is stick feedback important ?

[Victor Duarte]

hello
i would have your opinion about feedback in stick, is, on your opinion better have an important feedback or would you prefer no feedback, i mean, no vibe or effort on the stick.
thank you.

[Thomas]

I prefer no feedback. When you start getting vibrations through the cylic indicates the start of out of trim or balance; worn bearings.

[landman]

Of course, I have never been up in a machine without the stick connected to the rotor.
Martin Oliver

[birdy]

Not sure wot you mean by "feed back".
Stick shake,while it is fed back through the stick,is not wot I'd call feedback.It's just a sign of an out of tune rotor.
Most feed back is only in the pitch axis,as the offset dose it's thing.In some realy bad air you can feel feedback in roll from abrupt side gusts.
But it's no way near as noticable as in a FW.
I prefer a very light stick feel,mainly coz I'm lazy,and you git more feedback.I like to know me rotors can talk to me.
I'v just finished fiddling with different trim springs on my RAF and it's now very light in the stick,much easer to control.

[Chuck Irby]

Feedback to me means that you feel a wind gust, and any out of balance in the rotor, back to the stick. Feed back in the stick, in my opinion, is very important. We need to know what the rotor is doing.

[Victor Duarte]

yes chuck thats what i mean, i mean feedback as the feeling of wind gusts ot little rotor efforts, if i ask this question it is because there is a way to control th rotor in a precise way (srews) but this kind of controls eliminate the feedback, so you may miss some inportant "instinct " info.. just like "seat sensation", i think its an important element of piloting.
yes in a FW the feedback is more important than in a rotorwing and thats also what is disturbing the first time you take an helico stick, you wait for a kind of effort but you can pilot it with two fingers.
thomas i think you wanted ti say "i dont like vibrations in my stick" but would you really have NO sensation in it ?

friendly

[Chopper Reid]

If you had no feedback, then how would you know how much back pressure to apply if you hit a thermal ? I would rate feedback as extremely important.

[Victor Duarte]

thanks brian, thats kind of opinion is very important, i wonder what is the feedback in BIG gyros like cartercopter or mcculloch j2 ou a18, do they use actuators? in this case, there is quite no feedback , how do they deal with that?

another important question for specialists :
has anyone noticed a phenomena like flutter ? due to a spring or eigenmode ?
in FW this kind of phenomena can be lethal and destructive (i readed a report where a woman glider pilot had the two legs broken when the stick came into resonnance)

[Al_Hammer]

I think most would agree that feedback, in the sense of "feel" is important.
It is important that the designer of a rotorcraft insures that the stick movement and forces correlate with airspeed.
Going faster should require more forward stick. Sounds obvious, but the sense can be reversed in some designs and it makes for a dangerous aircraft.

A light stick is almost always preferred, but on the other hand, many accidents are attributed to low g pushovers or PIO/bunt in which the stick is pushed forward inappropriately. A light stick is a detriment in this instance.
Robinson has introduced hydraulics in the controls of the R44 which are designed to eliminate this problem. The stick force is controlled by the rate of movement, so that a fast forward jab is highly resisted while normal movements are not affected.

There was a fatal R22 accident in NY in August in which a student and instructor apparently saw a kite and tried to avoid it by jamming the stick forward, leading to low g and rotor seperation.
According to a witness that was laying on the beach watching a kite, the helicopter approached from the west along the shoreline 100 to 160 feet agl. The witness then saw the helicopter collide with the kite, the main rotor system separate, and about a second later, heard a loud "pop," which he described as sounding like a "balloon popping but much louder." The helicopter then started to rotate rapidly counter clockwise and impacted the water. The witness added that the kite was a red single line delta wing 2 to 3 feet in span, and had a gold tail approximately 2 feet in length. The witness also recovered the kite string minus the kite and gave it to local authorities.

[Victor Duarte]

interesting al, well sounds like the most of pilots want and need a feedback.
the idea of using an actuator as a "damper" is good..
has someone experimented a spring-centered stick ?

thanks al and others

[Doug Riley]

It is ALMOST possible to fly a stable gyro equipped with an offset gimbal head blindfolded, once you get it trimmed. The force feedback through the stick is very informative. You don't need centering springs; the "undersling" of the gimbal head pivots creates centering forces in both axes without them.

In fact, in some gyros with tall gimbal heads, there is a little TOO much centering force, leading to a "heavy" control feel. A more complex gimbal head design that moves the pivots up toward the teeter hinge would help "lighten" the stick forces. We should not try to eliminate these forces, however.

[RHerron]

The McCulloch J-2 has no feedback due to the fixed-spindle, swashplate-type control. It is more difficult to fly intuitively and "feels" more like a flight simulator.

[C. Beaty]

Real flight simulators, Ron, provide computer generated force feedback that closely mimics the aircraft being simulated. It's a stretch to call PC games flight simulators.

Having flown both stable and unstable gyros with swashplate type controls; it is my conjecture that only a Duanne Hunn could keep a stabless RAF rightside up with feathering cyclic control.

It would be no trick at all to design an automotive power steering unit with zero feedback; in fact, it would probably be cheaper but no one does for obvious reasons.

[mcbirdman]

C. I have a force feedback joystick on my computer PC. I can tell if I am on grass or pavement with the microsoft flight simulator 04. if you jab the stick it reacts back at you. The controls get "heavy" when pulling up and whatnot.

