air safety

May 2, 2016

Cobham jet caught fire after company failed to properly repair an engine

Which is worse? A jet on fire over a city because of an unapproved engine repair, or safety regulator CASA saying it won't act against the airline?

Ben Sandilands — Editor of Plane Talking

Ben Sandilands

Editor of Plane Talking

A Cobham Avro 146 RJ100 not on fire
A Cobham Avro 146 RJ100 not on fire

On 29 April 2014 a Cobham Aviation Avro 146 RJ100 caught fire over Perth with 93 people on board at the start of a charter flight to Barrow Island.

Cobham’s crew of six handled the emergency perfectly, and the small high winged four engined jet returned to Perth Airport without injury to any person.

But the release of the final report by the ATSB investigation of the incident mightn’t be said to have left Cobham’s reputation untouched.

An engine caught fire and was being fed by fuel under pressure because Cobham for whatever reasons failed to properly repair a fault prior to take off. Had the crew not acted promptly and correctly to the crisis, or the jet not been able to set down on an immediately available airport on its long mostly over water flight, the outcome could have been tragic.

Cobham's fiery engine repair mistake as seen from Perth
Cobham’s fiery engine repair mistake seen from Perth

The story about this flight is really two stories.

There is the ATSB report, which is thorough but accessible to lay readers-meaning those of us who could end up being killed in such serious incidents-and there is the diligent manner in which the safety regulator CASA has acted in relation to Cobham, no doubt in close consultation with the Minister responsible for air safety.

(Except that apparently it didn’t because it can’t see any reason why an Australian registered airliner trailing flames over a capital city requires it to do anything.)

This is the core of the ATSB report which can be downloaded in full here with added emphasis.

The Honeywell International Inc (Honeywell) LF507-1F (LF507) engine has four combustion liner locating pin welded bosses (welded boss) in the combustor turbine module (CTM) combustor housing (housing). The ATSB found that the welded boss located at the 2 o’clock position had cracked and fractured adjacent to the weld as a result of fatigue. The boss separated from the housing, allowing high-pressure combusting fuel to escape radially through the CTM housing, burning through the engine cowling.

The ATSB also found that localised grinding of the inner and outer surfaces of the CTM housing, adjacent to the welded boss, had reduced its wall thickness from 0.050 to 0.035 inches. The reduced wall thickness increased local stresses and hence the likelihood of crack formation. The crack accelerated at an unpredictable rate until penetrating the full thickness of the housing. It is likely that the grinding was associated with a weld repair conducted during a CTM heavy maintenance visit. The grinding repair was not an acceptable repair to Honeywell for returning the component to the original design strength.

Finally, the ATSB found that the normal scheduled visual inspection of the housing, which was designed to find cracks before they developed into a fracture, was ineffective in this case. This was because the reduced wall thickness invalidated the original crack growth rate predictions.

The ATSB’s safety message is that:

This occurrence highlights the importance of repairing aircraft components in accordance with the manufacturer’s specifications and ensuring that the repair meets the design intent of the manufacturer.

Enter, CASA, supposedly the guardians of public safety in the skies, in conjunction with fully informed and proactive ministers.

When a spokesperson for CASA was asked what action the safety regulator was taking in relation to this incident the reply was:

The Australian system does not have prosecutions for organisations.  We work under a certificate based system.  We also have system based on just culture to ensure open reports such as are made to the ATSB and mistakes rectified.

This statement is completely contrary to statements made by CASA about the legal responsibility for safety outcomes by its previous directors of air safety John McCormick. He even sent letters to the senior managements of the major Australian carriers reminding them that they and their boards were personally liable for the safety outcomes of their operations, regardless of where or by whom maintenance on their aircraft was carried out.

A ‘Just Culture’, in this most recent CASA statement, seems to be shorthand for ‘sod off.’ It is supposed to be about protecting confidences in safety reporting, rather than turning blind eyes on dangerous practices by airlines CASA is supposed to audit for compliance with the rules or procedures that keep passengers safe.

The safety outcome of concern in this Cobham incident is the catching fire of an airliner with 93 people on board over a capital city because of incorrect repair procedures.

What does CASA want before it gets it’s head around this incident. Burned bodies strewn over Perth, and casualties among those on the ground below it?

The safety culture in the US is one of naming, fining and shaming airlines for breaking rules and procedures. Think of it as being what Australia does, or intends to do, for the road haulage and construction industries. But when it comes to airlines, transgressions are buried under fairly floss, making them like banks or financial planners perhaps.

The new Minister Darren Chester is meeting the grass roots aviation industry in Tamworth this Friday, one hopes before the government goes into caretaker mode on the calling of a general election.

It is an important meeting. It is also important for the Minister to note that his predecessors were treated with arrogant contempt by his department in relation to aviation matters and public safety, and that taking visible control of his portfolio and remembering he is a representative of the people, not unaccountable bureaucrats or corporate entities, is a prerequisite for being held in respect.

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59 thoughts on “Cobham jet caught fire after company failed to properly repair an engine

  1. Fred

    The full report reveals some further details, which show that it is difficult, if not impossible, to determine who should legitimately cop the blame for this incident. The fire occurred as a result of a failed weld repair to the combustor housing. The report states that metallurgical analysis showed the housing had been weld-repaired on three separate occasions, however:

    “The only recorded weld-repair to the CTM housing was in 2005 although, as the CTM housing was an exchanged unit, its history could not be established. Therefore, either the CTM housing was repaired at or prior to 2005, or the housing was repaired after 2005 and the repair was not recorded. From the evidence available, the ATSB could not determine which was the case.”

    According to the report, the aircraft and its engines were introduced into Australian service in 2012. However, information on the Internet shows the aircraft had been stored at Adelaide since 2010. Before that, it had been registered to several overseas operators, including Turkish Airlines, Trident Jet Leasing in the UK, and Riau Airlines in Indonesia.

    Whilst airlines are “liable for the safety outcomes of their operations, regardless of where or by whom maintenance on their aircraft was carried out”, is it fair to blame Cobham, given that the history of the failed CTM housing could not be established? Does Cobham have a case to answer and would action by CASA against Cobham actually achieve a better safety outcome, given that the dodgy maintenance was probably performed several years before Cobham began operating the aircraft?

