This is the articles
Horizontal Stabilizer Discussion from RotorCraft Conference
Back To RAF2000 Owners Home
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Summary: Following is just a snippet of the many-many horizontal stabilizer discussions that appeared on the old RotorCraft Conference. The newer
http://www.rotaryforum.com forum holds many similar opinions.
Issue: The consensus is that the RAF 2000 should have a horizontal stabilizer.
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Links to Horizontal Stabilizer manufacturers:
Anyone have current information to put here?
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Date: July 03, 2002 09:10 AM
Author: Larry Martin (
earthloc@worldnet.att.net)
Subject: RAF Stabs
It has come to my attention that RAF is working real hard to convince the FAA that the RAF machine doesn't need a stab and that in fact a stab is a safety impairment to their machine.
Here is the exact quote from the RAF manual, product notice no. 30 dated June 2000.
"Horizontal Stabilizer: The RAF 2000 Gyroplane was tested by the factory with a Horizontal Stabilizer. It was found to have some adverse flight characteristics evident during the testing and there was a consequential crash of the test aircraft in 1996" and they go on to say do it at your own risk and so on.
...TEXT DELETED...
Bad Stab Page
"Don't squat with your spurs on!"
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Date: January 21, 2001 12:24 PM
Author: J P McNear (
rotorforce1@aol.com)
Subject: Horizontal Stablizer
I've installed a horizontal stabilizer on my RAF-2000 and am amazed at the difference it's made. The pilot workload is dramatically reduced and even though my stab has no dihedral, the landing flare is fine. It does NOT try to fly into the ground. I can trim it out and it flies with very little control input in all kinds of Florida weather.
I assembled the kit in 1996. It went together easily and quickly and the quality of the parts was first rate. In my dealings with RAF, Peter, Don, Linda, Maryanne and everyone else was always professional, courteous, helpful and responded promptly to my requests. I also thought Dan was a very good pilot.
I flew the gyro for 450 hours and thought it was a fine cross country machine. I grew up around machinery and like a lot of people in Southwest Florida, built and drove race cars, air boats, gigged frogs, hunted coons and raised hunting dogs. I think because of this (machinery, not coons, dogs or frogs), I haven't experienced the mechanical problems some people have complained about. The rod end bearings supporting my alternator haven't broken because I set them up so there is no sideways or bending load. I haven't had redrive belts chew themselves up. And they don't if properly aligned and tensioned.
Early on, I had the lower drive sprocket bored and sleeved at a local machine shop for a reasonable cost, not the exorbitant price I've seen quoted on the Conference. I also installed a double bearing rotorhead from Ernie at RFD.
I've installed most of the factory upgrades. The new factory ignition, on completely different circuits as are the fuel pumps, hasn't missed a beat after 300 hours. The new prerotator clutch works very well. I got the new untwisted, tip weighted blades at 475 hours and feel they fly better. I intend next to install fuel injection and the new seat tanks.
So, after 450 hours, I reluctantly bought a horizontal stab, thinking it wouldn't make all that much difference. Was I ever wrong!
I purchased the stab from Don Parham of RFI for $375 plus freight. It has 18" tip plates and no dihedral. I mounted it behind and below the vertical tail by sawing a strip out of a length of 2 x 2 aluminum tube to reduce the dimensions to 1.75 x 2, welding it back together so it would telescope inside the keel tube. The stab mounts on this tube. This method of installation gives a longer moment arm and makes it easier on the legs when wrestling it around on the ground. The tail wheel has to be offset slightly to the side.
This stab has made what I thought was a good cross country machine into a great cross country machine. The tip plates cure 95% the yaw problems when the doors are installed. I have over 500 hours and just love the way it now flies. There is no way I'd go back to flying without a stab.
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Date: July 06, 2002 02:24 AM
Author: Paul Bruty (
paulbruty@lexicon.net)
Subject: The problem with........
......a lot of people being trained in unstable aircraft, is that they think that all gyros behave that way.
I was one of these people. Following is a story that I wrote in June of 2000.
Well, after 12 months of testing with my RAF 2000, a variety of different size, shapes and dihedral angles of horizontal stabilisers, I now put pen to paper. I have tested with all sorts of loads and in ALL sorts of conditions on a number of machines and rotor systems. I have found that a relatively small flat plate placed behind the engine on a gyroplane is not necessarily an "effective" horizontal stabiliser. The higher that the thrust line is above the vertical C of G the more important the stab is. A lot of machines now have high thrust lines due to the reduction units and large diameter propellers that we now use. It all started in 1982 when I bought a partly built Bensen style airframe that already had a stab under the fin and rudder as well as the rock guard. My dad and I fitted a direct drive 1905cc VW with a 53" prop and 23' Rotor Hawk blades (resulting in a low thrust line) and got flying. (We had flown Gyrogliders in 1962 and my dad had done about 70 hrs with a Mac with the usual attacks). I did 350 hours in this machine and did not know what Porpoising or Power Push Over(PIO and PPO) felt like. In 1989 I started training in a side-by-side Air Command with the longer mast, raised Rotax 532 driving a 68" 3 bladed prop and 25' blades.
