Safety in numbers. Part 2

Previously, we walked on a path through some simple statistics as they relate to aircraft systems. Not wishing to sound like the next episode of a popular drama, the only recap needed is, that by making a few assumptions we showed that: where P is the probability of failure and n is the number of similar concurrently operating systems:

A total failure occurs at probability Pn

A single failure occurs at probability n x P

It’s as well to distinguish between the total system and the sub-systems of which it comprises. For example, we can have one aircraft normally operating with four engines. Here we can call each individual engine a sub-system. The word “simple” can best be applied for highly reliable sub-systems where there’s only a few and n is a low number.

Aviation is going through a period of great change. A big part of that change is electrification. Today, there are numerous Quadcopter designs. The name gives it away. Here we are dealing with 4 electric motors connected to rotors. Some new aircraft designs go much further with as many as 18 electric motors. That’s 18 similar sub-systems all contributing to the safe flight and landing of an aircraft.

Superficially, it would be easy to say that if n equals 18 then the chances of the failure of all propulsion simultaneously is astronomically low. That’s true but only if considering the reliability of the electric motors providing propulsion in isolation. Each electric motor makes a partial contribution to the safe performance of the aircraft.

Just as we have with fuel systems in conventional aircraft, in an electric aircraft, each of these sub-systems are dependent upon a source of power being provided. If the source of that power disappears the aircraft’s motor count becomes irrelevant. This is referred to as the consideration of common-mode failures. The electric motors maybe independent in operation but they are all dependent upon the reliable supply of electrical power.

Before a discussion of common-mode failures, let’s go back to the earlier maths. We can see that the loss of one electric motor, amongst 18 occurs with a probability of 18 x P. Unfortunately, in these cases the possible combinations of multiple failures increases.

Given that this subject is so much easier to discuss when dealing with small numbers, let’s consider the Quadcopter. Here there are 4 electric motors and 4 groups of distinct failure condition: 1 motor failed, 2 motors failed, 3 motors failed, and 4 motors failed. For the sake of argument let’s say they perform the same function and call them motors A, B, C and D.

Except for the case where all 4 motors fail, 3 cases produce an outcome with a reduced aircraft capability. We have the way of calculating the probability of total failure and a single failure so it’s the double failure and triple failure cases that are of interest.

Let’s step through the combination of double failures that can occur. Here they are A and B, B and C, C and D, D and A, A and C, B and D. There are 6 unique combinations that make up double failures.

Let’s step through the combination of triple failures that can occur. Here they are A and B and C, B and C and D, C and D and A. D and A and B. There are 4 unique combinations that make up triple failures. We can tabulate these findings for our Quadcopter motor failures thus:

SingleDoubleTripleTotal
4P6P24P3P4

There’s a nice pattern in this table of probabilities. The number of possible combinations of multiple failures grows as n grows.  

Now, we get more into the subject of combinations and permutations. The word “combination” is more often in common usage. When we use that word, it really doesn’t matter what order that any failures occur. Often combinations are like other combinations and so each may not be entirely unique in its impact on the flight of an aircraft. Hence the doubles and triples above.

With 4 electric motors there are 24 possible combinations. This is calculated thus:

n! = n × (n – 1) × (n – 2) × (n – 3)

This is pronounced “n factorial”. So, for n = 18 this gets big. In fact, it’s 6,402,373,705,728,000. 

However, as we have seen from the Quadcopter discussion it’s the grouping of failure conditions that we are often most interested in. Afterall, for safe flight and landing of an aircraft we need to manage those failure conditions that can be managed. At the same time reducing the probability of occurrence of the failure conditions that can’t be managed.

That’s a lot of work. It may explain the drive to develop autonomous aircraft systems. The case could be made that managing flight is impossible when subject to the vast array of potential combinations and permutation of failure conditions that can exist within a multi rotor systems, where n is large.

[Do you agree?]

Safety in numbers. Part 1

It’s a common misconception that the more you have of something the better it is. Well, I say, misconception but in simple cases it’s not a misconception. For safety’s sake, it’s common to have more than one of something. In a classic everyday aircraft that might be two engines, two flight controls, two electrical generators and two pilots, so on.

