The following horizontal stabilizer article was extracted in total from the AFS Newsletter of August, 2000. It is published here to add commentary to the discussion about which we all hear so much. No editing has been done to the actual writers’ words, sentences, or paragraphs.
Opening paragraphs written by the AFS Newsletter editor have also been included since they echo our sentiments and contain factual and documentary information which all members concerned with this issue need to possess.
The editor of the AFS Newsletter is Lisa de Vries, a CFI under the PRA Exemption 5029, she has 4400 hrs total time, of which 300 is in gyroplanes.
The Gyrocopter Horizontal Stabilizer Issue
In this issue of the AFS Newsletter we publish the experiences of Gyro instructors flying RAF’s with and without the Horizontal Stabilizers. In no way do we aim to resolve the issue for once and for all. We are simply giving space to all saying YAE and all saying NAY. We do have a few thoughts that you may consider when reading this issue.
In 1989 Transport Canada as well as the FAA evaluated the RAF 2000 as a Kit suitable for Amateur Built Category Aircraft. The kit comes without horizontal stabilizer.
When Cessna delivers an airplane, it is built to FAA standards. Other companies have made modifications like micro vortex generators (improve lift and lower stall speed), or bigger engines (Raleigh conversions).
These modifications are called After Market Conversions and they require extensive testing before being approved by the FAA. Cessna neither condones nor disapproves of those. The customer has the final choice as to what he wants out of the aircraft.
If adding a Horizontal Stabilizer changes the operational characteristics of the gyro, you have made a “major change” as defined in FAR 21.93(a). In the US your Operating Limitations may require you to notify your FAA office and re-establish compliance with FAR 91.319(b).
This issue is about people’s experiences. Scientific evidence can only (be) obtained when testing is done in controlled environments like wind tunnels.
Parameters like temperature, wind, turbulence, size and shape of horizontal stabilizer can be varied on the same machine to measure stability and control-ability. This takes time and money.
Last but not least, where it comes to the horizontal stabilizers, I am probably the most ignorant of y’all. I have not flown with one yet. Which is why my story is missing and no editing has been done to the material presented
NOTE: Duane Hunn and Jim Logan flew with Gary Brewer’s horizontal stabilizer. It is now with Dofin Fritts in FL. Dofin will ship it to me later. “How to make a great gyro better”.
Date: July 06, 2002 02:24 AM
Author: Paul Bruty (firstname.lastname@example.org)
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.
Paul Brutys horizontal stabilizer story
Well, after 12 months of testing with my RAF 2000, a variety of different size, shapes and dihedral angles of horizontal stabilizers, I now have 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. What I have found was that a relatively small flat plate placed behind the engine on a gyroplane is not necessarily an “effective” horizontal stabilizer.
The higher 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 night we went out again and my friend did so much better. During a break for fuel I took the horizontal stabilizer off and low and behold he is almost back to the way he was the night before. The next night we went out again with the horizontal stabilizer and he was progressing well.
He soloed some months later. I never trained without a stab again. I have had many an argument with experienced gyro pilots who 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 horizontal stabilizer is most useful for students and to the low time pilot caught in rough weather.
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 horizontal stabilizers 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 now 50 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 a horizontal stabilizer 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 link age 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. At this point I had not flown in a RAF. 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 1/2 the workload to start with until they became more proficient. My Air Command (or any high thrust line gyro) even with the horizontal stabilizer (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 horizontal stabilizer 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 horizontal stabilizer justice.
Being a very distrusting 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.
Eventually I 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 zero power 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 realized 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 thought 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 reached over and grabbed both my wrists and lifted 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 leaned 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 200 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 horizontal stabilizer and without exception they have insisted that they have one on their machine.
The first one we built was the same as Rob’s 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 carb 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 customer’s 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 3500 rpm 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” horizontal stabilizer 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 flying straight into a 30 kt headwind and was able to maintain airspeed of 60 to 65 kts.
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 kts and my throttle hand was worn out by the time I got home.
During the 2 years prior to the “effective” horizontal stabilizer, 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 kts IAS in all sorts of weather, and do it comfortably and most enjoyably.
SO, TO ANYONE THAT HAS FLOWN IN A RAF WITHOUT MY H/STAB PLEASE COME A ND HAVE ANOTHER GO. You won’t be disappointed with this now remarkable gyroplane.
Regards from a fellow flyer, Paul. Paul Bruty has flown 3000 hrs in Gyro’s since 1982, of which 1200 hours are in various RAFs. His current H stab has a 9 foot square area. Paul has flown 150 hours with his current horizontal stabilizer —cd.
