Tag: News

Understanding Boeing 787 Avionics

In what I’ve written so far, I’ve taken the humancentric view much as most commentators. The focus of interest being on what the two Air India crew members were doing during the critical moments of this tragic flight. Let’s shift perspective. It’s time to take an aircraft level view.

On the Boeing 787-8 “Dreamliner”, the flight deck has two crew seats and two observer seats. One observer seat is directly behind and between the two crew seats. Since these observer seats are not mentioned in the preliminary report, it’s responsible to assume that they were unoccupied.

In my days working on civil aircraft certification, it was often as a part of a multidisciplinary team. I suppose one of the privileges of working on aircraft avionic systems is that they touch every part of a modern civil aircraft. That meant working with highly experienced specialist in every technical field, including flight test pilots and engineers.

When it came to reviewing aircraft system safety assessments, we’d often put it like this, you look at the aircraft from the inside out and well look at the aircraft from the outside in. Meaning that the flight test team looked at how the aircraft flew and performed. Systems engineering specialists focused on how the aircraft functioned. What was the detailed design, the means and mechanisms. It was by putting these differing perspectives together that a comprehensive review of an aircraft could be established.

Here’s where I need to be careful. Although, I worked on the technical standards1 for complex aircraft systems, I did not work on the Boeing 787 at initial certification.

If I go back 25-years, a major change that was happening with respect to aircraft systems. It was the move to apply Integrated Modular Avionics (IMA). This was a move away from federated systems, where just about every aircraft function had its own box (autopilot, autothrottles, instruments, etc.) There was a fundamental architectural difference between federated and IMA systems.

The Boeing 787 has what is called a Common Core System (CCS). As an analogy let’s think of a time before the smart phone became universal. I had a Nokia mobile phone, a Canon camera, a HP calculator, a Dell lap-top, lots of connectors and pen and paper. Now, the only one that has survived the passage of time is the pen and paper.

So, it is with modern civil aircraft. An Integrated Modular Avionics (IMA) hosts the applications that are necessary for safe flight and landing. The IMA hosts functions that provide, Environmental Control, Electrical, Mechanical, Hydraulic, Auxiliary Power Unit (APU), Cabin Services, Flight Controls, Health Management, Fuel, Payloads, and Propulsion systems.

Information is digitised (sensors, switches and alike), processed and then acted upon. General Processing Modules (GPM) inside the aircraft CCS perform the functions needed. There’s an array of these GPMs and redundancy to provide a high integrity aircraft system.

An aircraft’s Fuel Shutoff Valve Actuator depend on the above working as intended in all foreseeable circumstances. No doubt the accident investigators are undertaking an analysis of the Boeing 787 avionics architecture to gain assurance that it worked as intended.

  1. Standards: EUROCAE started a working group (Number 60) in September 2001, which was tasked to define guidance. Later, in November 2002, there was a merge with an RTCA steering committee (Number 200). ↩︎

Fuel Control Switches

I’ll not go any further than the investigation report that’s in the public domain. The Air India AI171 Boeing 787-800 Preliminary Report is published for all to read. The aircraft’s Enhanced Airborne Flight Recorder (EAFR) has been replayed. Sadly, this report raised questions as much as it closes down erroneous theories.

It warrants saying again, and again. My thoughts are with the friends and families of those affected. They deserve to know exactly what happened and as far as is possible, why. Not only that but the global travelling public need to be confident that any necessary corrective action is being taken to prevent a recurrence of such a rare fatal accident.

What requires a one or two words is one of the commonest ways we interact with electrical and electronic systems. The humble switch. In fact, they are far from humble and come in lots of shapes and sizes. The general idea is that a mechanical device, that can be manipulated with a purpose in mind, is used to control the flow of electrical current. There are non-mechanical switches, but I’ll not go there for the moment.

I remember conversations with my aircraft electrical engineering colleagues. It goes like this – you deal with the small currents (avionic systems), and we will deal with the big ones (power systems). Also, a mantra was that all electrical systems are, in part, mechanical systems. Switches, cables, generators, control valves, relays, bonding, you name it, they are in part, mechanical systems. In the past traditional electrical engineers got a but jittery when faced with “solid state” controls (semiconductors).

