Aerodynamics of Gyroplanes, a report by Glasgow University.

Pilot Pete

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Hi all,

This is a link to the long awaited CAA technical paper produced by Glasgow University.

Please note the copyright notice on page 4 before making references or copies.

Acknowledgments to all the contributors of the report. To numerous to list here, but are listed within the report.

http://www.caa.co.uk/CAAPaper200902

Regards
Pete
 
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Thank you, Pete, for the link. However, I remain very skeptical about the results of a stability study that neglects the airflow deflection by the rotor on the HS. In my opinion, it's same thing as studying the flaps effects on a FW, just without wings !
 
Did not find this light reading. Struggled and skipped through it. A lot of it way over my uneducated head.

Delighted that it has been done and now available, interested to hear comments from our resident gurus, though they are probably familiar with the contents and have commented already.

Find it confirms much of what has been said on the forum, 288-297 of most interest to me.
 
CAA Introduction Page 2: "The report also concludes that horizontal tailplanes are largely ineffective in improving the long term response of pitch dynamic stability (phugoid mode)."
I regret that the paper CAA focuses on the phugoïde response before becoming interested in short-term phenomena. On the contrary, previous tests shows dangerous phénomenon (Figs 11-5 and 11-6): Approach dangerous flapping stops and unexplained increases to rotor rpm: "a forward stick input is applied which gives 4 degrees forward shaft tilt. The immediate effect is for the nose to pitch down to -20 degrees, airspeed to increasefrom a nominal 60 mph to around 75 mph, and most surprisingly, rotorspeed increases dramatically from around 360rpm to 450rpm"
"most surprisingly"... However, the lack of interest for this phenomenon persists. Instead here, CAA and Glagow University worry blade flapping at Vne, and discovered that it is better to center the blade 25% chord, as everyone knows since 1930! Very disappointing for me.
 
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They have been in the past but then people forget, I suppose.

Notice the extreme angle of engine tilt, necessary for proper thrustline/CG relationship due to massive rotor system. Knowledge of proper thrustline arrangement preceded Glasgow by a few years.
 

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The Glasgow report epitomised the British way of doing things..........pay out loads of money to find out what the rest of the world already knew.
 
We here in Oz land this year are being asked to do the double hang test on all non factory machnie before the registration is renewed for next year, and it is being sort of based on the info from this type of report, this way people get to know where their machines cog is and can change it to get a safer machines.
Mostly because there have been 3 deaths over here in the last X time, most if not all were htl machines, and CASA(FAA) are not happy.
It going to be the first mass change in requirements for reregistration, in the world i think, the rest of the world will probably follow so brace yaself :)
 
:whoo: that's greaat news , got to give CASA a gold star there, it looks like finally the "winds of change" are finally taking hold, would like to see this everywhere !!!

Tony
 
But there are no requirements to change your machine if it is HTL as i understand it, is that correct Mark? Will there be in the future?

Cheers,
Trent
 
But there are no requirements to change your machine if it is HTL as i understand it, is that correct Mark? Will there be in the future?

Cheers,
Trent
SHHHHH not yet but wait :lol:
 
Pete,

thank you very much for this link! The report is invaluable as a data source for anyone trying to delve into gyro stability. Now one can calibrate ones own mathematical model aginst the measured data.
Including aeroelastic effects into a model is a daunting task but luckily the report states that balancing the blade forward of the 25% chord will reduce blade torsion (as Chuck pointed out in a thread about half a year ago) so the need to tackle this problem does not seem to be immediate.

All in all one really great find!
(And one that I will have to work through for quite some time)
 
The report is invaluable as a data source for anyone trying to delve into gyro stability. Now one can calibrate ones own mathematical model aginst the measured data.
Are you sure, Juergen? I am not able to follow complex calculations of the author. Yet I wonder about the validity of the results of longitudinal stability, with the erroneous data following: (Appendix 2: Configurational Data)
Izz: 4425 kg.m2 (In reality, probably ten times less !)
Rotor blade: 8.5 kg (In reality, probably two times more !)
Flapping inertia: 51,6 kg.m2 (In reality, probably four times more !)
Nominal distance from the CG hrust line: 0.027 m (In reality, probably ten times more !)
These data are fundamental to the dynamic stability, is not it?

Jean-Claude
 
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I'm refering to the values of force and moment coefficients measured in the wind tunnel. These would have to be matched by a mathematical model.

(In fact, in my opinion, closer to 442 kg.m2, 18.5 kg, 200 kg.m2, 0.27 m)
The mass of Martin Hollmans Sportster blade is about 10kg, why should a more modern blade weigh in at 18.5kg? If 8.5kg is correct than 50 kg.m2 is reasonable. If you assume the teetering rotor to be one rigid beam with a mass of 18.5 kg for flapping than the inertia is m*l^2/12 which gives 84.4 kg.m^2 for a rotor diameter of 7.4 m. I have no idea how you arrive at 200 kg.m^2.

If your figures are to represent the quantities above the quoted line I'd be quite surprised if the inertia of the whole gyro (442 kg.m2) is just twice that of a single blade (200)
 
The mass of Martin Hollmans Sportster blade is about 10kg, why should a more modern blade weigh in at 18.5kg?
Juergen, I consider Appendix 2 (page 1) Data Configurationnal VPM M16 Gyroplane.
18.7 kg / blade (weighed by Xavier Averso), not 8,5 kg. Reducing the weight of the blades has never been the number One goal. Too much light gives too coning.
I have no idea how you arrive at 200 kg.m^2.
8,53 m (dia) and 18,5 kg give exactly 224 kg.m2 to the rotor when the mass repartition is homogen.
I'd be quite surprised if the inertia of the whole gyro (442 kg.m2) is just twice that of a single blade (200)
No single blade but both. You should not be surprised: The blade mass, launcher, vertical mast, swash plate, rear passenger, fuel, and everything is under the rotor axis are a negligible effect on yaw inertia.

And Magni data give 11" HTL. It's 0,28 m not 0,027 m.
Jean Claude
 
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As I pointed out in #16 the inertia for a teetering rotor is m*l^2/12. With the 18.5kg and a diameter of 8.53m this gives 18.5*8.53^2/12= 113 kg.m^2, I still have no clue how you arrive at 224. It would be quite helpfull if you would post the formulae you use to arrive at a figure, not just the figure. It would then probably be very easy to see where the error originates.

In appendix 2 page three the rotor data for the Montgommerie Parsons gyro are:
radius=3.81 m;
mass = 17.255 kg;

this gives 17.255*(3.81*2)^2/12= 83.4918kg.m^2, which is exactly the value given on this page.
 
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I wonder about the validity of the results of longitudinal stability
The flapping inertia enters the stability derivatives only through the Lock number. It has been shown in naca report 716 that changing the Lock number from 15 to 25 alters the flapping parameters by just 1.3%. An error in blade inertia is therefore not critical for a stability calculation.
Pitch and yaw inertia are of the same order of magnitude. I therefor assume that the value of 4425 is really a typo. An error of an order of magnitude is usually quite easy to see in the results. If you suspect that the derivatives are wrong you could check them using the approximate formulae given by Bramwell.
 
the inertia for a teetering rotor is m*l^2/12.
.
Juergen, I do not get the same equation as you. Inertia rotor = 2*m*l^2/12. This is the result of my demonstration. Where is the flaw?
On the other hand: Montgommerie Parsons blade weight 17.5 kg (7.4 m). Magni M16 blade 8.5 kg (8.5 m) is not consistent.
 
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