“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.
Thinking Horizontally by Michael J. Stump, CFI Gyroplane
In this article, we’re going to have yet another conversation on gyroplane horizontal stabilizers; a subject that still seems to be a popular one in gyroplane circles.
Now, I don’t like to help “over grind the axe,” but as time goes on, more people develop strong opinions on the subject because it is one of importance. Here, you’ll see my own.
You may have been involved in conversations that include statements such as “airplanes have horizontals; why not gyroplanes?” Or, maybe you have heard horizontal comparisons with actual, living birds.
I, too, have been sucked into such discussions, and here is my opinion, which also consists of a few facts: Horizontal stabilizers do wonderful things for gyroplanes!
Gyroplanes with properly designed and built stabilizers are easier to fly, are more stable, are more comfortable, look better and really should no longer need to be discussed, in the controversial manner, that is. A strong opinion, yes, but valid. I have enough experience to know that horizontals really do work, and work very well!
There is a certain school of thought, which states that the gyroplane one trains in should be less stable than the one they will solo for the first time. This way, there are apparently no surprises, the machine for solo should be “easier to fly,” and the first (and successive) solo flights can be completed more safely.
In addition, many new pilots have built machines that have no horizontal stabilizer; therefore the training machine should ideally be at least as unstable. An analogy to this may be that just because you were trained to drive a car, you aren’t necessarily competent enough to handle a street bike. While I tend to agree with this angle, there is a more fundamental issue that needs to be resolved.
For those of us who like the idea of a nice, functional horizontal stabilizer on our gyroplanes, a question arises when we look at what some of our students are building Aircraft without horizontal stabilizers, or stabilizers that don’t do much more than sit there and look good! Why? Because apparently many manufacturers still have not adopted the concept and proved it for themselves.
Also, some machines lack a horizontal stabilizer so that the aircraft can be sailed an “ultralight,” which really is another altogether different, controversial issue in itself. Other gyroplanes compensate for pitch instability through other mechanical means, and this is a good thing, but horizontal stabilizers have been proven to work on these aircraft, too.
Back to the airplane and the bird for a minute. It is true that if you removed the horizontal stabilizer from your hangar partner’s airplane while his back was turned, he’d have a heck of a hard time trying to fly the aircraft in pitch, and probably couldn’t.
I do agree that removing the stabilizer from an airplane essentially removes the pitch control altogether, and that a gyroplane without a stabilizer still has pitch control, but the horizontal stabilizer still keeps the machine flying straight like the proverbial arrow.
Now. look at the birds outside. What do you see. other than a “machine” that carries a nice, big, functional horizontal stabilizer?
When you watch birds fly, you’ll see that they don’t have a rudder; they yaw by twisting the big stabilizer. Stabilizers absolutely, positively work, as we can see and nature has proven. The old “arrow” analogy is also still a good one.
Now, I have never run the old Cierva horizontal stabilizer sizing equations on your run of the mill California Condor, but the results would be interesting to see, I’m sure. The problem is that I can’t seem to locate a California Condor that can sit still long enough for me to find the CG… yet another issue.
In all seriousness, though, gyroplanes are admittedly dynamically different from Cessnas and sparrows, but each of these machines still relies on simple aerodynamic principles in order to stay aloft with some reasonable level of stability, and these principles absolutely do apply to gyroplanes… and Cessnas…and sparrows.
The facts that I have discovered through real world testing also have plenty of validity. I have flown single place, side by side and tandem gyroplanes without a horizontal stabilizer, and found them to be relatively challenging to fly in pitch, and often downright uncomfortable if the air is not calm and thermal free.
I own a single seat, very popular kit built machine, and it does have the “standard” factory stabilizer installed. The effect? It is noticeably easier and more pleasurable to fly than without one, but the machine is still a handful in moderately rough conditions. A bucking bronco, actually!
If you run the Cierva numbers on my particular stabilizer, it is “too small”, yet it does have some positive effects, and I am glad that it is there. Another issue with this stabilizer is that it is fabricated from flat plate section, which means that the upper and lower surfaces have no camber at all.
This stabilizer works by deflection of air alone, and is far less effective than if it were actually capable of producing true lift. The latter requires camber (curvature) of the surfaces.
I have had several opportunities to fly aircraft owned by different individuals who each have installed very large, cambered stabilizers, even on machines that were designed to fly without one.
