Archives For Safety

The practice of safety engineering in various high consequence industries.

A while ago, while I was working on a project that would have been based (in part) in Queensland I was asked to look at the implications of the Registered Professional Engineers Queensland act for the project, and in particular for software development. For those not familiar, the Act provides for the registration of professional engineers to practise in Queensland. If you’re not registered you can’t practice unless you’re supervised by a registered engineer. Upon registering you then become liable to a statutory Board of Professional Engineers for your professional conduct. Oh yes and practicing without coverage is a crime.

While the act is oriented squarely at the provision of professional services, don’t presume that it is solely the concern of consultancies.  Continue Reading…

AirAsia QZ8501 CVR (Image source - AP Photo-Achmad Ibrahim)

Stall warning and Alternate law

This post is part of the Airbus aircraft family and system safety thread.

According to an investigator from Indonesia’s National Transportation Safety Committee (NTSC) several alarms, including the stall warning, could be heard going off on the Cockpit Voice Recorder’s tape.

Now why is that so significant?

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Aviation is in itself not inherently dangerous. But to an even greater degree than the sea, it is terribly unforgiving of any carelessness, incapacity or neglect.

 

Captain A. G. Lamplugh, British Aviation Insurance Group, London, 1930s.

I was cleaning out my (metaphorical) sock drawer and came across this rough guide to the workings of the Australian Defence standard on software safety DEF(AUST) 5679. The guide was written around 2006 for Issue 1 of the standard, although many of the issues it discussed persisted into Issue 2, which hit the streets in 2008.

DEF (AUST) 5679 is an interesting standard, one can see that the authors, Tony Cant amongst them, put a lot of thought into the methodology behind the standard, unfortunately it’s suffered from a failure to achieve large scale adoption and usage.

So here’s my thoughts at the time on how to actually use the standard to best advantage, I also threw in some concepts on how to deal with xOTS components within the DEF (AUST) 5679 framework.

Enjoy 🙂

Indonesian AirNav radar screenshot (Image source: Aviation Herald)

So what did happen?

This post is part of the Airbus aircraft family and system safety thread

While the media ‘knows’ that the aircraft climbed steeply before rapidly descending, we should remember that this supposition relies on the self reported altitude and speed of the aircraft. So we should be cautious about presuming that what we see on a radar screen is actually what happened to the aircraft. There are of course also disturbing similarities to the circumstances in which Air France AF447 was lost, yet at this moment all they are are similarities. One things for sure though, there’ll be little sleep in Toulouse until the FDRs are recovered.

Boeing 787-8 N787BA cockpit (Image source: Alex Beltyukov CC BY-SA 3.0)

The Dreamliner and the Network

Big complicated technologies are rarely (perhaps never) developed by one organisation. Instead they’re a patchwork quilt of individual systems which are developed by domain experts, with the whole being stitched together by a single authority/agency. This practice is nothing new, it’s been around since the earliest days of the cybernetic era, it’s a classic tool that organisations and engineers use to deal with industrial scale design tasks (1). But what is different is that we no longer design systems, and systems of systems, as loose federations of entities. We now think of and design our systems as networks, and thus our system of systems have become a ‘network of networks’ that exhibit much greater degrees of interdependence.

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787 Battery after fire (Image source: NTSB)

The NTSB have released their final report on the Boeing 787 Dreamliner Li-Ion battery fires. The report makes interesting reading, but for me the most telling point is summarised in conclusion seven, which I quote below.

Conclusion 7. Boeing’s electrical power system safety assessment did not consider the most severe effects of a cell internal short circuit and include requirements to mitigate related risks, and the review of the assessment by Boeing authorized representatives and Federal Aviation Administration certification engineers did not reveal this deficiency.

NTSB/AIR-14/01  (p78 )

In other words Boeing got themselves into a position with their safety assessment where their ‘assumed worst case’ was much less worse case than the reality. This failure to imagine the worst ensured that when they aggressively weight optimised the battery design instead of thermally optimising it, the risks they were actually running were unwittingly so much higher.

The first principal is that you must not fool yourself, and that you are the easiest person to fool

Richard P. Feynman

I’m also thinking that the behaviour of Boeing is consistent with what McDermid et al, calls probative blindness. That is, the safety activities that were conducted were intended to comply with regulatory requirements rather than actually determine what hazards existed and their risk.