  2. Ben Sandilands

    In Australian courts ignorance of any law is unacceptable. In the case of an airline, failure to establish the provenance of parts or procedures is extremely serious. Knowing this is written into the AOCs here. There is no hiding place, other than a lack of diligence or focus by the safety regulator.
    If Cobham is going to put you or me in one of their jets, it is explicit in their operator certificate that they know and perform the correct procedures acceptable in this case to Honeywell. They failed to do that.
    I think it is clear in this case that there is no defensible link between the antecedents of a part or prior procedure and the absolute responsibility of the operator for the safety outcome.

  3. comet

    Cobham… Isn’t that the same airline that had one of its aircraft enter a stall situation over Western Australia (Kalgoorlie from memory) with the control stick shuddering and shaking in a near disaster?

  4. Fred

    I agree up to a point, but the ATSB’s report shows there were three separate weld-repairs, only one of which was documented. That repair was performed some five years before Cobham owned the aircraft. We don’t know when the other repairs were done, or by whom.

    Under Australian law (CAO 100.5), maintenance records for aircraft components only need to be retained until the component is next overhauled. The records show that the combustor housing was fitted to the engine in 2005 and that the housing was inspected and repaired in accordance with the engine manual at that time. Cobham may well have done the necessary due diligence when it purchased the aircraft, but how were they to know the component’s provenance if there was no requirement for maintenance records prior to 2005?

    1. Ben Sandilands

      You’ve read the full report but somehow missed the safety message. Whatever the antecedents of a part, Cobham had to ensure the engine was repaired in accordance with the manufacturers procedures.

      They didn’t. They are responsible for any consequences.

      1. Fred

        Thanks for the condescending reply, but that still doesn’t answer the question. In the real world, how was Cobham supposed to know that a dodgy repair had been performed on the engine? How could they possibly “ensure the engine was repaired in accordance with the manufacturer’s procedures” if they had no way of knowing about the defect?

        1. caf

          If they don’t think they can trust the maintenance history of the aircraft, they shouldn’t be buying the bloody thing!

          1. Fred

            Hindsight is a wonderful thing, is it not?

      2. Dan Dair

        Does the ATSB report specifically say that they’ve trawled through all the previous owners documentation for this airframe & this specific engine.?

        How could Cobham’s engineers weld-repair a combustion chamber wall without being fully aware of what the tolerances are for that repair.?
        Is it even appropriate to weld that area of the combustion chamber in that fashion.? Is there perhaps a repair plate which would include the ‘welded boss’ so that the original weld is not being ‘welded-over’.
        (My limited experience of general (as opposed to aviation-grade) welding, is that the action of welding can make the surrounding area brittle & liable to cracking)

        1. Fred


          Yes, the aircraft’s past maintenance records were examined, but the records for the combustor housing only went back as far as 2005, when the housing was installed in the engine.

          There is no suggestion that Cobham’s engineers were responsible for the errant weld-repair. If there was, then I’d imagine CASA would have plenty of grounds to pursue Cobham. According to the report, the last time that heavy maintenance took place was in 2009, before Cobham owned the aircraft. The investigators could not determine the timing of the dodgy repair from the maintenance records. There were three repairs, two of which only came to light through metallurgical analysis following the incident. One repair was documented properly and was performed in 2005, but the other two were undocumented and could have been done some time before or after 2005.

          According to the report, weld-repairs are approved by the engine manufacturer as a technique for repairing cracks in the combustor housing. The problem, however, wasn’t the weld; it was the grinding that was done afterwards that significantly reduced the thickness of the housing.

  5. Dan Dair

    I had this same conversation on the Virgin ATR ‘tail’ incident pages.

    It is apparent that, under Australian law, the airline and not the maintenance company, is primarily responsible for the condition of their aircraft.
    That is not the way I had presumed it to be.
    It remains the case that the maintenance company would be responsible in law for their failures, but the airline ultimately ‘holds the baby’.

    1. Fred

      Absolutely Dan, and I have no problem with that. But realistically, what would CASA achieve in terms of improving safety if it chose to pursue Cobham over a dodgy repair the company didn’t perform and didn’t know about? It gets back to that ‘just culture’ thing. Ben said that a just culture is “supposed to be about protecting confidences in safety reporting”, but that’s only a small part of the story. A just culture was defined by James Reason as “an atmosphere of trust in which people are encouraged (even rewarded) for providing essential safety-related information, but in which they are also clear about where the line must be drawn between acceptable and unacceptable behaviour”. A just culture recognises that human beings are fallible and sometimes make mistakes. It encourages the open and honest reporting of such mistakes in order to improve the safety system, without fear of retribution. Nevertheless, it does not tolerate wilful misconduct.

      In Cobham’s case, it seems highly likely that this incident occurred through no fault of its own. If CASA pursued Cobham, it would send a very negative message to the industry. Nothing would be achieved in terms of improving safety outcomes and it would probably mean that other companies and individuals would think twice before reporting safety issues. Would that benefit the travelling public? I think not.

    2. ghostwhowalksnz

      Since there was no ‘disaster’ there were no liability issues to consider. But that would only need to be considered when relatives came looking for compensation, thats when the airline would be ‘ultimately responsible’ and couldnt fob them off to ‘Fix whileuwait’ engine repairs. It would be up to the airline to seek its redress through the courts and its contract with the repairer if they wanted to.

  6. Mark Skinner

    Fred, the question should rather be whether or not Cobham could have seen the repair under the manufacturer’s maintenance and inspection schedules.

    If it could have seen/detected the repairs, then it is totally responsible, not only in law, but also morally. Because if it saw the repairs, but could not establish, for the reasons you pointed out, whether they were done correctly, then it should have had those repairs redone so that they COULD establish that they were done correctly.

    The only out that Cobham might have morally is if those repairs were not detectable before the incident.

    1. Fred

      Mark, I agree. Unfortunately the report is not clear on that point. It only states that three separate weld-repairs were identified when the combustor housing was subjected to a detailed metallurgical examination. One of those weld-repairs was documented and was certified as being repaired in accordance with the engine manual. The others weren’t documented. Given the engineers would have had no way of knowing about the two undocumented repairs, it seems likely they would have associated any evidence of a previous ‘repair’ with the one that was documented.

