That game of darts...

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John Boucher
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Re: That game of darts...

Postby John Boucher » Wed Nov 20, 2013 7:28 am

Thanks Eben, even with the differences you have noted, would a HS be able to be retrofitted to the SA model?
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Re: That game of darts...

Postby saraf » Wed Nov 20, 2013 8:17 am

Hi John,

Yes it could, and has been done......just to be taken off a couple of months later at the owners request......
Good instructors always speak well about all flying machines.
Bad instructors speak badly about machines they cannot fly.
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Re: That game of darts...

Postby Gompou » Wed Nov 20, 2013 8:57 am

Hi all

Saraf.
Nice post . Thanks' for playing the ball and not the man. Always nice to read and be informed about gyro's, and not personal differences.

Len
Sorry if it seems that I am attacking you in my post . I surely do value the input of hi time pilots. At that stage I regard your post of one that has value and to be informative regarding the RAF, seeing that you had nothing to gain by it or were the owner of one. I was in a decision making process which gyro to by. Even today I believe that that report was a honest report of a pilot with experience that I lack and it surely influence me to by a RAF. Today I can only thank you for it, because I have no regrets in doing so . As said to EB , always nice to read and be informed about gyro's, and not personal differences.




Steve SP.
I for one must agree with Rocket on this one. I don't think that you could compare accidents stats from countries where training isn't or was not mandatory when you build your own aircraft. Just consider the accident rate on any complex aircraft or for that matter rotorcraft if training wasn't mandatory. How many gyro pilots in South-Africa can say that they could get into a gyro with no training and safely fly it. I suppose accident stats would look horrifying.

Bladerunner do however ask a relevant question regarding the fatal accident stats regarding the RAF in the past 15 years.

And NO,I don't want Len to answer it.

I know the answer for SA, but can you perhaps help us here on stats for the whole world. I certainly think that only a fool will try to fly any gyro without training today, so a count for the last 15 years will definitely be a indication of the mortality rate of the RAF for prospective buyers.

Nice photo's of G-IRAF, but there are no Rotor Stabilator fitted to it like in the models that are now built by the Mocke's. I personally have flown with Eben in ZU-DKW with nearly 800 hours on the clock and only with the Rotor Stabilator. It is the one in front in his avatar .I suppose they must be doing something right.

Regarding the Bcar T status of the RAF . It seems that the human mind is not as reliable as the computer \internet.
Pardon me if it seems like implying someone, but if the answer in this post was not correct, please enlighten me.

viewtopic.php?f=20&t=13145

However, if you are interested in gyro's, read this, and then form your own opinion about gyro's that do apply to the Bcar T standard.

https://www.caa.co.uk/docs/33/CAP643%20 ... 013%29.pdf

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Re: That game of darts...

Postby Steve_SP » Wed Nov 20, 2013 10:15 am

Hi


The UK CAA Type Approved Gyrocopter list is a short list


http://www.caa.co.uk/default.aspx?catid ... 8&gid=1562


look at the heading

Gyroplane Type Approval Data Sheets


Only two manufacturers have qualified - the big two - you'll recognise the approved models.


Note that there are no examples of the SA RAF M2 in the UK ( why ? - the RAF 2000 had sold well in the UK originally ) - we do have RAF 2000 still flying here, all are older H2 models and all have had to comply with various CAA mods.


Regards


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Re: That game of darts...

Postby PTKay » Thu Nov 21, 2013 2:24 pm

saraf wrote:...
To start: Do you fly the rotor disk or do you fly the cabin? Considering that the rotor disk is your wing and you manipulate this wing by shifting the weight on a pendulum arm, where do you propose to put the “feathers” you speak of?...
I think you have exposed yourself here.

If you still believe that a gyroplane is a "weight shift control aircraft", like trikes,
you have shown the enormous scope of your ignorance.
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Re: That game of darts...

