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Cyclic Friction On whilst flying

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Cyclic Friction On whilst flying

Old 29th Sep 2009, 01:36
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Cyclic Friction On whilst flying

Just trying to get a poll here on who & why flies with the friction on the cyclic, please?

I was taught to have some collective friction on & no cyclic friction at all. This has worked fine for me for 20 years. I am flying with a lot of ex military Pilots who love to be flying with it on, I tried it & did not like it, was too clunky & stiff to be smooth. Thanks

Last edited by Vertical Freedom; 29th Sep 2009 at 02:01.
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Old 29th Sep 2009, 02:00
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When the Bell 212/412 are fitted with Sperry Helipilots there is a prefixed friction settings for the cyclic. It helps reduce issues with feedback felt by the Helipilots and makes the aircraft fly much smoother.

Why would the same not hold for a hand held cyclic?

Put on a slight bit of friction and check for the difference in feel in the aircraft. UH-1 Hueys are very good demonstrators for this. I call it the Huey Wobble. But then....I am just one guy with an opinon.
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Old 29th Sep 2009, 03:28
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With no SAS/helipilot/whatever, I always keep a little friction on the cyclic. I don't like the sloppy feel without it. I also don't want the cyclic immediately falling over if I take my hand off it. I keep friction on both controls - not a huge amount, but enough to keep them from moving without input. It has worked for me for 40+ years, but it's certainly a subjective decision, and whatever works for you is fine with me. I think one can get used to anything, and if you fly an IFR ship you'll absolutely have to learn to live without the loose cyclic.
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Old 29th Sep 2009, 11:53
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I fly the Jet and Long Ranger, I like a little collective friction as a few Jet Rangers will wash off the pitch, but not too much so as to slow the lever being lowered inthe event of an engine failure, however I don't ever apply any cyclic friction as it takes the feel away.
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Old 29th Sep 2009, 13:16
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SASless,
You are right. Some friction takes out the "wobble". I spent a lot of time in Cobras which has a small amount of built-in non-adjustable friction. I always check the UH-1 cyclic friction at run-up. Sometimes the ambient humidity will cause the friction to change, so I always check/adjust it. It undoubtedly helps when one is engaged in precision hover work.
DH30
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Old 29th Sep 2009, 13:19
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Yep me too....a bit of friction on both and force trim on for that matter. I guess it is what you are used to but I find that a little bit of friction actually gives more of a "feel" than a sloppy stick.
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Old 29th Sep 2009, 13:20
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Collective Friction.

At very low friction, there is a real danger of either a pilot-induced vertical oscillation, wherein the pilot alone with the control system enter an oscillation that can be neutrally stable, or destructively divergent. In other cases, the pilot can interact with an airframe harmonic, and again, this oscillation can be quickly ( and scarily ) divergent in nature. The frequency of these oscillations are usually in the 3-6 hz range. The designers typically attack them either by installing a friction adjustment ( hopefully with a minimum setting in the 3-4 lb range ) or installing a friction block of some sort directly in the control system*. The design challenge is to have friction that is consistent and non-ratchety.

* And sometimes, there is enough system friction related to the particular design, to suffice.

Thanks,
John Dixson
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Old 29th Sep 2009, 13:31
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I don't ever apply any cyclic friction as it takes the feel away.
The feel? What feel? There is no "feel." No feedback at all in a 206.

I go 'round and 'round about this with pilots who don't like any cyclic friction. Nobody ever looks at their own cyclic when they fly, so I take the controls and have them remove all the friction. And no matter how hard I try...and I really do...there is no way that I can keep the cyclic from moving, even tiny amounts, and sometimes big ones! Still, even with no friction most people would consider me "pretty smooth" and most of these tiny movements don't result in any noticeable deviations or oscillations of the helicopter.

Or do they?

Here's the deal: *ANY* movement of the cyclic - even 1/8th of an inch - which is very small - any movement of the cyclic means that the swash plate is moving a proportional amount. It can be no other way; there is no slop in the controls. And if that 1/8th inch cyclic input is not necessary, then it must be countered with another 1/8th input in the other direction. And so then you, MR. PILOT, have just induced a PIO. Will it be noticeable to you or your passengers? Probably not in a sense that the airframe moves "much," because the control inputs are too quick and tiny. But the ride will be "busy." Needlessly busy.

Pilots who fly with zero cyclic friction *think* they can be as smooth as pilots who fly with "some" cyclic friction, but it is simply not true. You watch their cyclic as they fly and it is *always* making tiny little...unnecessary...movements.

Back when I was young and inexperienced, I wanted no friction on the cyclic. I was under the mistaken impression that you had to "feel" what the ship was doing, and moreover could do so! better with no friction. Over the years I learned differently. And now, like Gomer Pylot, I fly with enough cyclic friction to give me some drag...to keep the cyclic from moving if I (horrors!) take my hand off it. The upside is that in flight, the stick does not move unnecessarily. In fact, most of the time it does not move at all unless I command it. I'm more relaxed, because I'm not balancing on the beachball all the time.

I've told this story before. Ferrying a 206 out west with an uninsurable (insufficient make/model time) pilot. He was on the controls, a "good" helicopter pilot, pretty smooth, but he was constantly jiggling me around. If a pen had been mounted so that it stuck off the bottom of his cyclic grip, it would have made a terrible scribble on a piece of paper.