      Nevertheless, it wasn’t the weld-repairs that caused the problem; it was the grinding that was done afterwards. That grinding reduced the thickness of the combustor housing, causing an area of increased local stress and subsequent internal cracking. The report does not make it clear if the grinding (not allowed), as opposed to blending (allowed), was readily apparent during visual inspection.

      1. Mark Skinner


        I guess the point is that the things you mentioned should have been in the official report. That is, yes those repairs should have been detected by Cobham, or not, and if not, whether anything could be done to make it so they can be covered in future. Hindsight is one thing, but not learning nor improving nor making specific recommendations is the issue.

        There’s a difference between a report that says: “Cobham could/could not have detected the problem, and here’s the official recommendation for prevention of a recurrence.”, and a report that is only description of the problem and little more.

        1. Fred

          I agree, although I think the ATSB has to tread a fine line, because its role isn’t to “apportion blame or determine liability”. The blurb at the back of its reports states: “At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner”. In some cases, however, the ATSB goes too far out of its way to avoid blaming anyone, to the point where its findings and recommendations are of little value.

          In this case, the engine manufacturer (Honeywell) was proactive during the investigation and amended its maintenance manual to ban weld-repairs to the welded boss of a combustor housing. The entire housing must now be replaced if a crack is identified in the welded boss. A Service Bulletin was also issued that required a detailed visual inspection or non-destructive dye-penetrant inspection of all combustor housings.

  7. ggm

    I thought at acquisition, an airline doing public flight got the engines and airframe fluoroscoped and x-rayed.

    Cobham might have recourse to whoever they use to do survey?

  8. comet

    Cobham is buying aircraft from Indonesia.

    Indonesia is the most corrupt aviation jurisdiction on the planet. Aviation officials there are famous for their bribe taking. It is notorious.

    So how can any maintenance history from Indonesia be trusted? Obviously Cobham trusts it and hopes for the best.

    Defence: “Your honour, how could we possibly have known there was something wrong with the aircraft before it crashed?”

    1. Dan Dair

      “Defence: “Your honour, how could we possibly have known there was something wrong with the aircraft before it crashed?””

      His Honour: “Because it was purchased cheaply from Indonesia.?”

      1. comet

        To sum up, Cobham bought the aircraft from an untrustworthy source, where it’s airworthiness could not be verified, and unauthorised maintenance took place with no records kept.

        Cobham bought this aircraft in that condition for one reason… because it was cheap.

        Qantas uses Cobham’s services for the same reason.

        You get what you pay for, hence the stick shaking incidents in a Qantaslink 717 over Kalgoorlie, operated by Cobham.

        Alan Joyce knows a bargain when he sees one.

        1. Dan Dair

          Should a Qantaslink aircraft befall a serious mishap,
          bearing the Qantas name and colours,
          it is not Cobham that will be headlines in the sensationalist news media, is it.?

        2. Fred


          If you care to read the report, you’ll find the dodgy repairs most likely occurred in Europe, where the aircraft underwent heavy maintenance. The investigation could not trace maintenance records for the component prior to 2005, at which time the aircraft was owned by Turkish Airlines. My understanding is that Cobham acquired the aircraft from BAe Systems in the UK, who had previously leased it to Riau Airlines in Indonesia.

          Dodgy maintenance can happen anywhere, including Australia.

          1. comet

            The dodgy repairs were undocumented, so we can’t say they where they were done.

            But I assume that in a place like Australia or Europe there would be severe penalties for people who carry out aircraft repairs without documenting them. In more corrupt jurisdictions like Indonesia the penalties are waved for those who pay cash to the authorities.

            I’m wondering whether the purchase of aircraft that have been based in very corrupt countries is not such a good idea.

          2. Fred


            “The dodgy repairs were undocumented, so we can’t say they where they were done.”

            True, but that kind of maintenance isn’t done just anywhere. The engine needs to be disassembled and that can only be done in a heavy maintenance facility. The records show that heavy maintenance was conducted at a European maintenance organisation in 2005, 2006, 2008 and 2009. The dodgy weld-repair to the combustor housing was probably done during one of those documented visits; or it was done prior to 2005, when the housing was fitted to a different engine. There are no records for the combustor housing before 2005, so who knows where any heavy maintenance was done before that time?

  9. Bill

    I complained to QF after a Cobham managed flight from Broome to Perth a few months ago. The response a very nice, reassuring claim that QF was refurbishing its fleet. What the whole lot? Or does that just mean a paint job?

    1. comet

      The shoddy appearance of the aircraft you flew in probably represents the low standard of the airline.

      After Cobham had two major near-crash events – an Avro on fire and a 717 close to stalling – you should avoid flying with them ever again.

  10. Dan Dair

    BAe, the (effective) original manufacturers, or one of their maintenance providers, are most unlikely to have performed a ‘dodgy’ repair on anything.
    It’s just not in their interest.
    I can stretch my imagination a long way to imagine that THY might just possibly (with the wind in the right direction) have failed to properly document some repair-work. But it’s a struggle to imagine a major flag-carrier not doing a repair properly.?
    However, I’m really surprised to find that the ‘papertrail’ appears to show a component, ie. that combustor housing which is a used part but has no documentation prior to 2005.
    I’m really, really surprised that BAe’s documentation people haven’t picked-up on this (& changed the component) if it has been in their hands for any length of time.?
    I’d have thought that they’d pull the combustor housing on it’s next major engine check, replace it & have the ‘old’ one tested for quality, before returning it to the parts shelf, with appropriate paperwork or scrapping it.?

    1. Fred


      Bear in mind that a lot of airlines contract out their heavy maintenance to various third-party maintenance organisations. The airline and its regulator should be responsible for overseeing the work that is done, but the quality of that oversight varies enormously; some regulators are far better than others.

      In Australia, CAO 100.5 states that an aircraft Component History Card must be retained “until certification is made for the next overhaul following the last overhaul or a period of 1 year commencing immediately after the component has been permanently withdrawn from use, as the case requires”. If the rules are the same in Europe, then it’s not altogether surprising there’s no paperwork prior to 2005. The release certificate that was issued when the housing was fitted to the engine in 2005 stated that the housing was inspected and repaired in accordance with the engine manual. I guess the engine’s subsequent operators assumed the housing met Honeywell’s service limitations at that time, so they did not see any need to look deeper.

