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3top
10th Jul 2008, 20:03
Hi all,

everyone with experience on AS350:

I am in a discussion (friendly one .....) with my boss and the chief mechanic, regarding the best time to replace the TR-pitchlinks.

My boss obviously would like to run them out to the limits allowed according to the maintenance and repair manual for obvious reasons.

I would like them to change them whenever I start feeling vibrations!

- I am spending about 35% of the time in OGE hover with varying loads of up to 1200 kg on a 100 ' or 150 ' line. The work requires extensive hovering time - repositioning core-drill rigs, normally distances are less than 1/2 nm.
So there is a lot of business at the TR! (compared to regular A to B flying....).
When I complain about vibrations (high frequency) on the tail it gets checked according to manuals and so far it always came back "within limits".

On my type transition (factory), I was adviced, that the TR pitchlinks should never have any play - notwithstanding what the maintenance manual says!
Same advice came from the CFI and the Factory technicians.....
Reasons: Accelerated wear of TR-gearbox bearings, gearbox, TR-shaft bearings, tailboom (stress cracks)...
Especially in the job arena the helo was going into!

Again, considering my work area, I'd rather not ever encounter trouble with anything on the tail!
Escape possibilities are rather slim while on a rig-move...:sad:

Question to all:

Do you have any experiences related to this item?
Pilots, mechanics, ....

Evidence of accelerated wear, excessive cost for related wear and damage, accidents directly or indirectly related to the pitchlinks with "play"...

I am on it to read all 350 and pitchlink threads search will find, but it is some task!! The main 350 thread alone is 30 pages!

References to other publications, forums, whatever you can point me to!

So if anyone could shed some light on this, please post or send me a PM or an email to [email protected]


Thanks all!

3top :cool:

VeeAny
10th Jul 2008, 20:38
3top

Check you emails, may help.

GS

Oldlae
10th Jul 2008, 21:55
Whilst the MM limits of wear in the links must be respected, your operational use seems to have made the links wear out more quickly. I always used to allow any wear, not on the 350, until the pilot reported vibration at which point they must be replaced, who is certifying the aircraft? If your boss is smart the links should be retained and the excessive wear taken up with the manufacturer, they may be eligible for a refund if they are within a warranty period. As they are not normally a serialised item, careful recording of their replacement should help your case.

Scissorlink
10th Jul 2008, 22:02
I have always been told no movement at all as well

If all else fails
11th Jul 2008, 01:11
Always understood there should be no play in the pitch change links. Had a B2 spherical bearing 'flog out' to the point where daylight was clear between the link and the housing in an alarmingly short space of time (less than 2 hours flight). Pedal vibration was first indication and progressively increased throughout the sortie. Options to land short were terrain limited and a little complex due patient requirements.

spinwing
11th Jul 2008, 01:42
Mmmmmm .....

Might I suggest ... that the your T/R assy requires much more stringent balancing... (if that is the case) .... then as "OldLae" suggests accurately document s/n, Time On Vs Time Off and wear ... digital photos as well (?) and then you have something accurate to put to the "Boss" and he in turn has something to throw back at the manufacturer.

If the T/R balance is not spot on then you will accelerate the pitch link "flogging" wear by a rediculous amount.

:E

3top
11th Jul 2008, 02:04
Folks,

thanx for the quick replies!

spinwing: the TR is supposed to get balanced on every 100 inspection(internal company agreement...), but I am not sure this is really happening.
We use the ACES system - very easy to use and quick.

If I remember right, pitchlink axial play could have 0.5 mm, radial play 0.2 mm acc. to MM.

Scissorlink and If all else....: Thanx for the confirmation!

Oldlae: I have no idea what the lifetime of a good set of links, well balanced is in a normal flight environment.
We got the B3s specifically for longline/aerial cranework. At least 1/3 of my time on the type is moving things with a line....
I do know that the TR is working a lot and hard!!

Next 100 inspection we supposedly will do some testing:

Balancing record before any work, then balance and fly the ship.
Then new links and the whole thing again - to see if there is a difference.

Just a little hard to get the same conditions at the shop like out here in the field....