It seems the most common-sense of common-sense conclusions. That if one thing fails or doesn’t do what it should we have another one to replace it. It’s not always the case that both things work together, all the time, and when one goes the other does the whole job. That’s because, like two aircraft engines, the normal situation is both working together in parallel. There are other situations where a system can be carrying the full load and another one is sitting there keeping an eye on what’s happening ready to take over, if needed.

This week, as with many weeks, thinkers and politicians have been saying we need more people with a STEM education (Science, Technology, Engineering, and Math). Often this seems common-sense and little questioned. However, it’s not always clear that people mean the same things when talking about STEM. Most particularly it’s not always clear what they consider to be Math.

To misquote the famous author H. G. Wells: Statistical thinking may, one day be as necessary as the ability to read and write. His full quote was a bit more impenetrable, but the overall meaning is captured in my shorten version.

To understand how a combination of things work together, or not, some statistical thinking is certainly needed. Fighting against the reaction that maths associated with probabilities can scare people off. Ways to keep our reasoning simple do help.

The sums for dual aircraft systems are not so difficult. That is provided we know that the something we are talking about is reliable in the first place. If it’s not reliable then the story is a different one. For the sake of argument, and considering practical reality let say that the thing we are talking about only fails once every 1000 hours.

What’s that in human terms? It’s a lot less than a year’s worth of daylight hours. That being roughly half of 24 hours x 7 days x 52 weeks = 4368 hours (putting aside location and leap years). In a year, in good health, our bodies operate continuously for that time. For the engineered systems under discussion that may not be the case. We switch the on, and we switch them off, possibly many times in a year.

That’s why we need to consider the amount of time something is exposed to the possibility of failure. We can now use the word “probability” instead of possibility. Chance and likelihood work too. When numerically expressed, probabilities range from 0 to 1. That is zero being when something will never happen and one being when something will always happen.

So, let’s think about any one hour of operation of an engineered system, and use the reliability number from our simple argument. We can liken that, making an assumption, to a probability number of P = 1/1000 or 1 x 10-3 per hour. That gives us a round number that represents the likelihood of failure in any one hour of operation of one system.

Now, back to the start. We have two systems. Maybe two engines. That is two systems that can work independently of each other. It’s true that there are some cases where they may not work independently of each other but let’s park those cases for the moment.

As soon as we have more than one thing we need to talk of combinations. Here the simple question is how many combinations exist for two working systems?

Let’s give them the names A and B. In our simplified world either A or B can work, or not work when needed to work. That’s failed or not failed, said another way. There are normally four combinations that can exist. Displayed in a table this looks like:

A okB ok
A failsB ok
A okB fails
A failsB fails
Table 1

This is all binary. We are not considering any near failure, or other anomalous behaviour that can happen in the real world. We are not considering any operator intervention that switches on or switches off our system. We are looking at the probability of a failure happening in a period of operation of both systems together.

Now, let’s say that the systems A and B each have a known probability of failure.

Thus, the last line of the table becomes: P4 = PA and PB

That is in any given hour of operation the chances of both A and B failing together are the product of their probabilities. Assuming the failures to be random.

Calculating the last line of the table becomes: P4 = PA x PB

In the first line of the table, we have the case of perfection. Simultaneous operation is not interrupted, even though we know both A and B have a likelihood of failure in any one hour of operation.

Thus, the first line becomes: P1 = (1 – PA) x (1 – PB)

Which nicely approximates to P1 = 1, given that 1/1000 is tiny by comparison.

The cases where either A or B fails are in the middle of the table.

P2 = PA x (1 – PB) together with P3 = (1 – PA) x PB

Thus, using the same logic as above the probability of A or B failing is PA + PB

It gets even better if we consider the two systems to be identical. Namely, that probabilities PA and PB  are equal.

A double failure occurs at probability P2

A single failure occurs at probability 2P

So, two systems operating in parallel there’s a decreased the likelihood of a double failure but an increase in the likelihood of a single failure. This can be taken beyond an arrangement with two systems. For an arrangement with four systems, there’s a massively decreased likelihood of a total failure but four times the increase in the likelihood of a single failure. Hence my remark at the beginning. 

