Comms

The long history of data communications between air and ground has had numerous stops and starts. It’s not new to use digital communications while flying around the globe. That said, it has not been cheap, and traditional systems have evolved only slowly. If we think Controller Pilot Data Link Communications (CPDLC)[1] is quite whizzy. It’s not. It belongs to a Windows 95 generation. Clunky messages and limited applications.

The sluggishness of adoption of digital communications in commercial aviation has been for several reasons. For one, standardised, certified, and maintainable systems and equipment have been expensive. It’s not just the purchase and installation but the connection charges that mount-up.

Unsurprisingly, aircraft operators have moved cautiously unless they can identify an income stream to be developed from airborne communication. That’s one reason why the passengers accessing the internet from their seats can have better connections than the two-crew in the cockpit.

Larger nations’ military flyers don’t have a problem spending money on airborne networking. For them it’s an integral part of being able to operate effectively. In the civil world, each part of the aviation system must make an economic contribution or be essential to safety to make the cut.

The regulatory material applicable to Airborne Communications, Navigation and Surveillance (CS-ACNS)[2] can be found in publications coming from the aviation authorities. This material has the purpose of ensuring a high level of safety and aircraft interoperability. Much of this generally applicable material has evolved slowly over the last 30-years.

Now, it’s good to ask – is this collection of legacy aviation system going to be changed by the new technologies that are rapidly coming on-stream this year? Or are the current mandatory equipage requirements likely to stay the same but be greatly enhanced by cheaper, faster, and lower latency digital connections?

This year, Starlink[3] is offering high-speed, in-flight internet connections with global connectivity. This company is not the only one developing Low Earth Orbit (LEO)[4] satellite communications. There are technical questions to be asked in respect of safety, performance, and interoperability but it’s a good bet that these new services will very capable and what’s more, not so expensive[5].

It’s time for airborne communications to step into the internet age.

NOTE: The author was a part of the EUROCAE/RTCA Special Committee 169 that created Minimum Operational Performance Standards for ATC Two-Way Data Link Communications back in the 1990s.

POST 1: Elon Musk’s Starlink Internet Service Coming to US Airlines; Free WiFi (businessinsider.com)

POST 2: With the mandate of VDLM2 we evolve at the pace of a snail. Internet Protocol (IP) Data Link may not be suitable for all uses but there’s a lot more that can be done.


[1] https://skybrary.aero/articles/controller-pilot-data-link-communications-cpdlc

[2] https://www.easa.europa.eu/en/document-library/easy-access-rules/easy-access-rules-airborne-communications-navigation-and

[3] https://www.starlink.com/

[4] https://www.esa.int/ESA_Multimedia/Images/2020/03/Low_Earth_orbit

[5] https://arstechnica.com/information-technology/2022/10/starlink-unveils-airplane-service-musk-says-its-like-using-internet-at-home/

High ALT

Normal commercial air traffic control doesn’t go beyond 60,000 ft in altitude. That makes sense since civil flying activities have been limited to lower altitudes. In fact, modern commercial airliners are not designed to fly above about 45,000 feet. This is a compromise based on what works commercially as much as what’s works best. Aircraft instruments are calibrated making standard assumption about the atmosphere.

For some of its flight, Concorde cruised at a height of 60,000 feet. More like a military jet, with its speed it had the capability to make use of higher altitudes.

It’s even possible to fly above 50,000 feet without an engine. The world record glider flight by AIRBUS shows it’s possible.

The Earth’s atmosphere is not uniform. It changes its characteristics with altitude. The atmosphere can be divided into five layers, as the temperature and density change. They are named: Troposphere, Stratosphere Mesosphere, Ionosphere and Exosphere. 

The Troposphere is a layer that goes from 8 kms (26,247 ft) on the poles to about 18 kms (59,055 ft) on the equator. This is the layer where weather is experienced.

On average, the Stratosphere goes up to about 40 kms (131,234 ft). The winds blows fast but they tend to be more consistent as they wrap around the globe. The lower portion of the Stratosphere is virtually isothermal (layer of constant temperature). 

A medieval English philosopher and Franciscan friar, Roger Bacon[1] figured out that the air might support a ship in the same way that water supports ships. In the 13th Century that was a nice academic conclusion but little more.

