Category: Flying

Understanding Contrails

Crisscrossing the sky, as I look up on a clear day, there are civil aircraft going about their business. People travelling across the Atlantic or coming back or on a day trip to Glasgow.

These shiny pinpoints of light in motion, set against a blue sky, are all the more visible because of the vapour trails they leave behind. Aircraft speed through the rarified atmosphere to leave a momentary trail as evidence of their presence.

Up with the aircraft in flight are natural clouds. Up at 30,000 feet there can be Cirrus clouds[1]. There might not be much air pressure at that altitude but there’s enough moisture to support cloud formation. The word “wispy” sums them up.

Aircraft create condensation trails that are known as contrails. How the English language likes to shorten. They are not mysterious or generate with evil intent in mind. It’s simple physics.

In my bathroom, with hot water gushing from the shower, moisture is the air. When that moist air meets a cold surface, like a window, condensation is sure to be seen. Airbourne it’s not so different. Hot emissions from powerful jet engines shooting out into a cold low-pressure environment and guess what?

Typically, contrails don’t last long. If there’s appreciable wind at high altitude, then they get dispersed quickly. Not only that but the icy temperatures up there soon return things to the status-quo. There are days, when the air is still, that the sky can become a crisscross of contrails where dispersion is more like a gentle merging.

The theory goes that the cumulative impact of lots of high-altitude flying is like the impact of additional cloud formation. It’s water vapour after all. It’s known, high altitude clouds can contribute to the greenhouse effect.

The point I’m getting to here is that lots of flying contributes to climate change. Primarily because of the burning of significant amounts of fossil fuel. As a secondary consideration there’s the issue of contrails across the globe.

This leads to the question – can their formation be avoided? Even, is there something useful to be gained in doing so. Trials and research are trying to establish the answer to these questions[2].

Initially, contrail avoidance sounds like it should be relatively easy to do. However, like so many good proposals it’s not so easy. Change needs to involve air traffic management, flight operations and international regulators.

First the atmospheric conditions need to be detected or predicted in a given location and then an avoidance needs to be planned and undertaken in coordination with everyone flying at high altitude at a given time. Lost of data to crunch.

It’s possible, in oceanic airspace, a dynamic aircraft system could perform this avoidance function. It would be an interesting design challenge for an avionics company to take up.

#Net Zero #SustainableAviation

[1] https://weather.metoffice.gov.uk/learn-about/weather/types-of-weather/clouds/high-clouds/cirrus

[2] https://news.aa.com/esg/climate-change/contrail-avoidance/

Sustainable Aviation: Innovations and Challenges

Gas guzzling continues to be one of aviation’s problems. Combustion remains that the heart of most aircraft power plants. Taking large amounts of fossil fuel. Squeezing energy out of every drop of gasoline. Gobbling up more day after day. Pushing out emissions.

As I look out across the garden, I see gliding effortlessly as the warm air rises, a Red Kite[1] gracefully circling. Wings outstretched they hardly move them as they climb. They’re a distinctive small bird of prey, easily spotted because of their forked tail. Now, that’s what I call efficient flying. Using all that nature provides and wasting little energy.

Human attempts at flying are a million miles behind these magnificent birds. There’s still so much to learn about aerial navigation. It’s a matter of control. The sensing of ambient conditions and the precision movements needed to ascend and dive at will.

The search is on for effective change. There’s no pretence that the way commercial aviation operates is unsustainable. It’s true that the gas guzzlers of the air guzzle less gas now than they ever have but the physical facts remain.

None of this is new. I’m about to send a book called “Towards Sustainable Aviation” to a charity shop. It’s not that there’s anything wrong with it. The book is full of pertinent analysis and observations. Trouble is that it’s dated 2003.

I’m led to ask – what’s changed in over 20-years? In answering my own question – quite a lot but not enough. Discourse has moved on from academic quarters to the political sphere. Aircraft have become more fuel efficient. Driven by economic imperatives as much as any concern for the climate. Research initiatives are generously funded to come up with answers. Solutions like hydrogen, electric propulsion, and SAF (sustainable aviation fuel) are slowly moving from theory to practice. A few prototypes are flying. Limited supplies of SAF are flowing.