Switches. I’ve seen the words “cognitive engagement” used. In simpler terms, by design, pilots interact with switches with a purpose in mind. Equally, as in the world of human factors, unprotected switches can be operated in error, unintentionally or by physical force.

So, what are the chances of two protected Fuel Control Switches moving, within seconds of each other, at the most critical phase of an aircraft’s flight?

[There is a discussion to be had in respect of timing. Remember the record from the flight recorders is a sampling of events. The sampling rate maybe as low as one per second. Note: EASA AMC2 CAT.IDE.A.190.]

These cockpit switches are designed and certificated to perform as intended under specified operating and environmental conditions. That’s a wide range of vibration and temperature (shake and bake).

Switch operation is indicated by their physical position[1]. In addition, operation of these switches will be evident by cockpit indications. The concept being that a flight crew can confirm that the Fuel Control Switches have moved by their effect on the engines. If a crew need to take corrective action it is in relation to the information presented to them by the engine instrument system.

The report makes it clear that both mechanical switches transitioned from ‘RUN’ to ‘CUT-OFF’ almost immediately as the aircraft became airborne. That is a worst-case scenario. The time available to recognise and understand the situation, for training to kick-in, and then to take appropriate corrective action was insufficient.

This leads me to think that there may be a case for disabling the Fuel Control Switch function up until at least an altitude where aircraft recovery is possible. Now, these switches need to be available up until the V1 speed is achieved (Example: aborting a take-off with an engine fire). After that an aircraft is committed to becoming airborne.

I suspect the reason there is no inhibit function is the possibility of adding another potential failure condition. Inadvertent and unrecoverable disabling of ‘CUT-OFF’ are scenarios that would need to be considered. No doubt a reasonableness argument was used. No crew would shut-down both engines down immediately an aircraft became airborne, would they?

POST: I hope I haven’t given the impression that this is a case of simple switches and wires. The Boeing 787 is a digital aircraft.  Mechanical fuel technology plays its part but control functions are digital.

[1] Designs that offer switch illumination are not used in this case.

Insights from AAIB Report on Boeing 787 Accident

Now, we know more about the most tragic aviation accident of recent years. The report by India’s Aircraft Accident Investigation Bureau (AAIB) about the June 12 fatal accident of a Boeing 787 raises new questions.

The careful wording of the preliminary report[1] is eminently sensible. The facts are what they are, but it remains difficult to construct a scenario around these facts. I suspect that all the parties involved in this fatal accident investigation had a hand in ensuring that the words used where as clear as can be at this early stage. As I said, the facts are what they are.

It’s good that the report shuts down some of the fervent and erroneous speculation that was filling the international media. For this accident, fuel supply being the substantive issue, decisions around flying controls and other aircraft performance issues can be put to one side.

The crew encountered, or were responsible for a situation that once established led to one inevitable sad outcome. The time available to react, at such low altitude, was less than that which was needed to continue a safe flight.

A focus at this point is on the Boeing 787 aircraft’s fuel control switches. These switches are installed in the flight deck and used by a pilot to cutoff fuel to the engines. When correctly installed, these fuel control switches have a locking feature to prevent inadvertent operation.

Clearly unintended switch movement between the fuel supply and fuel cutoff positions can be hazardous. Inadvertent operation of one or both switches could result in an unintended consequence, e.g. engine(s) shutdown. What we know is that sufficient fuel was supplied to the aircraft engines to conduct a take-off. Then for some unknown reason that fuel supply did not continue as it should.

So far, the respectable technical speculation I’ve read (pilot and aircraft engineer led), raises a limited number of possibilities.

One being that the crew acted in an inappropriate or inadvertent manner. Another being that the aircraft’s fuel control switches failed or were caused to fail. Another being that aircraft’s fuel control system (including wiring) failed or were caused to fail. The movement of the flight deck switches may or may not have been involved. What we know is that the record on the accident flight recorder shows a condition occurred that should not occur.

