Raf stabilator.

[Aussie_Paul]

Well the time finally arrived for me to try the new fang dangled Raf stabilator. The machine also had another Raf option, the electric roll trim as well as the electric pitch trim thjat comes with the stabilator kit.

The greatest asset is the very minimum trim spring requirements because the stabiliator aerodynamically trims the rotor. The trim spring tension would not be 1/10th of a normal Raf. This allows the pilot to easily hold the stick forward when on the ground.

Second, when the nosewheel comes up it is much easier to push the stick forward to place the nosewheel back on the ground.

Thirdly, there is a different feel to the stick having the stabiliator controlling most of the pitch trim. The stick feels a little more "solid". by that I mean that you feel like you are pushing against something less giving as a spring. This probably would/could lessen the chance of overcontrolling by an inexperienced pilot. There is no trouble over riding the stabilator and inducing over controlling followed by a PPO, and I think that if a pilot was losing it, the extra force required would be activated by the pilot out of sheer fright.

The machine was as stable as it was 5 weeks ago when I flew it with our normal stab. No more and no less.

Finally, the electric trim on the hand grip allows you to trim much more often and easily, rather than putting up with an out of trim condition due to the inconvenience of winding the wheels with the wrong hand. There is a led readout of the pitch trim position and a button that defaults the trim to a take off position and is around the 50 mph mark. You then adjust the trim for whatever speed you require.

The stabilator certainly makes the Raf a much more user friendly machine to operate BUT does absolutely nothing to minimise the gross pitch instability that occurs with a large thrust line to CoM off set that a Raf has.

Even with our stab on it I did not enjoy the couple of rides. The first trip had the doors on and the chasing of the yaw and the instability in pitch is so foreign to me now that my nerves really can't take it. And why should they have to?

Trimmed at any speed between 50 and 65 mph hands free, the first bump would begin the oscillations that would end up in a PPO if not stopped. The slower speeds and/or a clever manipulation of the power can certainly lengthen the time before a ppo would happen.

After the owner went home, I just had to hop in Hybrid with my 130 lb concrete passenger and go flying around and around and around without using the stick, and not having to use any untoward skill with the power. I could climb and descend and end up at 15 feet ready to flare.

The people out there who are happy with stab equipped Rafs, good luck to you, but you are so far from what is possible, you just do not know it yet, and you may not need the stability that is availible. I do as I am marketing a cross country in any weather gyro, so I must have the best possible.

Aussie Paul.

[Aussie_Paul]

The stabilator kit is typical of the Raf nice, neat, and tidy bits.

Aussie Paul.

[Aussie_Paul]

This is the roll linear actuator. I know the pics are a little small, but I will post a couple of the more important pics a bit larger tomorrow night.

Aussie Paul.

[quadrirotor]

In fact, from the new pieces you get, put the stab (the composite small wing) on the tail and use the linear actuator directly to trim the rotor through the spring!...and that's it... :D

[CLS447]

Paul, thanks for giving a professional & unbiased report on what this device really does! I really appreciate it.

[Whirlydog]

Paul, You said the RAF that you flew had a HS on it. My question is by adding the stabilator did it add to or subtact from the stability of that particular aircarft?
Shawn

[Aussie_Paul]

Shawn, in my opinion it made no difference at all to the stability. What it did do was give a dampened feel to the controls in pitch, in other words more stick pressure is required to move the stick quickly. This would definitely reduce the likely hood of a student over controlling as easily. If one were losing the machine in PIO, sheer terror would have the pilot over controlling the same as with the usual Raf trim spring arrangement.

I have not had time to really look in depth if there could possibly be any way that it can dampen out pitching resulting from a gust.
Our stab, fitted to that machine is an 80% fix anyway. I could not notice any improvement with stability, but the ability to trim so easily is wonderful, as is the ease of holding the stick forward when pre rotating and using the rotor brake.

The owner felt that the machine held attitude better in turns, and a number of other things, but I don't know if these are correct. I will have to spend some more time flying it from the pilots seat with the trim buttons readily available to me.

I will have to take measurements and draw a schematic so the clever guys can work out what actually happens. I would appreciate some help from Doug and/or others re this part.

Aussie Paul.

