S76 down in Baltic Sea (Now incl NTSB Safety Recommendation)

[Geoffersincornwall]

Hydraulics

It is a dual hydraulic system - just think about it for a moment!!! What the hell do you think the other system is busy doing???

[cpt]

Geoff....I my undrestanding of the system, there is an internal bypass to allow the jammed actuator to freely move ( the bypass activation should lit the "servo" caption) now if for some reason, this bypass is inoperative (dirtyness in hyd.fluid ?) the actuactor will remain jammed and the affected control chain with it, even if the other hydraulic system is operative.
Maybe an internal leak, inducing counterpressures, also could impair the actuator normal operation, in this case I am not sure the "servo" light should always come on.
Well, it's still underinvestigation.

[Geoffersincornwall]

Cpt

Yes it's still under investigation. My understanding is that as a Cat 'A' certified helicopter a single failure should not cause the failure of another system. The two hydraulic systems are, as far as I recall, completely independent.

Just maybe the presence of waterspouts in the area at the time had something to do with it and the hydraulic problem is a red herring. Who knows? Let's wait and see.

G

[hovering]

A jammed pilot valve should allow its power piston to be moved freely with movements of it's sister hydraulic system. If the power piston itself is jammed, the other hydraulic systems power piston will also not be able to move because they are mechanically joined in a single unit, fixing the swash plate at that point.
As for the Cat A redundency idea, I would love to see how long a list of catastrophic single point failures on any Cat A helicopter could get, I bet it would scare you!

[NickLappos]

Hovering is right, I think the NTSB finding is important (a bad servo half with failed plating and debris) but it may not really explain the accident. I have no inside word at all, and speak only for myself, but the servo valves on the S76 are double spooled, so that a jam will lead to that servo half going into bypass (sort of forcing itself off line) so no hardover or stoppage is probable. Therefore, while the debris is not good, it does not seem to explain the accident.

A stick jump check is a great idea on every runup (I do that all the time) and any suspect movement, clunks etc should be examined.

The servo system is truly redundant, but lots of structure on a modern helicopter is not. Cat A regulations refer ONLY to engine power and engine/fuel system separation.

[Gomer Pylot]

I wouldn't have expected the crew to do a stick-jump test on the accident flight, because it's only required on the first start of the day, not every start, and the accident flight was well along in the day, as I understand it. I don't know how far back the FDR recorded, but it may not have gone far enough back to get to the first start of the day on a schedule like Copterline apparently ran. Doing many short runs per day means you don't do the systems checks for lots of starts if they're only for the first start of the day.

As has been pointed out, there are many single failure points on Cat A helicopters. If one doesn't understand this, then one doesn't understand Cat A at all.

[Aesir]

Gomer pylot:

The S-76 flight manual contains two preflight checks to be performed at every engine start. The first check requires pilots to check for overall smooth function of the flight controls. (Postaccident testing characterized the accident helicopter’s forward actuator to be “notchy.”) The second check requires pilots to switch off first one hydraulic system and then the other, watching for a change (referred to as “stick-jump”) in position of the flight controls. Such a jump would indicate a difference in hydraulic pressure between the systems and repair would be required before further flight. The accident helicopter’s FDR data showed that the stick-jump test had been performed in that aircraft only three times during the previous 14 engine starts.

This from the NTSB report!

It seems to me that the NTSB strongly hints that the pilots are at fault for "only" doing the test 3 times during the last 14 starts. Its important to remember that the operator may use other procedures than those specified in the manufacturers RFM so the pilots could very well have been in compliance with their operations specifications.

Another thing to remember is that this NTSB report is a "Safety recommendation" and in no way is to be considered any kind of final report on the accident! The Estonian accident investigation board AAIC are conducting the investigation and expect to publish a final report before aug. 2006.