Maybe not perfect but you can feel alot more with that. Sometimes I have hitched up the pedals which are pretty much ok. With the voice command I say flaps up and it kicks them up a notch. If I say look left it looks left but with the head control I can move my head to the left and it pans left or whatever pretty well. I am getting it tuned so when I look down at the instruments I can then look back up and see the view. Pans pretty good.

Things have gone a long way forward. I also can update to current weather conditions and day, time and season by telling it to download on the internet- local weather. It is all pretty neat. Only thing really missing is a gyro that is realistic. I have a pitcarin and when you chop the throttle well it just keeps going in a nice glide. Engine on engine off... just one big sailplane.... jtm

[Victor Duarte]

The McCulloch J-2 has no feedback due to the fixed-spindle, swashplate-type control. It is more difficult to fly intuitively and "feels" more like a flight simulator.

thanks Rherron good info.. thanks also doug, and cbeaty good imputs

jtm, yes MS FS is the best, you can also play online with other players, in realistic traffic conditions, and even use 3 screens as panoramic view !

so, most of people wouldnt like a "simulator-like" stick of a fly-by-wire (without feedback)

saab and mercedes experimented a joystick driving,

[RHerron]

OK Chuck, you are correct as usual. I have never "flown" a real flight simulator.

Perhaps I should have said, "it is more like flying a radio-controlled model". My main point was that there is no feedback with the J-2.

How does a simulator "simulate" flying a Hughes 269 as far as "feel"?

[C. Beaty]

I don’t know how you’d go about simulating something when there’s nothing to simulate if the rotor is in tune, Ron. Most likely, the Army had full motion simulators at Ft. Rucker when the trainer version of the 269 was being used.

Dr. Bensen had a scheme for applying feedback to the control system of helicopters that I presume somehow sensed rotor thrust and applied the appropriate force to the cyclic system.

On several of his trips to Bensen Days, I dropped him off at Orlando Helicopters and one of the staff would bring him back; he was quite secretive about it and disclosed none of the details to me other than what I’ve mentioned above.

Sounds like a good idea but I don’t know what happened to it. Centering springs are a poor excuse for real feedback.

[mcbirdman]

C. not sure if you were talking just centering springs on the joystick/computer or not. Assuming you were, I just thought I would mention that there are NO centering springs on the joystick. When the stick is not "on" the stick can flop to the side. When it is on it has motors that provide varying amounts of resistance. Rolling on concrete it just sort of buzzes but there is friction as you pull back to lift off. On the grass you feel the vibration and when you lift the nosewheel off it smooths things a little but there are bumps in addition to the vibration. There is more to it than that but it definately isn't just a spring centering setup. The geared micromotors are pretty neat and are why they call them force feedback. If you were not talking the computer portion....... ummmmm nevermind........ take care, jtm

[Chopper Reid]

A helicopter's rotors provide all the thrust where as a gyro's rotors are merely acting as a wing so this might make a diference in the amount of feel needed. Not having flown a helicopter, I have no idea on the stick feel, but boy, i'm going to find out one of these days !! :)

[Victor Duarte]

brian, it just acts as a gyro rotor, very light, for the gyro i tried, the stick was a little shaking i found. but quite thhe same.

c beaty, the device mr bensen told you, wasnt it a kind of inertia wheel or centrifugal lever?

[C. Beaty]

Victor, I don't know whether or not you're familiar with Bensen's offset gimbel rotorhead but it makes possible the flight of poorly designed, unstable gyros that would otherwise be unflyable.

Briefly, the rotorhead pitch pivot is set forward of the rotor thrust line, generating a nosedown force in the stick that is balanced against a trim spring. An upward gust or the increased "G" load from a turn overpowers the spring and tends to pull the stick nosedown. This is stable feedback in that it tends to diminish the effect of a disturbance.

I don't know but suspect Bensen's scheme for improving helicopter stability was based on the same principle as his gyro rotorhead.

Electronically, rotor thrust could be sensed by strain gauges that drove torque motors to generate nose down stick force proportional to rotor thrust and balanced by trim springs.

I also suspect Bensen would have chosen mechanical rather than electrical means of accomplishing the same thing.

Rotor thrust in a helicopter usually is coupled to the airframe through the transmission mounting, ordinarily rubber bushings. The deflection of these bushings is proportional to rotor thrust. Perhaps Bensen intended to use transmission deflection to generate stick force.

I'm pretty sure Bensen's stability scheme did not use the inertia of geared up flywheels.

[Victor Duarte]

c beaty, thanks for this clear explanation, i almost had an overview how it works, i think its the only solution used in small gyros... its a pity that there is not a REAL teeter rotor with real cyclic controls... costy i suppose...

i didnt know about rubber bushings in a helico, or i misunderstand, have you an example please ?

i created this poll because, theres a way to control the swashplate very precisely with screws (even mechanical) but this kind of control gives no feedback, thats my concern, i also think feedback is really important..

you seem to know a lot about rotors tech , if you had nothing to do for the next months, i d like to ask you various questions :D :D

pleased to read from you

[C. Beaty]

Victor, you should try to locate Jean Fourcade, an engineer with the French Space Agency. Jean flies gyros somewhere in the Toulouse area and is very knowledgeable about them.

Jean used to post on the old Rotorcraft Forum but got pissed off at all Americans over the invasion of Iraq.

[Victor Duarte]

colateral dammages :(

i heard this name... i see where he might be, thats the bigger and first historical gyro club in france..

many thanks mr Beaty