[Doug Riley]

If you have an unstable fuselage and you refuse to correct its instabilities, at least you want to avoid the instabilities' being passed through to the rotor --to the extent you can, anyway. On a typical gyro with Bensen-style head and trim spring, these instabilities do get passed through to the rotor, though. This "pass-through" can happen in at least three ways: (1) if the pilot holds the stick rigidly still (2) by means of the trim spring in hands-off or stick-floating flight and (3) if/when the rotor head contacts a control stop.

You can greatly reduce pass-through #1 using the "float the stick" technique. There's nothing you can do about #3; once the frame pitches enough that the head hits the stops, futher manipulation of the rotor isn't possible and over you go. This scenario is the one that all the trim springs, magic masts, offset gimbals and airfoils-in-the-control-system can't prevent.

Duane Hunn's airfoil stab system addresses pass-through #2. Here's how. The conventional trim spring links the control head to the airframe mechanically. If the airframe is unstable, it will pitch the wrong way and (through the spring) will tend to pull the rotor head the wrong way. If you replace the spring with an airfoil, you take away the bad influence that the airframe has on the rotor, and replace the bad influence with a good one: unlike the spring, the airfoil doesn't follow the airframe. Instead, it tends to keep the rotor aligned at a fixed angle with the AIRSTREAM. More precisely, the airfoil creates pressures in the control system that tend to produce this result, as long as you don't fight the stick too hard.

The airfoil is a partial work-around of the basic problem of airframe instability. It won't -- can't -- work once the airframe pitches far enough that the head hits the stops, though. Unfortunately, that's just what happens in a classic PPO.

(I should mention that I took the dimensions of a popular after-market HS for the RAF while at Bensen Days. As most of us already realize, such a HS, though fairly large and far back on the frame, isn't nearly powerful enough to prevent a PPO at a high power setting and sudden low-G on a stock RAF. I'll post the numbers when I have my notes here at work.)

[mceagle]

It would appear then that the stabilator tends to do a similar thing to the rotor that an anti-servo does to a full flying rudder. (ie. tend to line it up to the relative airflow).
If that is the case then in some situations (particularly manouverability) the stabilator could be counterproductive. What would it do in a vertical descent?

[Doug Riley]

Airspeed in a vertical is pretty low -- less than 20 mph (all of it straight down!). The stabilator will likely be stalled in that situation. Its drag would still be present, and would produce a stick pressure that tries to force the stick forward. That's an appropriate and stable stick pressure, given that you're way behind the power curve in a vertical. A frame-mounted HS would have the same effect. So would the spring-trimmed gimbal head.

[quadrirotor]

the russian version:

[mceagle]

That stabilator looks a hell of a lot simpler - interesting mono-shock front wheel, and the rear suspension looks different too. Could we get a look at it from a different angle?

[Aussie_Paul]

I spent a couple of hours with the Raf stabilator yesterday, and have quite a lot to report. I will try and post it in the neccessary detail shortly.

Aussie Paul.

[BenMullett]

DON'T KEEP CALLING ME SHORTLY, PAUL! :D
Seriously, be interested to know your results. Ben.

[Aussie_Paul]

and get it done tomorrow. The last few days have been a pain as I reported in another post.

Hey Ben, you on the left!!!! I can hardly call that shortly!!!!!! LOL :D

Aussie Paul.

[BenMullett]

.... so I'm not that short (wide maybe LOL :D ) - but trying to make a canard gyro fly (see canard thread) has banged my head on the (simulated) runway more often than anything else we tried. Feel shorter.

We just published John's article on the Firebird in GyroFlight - so expect a copy in the mail.

Nice to see that photo. I'll be back!

All the best, Ben

[Aussie_Paul]

What I have found with the Raf stabilator is that it is difficult to push the stick forward quickly, and to be trimmed at 60 mph, and then push the stick forward to 70 or 80 mph is almost physically impossible. A lot of almost brute force required. This means that you have to trim for each change of airspeed. For cross-country touring this is great, but for throwing the machine around, the stick forces are very high. Birdy would not be able to put up with it for a minute.

The good part is that you can’t accidentally get fast, and it stops someone from shoving the stick forward. The feeling of the aerodynamic trimming for cruising is great. The gusts and bumps still require the pilot to continually fly the machine, and while performing these often required small pitch inputs you do not feel the resistance of the aerodynamic trim.

Holding off while landing the stick pressure is very high until the speed begins to decay and the aerodynamic trim has less power. Not as nice to land as with the spring trim system. BUT it is so easy to hold the stick forward to taxy and slowing the blades down for parking.

