Pacific Flyer story

[asra]

John, I have no problems discussing any incident accident that I have unfortunatley been involved in.Unfortunately you do not remeber correctly. It was not Chuck Beaty who said that. It was a poster called gyro Ron. I am glad you enjoyed it!! Chuck was helping me, as he always does.John your recollection of my roll over is not accurate either, but that is beside the point.I was PIC and stuffed up. I am sure some others have also. My point of asking for info was that I was looking for design parameters that could improve the outcome of a stuff up. A bit like a stab with with a HTLM.We found a couple of areas that could be redesigned to help, rather than hinder if I stuff up the same way again.Thanks for the input.Aussie Paul.[]www.firebirdgyros.com

[asra]

Originally posted by Tim>> Anyone with common sense can tell you that it is impossible to achieve CLT unless the C of G of the pilot and the fuel are both on the thrust line.>> (b) Setting a prescriptive requirement for CLT (to avoid PPO) is wrong because of the different moments of inertia of different gyro's. A good example would be the vast differences between a Butterfly with a light pilot compared to a RAF with two portly occupants on board.I have a single seater, which was tested with me in it. I doubt my posture or wieght will vary sufficiently to be a problem.Also, the issue is not the weight of the occupants. It is where their cenre of mass is placed. Two heavy occupants may well shift the CofG forward, but not necessarily move it up or down.The fuel in the tank seat may be a bigger issue, but there is only a relatively small amount up the backrest, and the bit in the seat itself only vary's by about 4", and is a relatively small portion of the overall weight. I am confident that the total CofG variation will be well within +/- 3 inches.Also, you seem to be varying your argument. Sometimes you are saying that being within 3" is not important, and sometimes you are saying that it is not practical to develop a prescriptive requirement.You may well be might about the prescriptive requirement.In general, we would also require that the occupants centre of mass be near the thrustline, so that machines be insensitive to variations. This is probably overkill in the single seat case, where the machine can be tested with the owner as pilot. However in the two seat case, especially during training, pilot centreline (and event use of flat tanks) may be worth considering.As for "common sense", I learned many years ago that reality has almost nothing to do with common sense.The only reliable measure is accurate mathematics. Subsequent life experience has confirmed this. If you do the force vectors for varying occupant weight when their CofM is on the thrustline, and you will see what I mean.>> (c) ... a high C of G machine (or as it is incorrectly called - low thrustline), ...Since it is the relative positions of CofG and Thrustline that determine the PPO stability, how can one descrption be considered correct and the other incorrect?>>Power Torque over...which has a lower moment of inertia in the lateral plane. I recall one such accident caught on video (Ken Wallis I think) where the gyro torqued over under reduced "G".Could you define what you mean by Power Torque Over please?My guess would be that you are referring to engine torque?This would cause Roll sideways, rathing than pitching (bunt).Is that what you are saying? >>Tim McClureI can understand that it is possible for an experienced pilot to fly an unstable machine. But now that the theory is known, it is unnecessary. I have a 20 y.o. RZ500 motorbike - one of the most inherently, deliberately, unstable bikes around. I know how to hndle it when it gets a tank-slapper at 160km. But it could easily kill a beginner. I was lucky to survive the first couple until I learned the trick.If I was to buy a new bike now, there is no way I would tolerate such poor stability. Both the motorbike manufacturing industry and the gyrocopter manufacturing industry now have the theoretical knowledge they need to produce stable machines.People telling me CLT is unnecessary is like a bike rider telling me its OK to have the forks too steep and a small wheel. Absurd.And poorly thought out arguments like the ones I have seen in this article only push me further into the CLT camp.Gyro design has moved beyond "common sense" into the world of precise mathematical theory. Individuals now have three choices - Lead, follow, or get out of the way.S

[asra]

Oh, sorry. I was supposed to be positive. Here goes.We know how to build them properly. Its not even very hard. CLT, CLP (Centre line pilot)LVFT (low variation fuel tanks) 4WG (4 wheel gear), LWB (long wheel base). What else -How about Tandem with passenger right on CofG. Large stabilisers. Rudder in prop stream. Horizontal Stab out of propstream (unless you want a compensating effect for poor CLT) Long moment arm on stabilisers.Suspension! both springs and damping!Large diameter wheels. (Motorcross)Tall Mast. (Folding Mast)Torque compensating stabilisers in prop wash.All basic stuff, in either this or other industries. So we have a very bright future to look forward to.As long as we can agree that staying alive and not trashing the machine are important to continued flying, and the growth of an industry that produces better machines for us to fly.Hey Paul, are you putting any of these other considerations into the firebird?I wish I had money to invest...

[asra]

Originally posted by Firebird PaulJohn, if I may. If precession is involved, wouldn't the precession occur both left and right[?] Or have I missed something regarding precession[?]My guess would be this.Turning one way will prompt the rotor to pitch up.Turning the other way will prompt it to pitch down.Pilots have varying reactions to these effects, and will try to compensate, for one more than the other, and will thus percieve "turning" as being easier one way than the other.It might be worth trying some turns in which you also pull up or drop into it.Don

[Tim]

Lateral movement of the airframe does not cause any precessive forces in the rotor disc. The only slight force that comes into play is the momentum of the rotor mass trying to resist a change in direction, and because the Rotor C of M is above the rotorhead lateral pivot, this force is felt as a bit of side pressure on the stick. The Gyro would behave the same as it would it the rotors were removed and replaced with a lead weight of the same mass.CLT and Thrustlines are not the bottom line. The bottom line is Stability - no matter how it is achieved. If a particular gyro requires CLT to be stable, then so be it. A gyro with a thrustline offset of 600mm can be made to pass all the stability criterion if need be. The trouble is that the tail feathers would be so large that it would be impractical.Tim McClure

[asra]

[NiqueNaque]

Gavin,Wisely chosen words.Tim is a good read.Flying a gyro is fun and relatively inexpensive if you do it safely.CLT helps, stabilisers help, training helps, take all three.Cheers,Nick.

[asra]

Time to respond.... The thinking here seams to be that CLT is somthing new,its not.Anyone that has bothered to look at the early gyros of Bensen and Wallis,and before that with Cierva and Co, will see that its been around before most gyro pilots were even born.When Boyette and Beaty started messing with it again in the US in the late 80s early 90s others, including yours truly,started to take notice and jump on the bandwagon.It's not a "Fad" as some say but a fundamental principal of how to design a autogyro properly.M Barker

[asra]

Great post Tim. Stability no matter how it is achieved is the key. It seems to be easier to achieve the closer one is to CLT and with an effective stab. It is good that the Yanks won't accept prescriptive rules but rather a defined pitch stability test procedure. That leaves plenty of room for the innovators, who I believe are the backbone of most improvements to most things.Aussie paul. []www.firebirdgyros.com

[asra]

[asra]

hi there Gavin.Are you by any chance John's brother?? And thats not the John from this forum

[asra]

John as in Naracoorte SE of SA, NO. He's my cousin.

[asra]

No John as in peterborough. Where in SA are you??

[asra]

Meningie. If his last name is spelled Flavel then he's a relation.Flavel's are like Ar$#holes everyone knows one Gavin

[asra]

definately spelt the same way.