raf 2000 rotor stabilizer

[rotorhead06]

Has anyone flown a raf 2000 equiped with there new rotor stabilizer, they say that it provides better stability than adding a horizontal stabilizer.
Would appreciate any information on this.

Thanks rotorhead06

[chuter]

I took over 20 hours of training in a AAI modified RAF with no stabilator and with a horizontal stab. I then took 3 hours of training in an RAF with a stabilator and no horizontal stab.

My opinion is that the horizontal stab reduces the workload a LOT.
I would personally choose the hs over the stabilator any day.

As far as I could tell the stabilator just acts as a trim system. The fuselage rocked in pitch a lot more without the hs.

[Harry_S.]

Herman;

Welcome to the forum.

Are you an RAF owner, or, are you thinking of buying an RAF?

There are a lot of RAF's flying with just a stabilator...with both, a stabilator and a stabilizer...with just a stabilizer...and just stock, with neither a stabilator nor a stabilizer.

IMO...you need to ask a lot more questions.


Cheers

[rotorhead06]

I am debating on building a little wing or a raf2000, there is a lot of talk about the raf not having good pitch stability and being more subseptable to PIO and PPO with out a horizontal stabilizer.

After visiting their website you get the impression that their rotor stabilizer helps with this problem and since they don't recommend a horizontal stab I assume they believe their system works well to help with stability

I am new to gyros but not to helicopters after 21 years in the army in helicopter maintenance I have a lot of hours of stick time. I have been trying to read as much as I can about gyro"s and understand there operation. There is so much to read.

Thanks for any info
Herman

[C. Beaty]

When considering the purchase of an amateur designed anything, the first order of business it to take promotional hype with a grain of salt.

Smiling Bob the Enzyte man isn’t the only scam artist on the prowl. The difference being that while Enzyte most likely won’t do any good, it most likely won’t kill you.

[Doug Riley]

Herman:

The behavior of the fuselage in any rotorcraft, but especially a gyro, has a powerful effect on the behavior of the rotor.

It's often said, quite erroneously, that what the body does is irrelevant. We might wish that that were true, but it isn't. Here are some reasons why the body must be stabilized to track the aircraft's path of travel:

1. The control stops are attached to the body. If the body swings in a particular direction without the rotor going with it, the body will force the rotor to follow it once the control stops are reached.

2. If #1 occurs and the body is pitching very fast, it can force such a large and sudden cyclic pitch input to the rotor that the blade that gets increased pitch will stall. This isn't likely with normal manual control inputs, because the rotor will hammer back through the controls -- but the body is stupid and doesn't care about hammering. If a blade does stall, it will normally be the retreating blade. The rotor will typically flip into the prop and tail, and you will die.

3. The Bensen-type head on RAF and other gyros uses a trim spring that's attached to the body. This, again, manipulates the rotor based on pitching movements of the body, without pilot input.

4. Friction in the controls, and the tendency of most pilots to hold the stick still, provide some degree of coupling between airframe and rotor.

For all these reasons, a vane linked to the rotor head does not address a fundamental ingredient of pitch stability -- an airframe that stays aligned with the flight path. The control vane manipulates only the rotor, not the aircraft's body. A frame-mounted HS is the normal way to get the frame to exhibit "arrow stability" -- the tendency to stay aligned with the flight path.

The RAF airframe is particularly UNlikely to stay aligned with the flight path. The large cabin is somewhat de-stabilizing by itself, but much more serious is the very large vertical offset of the prop thrust line from the aircraft's center of gravity. This creates a nose-down pitching moment on the order of 600 foot-lb. at wide-open throttle. The rotor can counter this pitching moment except when G-loading is reduced. In those circumstances, the frame pitches violently nose-down, starting the sequence of events described in #1 and #2 above.

There have been many such catastrophic flip-and-crash accidents in RAF gyros and others with the same flaw. Gyro people commonly refer to them as "power pushovers," PPO's for short. The cure is a stable airframe, not merely a stable rotor. The autorotating rotor, wonderful as it is, takes a nap now and then in low-G events, leaving the frame to tumble or go straight, according to its own stability.

[Gyropilot007]

Herman:

I have an RAF-2000 with both a stabilizer and a stabilator. The RAF-2000 in which I had my flight training had only the stabilator. In my very humble opinion, the RAF with only the stabilator had no discernible negative characteristics but it did seem to pitch a lot in the wind.

On my RAF with both the stabilizer and stabilator the flying is smooth as silk. It is very stable, even in gusty conditions. But in addtion, I did do the drop keep modification and lowered my engine by six inches.

I hope this is of some help to you.

Bob

[Brad_King]

Originally Posted by Gyropilot007

Herman:

I have an RAF-2000 with both a stabilizer and a stabilator. The RAF-2000 in which I had my flight training had only the stabilator. In my very humble opinion, the RAF with only the stabilator had no discernible negative characteristics but it did seem to pitch a lot in the wind.