      Something else to bear in mind is that there have been big changes to the regulatory standards in Europe over the last couple of decades, with the JAA and then EASA taking over from the individual member States. I wouldn’t be at all surprised if something fell through the cracks!

  11. Tango

    What strikes me is that you have a repair made by supposedly accredited company that did not detect the problem? what am I missing? If they touched it they had to know it was bad, or they kludged it in which case they knew it was both bad and wrong to do so.

    If the inspection fails to find the problem then the inspection is bogus.
    If the part requires this kind of work regularly then there is a regulation problem, it should be removed from service until a part that does not fail is produced. this living with a fatal flaw is the worst things since Trump.

    Lastly, if an airline operatives an aircraft and does not have the capability to know what the aircraft history is, let alone its issue and what repairs are required and does not have the capability to ascertain said work is done right let alone documentation on what is a standard recurring problem, then its an airline issue as well. In short they should not be allowed to fly. Obviously its a serious issue if they don’t have the capability and they have to depend on a third party but are responsible for all of it, something is badly wrong. My take is the 3rd party is at fault assuming all inspections are done pre mandated and by someone who has the certified capably after they have their hands on it.

    I have things to do and can’t read the report this evening, who is CTM? where are they located?

    What is the time line on inspections and how fast does the crack propagate?

    Records should be held as long as an aircraft is flying. No records (due to history) all items out of compliance of in question have to be done before its allowed to operate in country.

    Lastly, the US while better does have issues. FAA is both responsible for air safety in enforcing regs and for growing the industry (as well as current ATC). that is contradictory and all three functions should be separated.

    NTSB investigates but can’t enforce though as Ben noted, they can embarrass as they fully investigate and do a provable cause of ALL accidents (most recent one was what appeared to be a low level stall that turns out to have been an Eagle hit on the tail plane)

    Some like the Eagle hit there is no answer for, those that are violations of existing regs and are not enforced or gone about in such a way as to allow unsafe ops they should have a halt mechanism to ops until its corrected rationally.

    Letting airlines fly for years with serious faults should never be allowed.

    I would put that engine repair in the serious fault area, sooner or latter is going to get screwed up and in most cases, aircraft fires aloft are fatal.

    sometimes their recommendation are costly and are not justified, sometimes spot on. It better and maybe the best we can do but not always logical. If they can’t embarrass it can be fata (DC10 losses)

    1. Fred


      1. CTM isn’t an organisation, it’s an abbreviation for Combustor Turbine Module. From the report: “The CTM consists of the combustor and the low-pressure turbine that are retained within the combustor housing (housing). The housing has four welded bosses located at the two, four, eight and ten o’clock positions (looking forward from the rear of the engine). A spigot pin is screwed into each welded boss to locate and retain the combustion liner. During normal operation, the fuel/air mixture is ignited in the combustion liner and supplies energy to the low-pressure turbine.”

      The crack occurred in the sheet metal adjacent to one of the welded bosses of the CTM housing. That welded boss had previously been repaired using a method that was not approved by the engine manufacturer. From the report: “Metallurgical examination of the fractured welded boss found that it had been weld-repaired on three separate occasions. The only recorded weld repair to the CTM housing was in 2005 although, as the CTM housing was an exchanged unit, its history could not be established. Therefore, either the CTM housing was repaired at or prior to 2005, or the housing was repaired after 2005 and the repair was not recorded. From the evidence available, the ATSB could not determine which was the case.”

      2. Inspections consisted of Hot Section Inspections every 6,000-cycles, where the CTM was removed from the engine. In addition to the scheduled heavy maintenance inspections of the engine modules, the aircraft maintenance system called for an ‘on-wing’ general visual inspection of the engine(s), including the CTM combustor housing, every 500 flight cycles or 6 months.

      From the report: “Honeywell published a system of maintenance where cracks, under a specific criteria, could be monitored during normal operation or repaired during heavy maintenance. Repairs depended on the length of the crack and the measured growth rate”. In this case, however, the crack was non-penetrating and had not previously been identified. Further, the unapproved repair method had decreased the thickness of the combustor housing, increasing the rate of propagation of the crack. The unapproved repair had not been identified in any of the subsequent heavy maintenance inspections.

      1. Dan Dair

        I’m surprised on a number of levels about all of this;
        Initially, I’m surprised that component part cards/documents are not retained for the life of the airframe, or at least retained electronically in some way.
        The trade in counterfeit and bogus aircraft spare parts is well-known at ‘official’ levels within the industry. This particular incident only reinforces that.

        If we accept that it was initially fitted to the engine ‘in good faith’ by engineers who saw the repair but assumed it was the documented one and further assumed the work was compliant, we must accept that in fact, the part card was bogus.
        If we accept that the part card was bogus, we then need the capability to back-trace that part through previous owners, breakers & parts dealers, etc..
        If we can’t do that, where is the retro-active part of the system for preventing this illegal trade, by tracing and imprisoning those who deal in ‘dodgy’ aircraft parts.?

        Further, how can it be that there could be no visual detection of a ‘known’ problem area, which went from OK to completely broken, apparently well-inside the inspection windows.?
        I accept that the repair was faulty, but it flew for years with the flawed part in place & then suddenly it completely failed without warning.
        Bearing in mind that the examination showed that the metal had cracked & then progressed into a hole, it seems unlikely that it happened more-or-less overnight. IMO it’s much more likely that the visual inspection failed to find a crack at it’s last check.?
        IF that was the case, how many more similar ‘known’-problems (not necessarily engine, or even BAe146 related) are lurking out there on these older airframes, because maintenance contractors are skimping on visual-checks, in order to make a profit.?
        (I understand that engineers are human & they make mistakes.
        The Virgin ATR tail & B737 engine-pod incidents make that clear.
        I am much more concerned with a failure to properly check the problem-areas, which airframe history will actually tell us are likely to occur in any particular model.?)

        (I’m not trying to hold you personally responsible for any of this, but you’ve offered yourself up as ‘defender’ of the ATSB’s report, so you’re the one being asked the questions.!!!!!)