My first student was a friend who was flying fixed wingers and due to the cost he thought he would try gyro flying with me. We started by flying the length of the runway and then taxi back and do it again. At that point I was not comfortable flying dual around the circuit with a single ignition 2 stroke and marginal rotors. My friend kept over controlling and porpoising. We packed up at last light and went home. I got to thinking about a pic I had seen of an Air Command with a cabin and their h/stab, so that night I made a temporary one, from memory out of ¼" ply and steel straps. The next evening we go out again and my friend is doing so much better. During a break for fuel I took the stab off, and low and behold he is almost back to the way he was the evening before. The next evening we went out again with the stab and he was progressing well. He soloed some months later. I never trained without a stab again. I believed that problems the students would have learning were just due to the inherently unstable flying machine, that we called a gyroplane!!!
I have had many an argument with experienced gyro pilots that declare that they do not need one. I say to them, experienced gyro pilots don't, they have the necessary skill to control the gyro so as to avoid danger. A stab is most useful for students, and to the low time pilot caught in rough weather. "Effective" h/stabs become more important as the thrust line gets higher. This has become more prevalent with the arrival of the reduction drives and associated larger diameter propellers. These designs place the thrust line above the vertical C of G, which results in the propeller rolling the machine forward when a gust unloads some of the rotor drag. One option is to raise the cabin or seating area, which makes the gyro difficult to get in and out of, particularly as we become older.
The other option is to fit an effective horizontal stabiliser. This is the path that I have taken. Some people are quoting wing commander Wallis, and others, who says that h/stabs are not necessary. They weren't in the days when all the machines had direct drive with short props, thus keeping the vertical C of G in the correct place. In 1990, when I was National president of our Australian Sport Rotorcraft Assn. (ASRA controls gyro flying on behalf of our government), we made effective h/stabs mandatory and implemented a ratio between rotor head and stick movement to keep the sensitivity down. I did over 1600 hours training in my Air Command during the next 8 years. A couple of years ago my chest (I was then 49 y/o) decided that it had had enough of the cold air and I looked for a machine that would allow me to go places and train in comfort. Having a look around the world, the only machine that really met my criteria and had sufficient machines operating safely was the RAF 2000. The only thing I was disappointed in was the fact that it did not have an h/stab as I had proven the h/stab to be essential, particularly for students and low time pilots. It was explained to me that it did actually have one by way of an arrangement with a rubber mast bushing and control linkage set up. I was told that this did the same job. I believed what I was told and became a rep for the RAF factory.
This about the time that I found Norms wonderful forum and went toe to toe with the anti RAFers. I am sure that a lot of you will remember that time.
When I got flying the RAF I was very happy with it, but found that the mast set up did a good job of lowering the nose when it rose but would not lift the nose when it went down due to rough air. This meant that the student only had ½ the workload to start with until they became more proficient. My Air Command (or any high thrust line gyro) even with the stab (which I now know was too small) required quite a high student workload during the early hours. We went to 1999 Bensen days and met some great people from the factory as well as locally. I flew in 3 different RAF's and found that they all behaved the same as mine. It was comforting to know that our machine flew normally compared to other RAF's.
A month later my wife and I were in New Zealand on holiday and I had heard that Rob Sanders, who I had trained in my Air Command a few years earlier was a RAF rep, and that he had experimented with h/stabs on the RAF. We went down to see Rob and other pilots I had trained to catch up with them and to check out the stab situation. Rob told me how they had developed the stab over a period of time because of the extremely rough air over there between the mountains, and flying could be very uncomfortable and almost dangerous. The conditions were moderately rough and Rob said that it was not rough enough to do the stab justice. Being a very untrusting soul I said that I would love to try it out. Off we went and Rob trimmed the machine to 60 mph and handed over to me. I naturally went easy with it but I was doing a lot more than I needed to. I eventually did what Rob said and let it have its head and I could not believe what was happening, a gyro flying itself in quite rough air. (Rob did not think it very rough) When we got to a 1000' Rob took over and did a zero airspeed and engine idling vertical descent down to 500' without any dramas at all. I then took control and began climbing towards a 900'mountain to see if we could get some rougher air on the lee side. As we were getting closer and could almost see the whites of the eyes of the tourists I thought that Rob was going close to the mountain when I realised that I was supposed to be doing the flying and turned away. I had been sitting there like I was instructing, just resting my hand on the stick ready to take over if needed. Rob of course was doing the same only he was thinking I was flying. The machine had climbed 400' through rough lee side air on its own. I was amazed. I then eased the stick forward until we hit 85 MPH. Still no negative effects. Rob gave the radio call and I lined up on finals and did an engine idling full flare landing. Rob said "do a touch and go" so I applied full power and established climb attitude. Much to my horror Rob reaches over and grabs both my wrists and lifts them off the stick and throttle. I very nearly said something I shouldn't. It was only the knowledge that Rob had a lot of experience with the stab that I relaxed. I kept center line by using just a little rudder and we climbed full power to 500'.Rob took over and threw it around a bit and then I lent over and patted him on the shoulder and said "WOW!!!! What you have done to improve an already great machine is fantastic."
