Stick Bounce

[Semler]

Had an interesting experience yesterday. Took off in a hurry and realised my seatbelt was a bit loose so instead of what I usually do by putting my knees against the stick while I use two hands to re-adjust my seat belt I let the stick go and let it float as it felt pretty calm so next thing (all within a second) I hit a big upper of a thermal and the stick starts bouncing from stop to stop (front to back, about 4 or 5 cycles within a split second) instinctively I chopped the throttle and got hold of the stick and centralised it and went back to flying normally. Certainly took me by surprise and something new to keep me on my toes.

Dunno what it would of done if I let It keep on going but im guessing it wouldn't of been pretty.

I've used 2 of my 9 lifes now

[DennisFetters]

Rotor-systems are not stable, and all of them need to be dampened. This can be done by a friction device like what most helicopters employ, where you can adjust the amount you need, or two dampers on both control-rods (or push-tubes). This will also take out stick-shake and provide for a much smoother ride..... providing you have a properly designed and dynamically balance rotor-system. Unfortunately 90% of gyroplanes don't.

The only damper most gyroplanes use is your hand. When you let go, you turned it off.

[Aussie_Paul]

Control push rods that are too long and flexible can cause the same result. Having a scissor joint midway up the tubes usually, like a RAF 2000, fixes the problem. I have lightly wound and "ocky" around the tubes and mast as a test. That is why Rosco uses those control rod flex limiters. The scissor arrangement stops any flexing of the control rods/tube, whatever we call them.

Trent, I got black knuckles from one machine I tested!!!!! Gets you attention when you are used to just letting the stick go for picking ones nose or taking pics etc.

Aussie Paul.

[Semler]

Thanks Dennis, yep i realised i was a damper, in every other case it was the side of my leg that was doing the job when i needed two hands.
I usually hold my stick very loosely, obviously the dampener doesn't need to be much.

I reckon i saw sometime back on here a damper on a mto's control system??


Hi Paul, Yeah I've got a knock off of Rosco's system with the flex limiters.


The biggest surprise was how quick it started doing it, and the rate at which it was doing it.
The burning question is if how long before it would of been before a pile of scrap?

Cheers

[Texasautogyro]

I reckon i saw sometime back on here a damper on a mto's control system??

http://youtu.be/WSLry5_6Ma0

Actually I was testing a dampner on the MTO that used a Cessna front wheel dampner after the rotor was dynamically balanced. I also found out that in mine I shim the side of the teeter bolt. Its not like most rotor heads. Anyway then I fly it with my left hand. If the shake is way worse I shim it on the other side. I then fly it with my left and the shake almost goes away. This happends from the rotor spinning counter clockwise. Then the blades not being center.

[Chopper Reid]

Originally Posted by Semler

Thanks Dennis, yep i realised i was a damper, in every other case it was the side of my leg that was doing the job when i needed two hands.
I usually hold my stick very loosely, obviously the dampener doesn't need to be much.

I reckon i saw sometime back on here a damper on a mto's control system??


Hi Paul, Yeah I've got a knock off of Rosco's system with the flex limiters.


The biggest surprise was how quick it started doing it, and the rate at which it was doing it.
The burning question is if how long before it would of been before a pile of scrap?

Cheers

The smoother the rotors, the less knock usually.

[Penguin]

That you associated the initiation of stick bounce with the thermal may indicate that there is slack in your control system. You might consider snugging things up a bit and testing the results.

[Aussie_Paul]

The experience I had was the head banged the front and rear control stops in a fraction of a second. The stick shot the 10" for and back and by the time I grabbed it I had a black knuckle. The second most frightening experience I have had in an aircraft!!!

Aussie Paul.

[Semler]

Originally Posted by Aussie_Paul

The experience I had was the head banged the front and rear control stops in a fraction of a second. The stick shot the 10" for and back and by the time I grabbed it I had a black knuckle. The second most frightening experience I have had in an aircraft!!!

Aussie Paul.

Yep it was exactly like that Paul, pure luck i got hold of the control stick, old mate flying behind me thought it was all over for me, as it pitch sharply down then up he reckons. I still can't get over how quick it all happened and at the rate it went from stop to stop, it didn't lead up into doing it, the stick just went from stationary to full on.

My rotors are smooth as, Larkins lovely as, no slop in my control system, recently replaced my bushes for the control systems so know that part is fine.

I'm thinking the trim spring probably didn't help the situation as it would of help the bounce once started.

If i knew how far i could get way with it i would try to get it to do it again and video it.

Anyways I did what i was told to do if things go to sh1t. Pull throttle and central stick, the machine is fine and has done a few more flights since so all is good.

[Resasi]

Interesting to hear the experience you had Trent along with the others, and that these ended well.

I know that there are stable gyros out there, and seen videos of impressive acts of faith.

Somehow have not to date felt experienced enought to try any of them.