There is no doubt that this would have been a highly stressful situation in the cockpit whatever the root cause. Normally, immediately after the aircraft is leaving the runway the pilot-in-command would have no good reason to look at the aircraft’s fuel control switches. They would be looking forward at the aircraft instruments.

We can take it that every aviation authority/agency/administration with a Boeing aircraft on its aircraft register will be closely watching the progress of this accident investigation. Since, to date, no Airworthiness Directive (AD) has been issued, related this fatal accident, it is reasonable to assume that aircraft systems and equipment failure or maintenance error has not been found. That said, it is worth noting FAA Special Airworthiness Information Bulletin (SAIB) No. NM-18-33 dated December 17, 2018.

We cannot rule out the possibility that this fatal accident was intentional. However, in the whole history of civil aviation this is one of the most extreme explanations. Looking at evidence, a situation when a competent and sane pilot is found to choose to act in an irrational manner is hard to diagnose.

POST: Just over 3-years ago, I wrote “The case for video”. That case to update the rules is now stronger than ever. The case for video.

[1] https://aaib.gov.in/

Tariff Turbulence

Tariffs are back in the daily News again. In fact, they never went away it’s just that more attention getting events have been happening. Tariffs were something specialist trade negotiators talked about before this year started. Now, the word is commonplace.

The simple assumption is always made that everyone knows what the word means. Apparently, the origins of the word are Arabic[1]. Linked to information. Now, it’s a fee that someone must pay. The important bit being “must”. In this context it’s about the import and export of goods. The relations between countries.

A presumption made by politicians, who like these bureaucratic instruments, is that they can help protect a nation’s domestic industry from competition from other countries. Thus, tipping the balance away from investments made abroad to those made at home. This chimes with nationalistic instincts.

If only it were as simple. Globalisation is a reality. Kicking against it has its attractive points, if it weren’t for the overall benefits that it has delivered in recent decades. Much of the technology we take for granted is available at low prices because of where and how it’s manufactured.

One advice given out by banks is to avoid knee-jerk reactions. In other words, the ups and downs and on and offs of changing tariff regimes may seem to demand an immediate response. However, it could be wiser to ride out the turbulence of these early months of 2025. To sit back and let the dust settle.

Politically driven efforts to disrupt global trade are likely to impact both importer and exporter. It doesn’t take more than a few minutes walking around a large warehouse store to see goods originating from all over the world. That is quality goods that are offered for sale at astonishingly low prices. It astounds me that I can easily buy a perfectly good basic kitchen microwave for £50.

I hate to say it, but I don’t think there’s anyway whatsoever that a domestic manufacturer could compete with that electrical product’s price and quality even if there was a 100% tariff placed on its import. The story vacuum cleaners is one of designs emanating from Britain but being made in Asia. Globalisation is a reality.

I will make at least one concession. That’s the environmental one. Shipping vast qualities of raw materials and goods around the globe has a real cost. An environmental cost. So, it would be wise, at least, to investigate if domestic production is a viable prospect before automatically assuming an import is better. This is a matter for both industry and public policy.

Not only this point but for some critical products, say steel and semiconductors, there should be a domestic capability even if it’s only aimed at meeting a fraction of the potential demand. Strategic needs are not trivial.

Are tariffs a good way to shift the global balance sheet? To me the answer depends on adopting either a short-term or long-term perspective. Certainly, in the later tariffs are a foolish measure. My recollections come from the history of subsidised industries in the 1970s and the poor products that resulted. It a sorry saga of designed decline. One quick look at the story of the British Leyland Motor Company (BLMC) is a good lesson.

I know for a liberal I sound Thatcherite but competition brings better outcomes than protectionism. That generally depends on a level playing field. Yes, tariffs are a form domestic protectionism and that’s much like a permanent subsidy. Trouble is that permanence is never permanent.

Trump maybe a part-time socialist. If not by word then by action. For the time being the tariff humbug will continue to command attention. In the longer term – I think not. Relearning what has been learnt in the past.