[Gomer Pylot]

I don't have an S76 flight manual handy, but I'll look at it when I go back to work. I can't recall seeing the requirement for doing the stick-jump test on every flight, but I haven't read the flight manual's checklists that closely for a long time. We just use the checklist provided by the company, and that only requires the systems checks once per day.

I saw the part you quoted in the NTSB report, but just assumed that they had misread the manuals again, as they seem to do far too often. If Sikorsky required the checks for every start, it would seem likely that all operators would have to include them on the checklists, wouldn't you agree?

[SASless]

FAA Checklist Procedures

Does not the FAA (as set forth in FAA Inspector's Handbooks) expect an Operator to create "unique" checklist procedures as a part of FAA Part 135/121 policy and regulations? It is my recollection that Operators create their own checklists....get them blessed by the FAA and after that....use of those checklists are mandatory.

Are not only certain portions of the RFM considered to be "mandatory" compliance sections and Normal Procedures are not one of them?

Thus....Nick and a few others might correct me if I am wrong here....I can create the Normal Procedures Checklist of my own choosing....and if it is blessed by the nice friendly folk in the FAA (namely my Principle Operations Inspector (POI) ), then I am good to go.

The hiccup (if I do not incorporate all of the Manufacturers "recommended procedures" from the RFM), is after something bad happens, I am subject to criticism by the litigant's attorney.

Nick,

Is the Normal Procedures portion of a 76 RFM a required compliance section like "Limitations"....or may an Operator vary the procedures to fit their own needs?

[Aser]

Experts solve Copterline mystery

Aug 09, 2006
By TBT staff
TALLINN - Experts have concluded that a servo malfunction was, in fact, what caused the Finnish Copterline helicopter to crash a year ago in the Bay of Tallinn.

Tonu Ader, vice chairman of the commission who met with representatives of the helicopter’s manufacturer, Sikorsky, in the United States last week, told the Baltic News Service that the helicopter crashed because of a rotor servos malfunction. He added that, although the commission’s report will not be finished before this fall, their conclusion would not change.
While the manufacturer finally agreed that it was a servo malfunction that led the helicopter to crash, the commission and the manufacturer still differed on the exact cause.

“Although representatives of the helicopter’s manufacturer do not directly agree with this, the in-depth investigation into the causes of the helicopter crash leaves no room for doubt as regards to the reasons why the helicopter came down. The aircraft was brought down because of a main rotor servo malfunction, which resulted from the fact that parts of the plasma-sprayed coating that is made from a mix of copper and aluminium had broken off from the piston crown,” Ader told the Baltic News Service.

A press release by the Estonian Ministry of Economy and Communications reports that representatives from the U.S. National Transportation Safety Board said that they, too, had concluded that the accident was caused by the uncontrolled self-extending of one of the servos.
“Representatives of the Sikorsky plant had to admit that their earlier claims as regards a waterspout on the Bay of Tallinn that may have brought down the helicopter were wrong. They admitted that there was no waterspout above the Bay of Tallinn at the time when the helicopter fell, and that the servo failure proved fatal for the helicopter. At the same time, their opinion as regards the cause of the malfunction still differs from that of the investigating commission,” Ader said.

The ministry said the manufacturer’s version that a waterspout had caused the accident was also regarded as ungrounded by the National Transportation Safety Board.
Ader added that the Sikorsky plant had still not answered requests for tests that would satisfy the investigating commission.
“The Sikorsky company had conducted tests on the main rotor servo, but they hadn’t taken into account our requirements and the results of the tests didn’t meet our expectations,” Ader said.
Following Ader’s visit to the United States, the Sikorsky plant agreed to conduct additional tests in line with the investigating commission’s demands. The outcome of those tests is due to be received in October, after which the final report can be completed.

The Sikorsky S-76C+, owned by the Copterline company and operated by a Finnish crew, crashed into the Bay of Tallinn minutes after takeoff from Tallinn to Helsinki on Aug. 10, 2005. All 12 passengers and two crew members onboard were killed in the accident.

http://www.baltictimes.com/news/articles/16053/

Very uncomfortable news...

