What would we do without TC?

[Hornblower]

Recently published Service Difficulty Alert AL 2007-03 has just been delivered to my home. It states:

"Transport Canada Civil Aviation (TCCA) has been notified of a recent Twin Otter accident in the French Polynesia. While the accident remains under investigation, preliminary examination revealed that two stainless steel elevator control cables were found worn beyond acceptable limits, however they did not fail. The defect occurred in the vicinity of station 426. The cables had been recently inspected."

Good thing they pointed this out eh? Umm, ... I believe that all of the cables I have ever replaced in nearly30 years of maintaining aircraft, have been worn beyond acceptable limits, ... D'oh.
In fact I believe that is the criteria for replacement, ... hello!

..........News Flash ................

Mr Goyaniuk;
Parts are replaced when they are worn beyond acceptable limits. That is to say, unless replaced as time limited items or at scheduled overhaul intervals, all wearing parts are found in service beyond acceptable limits, at which time they are replaced… otherwise they typically stay in service.

Thank you for wasting our time and money.

[CD]

Just so you are aware, in case you missed it, this is a direct result of a safety recommendation resulting from a fatal accident where all twenty people on board the aircraft were killed.

Press Release issued on 11 October 2007

Accident off the coast of Moorea ( French Polynesia) on 9 August 2007

The BEA’s investigation into the accident that occurred last August 9 off the coast of Moorea (French Polynesia) is continuing at a sustained pace. The airplane, a DHC-6 Twin Otter operated by Air Moorea, crashed into the sea a short time after take-off bound for Papeete. The pilot and the nineteen passengers on board were killed. This is an update on the progress of the investigation.

Undersea searches made it possible to recover the Cockpit Voice Recorder (CVR) and various parts of the airplane, including the engines, a part of the tail and parts of the cockpit. The CVR was read out and analysed, though this did not provide the investigators with an explanation for the accident. The recovered airplane parts were flown to Paris to be examined in a laboratory. This work is still ongoing. On the basis of the initial findings, the BEA has recommended the inspection of the stabilizer control cables installed on some airplanes in the Twin Otter fleet worldwide. This recommendation can be accessed on the BEA website.

The investigators have also collected documentation relating to the operator, the pilot and the airplane. These documents have been studied, as have other sources of information and the testimony gathered. A new phase of work has been launched that is intended to complete the documentation and other information on the airplane.

The BEA is planning to publish an interim report within a few weeks.

SAFETY RECOMMENDATION made on 9 October 2007

On 9 August 2007, the DHC-6 registered F-OIQI crashed into the sea after take-off from the island of Moorea in French Polynesia. This public transport accident caused twenty deaths. In accordance with the French Civil Aviation Code, the BEA is conducting the investigation into this accident, with the participation of the Transportation Safety Board of Canada, the State of Manufacture of the airplane.

During the laboratory examinations that were performed in the course of the investigation, it was found that the two stabilizer control cables, made of stainless steel, showed areas that were heavily worn by chafing when passing through the cable guides located aft of station 426. This wear, which was accompanied by broken wires, had reduced the loaded section of the cable by more than 50% in some parts.

It was also found that these worn areas were difficult to identify without an indepth examination. They were thus not noticed during the initial visual examination. In addition, the cables had been inspected on at least two occasions since 17 November 2006, during programmed maintenance checks.

Consequently, the BEA recommends that Transport Canada and the European Aviation Safety Agency:

• Require operators to perform an inspection as soon as possible on stainless steel stabilizer control cables installed on DHC-6 Twin Otter airplanes, with particular attention being paid to chafing areas in contact with cable guides;
• Consider extending these inspections to carbon steel cables that may also be installed on the stabilizer control system of this airplane.

TCCA SDA AL 2007-03 DHC 6 – (TWIN OTTER) CONTROL CABLE INSPECTION
EASA Safety Information Notice 2007- 38 Revision 1 Inspections of elevator control cables on De Havilland Canada DHC-6 series Twin Otter airplanes

[ChallengerDan]

i disagree with you Hornblower.

If the inpections were so good, the accident wouldn't have happened.

TC is just saying : Pay attention guys, this could really be an issue.

Although yes, parts are typically removed beyond serviceable wear limits (which is why there is limits ) control cables shouldn't be heavily worn while they have been inspected recently (twice in the last year ) This is why the maintenance program is designed the way it is: you should address control cable wear just as it is going over the limits, no once the cable is susceptible of beeing an issue.

I agree TC can be somewhat useless somtetimes, but i think a little headsup about some issues should be welcomed.

[Hornblower]

OK fine, however the cables did not cause the accident, nor have authorities decided on the cause yet either. In my opinion, telling Twin Otter guys how to inspect the cables is much like telling your granny how to suck eggs.

We all inspect aircraft, we all replace cables from time to time, and all (or nearly all) aircraft have cables that have areas that are difficult to inspect.

In addition, many aircraft flown in remote locations are not subject to the same level of scrutiny as domestically flown aircraft, and sometimes suffer from a lack of thorough maintenance inspections.

That being said, I don’t think there is any value added in telling maintenance people they need to inspect cables thoroughly. To me, it is nothing short of condescending.

I think after over 40 years of -6 operations, if there was an issue with the inspection of the station 426 cable areas, it would have been addressed already???

And by the way Dan, I believe that 50 %, or broken strands, is the wear limit, so what is the definition of heavily worn? At least they should try and describe what they meant by that statement. In any case if the cables wear to the point where they break, then the maintenance was not done properly, or the maintenance program for inspection of the cables is deficient. I think the former may have been the case, depending on what they meant by heavily worn. From what I read there, normal beyond-limit-wear is what they have described.

I stand by my original statement; that the alert was a waste of time and money.

[ChallengerDan]

hornblower.

The BEA says
"had reduced the loaded section of the cable by more than 50% in some parts "

You're right in mentionning the 50 % wear limit BUT this 50% is on the outer wires of the cables ( according to AC43.13) not the whole cable. So that is really, really far from "50% loaded section" on a typical 7x7 or 7x19 control cable.

[ChallengerDan]

In an ideal world, we should go and consult TC website about the SDRs and stuff about the aircrafts we maintain just to see what the issues other aare dealing with.
It is not like if they put a AD on the thing... It is just information (like saying "be on the look out").
Usually, to me, information can't be bad.
That is just my humble opinion.

[CID]

Hornblower,
First you state:

We all inspect aircraft, we all replace cables from time to time, and all (or nearly all) aircraft have cables that have areas that are difficult to inspect.

In addition, many aircraft flown in remote locations are not subject to the same level of scrutiny as domestically flown aircraft, and sometimes suffer from a lack of thorough maintenance inspections.

Then immediately after that you spout:

That being said, I don’t think there is any value added in telling maintenance people they need to inspect cables thoroughly. To me, it is nothing short of condescending.

You acknowledge that there could be a deficiency but in the same breath take offense at TC doing the right thing and informing people.

And then this gem:

I think after over 40 years of -6 operations, if there was an issue with the inspection of the station 426 cable areas, it would have been addressed already???

And I suppose there are no new AMEs coming into the industry that this information may help?

Hornblower, your horn is trumpeting a false alarm. You should get it checked. You know, you shouldn't wait for it to fail before you inspect it.

[Hornblower]

Hornblower,
blah, blah, blah, ...
.

My only response to your non-sensical response is as usual ...

...Huh?

[Hornblower]

Dan, I understand what you are saying, however the safety alert didn't say that , and only thanks to CD's supplemental information do we have a hint that the cable was badly worn, and even then, we don't have a good idea of how much wear there really was. For example what is, ... "50% of the loaded section" why not just say 50 % of the cable cross section??

In addition, if it was as you suspect, 50% of the cable cross section, why wouldn't the alert say so? Simply reading the alert, I get nothing more than an indication of normal wear.

I agree that the SDR database would be a useful tool, especially when multiple SDRs could illustrate a problem that reoccurs despite adequate maintenance. However I don't believe that a one off, especially cable wear issues, is something that warrants my attention unless it is something that has not been seen before, or something that illustrates a problem that would not be seen during normal scheduled maintenance.

To send a notice like that to every AME and owner in the country seems, to me, to be a waste of time, money and energy, mine and yours!

[Spinner]

not sure where station 426 is but something about this brought a memory to mind.

was there not a failure of a control cable on a twin otter in BC a few years ago. It failed under a pulley that was difficult to inspect.

Maybe someone can find the reference to it.