… there is a high level of corporate confidence in the safety of the [Nimrod aircraft]. However, the lack of structured evidence to support this confidence clearly requires rectifying, in order to meet forthcoming legislation and to achieve compliance.

Nimrod Safety Management Plan 2002 (1)

As the quote from the Nimrod program deftly illustrates, often (2) safety analyses are conducted simply to confirm what we already ‘know’ that the system is safe, non-probative if you will. In these circumstances the objective is compliance with the regulations rather than to generate evidence that our system is unsafe. In such circumstances doing more or better safety analysis is unlikely to prevent an accident because the evidence will not cause beliefs to change, belief it seems is a powerful thing.

The Boeing battery saga also illustrates how much regulators like the FAA actually rely on the technical competence of those being regulated, and how fragile that regulatory relationship is when it comes to dealing with the safety of emerging technologies.

Notes

1. As quoted in Probative Blindness: How Safety Activity can fail to Update Beliefs about Safety, A J Rae*, J A McDermid, R D Alexander, M Nicholson (IET SSCS Conference 2014).

2. Actually in aerospace I’d assert that it’s normal practice to carry out hazard analyses simply to comply with a regulatory requirement. As far as the organisation commissioning them is concerned the results are going to tell them what they know already, that the system is safe.

Compliance finding

04/12/2014

Here’s a short tutorial I put together (in a bit of a rush) about the ‘mechanics’ of producing compliance finding as part of the ADF’s Airworthiness Regime. Hopefully this will be of assistance to anyone faced with the task of making compliance findings, managing the compliance finding process or dealing with the ADF airworthiness certification ‘beast’.

The tutorial is a mix of how to think about and judge evidence, drawing upon legal principles, and how to use practical argumentation models to structure the finding. No Dempster Shafer logic yet, perhaps in the next tutorial.

Anyway, hope you enjoy it. 🙂

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A report issued by the US Chemical Safety Board on Monday entitled “Regulatory Report: Chevron Richmond Refinery Pipe Rupture and Fire,” calls on California to make changes to the way it manages process safety.

The report is worth a read as it looks at various regulatory regimes in a fairly balanced fashion. A strong independent competent regulator is seen as a key factor for success by the reports authors, regardless of the regulatory mechanisms. I don’t however think the evidence is as strong as the report makes out that safety case/goal based safety regimes perform ‘all that better’ than other regulatory regimes. Would have also been nice if they’d compared and contrasted against other industries, like aviation.

Cassini Descent Module (Image source: NASA)

When is an interlock not an interlock?

I was working on an interface problem the other day. The problem related to how to judge when a payload (attached to a carrier bus) had left the parent (much like the Huygens lander leaving the Cassini spacecraft above). Now I could use what’s called the ‘interlock interface’ which is a discrete ‘loop back’ that runs through the bus to payload connector then turns around and heads back into the bus again. The interlock interface is there to provides a means for the carriers avionics to determine if the payload is electrically mated to the bus. So should I use this as an indication that the payload has left the carrier bus as well? Well maybe, maybe not.

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Midlands hotel

A quick report from sunny Manchester, where I’m attending the IET’s annual combined conference on system safety and cyber security. Day one of the conference proper and I got to be lead off with the first keynote. I was thinking about getting everyone to do some Tai Chii to limber up (maybe next year). Thanks once again to Dr Carl Sandom for inviting me over, it was a pleasure. I just hope the audience felt the same way. 🙂

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TCAS and Tenerife

05/10/2014

Tenerife disaster moments after the impact

TCAS, emergent properties and risk trade-offs

There’s been some comment from various regulator’s regarding the use of Traffic Collision Avoidance System (TCAS) on the ground, experience shows that TCAS is sometimes turned on and off at the same time as the Mode S transponder. Eurocontrol doesn’t like it and is quite explicit about their dislike, ‘do not use it while taxiing’ they say, likewise the FAA also states that you should ‘minimise use on ground’. There are legitimate reasons for this dislike, having too many TCAS transponders operating within a specific area can degrade system performance as well as potentially interfering with airport ground radars. And as the FAA point out operating with the AD-B transponder on will also ensure that the aircraft is visible to ATC and other ADS-B (in) equipped aircraft (1). Which leaves us with the question, why are aircrew using TCAS on the ground? Is it because it’s just easy enough to turn on at the push back? Or is there another reason?