[Algy]

Sikorsky still unhappy

...because Estonians now formally in agreement with NTSB.

[Aser]

Copterline and Sikorsky disagree on cause of August 2005 crash
Operator and manufacturer discuss possible compensation issues

[Perro Rojo]

To answer the previous question; yes, the Flight Control and Servo System (Stick Jump) check, pages 2-15 and -16 of the RFM, is required every start.

It never ceases to amaze me how many helicopter pilots will take off without checking that their flight control servos are free to move, ie. not seized. A plank driver won't think of it but lots of us seem to do it regularily. Next time you are at an International airport watch when every single piece of heavy iron taxis, the fight control surfaces get a workout.

How about you guys? Do you check all your flight controls for freedom of movement every start?

[Aesir]

Copterline seeks massive damages in US court from Sikorsky

The Finnish passenger helicopter operator Copterline is seeking damages of 60 million US dollars from the helicopter manufacturer Sikorsky over a deadly crash that claimed the lives of 14 people in August 2005.

A Sikorsky S-76 helicopter with 12 passengers and two crew members plunged into the Gulf of Finland soon after leaving the Estonian capital Tallinn on August 10th, 2005.

Copterline is seeking damages of at least 60 million US dollars (EUR 45.8 million) in a US court against Sikorsky, saying that the manufacturer's negligence was the cause of the fatal crash.
Copterline is accusing Sikorsky of breach of warranty, negligence, aggravated carelessness, and neglecting its obligation to give a warning.

Copterline CEO Kari Ljungberg says that he is unable to comment on the matter at this stage in the process. No comment was forthcoming from Sikorsky during the company's Christmas vacation.
Copterline and Sikorsky have been engaged in lengthy discussions on matters of liability. The focus of the issue is one part of the stricken helicopter - the servo, which relays steering commands to the main rotor.
Copterline says that the the poor design of the part led to the destruction of the helicopter. Sikorsky has steadfastly maintained that there was nothing wrong with the servo, or any other part of the helicopter, and that the cause of the crash has to be somewhere else.
Now the company appears to be relenting somewhat: shortly before Christmas Sikorsky published an urgent maintenance instruction, calling for more frequent inspections of the servo.

The reason for the new guideline was not given, but it came very soon after the commission of inquiry into the accident had completed a series of thorough servo tests conducted in the United States.
The board is not revealing the results of the test. However, a final report on the Copterline accident is expected in April, according to the vice chairman of the commission, Tonu Ader.
Copterline had bought the servo of the doomed helicopter from the Sikorsky subsidiary, Helicopter Support Inc. (HSI) a year earlier, paying 14,500 dollars for the part. HSI is a co-defendant in the lawsuit.

Source: Helsingin Sanomat http://www.hs.fi/english/article/Cop.../1135224029647

[Aser]

Copterline S76 crash - interim official report

Copterline S76 crash - interim official report blames faulty plasma coating in control servo.
http://www.hs.fi/english/article/Loo.../1135229348440

Accident report link (Estonian language)
(English Text version to follow 2-3 weeks we are told)

http://ftp.aso.ee/pub/incoming/OH-HC...e-20070806.pdf
Big problems(money) for the servo manufacturer...

[tistisnot]

Copterline 103

http://www.turvallisuustutkinta.fi/m...taselostus.pdf

Many findings, including:

Inadequate maintenance and pre-flight practices hindered the discovery of the poorly performing main rotor forward actuator

[Copterline 103]

