Flying – Page 2 – John Vincent

Shifting Perspectives

Daily writing prompt

What’s a topic or issue about which you’ve changed your mind?

If you write the perfect rule, you will get the desired outcome. Authoring a specification that is robust and watertight will assure success. Having the best possible plan will deliver the best possible results. All sounds reasonable – doesn’t it? It’s not surprising that someone like me, having been schooled in project management, and working in engineering, would have a rational and systematic approach to problem solving. A proven highly successful way of implementing complex technical projects and delivering successful outcomes.

As an analogy I’ll start with mathematics. Nature is a curious beast. What we lean about complex systems is that what happens is highly dependent upon a start point. The initial conditions. Graduate level mathematics about control systems with feedback show that their behaviour changes a lot with a change of initial conditions. So, it’s reasonable to extend that to a systematic approach to just about anything. It’s often true.

Fail to plan – plan to fail. That idiom is a simple few words to sum up this cause and effect. Used by famous names and often quoted. Management training books are littered with this notion.

20-years ago, my team introduced the first European Aviation Safety Plan[1]. This initiative was built around the idea that to achieve a common objective a plan is the best and quickest way to get there. A roadmap, a pathway, a strategy, call it what you will.

Start by identifying problems and then propose a fix for each one. Not all problems but the ones that fit that awkward Americanism – the low hanging fruit. Namely, the biggest problems (fruit) that can be solved with the least effort (easily picked).

Here’s where I’ve changed your mind. Maybe not changed in a dramatic sense but shifted perspective. It’s essential to have a plan, even if it’s just in my head, but it can be overstated as the most important part of a process of change.

The Plan, Do, Check, and Act (PDCA) cycle, starts with a plan. It must start that way. However, each of the four steps is equally important. Seems obvious to say. Even so, it’s often the case that a press release, or alike, will state – we have a plan, roadmap, pathway, strategy, as if that’s the job done.

Management teams will smile with a sense of achievement and show off their plans. A decade down the line that celebration might seem less momentous as the “do” part of the process turns out to be harder than anticipated.

This basic model for systematic change is a good one. Where I’ve changed my emphasis is in the distribution of effort. Don’t put all available energies into constructing the perfect plan. Yes, the initial conditions are important but they are not everything. The key part of the process is the cycle. Going around it with regularity is a way of delivering continuous improvement. Afterall, when it comes to a subject like aviation safety, that’s what’s needed.

[1] 2005 – DECISION OF THE MANAGEMENT BOARD ADOPTING THE 2006 WORK PROGRAMME OF THE EUROPEAN AVIATION SAFETY AGENCY

Regulatory Insights

I can’t remember if my teacher was talking about maths or physics. His scholarly advice has stuck with me. When things get complex, they can seem overwhelming. Problems seem insolvable. So, it’s good to take a deep breath, step back and see if it’s possible to reduce the problem to its most basic elements. Do what could be called helicopter behaviour. Try to look at the problem top-down, in its simplest form. Break it into parts to see if each part is more easily comprehended.

Today’s international aviation regulatory structure, for design and production, follows the arrow of time. From birth to death. Every commercial aircraft that there ever was started as a set of ideas, progressed to a prototype and, if successful, entered service to have a life in the air.

This elementary aircraft life cycle is embedded in standards as well as aviation rules. Documents like, ARP4754(), Aerospace Recommended Practice (ARP) Guidelines for Development of Civil Aircraft and Systems are constructed in this manner. There are as many graphs and curves that represent the aircraft life cycle as there are views on the subject, but they all have common themes.

That said, the end-of-life scenarios for aircraft of all kinds is often haphazard. Those like the Douglas DC-3 go on almost without end. Fascinatingly, this week, I read of an Airbus A321neo being scrapped after only 6-years of operations. Parts being more valuable than the aircraft.

Generally, flight-time lives in operational service are getting shorter. The pace of technology is such that advances offer commercial and environmental advantages that cannot be resisted. Operating conditions change, business models change and innovation speeds forward.

My earlier proposition was that our traditional aviation regulatory structure is out of date. Well, the detail is ever evolving – it’s true. Some of the fundamentals remain. The arrow of time, however fast the wheels spin, mixing my metaphors, remains an immobile reality.

In airworthiness terms an aircraft life cycle is divided into two halves. Initial airworthiness and continuing airworthiness. This provides for a gate keeper. A design does not advance into operational service, along the aircraft life cycle, until specified standards have been demonstrated as met. An authority has deemed that acceptable standards are met.