[1] https://blog.collinsdictionary.com/language-lovers/the-fascinating-journey-of-the-word-tariff/

Managing Risk After Aircraft Accidents

Let me clarify. I can no more predict the future than is illustrated in the humour of this news report. “Psychic’s Gloucester show cancelled due to ‘unforeseen circumstances[1]‘”

Predicting the outcome of an aircraft accident investigation is just as fraught with unforeseen circumstances. For a start, the evidence base is shallow in the first weeks of an investigation. As the clock ticks so increasingly, new information either confuses or clarifies the situation.

Despite the uncertainty, aviation professionals do need to try to anticipate the findings of a formal investigation before they are published or communicated in confidence. It’s not acceptable to sit back and wait to be told what has been found.

In aviation, post-accident there is an elevation of operational risk. The trouble is that assessing that elevation is hindered by the paucity of reliable information. Equally, a proliferation of speculation can escalate risk assessments beyond what is needed. The reverse is true too.

Let’s look at the difference between commentary and speculation. One is based on evidence and the other may not be. One takes the best professional assessment and the other may be more to do with beliefs, prejudices or the latest fashionable thinking.

In reality, it’s not quite as binary. Since speculation in the financial sense may be based on a lot of calculation and risk assessment. Generally, though there is an element of a leap of faith. Opinions based upon past experiences commonly shape thinking.

Commentary on the other hand, like sports commentary is describing what’s happening based upon what’s known. Sometimes that includes one or two – what ifs. In football, that match deciding penalty that was only missed but for a small error.

Commentary includes analysis and study of past accidents and incidents. Trying to pick-up on any apparent trends or patterns is of paramount importance.

Those responsible for aircraft operations, whether they be airlines or safety regulators, need to have an immediate response. That maybe done in private. Their decision-makers need to have a theory or conjecture based on as much analysis and evidence as is available. Like it or not, the proliferation of commentary and speculation does have an impact.

In a past life, one of the actions that my team and I took was to compile a “red book” as quickly as possible post-accident. That document would contain as much reliable information as was available. Facts like aircraft registration details, a type description, people, places and organisation details that were verifiable. This was not a full explanation. It was an analysis, compilation and commentary on what had happened. The idea being that decision-makers had the best possible chance of acting in a consistent manner to reduce risk in the here and now.

[1] https://www.gloucestershirelive.co.uk/whats-on/whats-on-news/psychics-gloucester-show-cancelled-due-7250094

Impact of Speculation

The sadness of the loss of live and the suffering of air crash victims’ families, must be respected. On 12th June, Air India’s London Gatwick bound flight AI171 crashed after take-off from Ahmedabad airport. Only one passenger walked away from this catastrophe. Additionally, there were fatalities on the ground as the Boeing 787 aircraft came down in a built-up area.

My heartfelt condolences to those connected with this tragic fatal accident.

The technical accident investigation is well underway. In time, a probable cause for this accident will be determined. This will be published and available to all. As per the international arrangements of ICAO Annex 13 a report will be published. Organisations, with appropriate expertise, will carefully sift through the evidence to establish a sequence of events. This is not a matter of establishing blame. It’s a process of determining what happened with the aim of preventing it from happening again.

Meanwhile, the widespread reporting of the accident can only offer speculation as to the details of who, what, where, when and how and why. There are facts. The time, place and the people involved. Media interviews, with whatever pictures and video recording there are dominate the public domain. However, this is far from the volume of information the accident investigators will handle. They will have access to every nut and bolt, every document, every recording.

After another aircraft accident, back in August last year I wrote: Speculation is a natural human response. When faced with a paucity of information we often put together what we know and then make a best guess as to what happened or what might happen. However, wise or unwise it’s not possible to stop speculation.

In the case of flight AI171 the global media speculation has been, and is, of a new order of magnitude. Normally, the authorities caution against giving too much weight to early conjecture. This is prudent in that the obvious is often not as obvious as it might first seem. Accident investigation can be like putting the pieces of a complex jigsaw together. Deliberately and with great care.

