Aviomania's Agrinio Antics

[ckurz7000]

Chris, your only rotating on the bolt, theres no cyclic...

Yes, I know. In my experience the disc maybe moves a bit and I don't come out with my nose pointing straight down. But then you can't really tell what angle the disc is at unless you take a picture from outside the gyro.

But you can tell that you're doing it right when the stick does its semi-circular dance around to full forward.

Forget what I was saying regarding the direction of turn. I was just theorizing that the danger of a cyclic stall maybe a tad less going with the rotation of the rotor simply because the chassis turns left a bit more reluctantly than right (at least with the rotor going ccw when viewed from above and my 912).

-- Chris.

 

[Friendly]

An unstable gyro, one with propeller thrust line well above the CG and with insufficient horizontal stabilizer has all the requirements to become a rotary lawn sprinkler or yo-yo once the rotor stalls.

Also applies to gyros that rely upon rotor thrust to balance propeller torque. They can become roll axis yo-yos.

Chuck,
there has been losts of post on Thrust lines and center of gravity. Not much on torque roll. Would you start a new thread on this subject?

Nicholas ,
thanks for clearing that up. I have saved the video to my computer, I like it a lot.

 

[birdy]

David.. that depends on your Gyro. A HTL gyro will be as you described.. the engine is trying to put the nose down so you are using the rotor to keep it up.
Nik, TL orientation has no effect on roll.

With the genesis since the stick position is in the center and engine torque is effectively reduced, precession stall is avoidable especially with a light grip on the stick.
At wot attitude angle is the frame at wen your at WOT and 0 IAS?
A T tail centered in the prop will cancel out torque roll, but has no effect on the props gyroscopic resistance.
Short of a teetering prop, theres no other way of eliminating gyroscopic resistance from the prop.

A rotor with a stalled blade can flail around and do crazy things.
Bottom line: I don’t know what gave your blade straps a permanent wave.
Hmmmm, i hate not known.
i wouldnt have thought i stalled it bad enuff to do any damage, never mind flail about.
Not sure i woulda gotn away with it if i did.

But you can tell that you're doing it right when the stick does its semi-circular dance around to full forward.
Yes, if you float the stick, its all good.

chassis turns left a bit more reluctantly than right
This reluctance you feel is not related to the rotor Chris. Unless your bangn the stops, the only force the rotor can apply to the frame is along the axis of the tip plain. IOW, it cant impose any yaw effects.
The yaw effect your talkn bout is the prop discs resistance to directional change wen you stomp. [ gyroscopic]
Hard left at WOT and its easy, hard rite and it wants to dive. [ with a ccw 912 prop]
Its not a resistance against yaw, but a resistance against pitch. So wen you left stomp, its tryn to drive your nose down, and you have to consume alot of backstick to keep the nose up, maken the hole opperation feel slower and more energy inefficiant.
If your not sure wot im on about, do the same thing at idle.

 

[Aviomania]

David.. that depends on your Gyro. A HTL gyro will be as you described.. the engine is trying to put the nose down so you are using the rotor to keep it up.
Nik, TL orientation has no effect on roll.

I was not referring on roll... this is a comment on your description that the rotor is almost vertical when the gyro is at high nose up attitude when flying at minimum straight and level speed. with HTL the rotor disk is at higher AOA at the same frame attitude as compared to a CTL or LTL. ( all things been equal except TL). If you were meaning something else with your comment i did not understand you.


With the genesis since the stick position is in the center and engine torque is effectively reduced, precession stall is avoidable especially with a light grip on the stick.
At wot attitude angle is the frame at wen your at WOT and 0 IAS?
A T tail centered in the prop will cancel out torque roll, but has no effect on the props gyroscopic resistance.
Short of a teetering prop, theres no other way of eliminating gyroscopic resistance from the prop.

I thought we were discussing the minimum straight and level flight at WOT. If this is the case the airspeed is 10-12 MPH and the nose is 45* up. Gyroscopic frame reaction depends upon lots of things. The weight of the prop and its RPM ( plus other factor like props distance from CM etc.). the Ukrainian Prop is only 3.5 Kg (7.7 lbs).. not much gyroscopic effect compared to a warp drive. If the "Fan stops" again no Gyroscopic effect.

If you hard petal to the right at WOT then the gyroscopic reaction will be nose down and if to the left is nose up depending on prop rotation.

Bottom line is if the Gyro has all forces applied to to its CM ( very near) and balances out engine /prop reactions is much easier to handle than a gyro that depends on the OFFSET of all forces around its CM to maintain a balance. Not that you cannot perform aggressive maneuvers with an unstable gyro.. it just requires your skill and knowledge David to do them.

Other factor is the rotor blades and there ability to change there rotation path quickly. tip weighted blades that have light all up weight are perfect for this...

Mr. Ernie.... Your blades are the best i have tried on the Genesis Solo... thank you!!!!!! (i have tried 6 types so far)

 

[birdy]

I was not referring on roll...
I know, but i am.

 

[ckurz7000]

This reluctance you feel is not related to the rotor Chris. Unless your bangn the stops, the only force the rotor can apply to the frame is along the axis of the tip plain. IOW, it cant impose any yaw effects.
The yaw effect your talkn bout is the prop discs resistance to directional change wen you stomp. [ gyroscopic]

We agree completely on this, birdy. All I'm saying is that a peddal turn to the left -- apart from the gyroscopic effevt of the prop -- is a slower matter than when done to the right. That's a fact, at least in my MT03. So that when you are swinging the cabin around the jesus bolt in the direction of the slower side you are less prone to stall the rotor if you're not floating the stick completely. So it is the more forgiving way around since any residual cyclic input will be slower.