With all the current controversy surrounding high altitude balloons, that the road to flight started with balloons, could be said to be a bit ironic. It’s long been known about that balloons fly well at high altitudes but it’s a new frontier as far as commercial activity is concerned. For science, weather balloons may go up to 40 km to measure the high level winds.

Some experimental work has been done on trying to commercially use the airspace above normally civil flying. The Google Loon trials[2] are an example of an attempt to float a telecommunications platform high in the sky. These balloon trials were abandoned as difficulties proved greater than anticipated.

It’s not so easy to keep a high altitue balloon on-station.

Now, considering the news in North America, maybe high-altitude operations ought to be a matter of regulatory concern. This is not a subject that any one country can address alone.

There is some legal, regulatory and technical work[3] underway in Europe[4] but it needs to make progress. This is a subject for international collaboration. 


[1] https://en.wikipedia.org/wiki/Roger_Bacon

[2] https://blog.x.company/loons-final-flight-e9d699123a96

[3] https://www.eurocontrol.int/article/echo-making-space-new-high-altitude-entrants

[4] https://www.eurocontrol.int/events/european-higher-airspace-operations-symposium

UFO

It’s intriguing. Reports of unidentified flying objects being shot down over Alaska, Canada, and Michigan prompts a lot of questions.

The Earth’s atmosphere eventually becomes space at 100 km up. The Kármán line[1] is one way to define the boundary. All aeronautic activities are deemed to take place below that imaginary line. Theodore Karman[2] did his best to determine a height at which the Earth’s atmosphere is too thin to support flight. Now, there’s an international discussion about bringing that boundary down to 80 km. That is the hight above which a person in a space vehicle is said to become an astronaut.

I guess my point is that there’s a lot of the Earth’s atmosphere to continuously monitor, if the task is to know about everything that is flying everywhere. So, it’s perfectly reasonable that reports of unidentified flying objects will crop up, now and then.

It doesn’t mean that there are alien probes popping in to keep an eye on us earthlings. No, in so far as is commonly known there’s no evidence that stands up to scrutiny to definitively prove the existence of sustained airborne craft that are not of this Earth. However, extra-terrestrial objects fall to Earth all the time. Mostly ice and rocks. I wrote about objects falling from the sky in an earlier article.

It’s worth recalling the first article of the Chicago Convention on Sovereignty:  

The contracting States recognize that every State has complete and exclusive sovereignty over the airspace above its territory.

For those monitoring what’s in the air, the primary concern remains about flights over land and populated areas. This is the case where hazards can exist to those below.

All said and done, it’s no time to become alarmed. It may well be the case that these unidentified flying objects were previously ignored. Only now has the militaries in North America been galvanised into action and being more vigilant. The more people look, the more people see.

What do I know? Spy balloon, craft and drones may be much more common than has been generally reported.

Claims and counter claims that everyone is doing it shouldn’t be dismissed out of hand. The technology involved in flying above normal air traffic has a multitude of potential applications. A framework for higher altitude operations is now being written[1].

POST: Diplomatic tensions between the US and China continue to escalate as the US explains its shooting down of high altitude flying objects over North America. Much is still to be uncovered.


[1] https://www.eurocontrol.int/article/echo-making-space-new-high-altitude-entrants


[1] https://www.fai.org/news/statement-about-karman-line

[2] A Hungarian American physicist and engineer who was born 11 May 1881.

Fatal accident in Nepal 2

We are now one week from the fatal accident that occurred on Sunday, 15 January in Nepal. Yeti Airlines Flight 691, an ATR 72-500 aircraft, crashed while on approach at Pokhara International Airport in Nepal

We are now one week from the fatal accident that occurred on Sunday, 15 January in Nepal. Yeti Airlines Flight 691, an ATR 72-500 aircraft, crashed while on approach at Pokhara International Airport in Nepal[1]. Sadly, this accident resulted in 72 fatalities. No one survived. Only one body remains to be discovered[2].

This has been Nepal’s deadliest aviation accident in over 30 years.

After years of pandemic-caused travel disruption this land locked nation was hopeful that their new airport would bring the tourists back. The nation’s second-largest city sits in the shadows of a towering mountain range. It’s a picture postcode setting for this tragedy.

Nepal’s government has set-up a five-member committee to investigate the accident.