What has been surprising in this case is the intensity of the speculation related to this accident both through traditional and social media. The proliferation of experts offering opinions has reached a new high. Until conflict and war grabbed the headlines everyday a novel theory, or a variation of a theory has been offered. Each one chasing credibility and expanding on limited sources.

Let’s not be pious. I’m not immune from this need to fill a void. My own reasonably well-informed theories float around in my head, but I question my senses in sharing them with others. It’s not a fear of being wrong, as I might be, no, more a fear of cluttering up a confusing mass of information to an even greater extent. Piling theories on top of theories.

Can we have too much of “experts” offering their opinions? Some will be trustworthy and considered, and others will not. How far is it reasonable to stretch what little is known into detailed stories of possible cause and effect?

How is the average person going to tell the difference between sound reasoning and imaginative nonsense? This problem was brought home to me in a recent conversation. When a newspaper revelation is told to me as a “fact” when I know it isn’t, then I see the dangers in excessive speculation.

This may not matter so much to me. In so far as it affects me. However, to an air crash victims’ family this not considerate. To be led to thinking that the cause of an accident is generally known, when it isn’t, that’s disrespectful. It’s the downside of speculation. Not something that is ever going to stop, it’s true. What some keyboard warriors need to think about is the impact of their wild guesses or prejudices.

POST 1: Even reputable publishers latch on to theories that are at best well intentioned and at worse just flying a kite. Air India crash: Early speculation points to possible dual-engine failure | Engineering and Technology Magazine

POST 2: To be fair this YouTube commentator does a good job at making it clear what is fact and what is not https://youtu.be/dIgnR0zw3FU

Enhancing Transport Safety

There’re claims that Artificial Intelligence (AI) will make transport safer. It’s to put a positive spin on the introduction of AI. Implying that existing safety deficiencies can be addressed with the power of AI.

It’s difficult to disagree with this simple assertion. There’s a list of risks that continue to be troubling. With directed design effort there are functions that AI can perform that mean it can have an advantage over conventional systems. With good design, no doubt high performing systems can be constructed.

In aviation, for example, if I consider the top five fatality risks, there’s a persistence of specific categories. We never seem to get away from loss of control in-flight (LOC-I) being high on that grim list. Runway related issues persist, and the hardy perennial of mid-air collision remains. Over the years progress has been made addressing controlled flight into terrain (CFIT), but that category of destructive events never disappears.

It’s fascinating to see that the industry thinks that AI itself is a risk[1]. High probability but low impact. This is considering a broad description of risk rather than a safety focus. Here the concern is related to the difficulties of practical implementation of this new technology.

Marketing people will big up the possibilities brought about by AI. This is what’s going on in relation to the most recent mid-air collision fatal accident. With sound justification given how crude elements of air traffic management are in specific locations.

We will never entirely displace “see and avoid” as a means of collision avoidance. Scanning the horizon looking for other air users. In my opinion, relying on this technique in relatively busy traffic areas is unwise, to say the least. This is where airborne AI assistants have much operational safety potential. Sucking up multiple information sources and processing masses of information to give accurate and instant advice. Such systems can be designed to give real-time updates not only to improve situation awareness but give avoiding action guidance, or even automated responses.

Let’s get back to the general assertion that AI will make aviation safer. On this one I’d be more cautious. For example, looking at LOC-I incidents and accidents there’s a complex mix of causal factors, and circumstantial factors. In addition, there’s the complexity of potential recovery actions too. Solving problems in 4-dimentions whatever the weather, whatever any damage incurred and however pilots react. This is where the probability numbers start to stack up.

That catch all disciplines “human factors” makes outcomes particularly difficult to calculate. Accidents are known where pilots and automation fight each other to produce bad outcomes.

AI is a machine. It will speedily crunch numbers in a mechanical manner. An extremely advanced manner but without emotion or, yet, not matching the imaginative capabilities of the human brain. Or for that matter the sophistication of human senses.