[Please let me know if this is in error or there’s a better way of saying it]

Identity

Britan was never part of the Schengen Agreement[1]. I get that. In the days when I was commuting backwards and forwards between the UK and Cologne, Germany, I always had to show my British passport. So, although we once had freedom of movement in the European Union (EU) that document was essential to prove identity. Afterall, we do not have Identity cards (ID) in the UK. Even inside the Schengen Area[2] it’s necessary to carry personal identification. I remember being told off by a policeman for not having ID, other than a UK driver’s licence, on a high-speed train on the trip between Cologne and Brussels. He was fine about it, but it was a friendly – don’t do it again.

Generally, British people do travel overseas. Many of us travel for holidays and business, and in Europe, Spain is one of the most popular destinations.

The number of British people holding a British passport could be well over 80%. This is way ahead of Americans, for example[3]. This doesn’t take account of British passports that may have expired or been lost or destroyed. However, the remarkably large number of British people with passports does underline our love of travel.

I came back from a week’s sunshine in Grand Canary on Monday evening. It’s the second time I’ve been through the airport on that island. Entering the spacious modern airport, the first part of the process is relatively easy. Check-in and drop bags were shared with a great number of tired travellers. Even the hand baggage security check was straightforward.

It’s not until the gate number came up, and the long walk to the far end of the terminal was needed did it appear that the British experience was different. The departure gates were in a glass box wrapped around the end of the terminal. To get into the glass box it was necessary to go through passport control.

For those, like me there were electronic passport barriers. The ques there were shorter than the manual checks. The electronic passport barriers worked. However, on the other side of the glass wall was another que and a uniformed official checking passport. After that there was a desk where each passport had to be stamped. So, that’s 3 checks and an official exit stamp.

So, what’s the value of this added bureaucracy post-Brexit? I have no idea. What’s more upon boarding the aircraft for the flight home, the gate staff check passports again. So, that’s 4 inspections of passenger identity. 5 if the check-in desk procedure is included. British passports may have thick cardboard covers, and secure bindings but their strength as an international travel document has diminished since Brexit.


[1] a treaty which led to the creation of Europe’s Schengen Area, in which internal border checks have largely been abolished.

[2] https://ec.europa.eu/home-affairs/pages/glossary/schengen-agreement_en

[3] https://www.newsweek.com/record-number-americans-traveling-abroad-1377787

Island chaos

Aviation is an international industry. Britain has been “No longer an Island”[1] for over 120 years. As the Wright Brothers demonstrated practical powered flight, so the importance of sea travel began a decline. Nothing in history has shaped the British more than our island status. Living on an island has moulded attitudes, character, and politics.

The illusion of absolute national autonomy and sovereignty is shattered by the interconnection and interdependencies established by flight. Aviation’s growth encouraged a lowering of impediments between nations and geographic regions. In some respects, this has been a two-edged sword. On the one hand, there’s more cooperative working across the globe than there has ever been. On the other hand, conflict crosses natural barriers with much greater ease.

Affordable rapid air travel and growing freedom of movement have been a great boom in my lifetime – the jet age. At the same time, it’s not new that nationalist politicians continue to fear the erosion of difference between the British and the nations of continental Europe, brought about by commercial aviation. Ironically, it’s now the newer digital industries that pose the greatest threat to the illusion of complete independence.

In this context the failure to tackle the critical understaffing at British airports is deep rooted. Lots of finger pointing and experts blaming each other with a catalogue of reasons misses the damage that’s being done by nationalist “conservative” politicians.

Staffing shortages, poor planning and the volume of people looking to travel have led to huge queues and many flight cancellations across UK airports.

Yes, today’s travellers have learnt to take a great deal for granted. They are no longer impressed with the ability to check their emails and watch a movie at 30,000 feet above the sea. So, when the basics go wrong, and flights are seemingly arbitrarily cancelled, queues are long and delays are frequent, the backlash is real.

A UK Minister’s[2] reluctance to restore some freedom of movement to European aviation workers to alleviate the current chaos is an example of blindness to reality. Looking at the historic context, I guess, we should not be surprised that this dogmatic UK Government is so blinkered. Any acknowledgement that the imposition of Brexit is a big factor in airport chaos is far more than their arrogant pride can take. Sadly, expect more problems.


