuration of G0023 appears to involve a total rejection of the "plus or minus 2 inches" propeller thrust line to Centre of Gravity "sensible design aim" advocated by the UK CAA and clearly endorsed and promoted by ASRA for the past 3 years. I regard it as involving retrograde design choices. Clearly G0023 is a "new build", and could - should - have very easily been configured to take advantage of the UK scientific research.You have set the surplus Kruza pod much lower than the Morrison brothers ever did on any of the Kruzas they built, and hence the mass of the pod and occupant(s) will be much lower and contributing greatly to G0023 being a VERY High Thrust Line machine. No-one doubts that a pilot of your experience would very likely subconsciously deal with any dynamic aberrations that occurred in flight - and possibly not even notice them - but ASRA must always be vigilant to protect unsuspecting passengers, whether they be sightseers or potential students, or any inexperienced low-flight hours purchaser should you sell it down the track.The thrustline of G0023 appears to be at least as bad as a RAF 2000 and possibly even worse. Your design choice seems baffling, seemingly disregarding the progressively accumulated body of government-funded scientific knowledge on gyroplane dynamic stability coming out of the UK over the past 15 years. The RAF 2000 is a well and truly obsolete configuration and those still flying remain potentially dangerous in the wrong hands, as the type"s sorry international accident history clearly shows (including further very recent fatalities in the US and South Africa) and the Brits have slapped on severe performance restrictions on the remaining examples still in use there. The remaining 6 examples on the Australian register are being "closely watched". If any further RAF issues emerge with our remaining examples, the UK restrictions might have to be imposed here.Referring back to your G0023, as another Board member commented in discussion tonight ....... "it would have been just as easy to build right than build wrong". In other words, it would have been just as easy at the initial build stage to have arranged for the pod to be 10 to 14 inches higher than it now is.Until proved or demonstrated otherwise, I"ll be regarding G0023 as a pointier RAF 2000 clone likely to have all the lurking dynamic issues that bedevil RAFs in the wrong or inexperienced hands, and I"ll be regarding it as a problematic step back into the "bad old days" of the 80"s. Truly regrettable.I will shortly be calling for reliably accurate and corroborated empty weights and all details of G0023, plus corroborated and verified hang test and tilt back A4 photographs of G0023, plus all the registration paperwork. I trust all is in order?I thank you in advance for your future co-operation with the Board"s inquiries.Kind regards,Mark ReganMelbourne(as Technical Manager)