Pylon Rock

[Harmonic_Vibe]

HV ------some questions:

 

(1) what's the nature and make-up of your slinging gear and hook-ups?

 

(2) does it happen with ALL loads, no matter what their shape or weight?

 

(3) Does it always start about the same A/S and disappear again at about the same A/S?

 

(4) While this is going on, has the wind always been from the same direction or from varied directions off the nose?

 

(5) do you have any indication of this at all, OTHER than when you have something on the hook, no matter how minor? If so, does that occur while mt/lite or with some weight internal?

 

(6) considering where you are, I'd ask you if you have dual hydraulics or single. If dual let me know....if not e-mail me. Oh and "yes Virginia" there are Bell 212's with single hydraulics.

<{POST_SNAPBACK}>

 

A (1): Steel 130' Longline. Various loads including nets and straps on dense loads like compressors and re-bar.

 

A (2): It only happens with a load in the 2500 lb range or greater... and that's all this hog will lift.

 

A (3): Yes... It starts right at the transition area between translation and hover. It will remain at the same amplitude until the A/S is around 30 kts.

 

A (4): I'm not sure about the wind direction every time. I have had wind blasting in the right side window at the same time it's blasting in the hole in the bubble... I can see one flag at the site straight out, flapping furiously while indicating a 180 degree different wind direction from a flag no more than 80 metres away that is flapping just as furiously. It is certain however, that every time it has happened I have been in strong upflow... sometimes descending but sometimes climbing.

 

A (5): There have been a few instances where I have felt just the slightest trace of the onset while flying with an internal load... but it has gone away without building.

 

A (6): Dual hydraulics.

 

Thanks very much to everybody for their input... I really appreciate it. And to answer a few other questions that guys had or things they suggested:

 

Overtalk: I loved your descriptions of pylon rock and collective bounce... I caught myself whipping my head as I read them and tried to visualize... It's definitely not collective bounce although there is a vertical component. It is very obvious that the transmission is whipping around in a circular fashion and the airframe is trying to keep up.

 

Skully: That's a great bunch of info but refresh my memory about how to introduce the perturbation... I'm sure you taught me when I did my 204 endorsement but that's a long time hence... and I'm getting up there in dog years... and no one has taught it to me since...

 

Blackmac: If I keep getting it then I will try to get to the bottom of it along the lines of what you suggested. As of now I've flown several hundred loads and set about 200 power poles, and only got this "ride" about 4 times... so I'm still in the "is it me or Huey?" stage of the investigation.

 

LTE: That reference to something falling out of the helicopter... that's ringing a bell but I can't quite remember... could you refresh my memory? I just remember doing autos with Vertical Ref and the position lights popping off the toes of the skids... two years in a row!!!

 

Matador: Many thanks my friend... I am looking very forward to seeing you again. I intend to start practicing espanola as soon as I get home... which should be about two weeks... inshallah...

 

A couple of guys have mentioned cyclic friction but I don't think that's it... but I'm willing to try. The last time it happened I anchored the cyclic to my leg and had a "perfect" approach going. VSI was showing less than 300 fpm, A/S was bouncing around 20 kts, wind was strong from about 10:00. As I was coming over the site it started to shuffle and it felt like about twenty knots of wind coming in the bubble... so I "squeezed" in left pedal to bring the nose into wind while continuing the load moving towards the spot... and the thing just started to build that whipping motion over about 3-5 seconds. The guys on the ground heard it and all looked up. I dumped the nose and went for airspeed and it disappeared at about 25-30 kts. This was my 17th load to that spot in the space of 2 hours. The only variable that had changed was the wind... but it changes around here every three minutes so that was no surprise.

 

So... I'm still wondering but I see there're a lot of things I can try. One thing seems to be coming through and it's exactly what I've been wondering... and that's the fact that you can have a "bad" mount that is workable provided you don't do certain things... so it can be a case of pilot induced oscillation that wouldn't be noticed in another ship with better mounts... or that's my take on this so far anyway.

 

Many thanks fellas... I sure appreciate it.

 

HV

 

P.S. Vertical Ref: I hope you're not wounded 'cause I left you out... Come to think of it, I've never seen you wounded... even when all those guys had that tussle with us in Fort Nellie when we were completely minding our own business... and I ended up with those star and diamond patterns all over my head from that guy's cowboy boots... and you never got a scratch! Hmmmmmmmmmmm.....

[skullcap]

you're welcome;

 

I have tried to find the exact definition on how to purturb the ole girl, I guess it just comes naturally, ha. But if I remember correctly, done either in hover or slow 20-30 kts ias, a series of 3-4 short fore and aft pulses of 1 second,, like counting. Don't need too much movement on cyclic, just enough to get the machine to wallow. Kinda like testing the dampers on head. Normal damping should stop in 4-5 oscillations.

 

take er easy or just take er

 

 

sc

[matador]

Hi H V, I thought you were already working at home, but I see... you're having fun anyway. In my post I don't know if I made myself clear but I meant what you say: you may have a new one and some old ones or vicecersa, so you end up with a problem when they are supposed to work to their limits :down:

Buen vuelo and keep in touch. I will let you know all the rumors about next summer, up to now everything is still quite messy on how it will be set up :up:

Take care

[DGP]

####...that's what it says right on the panels but as Homer Simpson would say...that's just a suggestion.....just kidding....as far as I know the panels are to be installed...so unless you have a panel that has an inspection hole.... I see nothing....I hear nothing....

[Hogie]

Hey HV, If you weren't such a ham fisted knuckle dragger it would probably help.... I think maybe being away from civilization for so long has given you a funny twitch in your right hand. You remember that place we went to in Abu Dhabi one night months ago???? a quick stop there would probably alleviate your twitch... :up: :up: See you when you get home, keep the shiny side up.

[Elvis]

I don't want to ruffle any feathers, but aren't those panels all structural, and need to be in place for ground runs and/or flight? I have only "helped" on mediums and have limited knowledge of those panels.

 

Quote from BM.

 

"HV; Take the panel off the access to the hydraulic, sit the engineer in front of it on the rear facing seat, make sure all your frictions are properly set on cyclic and collective, then find a big field and go "barn dancing" with all inputs to the left, using left pedal and left cyclic."

<{POST_SNAPBACK}>

 

 

I agree 100% Mag the panels are clearly marked as required for flights and ground runs. But I will admit to doing a first start after a 1000 hr inspection with them off but the RPM was NEVER above ground idle.

 

:shock: