The challenge of gyrocopter design.

[mnowell129]

Having studied for some time and designed and test flown my gyrocopters for the past few months I came to a tiny amount of understanding about gyrocopter design. This is the beginning of a thread intended for future designers that I intend to discuss the challenges of gyrocopter design that I have encountered. It may generate a discussion among experienced designers as well and that would be welcome. According to David Ramsey this is part 1 of "the book of mickey". I thought I would start with some basics. A rotor in autorotative forward flight with coning is diagrammed. The rotor in side view and top view is shown. Clock wise (from the top) rotation. The "V"s are local air velocities. Vf is the forward speed but it is drawn backwards since this is what the blade "sees". Note that the rotational air velocity vector is drawn backwards to the rotation because that is what the blade "sees".
In side view is the rotor with coning with Vf resolved into the parts down the blade and perpindicular to the blade. The part down the blade does nothing to change the lift of that blade. The part perpindicular to the blade has the effect of increasing the local angle of attack and local velocity of that blade. note that the forward blade has a bigger increase than the backward blade due to coning. If the blades were straight the increase would be the same on both.
On the top view the left blade sees the Vr+Vf, the right blades sees Vr-Vf, creating the asymmetric lift problem.
There are two ways to resolve the asymmetric lift problem (ALP), feathering or flapping. Feathering and flapping are BOTH forms of cyclic pitch (more later).
Either one or both can be used to resolve ALP due to forward flight differences.
Here lies the first great gyrocopter challenge. Flapping cannot be used to resolve the ALP due to coning. If flapping were used to resolve the coning induced lift asymmetry, the forward blade would flap up on the right and the back blade would flap down on the left. The rotor disk would then be tilted to the left by some amount. The rotor always produces a force perpindicular to the plane formed by the rotor tips, called the tip path plane (TPP). So if the TPP is tilted left a left roll is created that must be trimmed out to fly level. This has to be done with feathering. This is accomplished by either shaft tilt feathering or swashplate type feathering. The effect being the same. The blade in front is pitched down as it crosses the front, the one in back is pitched up, this keeps the rotor level. (In my models I make the head rigid with very little coning, thus very little roll trim is needed and it changes very little with airspeed.)
So here is the first great gyrocopter challenge. If you build in flapping hinges to alleviate the forward motion ALP you allow more coning angle to develop. The higher coning angle requires roll trim to stop the coning induced ALP. Further, the faster you go, the more roll trim is required. In fact the forward flight speed becomes limited by running out of roll trim! This is also true of helicopters! On the other hand going faster speeds the head up, causing it to flatten out, reducing coning. The question becomes does the rotor speedup that reduces coning and therefore reduces the roll trim needed end up being more than the increased effect a higher forward speed on coning creates that increases the roll trim needed!!!! Obviously some models will favor one vs the other and is related to the rotor speed, flight speed and flapping stiffness....
First frustrating outcome : Fixed rotor head gyros with coning and shaft tilt to correct for coning are only usually trimmed at one airspeed. If this is takeoff speed then cruise is wrong, if this is cruise speed then takeoff speed is wrong. This is frustrating indeed. What does this lead to? Hand launches right into cruise speed.

The great compromise is just enough flapping to relieve forward motion ALP, but no so much as to allow so much coning that you run out of roll trim....
First conclusion : coning is bad, flapping hinges aggrevate coning.
......
First design choice : Roll cyclic either by shaft tilting or swashplate is probably a good idea, even if you don't use pitch cyclic....so you can maintain roll trim at multiple airspeeds.

[mnowell129]