[1] https://www.goodreads.com/book/show/4254465-no-longer-an-island

[2] https://www.independent.co.uk/news/uk/government-transport-secretary-bbc-gatwick-covid-b2092887.html

Past fatal accidents

What can cause an aircraft to plumet from high altitude in an uncontrollable way? A selection of accidents come to my mind.

One tragic accident was Indonesia AirAsia Flight 8501, Airbus A320-216[1] in December 2014. Here a malfunction in the rudder control system was reacted to by the crew in an inappropriate way. This fatal accident was put down to pilot error. That is mishandling after an aircraft system failure leading to a stall and plunge into the sea.

The loss of control and crash of Alaska Airlines Flight 261 McDonnell Douglas MD-83[2] in January 2000 is different from the recent Boeing 737 fatal accident but it warrants inspection[3]. For a start the MD-80 series has a high tail and rear engines. However, Flight 261 had a highly experienced crew, but the failure of a critical control component meant the aircraft became unrecoverable. Also, the MD-80 series of aircraft is of a similar generation to the Boeing 737. For both aircraft types, the control of the horizontal stabilizer is necessary to maintain safe flight. The MD-60 accident involved a catastrophic loss of pitch control.

Looking at the sequence of the fatal accident of SilkAir Flight 185, Boeing 737-300[4], in December 1997 it has some similarities. The lead investigators were unable to determine the cause, but suspicion fell on the aircraft rudder controls. This accident remains controversial. The accident flight recorders either stopped because wires broke or because their power was wilfully disconnected. We will never know which was the case.

Again, an accident with an inconclusive report is that of the uncontrolled descent and crash of United Airlines Flight 585. Boeing 737-200[5], March 1991. Anomalies were identified in the accident airplane’s rudder control system, but the accident was not attributed to these problems.

As can be seen from this small sample of accidents the interaction between aircraft and crew, when a control system failure occurs is a matter of great interest.


[1] https://bea.aero/uploads/tx_elydbrapports/Final_Report_PK-AXC-reduite.pdf

[2] https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR0201.pdf

[3] https://www.nytimes.com/2000/02/14/us/safety-board-says-wear-was-found-on-jet-in-1997.html

[4] http://knkt.dephub.go.id/knkt/ntsc_aviation/Revised-MI185%20Final%20Report%20(2001).pdf

[5] https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR0101.pdf

What are the likely scenarios?

When dealing with aircraft system safety, I often found it difficult to encourage design engineers to look at aircraft level effects. It was more common to address each set of systems as if they were the only ones that counted.

Safe continued flight and landing depends on a whole host of interactions. Picking up a technical specification, for say an autopilot, reading it and understanding it is one thing. It’s harder to appreciate how it interacts with every other part of an aircraft in flight.

Considering a large commercial aircraft there are only a few general conditions that can create a total catastrophe. I’m using a specific meaning of that well used word. In this case, catastrophe is a complete aircraft level failure situation that is non-recoverable. A chain of events that leads inevitably to fatalities and a total hull loss.

There are only a few general conditions because there are design commonalities between modern civil aircraft. For example, they all need surfaces that generate lift and surfaces that enable aircraft control. They all have propulsion systems that generate thrust. If they are for civil passenger transport, they all have environmental control systems that maintain a habitable environment within a pressurised area.

In flying, they all are subject to the effects of weather. That is any hostile situation that can exist in the atmosphere, from ground up.

With what is so far known about the crash of China Eastern flight MU5735, when thinking about potential aircraft level events, it’s not possible to rule out many scenarios.

However, it’s extremely difficult to conceive of a weather event on the day of occurrence that could have led to such a disastrous outcome. No great storm activity was reported. So, this is unlikely to have been an accident like Air France flight AF447 in 2009[1]. A high-altitude stall can be recovered if no other significant negative factors come into play.

Additionally, it’s extremely difficult to imagine this accident as a depressurising event. So, this is unlikely to have been an accident like Helios Airways flight 522 in 2005[2]. Unless there was a massive explosive decompression that caused structural and control damage. Japan Air Lines Flight 123 in 1985 had such a tragic fate[3].

Engines can fail in a spectacular way but that does not normally destroy a whole aircraft. A total loss of propulsion turns a large aircraft into a large glider. The trajectory of this aircraft suggests something happened that was far more devastating than the loss of one, or both engines.

