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CJM91

Tsb Report: Aug 2008 B206l Crash Near Terrace

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I'll warn all newbies now as I once did to the newbies om my base. You will encounter stretching with short lines also. As a result you will use ONLY web-constructed sling lines because they don't stretch. If you encounter any other company sling lines, you SHALL cut off the pear ring and the hook at the other end......and throw what's remaining as far into the bush as you can possibly do so and you probably saved somebody's life some day by doing so. I would then, at the very earliest opportunity, arrange to take them aloft at some high altitde with a sling load on a Medium. I'd introduce 'collective bounch' and talk them through it. Once on terra firma again they now knew the meaning of the term 'McPherson Seatbelt' that I often mentioned in regards to other 'flight envelopes' and also not to complain about built-in collective-friction amounts on that Medium when their time arrived for a check-out on that type...........those frictions were there for a certain reason and that reason had now just been demonstrated to them. Better they learned that way, than the way I did. Years later, when they had that check-out on some Medium and we met somewhere, they'd often thank me because the odd one of them had already had that 'encounter', knew instantaneously what was taking place and knew how to get out of it. It usually followed that somebody, somewhere got 'a feem job' for attaching them to 'stretchy' sling gear.

 

It's long, long overdue that this extremely dangerous, 'a-hole tightener' has been allowed to be something that maybe gets desrcribed in some written fashion and is otherwise considered the sole property of the very experienced who have learned it the hard way. It's B.S. and has taken too many lives and damaged too many a/c for my personal liking. I'm also very sure that I know the lead investigator on the accident for TSB and if so, then once upon a time, many 'moons ago' when he was junior he also had an expericence........but survived. If such is the case, then he can 'smell' collective-bouch before he investigates to see if that was involved. It is something that you NEVER forget the experience of having had happen to you.

Cap:

I cannot remember the amount of times I have had a Pilot ask me to adjust the "minimum friction" on a medium to suit his preference. Sorry dude, it's not going to happen!! Minimum friction setting was put there by the manufacturer for a reason!!. Set it by the book, maintain it by the book, operate it by the book, and you will probably survive. I have carried with me for the last 30 years a small fish scale (uncalibrated, but close enough) and always check the Minimum friction and usually found it to be set much to low.

Refesh my memory Cap, what is the 'McPherson Seatbelt'

Splitpin

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Im not a bell guy and have never heard of Colective bounce. Can someone explain what it is, how its induced and how its corrected.

 

Thanks

 

I don't know a lot about it (first hand) but my understanding is that it occurs as a positive feedback loop between the pilot's hand and the collective and the airframe. That is, the airframe is oscillating up and down "around" the collective (airframe up, collective (relatively) down then vice versa). The vertical cycles quickly accelerate to the point of destruction - the blades flex into the tail boom (as in this case) or the tailboom breaks off. I've seen clips from a movie of the latter - only a few gyrations and everything comes apart.

 

It's initiated by a sudden vertical movement of the airframe while the collective/hand stays in place (vertically). This results in an unintended collective input opposite to the airframe travel which then reverses the cycle. Since the airframe - collective/hand form a positive resonant pair, things accelerate quickly.

 

I guess the stretchy longline would tend to induce bouncing in the airframe if the load hit the ground and the longline tried to contract. With lots of up-collective the line would stretch again and begin a vertical oscillation (?).

 

Although CAP explains that the phenomenon can be induced and corrected, my understanding is that it can become violent quite quickly.

 

The remedy is to dampen the free collective movement so that it will be more in phase with the vertical airframe movement, not out of phase with it. Apparently letting go of the collective will help, presumably it won't bounce up and down on it's own. Book value collective friction is the chosen safeguard.

 

I'm not certain of all my facts here - any one else is invited to correct.

 

Cheers . . . . .

 

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Collective bounce has and will occur with or without any longline and almost every accident has had to do with minimum frictions. I would like to know what brand of synthetic they were using as most operators use the old Spectra or new brand name Amsteel Blue, both of these do have elongation properties but both have almost zero elasticity. I am guessing that most folks somehow cannot differentiate the two. But elongation is what happens in your jeans when you think of Jennifer Anniston for example but the thing is not elastic is it?....same with your good synthetic line....in fact steel cable has more elasticity than these lines but yes cable does not have elongation. It for this reason that you must prestretch the line in order to minimize the elongation or it will be giving the electrical hookups grief. The fact the line stretched one foot only means the line elongated,,,,there was no time frame giving for how long it took to return to original length. If any of you have noticed an older synthetic line you will notice it is not the same diameter as new thus the elongation will be nil. I have a bunch of steel lines and will not use for their elasticity properties if it breaks,,,,been many documented accidents which were directly the result of the steel line coming up and wrapping around the helicopter....there is a well documented incident of a puma catching its synthetic line on a rock with a 4500 lb load and the line did,,,,,,nothing.