  12. Fred


    I’m only trying to put a few things into perspective based on my limited understanding of the system. As you know, I’m a pilot, not an engineer, and I certainly don’t claim to be an expert in this area. That said, I think it is far too simplistic to pin all the blame on Cobham for this incident when there are wider issues at play that are not Cobham’s fault.

    The lack of documentation regarding the history of the failed CTM housing highlights a systemic issue relating to the tracking of aircraft components. I agree that critical components and their maintenance records should be tracked for the entire life of the component. Nevertheless, the best tracking system in the world won’t prevent dodgy maintenance organisations from using non-authorised repair techniques. I don’t know what the solution is, but better surveillance and monitoring by the regulators must surely be a priority, together with closer supervision of any maintenance by the aircraft operator at the time the maintenance is conducted.

    According to the report, the crack that caused the CTM housing to fail was a “non-penetrating” crack, ie “a crack that did not penetrate through the full thickness of the housing sheet metal”. Consequently, it was not visible during a visual inspection and may only have been identifiable when the CTM was fully disassembled, as occurs during a scheduled heavy maintenance inspection. The last heavy maintenance inspection was completed in 2009, five years before the incident. The crack may have formed after that inspection and then gradually propagated, unseen, until the housing failed.

    I’m not sure that fracturing of the CTM housing is a “known problem area”, as you stated. Although cracking in the welded boss was reported to be quite common, the engine manufacturer had a system of maintenance where such cracks could be monitored during normal operation and repaired during heavy maintenance. The report states: “the associated visual inspections were historically effective in detecting cracks around the welded boss prior to catastrophic failure”. A search of the records by Honeywell revealed only one other fracture of the CTM housing, some 10 years prior to the Cobham incident. The engine manufacturer has since amended its maintenance manual such that continued operation of the engine is no longer permitted when cracks are identified in the welded boss, and a cracked welded boss now requires replacement of the entire CTM housing.

    I should note here that, in Cobham’s incident, the crack was not in the welded boss; it was in the sheet metal adjacent to the welded boss. Grinding associated with a weld-repair to the welded boss had reduced the thickness of the adjacent sheet metal. That was not an approved repair method and created the conditions for a crack to develop.

  13. Ben Sandilands


    There is nothing difficult in Australian law in determining who is to blame in this incident, had it resulted in serious injuries, fatalities or loss of property. It would have been the operator, in this case Cobham.
    The law operates here much the same as it does in much of the developed world, imperfectly, but there is always an entity which is ultimately responsible for safety outcomes, however unfair that might seem to some.

    You’ve made an exhausting case that our law in that regard is unfair. But that is also irrelevant, because it is the law. A curious consequence of this situation is that had Cobham been operating the jet on behalf of another carrier, say Qantas, as it often does operate Qantaslink branded aircraft for Qantas, then Qantas would in this hypothetical have been the responsible party.
    The law requires the operator of the jet to take full responsibility for all safety outcomes. Had the Buffalo crash occurred here, Continental would have been solely responsible for the safety outcome, because in our legal practice, safety outcomes cannot be outsourced. The airline whose brand in on the aircraft is responsible for everything that happens, although it may, if it is quick, sue the supplier of goods and services for every last penny it has. (I’m ignoring the machinations of insurance arrangements, which do not apply to ultimate criminal liability for loss of life or property, which irrespective of insurance outcomes, could see executives jailed and operating certificates revoked.).
    Your detailed commentary on unfairness is however a reminder that regulators ought to insist on far greater depths of disclosure and record keeping in relation to aircraft maintenance and the repair of components.

    Your comments are interesting. They could be described as libertarian, in that libertarians tend to the view that no-one can ever be bound or held to account for anything other than a generalised principle of doing the least harm by removing legal protections from just about every activity, and freeing the individual from the constraints of collective responsibility.

    That may not be your intention of course.

    1. Fred

      No, that is absolutely NOT my intention, Ben. The full weight of the law should be brought to bear upon individuals or organisations where it can be shown they have behaved negligently, recklessly or have intentionally violated the law. Surely our ultimate aim should be to improve safety outcomes and achieve the safest possible system for the travelling public. In terms of safety improvement, I feel there is little or nothing to be gained by taking punitive action against an individual or organisation simply because the law says it can do so. Indeed, research into organisational accidents by James Reason and others has shown that kind of action only makes things worse. Is that what we really want?

      1. Fred

        Whilst James Reason’s thinking may not be acceptable here at Plane Talking, it has been adopted by safety organisations and regulators all over the world, including the FAA, the NTSB the UK’s CAA and Transport Canada. The following links provide additional information:

        1. Ben Sandilands

          Suggesting James Reason’s methodology could be unacceptable here is ridiculous. So is suggesting that somehow the airline could evade full responsibility for safety outcomes.

          As I’ve often reported in the past, there are signs that Reason is no longer held in the respect he merits by our safety investigator and regulator. Much of the coverage here has been about a growing contempt for ‘old fashioned’ values in those bodies, including outright contempt for full disclosure to the public, and the flying community world wide, and to the Minister responsible.

          There seems to be diminished room in them for both reason and Reason. My extensive contacts in the industry can be assured I’ll continue to resist the humbug.

          1. Fred

            Perhaps ‘not acceptable’ was the wrong turn of phrase. How about ‘too libertarian’? After all, it was you who described my comments as ‘libertarian’ when I espoused Reason’s views in my earlier posts.

          2. Fred

            And by the way, I have never suggested that Cobham is not responsible for safety outcomes under Australian law. That is not in dispute. The point I have tried to make is that CASA is quite justified in not pursuing Cobham, when the factors that caused the incident were outside the company’s control.

  14. Dan Dair

    My point with the ‘known problem’ aspect,
    was intended to be about the cracking around the bosses, not the failure of the whole liner.
    As you mentioned, Honeywell put in place a visual inspection regime for the bosses related to time & cycles, in-between major services.
    I do accept however, that I had not realised that the crack would not be visible in those inspections, as it was ‘non-penetrating’.