Unmistakable that’s where the problem lies. For all the hype, policy and government funding the pathway to genuinely sustainable aviation disappears way off into the horizon. There are setbacks too. Gas guzzling is back in fashion. Certainly, in Trump’s America.

We could make a much more of the technology that’s currently available. Yes, there are costs involved. Change is not a free ride. That said, sticking with the status-quo isn’t free either. Legacy costs mount up. One reason why older jets disappeared from fleets so quickly.

The next generation of commercial aircraft must make major steps forward. Since the life of a typical aircraft type can easily extend to 30-years, then change must happen in design now.

Typically, commercial aviation moves with graduated change. There’s an inherent conservatism in the system, as might be expected when safety and security are paramount. Facing this global challenge, there’s a need for a degree more radicalism.

Since high impact disruption is also in fashion, it’s time for airlines and manufacturers to adopt a pioneering spirt. It’s been done before. In the 1960s, that pioneering spirt gave us the Boeing 747, the Jumbo jet. That opened flying to a whole generation.

[1] https://www.rspb.org.uk/birds-and-wildlife/red-kite

Travel’s Societal Impact

Privilege is all around us. It’s, by definition, not equality. It’s a privilege to live in a country not torn by war or where the environment has not been decimated. It’s a privilege to be able to protest and strongly disagree with the powers that be. Indeed, in this country it’s a right too.

Debates about the moral or ethical grounds of inequality will never cease. That’s a hope of mine. For the minute we become timid and cowed by an authority that would rather supress such debates, then that’s the end of our democracy. We’d be free no more.

A large part of my career has been in the aviation industry, in one way or another. Putting aside the military uses of aviation, that’s another debate, civil aviation and the travel industry are two peas in a pod. Flying facilitates travel. Largely international travel. Apologies to the cargo industry, leisure flying and so many others.

One phenomenon that is not new, is that of raising the issue of responsibility. For example, the consequences of tourism to natural environments are often negative. Not always so. Huge effort is made by some countries and organisations to make tourism a positive. However, generally there are significant challenges to be grappled with in making travel affordable for all.

Wealthy young Europeans have been roving across boarders as part of a rite of passage since the 1600s. A “Grand Tour” was a form of discovery, education and cultural enrichment. Today, a student might call that a gap-year. Time taken out of formal studies to travel abroad. The aim, as well as having fun, is to return a more rounded person ready for whatever life might throw up.

Where do we sit as a society in terms of the balance between personal freedom and our collective responsibilities? Are activists right to attempt to slam or shame travellers for the negative impacts that they can trigger? These are uncomfortable questions. Ironically, these difficult questions are often raised by the people who have enjoyed the privilege of travel.

In my mind, a debate on this subject of balance reflects greater societal issues. When we look at a basic hierarchy of human needs then international leisure travel may not be top priority. However, life would be less rich and colourful without it. Embarking on an epic journey, that takes a traveller outside their comfort zone, can be a life changing event.

To defend the freedom to travel, I cannot avoid looking at the other side of the equation. There is an overwhelming responsibility to do something restorative. Ignoring the impact of travel, particularly civil aviation, is not an option anymore.

I know there are some politicians who scream for the abandonment of Net Zero policies and all they entail, but they are extremely foolish. Shifting the burden onto future generations is reckless. Appealing to those who want to escape the debate, or force a return to mythical age, is nothing more than doomed short-termism.

This is one reason I’m an advocate for electrification and the exportation of radical solutions, like hydrogen powered civil aviation. Technological solutions are part of the path to take. That, in of itself, may not be enough but at least engineering change is permanent.

Solutions by design are far more powerful than ephemeral political posturing. Legislation can be overturned in a weekend. A whole new way of operating aviation can be sustained for decades.

