View Full Version : AS 350 B & B2 Tail rotor damage help NEEDED...


Flyting
25th Jan 2007, 10:59
We have recently discovered on two of our squirrells (a B and a B2) tail rotor damage. If you look at the pics you see the pitch link wear and actual metal on metal contact with the other high-lighted marks. We've pushed and pulled on other 350 tail rotor's to try and find how and where, and the closest we've come to getting the metal to contact is about 7mm. Unfortunately, the engineers had already taken everything apart so we couldn't push the respective machines to see. Engineers say it the pilots doing it (as usual) and we say that it has to be an incorrect rigging... If anyone has seen or has any ideas about what has happened here please help. Eurocopter has no idea!!!!!!

PICS:
http://i101.photobucket.com/albums/m78/whirleybirdsa/P1222257text.jpg

http://i101.photobucket.com/albums/m78/whirleybirdsa/PB221687.jpg

Do you think this is still serviceable??? The engineers have filed the damage out and we're waiting to find out if they're going back on ??? :uhoh:



RVDT
25th Jan 2007, 12:15
More info would be appreciated...........

What are the bearings at the other end of the PCL's like? What is the condition of the bearing in the Pitch Change spider. It's a while since I have worked on a 350 but these contact marks look pretty bad. From memory the PCL's actually drive the Pitch change slider. If the inner bearings (rubber) are U/S it may allow the spider to get out of whack with the blades. What made the contact marks on the Spherical Feathering bearing? As an aside this TR looks like it's lacking a LOT of TLC for such a critical component!! Intergranular corrosion on the pitch horn visible? Tell us what the PCL bearings are like on the Spider end. :oh:

Head Turner
25th Jan 2007, 14:28
IMHO I would consider that these t/rs had picked up some FOD which has caused the damage, and yes they do need some TLC from both engineers and aircrew. If it wasn't FOD then the pilot must have known something during flight!!!

SASless
25th Jan 2007, 14:48
Was this found on preflight? How many flights took place since last maintenance action on the bits involved?

I would assume a bit of discussion and review of the maintenance log would answer those questions.

The real question I have is how long the abnormal wear was allowed to exist before being found. One would have to assume a proper daily inspection and preflight by an engineer and pilot would have discovered the wear no more than later than after the last flight one day and before the first flight the next day.

When was the last T/R rigging check done and by whom? What other repair, overhaul, component replacement take place since that time.

The corrosion seen in the photo is also a bit troublesome.

Can an engineer explain how a pilot can cause this kind of wear? Can pedal travel cause this problem if the aircraft is correctly rigged?

Was the tail rotor installed properly....and alignment checked?

I am not sure I accept the premise a pilot caused this.

Flyting
25th Jan 2007, 16:05
RVDT, I'll pass on the requests to the engineers in the morning...

The wear from the elements (lack of TLC) is normal for our heli's operating in the bush in Southern Africa. Lots of landings on dirt/sand and it takes a bit of the T out of the TLC. Most of the "corrosion" is more dirt than anything else. As for having an engineer to do an inspection after the last flight every day... that's a luxury that only happens in the "real world". The helicopters in question operate at seperate locations and it was definately not a FOD intake. Both have very similar marking with the B model starting a crack on the spar. "Just to warn others doing a preflight: the tail rotor check on the spar (pushing both blades to hear the creak of a crack) was only heard on every 15-20th time it was pushed."
Both machines are used for adventure flights and are never overloaded: B taking off with a max of 35% fuel and the B2 with 40% max. with the pedals never being pushed to the end of the full travel limits.
Flights varying from 5-15 minutes in length.

Both problems were picked up as the machines were coming up for the MPI. Riggings were done by the same company who says it has to be pilot error. I'll have to get the log cards from both to check those out and start the process of elimination.
Spoke to another engineer about it today, showed him the pics and we went push/pull again on one of his machines, and he says rigging - no other possibly way. The problem is, how can we check the rigging since both tail rotors were taken off before we were told about it?

Both tail rotors felt balanced with no unusual vibrationsand both pilots weren't aware of any unusual knocking etc. being experienced while flying.

Head Turner
25th Jan 2007, 16:33
Whirlybirds...I appreciate that having an engineer to do the after/check 'A's is a luxury BUT surely then the pilots have been taken round the helicopter with a licensed engineer and signed up to do the after flight/Check'A's. The damage and TLC issues ought to have been spotted sooner and the reason investigated. Rigging seems to be the problem, so there is need to get those doing the rigging sorted. If it turns out to be something else(?) we'd all like to know.
I have flown on the Safari Rally which requires full pedal to be used for 60-70% of the time and have never had the problems that your photos show.

SASless
25th Jan 2007, 16:33
Anyone else experience this problem?

Can anyone provide photographs of "normal" non-problem tail rotors, gearbox's for comparison with the ones in question?