section 2...
This is a diagram of flapping and feathering. The goal is to reduce the asymmetric lift due to forward flight. We are looking at the left side of a clockwise rotating rotor, moving forward to the left. The blade in the middle is the left hand advancing blade that recieves the sum of the forward velocity and the rotating velocity. This gives it more lift than the retreating blade. We must reduce this lift (and conversely increase the lift of the retreating blade) to achieve balance.
Reducing lift can be done two ways 1) slow down 2) reduce angle of attack. Obviously slowing down the blade at one spot in the circle is not possible. So we must reduce the angle of the attack of the advancing blade and increase the angle of attack of the retreating blade. Since this increase/decrease is zero at the back, max increase at the left side, zero again at the front and max decrease at the right, the pitch is varying around one blade cycle. Hence the term cyclic pitch. Asymmetric lift is removed by cyclic pitch. No one has invented another practical way to do this.
There are two ways to achieve cyclic pitch to remove the asymmetric lift, flapping or feathering. Both achieve the same result of reducing the local angle of attack of the advancing blade.
There are three sets of rotors in the diagram. The top is the rotor with no flapping or feathering. The advancing blade sees the same angle that the retreating blade sees, the same as the blade in any position. But we know the advancing blades sees a higher airspeed and must be pitch reduced to remove the difference in lift.
In the second rotor we allow the rotor to flap along the dotted line. The airflow that the blade sees is now relative to the flapped up dotted line. In other words the blade is climbing as it goes from the back to the front. As the blade passes through the left hand position its angle is no longer +a but is now -b. I have exaggerated the angles to show them better but the effect is the same. The blade, being allowed to flap up, sees a less positive angle of attack and thus does not attempt to climb even further in front, creating an increasing nose up condition. The retreating blade is descending into the airflow down the dotted line. It sees an increased angle of attack and thus more lift, preventing it from trying to flap further down adding to the nose up pitch that would occur with forward motion.

In the third rotor we limit the flap but we mechanically feather the blade in a cyclic manner. Feather means to tilt the blade on an axis down the length of the blade. We can do mechanical feathering by tilting the shaft ("direct control") which we will see later is in fact mechanical feathering or so called cyclic pitch, or by a feathering spider mechanism with a hollow shaft, or by a swashplate mechanism. No matter what mechanical means is used it still results in mechanical cyclic feathering being applied to the blade. Whatever the mechanism used the result is the same. The advancing blade is mechanically feathered so that it sees the same -b angle of attack that would have been produced with flapping.

(Aside: Delta three hinging is used to reduce the amount of flapping needed. I will deal with this as a seperate topic. Delta three actually performs automatic mechanical feathering as well as flapping.)

Important result :
Flapping and feathering ("cyclic pitch") have the same effect on the advancing/retreating blade in balancing asymmetric lift differences due to forward flight.
Important result:
Cyclic Pitch/Feathering provides asymmetric lift difference balancing without flapping thus has a more nose down rotor plane. This gives more tail clearance. This also results in less drag, because as you will recall the force vector is perpindicular to the tip path plane. The flapping alleviated solution is tilted further back resulting in more aft rotor thrust, and therefore more drag.

Important design consideration:
Feathering/cyclic pitch allows a more compact model ( less tail clearance needed), reduces the coning thereby reducing the roll trim needed for forward flight and requires less power to fly. As a non insignificant side benefit mechanical feathering can be used to directly control the rotor, not just trim out asymmetric lift due to forward motion and coning.
To the negative, feathering is more mechanically complex to build.
On the whole, the advantages of mechanical feathering usually outweigh the disadvantages.

The next question is what are the ways to perform mechanical feathering?
There are 4 common ones, shaft tilt, pitch spider, rotor servo flap and swashplate. They all are used to mechanically feather blades in a cyclic manner.

This brings up the issues of controllabilty and stability...
I guess that will be the next ramble...

If you are getting any benefit from my ramblings, please post something to that effect. This will be much more fun for me if I know that at least one person is benefitting from me sharing what I have learned....

[David A Ramsey]

Just got back from a forced vacation to Hawaii. My wife had to yank me from my hallowed basement, kicking and screaming. In the hotel bedroom night table I found that the Gideons and the Hindus were there. Humm. I went right down to the hotel desk and shouted; Where's the Book of Mickey??????

Informative and detailed. Thanks.

David

[mnowell129]

Originally Posted by David A Ramsey

Just got back from a forced vacation to Hawaii. My wife had to yank me from my hallowed basement, kicking and screaming. In the hotel bedroom night table I found that the Gideons and the Hindus were there. Humm. I went right down to the hotel desk and shouted; Where's the Book of Mickey??????

Informative and detailed. Thanks.

David

we gotta meet sometime..
Are you coming down for the autogyro fly in Feb 24,25th?
I'll keep going. ...

[David A Ramsey]

Would be an honor to meet you. I'd like to make the Gyro Fun Fly, but unable to this year.

Prior to your input, much of my autogyro imformation was from "autogyro.com". As helpful as that was it didn't cover recognizing the myriad of problems, solutions, cause and effect. Please go on.