Postby Vertical Tango » Thu Nov 21, 2013 10:15 pm

If you still believe that a gyroplane is a "weight shift control aircraft", like trikes,
you have shown the enormous scope of your ignorance.
PTKay, very unnecessary comment.
The conservatives are not interested in different designs. If it is not like my gyro, it cannot be good...
The RAF might not be everyone's cup of tea, but what Eben says has its merits. The RAF fuselage has no aerodynamic controls therefore could be considered a dead weight hanging below a rotor disc. However not all that dead because it is linked to the disc via a control stick. The disc is very much like the wing of a trike and flies by itself. The dead weight of a trike undercarriage + pilot has also no aerodynamic control. Other makes of gyros do have the HS which is an aerodynamic control in forcing somewhat the direction of the fuselage only, sometimes in opposition to the inputs to the disc. This is why the RAF is very unique and I always said that the conflicts of opinions are based on the fact that we want the RAF to behave 100% like other gyros. Why don't we impose the same from a R22 ? I think that the RAF sits in its own category, hence the rigorous and different training that the Mockes have developped. I think that the stats in SA prove that the machine is safe if in the hands of a properly RAF trained pilot.
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Re: That game of darts...

Postby saraf » Fri Nov 22, 2013 10:05 am

Hi PtKay.

Thanks for the post. Lets make this informative for all to learn......

Maybe we should look at what controle systems is incorperated into which aircraft, direct or reversed?

Lets say both microlight ( weight shift ) and Gyro has a direct stick attachement to the flying surface? What is the differance?

Regards
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Re: That game of darts...

Postby Learjet » Fri Nov 22, 2013 11:15 am

saraf wrote:Hi PtKay.

Thanks for the post. Lets make this informative for all to learn......

Maybe we should look at what controle systems is incorperated into which aircraft, direct or reversed?

Lets say both microlight ( weight shift ) and Gyro has a direct stick attachement to the flying surface? What is the differance?

Regards
Ebie, I think what PtKay is (correctly) pointing out is the mistaken assumption that the gyro disc attitude is changed by means of weight shift (i.e "pulling or pushing up, down,left or right etc.as per a trike wing - albeit on a gyro via the control linkages). This is not the case.
It is gyroscopic precession (not weight) which changes the disc attitude - i.e. the pilot input (via the control linkages) merely changes the rotor blade Angle of Incidence and gyroscopic precession (and thus the disc attitude change) occurs 90' degrees later.

wiki explains it quite nicely:
If the rotor disk is to be tilted forward (to gain forward velocity), its rotation requires that the downward net force on the blade be applied roughly 90 degrees (depending on blade configuration) before that blade gets to the 12 o'clock position. This means the pitch of each blade will decrease as they pass through 3 o'clock, assuming the rotor blades are turning CCW as viewed from above looking down at the helicopter. The same applies if a banked turn to the left or right is desired; the pitch change will occur when the blades are at 6 and 12 o'clock, as appropriate. Whatever position the rotor disc needs to placed at, each blade must change its pitch to effect that change 90 degrees prior to reaching the position that would be necessary for a non-rotating disc.
To see this in effect:
on the ground, position the rotor crosswise to the cabin. i.e rotor blades at 9'o clock and 3 o'clock
By pulling back on the cyclic you will notice that the advancing blade (not the whole disc!) tilts up (increasing Angle of Incidence) - so the control input is thus taking place at the advancing blade's 3 o'clock position, but...
Gyroscopic precession only occurs 90' degrees later - so at 12 o'clock position is when (and where) the change in overall disc attitude (AoA) occurs.

So it's a case of gyroscopic precession input (not weight shift) which is bringing about directional change. vhpy

Dave
Last edited by Learjet on Fri Nov 22, 2013 6:36 pm, edited 1 time in total.
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Re: That game of darts...

Postby Gyronaut » Fri Nov 22, 2013 11:48 am

Learjet wrote: ... Angle of incidence
=D*

Agreed. PTKay is correct.
Changing the Angle of attack/incidence alters the plane of rotation & the fuselage follows.
Not weight shift.
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Re: That game of darts...

Postby saraf » Fri Nov 22, 2013 12:45 pm

Hi Dave,

100% correct no doubt in that...but, ...controle wise there is in my eyes no differance as both are pendular aircraft.

Regards eben
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Re: That game of darts...