    I do wonder whether there is an element of hope or obfuscation in the particular ATSB comment that “the crack was non-penetrating”.
    Clearly, by the time the liner actually failed, the crack MUST have been fully-penetrating, to allow the fuel/combustion into the rest of the engine.
    I accept that the repair was non-compliant & I do not specifically accuse the maintenance engineers of failing to notice the crack.
    I’m interested in how the ATSB can ‘know’ at which time the crack was first visible from the inspection-point.?

    I do agree with you about Reason reasoning. The acceptance of full-disclosure in an investigation because there is no ‘retribution’ for a genuine mistake is the obvious way to maintain a safety-culture & improve future-safety.
    I agree too, that anyone of malicious of negligent action should be prosecuted to the fullest extent of the law.

    1. Fred


      I believe the conclusion that the crack was “non-penetrating” came from Honeywell’s metallurgical examination of the fractured housing. Unfortunately I don’t know enough about metallurgy to say how they came to that conclusion. At some point the crack must have begun to penetrate the surface, as you said. My understanding is they don’t know with any certainty when that occurred. It may not have occurred until shortly before the housing fractured, but it may have occurred some time beforehand. The report states: “In terms of Cobham Aviation Services Australia’s conduct of the most recent 500-hourly on-wing engine inspection, it was reasonable that, if the crack existed at that time, it was not visually-identified as:
      • the crack was non-penetrating, meaning that it would probably have only been identifiable when the CTM was fully-disassembled (such as at a scheduled heavy maintenance inspection)
      • there were no other, more usual, indications of a crack in the CTM, such as:
      – increases in the engine condition trend monitoring data parameters
      – blacking around any crack edges due to combusted gas leakage or fretting.”

  15. Ben Sandilands


    CASA isn’t ever justified in ignoring the law, as it did in the Pel-Air saga, or treating the executive branch and the people of Australia with arrogant contempt. It’s statement in relation to Cobham was a total nonsense, in that it completely contradicted its position on Tiger Airways.

    This is an agency that doesn’t have the capacity to overhaul aviation regulations even to its own timetable, and let 15 people die in the Transair disaster because it knew the airline was dangerous yet elected, as per its Senate committee evidence, to take no action, contrary to its obligations under the law, and without warning the public.
    You are in the wrong place if you think I’m going to ignore its resolute unwillingness or helplessness when it comes to being an effective safety regulator.

  16. Fred

    Nobody asked you to Ben, but how about a little balance?

    CASA’s failings are well documented. What do you propose as a solution to improve the safety culture in Australia? On the one hand you imply that James Reason’s methodology should merit more respect, and yet on the other you seem to advocate the punitive culture that Reason and others reject.

    I’ll reframe the question I asked earlier: Do we want a punitive culture that is likely to encourage individuals and organisations to hide their mistakes; or do we want a culture that encourages open and honest reporting, but at the same time does not tolerate wilful violations or reckless behaviour? Surely the answer is obvious.

    1. Ben Sandilands

      I’m on the side of those who want an accountable culture in the public administration of air safety in Australia. An administrative branch that is subordinate to and the servant of the executive branch. In other words, one that is appropriate to a parliamentary democracy, not some tin pot third world state.
      What do you stand for we might wonder? Just a string of excuses for practices that undermine air safety. If you were to better inform yourself about the current situation in this country you’d know that Australia has policy settings in aviation that are contrary to those endorsed by ICAO and the NTSB and FAA in some areas, and put commercial expediency above all other considerations, including the direction taken by James Reason.

      1. Fred

        I am very well informed with respect to safety regulation in this country, thank you. As a professional pilot, my safety depends upon it at least as much as yours and other members of the travelling public. My comments were not aimed at making excuses. They were intended to put a few things into perspective with a view to finding a better way forward than constant harping that does nothing to improve safety.

        You have made it abundantly clear that dissenting opinions are not welcome at Plane Talking. That is a very great shame, given the limited discourse on aviation matters in the media here in Australia. Perhaps you’ll be glad to know that I will not be adding my comments to any further discussions.

  17. Dan Dair

    IMO Ben can get a bit ‘cranky’ from time to time, especially on subjects that he takes a very personal interest in.
    (We’re all well-aware how he has ‘championed’ the Pel-Air ditching re-investigation. He might be best mates with Nick Zenophon, for all I know.?)

    Anyway, I’m not making any excuses for him, he can do that for himself if he wants to
    & of course it’s his blog, so he wields the ultimate power.!

    I’d just like to suggest that you have a break & return when you’re feeling a bit more comfortable with the rest of us.
    I respect your comments, which are generally interesting and very well-informed & as I’ve told you before, sometimes I’ve laughed out loud at your sense of humour.

    Even if Ben isn’t, I’ll be sorry to see you go.!


    1. Fred


      Thank you – I truly appreciate your comments and have thoroughly enjoyed our on-line exchanges.


  18. Ben Sandilands

    I think discussions are an important but of course voluntary part of on-line media, offering much more versatility and immediacy than ‘Letters to the Editor’. If any of us disagree with an opinion or perspective then by all means say so, as I do, occasionally.
    One thing I’ve noticed in recent months is the Twitter followers of Plane Talking are running parallel discussions on topics it reports on, and if that trend continues to grow, the twitterverse will be the larger place for discussions about posts.
    This has its problems. Twitter isn’t necessarily a more useful format at all, given the brevity required, but it’s faster and handles photos and graphics reasonably well in some cases.
    At this stage there doesn’t appear to much commonality among those who use Twitter and those here on Comments. Each has participants who only respond on one platform, rather than both.

  19. Dan Dair

    Since Twitter is so proscriptive about the number of characters per posting,
    on that platform, I can hardly indulge in the length of rant I usually resort to.???

    I’d actually no idea the Twitter platform was so well-used.
    I’ll have to pay it some attention.!!!

  20. Sam Jackson

    Now, when everyone has finished banging their drums; can we have a look at the realities? For example a flawed design which requires constant repair to peripherals. This engine section (component) has, in what, 10 short years often needed ‘repair’. Clearly, if the lug is in need of constant monitoring and a repair protocol, the underlying reasons for that need examination. I think we all have a fair idea of what happens within and the pressures it’s subject to of a ‘combustor’. Furthermore – if a 0.002 thickness of metal is the difference between flame in and flame out, then there is an inherent problem in the design specification.