Communication Prevents Disasters

It’s often forgotten that there’s a need to repeat messages. We are not creatures that retain everything we see and hear. There are exceptional people, it’s true, those who cram away facts and have an amazing level of recall. Often that’s my reaction to watching students leading teams on University Challenge[1]. How on earth do they know those obscure facts?

Most of us do not respond well to those who say, “Well, I told them once. I’m not going to tell them again.” That line is probably one of the most misguided utterances a teacher can make. Like it or not, this approach is part of our heritage. Past ages, when deference was expected, listening was mandatory, and misremembering was entirely the listener’s fault.

We’ve had a cultural shift. Our complex technological society doesn’t work in a command-and-control way. Too many disasters can be traced to miscommunications and misunderstanding. Now, the obligation exists on those delivering a message to go some way to ensure that it’s received with a degree of comprehension. That’s when repetition has a role to play.

One of the pillars of Safety Management Systems (SMS) is Safety Promotion. It’s the Cinderella of the aviation safety world.

Why do I say that? Experience for one. It’s much easier to get policy made and funding for the “hard” sciences like data acquisition, analysis and decision-making systems. These are often perceived as providing tangible results. Actionable recommendations that satisfy the need to be recognised as doing something. Even if that something is questionable.

Communication is key to averting disasters. It’s no good having pertinent information and failing to do anything with it, other than file it. The need to know is not a narrow one. Confined to a specialist few.

Let’s go back to 2003 and the Space Shuttle Columbia accident[2]. This craft was destroyed in a disaster that claimed the lives of its crew. The resulting investigation report is extremely compressive, if slightly overwhelming, but it has some key points to make.

To quote, “That silence was not merely a failure of safety, but a failure of the entire organization.” [Page 192]. In other words, the hidden concerns and internal machinations of an organisation can smother safety messages and led to failure. Since 2003, it’s sad to say that there are multiple occasions when what has been learned has been ignored. The impact has been devastating.

So, to shape the future let’s remember the Cinderella of the aviation safety. Discovering problems is not enough. It’s vital that practical solutions and good practice gets promoted. That needs to be done forcefully and repetitiously.

NOTE: This is, in part, a reaction to watching this video presentation. https://acsf.aero/an-unforgettable-closing-to-the-2025-acsf-safety-symposium-with-tim-and-sheri-lilley/

[1] https://www.bbc.co.uk/programmes/b006t6l0

[2] https://ntrs.nasa.gov/api/citations/20030066167/downloads/20030066167.pdf

My First US Adventure

Let’s wind the clock back. My first trip to the US. It was a big adventure. One that I’d recommend to anyone in their 20s. The trip was a Pam Am fly-drive affair. A travel package that took me and three friends from London Heathrow to Seattle and back. In 1981, I had no idea that I’d be returning to Seattle numerous times in the following decade.

I keep a personal flight logbook. It’s a simple way of keeping track of the dates, times and places. Memory can be unreliable. When 40 years or more has past recollections of individual trips get jumbled up. Although this one is difficult for me to mistake.

We took off in the afternoon and flew across the Atlantic on flight PA 123. Slightly being in awe of the mighty Boeing 747-100. It was the largest aircraft doing that route on a regular basis.

Sadly, the Lockerbie bombing occurred 7-years later to a similar transatlantic Pan Am flight. The airline that brought the Boeing 747 to life didn’t survive after that tragic event.

One of the advantages of being a sandwich student was the ability to earn. To put some money away. To have the funds to plan an exploration like this trip without depending on the bank of mum and dad. To keep the costs down the four of us shared a car, the driving and the motel rooms along the way. In fact, we had a detailed itinerary that didn’t leave much slack time at all. Our travel planning was meticulous. I’d even arranged to visit an offshoot of the Plessey company in the Los Angeles suburbs. It was a real eyeopener. A maker of precision metals for the aerospace industry.

We arrived in Washington State only a year after the deadliest volcanic eruption[1] in US history. Naturally, being the students we were, we drove as close to the devastated area as the open roads would let us. I took pictures of that too. Views of forests felled like matchsticks.