The owner feels that holding the nose up for slow flight, 25 mph, the pressure is less than with the spring trim system. The advantage here is that the electric trim buttons are on the stick and it is very easy to change trim. The roll trim happens immediately, but the pitch trim has a 2 second delay before it begins to move, then you can fine-tune it, as the movements happen immediately. If you leave the pitch trim for some seconds then you have to put up with the 2 second delay and start again. This is a pain but it would stop someone accidentally adjusting the pitch trim. I do not think that the 2-second delay is a good idea.

The take off is great as there is no pressure much at all to push the stick forward to place the nose wheel back on the ground. The trim position indicator in the cabin has a setting for take off so that you can have the trim in the correct place every time. This position is pilot adjustable, and can also be defaulted back to the factory setting.
The stabiliator does vibrate in sympathy with the mast as it is above the “magic” bush that isolates that 2-rev upper mast shake.
Testing with our h/stab installed, it is hard to imagine how it would work without a stab.

My gut feeling is that a little less aerodynamic trimming and a little more spring trimming may be a good compromise.

One value is the difficulty in quickly pushing the stick forward.
This of course is a non-event in a properly set up gyroplane!!!!!!

The main value is the lack of stick pressure on the ground and the electric pitch and roll trimming systems. The electric pitch and roll trimming could be achieved easily with linear actuators.

For the stick forward pressure on the ground Raf problem, I have reduced the torque tube offset, and re arranged the control geometry to have 12” of stick movement instead of the normal Raf 9” or 10”.

So, at the end of the day, I really can’t see any advantage over a correctly set up gyroplane!!!!! :rolleyes: But it does make a Raf with a stab a little more user friendly on the ground, and with not having to turn those trim wheels.

I do love that electric trim though!!!!!!!!!!!! :D

Aussie Paul.

[rmcfly]

Paul,

I’m sure we all agree that the information you have gathered is valuable but it’s my belief that some of it is not accurate in describing the effects of the RAF Stabilator. I would compare testing the Stabilator on an RAF with a HS as to a patient going into his doctors office and commenting that Tylenol PM does not work any better than Advil, “really doc it doesn’t, I took the Tylenol right after I took my Advil and didn’t feel any better than usual, I slept a little better but that was all”. We all know that mixing two medications together will not necessarily make one or both work better and in some cases may even have adverse effects and I believe the same hold true for some of your results.
I have spent a good number of hours in an RAF without a HS on it and have also spent about 30 plus hours in an RAF with a Stabilator on it and have noticed a significant increase in pitch stability. Granted it did not fly for a half hour hands free but it typically did for quite a while until hit by a gust of wind. One evening we flew to a local airport in about 20 mph winds and all that was really needed were some minor corrections here and there to keep it steady. I did not find it as difficult to override the Stabilator as what you described and believe this may be due to the HS holding the position of the aircraft to the relative wind and not allowing it to freely pivot from the head but that is just a guess. At one point we trimmed it out at 90mph and landed without making any trim adjustments and then did just the opposite by trimming it at 40 and then doing some takeoffs and landings. I have not racked up nearly as many hours as some of you out there but I do know that flying an RAF with a Stabilator on it was much easier than without.
In the end I guess it comes down to what you want to do with your gyro and in my case I was pleased to see that the Stabilator had no adverse effects on maneuverability as described by some others as they have experienced with their stabs.

[Aussie_Paul]

Wheb we were flying the other day I said to the owner who is going to step the keel and lower the engine and redive, that we need to take the stab off and fly it before he steps the keel. I said to him that it was the only fair way to appraise what Raf has designed for their stabless Rafs.

I have no problem with you "one mans opinion" at all. I did not realise that I had not included that statement in my report. :o :o

Aussie Paul. :)

[rmcfly]

Paul,

I just want to clarify that this was by no means an in your face post. I just want to state my finding on the Stabilator and note that they differed in some respect to yours. I do agree removing the stab is the fair way to assess the true effect of the Stabilator and look forward to hearing what his opinion is afterwards. I believe RAF has sold quite a few of the units and wish others would give their opinions also.

Russ

[Doug Riley]

It's really important for everybody's continued health that we keep in mind what RAF's "whale tail" control-system airfoil is and what it is not. It is a semi-intelligent adjustable trim spring that senses the aircraft's airspeed and angle of attack. It is NOT a horizontal stabilizer and should not be confused with one.