Issues related to communication and navigation can put to one side given that the accident from start to finish was so rapid. No crew communication is reported to have taken place.

Following the deductions made above the remaining possibilities that warrant consideration are to do with either or both, structural failure, and unrecoverable aircraft control failure. The accident investigators working on-site will be looking at the deformations found in the recovered wreckage. They will be looking at collecting and putting together what remains of the aircraft control system. They will be saving every electronic circuit board they can find.

By far the remotest possibility is a wilful act of destruction. It’s better to first rule out more likely aircraft scenarios before posing questions that bringing into question those on-board.

Global commercial aviation has a tremendous safety record. China’s aviation safety record is a strong one. As has been said by commentators: planes don’t just drop out of the sky like that one. The urgency of the accident investigation is all too evident. The sooner there’s a plausible theory the sooner corrective action can be put in place.


[1] https://bea.aero/docspa/2009/f-cp090601.en/pdf/f-cp090601.en.pdf

[2] https://aaiasb.gr/imagies/stories/documents/11_2006_EN.pdf

[3] https://www.mlit.go.jp/jtsb/eng-air_report/JA8119.pdf

A wing and a prayer

Gaps

Fascination with the new. Who can resist? Advanced Air Mobility (AAM) provides just that. Often visualised in Science Fiction, plans for flying cars, taxies and autonomous machines buzzing around our heads are as popular as ever. A long-held dream of taking the imagination and making it real is the business of a lot of new entrants in aviation. The proliferation of projects is astonishing. Even with all the hype aside, there’s a strong chance that some organisations will suceeed in changing our skies forever.

This is great. It’s a way of decarbonising but continuing to fly. It opens new ways of undertaking vital tasks, like getting drugs and vaccinees to remote regions of the world. Emergency services can benifit in getting people from A to B faster and less expensivly. It may help get internal combustion engines off our congested roads in major cities. Air quailty may then improve for densly populated areas.

Nothing is for free. The shear complexity of the problems that need to be solved are taxing some smart people all over the globe. Not only that but the accommodation of aviation’s hundred-year legacy must be factored in too. That’s one reason why research and technical programmes are swallowing up the funds with a voracious appetite. Academics, consultants, and engineers are tapping into the pool of funds that Governments are making available.

Aviation has a pitfall that in that it is very unforgiving when errors and failures occur. It’s why the refrain that fits into every safety advocate’s lexicon is – safety is our number one priority. I will not argue as to how sincere those words are spoken. In the vast majority of cases, people mean what they say.

The awareness that in-service aircraft accidents can sink businesses is not lost on most protagonists. Health and Safety practitioners often say: “If you think safety is too expensive, try an accident”.

This note is more about the gaps that are evidence. Reading several publications on advanced air mobility safety and operations, I’m struck by the vagueness and wooliness of the material available. Or at least that’s how the material often starts. Then there’s a rush into infinitesimal detail to crack problems that seem more tangible. There are two problem spaces. There’s the part where uncertainty prevails. Then there’s the part where the nicely bounded nutty, gritty technical problems exist.

There are often far more questions than answers. Documents that proport to have answers are littered with questions. I’m reminded of the HHGTTG[1]. Talking about the invention of the wheel and a group considering what to do with it: “Well, if you’re so smart – what colour should it be?”

Asking the right questions is a must but there’s a lack of clarity too. Before going into painstaking detail on a set of scenarios a sound report should states its underlying assumptions first. It’s not a good idea to bypass the fundamentals. For AAM to go beyond a novelty, real world difficulties need to be faced head on. Context matters. Sharing the airspace with existing users must be considered[2]. Safety assessment must take account of interactions with General Aviation, ballons, recreational activities, aerial work, emergency services and military operations[3].

It wouldn’t be a bad idea to consider how accident investigation will be conducted, even at this early stage. No doubt lots of data will flow from AAM but will it be what’s needed when things go wrong?