[mnowell129]

Originally Posted by David A Ramsey

Would be an honor to meet you. I'd like to make the Gyro Fun Fly, but unable to this year.

Prior to your input, much of my autogyro imformation was from "autogyro.com". As helpful as that was it didn't cover recognizing the myriad of problems, solutions, cause and effect. Please go on.

Will do.
I want to give credit where it is due. The material organized and presented on autogyro.com is very helpful, a tremendous effort and very unselfish in its presentation. The amount of work represented in design and experimentation is huge and not to be taken lightly. So my discussion here is not meant to diminish that work in any way. The difference is that much of the information presented there is very practical and the result of real experimentation. It is difficult however to use that form of information to make an educated guess as to what is right or wrong with something, it is more of report of what works rather than a predictor of what to do even though there are some guidelines on the site. My goal is to approach the topic from a theoretical perspective with the goal of establishing some way to steer a new design so that it will be successful. I believe if one understands the various forces and problems involved, then one is better able to make design choices and is more aware of the consequences of the design choices they are making. I believe that this understanding was vital to my success and may benefit others. As an example, I knew I could make a PT gyro/Gyro Schtick/ECDC type autogyro fly. But knowing that the direct control head creates very high servo loads ahead of time guided me into another form of control for my design that I wanted to use pico servos on. There are only two other real choices 1) A hollow shaft with pitch spider or 2) a swashplate and resulting stuff. My plan for development was to learn to fly a gyro first and continue to develop once I had a working platform and flight skill. THe hollow shaft spider method is something I am now working on that I will add as the single unknown to my already proven G3PO platform. I chose #2 because I knew it would work and get me in the air and because the parts were cheap, available and required no manufacturing on my part. In the process I sorted out general layout, landing gear setup, ground handling, tail requirements, power requirements, CG sensitivity, tractor vs pusher arrangements, and I learned to fly gyrocopters. From an experimental viewpoint it has been highly successful and I am now much better equipped to do the spider control version...

I'm hoping that I can explain the reasons that lead me to my conclusions and my design with the hope that a theoretical understanding of the problems will let other gyro designers make good choices in what they are building rather than just guessing....
mickey

[mnowell129]