The airfoil does directly what the standard trim spring-offset gimbal does indirectly -- it senses angle of attack and feeds forces into the control system that tend to keep the rotor at a chosen angle of attack. These centering forces get stronger as airspeed increases, and weaker as it decreases. (This latter quality is handy in that it reduces stick pressures you feel during ground operations... in contrast to the simple spring.) If set up properly, such a system helps to de-couple the control system from the airframe's movements -- a good thing if the airframe is unstable, and not really a good thing if the airframe IS stable.

The de-coupling is limited, though. In a full-blown PPO, the airframe pitches over faster than the rotor can follow. As the nose drops, the rotor lags behind and soon hits the rear control stop and the flap stops. At that point, any trim system that relies on rotor forces become useless -- the rotor head is already pinned against the rear stop and no further control movement is available. This analysis applies equally to the usual gimbal head, the pivoted "magic mast", the whale tail and any other gadget that attempts to stabilize an unstable airframe by manipulating the rotor. It even applies to attempts by the pilot to stop the PPO by moving the stick. Pilot skill is irrelevant in such a situation.

Without a stable airframe, PPO remains a very real possibility. No rotor trim system can affect that truth.

[Chuck_Ellsworth]

So why doesn't RAF change the design, and get rid of the thrust offset?

Chuck E.

[donshoebridge]

Chuck,

My guess would be that it would be an admittance of guilt. Looking back at the court cases where RAF has had to defend itself by saying that there's nothing wrong with the design, changing directions is going to be a big red flag.

To avoid being sued again, I think they'd have to close the doors, change the design, then start a new company so they can distance themselves from the RAF name and history.

But that's just my silly opinion.

[Doug Riley]

Don, I think you've hit the legal nail on the head. I also suspect that Igor Bensen perceived the same dilemma as the body count grew with his B-8M gyrocopter.

Air Command took a different route and simply fixed their design, however, with no apparent repercussions.

[ahancock]

Doug,
If I remember correctly, Air Command changed owners and then fixed the problem.
Alan

[Dean_Dolph]

Obviously, from a moral standpoint, that isn't a valid excuse. And from a legal standpoint it might not even be a good one. I certainly don't know anything about the law and the way the courts work these days I'm not sure anyone knows what to expect.

This was commented on on Norm's conference many times and the general feeling was that any one that sued a manf., on the grounds that a new and improved model was an admission that the previous one was faulty, had no case.

The argument is that if that was the true then there wouldn't be continuous improvements in auto safety or other consumer items. And yet, as we know, anyone can sue at any time for any reason, valid or not.

Nah, I think what we have in RAF is a collection of masochist that enjoy shooting themselves in both feet.

[donshoebridge]

Dean,

One thing to take into account, I don't think Canada has an anti-double-jepordy clause in their law books like the US does. In other words, if RAF makes the change/redesign, and the surviving family members see that as an admission of guilt, RAF can be sued again for the same thing, by the same family. Even if RAF's new path was paved with good intentions, the sue happy wolves would eat them alive. As I see it, their stuck. The only way out is to close the doors and start over.

Is there anyone here that lives in the Great White North that can confirm the laws in Canada?

[quadrirotor]

What i think to know is that when a trial is set off (judged): it can not be reopened without a very big pertinente evidence which preexisted before the settlement. :rolleyes:
Anyway, the settlement occured on the basis that the Homebuilt domain is under the whole liability of the builder of the future aircraft...The provider of the kit is only the provider of the raw materials: it is NOT an aircraft unless YOU certify yourself it is an aircraft... :eek:
What you make with the materials is up to YOU! the representation made by the provider of the kit is only a "friendly" advice unless it is signed off by a fully certified engineer!... :eek:
For me (IMOHO), if RAF sells a Tail-HStab.: it would be an option given to YOU if YOU think it is necessary or at least usefull... not a proof they were wrong...In the aviation domain, every device is a trade off, to put a Hstab could make you lose something!...It's up to you to know what you are doing!...By flying it you certify that it is serviceable!... :eek:

[birdy]

Paul reckons,

"One value is the difficulty in quickly pushing the stick forward.
This of course is a non-event in a properly set up gyroplane!!!!!!"