Copterline

MEMORANDUM
To: Federal Aviation Administration
From: Michael Evan Jaffe
Date: April 13, 2009
Re: Docket No. FAA-2006-24587; Directorate Identifier 2006-SW-05-AD; RIN 2120-AA64
This Memorandum is submitted on behalf of Copterline Oy in response to the Supplemental
Notice of Proposed Ruling Making – Reopening of Comment Period published by the Federal
Aviation Administration on February 11, 2009 concerning Sikorsky Aircraft Corporation Model
S-76A, B and C Helicopters.
Copterline Oy suffered the loss of its helicopter OH-HCI, a Sikorsky S-76C+ helicopter on
August 10, 2005. 14 persons died. The circumstances of the crash and the cause – plasma
flaking from the piston head of the pistons in the forward servo actuator – are documented in the
8 August 2008 report of the Estonian Aircraft Accident Investigation Commission. That report,
which was prepared with the active involvement of the National Transportation Safety Board,
Sikorsky Aircraft Corporation and HRTextron is available at http://www.mkm.ee/doc.php?322962.
Copterline’s concern is that the proposed rules – increasing the frequency of leakage inspection
of the servo actuator – is based on a faulty premise. The proposed rules assume that the failure
that led to the crash of OH-HCI could have been detected by a leakage test conducted within 100
to 500 hours of the catastrophic failure of the servo. In fact, that premise is flawed. The time
between the flaking of the plasma coating and leakage is quite short. It is measured in minutes,
not hours.
The Design of the Piston Head Was Altered During the Overhaul Process
The design of the piston head – as qualified by the FAA in the 1970’s – had the plasma coating,
which acted as a lubricant – located entirely within the stainless steel groove that was formed by
the edges of the piston head. Each piston head has two such grooves. As the piston head was
overhauled, the stainless steel edges were worn down such that the plasma coating was no longer
within the protective stainless steel grooves. Rather, the plasma coating lapped over and across
the head of the piston. In that condition, the plasma coating was vulnerable to cracking and
flaking as the piston moved within the cylinder.
Once the plasma coating cracked and flaked off the piston head, the carbon-teflon seals that
were stabilized by the stainless steel edges in the original design and were also stabilized by the
plasma coating in the overhauled piston, were no longer stabilized. Without the stabilization,
Pillsbury Winthrop Shaw Pittman Page 2
testing reveals that the seals will no longer function to prevent leakage across the piston head.
The instability – testing shows – occurs within a very short time after the plasma flaking. The
testing report commissioned by Copterline Oy is attached as Appendix 1.
Attached at Appendix 2 are diagrams showing the piston head as designed originally and as
altered in the overhaul process. Photographs of the pistons and piston head from the failed servo
that was onboard OH-HCI show the “as altered” condition. Photographs from the failed servo
are also attached at Appendix 3.
The Altered Design Was Never Approved or Certified by the FAA
The original design of the piston head was the subject of testing and submission for approval/
certification by the FAA in the 1970’s. This testing during the 1970s included testing arising as
a result of plasma flaking. The overhauled piston design was purchased by Copterline in 2003.
The alteration that resulted from overhaul was, to Copterline’s understanding, never submitted to
the FAA for consideration. In short, the alteration is unapproved/uncertified. To the extent that
pistons with plasma coating lapped over and across the head of the piston are in service, whether
by original design or by altered overhaul design (i.e., all servos designated with part number -110
or lower), they are not, to Copterline’s understanding, airworthy.
Immediate Removal of Servo Actuators with Unairworthy Pistons is Required
Because the deterioration of the seals that are intended to prevent leakage occurs in a very short
time after the plasma coating flakes from the piston head, testing for leakage at 500 or even 100
hour intervals will not provide any assurance that the servo actuator will function even a few
hours after the test has been performed.
Because the overhaul-altered piston heads have not been FAA approved or certified as airworthy
and because the application of the plasma coating presents an unpredictable risk of failure, it is
Copterline’s view that all unairworthy servo actuators with plasma coating lapped over and
across the head of the piston should be removed from service immediately. Until removed and
replaced, helicopters with these servo actuators should not be designated as airworthy and,
accordingly, should be grounded and not be permitted to operate.