I’m arguing, this part of the aviation regulatory structure is far from out of date. However much there’s talk of so called “self-regulation” by industry it has not come into being for commercial aviation. I think there’s good reason for retaining the role that a capable independent authority plays in the system. A gate keeper is there to ensure that the public interest is served. That means safety, security and environmental considerations are given appropriate priority.

To fulfil these basic objectives there’s a need for oversight. That is the transparency needed to ensure confidence is maintained not just for a day but for the whole aircraft life cycle. And so, the case for both design and production approvals remain solid. The devil being in the detail.

Why 12,500 Pounds?

Regulation is a strange business. It often means drawing lines between A and B. Bit like map making. Those lines on a map that mark out where you are and the features of the landscape. You could say that’s when all our troubles start but it’s been proven unavoidable. As soon as our vocabulary extends to words like “big” and “small” someone somewhere is going to ask for a definition. What do you mean? Explain.

For a while you may be able to get away with saying; well, it’s obvious. That works when it is obvious for all to see. An alpine mountain is bigger than a molehill. When you get to the region where it’s not clear if a large hill is a small mountain, or not then discussion gets interesting. Some say 1000 ft (about 300 m) others say much more. There’s no one universal definition.

[This week, I drove through the Brecon Beacons. Not big mountains but treeless mountains, nevertheless. Fine on a clear day but when it rains that’s a different story. This week Wales looked at its best].

Aviation progressed by both evolution and revolution. Undeniably because of the risks involved it’s a highly regulated sector of activity. Not only that but people are rightly sensitive about objects flying over their heads.

For reasons that I will not go into, I’ve been looking at one of these lines on a regulatory map. One that’s been around for a long time.

I cannot tell you how many discussions about what’s “minor” and what’s “major” that have taken place. That’s in terms of an aircraft modification. However, these terms are well documented. Digging out and crewing over the background material and rationale is not too difficult, if you are deeply interested in the subject.

The subject I’m thinking about is that difference between what is considered in the rules to be a “large” aeroplane and a “small” aeroplane. Or for any American readers – airplane. So, I set off to do some quick research about where the figure of weight limit: maximum take-off weight of 12,500 pounds or less originated for small airplanes (aeroplanes).

I expected someone to comment; that’s obvious. The figure came from this or that historic document and has stuck ever since. It seems to work, most of the time. A confirmation or dismissal that I wanted addressed the question, is the longstanding folklore story is true. That the airplane weight limit was chosen in the early 1950s because it’s half the weight of one of the most popular commercial transport aircraft of that time.

There is no doubt that the Douglas DC-3[1] is an astonishing airplane. It started flying in 1935 and there are versions of it still flying. Rugged and reliable, this elegant metal monoplane is the star of Hollywood movies as well as having been the mainstay of the early air transport system is the US. Celebrations are in order. This year is the 90th anniversary of the Douglas DC-3[2].

What I’ve discovered, so far, is that the simple story may be true. Interestingly the rational for the weight figure has more to do with economic regulation than it has with airplane airworthiness. The early commercial air transport system was highly regulated by the State in matters both economic and safety. Managing competition was a bureaucratic process. Routes needed approval. Thus, a distinction established between what was commercial air transport and what was not.

POST 1: There is no mention of 12,500 pounds in the excellent reference on the early days of civil aviation in the US. Commercial Air Transportation. John H. Frederick PhD. 1947 Revised Edition. Published by Richard D. Irwin Inc. Chicago.

POST 2: The small aircraft definition of 12,500 pounds max certificated take-off weight first appears in US CAB SPECIAL CIVIL AIR REGULATION. Effective February 20, 1952. AUTHORIZATION FOR AIR TAXI OPERATORS TO CONDUCT OPERATIONS UNDER THE PROVISIONS OF PART 42 OF THE CIVIL AIR REGULATIONS. This was a subject of economic regulation in the creation of the air taxi class of operations.

[1] https://airandspace.si.edu/collection-objects/douglas-dc-3/nasm_A19530075000

[2] https://www.eaa.org/airventure/eaa-airventure-news-and-multimedia/eaa-airventure-news/2025-07-17_dc3_society_celebrate_90_years_douglas_dc3_airventure25

Aircraft Safety and Fuel Starvation

Unsafe. In common language it’s the opposite to being safe. So, take a definition of “safe” and reverse it. Let’s say to be safe is to be free from harm (not a good definition). That would lead to “unsafe” being subject to harm or potentially being subject to harm. The probabilistic element always creeps in since it’s the future that is of concern. Absolute safety is as mercurial or unreal as absolute certainty.

Let’s apply this to an aircraft. The ultimate harm is that of a catastrophic event from which there is no escape. Surprisingly, taking a high-level view, there are few of these situations that can occur.