We packed an enormous amount into August 1981. Returning to our final year as soon as we got back. This trip always reminds me that if you plan well and are determined enough you can do a hell of a lot in a short time. We drove over 6000 miles and took in a lot of the West Coast.

[1] The Mount St. Helens major eruption of May 18, 1980.

Tragic Helicopter Crash

The record of sightseeing helicopters is not a good one. In the most recent case 6 people perished as helicopter crashed into the Hudson River in New York City. It’s with a heavy heart that I offer my condolences to the family and friends of those involved. These are devastating events for all concerned.

It’s certainly far to early to say why this helicopter fell from the sky. Eyewitness reports suggest a catastrophic occurrence. Also, that the helicopter tumbled and hit the water inverted. Again, suggesting an occurrence where the pilot had no opportunity to avoid the outcome.

Initially, the indications are that the local weather was not a significant factor in the accident. Also, reports are that no other aircraft was involved. In this fatal accident the US National Transportation Safety Board (NTSB) will be on the scene as they manage the technical investigation. They have already published initial information.

Given the size and nature of operations there will be no Flight Data Recorder (FDR) installed on this helicopter. There is a strong argument for requiring light weight flight recorders on small helicopters. It will be interesting to read of what electronics are recovered from the accident site. Images from a mobile phone may be most useful to the investigators.

The helicopter’s maintenance records will be reviewed for indications of mechanical problems. However, it is highly unusual for a complete rotor system to fall apart in flight. Mechanical failures often have some precursors that give an indication that all is not well.

The list of Bell 206 type helicopter accidents and incidents is long[1]. That’s not an indicator of their relative safety. This is a popular single engine small helicopter with a long history. Both civil and in other variants, military. First flight dates to 1966. It’s going back a while, but I clearly remember a sightseeing flight I took on such a helicopter back in the 1980s.

This type of small helicopter is often operated in difficult conditions. They have the advantage of being highly maneuverable. However, there are maneuvers that can case serious problems. The term “mast bumping” was used by the US Army[2]. In the worst cases this results in catastrophic occurrences.

One of the factors in such accidents and incidents is a significant change in the helicopter’s center of gravity and an inappropriate response to that condition.

POST 2: Pictures of the recovery of the rotor system from the river suggest structural failure. It’s as if the rotating mechanical parts ripped themselves from the body of the helicopter. Bell 206 L-4 helicopter crash, Jersey City, New Jersey (April 10, 2025) | Flickr

POST 1: Social media is littered with theories, as per usual. One seems highly unlikely. Namely, fuel exhaustion. Another, concerning a strike of a flock of birds over the river is worth investigation. In that possible case evidence will surely be easily uncovered.

[1] https://asn.flightsafety.org/wikibase/495847

[2] https://youtu.be/_QkOpH2e6tM?si=AtMfqztc_cjrUOSm

Safety Analysis

In discussions about safety one model is often called up. Its simplicity has given it longevity. It also nicely relates to common human experience. The model is not one of those abstract ideas that take a while to understand. If you have been on a safety training course, a lecturer will give it couple of minutes and then use it to draw conclusions as to why we collect and value safety data.

On illustration, and it’s a good one for sticking in the memory, is a picture of a big iceberg. Most of an iceberg is underwater. One the surface we only see a fraction of what is there. This is the Heinrich pyramid. Or Heinrich’s Law[1] but it’s not really a law in the sense of a complete mathematical law.

The logic goes like this. In discissions about industrial major accidents, there are generally a lot more minor accidents that precede the major ones. Although this was drawn up in the 1930s the model has been used ever since. And we extend its useful applicability to transport operations as much as workplace accidents.

Intuitively the model seems to fit everyday events. Just imagine an electrical cable carelessly extended over the floor of a hanger. It’s a trip hazard. Most of the time the trips that occur will be minor, annoying events, but every so often someone will trip and incur a major injury.

What we can argue about is the number of precursor events that may occur and their severity. It wouldn’t be a simple universal ratio, either. Heinrich said there were generally about 30 accidents that cause minor injuries but 300 accidents with no injuries. A ten to one ratio.