Hiro Protagonist
26th Jan 2007, 00:50
Could that wear be caused by the machine being started and run up with the tail rotor gust lock/block installed? I was going to check contact points between a tail block and the rotor today but didn't get close to an astar... I've heard of someone finding out he couldn't move the pedals when he started to pull pitch :eek:

bellsux
26th Jan 2007, 04:32
I doubt if it has anything to do with rigging as if it had been ok since is was last done then why would it change?? If you look at the fwd and rear stops and they are not damaged then... The tail rotors being removed have no effect on rigging checks. The way that the tail rotor is designed it is not possible to fit it any other way. It does seem realy strange that it must have happened to both machines at the same time at different locations.

The PCL end sure looks like FOD to me or damage done during the last time it was off during maintenance but then that would have been picked up on the first pre flight?? If there is play in the spider or PCL's that would have been picked up on pre flight as well?? You say that the machines operate in dirty locations but no channce of FOD??? :confused:

I would have a guess that the other damage could be due to someone inexperienced in changing the spherical bearings ( but this would have been seen on the first pre flight out of maintenance), FOD or gust lock damage ( if you use the blocks? ) is also a possibility.

On the spar cracking it it quite easy to see what appears to be cracks but it is just the resin coating cracking. The only time I have ever seen a real crack is after a tail rotor strike except for one which was fitted new from the factory, and if there is a suspected crack the tail rotor has to come off as you can't see much of the spar when it is bolted on. The book is quite definate on the check, 5cm push and pull flex from the resting position, I hate it when I see people pushing and pulling it from stop to stop.

Sorry to say but it does seem to be a bit of a witch hunt going on where you are whirls which is never a good thing. Maybe every one there should slow down a few knots and have a look at themselves before pointing fingers.

rapman
26th Jan 2007, 06:19
Get your engineers to refit the tail rotor assy and the old pitch change links. Fit Hydraulic rig and check that the tail rotor stops under the cabin floor are contacted at full left/right pedal. Then check the dimensions for the pitch change spider/tail rotor shaft dimensions at full left/right pedal as per maintenance manual. This will prove if there is a rigging fault. A very easy check to carry out with a rigging kit and hydraulic rig.

Do a wear check on the pitch change bearings to check within serviceable limits eliminates another possibility and change the pitch change links for new ones the damage is nasty! Do a spider bearing wear check to ascertain serviceable. The damage to the rest of the tail rotor looks ok in the pictures, but check the manuals/eurocopter for advise.

As for how the damage has occured maybe it is a little early to tell until further checks have been carried out, but it is very strange that it has occured on both of your machines. The main point is that the damage has been found and that you can rectify the problem safely. Work closely with your engineers as it dos'nt help when we blame one another, we are all professionals who want to these machines operated and maintained safely

Hawkrx
26th Jan 2007, 22:24
Hey all, Just my opinion here. Don't want to step on toes, as I'm sure your engineers know what their doing.
That said, had a look at one of our B2's sitting here, (operate 14 of 'em) couple of my boys and I came to the conclusion that;
1) The scores on the pitch horns and pc link are most likely from the T/R control being slightly out of rig, allowing excess right pedal input so they contact the T/R hub, and,
2) The impact marks on the half shell lam's are most likely caused by the T/R hub spherical laminates being sheared, allowing excess blade flap under high loads w/ right pedal input.
Unfortunately have seen both problems in the past. Good thing they were caught sooner than later. As far as serviceability, the MM says impact marks lass than 5mm can be filed out, more than 5mm requires replacement. Hope this helps ;) Hawkrx

B Sousa
27th Jan 2007, 03:10
I know Fxxxall about maintenance other than if I saw that on a preflight I would be asking also. Anytime you get parts touching that shouldnt, to me, its a problem.
Im certainly going to be looking at some of ours. What bothers me is not getting an answer from Eurocopter.

SawThe Light
27th Jan 2007, 09:10
I'm also bothered by the "Eurocopter has no idea !!!!" bit. When and who did you ask, and what did you ask? I could certainly imagine a "No idea" answer if you asked how it happened. We've all looked at the piccies and also can't really imagine what happened, especially since you have said that the rigging is OK. The fact is that there's not much to go wrong with the T/R control system if the last mechanics to touch/adjust the system did what they should, and if there's nothing broken. It's simple and pretty much fool-proof, but fools can be ingenious when they try.

Flyting
27th Jan 2007, 13:09
Thanks every one for the initial help....

Please don't think that I'm on a witch hunt and putting all the blame on the engineers. I'm one of the pilots that fly both these machines, and am willing to take the blame for anything I've done to create the problem. My main objective is to find out how this has happened and to prevent it from happening in the future, and to warn others of my experiences.
Process of illimination...