Would exceptional capable AI have saved Swissair Flight 111[2], for example? Sadly, I think not. On the day, likely an automated airborne system would have made the same decisions as the pilots. Decision making without the sense of precisely how the aircraft fire was developing would still have been hamstrung. I could raise other cases too.

Will AI make transport safer. In part. Not as a universal cure all.

[1] https://www.iata.org/en/publications/economics/reports/risks-2025-brief/

[2] https://www.bst-tsb.gc.ca/eng/rapports-reports/aviation/1998/a98h0003/a98h0003.html

Challenges to Liberty

We live in interesting times. Conflict and turbulence, shifting political loyalties, and rapid technology advances. What a mix.

I don’t want to say – twas ever so. That’s a resignation. To say that challenges and tragedies are of exceptional magnitude in any one era. Since forecasting is such a fragile art, better or worse maybe just around the corner.

What’s unique is our societal expectations. Whereas a serf in a feudal country had little hope of a better life. Today, our higher expectations come from generations of struggle having improved the circumstance of the individual and our communities. Improvements in standards of living, economic, social, environmental, are maintained by an adherence to the “rule of law”. However, imperfect that might be.

The basic stuff still matters. English liberties, in great part, stem from the Magna Carta of 1215[1]. It may have not been immediately successful, as Monarchs and Popes quickly tried to kill it. What’s amazing is that its core content has echoed down the centuries.

Democratic societies have taken on rights, human rights, in their simplest essence. Each of us expects a day in court. A means to defend ourselves from the exercise of arbitrary power.

Yes, for hundreds of years English Monarchs continued to assert what they claimed to be God given powers. Until that came to a head. Literally so. The English Civil War set the rights of the citizen against the arbitrary power of a King.

Where I am now there are signs of that past conflict. In fact, I can see one of from my kitchen window. Surrounded by trees, on the brow of a hill, overlooking a fast-flowing river, is the remains of a castle. Most of Donnington Castle[2] was destroyed but the gate house tower remains. The winning side, Parliament ordered its destruction.

You can understand why I get nervous when politicians assert that they are on a mission from God. Centuries of conflict have bought a citizen’s protections from arbitrary power. To see it return under the guise of personal ambition and careless action is sad.

Yes, there are lots of undemocratic places in the world where this does not apply. Even so, with all its imperfections, English liberty did spread far and wide. It made its way across the Atlantic Ocean. Constitutional practices maybe different but common law prevails.

I hope democratic societies will emerge stronger from this turbulent period. Shifting sand is everywhere. Values are being assailed. Nevertheless, there’s every good reason to believe that a strengthening of our society is possible. A progressive vision offers so much more than a backside into a dark past.

[1] https://www.magnacartatrust.org/

[2] https://www.battlefieldstrust.com/resource-centre/battleview.asp?BattleFieldId=89

Evolution Politics

Wake up John. The herald of today was there in the late 1990s. There was me fascinated by the possibilities of the INTERNET. Buzzing modem squeaking down a phone line. With such peculiarities as Y2K behind us the new century provided broadband access to everyone. Almost everyone. Eventually, being off grid became a sales tag for remote rural settings.

Meanwhile, good old-fashioned popular entertainment media was desperately trying to make itself relevant to the new era. Proliferation of reruns were not enough. Stale formats dwindled. In that maelstrom, reality television was born. Technology shaped what became possible. It was a horror to me but then again, I was just out of touch.

Big Brother is a strange beast. Watching joe average or minor celebrities make complete fools of themselves for big bucks – how could that work? It did, bigtime. Undeniably scoring with the public. It spawned lots of similar shows bombarding us with unscripted chat seen through the tight lens of an edited television show.

Not quite like throwing Christians to the lions, familiar to Romans, but a social experiment open to participants combative as much as caring behaviour. Watching relatable and unrelatable volunteers try their best to seem nice or nasty as they thought appealing.

25-years on, now British politics begins to resemble reality television. That creation provided a pathway through our screens to capture our attention. To make names out of relatively unknowns. Or to revive careers waning.