Cyclic, version one.
Having determined that cyclic is probably a good thing to use in the autogyro we go about implementing it. The first obvious and simple choice is to tilt the shaft on which the rotor is rotating. The picture shows a side view of a four bladed rotor in the level flight condition in red. In green is the rotor if we were to gimbal the shaft and try to tilt the shaft backwards. What would happen would be that the advancing blade, the one on the left where we can see the airfoil, gets an increase in local angle of attack (LAOA) proportional to the shaft tilt. The blade on the other side decreases in LAOA, the same. The two blades fore and aft get tilted up or down but don't change in pitch. If we were to turn the rotor around slowly we would see that the front and back blades as they turn would increase/decrease in angle as they approached the side positions and then return to the nominal settings back at the front, when measured against the original steady state rotor plane.
This is very important, the forces are too high to instantly change the rotor shaft like this, so the change in pitch at the sides requires very high forces to overcome the centrifugal forces in the fore/aft blades, essentially causing them to bend to allow the shaft tilt to take place. In reality this is basically impossible with stiff rotor blades turning at any kind of rpm. Further even if you could force the pitch into the side blades and force the fore/aft blades up and down because the rotor is fairly rigid it would precess at something less than 90 degrees. A gyroscope precesses 90 degrees out of phase only when it is not constrained. If you add stiffness to the gimbal the precession angle gets smaller. For rigid rotors this angle may be as small as 65 degrees. What this would do is when you put in an up elevator command you would get rotor precession 65 degrees later which would give you 2/3 up command and 1/3 right roll command. Helicopters have to deal with this problem too and the solution they use is to turn the upper part of the swashplate to match the non 90 precession angle.
In any event this solution generates way too high of control forces to be of value. The next thing to try is the bottom diagram. The blades are hinged allowing them to pivot in the flap direction (flapping hinges). Now when the shaft is tilted up the left blade can get its increase in pitch and the fore aft blades don't have to be lifted to accomplish this. However, then hinge is usually at some distance from the shaft, called the flapping offset. As you may be able to guess from the diagram, because of the flapping offset as you tilt the shaft, the fore and aft blades are pulled in a tiny amount, and are no longer lined up with each other. They try to pull the hub back flat due to centrifugal force. This is bad because this force tries to flatten the hub out against the control input so the servos have to overcome this force. This is why so called "direct control" heads require heavy duty servos, they are carrying the centrifigal load of the blades during control inputs. Note that after a few revolutions the cyclic pitch applied to the left and right blades as they come around has forced them to precess up and down at the front and back and the whole rotor system is now realigned with the shaft which is now pointed in a different direction. Because the thrust is perpindicular to the tip path plane the thrust now doesn't line up with the aircraft CG anymore and goes in front of it. The coupling of the rotor thrust ahead of the CG now causes a pitching motion of the aircraft. Just what we wanted in the first place.
There is another hidden cost. Because the rotor is now aligned with the shaft the rotor is not applying any side load to the shaft. The pitch is strictly due to the thrust of the rotor and the CG not lining up. The result is that direct control cyclic heads have very little control power, so the roll and pitch rates are not very authoritative. In some respects the direct control head controls more like a hang glider than anything else. You could probably just shift the CG around under a fixed rotor and have the same control power as a direct control head if you could shift the cg an equivalent amount to the rotor tilt.
A very light gyro could potentially be steered by hanging the battery on a gimbal and shoving the battery around. There was a person in europe who built a weight shift autogyro hang glider employing just the method.
Notice that we introduced flapping hinges, this allows coning. Coning requires roll trim that varies with airspeed.
Here is the first great gyrocopter design challenge.
With a direct control head, flapping hinges are required to reduce the servo loads. The softer the flapping hinges and the shorter the flapping offset the less servo load is created. However the softer the flapping hinges and shorter the flapping offset the more coning is allowed and less control power is created. So at a certain flexibility of flapping hinge you run out of control power that is needed to counter the coning induced roll. This is why some gyrocopter designs will not turn to the retreating blade. The control power is already all used up countering the coning induced roll trim!
Now what does delta 3 add to this. I won't go into it now but the result of delta three is that it reduces the overall flapping magnitude. So the flap up in the front of the rotor is reduced, lessening the amount of coning induced roll trim that is needed. However you still don't have very much control power with this design because all the forces against the shaft are in the opposite direction of the way you are trying to steer. So the initial reaction to the control input is to fight the control then the rotor precesses and the CG difference pitch or roll sets in and the control begins to take effect.
This is why the direct control head fell out of favor. Only one kind of direct control head remained, that being the two bladed bensen/wallis type. This head solves some of these problems but creates some nasty other ones, one of which is that it doesn't scale up or down very well from the man carrying size.
The solution to getting more control power without the coning penalty and the high servo loads lies in control mechanisms that fix the blades to a non tilting shaft and adjust the cyclic pitch using other methods....
These other methods involve letting each blade feather by itself on a "feathering hinge" rather than a flapping hinge.
more to come...

[mnowell129]

Two "spider" controlled cyclic pitch mechanisms.
Verbage to go with the pictures later.
mickey

[mnowell129]

Questions that remain that I intend to address...
What are the characteristics of the two bladed teetering head (bensen/wallis) ?
Why does a scale benson head not work right?
Why is the flybar used on your model?
What does collective do and does it help the gyrocopter?
What is following rate and why is it important?
What's the big deal about CG correcting and/or tip weights on
the blades?

If you have questions yourself, please add to the list.
mickey

[mnowell129]