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Interesting article on old school rail safety and lessons for the modern nuclear industry. As a somewhat ironic addendum the early nuclear industry safety studies also overlooked the risks posed by large inventories of fuel rods on site, the then assumption being that they’d be shipped off to a reprocessing facility as soon as possible, it’s hard to predict the future. 🙂

Right hand AoA probes (Image source: ATSB)

When good voting algorithms go bad

Thinking about the QF72 incident, it struck me that average value based voting methods are based on the calculation of a population statistic. Now population statistics work well when the population is normally distributed, or otherwise clustered around some value. But if the distribution has heavy tails, we can expect that extreme values will occur fairly regularly and therefor the ‘average’ value means much less. In fact for some distributions we may not be able to put a cap on the upper value that an ‘average’ could be, e.g. it could have an infinite value and the idea of an average is therefore meaningless.

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An interesting post by Mike Thicke over at Cloud Chamber on the potential use of prediction markets to predict the location of MH370. Prediction markets integrate ‘diffused’ knowledge using a market mechanism to derive a predicted likelihood, essentially market prices are assigned to various outcomes and are treated as analogs of their likelihood. Market trading then established what the market ‘thinks’ is the value of each outcome. The technique has a long and colourful history, but it does seem to work. As an aside prediction markets are still predicting a No vote in the upcoming referendum on Scottish Independence despite recent polls to the contrary.

Returning to the MH370 saga, if the ATSB is not intending to use a Bayesian search plan then one could in principle crowd source the effort through such a prediction market. One could run the market in a dynamic fashion with the market prices updating as new information comes in from the ongoing search. Any investors out there?

MH370 underwater search area map (Image source- Australian Govt)

Just saw a sound bite of our Prime Minister reiterating that we’ll spare no expense to find MH370. Throwing money is one thing, but I’m kind of hoping that the ATSB will pull it’s finger out of it’s bureaucratic ass and actually apply the best search methods to the search. Unkind? Perhaps, but then maybe the families of the lost deserve the best that we can do…

Enshrined in Australia’s current workplace health and safety legislation is the principle of ‘So Far As Is Reasonably Practicable’. In essence SFAIRP requires you to eliminate or to reduce risk to a negligible level as is (surprise) reasonably practicable. While there’s been a lot of commentary on the increased requirements for diligence (read industry moaning and groaning) there’s been little or no consideration of what is the ‘theory of risk’ that backs this legislative principle and how it shapes the current legislation, let alone whether for good or ill. So I thought I’d take a stab at it. 🙂 Continue Reading…

Finding MH370

26/08/2014

MH370 underwater search area map (Image source- Australian Govt)

Finding MH370 is going to be a bitch

The aircraft has gone down in an area which is the undersea equivalent of the eastern slopes of the Rockies, well before anyone mapped them. Add to that a search area of thousands of square kilometres in about an isolated a spot as you can imagine, a search zone interpolated from satellite pings and you can see that it’s going to be tough.

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On Artificial Intelligence as ethical prosthesis

Out here in the grim meat-hook present of Reaper missions and Predator drone strikes we’re already well down track to a future in which decisions as to who lives and who dies are made less and less by human beings, and more and more by automation. Although there’s been a lot of ‘sexy’ discussion recently of the possibility of purely AI decision making, the current panic misses the real issue d’jour, that is the question of how well current day hybrid human-automation systems make such decisions, and the potential for the incremental abrogation of moral authority by the human part of this cybernetic system as the automation in this synthesis becomes progressively more sophisticated and suasive.

As Dijkstra pointed out in the context of programming, one of the problems or biases humans have in thinking about automation is that because it ‘does stuff’, we find the need to imbue it with agency, and from there it’s a short step to treating the automation as a partner in decision making. From this very human misunderstanding it’s almost inevitable that the the decision maker holding such a view will feel that the responsibility for decisions are shared, and responsibility diluted, thereby opening up potential for choice shift in decision making. As the degree of sophistication of such automation increases of course this effect becomes stronger and stronger, even though ‘on paper’ we would not recognise the AI as a rational being in the Kantian sense.