No chance of the block being left in as we don't use them. The machines stay in hangars and if left out side, will only be for a while with the pilots near by in case of any storms activity or gusting winds.
No chance of FOD. For FOD to occur at the roots/hub of the tail rotor without causing any damae to the rest of the rotors, on both machines, is lottery odds. Both areas where the heli's operate from are clear of debri. The TLC it lacks is dust/sand that is picked up. Majority of landings are on grass pads or openings. Now and again a dirt lading is unavoidable
No chance of full travel impact. Like Head Turner said: "I have flown on the Safari Rally which requires full pedal to be used for 60-70% of the time and have never had the problems that your photos show." I have never used full travel in the B2 (fully loaded) or the B with limited load. Both machines work with very light loads. Even if full travel is used, there is no possible way for anything to touch anything like shown in the pics. We tried on numerous other machines.
As for the rigging, we are putting the machine back together this week end and will be commensing the initial test runs on Monday morning. Once it's all back together, we'll be able to push/pull and try and figure out how and where... According to the engineers, the rigging is a fixed setting that is done when it's all installed initially or when any majors are done on the t/r. Both machines where rigged some +-500 hrs previous to the occurance, and both were picked up by the respective pilots just prior to the last MPI...Eurocopter was sent pictures and the "Had no idea" from them just meant that they did not know how it could have happened. Obviously they can see what is damaged... I can also.... I NEED TO KNOW HOW...

The cracked spar (on the resin coating) was replaced. No-one is going to fly with that - even in Africa.... As for the other damaged parts, as per the MM they were either repaired or replaced. We still use the MM here too...

Lots of questions were asked from you guys about spiders, bearings, etc. and I have passed it onto the engineers. Monday will tell all.... I'll pass all the info on to every one once we can figure it out here.

Thanks again for the help
Let you all know soon...

MBJ
27th Jan 2007, 13:41
The V-shaped notch in the pitch change horn on your first picture looks a killer. God knows what stress that has induced in the metal. I wouldn't think blending out was a solution there!

As for the other marks how about a high altitude tail rotor stall through mishandling? I've done it on a Bell 206 at very high altitude when my foot slipped off the right peddle. Instant left peddle, lots of vibration but almost no yaw because the blades were stalled. ..might induce TR movement that you can't replicate on the ground? Just a thought.

Flyting
1st Feb 2007, 14:07
Hi again every one.

I gave the following questions and ideas that every one put forward through to the engineers on Monday. Unfortunately the machine is not ready for test flights yet, for some other reason, so I hven't been around to the airport for the checks in person.

Here are all your questions and answers in red from them.


What are the bearings at the other end of the PCL's like? Serviceable with no significant wear

What is the condition of the bearing in the Pitch Change spider? Serviceable with no significant wear

If the inner bearings (rubber) are U/S it may allow the spider to get out of whack with the blades. Not worn at all

Inter-granular corrosion on the pitch horn visible? Tell us what the PCL bearings are like on the Spider end. No corrosion

When was the last T/R rigging check done and by whom? 550hrs ago at major inspection

What other repair, overhaul, component replacement take place since that time. None

Can pedal travel cause this problem if the aircraft is correctly rigged? No

Was the tail rotor installed properly....and alignment checked?Rigging seems to be the problem, so there is need to get those doing the rigging sorted. I have flown on the Safari Rally which requires full pedal to be used for 60-70% of the time and have never had the problems that your photos show.

Tail rotor was installed correctly with the problem only showing up during the last service interval


The PCL end sure looks like FOD to me or damage done during the last time it was off during maintenance Not correct - worn from above snag

If there is play in the spider or PCL's that would have been picked up No excessive play. Well within limits

I would have a guess that the other damage could be due to someone inexperienced changing the spherical bearings Not correct

The scores on the pitch horns and pc link are most likely from the T/R control being slightly out of rig, allowing excess right pedal input so they contact the T/R hub See 8 above

The impact marks on the half shell lam's are most likely caused by the T/R hub spherical laminates being sheared, allowing excess blade flap under high loads w/ right pedal input. Bearing still serviceable, no wear marks

Unfortunately have seen both problems in the past. Good thing they were caught sooner than later. As far as serviceability, the MM says impact marks lass than 5mm can be filed out, more than 5mm requires replacement. Below 5mm

Get your engineers to refit the tail rotor assy and the old pitch change links. Fit Hydraulic rig and check that the tail rotor stops under the cabin floor are contacted at full left/right pedal. Then check the dimensions for the pitch change spider/tail rotor shaft dimensions at full left/right pedal as per maintenance manual. This will prove if there is a rigging fault. A very easy check to carry out with a rigging kit and hydraulic rig.

Do a wear check on the pitch change bearings to check within serviceable limits eliminates another possibility and change the pitch change links for new ones the damage is nasty! Do a spider bearing wear check to ascertain serviceable.

Done, carried out


Still the mystery carries on... I'll keep everyone updated on any new developments "if we find any"...

Thanks again for the help

ShyTorque
1st Feb 2007, 18:00
Is it possible that something such as a blade securing tie was left in place, or has something become temporarily been entangled in flight then departed? I cannot see how this was caused by "nothing rubbing against nothing".

Has anyone local reported losing a small boy, last seen out flying a kite?