    There may be flaws in the system for checking and recording repairs, there is in every system. But – reality is a prospective buyer cannot, nor will a survey engineer on a ‘pre-buy’ inspection take out a micrometre and check the thickness (or lack thereof) of every ‘skin’ in the aircraft. The ‘grinding pass’ may well have been a couple of thou too much – but how could Cobham, or anyone else for that matter have known? The lug ‘repair’ prescription is a result of inherent faults within the combustor liner design. If, indeed there is an existing design fault, then how is it to tracked back to the designers weight/ cost allowance tolerances, let alone to the apprentice welder with a grinder. No: this dog won’t hunt – what of cracks in the combustion layer, which lead to lug failure, which lead to fine tolerance grinding, which start engine fires? Only one place to look foe answers.

    1. Dan Dair

      Sam Jackson,
      Now that you’ve got-down off your own soapbox….. (joke)

      Can I ask a question of you, which I alluded to with Fred.?
      How big a problem has this particular issue been with these Honeywell engines.?
      The fact that Honeywell had an inspection regime in place AND had requirements specified for welding repairs would imply that the problems surrounding the liner & bosses is well-known to the manufacturer.?
      On the other hand, the ATSB report appears to suggest that there isn’t any significant history of actual failures which relate to this engine-type.?

      NB. I agree completely about the 2-thousandths tolerance-deficit. Sure, it’s out of tolerance, but as I said earlier, it’s flown for ages with no apparent problems. The idea that the 2-thou’ makes all the difference is a bit rich to me.? That statement would imply that it is inevitable that the liner MUST fail if it is out of tolerance.?
      Surely if that IS the case, it would make more sense to have made the liner a couple of millimeters thicker in the first place,
      or perhaps they ought to have specified that welded repairs were unacceptable ten or more years ago, when this particular problem was already apparent.

  21. PAIN_P2

    Agree with your comments Ben on twitter versus blogs etc. I also watched with interest your to & fro debate with Fred suggesting unbalanced reporting by you on this and other PT blog pieces where CASA, ATSB, & sometimes ASA, come under IMO justified criticism.

    Anyway for what is worth here is part of a post that I wrote on the Aunty Pru Forum over a week ago in response to this PT article ( AP link: )

    “… CASA & ‘just culture’ – Fantasy or fact?

    Yes indeed this is an interesting one… Huh
    “K” said – Now Ben Sandilands over at Crikey has written an article on the PLANE Talking blog which is ‘interesting’ in that it mentions the CASA response to the incident. Have a read of the ATSB report, then the article. I can’t see why CASA would want to become embroiled in a prosecution, I can, just, see Ben’s point, but I fail to see anything of value other an expensive legal nightmare resulting from direct action by CASA – in this case.
    Anyway – FWIW, if time allows, have a scamper through both: personally, I think I may have to agree to disagree with Ben on this one. Handing over.

    This has also flowed through to the comments, with a bit of a ding dong going on between Fred & Ben.. (refer comments above etc.)

    …Perhaps Ben is overreaching with this one but again I think there are greater messages in here that are sadly being missed.

    However first to this incident, IMO the best part about this report is that for once we are not talking about the ATSB – i.e. they have actually done their job and clearly stated the facts as presented.

    For mine the key to this incident and the ‘just culture’ message is in the following passage from the Final Report…(refer my post link above)

    …Now back to what is IMO the central issue to Ben’s article that is now causing debate & contention in the ensuing commentary.

    First the background. Ben Sandilands has witnessed for many decades the administration of the Oz aviation safety system being manipulated, obfuscated, abused, historically tarnished, neglected etc..etc; by a rampant, seemingly untouchable bureaucracy that governments of either colour totally abscond from proper oversight or governance.

    So naturally, like much of industry (refer ASRR report), Ben’s trust quotient & ‘bollocks’ alert will be rapidly pinging when it comes to the regulator making comments like…

    “…We also have system based on just culture to ensure open reports such as are made to the ATSB and mistakes rectified…”

    …Until proven otherwise “just culture” & CASA in the same sentence will be met with much scepticism from an industry (including some aviation journos) that have been bullied, belittled, badgered and embuggerised by the “Iron Ring” big “R” regulator and supporting department for the best part of three decades.

    Seaview…Lockhart…PelAir cover-up…Mildura Fog duck-up…VARA ATR bird strike abberration…the list & the bollocks continue – miniscule Chester please take note of what IMO is the most important part of Ben’s article:
    “The new Minister Darren Chester is meeting the grass roots aviation industry in Tamworth this Friday, one hopes before the government goes into caretaker mode on the calling of a general election.

    It is an important meeting. It is also important for the Minister to note that his predecessors were treated with arrogant contempt by his department in relation to aviation matters and public safety, and that taking visible control of his portfolio and remembering he is a representative of the people, not unaccountable bureaucrats or corporate entities, is a prerequisite for being held in respect.”
    End Quote


  22. Sam Jackson

    (Smile) – Nay, not a soap-box Dan; ‘tis but a small stump. The ATSB investigator has, as P2 defines it, not done too shabby a job in this report. Honeywell had and still have a procedure in place to deal with a ‘known’ potentially weak area; and, that procedure has stood the test of time. I have no doubt that amendments now in place will adequately cover any other potential trouble spots their skilled engineers and experts may discover. Company reputations and profits depend on the ‘manufacturer’ getting it right – every time. The pressures and temperatures within the combustion section of a modern jet engine are insane; these engines have been in service a long time now and there can be little doubt the repair, done when required, as specified, has been effective. ATSB do reflect this in their report; mark you they have no skin in the game; their report also reflects that. Hopefully, Greg Hood will be able to stop the downward trend and PC outcomes we have seen the last half decade.

    But CASA – well that is a horse of a different colour. Personally, I don’t believe there is much in this one incident, to get them reaching for the big R book and hammering the company. It could even be that the company was as much sinned against as it was sinful. Caveat Emptor has long been a hard held tenet of aviation traders, for bloody good reason. No, the beef is with the cynical CASA point scoring, by claiming, all of a sudden, that a ‘just’ culture is in place. Bollocks. Just when it suits and only when it suits is much nearer the truth. Close observers know that this is just another cycle in the no change to policies of strictly no liability, responsibility or accountability. It has been thus for at least three decades I have witnessed. This will not be allowed to change under the current lunatic running the asylum.