Text that goes with the spider cyclic diagram.
This is the next step in cyclic control beyond tilting the shaft. You still tilt the shaft but you add a hollow hub mounted on bearings around the shaft. You now fix the blades to the hub which is connected rigidly through a big bearing to the fuselage. Now the flapping forces of each blade are carried straight to the fuselage and not carried by the control servos or human. The tilting shaft now tilts in a ball link in the center of the hollow hub. A "spider" turns with the rotor and has linkages attached to blade holders. The blade holders have feathering bearings so the spider can move the pitch of the blades positive and negative. If you look at the left side of the diagram you will see that the shaft tilts and all the blades follow in pitch all around the circle just as if you had tilted the shaft in direct control. Because the linkages are attached at 90 degrees with ball links, only shaft motion perpindicular to a blade causes any change in pitch. Thus if you tilt the shaft and follow a blade around you will see that it receives cyclic pitch just as it would with a direct control head.
This form of control puts the same cyclic pitch inputs in that are present with shaft tilting with two distinct advantages. 1) The flapping forces are not fed into the servos 2) The control power is much higher because the flapping forces are fed directly into the fuselage, so you end up with roll or pitch forces applied directly to the body.
I read someone state on autogyro.com ( I believe Jim Baxter) that with direct control the rotor moves first and then the body. This is in fact true and is indicative of the low control power. The misalignment of the rotor thrust and CG must take place to create motion. With the spider controlled cyclic you get the same rotor thrust tilt but is rigidly attached to the body so the whole unit rolls together, indicative of the much higher control power present.
THe right side of the diagram is an idea of how to build a spider control head without lots of bearings and linkages. The spider is now a thick slotted piece. THe blades now tilt on plain hinges (radially oriented). The little block and CF rod fit into the spider. Now tilting the spider has the same on/off axis effect (or lack of effect) on each blade. This might work if the hinges were good enough to not bind under load and the slot in the spider were smooth enough to also not bind under load.
The complication with this type of control system is the big hollow hub and bearing required. This is a practical, not aerodynamic problem.
The practical solution is to move the spider to the bottom and put IT on the big bearing and let the rotor spin on its normal sized shaft.
What you can probably guess is that this turns into the swashplate and the nominal arrangement for helicopters.
Maybe the next installment will show how a bottom spider works and how this easily turns into a swashplate.
The general result however is this:
1) Non controlled rotors need flapping hinges to correct for forward flight asymmetry.
2) Non controlled rotors need roll trim to correct for coning induced roll.
3) Non controlled rotors can be trimmed in roll for one flight speed.
4) Non controlled rotors can be trimmed with a wing or winglets (the original Cierva's did this)
5) Cyclic pitch MUST be used to control both asymmetric lift and coning induced roll trim.
6) Cyclic pitch can be peformed by shaft tilting, however the control forces are high and the control power is low.
7) Cyclic pitch can be performed with feathering bearings and a cyclic spider. THe control forces are light, the control power is high. The hollow hub is hard to employ.
8) A swashplate provides the same control power and light controls as the cyclic spider with less mechanical difficulty in construction, and results in the same effective cyclic pitch as shaft tilt.

This chain of results is why helicopters have swashplates.
This is why my gyrocopter model uses a cheap commercially available swashplate, etc. (no manufacturing required on my part).

WHat a designer should know is that for a fixed head you are going to have to solve the asymmetric lift problem and the resulting coning induced roll trim problem. This can be tedious and without ailerons, likely only to work at a narrow range of flight speeds.
If you put roll control in with flapping hinges you can expect high servo loads, and low control power but you can still correct the coning induced roll trim problem.
If you do spider cyclic you can get pitch and/or roll control, get by with no flapping and very little coning and need very little roll correction due to coning and will work at all flight speeds.
If you use a swashplate you get all the benefits of the spider cyclic, it is easier to construct and components are commercially available at low cost.

(www.micro-flight.com is guy who makes very tiny helicopters (< 12"), he has very small swashplates, linkages, etc. if you are into the tiny indoor problem, For anything bigger GWS dragonfly, Century hummingbird or bigger helicopter parts are available. www.like90.com has the trex450 parts, including blade holders, swashplates, etc for dirt cheap, these would be appropriate for 1.5 - 2 pound sized models.).

The bottom line is that gyrocopters are controlled by cyclic pitch, whether by flap or by feather, its just which one you chose and what effects you get from your choice.

The next question, "what about that flybar or those tip weights?" is very important. THe answer will explain why your swashplate or spider controlled (or two bladed direct controlled ,etc. ) gyro rolls over on takeoff faster that you can say spit...(and why you can't make a scale bensen! without electronics) And what to do about it.

TTFN
hope somebody is reading this chatter with some benefit...
mickey

[FlyByMike]

Originally Posted by mnowell129

<snipped>
TTFN
hope somebody is reading this chatter with some benefit...
mickey

mickey,
I am. I thought autogyro'ing was going to be simple, boy was I wrong
Keep it up, you're article(s) is very enlightening.
-Mike

[mnowell129]

Originally Posted by FlyByMike

mickey,
I am. I thought autogyro'ing was going to be simple, boy was I wrong
Keep it up, you're article(s) is very enlightening.
-Mike

Thanks, I will.
The advice to the gyrocopter beginner "build a proven design" is
very good advice indeed....