[1] https://www.bbc.co.uk/programmes/b03v379k

[2] UK CAA CAP2272, October 2021

[3] https://www.mitre.org/sites/default/files/publications/pr-19-00667-9-urban-air-mobility-airspace-integration.pdf

Avionics

Segmenting, categorising, and naming technical subjects has a long history. However, it’s not often there’s a back story to say what’s in each name. Numerous definitions exist. These are quite often an afterthought. Naming that evolves rather than can be traced to a single author.

The subject on my mind is Avionics. It’s a ubiquitous term in aircraft engineering. In fact, it’s applied much more widely than that because administrators, pilots and air traffic controllers all use it. So, let’s look at the history, etymology and usage of the word.

The word seems obvious, as to not need a definition. Bring the world of aviation and electronics together and there it is – Avionics. However, Avionics often extends beyond the world of aviation and into space. So, it may be better to say, bring the world of aeronautics and astronautics and electronics together and there it is – Avionics.

Notice that it’s electronics and not electrics that forms the definition. A loose distinction between the two might be to say that, in terms of electric current, electronics is anything below an ampere[1] and electrics is that above an ampere.

Marconi was the first to experiment with airborne radio. It was even available to pilots in the First World War. However, spark-gap radio was unloved, heavy, and awkward.

The name Avionics started being used in the 1940s. VHF radio communication between aircraft and ground stations was vital to an aircrafts’ operation. The fabrication of radio valves in high volumes and at low costs led to the use of numerous radio technologies: communications, navigation, RADAR and Radio Altimeters to name a few.

The science and technology of electronics, and the development of electronic devices has advanced faster than that of aircraft design and manufacture. Avionics engineering has been divided into numerous sub-fields as a result.

Where once an aircraft could complete safe flight and landing with a complement of defective avionic equipment that is no longer the case. It’s quite the reverse, as the current generation of both military and civil aircraft are highly depended upon the correct functioning of their avionic systems.

Often the more complex an aircraft and its operation becomes, the more complicated the avionic systems become. Aircraft flight-control systems can be of great sophistication. By contrast a VHF radio hasn’t changed much, in its basic function, for decades.

Although avionics is a common term, it doesn’t often find its way into legislation or everyday usage. There’re certainly great swathes of the population for which the word means nothing. It’s an unusual day if the six-o’clock news has a reference to this technical word. 


[1] https://www.npl.co.uk/si-units/ampere

Still work in progress

Has it really been 100 days since the final, final, final Brexit day? 

The UK left the European Union (EU) on 31 January 2020.  A Withdrawal Agreement (WA) that the UK Government agreed with the EU, established a transition period that came to an end the day this year started.  Now, a new EU-UK Trade and Cooperation Agreement (TCA) has been in force for 97 days. So, it’s not a bad time to have a go at writing a 100-day review.  It’s often a period of reflection that is used to assess a newly elected politician.  It gives an indication of the direction of travel. 

Last year, although it was a top priority of UK industry to stay in, the UK has left the European Union Aviation Safety Agency (EASA) based in Cologne.  So, there’s no official UK participation in the EASA activities by right and the UK is treated as any other 3rd Country.  EU law no longer applies to the UK. Much of what was previously applied has been swept up in new UK Legislation[1]

Regulation-wise, to figure out where we are now, it’s necessary to combine the officially published corresponding text of UK Legislation and EU Commission Regulations with the EASA Acceptable Means of Compliance and Guidance Material, including amendments.  Some smart people have done this work, but the challenge will be keeping the whole paperwork construction up to date. 

Informed commentators have often said that a Bilateral Aviation Safety Agreement (BASA) and a Comprehensive Air Transport Agreement (CATA) are needed between the EU and UK.  To some extent the TCA starts the ball rolling by calling for the establishment of a number of committees. 

On the basis that there’s far to much still in flux to discuss, I’ll bite off one key aviation related subject. 

Despite the massive impact of the COVID pandemic on international civil aviation there remains a demand for qualified engineers.  In many ways their roles as Airworthiness Inspectors or Licenced Aircraft Maintenance Engineers have become even more important than ever. Traditionally, there’s no doubt that the UK has been good at training aircraft engineering personnel. Students from all over the world have gained their licences in the UK.  It’s one of the most demanding professions in the world but their dedication to the highest standards keeps flying safe. 

