Left Turn, Right Turn which is more stable at 60*

dragonflyerthom

Platinum Member
I have observed that a left turn seems to be more stable on my machine. I am thinking this is because of the direction of rotation on my Gyro. It turns clockwise if you look up. Wouldn't it be the opposite if it turned the other way?
 

OzyRuss

Senior Member
I've found over the yrs, "most" pilots are LH turners, seems to just happin.
Stick a newbie into the seat, commence training, sure enough they tend to turn left each time.
No big deal, then after a few hrs etc, i get em to turn RH only.........that's when things can go pear shaped a tad............usually rudder balance is all gone, ............interesting tho

Same when gettin em to fly using left hand on the stick...........interesting reactions by some..........geez russ, bugger this left hand stuff.

As to the mechanics of stability etc, right verses left turns ?????????
turn whatever way.........just deal with it
 

birdy

Newbie
The biggest difference between left and right turns in gyros is the effect of the props gyroscopic resistance. One way it unloads the rotor and the other it loads it.
If you dout it, then climb to a safe alt and chop the power to idle [ next to no prop gyroscopic effect] and youll find theres no difference left or right.

My rotaxs mean its 'harder' to turn left than right, because the rotor has to counter the props force as well as pull you round the turn, right turns are easy, if the taps open. If i have to turn hard to the left, ill chop it, rip it round and fly off, easy. The tighter the turn the more youll notice it, coz your tryn to change the prop blades flight path faster, meaning they will resist more.
 

C. Beaty

Gold Supporter
You would find, Mr. Bird, that if you had a full span vertical tail, it would make no difference which way you turned.

When the prop disc is rapidly yawed, its gyroscopic precession creates either nose up or down reaction as you know from having played with a spinning bicycle wheel.
 
I have noticed that a hard left rudder on my SparrowHawk or my RAF would cause the nose to pitch down....and pitch up with a hard right rudder.

This goes exactly with what Chuck B just posted. Both props turn ccw looking from the rear....so a hard left yaw....looking from the rear of the prop is pulling it back at the 9 o'clock position. Gyroscopic precession makes it react 90 degree later...or like its being pulled back at the 6 o'clock position. This causes a nose down moment.

A hard right rudder input...again looking at the rear of the prop...causes the prop to be "pulled" at the 3 o'clock position...and once again our faithful gyroscopic precession law has the reaction 90 degrees later in the direction of the prop rotation...and the action noticed is the prop path being pulled at the 12 o'clock position. This pulls the nose up.

Stan
 

Vance

Gyroplane CFI
Hello Stan,

Your vocabulary and delivery is progressing toward the technically astute.

Thank you, Vance
 

Heron

Platinum Member
I do have probelms turning to land right handed!
I will have to pull a little stronger and keep it a little longer to find the correct alignment.
Left hand is ok. NOw I need some more air time and emergency procedures to go solo! :D
Heron
 
Last I checked.

Last I checked.

The prop may have something to do with turns but I thought that the ROTOR was flying the machine and control inputs had a lot to do with the ease of turns.

Gyroscopic precession is a major force of course as it is applied to the rotor when it is loaded in turns. At least for myself it is easier to pull back on the stick and level out in a left hand turn than to push forward slightly on a right hand turn to keep the nose down.

Most students are taught left hand turns from the start because they are easier to perform and human nature always takes the path of......plus most patterns are left hand.

If that is in fact what we are talking about.

Jonathan
 
Chuck or some of the other think tanks.... I have a router that turns at 30,000 rpm. Talk about a hand held gyroscope. Its neat to try to roll it on say the x axis quickly only to have it hopelessly rotate on the y axis.

I have never really ever read or heard the exact explanation of why this reaction occurs 90 degrees later in the direction of rotation. But I will type here what I have deduced is the reason why this happens. Please correct me if I am wrong...or add whatever you can.

If a disc is spinning ccw looking down from above.....and you appy pressure at the 3 o'clock position...it will of course react by going down 90 degrees later at the 12 o'clock position.

My feelings on why this occurs is that when you are applying pressure at 3 o'clock....that point has the highest velocity relative to your finger...and it instead "starts" deflecting its tilt there...and just simple geometry has it moving its greatest deflection at 12 0'clock where the speed relative to the pressure being applied at 3 o'clock is least.

Chuck or Al or Doug,or Udi......is this a fair assessment? My pea size brain burned a lot of calories coming to that simple explanation. I would like your input either correcting me or adding to it.

Thanks
 

C. Beaty

Gold Supporter
Astute, Vance, is an adjective. If you need a noun, you might try astuteness.

You wouldn’t say Stan is approaching lovely, but you might say he is approaching loveliness.

There; you have my English lesson for the day.:rolleyes:
 

C. Beaty

Gold Supporter
Stan, I wish I could give a simple, concise explanation of precession but I can’t.

Gyroscopic precession is an extremely complex phenomenon for which there is no simple explanation. College level physics textbooks offer no 10 word explanation. First year physics texts often give “simplified” explanations with vectors of wheel angular velocity pictured as either right or left handed screws depending upon direction of rotation and vectors of precessing torques added at oblique angles. They go on to state you’ll have to wait for your senior year before fully comprehending precession.

All things that are resonant display an equivalent phenomenon; displacement lags force by 90º, whether mechanical or electrical resonance.
 

Al_Hammer

Platinum Member
Stan, I gave it a shot. The attached diagram is my attempt at an explanation.
It shows precession as a side effect of having an object in a circular "orbit" relative to another circle which is used as a reference point to define which way is up and down. The paths will cross and up changes to down 90 degrees later from the point of maximum up velocity(where the input is aplied).
 