I reckon this is a good thing too,but how dose a "properly setup gyroplain" stop a pilot from pushing forward quickly?????
Sounds like this gadget could save alot of necks in the first hours of solo flight if it is going to make it difficult to push [or pull] quickly.A Hstab won't stop a student pilot from abrupt pitch inputs.
That's only the opinion of a S.C.G.

As far as stick pressure goes Paul,do you reckon it's better or the same as changing the offset.[for ground handeling I mean.With the extruded blades I need alot of trim tension and it's a real bastered on the ground.]

[Aussie_Paul]

Guys, I don't believe that litigation is the propblem. If a company wanted to avoid that situation, a lawyer would soon sort it out!!!!!! :D


Rafs problem is that they are stubborn, think they know everything, and can't be told!!!!!!!!!!! :mad: :mad:

I believe that it is a simple as that.

Aussie Paul

[Aussie_Paul]

I have a set of 30' blades here that you would absolutely love, and after you flew them you would not want to fly anything else.

These blades fly the same weight using 400 engine rpm less than the Raf blades. There is no change in stick pressure from 30 to 80 kts. Musterers would love them. They fly the slowest, and fastest of any blades I have flown dual at 1200lbs gross weight.

They are not suitable for my kits as they are pitch stability neutral. Have the gyro trimmed at 50kts, pull the stick back to 40 kts and let go. That is where everything stays, 40 kts. Push the stick forward to 60kts and when let go it stays at 60 kts. Nothing gets worse, just stays the same. :)

No positive pitch stability, BUT heaps of performance.

With your AK blades you really need to bring the offset down to 5/8". Jeff does not know what causes an increase in trim spring requirements, but reducing the offset will help. Even with the Raf blades I would prefer less than the 3/4" offset that the Raf has.

A quick and easy small fix for the stick pressure on the ground is to have the bottom of the upper control rods 1" closer to the mast, There is already a 3/8" hole there. You just need a couple of extra shorter bolts. This brings the stick movement in pitch from 10" to 12". 20% less pressure. The only problem is that the stick roll movement becomes 20% more and may need a shorter cross arm up the top.

If you like, I could see if I have a spare 5/8" offset torque tube to suit a Raf, and if you asked nicely on bended knee I couild lend it to you to try. :D


On a correctly set up machine, CLT, it does not matter if you shove the stick forward a bit, PPO will not develop very quickly, if at all. It you did the same stick movement with the Raf thrust to VCoG offset, and did not reduce power you will be upside down real quick. That is what I meant.

Birdy, as there is basically no trim spring pressure, there is nothing to push forward against when on the ground.

You just have to eat more breakfast!!!!!!!!!!!!!!! LOL :D

Aussie Paul.

[Chuck_Ellsworth]

Paul :

I believe I know the RAF owners better than most people in this forum, having worked at the factory and lived with Don and Linda in their home, and I can guarantee that you are right.

Don, Linda and Peter in my opinion will never change the design, that would be admitting they were wrong.

Chuck E.

[birdy]

Tell you what Paul,send us the touque tube AND the blades and I'll try both.

[Brennen]

Paul :

I believe I know the RAF owners better than most people in this forum, having worked at the factory and lived with Don and Linda in their home, and I can guarantee that you are right.

Don, Linda and Peter in my opinion will never change the design, that would be admitting they were wrong.

Chuck E.


I hope the gyro community is steering everyone away from these improperly designed machines.

[BenMullett]

It is such a pity when the opportunity to learn is missed - we all do it, me more than most :( , but my family usually put me right! ;) Mistakes (and admitting them) are all a part of progress in any endeavour.

Hey, Paul - that rotor technology sounds like a major step forward - would be interested in your thoughts on the reasons behind the described rotor behaviour.

All I've been doing with rotors so far is to take a look at some resonance phenomena - there appears to be an 'interesting' mode where the pendular frequency of the aircraft has a period near (but not quite the same as) the delay period of the rotor.

The way it works is roughly:
Cabin swings (say) left, but rotor responds when cabin has neared the end of the swing, so rotor helps cabin swing right, and so on.

X-Plane will simulate it very well - total rotor lag is around 1/4 turn of the rotor, so the frequency is a multiple of rotor speed. Looks serious on the Sim - you can lose the aircraft.

It can seem to be exacerbated in take-off, when the rotor is about to take the whole weight of the machine, and (say) one wheel lifts off. That figures, because both the pendular frequency and the RRPM will be altered with one wheel on the deck.