As stated in the International Civil Aviation Organisation (ICAO) Annex 13, Aircraft Accident, and Incident Investigation[3], it’s the responsibility of the State of Occurrence to lead an investigation. The objective of that investigation should be prevention of future accidents and incidents. It’s not the purpose of a technical activity to apportion blame or liability.

Nepal is the State of Registry and the State of the Operator, but they must notify the State of Design, the State of Manufacture (France) of the aircraft and ICAO in Montreal.

There are numerous speculations concerning the cause of this accident. The scant evidence available on social media does suggest that this aircraft accident fits into the category of Loss of Control in Flight. However, that suggestion is purely informed conjecture at this time.

I agree with David Learmount[4] in that it’s likely that this will be found to be a preventable accident. That said, once the accident flight recorders have been replayed there should be a substantially better indication of what really happened on that fateful day.

Whereas it was previously reported the accident recoders were going to France it’s now reported that they are going to Singapotre for replay Black boxes from Nepal plane crash to be sent to Singapore – ABC News (go.com)

Based on the experience of the analysis of numerous accidents it’s unlikely to be a simple single cause. Such fatal aircraft accidents are often combinations of factors that come together. Approach to a new airport plus an unexpected event or error plus aspects of organisational culture can be enough to tip the balance.

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

A quote of Captain A. G. Lamplugh, British Aviation Insurance Group, London. c. early 1930’s. This famous phrase has been reproduced on posters many times.

POST: Here’s some examples of what can happen again and again. Lessons learned from business aviation accidents maybe equally applicable to this case. Lessons Learned from Business Aviation Accidents | NBAA – National Business Aviation Association


[1] https://aviation-safety.net/database/record.php?id=20230115-0

[2] https://www.thehindu.com/news/international/nepal-plane-crash-search-continues-for-lone-missing-person/article66415303.ece

[3] https://store.icao.int/en/annexes/annex-13

[4] https://davidlearmount.com/2023/01/21/regional-airline-safety-really-doesnt-have-to-be-this-bad/

Still learning leasons

Mobility has transformed society. By land, by sea or by air the world we see around us has been shaped by the technology that has enabled us to move people, goods, and services. Aviation, the youngest means of everyday transport, has radically transformed society in just over a century.

Demand for air transport is linked to economic development and at the same time air transport is a driver in an economy. Nearly all States work to encourage the growth of aviation in one form or another. All States acknowledge the need for the stringent regulation of activities in their airspace.

4.5 billion people moved around the globe by air. Well, that is until the COVID pandemic struck[1]. Even so, there’s an expectation that global air traffic levels will start to exceed those of 2019 when we start to get into 2025 and beyond.

One quote, among many, sums up the reason for the safety regulation of flying, and it is:

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

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

Here the emphasis is on aviation safety and security as the top considerations. In fact, ask an airline CEO of the number one priority of their business and that’s likely how they will answer, if on the record. Much of that open expression will be sincere but additionally it’s linked to the need to maintain public confidence in the air transport system.

We need to remember that aviation had a shaky start. Those magnificent men, and women in their flying machines were adventurous spirits and born risk takers. That is calculated risk takers. Few of them lasted long unless they mastered both the skill and science of flying.

In the post war era, improvements in aviation safety have been dramatic. As the number of hours flown and the complexity of aircraft has grown so has the level of flight safety. Aviation has been an uncompromising learning machine. A partnership between States and industry.

Sadly, in part, the framework of international regulation we may now take for granted has been developed because of lessons learned from accidents and incidents, many of which were fatal.


[1] https://www.icao.int/sustainability/Documents/COVID-19/ICAO_Coronavirus_Econ_Impact.pdf

Fatal accident in Nepal

My condolences to all those people who have been affected by the catastrophic aircraft accident in Nepal. On-board the ATR 72 aircraft operated by Nepal’s Yeti Airlines were 72 people – 4 crew members and 68 passengers.

The aircraft took off from Kathmandu at 10:33 (local time) on Sunday. At around 11:00, while on approach to the airport the twin-engine ATR 72 crashed into a riverbed gorge located between the former airport (VNPK) and new international airport (VNPR). Nepal’s Civil Aviation Authority said the aircraft last contacted the airport at 10:50. There are no reports of distress calls from the aircraft before the accident.