On my RAF with both the stabilizer and stabilator the flying is smooth as silk. It is very stable, even in gusty conditions. But in addtion, I did do the drop keep modification and lowered my engine by six inches.

I hope this is of some help to you.

Bob

In other words its no longer the RAF the company sells but one that has been modified to make it EAISER to fly and SAFER at the same time.

Oh, did they company mention that with a horizontal installed the aircraft is more efficient because the rotor can fly at a flatter angle reducing drag by not having to counteract all that thrust offset. Hey, less engine RPM less, 3.00 gal gas needed.

So, you don't believe people who know aerodynamics, and have no financial interest in your purchase, telling you they have the physics to back up their positions. While, RAF MARKETING INC is telling you that in their OPINION the RAF 2000 doesn't need a horizontal, well you know they wouldn't mislead you just to make a sale. You can trust them right?

Well how about easier, cheaper, more fun to fly, and by golly safer as a little added extra too.

It's your decision. Make up your own mind. I know what I would do.

BTW The RAF owners rightfully will tell you that there are 100's of RAF's flying racking up 1000's of hours without a fatality and that's a fact.

The other fact is that the vast majority people who WERE killed in an RAF was due to PPO. Not many just a few. But they didn't have to die that way.
It was preventable. You decide.

[Aussie_Paul]

.... and think it worth posting.

Norms Forum 9/12/03.


I just read Paul Bruty's magazine article written in Jan, 2001. Paul had worked and perfected a stab that he was extremely excited about because of how it helped with the RAF stability and training issues. He mentions flying in windy, gusty conditions with turbulence. The stab stabilized the RAF and made it more enjoyable and safe with a lot less pilot input. I am assuming that was without any thrust line changes on the RAF. Now all I hear is the RAF is unstable without a clt kit on it. What has transpired since 2001 when The RAF flew through turbulent windy conditions with the "band aid fix" stab?
I 100% agree that all gyros should have a stab. But if Paul Bruty, Ron Menzi, and other famous gyro pilots just a few short months or years(depending on who you listen to) all felt and many still do feel that a good stab will conquer most air issues, then why change to clt? Is the change that profound? I have flown both CLT, stabless, and high thrust line gyros. I will go on the record that the CLT air command didn't oscillate in wind gusts. I can't say the stabless RAF did either. (35 mph with gusts) and my RAF with a stab flies fine in wind and thermal conditions. I had to learn how to react to these wind issues. I found Jim Logan's advise the best. A little back pressure does wonders! It smoothes out the bumps.
To make my point. Here I go. There is no decision on whether you should have a stab. That's a given. Should I put more money in a CLT conversion, I am not convinced yet. Again I ask the question. Is the change that profound? It would have to be a huge difference for me to change the beautiful RAF I have. I would like someone with experience write a test pilot like report discussing their own experienced opinion of the difference of stab verses clt with stab. I experienced little difference. How about you Jim Mayfield? There are several Groen brothers’ conversions done, yet the only input I have seen is “There was a real difference". Like how was it different? Did it fly faster? Did it fly like an airplane? How did throttle inputs make the machine react? Come on some one. A verses B. Inquisitive minds want to know!!!!

LOVE TO FLY!

This message was edited by LARRYE.BOYER on 12-7-03 @ 5:44 PM
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Larry: I have asked the same questions you have as I now am looking forward to flying my RAF next year with a stab. I have talked to many pilots that have LOTS of experience. Paul Bruty who has thousands if hours has a glowing report on how nice the RAF is to fly in all kinds of winds. ..It’s on the RAF forum. I talked to several pilots at Mentone and Shelbyville. All concurred that a RAF with a good stab is a nice flying machine.

I watch guys like Ron Menzie and other high time pilots and it was more than enough to convince me that I will be very satisfied. I will post from time to time as I did while flying my Air Command.

Larry: I enjoy reading your posts and have a safe and fun 2004 season.
Stan Foster
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Right on Larrye and Stan. At that point in time that article was true. I was as happy as can be, and accepted that what we had achieved was acceptable.

When I started to think about my own design after RAF would not even discuss the major safety issues, I thought "well how about I try this CLT thingie".

By finding a gearbox with the correct ratio I was still able to run a 68" prop. I stepped the keel 4", raised the engine 7" and turned the gearbox around so that I had lowered the thrust line 5". How did I get 5" when the step in the keel is 4"? RAF run 2" prop to keel clearance and minus 2" prop to rotor clearance!!!!! I just reduced the prop to keel clearance to 1" which is ok.

Because we had changed the rotation of the prop we had to make new tail feathers so we increased the size by 30%. This really improved the doors on yaw stability.