Forget the numbers. The general idea is that of the iceberg illustration. Underlying that example of the pyramid is the notion that there are a lot more low severity events that occur before the big event happens. Also, that those low severity events may not be seen or counted.

It’s by attempting to see and count those lesser events that we may have the opportunity to learn. By learning it then becomes possible to put measures in place to avoid the occurrence of the most destructive events.

In British aviation I will reference the 1972 Staines air accident[2]. A Brussels-bound aircraft took off from London Heathrow. It crashed moments later killing those onboard. One of the findings from this fatal aircraft accident was that opportunities to learn from previous lesser events were not taken. Events not seen or counted.

Thus, Mandatory Occurrence Reporting[3] was born. Collecting data on lesser events became a way of, at least having a chance of, anticipating what could happen next. Looking at the parts of the iceberg sitting under the water.

How many fatal accidents have been prevented because of the safety analysis of data collected under MOR schemes? If only it was possible to say.

[1] https://skybrary.aero/articles/heinrich-pyramid

[2] https://www.bbc.co.uk/news/uk-england-surrey-61822837

[3] https://www.caa.co.uk/our-work/make-a-report-or-complaint/report-something/mor/occurrence-reporting/

From Prescription to Performance-Based Regulation

One regulatory development that has stuck since the start of the new century is the idea that we need to transition from prescriptive requirements to performance-based requirements. It’s not too hard to understand where the motivation to change has come from but there are several strands to the path. Here’s three that come to mind.

For one, the intense dislike of overbearing governmental regulators who adopt an almost parental attitude towards industry. It’s true that safety regulatory bodies have a duty to serve the public interest. The difficulty arises in interpreting that brief. Not as police officers sometimes did, imagining everyone as a potential miscreant.

My experience as a regulator started at a time when traditional institutional approach was quite common. There was a respectful distance between the airworthiness surveyor or operations inspector and the aviation industry that they oversaw. I think, even the term “surveyor” was one inherited from the insurance industry at the birth of flying.

A wave of liberalisation swept into the 1980s. It was an anathema to those who started their careers as men from the Ministry. The idea that regulators should be in a partnership with industry to meet common goals was not easily accepted. Undoubtably a change was necessary and, naturally, easier for an up-and-coming generation.

The next move away from regulatory prescription came as its value declined. That is, not that there will not always be an element of prescription by matter of the written law. However, for detailed technical considerations it became less and less practical to say, this is the way it must be. The minute decision-makers were faced with the complexity of a microprocessor it become clear that it’s not effective to simply prescribe solutions.

Much of the changes that took place can be traced to the evolution of system safety assessment and the use of probabilistic methods in aviation. In mechanics, prescribing a safety guard for a chain drive is straightforward. For complex electronics saying when a flight system is safe enough requires a different approach. Regulators are now driven to set objective rather than dictate solutions.

My third point is a future looking one. Whatever the history and heritage of aeronautical innovation, it’s true that a “conservative” but rapid adoption of new technology continues to be a source of success. Great safety success as well as commercial success.

Hidden amongst the successes are products, and ways of working that don’t meet the grade. The joke goes something like this: “How can I make a fortune in aviation?” Answer: “Just start with a big one.” Implicit in this observation is a wiliness to innovate at risk. That means, amongst many things, having confidence, adaptability and not be so constrained as to be assured failure. An objective or performance-based approach to safety regulation opens opportunity to innovate more freely whilst still protecting the public interest in safety.

There’s no fixed destination for regulatory development.

1985 to 2025 Trends

On reading J. C. Chaplin’s paper on the first 100-years of aviation safety regulation in the UK[1], it struck me that the journey from the 1910s to the 2010s was one of constant change. That change has not slowed down. In fact, the last 40-years of my aviation career have seen dramatic technological changes that have demanded ever new regulatory methods and practices.  

Overwhelmingly aviation history writings obsess about the early days of flying or the start of the jet age. It’s as if those periods were so dominated by great pioneers that nothing worthy has happened since. I exaggerate for effect, but I think you get the meaning of my comment.