I took the controls. "Try this," I said, and had him put some friction on - not a lot. Once the cyclic got to the proper "trim" point, I was able to take my hands off, fold them in front of me and keep the ship flying straight and level with the PEDALS. Tiny little pedal pressures were all that were needed to correct any bank excursions. The pilot/owner flew along like that for a while, but he could not get used to it (didn't want to, is more like it). Then he took all the friction off again. While he agreed that my way did work better, he said, "I just like it better this way." I shrugged. Eh.

It did not matter to him that he could be "smoother" with some friction on the cyclic. He thought he was "smooth enough" with no friction. And it's probably true in a way. All helicopters "jiggle" in flight a little. Who really cares about tuning that stuff out? Many pilots obviously feel the same way. To each his own. But anything I can do to lessen the workload in flying these pieces of junk is okay by me.

And a little cyclic friction means that you have to work less
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Old 29th Sep 2009, 14:05
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Being a Chinook Pilot....our force trim was always "ON"....and when one hit the Trim Release the Cyclic reverted to a "Zero Friction" state and became a limp ....errr.....errrr.....noodle. Instantly one could feel the difference in the movement of the aircraft even if only very slight. The Thrust Lever (Collective Lever for you unenlightened Skid Kids) had a separate switch for the Thrust Brake....very strong force trim....very strong! As our good friend Dixson notes.....widely divergent oscillations can occur...and oft times presented us with a ride similar to that of a Bull Ride on steroids. The only way to stop the Thrust Lever from moving was to re-apply the Thrust Brake and apply a blocking of the lever using your knee.

The Bell SCAS system which started on the Cobra used a similar concept as did Sperry....a minimum friction setting for the cyclic as I recall....as on the later Bell 212 SCAS equipped aircraft.

If an aircraft has an attitude hold SAS system such as the 212/412/76/and a host of others....why not set the attitude you want...release the Force Trim Switch and let the aircraft hold the selected attitude. Did we not all learn to fly "attitudes" from our first lesson in a helicopter? Even on the HUEY, with no SAS system...I used the Force Trim system all the time. Still got the calloused Thumb all these years after retiring.

Smooth is good....burns less fuel....takes less muscle....and certainly less thinking....all good things.
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Old 29th Sep 2009, 21:12
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I like as little cyclic friction as possible, but a bit on the collective to prevent us entering auto when I change a radio frequency!
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Old 29th Sep 2009, 22:49
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I always use collective friction in the cruise, it is adjusted so that I can override it in case... but haven't tried cyclic friction in flight.
Have to give that a go one day and see if my airsickness gets better
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Old 29th Sep 2009, 23:14
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On the Bell 47 D1's that I fly, the cyclic friction is a knurled ring on the vertical portion of the stick. Unfortunately, this means that unless the friction is wound completely off, gravity and the engine vibration will cause the ring to wind itself down.
I therefore fly with small amounts of collective friction but zero cyclic.
A couple of times, having been in the cruise, I have found it an effort to make a course change because the friction has decided to make life interesting for me.
Now if the smelly stuff had interfaced with the air circulatory device and I had to take immediate and positive avoiding action, I'm sure that the friction would have been easily overcome by the adrenalin but it is now something that I make a habit of checking at regular intervals.

LM
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Old 30th Sep 2009, 01:57
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FH1100Pilot is right, there is no feel in a 206 without friction. None. The hydraulic servos are between the cyclic and the rotor, and with no friction you can't feel anything at all. It just flops around. The movement is bad enough VFR, but if you are ever unlucky enough to go into inadvertent IMC, you're going to be in real trouble, real fast. Every IFR helicopter requires some form of force trim, SAS, or something, and no helicopter I know of is certified for IFR without it. Just a little inadvertent cyclic movement, and you're in a bank or worse, very quickly, and you absolutely cannot feel anything. The only way to get any feel at all is through friction. It doesn't take a lot, but I need some. I absolutely hate the lack of feel without it. You get the same effect in a 212/412 with the force trim off and no friction - no feel at all. Some people like that, but IME they're never very smooth in that mode, and it's absolutely illegal in IMC, for good reason. Smoothness counts for a lot when you're loaded to max gross trying to take off from a platform on a 90+ degree day with no wind. Even very small cyclic movements reduce lift, and you can see that if you try a hover anywhere, prevent the collective from moving, and stir the cyclic. You'll sink, more with every movement. Start pumping the collective, and you're done, on the deck. Smooth gets off, wobbly doesn't.

All that said, it's your cockpit, so do what you like in it.
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Old 30th Sep 2009, 06:32
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In the TH-57 series (BH-206B) there was force trim, but there was also some cyclic friction applied. Most of the time pilots didn't adjust it. I assume the reason is that there's probably some happy approximate level of cyclic friction that most pilots of that machine like.
Once in a while a machine would come out of maintenance and there wouldn't be any friction on... that wouldn't last too long as a student would have a very hard time managing the machine, especially during low work.
Sometimes instructors would (while instructing hovering) place a dampening hand atop the cyclic to reduce the student's PIOs. Not friction, per se, but tends to help the student to figure out appropriate input levels.
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