[Pratt Punk]

To send a notice like that to every AME and owner in the country seems, to me, to be a waste of time, money and energy, mine and yours![/quote

Your professionalism as an AME (if that is what you are?) has definitely been brought into question with a comment like that!

[CID]

Hornblower:

Honk honk honk, bullshit bullshit bullshit, honk honk honk...

[CD]

not sure where station 426 is but something about this brought a memory to mind.

was there not a failure of a control cable on a twin otter in BC a few years ago. It failed under a pulley that was difficult to inspect.

Maybe someone can find the reference to it.

You may be thinking of this accident:

Flight Control Failure
Pacific Coastal Airlines
de Havilland DHC-6-100 Twin Otter C-FDMR
Port Hardy, British Columbia 56 nm N
17 September 1994

Two pilots and two passengers departed from a logging camp on Fish Egg Inlet, British Columbia, in the float-equipped de Havilland DHC-6-100 aircraft for a 16 nautical mile charter flight to Pruth Bay. As the aircraft was climbing through 100 feet above ground level, an elevator control cable broke. The aircraft pitched to a nose-up attitude, stalled, and descended to the surface of the water. The captain, who was seriously injured, escaped from the sinking wreckage; the first officer and the two passengers drowned. The aircraft was destroyed by impact forces and sank.

The Board determined that the down elevator control cable failed at station 376 due to corrosion, and, as a result, the pilot lost control of the aircraft. The corrosion was not detected by the maintenance personnel during the aircraft's last cable inspection.

Report Number A94P0215

Or perhaps this one, although it wasn't Canadian:

South Pacific Island Airways - SPIA
de Havilland Canada DHC-6 Twin Otter 300
Tau Airport (TAV) (American Samoa)
21 JUL 1984

While turning from base leg onto final approach the fight controls suddenly collapsed forward and the nose of the aircraft pitched up. The pilot tried to maintain control by using throttle and flap control. The Twin Otter then collided with the terminal building and a vehicle. It appeared that the elevator control cable was rusted and broken at Station 376 and the cable pulley in the area was also damaged. The cable hadn't been inspected for 725.9 hours, while inspection is required every 700 hours. The corrosion process was speeded up by the fact that the aircraft was operated in a high humidity and marine salt environment. The aircraft had also carried large amounts of salt pork and corned beef in the aft cargo compartment, directly above the corroded cable area.

ASN Accident Description

[Hornblower]

To send a notice like that to every AME and owner in the country seems, to me, to be a waste of time, money and energy, mine and yours![/quote

Your professionalism as an AME (if that is what you are?) has definitely been brought into question with a comment like that!

Yah, Pratt, I'm an AME, and you may feel free to question my professionalism if you wish, however I stand by what I said. The alert provided no useful information and after reading it (without CDs additional data) I learned nothing, and was informed of no here-to-fore unknown technical issue.

Even with CD's additional data, I see no reason to run out and check all the station 426 control cable sections. If you were maintaining a fleet of twin otters, would you imediately ground the fleet pending an inspection of that area, ... Idoubt it, nor, I venture, will Borek, Tindi, or any other -6 operator.

My point here is that they should provide useful info not the kind of non-specific, pointless blather we see here. At least they could look at a few other -6s, the sdr database, or some other kind of data, in order to determine if there is a real problem or not. Just publishing something like that without any other supporting data is at least a waste of our time and money, and at worst a lack of due diligence on the part of TC.

[Pratt Punk]

The intent of this Service Difficulty Alert, is to bring this problem to the attention of those who may be performing maintenance on this model of aircraft. Basically they are telling you to keep your eyes open when performing inspections.

Lets just hope you are not in a position of authority within an AMO. With an attitude like yours, any culture of safety would be non-existent within your organization.

Perhaps you should end your rant now, to avoid any further embarrassment.

[Hornblower]

Yes, good idea, I will from now on keep my eyes open while inspecting aircraft.

It's a good thing that both you and TC have alerted me to the dangers of inspecting aircraft with my eyes not open, ... I may not have thought of that.

From now on I will be vigilant and ensure I do no more inspections of cables with my eyes not open. And when inspecting cables, I will be sure to inspect the whole thing; not just part of it! No way I would have known that otherwise. Keep up the good work.