[David A Ramsey]

Still reading. Are ya gonna get to "ccpm"?

[mnowell129]

Originally Posted by David A Ramsey

Still reading. Are ya gonna get to "ccpm"?

I can and will if you like.

[mnowell129]

When your spider is on its back...
Anyhow. When you take the cyclic spider in the last installment and move it to the bottom of the rotor, this is what you get. The blade holder with feathering bearings is the same. The hub is now small and just big enough to bolt the blade holder to. The shaft is a normal non-hollow shaft and goes down into bearings in the fuse. Or the hub can have bearings but this creates some other issues. For simplicity we assume the shaft goes down into bearings below.
We take a shore piece of hollow shaft, the ball joint and a much less strong large diameter bearing and our spider arms and put it together as shown. We attach a little tiller arm off to the side and now we can tilt the hollow shaft cyclic pitch spider any direction. The spider arm now has the same on/off axis behavior creating cyclic pitch in the blade holder as before.
The advantage is that the bearing only has to carry the control load, not the entire rotor head load. So the large diameter bearing required is a very light duty one instead of one or more heavy duty ones for the whole head. The rotor head load is carried by small insided diameter bearings on the shaft, down below, in the fuse, where it can be strong, not cantilievered way up high (there is a trend here).
Anyway it is now just a minor change to get to a real swashplate on the right. Swing the tiller arms out to the side, make one for pitch, one for roll and now you can connect one each to a servo and get pitch and roll. The upper part of the swashplate turns with the shaft (this is the reason to not put bearings in the head, but put them below on the shaft, otherwise you'd have to put a bearing inside the ball join on the upper part of the swashplate).
The upper part of the swashplate has links to the blade holders and this transfers the cyclic to the blades. The blades get the same cyclic pitch with the swashplate tilt as they would have gotten with shaft tilt. We still have the advantages of the spider mechanism, light controls, high control power, etc. And it is easier to build because we don't need hollow shafts. We just need one big light duty bearing with a ball joint in the middle that connects an upper and lower plate with links for the blades holders and servos respectively. The disgustingly easy part about this is that a complete GWS dragonfly swashplate assembly is a whopping five dollars and 37 cents ($5.37). I don't know what your time is worth but 5 bucks for a swashplate to get easy cyclic pitch, which I MUST have to have to achieve trim and control seems like a no brainer, but that's just my opinion.
Further, the entire rotor head and swashplate parts is just $40. I also bought and entire helicopter wreck with all the parts I need for $35.
Ergo, my two gyros have helicopter heads on them with gyrocopter style blades, no coning, good control power and no trim change with speed.
This is how I got to where I got.
If you go look at closeups (rcuniverse, they take bigger image files you can zoom in on) of the G3PO model and the BeGi pusher you'll see exactly what was developed here ( plus that naggy flybar, but that's coming).

While we're at it. Imagine what happens if you made that swashplate
rise or fall instead of tilt. What would happen would be that the pitch of all the blades would go up or down together at the same time, errr...umm... collectively! The process of changing the pitch of all the blades at the same time is called collective pitch. Heli's do it to increase the up down lift control without having to speed the motor up and down (the motor up/down control only on some heli's being called "fixed pitch" for obvious reasons, even though they still have swashplates and cyclic pitch).
Sometimes collective pitch is done by running a rod through the center of the shaft or along side the ball joint and connecting to little levers on the blade holder. When the rod slide up and down the collective pitch motion occurs in all blades at the same time.
If however we just slide the swashplate up and down we accomplish Cyclic and Collective Pitch Mixed (CCPM) into the same little levers. We can do this by using electronics and three servos (ECCPM) ( they all go up and down for collective, opposite each other for pitch and roll) or mechanically (Mechanical CCPM) by mounting the pitch and roll servos on a rocker arm and using a third servo to move the whole rocker arm. Either way when the swashplate rises and falls for collective and tilts for cyclic this is CCPM. There are many ways of doing collective pitch, but if you have a model in your hand and can make the servos move its pretty easy to see what control is doing what. They become the stuff of dreams for mechanical designers, all those littlle linkages.
Enough for one session.
I guess we have to deal with that nagging flybar issue soon....
mickey