Overhead Console for the RAF [Archive]

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Scooter

11-17-2003, 11:58 PM

Here's a picture one of my customers sent me of the overhead console I sold him. *I thought I would share this because I think it really looks good. P.S. Extremly functional too!

Udi

11-18-2003, 04:36 AM

I hope this customer is concerned about the stability of his RAF as much as he is concerned about looks and functionality.  I'm sick of hearing about high time ATP pilots with shiny new RAFs ending up 6 feet under! Udi-

Gary_in_Orygun

11-18-2003, 05:32 AM

Hey Scooter, who are you?  I didn't see a "real" name in your profile or in your signature

airRanger

11-18-2003, 07:43 AM

;D  Check out his E-mail,   that'll give you a clue!    :o ::)

Scooter

11-18-2003, 11:27 AM

I thought I had put it in the profile, guess not. *It is now. * The guy is concerned about safety.  He bought the  Ultimate stab before his RAF kit even arrived.  Plus he he going to train with Menzie.   Safety is certainly the most important, but some people appreciate beauty/craftsmanship also. Larry Martin

Al_Hammer

11-18-2003, 12:02 PM

Larry, have you given any thought to providing differential incidence in your stabs,? That's how Power Torque Over (PTO) was prevented in the early autogiros, according to Ron Herron. Tall tails also act as flow straighteners and will accomplish the same thing, according to C. Beaty. Chuck  has calculated that a typical RAF with 100HP engine could rollover in less than 2 secs from engine torque in zero g. The engine on the stab equipped RAF gyro that crashed in Virginia was 130Hp. A witness said it rolled over , so this could possibly  be a case of PTO(as pointed out by Fergus K. on Norm's conference). Even with the H-stab, there would be no protection against PTO without the differential incidence.

Scooter

11-19-2003, 12:24 AM

I'm not pushing my stabs on this conference, but I will try and answer your question. If I understand it correctly, I believe I have provided differential incidence. Go to my site and study the pictures.  www.gyrostabs.com. You will see that it has a large surface area with tall winglets.   If I remember right, I don't have the figures in front of me, the main area is at 0 degrees, 18 inches long, the center is at 16 degrees, about 9 inches and the winglets are at 66 degrees and 18 inches tall.  A total of over 10 sq ft of surface area.  There is no airfoil on the top of the main surface or insides of the winglets.  Bottom airfoils are used on all three sections.  They provide a lot of negative lift to the bottom and outsides.  This, plus the amount of furface area counter acts the high thrust while holding the tail where it belongs, straight behind you.  Doors on or off it flys straight.   I've had a couple of customers tell me they had to readjust the mast or put extra weight in the nose  because the couldn't keep the nose down, even under full power it would want to climb.  Being that I don't fly gyros anymore I can only repeat what I hear from my customers.  While testing with Ron Menzie I do know that from no power, no hands on, to full power, the nose would not go down one little bit. Anyway,  that's my story and I'm sticking to it.  Larry

Al_Hammer

11-19-2003, 12:57 AM

No, Larry, I was thinking more of angling one side of the stab  differently than the other so as to create a "banking " force, opposite to engine torque. Your stab will not prevent PTO without this. YOu would need to run the engine on the ground and adjust the incidences until the torque was nullified. Scales could be placed under the wheels to measure this. As Chuck B. pointed out, a tall tail also counteracts engine torque because it acts to straighten the propswirl. One more good reason to consider having a RAF modified by AAI.

Udi

11-19-2003, 02:55 AM

Al, I don't think that, without additional supports, the RAF keel can handle the torque moment you are talking about. Udi

Al_Hammer

11-19-2003, 03:50 AM

> I don't think that, without additional supports, the RAF keel >can handle the torque moment you are talking about. Too bad, then, because the stab is not able to be fully effective if it only works in the pitch axis. The tall tail is sounding better and better.

PW_Plack

11-19-2003, 06:17 AM

Al, If I understand your proposed design, differential lift would balance engine torque only in unaccelerated flight; it would actually create a new torque issue during power-off glides. A full-sized tall-tail would solve the problem without creating a new one, right?