[Kor6e]

Copterline 103, are you seriously sure that the servo actuator's altered design was never approved or certified by FAA??

If not, why FAA and Sikorsky keep these helicopters flying? Do you know who made this decision and how many helicopters are affected?

[Copterline 103]

Copterline 103, are you seriously sure that the servo actuator's altered design was never approved or certified by FAA??

If not, why FAA and Sikorsky keep these helicopters flying? Do you know who made this decision and how many helicopters are affected?

Yes, this is true. Sikorsky and its suppliers kept ongoing overhaul process which had not been approved by the FAA. They made a change in procedures (a major change) which was related to the plasma coating chipping problem (they knew). Also a wrong type of Plasma was used. During recoating process they lost the identity of the pistons serial numbers and historical data because original serial number markings was over coated with new plasma during the recoating process. Despite this, the defective pistons were used until 26.5.2010 (FAA AD. After this, the defective pistons were assigned replacement. Today, some helicopters are still installed unairworthy servos which are not overhauled according FAA approved drawings, or wrong type of plasma has been used. The plasma combination should be (85% copper and 15% aluminum as original Plasma Metco 455 but they used Metco 445 where the composition of plasma was 99 copper and 1 % aluminum). During overhaul process they deviated from FAA approved instruction to strip old plasma away by mechanical process instead of FAA approved instructions where the process was a chemical plasma stripping process. S/n 740512 helicopter’s defective piston had accumulated 24,317 hours / seven times overhauled. Each time overhaul process was using illegal mechanical stripping process. After each rework piston’s origin came smaller and smaller. According FAA approved overhaul instruction the piston origin doesn’t change at all during process due to chemical stripping process.
By each rework process they need to have more and more plasma to reach piston’s target measurement. Finally, after each overhaul plasma coating come thicker and thicker. At time of accident plasma was much thicker than planned and plasma composition was wrong (99 % copper and 1 % aluminum). These combinations together create plasma flakes which were big enough blocks C3 return ports and causing that helicopter came immediately unflyable.

FAA take a note from Copterline's Supplemental Notice of Proposed Ruling Memorandum. FAA released an AD an year later and this AD has mostly likely eliminated this illegal piston problem, but the main problem still exists. The main issue is whole Servo Actuator design not only pistons.

Type Certification requirements insist that Servo Actuator design (whole Servo Actuator system) must be a failsafe or redundant systems. This requirement is a mandatory for all FAR 29 certified helicopters. FAR 29 insist that every critical components and critical systems which may have an affect for flight safety must be designed to be failsafe or redundant system. It doesn’t matter is the root cause piston or something else a single defect should not make helicopter unflyable!

This is an airworthiness issue where is a zero tolerance.

Accident in Lagos could have some other roots than this piston problem. It is possible that this is also related to the main problem which is the servo system design and servo certification process. We are talking offshore operated transportation category helicopter and it unacceptable that helicopter is dropping down to the sea when the sun is shining.

"Kor6e" I hope that this will clarifies your thoughts and open your eyes?

[ericferret]

"FAR 29 insist that every critical components and critical systems which may have an affect for flight safety must be designed to be failsafe or redundant system."

Just about every helicopter I can think of has a single control input into the main servo, the bolt comes out and that control channel becomes inoperative. I see no redundancy in this.
This includes modern designs such as the AW139.

I would question that the S76 servo is somehow different from other manufacturers designs.

Independent pilot valves but a common ram are the norm. The Sikorsky design is different mainly because they needed a low profile servo and placed the pistons in parallel rather than in series. The layout is different but the operation is the same.

"""Today, some helicopters are still installed unairworthy servos which are not overhauled according FAA approved drawings, or wrong type of plasma has been used.""

If you have evidence of this surely you should be reporting this to the relevent Airworthiness Authority and the FAA, I am sure Sikorsky would also be interested.I am sure we would all be interested to know which operators are breaking the rules.