Whilst the UK was a member of the EASA system a licence granted in the UK by an approved organisation was recognised throughout the EASA Member States and beyond.  One of the powerful arguments for continued participation in EASA was the avoidance of the duplication of approvals, certification, and licencing. Each duplication comes with a fee and time consuming paperwork.

The political decisions having been made and that’s exactly what we now have in place. Duplication. In fact, it’s worse than that because there’s asymmetry in the current situation. 

The UK CAA advises Part 66 licence holders to take action to minimise impact on their privileges.  There are several combinations and permutations that can be considered.  There’s a useful updated section of information for licensed engineers on the UK CAA website[2]

Engineers who continue to release EU-registered aircraft to service outside the UK will need to transfer their licence to the National Aviation Authority (NAA) of an EASA Member State. If an engineer works outside the EU and UK, on EU-registered aircraft, a UK Part-66 licence will no longer be valid. 

If an engineer has a non-UK Part-66 licence they will be able to continue to work on UK-registered aircraft for up to two years after the end of the transition period, unless your licence changes or expires (whichever occurs soonest).

There’s also an exemption for engineers who hold a EU Member State issued EASA Part-66 licence who only received
or changed their EASA licence after the departure of the UK from the EU.

All of this is high politics because a Part 66 licence, UK or EU is granted on the same technical basis. Yes, there’s potential of regulatory divergence or new ways of doing business in future. However, it’s difficult to understand what the justification for any divergence might be but the possibility exists.  And as avid Brexit supporters like to point out the UK is no longer subject to EU legislation.  That has no impact of the UK’s need to meet its international obligations. Both UK and EU need to be complient with the ICAO Convention.

There’s much work in progress. Now, is a moment when it all looks like a kitten as been playing with a large ball of wool that has rolled down a staircase.


[1] https://info.caa.co.uk/uk-regulations/

[2]https://info.caa.co.uk/uk-eu-transition/licensed-engineers/

Mars flight

I was wondering – is there air on planet Mars? It’s one thing to say is there life on Mars? We’ve been asking that big question of generations. But can we use the word “air”? There’s a thin atmosphere on Mars but can you call it air? The rover that’s there will be listening for sounds in what is 95% carbon dioxide. That kind of atmosphere on Earth would be our worst nightmare.

Let’s look at the definition of that everyday word – air.  Air is the mixture of gases which forms the Earth’s atmosphere and which we breathe.  No way could we breath on Mars.  That gas we depend on, oxygen is down to about 0.1%. Taking that basic definition then Mars does not have “air” in the common sense.

I’m going down this rabbit hole because of the references to Ingenuity, the Mars Helicopter that is being prepared for flight. This innovative flying machine has been landed on Mars and is being referred to as a helicopter.  Now, a Helicopter is a heavier-than-air aircraft supported in flight chiefly by the reactions of the air on one or more power-driven rotors on substantially vertical axes[1].

Oh dear, there’s that reference to the air as per planet Earth.  I may be being an aviation pendant, but this could be the time to revisit the definition of helicopter and change the word “air” to “atmosphere”. Afterall, if there’s a gas of sufficent density then flight is possible with the right equipment.

Ingenuity could also be known as a Rotorcraft.  It undeniably has two rotors, so it must be a craft supported in flight chiefly by the reactions of an atmosphere. Since we are entering a new era of aviation as a human built extra-terrestrial vehicle makes a controlled flight for the first time, revisiting definition could be appropriate. 

Then Airworthiness is then better expressed as Flightworthiness. Maybe, Aircraft ought to be Flightcraft. There’s a history here given that a craft that hovers is called a Hovercraft. Which is more important? What it does or what it does it in?

Whatever the nuisances of these internationally used definitions in English, the wonder of this fantastic achievement is not lost on me.  This moment only happens once. The first time the immense challenges of controlled flight on another planet are overcome we are in a new era of aviation. 

Flying in a hostile cold, thin atmosphere will be amazing. Take-off and landing several times will be astonishing.  What magnificent engineering design. Rotors spining at 2400 rpm. This robotic rotorcraft will test the feasility of flying on another world. Imagine what that will open up. From me, all the best good fortune to the team who made this possible. Lift-off and come down in one piece. Looking foward to seeing the pictures.


[1] Annex 8 to the Convention on International Civil Aviation