Interesting? Ever encountered anything like that?

All the best, Ben

PS You and Alan can expect something small in the post soon. :D

[Aussie_Paul]

I have seen you fly!!!!! :eek:

I don't need tree trunk marks on them!!!!!!!! :D

Aussie Paul.

[Doug Riley]

Ben, I've gotten into lateral PIO a couple of times. I've never had the more usual pitch-axis PIO -- a fact that I've always attributed to my lousy sense of rhythm.

My first adventure with lateral PIO was the first time I lifted off in a gyroglider. I was soon swaying back and forth, pumping madly at the stick and no doubt making things worse. A friend snapped a picture with the machine in a 30 degree bank while I had the stick deflected all the way in the opposite direction. I was "saved" by plowing into a snowbank on the side of the runway. Luckily, I got away with no damage to me or machine. My next tow driver took it easier and I progressed from easy crow-hops on to smooth flight without any additional trouble.

The second incident was about 5 years ago when I started flying my then-new Gyrobee. I did quite a bit of lateral wallowing about in the first few hours. The (overhead) stick on the Bee is very long and hence rather insensitive. The ratio is over 1" per degree in both axes. It takes a large, positive stick movement (followed by the usual momentary reverse pressure to arrest the roll) to produce a crisp response. It took a couple of learning sessions to get things smooth.

[BenMullett]

...and valuable information, Doug. Thanks for that.

A sense of rhythm and perhaps a touch of "Getting into the swing"? ;)

What we think we are seeing is a fixed-stick oscillation, and although hard to replicate in real life, we have seen it happen with some gyro-kites under certain conditions. They are a real boon to rotor management training - Craig Wall put us onto it here in the UK, bless him.

The resonance is probably (hopefully) out at the extreme corner of the flight envelope for most full scale machines, but I want to do the maths in detail since there may be an unexplored coffin corner here. Or then again, maybe it has already been defined and I didn't (yet) read the right reference!

One difficulty is estimating the instantaneous centre of the movement. The Sim seems to be rocking around a point slightly below the rotor.

Hmmm... Gyro-glider? What sort of weight and blades? Would be interesting to know.

We have also seen a pitch oscillation like this at very high altitudes, where all aero forces are less effective. Rotor system sims that are stable in pitch at lower altitudes can go into pitch instability in thin air - even a stab is less effective. H U G E stab will cure this in the sim, but only a BRAG configuration will cure it in roll - some BRAG info at www.BRAGgroup.com.


All the best, Ben.

[birdy]

I'v never heard of lateral PIO before.
Heard plenty of pitch PIO.
I reckon it's obviose what causes it,delayed responce by the rotor,and I'v never heard/read anything about this in any flight training .
Shoot me if I'm wrong again please.

[Doug Riley]

Birdy: Igor Bensen reported a lateral PIO episode in a gyroglider in one of his columns in the PRA mag in the early 70's. It makes sense that it could occur; in the roll axis, we have no stabilizing aerodynamic surfaces at all (not even the much-scorned rock guard) and we don't have the offset part of the offset gimbal helping us, either. Of course, a Cierva-style winged gyro would have lots of aerodynamic damping in roll.

Ben: my first incident was with a classic 60's Bensen gyroglider: spindle head, wooden blades, short mast, overhead stick. The Gyrobee incident was with a gimbal head, Rotordyne metal blades and a Gyrobee frame having a six-foot mast.

Both these incidents were PILOT induced oscillation. We need a name for craft that are susceptible to this sort of pilot-powered misbehavior. "Unstable" is too harsh; the machines won't go into these oscillations on their own, even if disturbed by a single or double control pulse. What they DO have is a reaction time (or lag) that's rather close to the reaction time of some of us "slowhand" types, and a pretty weak damping effect. That, plus the uncommanded yaw-roll reaction caused by the towline in the case of gyrogliders, can result in a man-machine SYSTEM that is unstable overall.

[birdy]

Doug,I'v never flowen a gyro glider but you are spoton with the control LAG causing PIO,in pitch and lateraly.The machine should never be blamed for the faults of the pilot no matter how stable/unstable it may be on ether axis.
I'll defend these machines to the end,coz they are the easest and safest to fly in the rough stuff.
I'v said many times,an idiot will kill imself in any machine,even a wheelbarrow.[if e drove it off a cliff and forgot to let go e would die,that's an idiot]