Postby M I Claase » Fri Nov 22, 2013 4:58 pm

To support SARAF comments regarding weight shift. Take a hellicopter (which i think was refered to above as there is a big difference), make a bracket attachment,that does not interfere with rotor movement for the rotors, and hang it so the rotor centre is secure. Move the controls and you will find the anle of attack off the rotors will move up and down. This tells me i am controlling the rotor. Now take a gyro and do the same securing the rotor and hang it. Move the controls and you will find the cab is moving and not the rotor. This, i thinks, is what Ebie is trying to explain. I remember a old gyro that had a fixture from under the rotor with a handle in front off the pilot same as with a trike. Controls was same as trike, pushing forward (moving weight backwards) for up and pulling back (moving weight forward) for down. Todays gyros have a more advanced contol arm and link system which reversed the stick input to forward for down and back for up, but the weight shift principle remains the same. A gyros rotor blades are set at a fixed angle which can not be altered and when spinned at speed creates lift. The the only way to change the angle is to change the direction of the airflow moving over it. The only way this can be done by is to move the C of G into the direction of intension, which means shifting the weight hanging in the centre off the rotor into intended direction being up, down, left or right forcing the airflow angle over the blade to change. (Dont believe me, go fly your gyro and you will notice if you push stick left, moving weight left you go left!! sommer do this while it is hanging and you will see for yourself the cab wants to move left causing the C of G to move left!!) If my theory is wrong please tell me how you control direction other than shifting weight. Remember the GYROscopic effect created by the big rotors resists changes out off orbitting direction, ( like having the rotor fixed when doing the hang test) and can only be forced to alter its orbit with a weight enforcing such a change.Shoot me down if you differ.
Hereby supporting Ebies comments regarding tailfeathers, which in my opinion will only have a influence if there was no rotor involved.
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Re: That game of darts...

Postby Learjet » Fri Nov 22, 2013 7:19 pm

M I Claase wrote:Take a hellicopter (which i think was refered to above as there is a big difference), make a bracket attachment,that does not interfere with rotor movement for the rotors, and hang it so the rotor centre is secure. Move the controls and you will find the anle of attack off the rotors will move up and down. This tells me i am controlling the rotor. Now take a gyro and do the same securing the rotor and hang it. Move the controls and you will find the cab is moving and not the rotor...
Rotor directional control in helicopters and gyros is brought about by gyroscopic precession (and not weight shift) and this is due to change of rotor AoI 90' degrees before effect.

I think you'll be surprised to find that if you conduct your hang test with the rotors in the 3 & 9 position as described in my post - you will in fact see that the rotor blade "pitch" (or more correctly, the Angle of Incidence) changes - in exactly the same manner in which you describe the helicopter pitch changing.. :shock: This is exactly what initiates the gyroscopic precession which manifests 90" later. A gyro may have a solid-hub bar, (and no swash plate as in a helicopter) however the rotor angle of incidence "pitch" does indeed change thanks to the gimble and cyclic input. vhpy Try it for yourself vhpy

The other common misconception is that gyros (and I'm talking about all gyro types!) pendulum freely below the rotor. This would only be (partially) true if there were no control linkages and a hand holding the cyclic. The instant that we apply control on the cyclic we are restricting or negating the free-pendulum effect. Also, scientifically, a pendulum requires a static fixed point - which a rotor disc is not... ( but I"ll save this explanation for a rainy day other than to say that try swinging a pendulum from a curtain rail in the same direction as the ring is able to move on the rail and the result will be not what you expected (**) )

A more familiar analogy may be the steering wheel in your car with its "free-steering" front wheels. Place a hand on the wheel and the free-steering is immediately diminished. Ditto the outboard engine on a speed boat example. It can be asserted that the speedboat skipper is "flying the outboard engine" and his control inputs in turning the engine left or right is directly controlling the direction of the speedboat (which has no rudder of its own) and is just being pushed along for the ride. Despite the fact that the outboard engine is free to swivel on the transom - the control linkages or the hand on the tiller immediately diminishes the engines inherent free swiveling or pendulum capability, and imparts a force on the hull and vice versa. It's also more than apparent that despite having no input control surfaces of its own, the boat's hull and hydronautical design plays an integral part in the stability, directional control, or performance of the boat. The same principle applies to the aerodynamic design of a gyros fuselage (any gyro). That we are "flying the disc" in isolation of effects on and from the fuselage is a misnomer. The fact that a gyro can fly a circuit using only tail rudder for sufficient directional control contradicts this entirely. :wink:
M I Claase wrote:To support SARAF comments regarding weight shift. I remember a old gyro that had a fixture from under the rotor with a handle in front off the pilot same as with a trike. Controls was same as trike, pushing forward (moving weight backwards) for up and pulling back (moving weight forward) for down. Todays gyros have a more advanced contol arm and link system which reversed the stick input to forward for down and back for up, but the weight shift principle remains the same.
(**) (**) (**) oh vey! :roll:

You are referring to the old Bensen gyro glider with the T-bar control.
image.jpg
image.jpg (14.95 KiB) Viewed 6415 times
I know its hard to believe from looking at the picture and the simplistic T-bar control - but it's NOT a weight shift. :shock: When pushing the T bar forward, the angle of incidence ("pitch") of the advancing blade in the 3 o'clock position would exert a control input (lift) which by the law of gyroscopic precession manifests itself 90' later - and the disc angle of attack changes accordingly. If you think that this is being brought about by "pushing the disc" to move weight backwards - then your gyro instructor probably never demonstrated to you the effect of gyro precession on a spinning bicycle wheel.

Watch this little bicycle wheel gyroscopic effect demo - and consider whether you'd be able to overcome the gyroscopic inertia of a spinning 30ft rotor disc with a simple unassisted push, pull or using a shift in weight!?? vhpy

http://m.youtube.com/watch?v=c1F9t6TV4qE

I'm probably wandering off-topic here into the physics of flight - but maybe that's not such a bad thing. vhpy No matter what we fly, the sky is the same colour blue for all of us. puff
Last edited by Learjet on Sat Nov 23, 2013 12:22 am, edited 1 time in total.
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Re: That game of darts...

Postby PTKay » Sun Nov 24, 2013 2:00 pm

Vertical Tango wrote:
If you still believe that a gyroplane is a "weight shift control aircraft", like trikes,
you have shown the enormous scope of your ignorance.
PTKay, very unnecessary comment.
.... The disc is very much like the wing of a trike and flies by itself. The dead weight of a trike undercarriage + pilot has also no aerodynamic control. Other makes of gyros do have the HS which is an aerodynamic control in forcing somewhat the direction of the fuselage only, sometimes in opposition to the inputs to the disc. ....
This is a completely false and utterly unfounded concept.

In reality, the gimbals on the rotor is no "hanging point",
but a measure of controlling the rotor.

By tilting the rotor forward you increase the angle of icidence
of the advancing blade and lower the AoI of the retreating blade.

This tries to tilt the rotor to the side with the precession force, acting
1/4 turn (90deg) after the force applied to rotating body to tilt the rotor forward.

See: http://en.wikipedia.org/wiki/Precession

Gyroscopic precession also plays a large role in the flight controls on helicopters.
Since the driving force behind helicopters is the rotor disk (which rotates),
gyroscopic precession comes into play. If the rotor disk is to be tilted forward
(to gain forward velocity), its rotation requires that the
downward net force on the blade be applied roughly 90 degrees
(depending on blade configuration) before that blade gets to the 12 o'clock position.

This means the pitch of each blade will decrease as they pass through 3 o'clock,
assuming the rotor blades are turning CCW as viewed from above looking down at the helicopter. The same applies if a banked turn to the left or right is desired;
the pitch change will occur when the blades are at 6 and 12 o'clock, as appropriate.
Whatever position the rotor disc needs to placed at,
each blade must change its pitch to effect that change 90 degrees
prior to reaching the position that would be necessary for a non-rotating disc.


Please, do revise your understanding of the way gyroplanes fly, before it is too late!!!
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Re: That game of darts...

Postby Vertical Tango » Sun Nov 24, 2013 6:43 pm

PTKay and Learjet, we all know the theory of gyros and rotor blades in gyrocopters. We would not have passed our exams if not.
It is just a discussion and immediately it has to get out of hands.
No wonder why so few post their thoughts as they are so sh.. scared to be bombarded by the fundis.
If you dare ask a question, the only way is to apologize profusely first for being an ignorant and then you will taken under someone's protection and good advice.
Something has to change... :roll:
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Re: That game of darts...

Postby THI » Sun Nov 24, 2013 7:48 pm

I'm clearly reading a different thread...
Last edited by THI on Sun Nov 24, 2013 8:01 pm, edited 1 time in total.

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