 

Please note that in no way am I pointing fingers here but just wanted to put in my opinion about synthetic lines.

 

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Splitpin -----------Not a subject to introduce humour into, but sometimes it's needed to make a point. So just for you 'ol bean.

 

MCPHERSON SEATBELT ---- Begin construction by visiting your local Canadian Tire or trailer supply outlet. Purchase various sizes of ball hitches and the reason for doing so will become very apparent as you read on. You take these balls to your a/c and cut a hole through the padded seatcover at about the dead-center location. Once securely mounted, you now do a test run where a change of sizes may become necessary. The test run should be done by the most frequent user of that seat. Begin by taking both hands and spreading both cheeks of one's derriere and very carefully and smoothly inserting the ball into the anal opening and as far into it as possible. Now you may use the already-in-place a/c seatbelt also or disregard it totally because with the ball hitch firmly established in the rectum, there will be absolutely nil chance whatsoever of being thrown from your a/c in case of an accident. Reason being, that once one understands what is about to happen milliseconds before it takes place, your anal opening will tighten-up and constrict to what is believed to be about 1,800 PSI.

 

I had certain engineers over the years who loved to take their turn flying our Medium on long ferry flights. In fact, I had one who would get his nose severely out of joint if I didn't let him. I was always careful because some of those d*mn engineers out there can fly those things better than I could........ and if they get a swelled head it could be a very long summer you see. Anyway........as they took command of the controls, very often I'd get the comment....."Hey Cap, would you prefer we land some place here and I'll transfer the McPherson belt to you becuse you might want it. In case you haven't noticed, I use it all the time, when I'm flying with you 'ol buddy. Smarta*ses.......... everyone gotta try to be a comedian. :D

 

 

CMJ91.............as I stated before, READING about this does nothing for someone who has never encountered it. It's a two part deal. First you read and learn about it and then you go out and with a very knowledgeable IP, induce same into an a/c at high enough altitude to recover from it. Without doing both, you're just basically wasting your time.

Does it happen quickly? That depends on the speed at which everything before it took place. So I say again for the two zillionth time............be smooth on the controls.....just like silk. Hot doggin' the load is just beggin' for it and as the saying goes "It's a long alley without trashcans and one of these days when your Superman reflexes are least expecting it, you'll have a need instaneously for that special seatbelt I mentioned above to Splitpin.

 

You'll know the instant it begins when you pull up on the collective and the a/c goes down, then you go down on the collective and the a/c goes up. Nothing you can do is working, EXCEPT if you been trained in same and then there's two things you can do and don't have to waste time deciding which one. IF the load is on terre firma, then it gets punched-off RIGHT NOW!!!....you stick nose down gasping for A/S and get the **** outa there. If the load isn't on the ground and you don't have that height to get the a/c AND the load out of trouble.....well I guess the client gets to activate that extra sling insurance he hopefully bought from you because that object hittin' off the sides of the rock faces of the cliff below you is his $4000 drill.

 

Those osscillations mentioned, will take place very quickly and if severe enough you might do it about 5 times and then nothing you do is going to help. Long before any M/R blade hits any tailboom, other valuable parts will be departing the a/c and any ripping you hear will probably be the transmission deck attempting to do the same. Considering what the sling hook is attached to in the '**** hole' of any Medium then the sounds coming from that area cannot be described, but are somewhat vaguely akin to the screaming emitted when the oil cooler is trying to seize-up because it's main bearing is now 'fried'.

 

One last time. You wanna drive that thing like some BMW M3 or Corvette, then it's a long alley without trashcans and you'll find that 'trashcan' sooner than you think. S-m-o-o-t-h and e-a-s-y in the controls are the operative words. If you're driving a Medium, then put exclaimation marks around those words. Mediums are great and totally reliable, specially those who were born into combat roles. They are elephants though. They don't really do anything quickly and won't get you into trouble quickly either unless you've had a complete 'brain cramp'. Once you've made that mistake though, ALWAYS remember that they weren't quick getting into it and so they won't be quick getting out of it. That's why some engineers call Mediums 'an old man's machine' because they move about at about the same speed. So ALWAYS be out in front of that a/c, some distance away, so you can read any potential problems oncoming BEFORE your a/c gets there.