Al_Hammer

11-19-2003, 07:27 AM

Paul, it isn't my design. I'm just passing on an idea that has been mentioned before. The differential incidence  stab would work across a range of power/speed settings since its effect would be proportional to prop wash and airspeed. You are right, that a power off glide would create a small problem. In that case, with no propwash, the effects might not be too large and could be compensated for by dialing in a bit of  stick. A Tall tail (or full span horizontal) embedded in the propwash straightens the flow from the prop and therefore reduces the torque. Also, yaw effects are minimized because equal and opposite amounts of spiraling propwash hit the lower and upper surface and cancel out any yaw tendency. And yes, a tall tail is probably  better behaved in power off flight than a differential stab.

Scooter

11-19-2003, 12:33 PM

Sometimes I am puzzled how people can say it won, it can't or it will cause this or that without even have seen one, never the less ever fly one.   It just does what I say it does.  It's been well tested and is on quite a few machines worldwide.  Sometimes we forget that there is more than one way of skinning a cat.  The tall tail is one, but not the only one and maybe, just maybe not the best one. If you will take a good look, you should note that the stab design actually encapsulates and channels the lower half of the prop swirl in sorta of a half wind tunnel.  It gives better thrust control and offsets the engine torque.  Customers have told me that their airspeed was actually increased.   I was just trying to explain why and how it works.  I'm not going to argue with anyone. Before anyone asks, no I don't have test data, numbers and all that.  So, let's just leave it at that.  There's more info at my site or I can be e-mailed. I was going to add a picture, but this thing won't let me.  I clicked on the image icon and the start of some html code was added.  But I don't read html very good.  Oh well, if anyone wants a good rear view of the stab that makes my point, e-mail me.  Larry

Gyropilot007

11-19-2003, 10:51 PM

I'm the guy who put together the overhead console at the beginning of this thread.  You can bet your life (and mine) that I'm extremely concerned about safety.  But I agree with Larry Martin's comment.  You can build an extremely safe machine...and still have it look sharp.  I will admit that I'm still unsure about the horizontal stabilizer issue, even though I have purchased one of Larry's units.  Any experience or comments would be appreciated.

Udi

11-20-2003, 03:52 AM

Bob, I am really glad that you've joined this discussion. *There are very important issues regarding the gyroplane that you are building, and I am relieved to know that you want to learn more about these issues. First, an answer to Larry. * Larry, I believe you and Al are talking about two different torque issues. *You were saying that your stab is doing a good job canceling-out the nose down moment caused by the engine high thrust line. *Al was talking about the rolling moment that is caused by the propeller spiraling the air. *A differential horizontal stabilizer can cancel some, or all, of this rolling torque. *Two examples are the Little Wing and the Dominator. * Correct me if I am wrong, but I think that your stab is designed to apply only pitch and yaw moments. Bob, I don't want to offend you with explanations that are below your current level of understanding. *I don't know how much you already know about gyroplane aerodynamics, or about RAF issues, but I will start from ground level just to make sure you don't miss anything. *I see that you are holding a fixed wing private pilot license, so you will not have hard time understanding what I am talking about. Gyroplanes, like fixed wing airplanes, may have different levels of pitch stability. *There are two kinds of pitch stability - static stability, and dynamic stability. *When the FAA is certifying aircraft, they test these aircraft for stability and unstable aircraft do not get certified. *Unfortunately, experimental aircraft aren't being tested by anyone and the responsibility of verifying stability lies with the kit manufacturer and the builder/pilot. Stock RAF gyroplanes are highly unstable aircraft and that is one of the reasons so many of them have crashed since they were conceived. *Why are they so unstable? A pitch stable aircraft is one that tends to return to its previous trim condition after being upset (push your plane’s stick and let go; it will oscillate a little and then return to trimmed flight). *An unstable aircraft is one that, when being upset from a trimmed condition, does not return to trimmed flight without the intervention of the pilot. *Some of the WW1 fighter planes were made intentionally unstable to make them more maneuverable. *They were difficult and dangerous to fly. In a fixed wing aircraft, the center of gravity must be forward of the wing center of lift for the airplane to be stable. *That is why fixed wing pilots always fill out a weight and balance sheet before flying. *If the center of gravity moves behind the center of lift than the aircraft becomes statically unstable. The same thing happens in gyroplanes. *In gyroplanes stability a little harder to visualize because the gyro does not have a fixed wing, but a movable one. *In the gyro, the rotor is providing thrust that is perpendicular to the rotor disk plane. *We call this force the “rotor thrust vector” (RTV). *The RTV is the gyroplane parallel to the fixed wing center of lift.  You want the RTV to pass behind the CG for the gyro to be stable.   In flight, all the moments acting upon the gyroplane must be balanced in order to keep the gyro from pitching up or down. *Drag, for example, may be trying to pitch the gyro nose down if the center of drag is lower than the center of gravity. *The engine is also trying to pitch the gyro nose down if the engine thrust line is higher than the gyro center of gravity. *There must be a balancing force that keeps the gyro from pitching nose down due to these moments. *This force is the RTV. *The pilot is using the stick to move the cyclic, which controls the angle of the rotor disk in relation to the airframe. *In effect, by pulling the stick back, the pilot is moving the RTV forward in relation to the CG. *This is how the RAF can still fly straight. *The rotor thrust vector is moved forward of the center of gravity to a point where it can balance the engine and drag nose down pitching moments. There are a few problems with this setup in the RAF. *The first and biggest problem is, if you were to enter a situation where the rotor stopped producing lift (zero G). *Flying into a strong downdraft for example. *The RTV can no longer counter the nose down pitching moments, because there is no RTV in a zero G situation. *When this happens in an RAF, the engine nose down pitching moment is so strong that it flips the gyro to an inverted position in a split of a second. *This is a rare situation but it can and has happened many times already. *This is not a recoverable condition. This message is too long, continued below...

Udi

11-20-2003, 03:52 AM

The second problem is that any time the gyroplane is flying with the RTV forward of the gyro CG, it's like a fixed wing flying with the CG behind the center of lift. *The reason this is an unstable condition is because the aircraft reactions to G forces are opposite from what you want them to be. * Example: *The gyroplane is flying straight and level. *It flies into a strong thermal. *The thermal is pushing the rotor up, creating more lift, which means a greater than 1 G situation. *In a situation like this, you want the gyro to pitch down into the updraft, in order to return to a 1 G flight. *Every stable aircraft does that hands off. *In an RAF, since the RTV is forward of the CG, a high G situation is causing a nose up pitching moment (the rotor is pulling the nose up and the weight of the gyro is pulling down). *The nose is pitching up, which causes the rotor to pitch up, and there's even a higher G situation. *This is an unstable condition that feeds upon itself. *It requires a pilot intervention or the machine will get out of control. The above explanation is why the RAF is statically unstable. *What makes this situation even worse, it that the RAF is also dynamically unstable. *I don't want to go into dynamic stability, but I will just say that the reason the RAF is dynamically unstable is because it has no horizontal stabilizer. *Being dynamically unstable makes the RAF very susceptible to porpoising, which I assume you've heard about. *Briefly, it means that, unless the pilot is well tuned to the gyro rate of pitch and control response timing, pilot corrections may cause the gyro to overshoot back and forth until it self destructs. This is where Larry's (or any other) stab is coming into the picture. *Larry's stab has two functions. *The first function is to create a nose-up moment to counter the engine nose down moment. * If the stab were 100% effective, it would completely cancel out the engine nose down moment, and provide just a little more nose up moment. *This would prevent a bunt over when the rotors are unloaded, and it would also move the RTV closer, and preferably, behind, the gyro CG and the gyro will become stable. The second function of the stab is to provide dynamic stability. *Larry's stab, due to the vertical winglets, is also providing some additional yaw stability. Larry may disagree with me on this one, but I don't think any stab, including Larry's, can offset the huge engine thrust offset moment that is inherent to RAF. *There is no doubt that Larry's stab is making the RAF much safer to fly but I don't believe that it accounts for more than a band-aid. *You can search the threads on the other forum for calculation that Doug Riley made for how much down lift is required in order to cancel out the RAF engine pitching moment. *His numbers show that even if you placed the stab inside the prop wash, you would still need a huge stab to generate the required moment. * This is why Jim Mayfield at AAI has decided to really solve this problem by making the RAF a true centerline-thrust machine. *Actually, Maxie Wildes has done that before with his famous "easter egg", but Jim has optimized this design with his engineers. *A large stab may be used to balance the moments in a gyro in which the engine thrust offset is not too great. *In the RAF the offset is so great that the only practical way to make it truly stable is to move the engine down. Bob, this is a long answer for a short question, but, as I said at the top of this thread, I am sick of seeing people getting killed in their RAFs. *I think the RAF manufacturer is criminal, and I hope they go out of business very soon. *I am very worried for all the un-suspecting RAF pilots who are not aware of the death traps they are flying. *Just two weeks ago, as you know, an un-suspecting ATP-rated airline pilot plummeted to his death in his brand new RAF (which had a stab, I don’t know who’s). Udi-

Aussie_Paul

11-20-2003, 06:41 AM

Udi, the Raf keel is 4" X 2" with 1/8" wall thickness. It is very strong compared to what is normally used for keels. Aussie Paul.