Since that time I have done well over 300 hrs testing a number of stabs of various sizes, shapes and placements. Prototype no 5 that we are now flying is the best. I have had students that I have been training as they are building and have had them fly with and without the stab and without exception they have insisted that they have one on their machine. The first one we built was the same as Robs but made out of 1/4" plywood with 2 supports down to the keel on both sides. We flew it and were a little disappointed but we could feel it trying to work but it was flexing too much. I was able to fly that one solo on a nice evening at 50 mph about 7 miles back to my airport join base reduce power, pull on the carby heat and readjust power, turn onto finals and get down to 4 feet without touching the stick. I had only used power and rudder. The next one I changed the shape a little and moved the outer/rear edge forward to stop me hitting my shins when I was pushing the machine into the hanger. This was made out of much less flexible wood but was slightly worse in stability. The next one was the same as Rob's (all the stabs have had between 10 and 12 degrees of dihedral each side) but was shifted back 11 inches. This had been the best one that I had flown. This machine is in central Australia. I went up there to do the final inspection and to finish off my customers training. One day we were doing circuits in a gusty thermally 12 mph wind and I said to Glen let me give you a rest I want to test something. We took off and by 50 feet I had it trimmed in a 60-mph.full-power climb and took my hand off the stick. We climbed to 500' reduced power, skidded around the turns, reduced power to 3500rpm and approached the strip. When we got to 20' I thought that with the higher thrust line if I quickly reduced power the nose might come up but it didn't and I had to take the stick to flare. Well we now have a composite stab without struts and have seen a much more stable RAF. This "effective" h/stab has a neutral airfoil and is possibly 30 to 50 % better than the flat plate variety. Two weeks ago I took the stab off and had it painted. Before I put it back on, one of my students, who has spent his working life as an aeronautical engineer, rang for a lesson. I thought "what a great chance for a test". Mike agreed to fly without the stab and away we went. Poor Mike, he was becoming quite proficient the week before, and now he was working extremely hard, particularly with the power. He was not used to having to adjust power all the time as the nose went up and down in the bumpy air. I was not game to take my hand more than 1/2 an inch away from the throttle in case Mike got behind with power and we would be at the beginning of a power push over. Mike said, "why would people want to fly with that workload?" I told him that with enough training you do get to be able to fly a high thrust line machine ok, but it is quite a while before they can fly in rough weather, and is never as comfortable as with the stab. From a personal point of view the comfort on a 1,2 or 3 hr flight is fantastic. I came home a couple of days ago from a flyin straight into a 30 mph headwind and was able to maintain airspeed of 60 to 65 mph. I have done this trip a number of times and one of those times I had the same conditions, strong gusty headwind without the stab and could only maintain an airspeed of 40 to 50 mph and my throttle hand was worn out by the time I got home.
During the 2 years prior to the "effective" horizontal stabiliser, I had taken a lot of people for a trial flight in my RAF. Quite a number were very disappointed that they did not have much control of the RAF in pitch. I think that a few egos were dented. This was a little discouraging for me because I could fly it quite easily. That was obviously due to my thousands of hours in gyroplanes. What I needed was a RAF that was much easier to fly, so that people could enjoy their trial flight without it being a trial? That way they may be encouraged to come back and have a serious look at learning to fly gyroplanes. I have now achieved what I set out to do. I now have a genuine cross country gyroplane that can be flown for over 3 hours at 70 mph IAS in all sorts of weather, and do it comfortably and most enjoyably.
Well now I am in the process of producing a much-improved RAF style (side by side fully enclosed) gyroplane.
It is a little humbling to think back to how much I did not know, and how people on this forum have nurtured me along. Aussie Paul.