Keep it coming guys! .....girls too! :)

3top
:cool:

aspinwing
11th Jul 2008, 02:23
In your normal -- friendly-- manner; put this to the boss.

1. What is the cost to replace the T/R early, say at 70% of rotable time.

2. What would be the cost if it quickly worsens to the stage where I have to drop the drill and go into the trees or roll it up?:eek:

I suspect that 2. - insurance deductable at least - will exceed 1.

Leave that idea to simmer for a bit.

3top
11th Jul 2008, 02:51
Aspinwing:

Seems like common sense, doesn't it!

Guess what:

Common sense isn't!!

I do understand their view from a short term (view...) perspective:
We have a prescribed max tolerance and if it works we go all the way there!
These things are expensive!! (...can't make them "see" your point 2....)
And best of all - none of them bites the dust when the darn things go south!!


It's pretty obvious that we (pilots on this thread...) all agree, that saving peanuts is not worth the increased risk.
What I would like to get my hands on is examples like "If all else fails"s....
or some hard data that shows later, more expensive damage/downtime to other parts of the tail or airframe...

Thanx Aspinwing!

3top:cool:

bellsux
11th Jul 2008, 08:26
If you can ask your AME or A&P if they have the part number for the bearing in the TR PCL I would love to know it, I did see them being replaced in the early 90's but now the number is not listed in the IPC. Very easy task just pressed out and roll staked in the new item.

or

If anyone knows who does exchange overhaul on the TR PCLs..

please PM me thanks.

Bushrat
11th Jul 2008, 10:19
As for replacing the pitch link bearing...that procedure was removed from the maintenance manuals a long time ago ...large parts supliers...(vector) can do exchange on your old links...If there is not excessive wear on t/r pitch change link and you are getting vibe....look closely at the laminated hinge bearings(teetering bearings) on th hub...slight wear in these is ussually the first cause of vibe in t/r...often pilots will not realize it is starting but if longlining will get that "not into wind" feeling more often..which will lead to fighting the pedals and accelerated wear on everything...also on B3 keep an eye on the tgb lever where it attaches to gearbox...can spin bushes out of the lever if not installed properly.

piggybank
11th Jul 2008, 11:34
In my experience maintaining Bell 212 and 206 desert and jungle the time between within in limit and showing daylight can be very short, a few flying hours. I have seen this on three occasions. I agree completely with oldlae (ex PNG?) but the fact is no one is moving in a rush to sort it out. This problem has been round for years, certainly since the seventies.

Oldlae
11th Jul 2008, 21:16
Piggybank,
Not PNG, more Duri 71-72.

helifixer
12th Jul 2008, 05:54
Sounds to me like you need to toughen up. If the bearings are within th MM limits, they are serviceable. End of arguement, get in the aircraft and fly it or find a different career path.

TukTuk BoomBoom
12th Jul 2008, 10:30
Yeah i agree.
Ive worked on Astars for 15 years and PCLs are one of the big ways to save money on Maintenance.
Run them to the limit. Who cares if they click when you flex the tail rotor.
If you swap them out every time someone says theres a tiny bit of play you be changing them at least 3 times as often as need.
Ive never heard of PCLs causing vibrations unless they are falling out.
Id be more interested in the teetering bearing, make sure if they have been changed they are aligned properly and in service that they get changed after they shear.

But maintenance is not an exact science so do whatever your Chief recommends..

spinwing
12th Jul 2008, 10:30
helifixer ....

Just because they are deemed to be "servicable" does not necessarily mean they are going to do the job satisfactorily .....

Perhaps you should listen to pilots a bit more lest you end up having to find a different career path!

Methinks .... your attitude needs adjusting!

:E

TukTuk BoomBoom
12th Jul 2008, 14:43
no Spinwing, i think that is the actual definition of serviceable

When it comes to maintenance issues you dont go by individual pilot recomendations. HeliFixer is dead on

Within limits IS serviceable, thats why they have limits

You explain it to the guy who pays the bills why you changed it early

Its like saying, "yeah sure you can pull 100% torque but im not comfortable with it.."


Did you mention career change?