Aussie_Paul

11-20-2003, 06:49 AM

Udi, you are so right about the "bandaid fix". Even if the stab was effective enough to compensate for the Raf 10" thrust offset it would be of no use at all in a zero or almost zero airspeed unloading of the rotors with lots of power. Having the Stabs on my Raf was a much needed improvement but having CLTon Hybrid was a much larger improvement and then having stabs as well as CLT made it the most pitch stable machine that I have flown. Aussie Paul.

Scooter

11-24-2003, 12:09 PM

"A pitch stable aircraft is one that tends to return to its previous trim condition after being upset (push your plane's stick and let go; it will oscillate a little and then return to trimmed flight)". * That was a perfect description of what a RAF does with the Ultimate stab. *Except it doesn't "tend to return", it returns. One customer actually complained in a joking way because *every time (before stab) he would fly by his mom's house he would make a few circles to get her attention. *Now he has to manually hold the circle. *When he takes pressure off the stick, his RAF straightens up to it's trimmed position. Here's that picture I was trying to get to work and I messed around with the profile thing and got it to work. *Just requires keyboard time. * P.S. removed the N-Number because I haven't gotten an answer from the owner yet. *Some people don't check e-mail very often. *Larry

Hognose

11-24-2003, 04:27 PM

Having the Stabs on my Raf was a much needed improvement but having CLTon Hybrid was a much larger improvement Paul, and guys -- That is exactly what the studies at University of Glasgow concluded -- the single best thing you can do for pitch stability is to get the thrustline to run through the centre of mass. The next best thing is to have sufficient horizontal stab (area, arm, and interaction with the rotor wash are all factors) to provide real-world pitch damping. And having the two together can prevent or delay pitch excursions (depending on the cause of said excursions). Glasgow had an instrumented gyro where they could move the motor up and down on the mast between flights. Lots of very good experiments went on there. It all started with a CAA grant to study why a certain brand of gyro ras reverting to kit form inflight due to PPO. (Not what you think -- Fetters-era Air Command). If you remember, Air Command hit hard with (1) complete kits, (2) effective marketing(=many sales), (3) the Rotax motor (=more thrust than Macs or VWs), and (4) longer props (=higher thrustlines). Unintended consequences. Air Command wound up banned in Britain (although I think the CLT machines are permitted again. Current Air Commands are a good and safe design). Anyway, that other vendor of high thrustline machinery (the one that says a stab is a hazard), their rep told me that there had been no academic research on Gyro stability and control since NACA. Do they really believe that? They must. They couldn't sell their machines unless they believed them to be safe. cheers -=K=-

airRanger

11-25-2003, 11:37 AM

But, Scooter/Larry ...........says  Here's that picture I was trying to get to work and I messed around with the profile thing and got it to work.  Just requires keyboard time.   P.S. removed the N-Number because I haven't gotten an answer from the owner yet.  Some people don't check e-mail very often.  Larry ********  I DID answer you, both in this Instant messaging here and to your Private e-mail. Just send Royalties check to the photographer.......Me! Dennis ::)

Scooter

11-25-2003, 11:53 PM

I don't have or use instant messaging and nothing has ever appeared in my pm from a Dennis unless it was spam. *And, Dennis who?  Never sold a stab to a Dennis that I remember.  Sorry no check. Anyone sending me e-mail, whatever the method, best be very specific in the subject area or they go to the automatic delete folder in la-la land.

Chuck_Ellsworth

11-26-2003, 01:00 PM

Quote: ----------------------------------------------------------------------- You can build an extremely safe machine.... and still have it look sharp. ----------------------------------------------------------------------- How true.... Thats why im going to build a two place Little Wing with a Radial engine. I just may finally decide to start offering gyro training....maybe the time has come for me to do it. However something new just just came up that may delay me for another year before I am ready to actually start a school. At least I have ordered the plans so I am now committed to the project. Chuck E.