Even the design of decision support system interfaces can pose tricky problems when an ethical component is present, as the dimensions of ethical problem solving (time intensiveness, consideration, uncertainty, uniqueness and reflection) directly conflict with those that make for efficient automation (brevity, formulaic, simplification, certainty and repetition). This inherent conflict thereby ensuring that the interaction of automation and human ethical decision making becomes a tangled and conflicted mess. Technologists of course look at the way in which human beings make such decisions in the real world and believe, rightly or wrongly, that automation can do better. What we should remember is that such automation is still a proxy for the designer, if the designer has no real understanding of the needs of the user in forming such ethical decisions then if if the past is any guide we are up for a future of poorly conceived decision support systems, with all the inevitable and unfortunate consequences that attend. In fact I feel confident in predicting that the designers of such systems will, once again, automate their biases about how humans and automation should interact, with unpleasant surprises for all.

In a broader sense what we’re doing with this current debate is essentially rehashing the old arguments between two world views on the proper role of automation, on the one side automation is intended to supplant those messy, unreliable humans, in the current context effecting an unintentional ethical prosthetic. On the other hand we have the view that automation can and should be used to assist and augment human capabilities, that is it should be used to support and develop peoples innate ethical sense. Unfortunately in this current debate it also looks like the prosthesis school of thought is winning out. My view is that if we continue in this approach of ‘automating out’ moral decision making we will inevitably end up with the amputation of ethical sense in the decision maker, long before killer robots stalk the battlefield, or the high street of your home town.

Waaay back in 2002 Chris Holloway wrote a paper that used a fictional civil court case involving the hazardous failure of software to show that much of the expertise and received wisdom of software engineering was, using the standards of the US federal judiciary, junky and at best opinion based.

Rereading the transcripts of Phillip Koopman, and Michael Barr in the 2013 Toyota spaghetti monster case I am struck both by how little things have changed and how far actual state of the industry can be from state of the practice, let alone state of the art. Life recapitulates art I guess, though not in a good way.

Tweedle Dum and Dee (Image source: Wikipedia Commons)

Revisiting the Knight, Leveson experiments

In the through the looking glass world of high integrity systems, the use of N-version programming is often touted as a means to achieve extremely lower failure rates without extensive V&V, due to the postulated independence of failure in independently developed software. Unfortunately this is hockum, as Knight and Leveson amply demonstrated with their N version experiments, but there may actually be advantages to N versioning, although not quite what the proponents of it originally expected.

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Hazard checklists

06/07/2014

As I had to throw together an example checklist for a course I’m running, here it is. I’ve also given a little bit of a commentary on the use, advantages and disadvantages of checklists as well. Enjoy. 🙂

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The DEF STAN 00-55 monster is back!!

That’s right, moves are afoot to reboot the cancelled UK MOD standard for software safety, DEF STAN 00-55. See the UK SCSC’s Event Diary for an opportunity to meet and greet the writers. They’ll have the standard up for an initial look on-line sometime in July as we well, so stay posted.

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Cleveland street train overrun (Image source: ATSB)

The final ATSB report, sloppy and flawed

The ATSB has released it’s final report into the Cleveland street overrun and it’s disappointing, at least when it comes to how and why a buffer stop that actually materially contributed to an overrun came to be installed at Cleveland street station. I wasn’t greatly impressed by their preliminary report and asked some questions of the ATSB at the time (their response was polite but not terribly forthcoming) so I decided to see what the final report was like before sitting in judgement.

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NASA safety handbook cover

Way, way back in 2011 NASA published the first volume of their planned two volume epic on system safety titled strangely enough “NASA System Safety Handbook Volume 1, System Safety Framework and Concepts for Implementation“, catchy eh?

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Current practices in formal safety argument notation such as Goal Structuring Notation (GSN) or Cause Argument Evidence (CAE) rely on the practical argument model developed by the philosopher Toulmin (1958). Toulmin focused on the justification aspects of arguments rather than the inferential and developed a model of these ‘real world’ argument based on facts, conclusions, warrants, backing and qualifier entities.