The Sultan
12th Jul 2008, 15:25
Spinwing and all

Tail rotor balancing has not a damn thing to do with pitch link where. Your equating fixed system vibration which can be felt at fairly low force levels with what the pitch link see which is a steady force because it it rotating. Now a massive out of track of the tail rotor may cause an issue, but you would see that again as fixed system problems not (cracks etc..)

Most likely the mission is causing high flapping(lots of pitch link bearing motion), which can not be changed, in a hostile (dusty) environment and that is causing the problem. Once bearings wear through the Teflon the bearing goes to daylight relatively quickly.

The Sultan

3top
12th Jul 2008, 16:10
Fixer:

Actually I am trying to soften up!
I believe I was quite a bit too tough - I did a lot of things in my career, because I thought I am really tough - got really close calls too - generally what you call "experience".
I am just plain lucky to always have gotten away with it and still be around to tell about.

I am not afraid of the TR PLs. The recommendation did not come from just "any individual pilot", but from the factory instructor + the factory tech personnel.

The whole discussion is just about that:
Money versus safety versus operating terrain versus type of operation.

Looking at the PLs, it is very unlikely that these ever would let go.
The concern is the TR gearbox, bearings and controls.

Donīt want to assume anything, but your talk doesn't sound like you have a lot of sling time in your book...
Looking at your age - I was talking likewise, back then - hope you make it too where I am now.....


Though talk is just smoke....

3top:cool:

3top
12th Jul 2008, 16:26
Tuktuk,

I see your point and certainly understand it.
What you seem not to consider is possible more expensive damage to anything in the tail down the road.
Just because there is certain limits allowed on a part, does not mean it is neccessarily recommended to run it to the limit.

This will to a good part depend on the environment you run in too.

Just as a pointer:

We are required by EC to note down all landings and external loadmoves.
The intense use we give our machines has them concerned that certain parts might not make it to published TBO hours! To many loadcycles!
It is not uncommon to do 40-50 landings here in 4-5 hours flying time.
Most of our sling time is picking up and letting down or holding on the spot, hardly any distance flying at all. So in an hour of slinging we can get up to 20 loadmoves.

Though talk is cheap.
PLs are cheap too in comparrison to possible more damage down the road.

However I don't claim to know it all - by all means I might be completely off and the vibrations I can feel on/off are normal or come from a different source, as some mentioned here already.

I am glad my boss actually tries to go the bottom of this and at the next 100 hrs inspection we will do some trials (which no doubt will cost money...)

The whole reason why I started this thread is to find out what experience other professional pilots have and what they have to say about.

Also still hoping that some mechanics chime in too...


3top:cool:

spinwing
12th Jul 2008, 23:25
3Top ...

You make some very good points .... I agree with you entirely.

As I indicated in my post ....

" Just because they are deemed to be "servicable" does not necessarily mean they are going to do the job satisfactorily" .....

...Perhaps I should have added the words "continue to" in there somewhere!

And when there is concern about anything to do with your machine you are duty bound to investigate it and the possibilities whether you be a "sissy" pilot or a "hardened" Engineer/mechanic. You just MIGHT end up SAVING your boss a fortune by being a bit more pro-active.

Fixer/ TukTuk ...

I understand very well what servicable means ... having been a Helicopter Licenced Aircraft Maintenance Engineer since (if his profile is accurate) before Fixer was conceived. I do both jobs... I understand both points of view.

:E

TukTuk BoomBoom
13th Jul 2008, 00:49
Roger that

Im sure youve had at least as many discussions as ive had with prima donna pilots who think they know whats serviceable better than the MM.
Is always good to be able to get out the book and point to the limits.
Those bloody TR PCLs are one of the most common battles ive had
"oh its clicking!"
:ugh:

helofixer
13th Jul 2008, 00:53
I talked about this topic with another mechanic I work with. He used to work for a major contractor here in the states that did maintenance for a US government agency. He told me that as soon as the PCL bearings had noticeable or measureable wear within limits, they had a maintenance policy that instituted a recurring 30 hour measurement check. That way they knew which aircraft had pcl's wearing, and got a mechanic to measure it every 30 hours to determine if they were serviceable. Kept the aircraft flying, the pilots got some peace of mind, and they did not spend a ton of money on links that were a bit worn, but serviceable.