Generally, the stabilizers I flew on these machines are mechanically symmetrical, meaning that the camber on the bottom is the same as it is on the top, and they generate large, symmetrical, opposed lift vectors.
Also, these stabilizers were sized properly, if you listen to Cierva. The result? They fly great, are very stable in pitch, and are much more pleasurable to fly.
As far as control-ability and maneuverability are concerned, the aircraft never seem to exhibit a lack of either, due to the horizontal stabilizer installation. In other words, folks, flaring for landing was still as easy as it should be!
I have yet to experience a negative effect from a horizontal stabilizer on flight characteristics, and in most cases the stabilizer was properly “Cierva sized.”
Additional testing I did a few years back showed a few other interesting things to be true. First, winglets, as seen on many larger aircraft wing tips, had the effect of increasing the effectiveness of the stabilizer, or “it acts bigger than it really is.”
A valuable side benefit from this that often goes overlooked is that winglets can improve yaw stability by providing additional vertical surface area.
With this in mind, it seems that the best stabilizers would have symmetrically cambered surfaces and installed winglets, with the expected result being improved stability in both pitch and yaw.
The gyroplanes that I flew with this combination of cambered, Cierva sized surfaces and winglets had the most stability of any other machines I have flown, and this appeared to be the right combination since these machines were the most comfortable and easiest to fly.
Because I keep mentioning “Cierva,” I probably owe a quick explanation for those who don’t recall the story. In the 1920’s, a gyroplane pioneer named Cierva developed tractor gyroplanes that had large horizontal stabilizers installed.
He discovered a formula for sizing the horizontal stabilizer that was based upon a measure he called “rotor volume.” Cierva suggested that the “tail volume” should be roughly 12 to 15% of the “rotor volume.”
As for some definitions to make this useful, “tail volume” is defined as the horizontal stabilizer area multiplied by the horizontal distance between the center of the rotor head and the quarter chord line of the horizontal stabilizer.
“Rotor volume” is defined as the total rotor blade area multiplied by the rotor diameter. The final solution, then, is to divide the tail volume by the rotor volume and look at the result as a percentage.
Horizontal stabilizer location is another key issue. Some say to keep it in the propwash, others say keep it out and in the clean air.
How I see it: Air planes are designed both ways; gyroplanes can be, too. My single place machine has the stabilizer below the propwash, and it works noticeably well. An acquaintance with an identical machine allowed me to test fly his aircraft with the stab moved up into the propwash.
What’s the effect of moving the horizontal stabilizer? Not noticeable. On my current two-seat trainer, I have a compromise. The stabilizer is in the propwash, but not vertically centered on the prop.
The effect? Stabilized as expected, with no strange habits. You may, by now, even wonder how it is even possible for a gyroplane to fly without a horizontal stabilizer.
The reason is simple: most gyro planes have very little surface area exposed to the airstream and fly relatively slowly, therefore, there is very little drag to offset with a horizontal stabilizer. This is not to say that stabilizers aren’t effective, because they are!
In the case of enclosed gyroplanes, tail group sizing is even more important, because the center of pressure must always remain behind the center of gravity, else the machine will want to “swap ends” and fly tail first….a dangerous condition that I experienced… once!
The solution for safety and stability is to provide generous tail surfaces, both horizontal and vertical, that ensure that the center of pressure stays where it should. Let’s ask the final, most important question: Do gyroplanes need stabilizers? No, they don’t.
There are many very interesting mechanical methods in some gyroplanes that a few manufacturers have put into place to help with stability; many others just fly without aids to stability.
The truth is that training is more important than the stabilizer, because with proper training, most people can fly a machine without one, however, my experiences show that horizontal stabilizer equipped machines are just easier and more pleasurable to fly, so let’s find good reasons why not to have one!
That includes machines that use other interesting design methods through-out the rest of the aircraft to aid in stability.
To conclude, I have proven that stabilizers generally work quite well, and that the advantages of stabilizer ownership far exceed any disadvantages. Some of you may want to see data, which is difficult to collect without elaborate instrumentation, but I don’t need to prove anything to anyone except for myself.
I am convinced by plenty of testing and seat of the pants, real world stick time. If you have never tested stabilizers, prove it to yourself. You may find that once you install one, you’ll kick yourself for not having done it a long time sooner!
As for the students, I believe that gyroplane Flight Instructors are obligated to provide their students with valid information so that the student can make the horizontal stabilizer decision for themselves.
As for manufacturers who have not done enough testing, please do more! The gyroplane manufacturers can have the biggest impact on the stability, safety and horizontal stabilizer issues; hopefully all gyroplanes will some day be equipped with one straight from the crate.