Flying, and continuing to fly, involves four forces. Lift, Weight, Thrust and Drag. It’s that simple. An aircraft moves through the air with these in balance. Flying straight and level, lift opposes weight and thrust opposes drag.

Yes, there are other safety considerations. If there are people on-board. For example, it’s important to maintain a habitable environment. At higher altitudes that requirement can be demanding. Structural integrity is important too. Otherwise flying is a short-lived experience.

In the recent Air India fatal accident, the four forces of flight were not maintained so as to make a continued safe flight possible. The wings provided lift but the force that was deficient was thrust.

Two large powerful engines, either of which could have provided enough thrust, were unable to do so. The trouble being fuel starvation. Fuel starvation occurs when the fuel supply to the engine(s) is interrupted. This can happen even when there is useable fuel on board an aircraft[1].

Sadly, in the records there are numerous aircraft incidents and accidents where this has happened. Quite a few fuel starvation incidents and accidents occur because of fuel mismanagement. This can result from a pilot selecting an incorrect, or empty, fuel tank during a flight.

Now and then, it is the aircraft systems that are at fault. The pilot(s) can be misled by a faulty fuel indication system[2]. In one notable case, a major fuel leak drained the aircraft’s fuel supply[3].

When there is useable fuel on-board an aircraft, the imperative is to restart and recover. It is not uncommon or unreasonable for there to be a delay in restarting engine(s), especially when a fuel starvation event is entirely unexpected. Diagnosis takes time given the numerous potential causes of a starvation event.

In cruise flight there is time available to perform a diagnosis and take appropriate corrective action. Both take-off and landing have their hazards. Both are busy times in the cockpit. When looking at the worldwide safety numbers, less fatal accidents occur on take-off than landing. The numbers Boeing provide put take-off at 6% and landing at 24% of fatal accidents. Each one only occupies about 1% of the total flight time.

Although these are the numbers, my view is that, even though take-offs are optional and landings are mandatory, the requirements for adequate thrust are most critical during take-off. This is arguable and it reminds me that safety assessment is never simple.

[1] https://www.faa.gov/lessons_learned/transport_airplane/accidents/G-YMMM

[2] https://asn.flightsafety.org/asndb/322358

[3] https://asn.flightsafety.org/asndb/323244

Causal Chains in Accidents

It becomes apparent to me that there’s much commonplace thinking about accidents. What I mean by this is that there’s simple mental models of how events happen that we all share. These simple models are often not all that helpful. Commonplace in that journalists and commentators use them as a default. It’s a way of communicating.

Don’t worry I’m not going on a tirade of how complex the world happens to be, with a dig in the ribs for anyone who tries to oversimplify it. We need simple mental models. Answering questions and explaining as if everything is an academic paper doesn’t help most of us.

I talk of no less than the causal chain. That’s a love of putting the details of events into a chronological sequence. For an aviation accident it might go like this – fuel gets contaminated, fuel is loaded onto aircraft, engine stops, pilot makes an emergency landing, aircraft ends up in a field and an investigation starts. The headline is dominated by the scariest part of the sequence of events. Key words like “emergency” are going to command the readers attention.

In my example above it’s reasonable to assume that there’s a relationship between each link in the chain. The sequence seems obvious. It’s easy to assume that’s the way the situation developed and thus made the accident or incident. However, it doesn’t have to be so. Let’s say there was contaminated fuel but not sufficient to stop an engine. Let’s say for entirely unrelated reasons (past events) the spluttering of the engine led the pilot to think that there was a fire on-board. Fuel was shut down. Thus, events took a different sequence.

Anyway, my point is an ancient maximum. Question what you first hear (or see). The recent tragic fatal accident in India is an example of much speculation often based on a proposed orderly sequence of events. Many commentators have lined them up as, this happened, and then that happened and then something else happened. QED.

What I’ve learned from reading and analysing accident reports over the years is that such major accidents are rarely, if ever, a simple sequence or only a couple of factors combined.

Yes, adding circumstantial factors to a causal chain adds realism. Even that is not so easy given that each factor has a different potential influence on the outcome. Atypical circumstantial factors are time of day or night, weather, atmosphere conditions and the human and organisational cultural ones.

To make sense of the need to put events in an order a more sophisticated model is the fishbone diagram[1]. The basic theme is the same. A core causal chain. What’s better is the injection of multiple factors to make a more authentic accident model.

Although, we do think in a cause-and-effect way about the world, if there are more than 4 or 5 factors combined in a random manner these models are far from authentic. My message is not so sophisticated, beware of simple sequences as being definitive.