The first tests were done with RAF rotor blades and rotor head, RAF cabin and nearly all RAF airframe.

Without a stab this modified RAF flew so much more stable than the RAF with a good sized stab.

The test being trimmed hands off in cruise at 60 mph, then jam the power to WOT. The speed would increase approx 2 mph and then the nose would rise a little and the machine would climb at 60 mph. That proves you have a CLT aircraft not relying on a stab to perform some of the work.

Some side stick pressure was required to compensate for the increased torque at WOT.

Next we fitted the stab and I was able to perform the stick fixed testing of locking the stick in pitch at 60 mph after lift off, and fly the circuit right down to where I had to flare and that would let the locking stick drop out. Now please take notice of this. This is flying a pusher gyro with no pitch control at all except for take off and landing.

Now back to where I was happy with a RAF with an effective stab. I was happy BECAUSE I had not flown anything better, and I can excuse all these "Raf with stab" pilots for thinking the way they do. The stab is such an improvement but the step to CLT with a stab is a much bigger step.

Probably 90% of gyroplane pilots have only flown gyros with varying degrees of instability, they have never flown a truly pitch stable gyroplane, as I had not until my experiment and experience with CLT and a stab.

Most people will be happy with an effective stab on a RAF, BUT it is not the best that can be achieved, and it is not truly pitch stable. The instability that is left when you add a stab to a RAF is low enough to allow the pilot to stay ahead of the gyro.

It is not the experienced RAF pilots who are the best judges; it is their students who have flown a non stab RAF, a RAF with a stab, and a RAF with CLT and a stab.

This is a report of a recent trip with Hybrid to help some people.

Two pilots who trained with me approx 6 years ago, Bill and Boyd, and Boyd’s son, Aaron flew with me. They were ecstatic with the pitch stability!!!!!!!!!!! I would take off, and as we climbed through 30' I would let go of the stick and climb to 500' hands free. I took Aaron before I took the two pilots. Aaron has now done 15 hours dual spread over 5 years. He has experienced the stabless RAF, the RAF with the effective stab, and now Hybrid, which is a CLT RAF with stab. He could not believe the difference. Chalk and cheese by 100 times was quoted.

I had been flying hands off for the trial instructional flights, (showing off), and when I took my hand off the stick at 30' with the son, he said, "it really does fly hands off". Obviously when I am flying there is a lot of chatting going on!! I gave Aaron control and he flew around with out any trouble at all. When we got back, his father and Bill could not quite comprehend the excitement.

I then took Bill and Boyd flying and they now want their machines to be as stable. These guys are on their own, with not a lot of hours, and the machines I let them build 7 years ago are terrible. It was a shame that I did not know then what I know now. The conditions with the hills around where they fly have them on the edge of their seats. I gave them each the info to rearrange the geometry of their gyros. Mostly it is, turn the engine or gearbox around, step the keel, shift the tail feathers further back, and to make a suitable stab.

I hope that this puts into perspective my 2001 RAF with stab stories.

Aussie Paul.



It is always possible to fly an unstable machine, but not for everyone. Even for a very good pilot an unstable machine is more dangerous than a stable machine.

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Paul! That is the BEST!!!! response I ever got on this forum. I hope everyone with a RAF reads it. No, I hope everyone with a high thrust line reads it! If you were an insurance salesman trying to convince me why I need more insurance when I think I already have enough, you get the sale. This is why I respect people like you. It's not just that you speak from experience; you take your time to help others with so much less experience better understand. My hat off to you.

LOVE TO FLY!
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Aussie Paul.

[Rene Genest]

I have seen Michel Valliere killed himself last autumn in his RAF2000 with this rotor stab....He as no other horizontal stab.

[C. Beaty]

RAF and their dealer/CFIs are either too stupid to understand or too callous to care that the so-called rotor stabilizer does not address the inherent flaw of the design.


Machines without a horizontal stabilizer and with a large offset between propeller thrust line and CG are always tail heavy, i.e., the rotor thrust vector must always lead the CG to balance propeller thrust line offset, whatever the dangle angle.

All tail heavy aircraft; whether gyro, fixed wing or blimp are inherently unstable. Response to gusts must always be in an unstable direction.

RAF’s “stabilator” and the offset gimbal rotorhead work in about the same way; stick free stability is improved by either; fixed stick stability is unaffected.

[Doug Riley]

Michel was a low-time gyro pilot who pushed maybe a little too hard to become Quebec's local gyro CFI. His accident was a classic power pushover, or PPO. PPO is caused by instability in the airframe. As discussed above, the control vane does not address this problem -- hence the crash.

[Rene Genest]

Yes, Michel was a low time gyro pilot and he would probably still there if he had a Dominator like your's rather than his RAF.