Hey there’s another topic for a safety alert, … “Inspection, and why “eyes open” is the best policy”. Maybe you could write it for them?? You have the right holier-than-thou attitude.

Think of all the people especially, young guys, that might not be doing that eh?

[Cat Driver]

The intent of this Service Difficulty Alert, is to bring this problem to the attention of those who may be performing maintenance on this model of aircraft. Basically they are telling you to keep your eyes open when performing inspections.

I'm with Hornblower on this one.

If you need TC's warnings to keep your eyes open when doing inspections and you are an AME then you should either tear up your license or get a job with TC.

[CD]

I'm with Hornblower on this one.

If you need TC's warnings to keep your eyes open when doing inspections and you are an AME then you should either tear up your license or get a job with TC.

I'm fairly certain that you don't really believe the regulator should ignore the recommendations of accident investigators and transportation safety boards. In this case, the BEA recommended that both TC and EASA mandate an inspection of the control cables for the Twin Otter. Neither authority have gone that far but rather chose to publish the SDA and SIN to advise of the potential problem - so apparently, they agree with Hornblower in part by expecting that AME's are indeed doing their job in accordance with published maintenance standards and a special inspection isn't necessary at this time. Had the authorities ignored the recommendation in its entirety and a subsequent accident resulting from yet another failure of a control cable had resulted, who would share the blame?

Anyway, now the safety information is out there and being discussed ... and that's a positive thing, imo.

[Cat Driver]

CD:

I'M just being a shitdisturber.....

[Firebird]

Looks to me an AD should be implemented not just general information. I,m not a Twin Otter AME but I can say if we had cable problems on a Boeing you can bet your ass Boeing and the FAA would have us changing cables or performing inspections at specific intervals.

[CID]

It's funny actually. There are so many posts on this forum that blame TC for not doing their jobs. Here we have a thread blaming TC for over-doing their jobs.

[twotter]

Looks to me an AD should be implemented not just general information. I,m not a Twin Otter AME but I can say if we had cable problems on a Boeing you can bet your ass Boeing and the FAA would have us changing cables or performing inspections at specific intervals.

Actually it is mandatory to change those cables every 12 months when operating in a corrosive enviroment. If they are tensioned correctly and the pulleys etc. are in good shape, they should have no problem lasting that long. The area described is very easy to check as you go into the tail of the aircraft, in fact those cables should have nearly smacked someone in the face. I'd say someone wasn't looking very hard, just like the YZT accident.

[CD]

Cable fracture caused Air Moorea Twin Otter crash: BEA
08/08/2008

French air accident investigators have established that a fractured elevator cable was the direct cause of last August's fatal Air Moorea de Havilland Canada Twin Otter crash in French Polynesia, confirming earlier indications.

On 9 August 2007 the Air Moorea aircraft suffered a sudden and rapid loss of control, causing it to crash into the sea just 11s later claiming the lives of all on board - the pilot and 19 passengers.

Last December investigators from France's Bureau d'Enquetes et d'Analyses (BEA) said they were focussing their attention on a fractured elevator cable which was discovered in the wreckage of the Twin Otter.

In its preliminary findings BEA said that recovery personnel had retrieved the entire pitch-down cable from the sunken wreckage. But an 8.8m (29ft) section of the pitch-up cable, between its forward and rear fracture points, was missing.

At the time BEA had only concluded the initial stage of its probe and it had not formally linked the damage to the accident.

In today's update, the BEA says: "A preliminary report, published on 6 December 2007, established that the elevator control cables showed significant worn areas.

"Ongoing studies have confirmed that the failure of the elevator pitch-up cable, at the moment when the flaps were retracted, was the direct cause of the accident.

Tests and research have made it possible to reconstruct the complex process which led to the failure of the cable."

It adds that the full report will be published before year-end.

Source: Air Transport Intelligence news

[kilpicki]

I'm going from memory here but I'd say STN 376 is the aft cabin divider under floor extreme RH where the cables are visible again after running along the RH side fuselage. 426 is where they leave the aft baggage area and run into the tail.
426 is right there and will jump out at you but 376 is more difficult, you need the elevators to be moved to see the damage, even if you got them locked in neutral you could miss stuff. If you're working alone and don't move the elevators ????

1 yr change in corrosive enviro and 5 yr otherwise.

that latest from TC was just a reminder, this is old news.