I said “begins to resemble” without realising that I’m being a dinosaur. It’s here. A politician can’t anymore stand on a soap box and pontificate about the world. The grand ark of a well written speech is destined for the dustbin. Every presentation needs to be framed as if they are in the jungle (I’m a Celebrity…Get Me Out of Here![1]).

Reality shows are becoming a training ground for political personalities. Forget the serious need to do an apprenticeship. That one has been hijacked too. The basic grind of administration and casework can be bypassed if the candidate is a good enough showman or woman.

Going back to the 1990s, I think a lot of us were naive about the coming technologies. There was an imagining of the information superhighway[2] as a great educator. A positive liberator. A forum for better communication. Making it easier for people to have a real dialogue with the elected officials. Thus, solving problems, cutting down bureaucracy and engaging communities.  

Of course it is those things. The naivety came with the blindness to the huge entertainment possibilities. How reality and make-believe can get intermingled. How dominant personalities would capture the cameras like Hollywood stars.

With that fuzziness between reality and make-believe storytelling takes on a new importance. That’s what political managers have discovered in abundance. Medium and message have always been closely linked. Now, a would-be star or demigod must take that ever more seriously to win.

[1] https://www.itv.com/imacelebrity

[2] https://www.bbc.co.uk/videos/czv20818q2no

Probabilistic Predictions

Uncertainty is the only certainty. Not a radical statement. As long as I live, dealing with uncertainty is inevitable. Unavoidable everywhere. I wouldn’t have it any other way, even if it can be uncomfortable.

Prominent Ancient Greeks may have travelled to Delphi for advice as to what the future may hold. There’re those three enigmatic witches who warn Macbeth of his fate. History and fiction are littered with references.

For me, I can pick-up a newspaper and look for a daily astrological prediction. One I like. I can flick around social media and see more prophecies than ever. Mostly gibberish. There are those convinced of their foresight.

Despite a cynical disposition towards the above, science can be applied to the world of uncertainty. Generally, the proposition is that an element of the past and present will be reproduced in the future. This is not absolute. However, human engineered systems tend to behave with a degree of predictability.

Empirical methods, where society collects data from the past and present, can be useful in trying to forecast what may happen next. The more deterministic the systems under study, the more useful acquired data can be. For these, forecasting challenges mount for the new, novel, or radically altered.

I’m writing this given the interest there is in probabilistic safety. There are figures that hit the headlines that are almost incompressible. If the rationale behind the numbers is not clear then incorrect assumptions result. Tiny numbers from 1 x 10-6 to 1 x 10-9 are quoted in the News (SI Units). What do they mean? Let’s start with simple probability.

If an occurrence is certain then a numerical value of “1” can be given to it.

Absolute certainty is a rare thing. I can say that the Sun will rise tomorrow, and most people will take that as a statement of certainty. Intriguingly there’s the most incredibly improbable case where the solar system is thrown into instability and the Sunrise isn’t as expected.

If an occurrence never happens then a numerical value of “0” can be given to it.

Absolute impossibility is only possible with absolute knowledge. So, again it’s rare. I can say that human time-travel, to and from the distant past, is only fiction to next discover that a way has been found.

Let’s say we live in a world where the probability of occurrences ranges from the 0.99999, with ever more “9s”, to a number as small as 1 x 10-30[1]. A quecto.

These extreme numbers are nice for physicists and astronomers to play with, but they are outside normal engineering practices. As yet, we do not have the means to operate at the level of these limits. Time will tell. Or I maybe wrong.

By the way, I used the word “occurrence” above to denote anything that can happen in an instant. When talking about undesirable happenings, that can mean an incident, accident, mishap, slip, failure, or error. Each of these has a definition. Often more than one.

Next. I’ll go back to the tiny numbers more commonly quoted.

POST: For extraordinary numbers we need look no further than the nimble electron. So far, the best measurement for the life of an electron suggests that one now will still be around in 66,000 yottayears (6.6 × 1028 yrs). That’s about 5-quintillion times the current age of our universe. 

[1] https://www.nist.gov/pml/owm/metric-si-prefixes