Not much of a difference but I wasn't trying to make a big point out of it. Sorry if it seemed otherwise.

-- Chris.

 

[birdy]

Not much of a difference but I wasn't trying to make a big point out of it. Sorry if it seemed otherwise.
Ah, now i savvy Chris.
And your rite, "if dun proper" also means you dont get a supprise sink/ bubble/ gust that can force sum cyclic before you can react, and taken your ' safest' option will minimise the risk.


Sorry Nik, ran outa time with my last short post.
I thought we were discussing the minimum straight and level flight at WOT.
Yes, we are.
But this comment;
If this is the case the airspeed is 10-12 MPH and the nose is 45* up.
has me confused.
If your frame att is at 45*, and your at WOT ina steady, slow S/L, wots holdn the nose up if your stick is centered??

 

[Aviomania]

But this comment;
If this is the case the airspeed is 10-12 MPH and the nose is 45* up.
has me confused.
If your frame att is at 45*, and your at WOT ina steady, slow S/L, wots holdn the nose up if your stick is centered??

a proper balance of forces. :whoo:

David if engine thrust is applied at CM and rotor thrust (lift) at CM there is no rotational force on the frame. All forces are applied at the same point.

in real life a very slight "stick forward" FORCE is needed ( with stick being somewhere in the neutral (center) position) because the rotor supports less weight (prop thrust is supporting some of the weight) and in the trim spring now "pulls" on the stick.

If i let go of the stick, the nose will rise another 5* or so, the speed will be reduced and the gyro will start to sink. Trading ALT with speed the gyro will recover to its trimmed speed eventually.

have a look at this video:
YouTube - Aviomania G1sa "Genesis solo" at Thiva aero club GREECE demo flight 1

at 2:20 -2:30 you will see a slow flight at WOT with the stick in the middle.

Get a broom stick and try to dance around will holding the stick vertical. If you hold it from its CM the stick will remain vertical, if you hold it anywhere else then the stick will need to change its position.

I have tried to clarify it as simple as i could.... not because i think you will not understand but for everyone to understand it.

 

[birdy]

Nik, if the prop thust is centered [ clt] and the stick is centered [ RTV behind the COM] why is the nose high?

 

[C. Beaty]

As Nick was explaining, Birdy, when there are no offsets and all forces act through the center of mass, even hanging on the prop at 12 mph, the stick is more or less centered. Even cave men figured that the ox should be hitched to the center of the cart.

The same rule also applies to propeller torque; compensating vanes in the propeller slipstream ensure that the airframe isn’t rolled to one side and relying upon rotor thrust to balance prop torque. No rotor thrust; no balance and over we go.

Stuff well known to Cierva in the 1930s.

 

[birdy]

I thought, if the stick is centered in a CLT machine, the RTV passed aft of the COM?

 

[C. Beaty]

If the stick is centered in a CLT machine and there’s no load on the tail, the rotor thrust line will pass exactly through the center of mass.

But that’s not exactly what we want. We want angle of attack stability and for that, the rotor thrust line must pass slightly aft of the CM.

There are several ways of accomplishing that.

A slightly low thrust line.

A downloaded tail.

A tail airfoil that has a slightly steeper lift slope than the rotor. In this case, the rotor thrust line can pass through or even slightly forward of the CM because an upward gust for instance, produces a greater incremental lift change on the tail than on the rotor, nosing the machine down and keeping it headed into the relative wind.

Lift slope is controlled by aspect ratio; chord to span. Ping-Pong paddles have shallow lift slopes because of low aspect ratios.

The bottom line is angle of attack stability.

 

[Aviomania]

David Mr. Beaty in his last post explains how the Genesis accomplishes its stability. We have some more tricks under our hat ( i am not giving details ). ... Just let me say.. the RT, tail position, size and angle gives deferent effects of desirable stability in deferent situations ( fast flight, vertical descend, high AOA at WOT, etc).

I do not have Mr. Beaty's ability to communicate and explain things.
( Mr. Beaty .. be prepaired... When i finally make it to the USA.. i will sit with you and you tell (teach me) everything you know :whoo: )

Imagine that you cut the outline on the Genesis out of a sheet of wood. You install a ball bearing exactly at the CM and then insert it on a shaft. If you now rotate the figure at any Angle and you let it there it will stay at that angle.

At low speed and hight power moving the stick on the genesis will change the attitude and then by centering it will maintain the attitude. On other situations it behaves deferent... in a vertical descend for example... it will want to point the nose down to return to its trim speed in a straight and level flight.

as i said before in real life the stick is within an inch from the center.... you can not have the perfect balance (pilot weight, fuel weight etc).... but more or less is at the center.

 

[Aviomania]

If the stick is centered in a CLT machine and there’s no load on the tail, the rotor thrust line will pass exactly through the center of mass.

But that’s not exactly what we want. We want angle of attack stability and for that, the rotor thrust line must pass slightly aft of the CM.
The bottom line is angle of attack stability.

a tail with the right position, size and angles can do this. with the RTV passing slightly aft and a tail that does its job... at any speed... any torque is balanced out ... most of it anyway.

 

[birdy]

--------------------------------------------------------------------------------

If the stick is centered in a CLT machine and there’s no load on the tail, the rotor thrust line will pass exactly through the center of mass.
Well there ya go, this SCG aint too old to keep learn new things.

Clears up a few things for me, thanx blokes.