[1] https://asq.org/quality-resources/fishbone

The Intriguing Life of Jackdaws

As the grass turns brown, the sun beats down. Me, I just a lawnmower[1]. Now, that’s probably the daftest lyric that has ever been written in the history of rock. As I look out of the window at the parched grass there’s no way I’d take my lawnmower to it. If I did there would be nothing, but dirt left in its wake. Stubborn deep-rooted weeds and dead moss.

It’s summer. It’s unusually dry. Although, as the sun came up this morning, looking out of the bedroom window, a thin mist covered the ground. That was early. Between 4am and 5am. A thin white mist, low to the ground, must refresh the grass just a little. Most of nature sleeps.

As the morning progresses its not long before one dominant sound fills the air. It’s not the cars on the nearby road. One species of bird has adopted the tall trees, field next door and my garden. They are not a quite bird. To those that know their call is instantly recognisable. Their sound isn’t musical like some birds. It’s an incessant chatter. Loud and repetitious.

Jackdaws are having no trouble despite the dying grass and rock-hard ground. Our community of noisy birds is thriving. I guess their advantage is that they eat just about anything that’s going. Not much concern about predators as they take no care to hide their presence. I’ve seen them happily mocking larger birds. Showing off seems to make them happy.

As far as evolution goes, they have a lot of advantages. Equally agile hopping around on the ground as they are swooping and diving from tall trees. There’s no doubt they have a complex social etiquette. One or two minutes watching how they interact gives this away. Bigger, more mature, birds intimidate the younger ones.

Can’t say I like them much. More that I admire them for being so savvy. Jackdaws look as if they own the place. It’s not my garden. They are saying, we come a go as we please, you can share the space if you like. Sooty black masters of the airspace.

We’ll tolerate each other mainly because we have no other choice. Trying to scare a jackdaw is a fruitless task. They learn quickly. Soon sussing out that they can get the better of you.

As the sun beats down, I lay on my lounger. Listening to the endless chatter. Me, I’m just a bird feeder. Watching as the skies fill with shiny black dots. There for moment and gone the next.

[1] https://genius.com/Genesis-i-know-what-i-like-in-your-wardrobe-lyrics

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 12^th 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

Technology and Probability

Everyday numbers don’t scare me. The day, the date, the time are important and simply communicated. I can throw a couple of round numbers at anyone, and they should know what’s happening. Yes, convention does matter. Standards matter. I don’t know how, but I know some people struggle with the 24-hour clock notation.

When we get to small scales and tiny numbers, less familiarity means that it’s not so easy to communicate. To make those numbers meaningful media people like to use analogies. A common one is saying that a thing is: less than the width of a human hair. If you still have it, and I do, hair is an everyday item.

Let’s say a human hair is typically 100,000 nanometres wide. Sounds big in nanometres. That’s a tenth of a millimetre. Now, I can get a plastic ruler and visualise that size. My perception of scale depends on where I put the decimal point. Remember in SI Units a “nano” is 1 x 10^-9[1]. Something to think about when seeing newspaper headlines about nanotechnology.

Visual depictions do help. Even if they can be slightly misleading when comparing dissimilar objects. Our planet, Earth is about 12,756 kilometres in diameter. So, for a bit of fun I could say the Earth is about 128 x 10⁹ times wider than a hair on my head. Nice but not so useful. Tiny probability numbers like the range from 1 x 10^-6 to 1 x 10^-9 require some imagination.

It’s not such a big leap. Let’s say that I make mistakes. That said, I’m well trained at a specific simple task. Flicking a switch at the right time. My measured error rate is about 1 in 100. However hard I try, I make mistakes, not necessarily the same one, but with a reasonably quantifiable average frequency when nothing changes.

A well-designed machine, doing the same mechanical task, can do better than me. It’s measured error (or failure) rate is about 1 in 10,000. That might be considered good if it’s merely to switch on a toaster at precisely 6 am. It might not be so good if the result of a single mistake is instant death. In other words, I’ve become highly dependent on this mythical machine.

To do better, I could devise a means of checking the results of this machine. If I did this checking perfectly, entirely independently and without distraction, then experiencing a negative result might get up to a rate of one in a million. With this arrangement, I’m still not happy enough to place my life, or the lives of my colleagues in the hands of such a system.

Instead, I’ll construct two entirely independent well-designed machines, each doing the same simple task and each constantly checking the other one. Now, I’m cooking on gas, as the expression goes. Will this result in a negative outcome rate of around 1 in 1 x 10⁸? One in a ten million. At least it’s an analysis worth doing. However, calculations may not give the result as one in a ten million. That result can hinge on the notion of what is entirely “independent”.