Using Toulmin’s model from evidence one can draw a conclusion, as long as it is warranted. Said warrant being possibly supported by additional backing, and possibly contingent upon some qualifying statement. Importantly one of the qualifier elements in practical arguments is what Toulmin called a ‘rebuttal’, that is some form of legitimate constraint that may be placed on the conclusion drawn, we’ll get to why that’s important in a second.

Toulmin Argumentation Example

You see Toulmin developed his model so that one could actually analyse an argument, that is argument in the verb sense of, ‘we are having a safety argument’. Formal safety arguments in safety cases however are inherently advocacy positions, and the rebuttal part of Toulmin’s model finds no part in them. In the noun world of safety cases, argument is used in the sense of, ‘there is the 12 volume safety argument on the shelf’, and if the object is to produce something rather than discuss then there’s no need for a claim and rebuttal pairing is there?

In fact you won’t find an explicit rebuttal form in either GSN or CAE as far as I am aware, it seem that the very ‘idea’ of rebuttal has been pruned from the language of both. Of course it’s hard to express a concept if you don’t have the word for it, nice little example of how language form can control the conversation. Language is power so they say.

 

Well I can’t believe I’m saying this but those happy clappers of the software development world, the proponents of Agile, Scrum and the like might (grits teeth), actually, have a point. At least when it comes to the development of novel software systems in circumstances of uncertainty, and possibly even for high assurance systems.

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For those interested, here’s a draft of the ‘Fundamentals of system safety‘ module from a course that I teach on system safety. Of course if you want the full effect, you’ll just have to come along. 🙂

MH370 Satellite Image (Image source: AMSA)

MH370 and privileging hypotheses

The further away we’ve moved from whatever event that initiated the disappearance of MH370, the less entanglement there is between circumstances and the event, and thus the more difficult it is to make legitimate inferences about what happened. In essence the signal-to-noise ratio decreases exponentially as the causal distance from the event increases, thus the best evidence is that which is intimately entwined with what was going on onboard MH370 and of lesser importance is that evidence obtained at greater distances in time or space.

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Triggered transmission of flight data

Continuing airsearch (Image source: Shen Ling REX)

“Data! Data! Data!” he cried impatiently. “I can’t make bricks without clay.”

If anything teaches us that the modern media is for the most part bat-shit crazy the continuing whirlwind of speculation does so. Even the usually staid Wall Street Journal has got into the act with speculative reports that MH370 may have flown on for hours under the control of persons or persons unknown… sigh.

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After the disappearance of MH370 without trace, I’d point out, again, that just as in the case of the AF447, disaster had either floating black boxes or even just a cheap and cheerful locator buoy been fitted we would at least have something to work with (1). But apparently this is simply not a priority with the FAA or JAA. I’d note that ships have been traditionally fitted with barometrically released beacon transmitters, thereby ensuring that their release from a sinking ship.

Undoubtedly we’ll go through the same regulatory minuet of looking at design concepts provided by one or more of the major equipment suppliers whose designs will, no surprise, also be complex, expensive and painful to retrofit thereby giving the regulator the perfect out to shelve the issue. At least until the next aircraft disappears. Let’s chalk it up as another great example of regulatory blindness, which I’m afraid is cold comfort to the relatives of those onboard MH370.

Notes

1. Depending on the jurisdiction, modern airliners do carry different types and numbers of Emergency Locator Transmitter (ELT) beacons.These are either fixed to the airframe or need to be deployed by the crew, meaning  that in anything other than a perfect crash landing at sea they end up on the bottom with the aircraft. Sonar pingers attached to the ‘black box’ flight data and cockpit voice recorders can provide an underwater signal, but their distance is limited, about a thousand metres slant range or so.

Mars code: JPL and risk based design

Monument to the conquerors of space Moscow (Copyright)

Engineers as the agents of evolution

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Reflecting on learning in the aftermath of disaster

There’s been a lot of ink expended on examinations of the causes of the Challenger disaster, whose anniversary passed quietly by yesterday, but are we really the wiser for it?

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Silver Blaze (Image source: Strand magazine)

Gregory (Scotland Yard detective): “Is there any other point to which you would wish to draw my attention?”
Holmes: “To the curious incident of the dog in the night-time.”
Gregory: “The dog did nothing in the night-time.”
Holmes: “That was the curious incident.”