If all gyroplanes came with proper horizontal stabilizers, the stability in training issue could be effectively dissolved. Until then, I’ll most likely train intentionally in an aircraft of only moderate stability because many students will have un-stabilized aircraft.
You can see the demand for stabilized machines…properly designed stabilizers work well and are here to stay. As time goes on, I’m confident we’ll see more. If your creation has a stabilizer already, please review your design and see if it can be improved.
Chances are, it can, and doing so should be a good thing. In the meantime, and in the future, proper training will still be necessary, regardless of the type of gyroplane you choose to fly. Thanks for reading, and fly safe!
Michael J. Stump Michael Stump is a CFI Gyro.
He has flown gyroplanes for 8 years and spend three years developing and testing various h stabs. He holds an Airframe and Powerplant Mechanics license. He does not own an RAF—ed.
RAF Factory Statements
“The RAF 2000 Gyroplane was tested by the factory with a Horizontal Stabilizer. It was found to have some adverse flight characteristics evident during testing and there was a consequential crash of the test aircraft in 1996.”
“Any use of a Horizontal Stabilizer is done against the recommendations and advise of the RAF Factory. The installation of a Horizontal Stabilizer does not replace the requirement for proper and adequate flight training. Installation of the Horizontal Stabilizer is at your OWN RISK.”
“Review HISTORY OF THE RAF 2000 GYROPLANE’S UNIQUE DESIGN INNOVATIONS.” “Does the RAF have a horizontal Stabilizer? Yes!! It is incorporated into our two-part mast system, rotor head and push tube design (Patented in the U.S.A. and Canada)” (end quotes—Ed.)
GARY BREWER ON THE HORIZONTAL STABILIZER
I would like to give you a little background on why I started experimenting with a Horizontal Stabilizer (i.e. HS). Back in the Fall of 1997 Bob Aspegren and myself decided to fly our gyros to El Mirage Dry Lake Bed for the annual fly in.
Bob had a Barnett J4B, which has a HS. While en route to and from it was easy to tell the benefits of an effective HS. Bob was cruising along straight and level reading and folding his sectional as we went.
On the other hand, I was experiencing much more of a work-load keeping my gyro straight and level. It was much more difficult for me to read my sectional while we cruised along.
I could fly along very nicely making small control inputs without even thinking about it but when I wanted to let go of the stick for a few seconds to position the map etc. I would have to take hold of the stick to make a correction. So when we got back Bob offered to help me design and make a small horizontal stabilizer.
The first attempt was a small stab that had no airfoil shape and a surface area of 6.5 sq. ft., which made little or no difference. We then decided to put an asymmetrical air-foil on it to improve performance but it still wasn’t what we wanted.
The third try was a welded steel frame with ribs and spar mounted under the keel. This one had 13 sq. ft. of surface area and an asymmetrical airfoil shape. Now we were starting to see an improvement in pitch stability.
This is the stab that I have offered to anyone who would like to see first hand the effects of a stab. The horizontal stabilizer I am now testing is 7′ wide, 30″ at the keel and 24″ at the tips.
This gives me 15 3/4 sq. ft of surface area I have tested this horizontal stabilizer for over 200 hrs. Performing all PTS maneuvers with no negative effects. In all my testing, I have not at any time felt that I had too much stability. I have always been able to flare on landing while in ground effect, with or without power.
Engine out simulation is 60 MPH indicated engine at idle and the VSI shows a 1000′ per min. descent. This descent rate is the same without the HS. Tight turns are not a problem. I can turn as tight as I am comfortable with (50 60 degree).
I have made all the adjustments to my machine that Dofin did to his but still have not been able to get the pitch stability performance he has, but by bolting on a horizontal stabilizer I could achieve the stability that I feel comfortable with.
Here are some of the facts from my 2 years of testing: I have 1100 hrs of flight time. This in no way makes me an expert but I felt you should know. Without the stab I can trim the gyro for straight and level flight at 55-60 MPH.
With calm wind it will fly quite nicely without any corrections with the stick and flying with just rudder. If I bump the air speed up to 70 MPH with light winds to 10 MPH the aircraft will start to hunt slightly left or right requiring more rudder control.
The main difference I noticed now was that any small bump or gust of wind will raise or lower the nose slightly and start a pitching motion continuing to increase until I have to stop it with the stick, usually 3-4 cycles. Without the HS when I hit a gust or thermal I can feel the nose pitch up requiring a stick correction.