 

My reference here has been almost totally pointed at Bell Mediums and their two-bladed M/R systems. I've also encountered 'collective bounce' in multi-bladed M/R ststems in the past. In that case I got different kinds of warnings as it entered into it and I therefore was able to correct any further deterioration and make that second go 'round attempt. Then again, I've found the same type of advance warnings given-out by the A/F of multi-bladed a/c as they are approaching possible 'settling with power'. To me at least, they have more of a tendency to 'talk to you' and let you feel oncoming flight problems beforehand than the two-bladed systems

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Does it happen quickly? That depends on the speed at which everything before it took place. So I say again for the two zillionth time............be smooth on the controls.....just like silk. Hot doggin' the load is just beggin' for it and as the saying goes "It's a long alley without trashcans and one of these days when your Superman reflexes are least expecting it, you'll have a need instaneously for that special seatbelt I mentioned above to Splitpin.

 

You'll know the instant it begins when you pull up on the collective and the a/c goes down, then you go down on the collective and the a/c goes up. Nothing you can do is working, EXCEPT if you been trained in same and then there's two things you can do and don't have to waste time deciding which one. IF the load is on terre firma, then it gets punched-off RIGHT NOW!!!....you stick nose down gasping for A/S and get the **** outa there. If the load isn't on the ground and you don't have that height to get the a/c AND the load out of trouble.....well I guess the client gets to activate that extra sling insurance he hopefully bought from you because that object hittin' off the sides of the rock faces of the cliff below you is his $4000 drill....

 

..... Those osscillations mentioned, will take place very quickly and if severe enough you might do it about 5 times and then nothing you do is going to help.

 

 

It is my understanding (if I heard correctly, in amongst overwhelm), that in this case, because the door was off (I was told this is standard practice for long lining), and the pilot was leaning out the door, once the bounce began, he was unable to correct quickly enough because of his position. The position of the foot pedals and also the marks inside the machine indicated that he was unable to get himself back into the machine to do so after the bounce began, in order to correct. I was also told what you (Cap) have mentioned here...

 

"Those osscillations mentioned, will take place very quickly and if severe enough you might do it about 5 times and then nothing you do is going to help."

 

I left with the impression that this (collective bounce) would potentially be a very difficult thing to correct from, given the pilots position required for long lining.

 

(very grateful for this thread)

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Hello-Bird ---------what you stated about the door being off is undoubtedly true. By the sama token, something else is also true..........an emergency release to 'pickle' the load and get rid of it toute suite (as in NOW). It's activated by a finger, a hand, a foot and activates something that releases the load or sheers-off the cable holding the load from wherever it's attached......to the belly hook or otherwise. I've worked in repel operations where certin things take place ina certain order for safety reasons. It is firmly understood by all concerned that should there be an emergency of ANY type, that I sheered the cable remotely quicker than you could bat an eyelid and that was with or without someone attached to it and possibly repelling. They heard my siren and then they were in free fall.

 

So the pilot in question had three options at least: (1) a spring-loaded toggle switch on his cyclic where one finger should have been on or very close to (2) a manually operated pull-handle between the seats to his immediate left and (3) a foot-operated manual release between both of his feet and both rudder pedals. Knowing the pilot involved and his experience on ype and in total, his reactions should have been lightning quick at releasing that load. They weren't and it cost him......and I'd love to know why. I have a funny feeling though that that will remain an educated guess at best.

 

Worked with and have known Bill Yearwood for close to 30 years.....and he does indeed know his job well. TSB is well-represented with him onboard.

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What a shame, I got my 206 endoresment on FRCL in Revelstoke by Gerry Richard.

 

I to have experienced collective bounce in Longrangers, quite the experience to say the least. It comes on so fast and violent, it cut my ears up cause my head was bouncing off of the bubble window. I was fortunate to have known and recognized the symptoms of what was happening and how to get out of it... but still left me with dirty shorts. I called my engineer and he then looked at the collective friction under the co-pilot seat and was able to remove the nut by hand that is supposed to adjust the friction... after we adjusted the friction it never happened again.

 

 

 

 

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