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ckurz7000

Senior Member
Well, here is an intuitive explanation of gyroscopic precession which I came up with for a high school physics course I once taught:

Imagine yourself tying a good sized potato to a piece of string and whirling it around your head ccw looking from above (don't try this at home, folks, where you can be seen by your neighbors). Now, at the 3 o'clock position the velocity of the potato will point straight forward. If you nudged the potatoe a bit downward at this point, you'd change the velocity at that point so that now the potato is moving straight forward as well as a bit downward. Remember, you haven't displaced the potatoe itself, only changed the direction in which it is moving! If the potato is moving forward and slightly downward at the 3 o'clock position, it will have reached its lowest point at the 12 o'clock position. So there you are! You pushed down at 3 o'clock (changing the potato's direction of flight) and the potato actually reached its lowest point at the 12 o'clock position (which is 90° later).

Here is an illustration (counting for a 1000 words):
precession.jpg
The potato is shown at the 3 o'clock position following initially the red trajectory. Then the nudge from above tilts its velocity downward (grey) and hence it now follows the grey trajectory. Note that the potato's new flight path has its lowest point at the 12 o'clock position -- which is those magic 90° later!

Hope that helps, -- Chris.
 

Al_Hammer

Platinum Member
I like it. Very concise, Chris.

I should have used a potato. Our diagrams are quite similar, but you made it very clear that the direction is changed by the nudge where I only showed that for the case of linear motion. Acceleration can be a change in direction or a change in displacement.
In the case of the rotor blade, it gets its direction changed(pilot input accelerates blade), just as the potato gets nudged and changes its direction and plane of motion.
 

Douglas Riley

Senior Member
The rotor blowback effect is different in turns with the rotor and against it. I didn't think so until I did the arithmetic; once you do, it's as obvious as why $5 is only 5% of 100 but 10% of $50. "Duh" on me.

Assume a rotor that turns CCW viewed from above. Do two turns with equal airspeeds and tunring radii; one left and one right.

When you turn right (against the rotor), both blades have less airspeed than they do in straight flight at the same airspeed. The retreating blade, however, loses MORE airspeed than the advancing blade does because the retreater is on the outside. Therefore, the difference in airspeed between the two gets larger. The teeter hinge reacts to this increased difference by allowing the rotor disk to flap black relative to the spindle. This, in turn, move the rotor's thrustline forward relative to the CG -- an unstable direction for it to move.

In a left turn, everything's reversed. The advancing blade picks up the same number of MPH of airspeed that the retreating blade LOST in the right turn. The retreating blade actually gains airspeed, too, compared to straight flight. It picks up the same number of mph that the advancing blade LOST when you turned right.

(The key to understanding this is recognizing that increases in forward airspeed actually DECREASE the retreating blade's airspeed. Putting the retreating blade on the outside of a turn -- where the forward airspeed is higher -- costs the retreating blade dearly. The retreating blade is happier on the inside of a turn, where it loses less airspeed that it would in straight flight. This is quite different from fixed-wing experience, where the "inside" wing loses lift and airspeed no matter which direction you turn.)

As a result, in a left turn, the teeter hinge faces a situation of greater "blade equality." The hinge reacts by allowing the rotor disk to fly more nearly square to the spindle. This moves the rotor thrustline aft relative to the CG -- a stable reaction.

You'll need more aft stick in a left turn that in a right one. Saying the same thing another way, you're a little more likely to lose speed and mush out of a right turn than a left one. A gyro with good airframe stability with respect to airspeed and angle of attack will compensate for the differences in turn direction.

The effect becomes less and less as bank angle steepens. It's zero at the Stan Foster bank angle: 90 deg.
 

ckurz7000

Senior Member
Astute, Vance, is an adjective. If you need a noun, you might try astuteness.

You wouldn’t say Stan is approaching lovely, but you might say he is approaching loveliness.f
Sorry guys and gals, but since English isn't my mother tongue either, I'm in dire need to clarify this (lest I can't sleep tonight).

@Chuck: I think Vance had it right: "Your vocabulary and delivery is progressing toward the technically astute." Reason being that "the technically astute" is a group of words that stand in for a noun (as evidenced by the definite article).

There are two ways to say it:

(1) He progresses toward THE TECHNICALLY ASTUTE.

Or

(2) He progresses toward TECHNICAL ASTUTENESS.

Both are correct in my understanding. And don't come down flogging me all at once, please! There's got to be an English teacher flying gyros somewhere on this forum....:help:

-- Chris.
 

Al_Hammer

Platinum Member
Sorry, not an english teacher, but "the technically astute" would be a group of people, wouldn't it? They are those that are technically astute.

One can progress towards becoming technically astute, but vocabulary and delivery are not people, so I think you would say your usage of vocabulary is progressing towards becoming more astute, but your vocabulary itself cannot be astute.

Oh, forget it, we're all likely to join Vance in his "higher level of confusion."

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The rotor blowback effect is different in turns with the rotor and against it. I didn't think so until I did the arithmetic; once you do, it's as obvious as why $5 is only 5% of 100 but 10% of $50. "Duh" on me.
Doug, are you sure??? I tried working the numbers and I get no difference in total flapping left or right.
 

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Fl90

Gold Member
In Chuck's defese, English is an illogical language with rules and structures a soap opera would be proud of. Not that Chuck B. needs me to defend him.

Back to topic.

Doug, the difference in blade speed and craft airspeed seems, to me, to be great enough not to be affected to the point of noticability. I've not had a conflict of turn performance to get my attention. I'll think on it, then fly a while...
 
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