View Full Version : CLT training
06-06-2004, 05:30 PM
Would a person trained in a CLT gyro be able to safely fly a gyro that is not CLT?
06-06-2004, 06:30 PM
The biggest thing you will have to learn in a non CLT machine is how to feel the gyro becoming unstable and being ready to immediately chop or reduce power and to pull back on the stick to " stablize " the gyro. In a CLT machine that is stable there will be no reason to do this and therefore the instructor may not teach this part of gyro flying. Otherwise a gyro is a gyro and it will fly the same so you shouldn't have any problems.
06-07-2004, 07:17 AM
" you shouldnt have any problems"...........
........until the bunt starts.
And then it is all over anyhow.
06-07-2004, 07:41 AM
Bart, I agree with Ron. Most of my training was in non CLT machines. I now fly a CLT machine, but don't think I would have a problem flying any of the machines I trained in.
06-07-2004, 08:21 AM
One of our club members learned to fly a Gyro with a Horiz stab. He flew it well for several years. It was the only gyro he flew.
He purchased an older model Air Command with out a horiz. stab. The second time he flew it, it was about a 1/2 year later, he killed himself in it.
The key point in bartc150's post is "safely". I would be uncomfortable with someone who only flew a CLT gyro. Because he might not have the automatic responses necessary to keep from PIO and recover from PIO. Add some winds and gusts and,,,,,,,,,,,well, I can imagine what could happen.
Bart, I would ask what type of gyro would you get? New or Used?
If used, do you have somebody who could check it out for you and test fly for you.
I think a more accurate question might be - would a person trained in one type of gyroplane be able to safely fly another type of gyroplane.
Different gyroplanes have different flying and control characteristics. Avery pilot needs to transition himself from one gyro to another by slowly learning the new gyro's flying and controls. This transition would be easier and faster going into a stable gyroplane, than into an unstable gyroplane.
It could be done safely, though. It only takes more time and practice.
06-07-2004, 08:36 AM
Well stated, Chuck R. and Udi!
06-07-2004, 08:40 AM
My answer to the original question is no.
Doug, you must be tired from a long weekend of flying... I don't remember you posting such short answers.
The problem with the original question is that it is not well defined. Technically, a Magni gyro is not a CLT gyro; yet, it is more pitch stable than some CLT gyros. Replacing "CLT" with "pitch stable" in the original question will make it more meaningful.
06-07-2004, 10:13 AM
Udi: Sailing, actually. Same thing.
Yes, a craft such as the Gyrobee and perhaps the Magni (I don't have enough time in them to be a good judge), equipped with a properly down-loaded HS and having only a small thrustline over-sling, will fly like a CLT machine.
They are the exceptions, however. Most high-thrustline gyros, whether they have a HS or not, have a significant nose-down moment that's only balanced out by rotor thrust pulling up on the nose. This makes them statically unstable in pitch. Among the consequences are these: (a) forward stick pressure is needed in turns, (b) the nose gets progressively lower as the craft speeds up, and (c) the nose pitches the wrong way in turbulence. In general, the pitch behavior is the opposite of what someone trained in a FW or CLT craft would expect.
So I think that "no" is a good general answer. Maybe with a footnote?
06-07-2004, 10:47 AM
Please explain: "the nose gets progressively lower as the craft speeds up". How would the thrust offset cause this to happen?
Are you talking about only while the gyro is accelerating or while it is flying at steady but higher speeds?
06-07-2004, 11:08 AM
Ken: Assume level flight in a high-thrustline machine at cruise speed. Assume also that the machine's PPO moment is not completely countered by a HS or other aerodynamic device. This means that the rotor thrust is being used to counter the PPO moment.. or, IOW, that the rotor thrust line is ahead of the CG as long as there is engine thrust.
Now add power but continue to fly level. As the gyro flies faster in a steady state, the rotor flies at a shallower angle relative to the horizon (a shallower angle of attack). The pilot experiences this as a need to add forward stick to prevent a climb as he powers up.) If the airframe were to maintain the same stance in the air, this foward or levelling movement of the rotor would bring the rotor thrustline back toward the CG. This would reduce the nose-up moment created by the rotor thrust, at just the time when MORE nose-up moment is needed (because power has been increased to achieve the higher airspeed). The result? For everything to stay in balance, the nose must drop enough so that the rotor thrustline stays enough ahead of the CG to counter the PPO moment.
This effect is very noticeable in a high-thrustline machine with no HS... and it's rather scary. The nose can get so low that you feel like a kid riding in a wheelbarrow about to be dumped forward. With any HS (even one that's no tuned to counter the PPO moment automatically), the effect is less noticeable but still there. In a machine that's aerodynamically well-balanced, the nose position stays level as you speed up in level flight.
You're right that nose-down moments created by pods, landing gear and other stuff in the airstream depend only on airspeed, not on power setting. The effects of these objects will be felt just as much in a power-off dive as in power-on level flight. The effects of high thrustline, OTOH, disappear when power is cut off... hence the old advice to reduce throttle if you get into trouble.