As only a short time has elapsed, it’s good to hear that the accident flight recorders have been discovered[1]. It is reported that they are to be sent to France for replay and analysis.

Sadly, Nepal has a grim record in respect of fatal air accidents. There have been 42 fatal air accidents since 1946[2]. Poor weather and hazardous terrain can often be a problem in this nation. However, in the case of this tragic flight, video circulating on social media indicates clear skies at the time of the accident.

Nepal became a member of International Civil Aviation Organisation (ICAO) back in 1960. Nepal’s improvement in safety measures and compliance with international standards was recognised by ICAO in 2018. However, Nepal remains on the EU Air Safety List.

Prior to the accident, Yeti Airlines has 6 ATR 72 aircrafts, aged between 11 and 15 years old.

The new international Pokhara Airport[3], was inaugurated on the 1st January, this year by Nepal’s Prime Minister. This was seen as a significant step to boost tourism in the region. The airport project was a cooperation as part of China’s Belt and Road Initiative (BRI)[4]. The new international airport was built to replace the city’s former airport, located 1.6 nm to the West. Flights were gradually being transferring to the new airport facility[5].

The Civil Aviation Authority of Nepal (CAAN) has checked the airworthiness of the ATR aircraft on its register. No technical faults have been found[6].

POST: Teams of aviation experts, including those from ATR and EASA are on their way to Nepal to help in the accident investigation French team starts probe into Nepal plane crash (msn.com)


[1] https://www.reuters.com/world/asia-pacific/search-resumes-four-people-missing-nepal-after-deadly-air-crash-2023-01-16/

[2] according to Flight Safety Foundation data

[3] http://pokharaairport.com.np/

[4] https://www.telegraphindia.com/world/nepals-pokhara-airport-was-inaugurated-two-weeks-ago-and-built-with-chinese-assistance/cid/1910031

[5] https://aviationweek.com/air-transport/safety-ops-regulation/yeti-airlines-atr-72-crash-nepal-kills-least-68

[6] https://nepalnews.com/s/nation/caan-carries-out-technical-tests-on-all-atr-aircraft-operational

SPO 2

An instant reaction to Single Pilot Operations (SPO) is like the instant reaction to completely autonomous flight. “I’m not getting on an aircraft without a pilot!” Then to justify that reaction fatal accidents of the past are cited. Typically, this is to remind everyone of the tragic Germanwings accident[1]. It was 24 March 2015, that an Airbus A320 was crashed deliberately killing all onboard.  

However, it’s wise to remember that the likelihood of incapacitation[2] is much greater than that of the malicious behaviour of the pilot in command. Cases of malicious behaviour leading to a catastrophic outcome are truly shocking but extremely rare.

One fatal accident, that is still disputed is EgyptAir Flight 990[3] that killed 217 people in 1999. The possibility of inflight pilot suicide is unnerving, since on the face of it there is little any of the aircraft’s cabin crew or passengers can do to stop it.

This could be a future opportunity to use automation to prevent these scenarios occurring. Afterall the aircraft knows where it is and that a sustained high-speed dive towards the ground is not normally intended. A safety system exists to do this[4], but its outputs are not connected to the aircraft’s flight controls.

Humans being adaptable, extremely creative and capable of highly irrational actions, it’s unlikely that malicious behaviour resulting in aviation accidents will ever be reduced to zero. This is said regardless of the procedures or technology involved. The fate of flight MH 370 remains a mystery.

Thus, the prominent safety issue in respect of SPO is pilot incapacitation. Where the pilot in command is no longer able to perform as expected. That is, if the aircraft flown is not capable of safely landing itself. The objective always being safe continued flight and landing.

I’ve had the “1% Rule” rule explained to me by a notable aviation doctor, but I must admit I didn’t fully take it in. So far, the rule has stood the test of time. When the pilot in command of a Czech Airlines aircraft collapsed and died on route from Warsaw to Prague in 2012, the co-pilot took over and everyone got home safely.

Any automated co-pilot must be at least as capable as a human co-pilot in all aspects of operation of an aircraft. The key word here being “all”. It’s not enough to have the functions necessary to undertake safe continued flight and landing. Task such as communicating with the cabin crew and passengers must also be considered. Including preparation for an emergency landing.