To make my general point here I have grossly oversimplified a problem. What I hope I have conveyed is that tiny probability numbers can be grasped without entertaining rocket science or nuclear physics. In the world of computational systems, we can make machines that are exceptionally good at performing consistently, persistently and error free. Not perfect. Not at all. Not prefect in so much as making life and death decisions.

[1] https://www.nano.gov/about-nanotechnology/just-how-small-is-nano

Avoiding Contrails and Enhancing Operations

Here I’m expanding on my earlier words on aircraft Contrails.

Airspace is a busy place. It’s most busy over Europe and the US. Over the oceans there’s more room, although on certain routes, like the North Atlantic, there’s plenty of daily air traffic.

Those who manage the airspace are primarily concerned with ensuring that aircraft collisions do not occur. The impact of mid-air collisions is devastating. There’re few people in aviation who can forget the events of an evening in July 2002. Over Überlingen, Germany[1], 71 people lost their lives at a time when the sky was not busy at all.

Managing the use of airspace is more than collision avoidance. Flying is perpetually concerned with the weather. What’s it doing, how is it changing and is it a hazard? It’s not just the safety of flying that demands up-to-date meteorological information. Knowing about the winds can enable more efficient operations, and that’s less fuel use for a given route.

Large thunderstorms need to be avoided. Regions of the world (example: intertropical convergence zone) make this a dynamic challenge. Manoeuvres may be planned but flight crews must be ready to act based on the information they have, like weather radar.

Turbulence is another phenomenon to be avoided, if possible. This can occur in clear air. It can be difficult to detect. Which explains the unpleasant examples that hit the News now and then[2].

Back in 2010, aviation had a reminder that avoidance encompassed any hazardous airspace. That was when an unpronounceable volcano in Iceland was spewing out ash at high altitudes. Plumes of volcanic ash, if ingested into aircraft engines, can cause major difficulties.

I’ve written these words to emphasise that the avoidance of contrail formation cannot be done as a stand-along consideration. It becomes one factor in a whole mix of factors.

Avoidance of contrail formation is about considering the mechanism that cause them to form. Clearly, the warmer the air is the harder it is for a contrail to form. The more humidity there is in the air, the easier it is for a contrail to form. Outside Air Temperature (OAT) and atmospheric humidity vary at each altitude. That relationship interacts with the aircraft inflight, and the outcome may be different for each aircraft type.

At least one academic study[3] says that adjustments of aircraft altitude of around 2000 ft could have a useful effect on contrail formation. That’s good to know but let’s not forget that Reduced Vertical Separation Minima (RVSM) [4] means a vertical spacing of 1000 ft in busy airspace.

My take on this fascinating subject is that there both a tactical and operational approach that can be practically taken by aviation.

At the tactical level, airlines can factor contrail avoidance into flight planning. Creating an algorithm that will weigh all the relevant flight factors. Improved sources of accurate and timely meteorological data and predictions will be needed.

At the operational level, it’s down to the flight crews to take advantage of environmental conditions as the opportunity arises. Much as dealing with turbulence, that is when safety and operational rules permit. To change altitude when its beneficial, computational help is likely to be needed. Over the ocean, air-ground communications systems may need to be further improved. An altitude change that avoids contrail formation but increases fuel consumption would not be a sustainable solution.

These computational tasks may well be well suited to machine learning. A useful application of artificial intelligence. I can imagine a cockpit weather radar display with a new set of symbology that indicates a low probability contrail formation zone ahead.

[Back in the 1990s, I worked on RVSM when the ARINC organisation was creating international standards. Safely increasing traffic in the North Atlantic region. Additionally, I participated in the certification of Future Air Navigation System (FANS) 1/A for use over the ocean. FANS led to more efficient aircraft operation due to shorter flying times and decreased fuel burn.]

POST: Looks like data crunching is underway Flight plans, but greener: The ICCT and Google’s mission to refine the Travel Impact Model – International Council on Clean Transportation

[1] https://www.bfu-web.de/EN/Publications/FinalReports/2002/Report_02_AX001-1-2_Ueberlingen_Report.pdf?__blob=publicationFile&v=1

[2] https://www.flightglobal.com/safety/turkish-777-rapidly-descended-during-crews-aggressive-response-to-turbulence-encounter/162937.article

[3] https://www.imperial.ac.uk/news/195294/small-altitude-changes-could-contrail-impact/

[4] https://skybrary.aero/articles/reduced-vertical-separation-minima-rvsm