06-07-2004, 01:05 PM
I think I see what you are saying now.
You said: "the rotor thrust line is ahead of the CG as long as there is engine thrust."
I have always thought that the rotor thrust line is through the CG regardless of the amount of thrust or speed of the gyro, and that it could not be in front of the CG unless the HS pushes the tail down to swing the CG forward (or some other force acting on the gyro, like low drag).
I wish Chuck Beaty, who I respect for both his knowledge and his ability to explain things clearly, would clarify this. Chuck, am I out of line again?
06-07-2004, 01:07 PM
to your question no. you need to get training in a RAF 2000 without HS. My question is why do it at all.
06-07-2004, 01:21 PM
Ken, if the prop is pushing above the CG, then of course it's trying to push the nose down. That is, it's producing a nose-down moment. What keeps the gyro from reacting to this nose-down moment and flipping forward? An equal and opposite nose-UP moment.
Where does the nose-up moment come from? It can come from a HS if the HS is sized, located and set to produce such a moment. If there's no HS, or if the HS doesn't meet this criterion, what ELSE can produce the nose-up moment?
In practice, the rotor produces it. As the prop thrust rotates the frame in a nose-down direction, the rotor thrust line stays put. As a result, the CG moves down-and-back relative to the rotor thrust line. The CG ends up behind the rotor thrust line. In steady flight, the distance by which the rotor thrust line is forward of the CG will be just enough so that rotor thrust times this distance equals prop thrust times the distance from the CG up to the prop thrust line.
Example: A gyro has a thrustline 6" above the CG. The prop makes 300 lb. of thrust. The prop is therefore making a nose-down moment of 150 ft.-lb. (300 ft. x 1/2 ft.).
If rotor thrust (which is slightly larger than gross weight) is 550 lb., then how far ahead of the CG does the rotor thrust line have to be in steady flight? It has to be far enough to create a nose-UP moment of 150 ft.-lb. 150/550 = 0.27 feet, or 3.27 inches.
06-07-2004, 02:24 PM
"if the prop is pushing above the CG, then of course it's trying to push the nose down"
You say "of course", but I can not see any nose down force.
When in steady level flight at any speed the engine/prop produces a forward thrust in line with the prop, not a nose down thrust. Gravity pruduces a down pull directly on the CG. The rotor produces an upward and rearward thrust to balance both the gravity and the prop thrust. The rotor thrust is also pulling directly on the CG.
I looks to me like the prop can not produce a nose down thrust, unless the the rotor stops its drag (like negative G) and the gyro rotates forward around the CG allowing the prop to then produce a downward force.
Doug, no need to respond. I don't want to argue the point. I'll just think about it and try to figure out why we see things from two different perspectives. I'm probably wrong, but it will take me awhile to figure it out.
Thanks for the discussion.
06-07-2004, 02:41 PM
Doug: I always find your posts informative and always done politely. I have posted many times how I feel my RAF2000 with my Parham stab handles nice. I probably am wearing out my welcome posting such statements and lots of pictures of pure enjoyable flying my machine is giving me.
I definately have to hold back stick in turns...and have tested this at all speeds to 85 so far. I had a post where I posted some pictures of my checking the inclination of my dash with a Warp drive level. It showed the keel flying at a consistent 2 degrees nose down at speeds of 55..65..75..and 85. I did not feel the nose coming down at all while using the seat of my pants indicator...but I wanted to REALLY know for sure...so I used the level and it varified what I was feeling.
I fly in all kinds of winds and have been out many afternoons when the ultralights just would not fly....and I just notice a little rolling action. I recall just slight corrections to the cyclic....but nothing that would prevent me from enjoying a 100 mile flight in it.
One thing I have never seen addressed is in regards to the little RAF cartoon doing a buntover. It shows it bunting over in just a very short period of time..like one and half seconds or so. I understand the math on the HTL causing the buntover.....but it is based on the rotor becoming completely unloaded in a downdraft.....and then the FULL thrust of the engine is used to compute the buntover time with the unloaded rotor. What I havent seen addressed is how much less thrust the engine would be putting out in this sudden downdraft that completely unloads the rotor. I know the engine would not be putting out the full thrust at this time....but I never see this reduced thrust in computing the RAF buntover time. Again..the examples are always with 0% rotor thrust...and 100% engine thrust.
Doug: Any thoughts on how much engine thrust is reduced during a downdraft that completely unloads the rotor? I realize that flying at 30 and flying at 80 would present different answers....thanks for any inputs on this.
I just still am confused as to the extent of posts that make it sound like these machines are so difficult to fly. I can honestly say the more I fly mine...the more confused I get. :D
06-07-2004, 02:48 PM
Ken, even though there's no need to respond, I'll do so anyhow.