What you pay attention to dictates what you’ll miss

The point that the great detective was making was that the absence of something was the evidence which the Scotland Yard detective had overlooked. Holmes of course using imagination and intuition did identify that this was in fact the vital clue. Such a plot device works marvelously well because almost all of us, like detective Gregory, fail to recognise that such an absence is actually ‘there’ in a sense, let alone that it’s important.

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I guess we’re all aware of the wave of texting while driving legislation, as well as recent moves in a number of jurisdictions to make the penalties more draconian. And it seems like a reasonable supposition that such legislation would reduce the incidence of accidents doesn’t it?

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Over on Emergent Chaos, there’s a post on the unintended consequences of doling out driving privileges to young drivers in stages.

Interestingly the study is circa 2011 but I’ve seen no reflection in Australia on the uncomfortable fact that the study found, i.e that all we are doing with such schemes is shifting the death rate to an older cohort. Of course all the adults can sit back and congratulate themselves on a job well done, except it simply doesn’t work, and worse yet sucks resources and attention away from searching for more effective remedies.

In essence we’ve done nothing as a society to address teenage driving related deaths, safety theatre of the worst sort…

Toyota ECM (Image source: Barr testimony presentation)Economy of mechanism and fail safe defaults

I’ve just finished reading the testimony of Phil Koopman and Michael Barr given for the Toyota un-commanded acceleration lawsuit. Toyota settled after they were found guilty of acting with reckless disregard, but before the jury came back with their decision on punitive damages, and I’m not surprised.

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A slightly disturbing story of the car manufacturer, it’s software and what happened when that software failed… or at least was presumed to fail.

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Why risk communication is tricky…

An interesting post by Ross Anderson on the problems of risk communication, in the wake of the savage storm that the UK has just experienced. Doubly interesting to compare the UK’s disaster communication during this storm to that of the NSW governments during our recent bushfires.

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One of the perennial issues in regulating the safety of technological systems is how prescriptively one should write the regulations. At one end of the spectrum is a rule based approach, where very specific norms are imposed and at least in theory there is little ambiguity in either their interpretation or application. At the other end you have performance standards, which are much more open-ended, allowing a regulator to make circumstance specific determinations as to whether the standard has been met. Continue Reading…

Fire day

17/10/2013

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Woke to thick smoke in the city today, and things have not improved on what is turning into a bad fire day for us. Our airport at Newcastle is evacuated due to the Hank street fire that’s breached its containment lines and is now burning south east. There’s a fire at Killingworth to the west of the city and grass and scrub fires down the west side of the lake. More than eighty fires state wide, four with emergency warnings and three with watch and waits issued. And the wind is rising…

Command and control

09/10/2013

Titan launch (Image source: USAF)

The human face of nuclear weapons safety

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Provided as part of the QR show bag for the CORE 2012 conference. The irony of a detachable cab being completely unintentional…

Battery post fire (Image source: NTSB)

The NTSB has released it’s interim report on the Boeing 787 JAL battery fire and it appears that Boeing’s initial safety assessment had concluded that the only way in which a battery fire would eventuate was through overcharging. Continue Reading…

Cleveland street train overrun (Image source: ATSB)

The ATSB has released it’s preliminary report of it’s investigation into the Cleveland street overrun accident which I covered in an earlier post, and it makes interesting reading.

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4100 class crew escape pod #0

On the subject of near misses…

Presumably the use of the crew cab as an escape pod was not actually high on the list of design goals for the 4000 and 4100 class locomotives, and thankfully the locomotives involved in the recent derailment at Ambrose were unmanned.

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yellowbook-rail.org.ukThat much beloved safety engineering handbook of the UK rail industry, the Yellow Book, is back. The handbook has been re-released as the International Handbook Engineering Safety Management (iESM).

Re-development is being carried out by Technical Program Delivery Ltd and the original authoring team of Dr Rob Davis, Paul Cheeseman and Bruce Elliot.

As with the original this incarnation is intended to be advisory rather than mandatory, nor does it tie itself to a particular legislative regime.

Volume one of the iESM containing the key processes in 36 pages is now available free of charge from the iESM’s website, enjoy.