    So, we have a known, high stress engine area which, occasionally, needs careful, concise, proper repair. We have a manufacturer doing all the right things. We have an ATSB report which, in the main, is acceptable. Then we have the CASA ‘touchy-feely’ response. Now a cynic would (quite rightly) say that CASA would not dare upset a company like Cobham, in any event. The notion of annoying a big hitter like Cobham – when they probably have the ‘law’ on their side becomes unthinkable. A cynic could say that ‘just culture’ is just buzz words are written on the dunny walls, but Gibson is silly enough to use it, after a non event to score much needed Brownie points. Two thou’ does not a law suit make – IMO. Right then; off the stump and back to my knitting, having spent my two bob as best pleased me.

    1. Dan Dair

      “having spent my two bob as best pleased me”

      Two bob well-spent IMO.!!

  23. Dan Dair

    Sam Jackson,
    “Now a cynic would (quite rightly) say that CASA would not dare upset a company like Cobham, in any event”

    So is this actually what it boils-down to…..?
    CASA isn’t prepared (for whatever reason.???) to take-on any of the ‘big-hitters’ in Australian aviation.?

    The law probably is on their(Cobham’s) side with this particular incident, so as you say, why then does CASA even mention ‘just-culture’ at all.?
    It would appear very strongly that the law was not on the side of Pel-Air & by inference REx when CASA was ‘looking-the-other-way’ over various procedural deficiencies at that time.?
    Additionally, why no penalties, sanctions or procedural changes for QF or VA (or their subsidiaries & sub-contractors) over the various near-miss, fuel-starvation, undiagnosed impact-damage or attempted landings on ‘stuff-that-looks-a-bit-like-a-runway-from-here-in-twilight’, which have occurred over the last couple of years.?
    (why is there no push to begin a ten-year program of installation of proper lighting, radar, ILS, weather-radar, etc, etc across all of Australias’ major (by passenger volumes) commercial airports.?)

    Could the same ‘laissez-faire’ attitude by the regulators be attributed to the way they deal with the much smaller (& less powerful) General Aviation operators.?

  24. Sam Jackson

    Gee whizz Dan – too much to pile into a potted post on Ben’s blog. ‘We’ have, extensively, discussed CASA and it’s antics on the Aunty Pru website forum, which is easily accessed. But fair warning, there is a lot of coverage. But, in short, your comments above more or less reflect industry and some Senators concerns; of which there are many. The degree of frustration and old fashioned, non PC anger within the industry has reach the stage where any politician, seeking re election should be paying attention; real attention, before jobs, investment, export dollars are lost forever as an independent, essential industry collapses from sheer neglect. The intention is to remove the catch-all of the bi-partisan cop out and make ‘industry’ well being a political issue, rather than a nice place for a selfie and a free feed. FWIW have a skim through this – it’s now four years old and (IMO) even more relevant now. Cheers Ben – the link is bug free, from our own library.

    1. Dan Dair

      Sam Jackson,
      OK, I read your link, more or less word-for-word.

      Firstly, that’s a good example of why I’m not on Pprune.!
      I let Ben read this kind of stuff & pick the bones out of it for me.
      He obviously has more experience & insight than me into these matters & I just ‘glaze-over’ as I’m reading. (It’s too hard.!……. quote:Andy & Randy Pig. (Miss Piggy’s nephews))

      Secondly, this was published Four & a half years ago & there’s been no obvious progress. No-wonder Ben (& of course GA people) have got such a bee-in-their-bonnet about it.!!
      I’ve had a couple of managers who acted like the CASA management & inspectors. (needless to say they’re not my managers now) You can’t go up against them, you can’t get back on their good side once you’ve crossed them & they’re part of the established management, so you’re wasting your time complaining to their manager about them.

      I knew from these pages that CASA’s implementation of the law & regulations was patchy & erratic. I really hadn’t grasped though, the extent to which GA was being affected by CASA’s behavior.
      You make a good point that airlines have people to ‘interface’ with the regulator, who are also ‘pen-pushers’. Most GA people will have to deal with their inspector or administrators directly & have no ‘clout’ to wield in order to help speed something up or change someone’s mindset.

      The ‘chooks & the chimney’ anecdote captured the spirit of what you’re fighting against very well.

      I am wiser than I was before I started reading the petition report,
      but now I need a lie-down.!!!

  25. Sam Jackson

    Dan, I’m sat here still laughing at your response. I admire your tenacity, it’s a long read through to the ‘Chook-shed’ incident, well done, have an AP Choc Frog. The point is nothing has changed, not for the better anyway; despite the Pel-Air inquiry, multiple close calls (Mildura) the Forsyth review (ASRR) and the TSBC peer review and then millions wasted pointlessly writing ‘rules’ against which expensive, time consuming exemption must be published and maintained – 3000 odd ICAO ‘differences’ for an example. IMO, all for nought; the ‘rules’ ain’t the problem, it’s the regulator. Unless that very real problem is addressed, it will be another quarter century and another 300,000,000 bucks down the Swanee, for no return on the investment. Thank you for taking the time, it is appreciated.

    1. Dan Dair

      The petition was very interesting reading, but also hard work. Hence why it took me two days to actually work through it. I kept stopping & coming back to it…. that & the fact that I’ve got other stuff to do.! (haven’t we all.??)

      It’s amazing (if your figures are correct & I have no reason to suspect otherwise) to contemplate the spending of $300 million & not to appear to have moved forwards in any way. (no wonder Nick Xenophon is so hopping-mad)
      How much aviation infrastructure could that money have paid for instead.?? (a good bite at the installation of ILS at all major passenger airports, which is one of my hobby-horses.?)

      Without wishing to sound defeatist, it’s a really big ask to turn-around the culture within such a large arm of government (again, assuming your allegations are correct & I have no reason to suspect otherwise) at all & even more-so in the context of trying to change that culture before it has effectively killed-off a significant part of Australian GA.?

      To finish on a more positive note;
      it would have been rude of me not to have taken the time to read the petition report you’d suggested, after you had so thoroughly responded to & elaborated upon the points I made.
      The appreciation is reciprocated.

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