A basic law of mechanics (that's the branch of physics that deals with everyday objects acted on by forces) is this: Picture an object floating in space, with no forces on it. Now apply a force (a push or pull) to this object. Assume that the line of the force passes precisely through the object's CG*, The object will experience an acceleration that is in a straight line and in the direction of the force you apply.
If OTOH you push/pull along a line that doesn't pass through the object's CG, the object will, in addition to acceleration along a straight line, experience an "angular acceleration." That is, it will tend to begin to rotate. The object will be experiencing a moment or torque, resulting from your off-center force.
You can see this effect by floating a beach ball in a kiddie pool. Push on it with one finger. If you aim your push right through the center, the ball will slide away without rotating. If you push off-center, it will spin.
Applying this rule, the prop applies zero rotational force to the gyro only if the thrustline passes through the gyro's CG. If the thrustline doesn't pass through the CG, the prop thrust is applying both a straight-line force and a moment (rotational torque). The gyro will rotate in response to the moment unless a countering moment is there to prevent it. That's where the HS or rotor thrust comes in.
It's critical to understanding this stuff to be able to picture the effects of both off-center and on-center forces. Off-center forces always result in torques. If the object is going to avoid rotating, it can only do so in the presence of an off-center torque if there's an equal and opposite off-center torque. Without that opposing torque, it's gonna start rotating.
* more properly, the center of mass (CM), but they are located in the same spot.
06-07-2004, 03:02 PM
Stan: Maybe you saw the rough numbers I posted on the Parham stab. At higher speeds, it has reasonably close to enough HS power to offset a less-than-full-throttle thrust. What helps, too, is the reduction of thrust (at a given throttle setting) that occurs at higher speeds with most gyro props. The worst case with an "almost enough" HS is probably a full-throttle climbout at slowish speeds while plowing into a downdraft.
I wouldn't expect a downdraft itself to reduce thrust much at all. What it will do is cause the slipstream coming off the prop to deflect down a bit and point more toward the ground. The effect is pretty minor, though, since (for example) a 1500 ft./min. downdraft is only 17 mph, while the prop slipstream on a gyro at cruise might be 80-100 mph or more.
A downdraft that produces zero or negative G isn't all that uncommon on a thermally day in hill country. I've hit some myself -- both in a fixed-wing ultralight (bumpy but not scary) and in an unstable, no-HS gyro (scary).
06-07-2004, 10:55 PM
If one learned to fly in a Sparrowhawk and then bought or built and flew an RAF without a stab, I'd give him about 1 minute (if that) of life left after the wheels left the runway.
06-09-2004, 01:09 PM
Great info guys. The Magni is too far out of my price range, but a Dom or a Monarch is much more affordable on a firefighters salary. The reason I asked the original question is the nearest instructor teaches in a Sparrowhawk, but I might find a good deal on a used gyro, but probally won't be a CLT or a Magni. Seems like I must treat these machines individually and seek final training in what I end up with.
Again thanks for all the great info. I read this entire site everyday at work so some post may take a few days to respond. I've been hooked on gyros since my first ride at B days, and can't wait to get off the fence and join the herd.
06-09-2004, 04:31 PM
I hope that soon you will not be able to find training in a HTL gyro. It is not like an option in a car that you can do without. Train to live, live to fly. just my 35 cents
06-09-2004, 05:38 PM
bartc150, whatever machine you get, modify it to be as stable as a sparrow Hawk.
Aussie Paul. :)
06-10-2004, 09:59 AM
Hi Ken, (the young, energetic, relatively urbane ken that lives east of San Diego)
Our entire concept is based on the following tenets:
1. Motions of an aircraft in flight are about the CG.
2. There can be no moment about a hinge (CG) without an arm.
3. If there is an arm and a force there will be a moment (torque)
4. Force applied through the CG will (can) translate the object to which the force is applied, but can not apply a moment about it's CG.
An analogy: Go to a door in your house that is closed but not latched. Push on the hinge (CG) you may be able to translate the entire frame outward, but you will not be able to swing the door open (apply a pitching moment).
Now move your hand out on the door several inches from the hinge. Of course the door opens effortlessly by applying a force on an arm about a hinge.
We believe that a gyro with an offset thrustline must have a pitching moment applied. We believe that if there is no H stab to overcome, or help overcome that pitching moment that the only appreciable force available to prevent the aircraft from doing forward loops is the rotor thrust vector being ahead of the CG.
We believe that, in any configuration practical, that the rotor thrust vector ahead of the CG is an unstable configuration.
Chuck and Doug are so much more articulate in these things that I was almost hesitant to post.
06-10-2004, 12:16 PM
I have to agree with Ken . If you trained in a stable machine and go and buy an unstable machine you will be dead. If you learn in an unstable machine when you jump into a stable machine is very easy.
Waht can we do first plant the seed of fear in the student mind. Have them alwasy awake when training in a stable machine and force them to understan flight configurations and transition. That a solo endorsement is not a certification you can fly anything any day.
The when knowleadge is build the fear seed will be converted to understanding and respect for the aircraft youflies.
my 2 cents
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