[1] https://www.bbc.co.uk/news/world-europe-32072218

[2] http://www.avmed.in/2012/02/pilot-incapacitation-debate-on-assessment-1-rule-etc/

[3] https://www.theguardian.com/world/2002/mar/16/duncancampbell

[4] https://skybrary.aero/articles/terrain-avoidance-and-warning-system-taws

Single Pilot Operations

Single Pilot Operations is not new. What’s new is considering this way of working for everyday public transport operations of large aircraft

Research is of fundamental importance. It seems obvious to say so given the benefits it has given us. When proposals come forward to exploit new technologies there needs to be that moment when everyone steps back and takes a long hard look at the implications of its use.

In basic technical research it’s not the most important consideration is to focus on the drivers for change. They can be multifarious: economic, environmental, social, safety, security, political, and maybe just a matter of preference. Policy directions are taken by the industry and governments not constrained by what is happening now as much as what might happen tomorrow.

Research has delivered incredible safety improvements in aviation. This is not only in the basic design and construction of aircraft but all aspects of their operation. So, to see that the European Union Aviation Safety Agency (EASA) sponsoring research to study the implications of aircraft Single Pilot Operations[1] is a wholly good measure.

My history goes back to the early days of fly-by-wire aircraft systems. This is where the mechanical and physical connection between an aircraft pilot’s actions and the control surfaces that determine flight are replaced by digital computers. Back in the 1980s, a great deal of research and experimental flying proved the technology to make fly-by-wire work. It first found favour with the military. One reason being that an aircraft’s capability could be extended well beyond what was formerly reached. This change was introduced with caution, analysis, testing and much detailed risk assessment.

At the time, there was a significant body of professional pessimists who predicted a diminishment of aviation safety. Today, four decades on, studies show that even as air traffic has increased so civil aviation safety has improved. A momentous achievement. An achievement that has, in part, been because of the well-regulated adoption of advanced technologies. 

It is important to look at potential changes with an open mind. It’s easy to come to an instant opinion and dismiss proposals before a detailed study has been conducted. The detailed technical research can then be part of the challenge and response that is necessary to before approval of any major change. First difficult questions need to be tabled and thoroughly investigated.


[1] https://www.easa.europa.eu/en/research-projects/emco-sipo-extended-minimum-crew-operations-single-pilot-operations-safety-risk

Air Taxi 3

Urban mobility by air, had a flurry of success in the 1970s. However, it did not end well.

Canadian Joni Mitchell is one of the most celebrated singer-songwriters and my favourite. She has tapped into the social and environmental issues that have concerned a lot of us for decades. Of her large catalogue, I can’t tell you how much I love this song[1]. The shear beauty of the lyric.

Anyway, it’s another track on the album called “Hejira” that I want to refer. When I looked it up, I found out, I was wrong. The song I want to refer to is on the 1975 album “The Hissing of Summer Lawns”. The song “Harry’s House[2]” contains the line “a helicopter lands on the Pan Am roof like a dragon fly on a tomb.” Without going into what it’s all about, the lyrical image is that flying from a city skyscraper roof was seen as glamorous and the pinnacle of success.

In 1970, prominent aviation authorities were talking about the regulatory criteria needed for the city-centre VTOL[3] aircraft of the future. Then on the afternoon of 16 May 1977, New York Airways Flight 971, a Sikorsky S-61 helicopter, crashed[4] on Pan Am’s building rooftop heliport[5]. That ghastly fatal accident reset thinking about city centre operations air transport operations.

So, what’s different 50-year on? Proposals for city centre eVTOL operations are much in the News. City planners are imagining how they integrate an airborne dimension into public transport operations. Cars, busses, trains and eVTOL aircraft may all be connected in new multimodal terminals. That’s the city transport planners’ vision for less than a decade ahead.

For one, the vehicles are radically different. Yes, the physics of flight will not change but getting airborne is quite different between a conventional large helicopter and the plethora of different eVTOL developments that are underway across the world.

Another point, and that’s why I’m writing this piece, is the shear amount of safety data that can be made available to aircraft operators. Whereas in the 1970s, a 5-parameter flight recorder was thought to be neat, now the number of digital parameters that could be collected weighs in over thousands. In the 1970s, large helicopters didn’t even have the basic recording of minimal flight data as a consideration. The complexity in the future of eVTOL will be, not how or where to get data but what to do with all the data that is streamed off the new aircraft.