With the horizontal stabilizer under the same conditions the whole machine raises with very little pitch change. As I stated before I have performed all PTS maneuvers with the stab and I found that it makes the aircraft more stable in pitch and easier to fly. The best ex ample of this is the following. This test was performed solo.
Engine RPM 4400, air speed trimmed to 60 MPH, winds light (less than 5 MPH) and temp. 90 degrees. With airspeed at 60 MPH I slowly pulled the stick back to bleed off airspeed to 55 MPH and then let go of the stick.
The nose dropped, airspeed increased to 60 MPH and leveled off without touching the stick. This was repeated in 5 MPH increments until I reached 40 MPH.
Even with a 20 MPH difference in airspeed the nose raised on its own and leveled out at 60 MPH every time in one cycle. Next I raised the airspeed to 70 MPH and did the same test in 5 MPH increments.
This time I slowed to 50 MPH, which is 20 MPH difference. Again the results were the same. The only difference was with the last run after letting go of the stick the airspeed went to 75 MPH briefly then to 70. I think this test show’s positive dynamic stability. In my opinion, I don’t feel the RAF has to have a horizontal stabilizer.
I also don’t think the HS is a magic fix all. A horizontal stabilizer doesn’t eliminate the need for training. A horizontal stabilizer should not be flown in marginal weather conditions that the pilot is not comfortable in and it should not be used as a crutch to make up for experience.
In over 2 years of testing I haven’t found any reason not to take advantage of the Horizontal Stabilizer. I prefer to fly with the horizontal stabilizer and feel more comfortable when going fast or flying in strong winds. My recommendation is simply this: do the research; get the facts.
Fly a gyro without an effective horizontal stabilizer and then fly it with one. Make up your own mind. As for my students, both previous and current, I try to explain the aerodynamics of the gyro along with the effects different thrust lines and horizontal stabilizer have on flight characteristics.
If the student wants to fly his ship with an horizontal stabilizer then he trains with one. On the other hand, if he chooses not to use an horizontal stabilizer on his ship, then we train without it. Either way he receives the training he needs.
All of the information above is my own opinion based on testing I have done with this stab. Other horizontal stabilizer will have different effects on performance, flight characteristics and should be tested by an experienced pilot before putting it on your machine.
Gary G. Brewer – Gyroplane CFI-1100 hrs Flight Time Duane Hunn’s experiences with Gary Brewer’s horizontal stabilizer
Take off: Gyro doesn’t levitate on takeoff. Pilot has to add back pressure on the stick for takeoff, which slows the gyro down somewhat on climb.
It takes more stick pressure to maneuver the Gyro on climbs, turns and at high speeds.
It interferes with about 30 % of the elastomeric mast movement.
(It takes cd) double the back stick pressure when flying behind the power curve or slow flight.
Flat spin is part of flying the gyro. When done with an H stab, if you let the airspeed build up with nose down (it takes ed.) double or more back stick to pull it out.
So if your hang test is not right or you have more weight than usual in the seat you may not be able to pull out. Stick will be up against the seat.
Landing: more back stick pressure is required. It also floats longer on landing. In my opinion Gary’s horizontal stabilizer is too big and the moment arm is too far back. Would I put it on my machine? At this time, No.
Duane Hunn CFI Gyroplane Total 8000 hours gyro, 4000 hrs in an RAF.
Jim Logan’s experience with Gary Brewer’s horizontal stabilizer I flew a total of 5 hours with a horizontal tail supplied by Gary Brewer
I performed all the flight maneuvers that are in the PTS for Commercial pilot. I found the aircraft to be less pitch sensitive in level flight especially in the range of 110 mph. At 110 mph I performed a throttle chop to idle with no adverse effects. I advanced the throttle from idle to full power with no adverse effects.
The only thing that concerned me was the increase in autorotation speed. My aircraft without the horizontal tail autorotation is 1000 to 1200 feet per minute. With the horizontal tail on the aircraft the autorotational speed increased to 2000 feet per minute.
My concern is for the novice pilot not being able to handle the higher autorotational speed.
Jim Logan has accumulated over 7000 hours in helicopters and 1800 in gyroplanes.
He is a flight instructor Helicopter, Instrument helicopter and Gyroplane -ed.
All of the above was from Volume II, Issue 6, AFS Newsletter, Ask First Society, Inc. 6081 Four Star Farm Rd. Molino, F1 32577, August 2000
The editor, Lisa DeVries can be reached at email@example.com