So, what of the race from the 1985 to the 2025? I think that is useful period to look at. One of the reasons is that those years are mark the transition from an analogue era to a digital one.

The early 1980s saw experimentation with the potential for digital technologies, most particularly fly-by-wire systems. Quickly the military understood the increase in aircraft performance that could be gained by use of such technologies. Groundbreaking was Concorde in that it demonstrated that critical electronic control systems could safely go into everyday operation. That project drove the development of new regulatory methods and practices. 

A turning point occurred in the mid-1980s. That silicon revolution that impacted so much of life was dramatically put to use in civil aviation. Computing power had so miniaturised and become affordable so that past theoretical possibilities could now be practically realised.

The Airbus A320 aircraft first flew in 1987. It was a shaky start. Not everyone was convinced that safety critical systems were indeed safe. The not so obvious discovery that the human factor was even more important for a computerised aircraft. Learning to adapt and adjust ways of operating didn’t happen overnight.

The lesson is that learning lessons must be part of the process. Through applying continuous improvement, the Airbus A320 family has grown ever since.

Maybe there needs to be a short paper to cover civil aviation safety regulation from 1985 to 2025. It’s needed now. It’s needed because the next 40-years are going to see equally dramatic changes. In the time to come the main driver will be the environment.

[1] https://www.aerosociety.com/media/4858/safety-regulation-the-first-100-years.pdf

The Revolutionary Role of Hydrogen

Hydrogen has a history with aviation. What could be better. A gas that is so light. So easily produced and with no need heat it up. With a lightweight gas-tight bag and a fair amount of rope, balloon construction took-off. Literally. The proof that hydrogen gas could lift a balloon goes back to the 1780s in France.

Sadly, the downside of this gaseous element is its propensity to combine with other elements. In fact, where would we be without liquid water. On this planet, that most basic and prolific combination of hydrogen and oxygen. Not so much sadly but more luckily.

Step forward about 250 years and we have a different vision for hydrogen in aviation. If it’s combined with the oxygen in the air that we breath, we get nothing more noxious than water. Since, the other forms of combustion, that populate our everyday lives, is distinctly noxious, surely hydrogen has a lot to offer. Talk about downsides. Burning fossil fuels is distinctly unsustainable. Polluting the atmosphere.

This week, I was looking out to sea. At the English Channel (No name changes there, I see). Standing on the pebble beach at Budleigh Salterton. They ought to have an award just for that name. It’s a small seaside town in Devon. The towns cliffs are part of a World Heritage Site, namely The Jurassic Coast[1]. 

Forget the 250 years of humans flying, cited above. About 185 million years of the Earth’s history is for all to see on the Devon and Dorset coast. When we say “fossil fuels” what we mean is that we are living off the back of Earth’s history. Society powers modern life on dinosaur juice. Well, not exactly but plant and animal life from hundreds of millions of years ago. How crazy is that?

Hydrogen, on the other hand, is one of the most abundant elements. It’s everywhere.

Modern day dinosaurs (politicians and pundits) insist that we continue to exploit dinosaur juice until it’s all gone. That’s putting aside any concerns about returning all that carbon to the Earth’s atmosphere. Carbon accumulated over millions of years.

Hydrogen can be a clean fuel. The problem is that saying that and then doing it are two different things. There are complexities that come with using Hydrogen as a fuel. It might be reasonably easy to produce, in multiple different ways, but it’s not so easy to transport.

Producing leak proof systems for transport and storage requires innovative thinking. We can’t just treat it with the familiarity of conventional fuels. Whole new regimes are going to be needed to get Hydrogen from where it’s produced to where it’s needed.

Producing leak proof systems for aircraft is a challenge. Given the odourless and invisible nature of this light gas, accurate and extensive detection systems are going to be needed. If the gas is to be consumed by fuel cells to produce electricity, then there’s going to be a constant struggle against complexity and significant expenditures.

What is reassuring is that none of the above is insolvable. At this time in history, we have the materials technology and control systems that make Hydrogen a viable clean fuel.

[1] https://jurassiccoast.org/