Interestingly, this changes the shape of the Heinrich and Bird “safety pyramid” model[6]. Even knowing about such a safety model is a bit nerdy. That said, it’s cited by specialist in countless aviation safety presentations.

Top level events, that’s the peak of the pyramid, remain the same, but the base of the pyramid becomes much larger. The amount of safety data that could be available on operational occurrences grows dramatically. Or at least it should.

POST: Growing consideration is being given to the eVTOL ecosystem. This will mean a growing need to share data Advanced Air Mobility Portal (nasa.gov)


[1] https://youtu.be/nyj5Be5ovas

[2] A nice cover https://youtu.be/bjvYgpm–tY

[3] VTOL = Vertical Take Off and Landing.

[4] https://www.nytimes.com/1977/05/17/archives/5-killed-as-copter-on-pan-am-building-throws-rotor-blade-one-victim.html

[5] https://www.thisdayinaviation.com/16-may-1977/

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

Safety Performance Indicators

What’s happening? Two words, and what seems like the easiest question in the world. Open your phone, look at the screen and a myriad of different sources of information are screaming for your immediate attention. They are all saying – look at me, look now, this is vital and don’t miss out. Naturally, most of us will tune out a big percentage of this attention-grabbing noise. If we didn’t life would be intolerable. The art of living sanely is identifying what matters from the clutter.

So, what happens in aviation when a Chief Executive or Director turns to a Safety Manager and askes – what’s happening? It’s a test of whether that manager’s finger is on the pulse, and they know what’s happening in the real world as it happens.

This is a place I’ve been. It’s a good place to be if you have done your homework. It’s the way trust is built between the key players who carry the safety responsibility within an organisation.

One of the tools in the aviation safety manager’s toolbox is that of Safety Performance Indicators (SPIs). In fact, it’s part of an international standard[1] as part of a package for conducting safety assurance. Technically, we are talking about data-based parameters used for monitoring and assessing safety performance.

The ideas are simple. It’s to create a dashboard that displays up-to-date results of safety analysis so that they can be viewed and discussed. Like your car’s dashboard, it’s not a random set of numbers, bar-charts, and dials. It should be a carefully designed selection of those parameters that are most useful in answering the question that started this short blog.

That information display design requires great care and forethought. Especially if there’s a likelihood that serious actions will be predicated on the information displayed. Seems common sense. Trouble is that there are plenty of examples of how not to do this running around. Here’s a few of the dangers to look out for:

Telling people what the want to hear. A dashboard that glows green all the time it’s useless. If the indicators become a way of showing off what a great job the safety department is doing the whole effort loses its meaning. If the dashboard is linked to the boss’s bonus, the danger is that pressure will be applied to make the indicators green.

Excessive volatility. It’s hard to take indicators seriously if they are changing at such a rate that no series of actions are likely to have an impact. Confidence can be destroyed by constantly changing the tune. New information should be presented if it arises rapidly, but a Christmas tree of flashing lights often causes the viewer to disbelieve.

Hardy perennials. There are indicators, like say; the number of reported occurrences, which are broad brush and frequently used. They are useful, if interpreted correctly. Unfortunately, there’s a risk of overreliance upon such general abstractions. They can mask more interesting phenomena. Each operational organisation has a uniqueness that should be reflected in the data gathered, analysed, and displayed.

For each SPI there should be an alert level. It can be a switch from a traffic light indication of green to amber. Then for the more critical parameters there should be a level that is deemed to be unacceptable. Now, that might be a red indicator that triggers a specific set of significant actions. The unscheduled removal or shutdown of a system or equipment may be tolerable up to a certain point. Beyond that threshold there’s serious safety concerns to be urgently addressed.

The situation to avoid is ending up with many indicators that make seeing the “wood from the trees” more difficult than it would otherwise be. Afterall, this important safety tool is intended to focus minds on the riskiest parts of an operation.


[1] ICAO Annex 19 – Safety Management. Appendix 2. Framework for a Safety Management System (SMS). 3. Safety assurance. 3.1 Safety performance monitoring and measurement.