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The next ‘Big-Thing’ in Aviation

The next ‘Big-Thing’ in Aviation

Commercial aviation is at its centennial. One hundred years ago it was mostly used for freighting or, more particularly, as couriers on behalf of national post offices. Mail then, as emails now, required expeditious transmission. So, in those days, rickety piston engine aircraft criss-crossed the globe generally successfully fulfilling that requirement. Their pilots had a bravado and mystique similar to that of an astronaut today. The true nature of that unique operating environment is well captured by Sainte Exubery in his biography ‘Sand, Sea & Stars’ – now more famed as the author of the ubiquitous ‘The Little Prince’, which itself was devised while he was awaiting uncertain rescue when his plane came down on a remote, high plateau in Morocco. Commercial passenger flights then were more akin to extreme sports than normal travel. That said, at that time, long haul Zeppelins carried almost 100,000 well-heeled passengers across the Atlantic in lavish style, and reasonably safely – until the Hindenburg’s (possibly terrorist instigated) Hydrogen-fuelled flaming destruction in 1936 which bought that era of commercial aviation to a close.

In the hundred years since, aviation technology and safety have steadily improved in incremental steps with revolutionary changes being very rare. In the early 50’s, the jet airliner was likely the first such ’Revolution’ along with the subsequent wide-body jet airliners making cheap (in every sense of that word) air travel available to all. The helicopter in general aviation is surely another. The (almost unequalled) speed of the Mach 2.2 Concorde had too small an impact to be considered revolutionary. Now, the development of AAM (Advance Air Mobility) electrically powered, city-hopping, autonomous flying vehicles has the potential to be the next such revolution. That these air vehicles are to be electrically powered is under the incremental category as is the fact that there will be no pilot which, technically, if not emotionally, is also but an incremental change – this author flew in a fully automatic helicopter in 1968 (a measure of both his maturity and that of automated flight!).

The revolutionary element here is not so much the vehicle but more in how it will be used. Until now commercial flights have, in the main, been over distances of many hundreds of miles in aeroplanes and dozens of miles in helicopters. These flights, in the main, are scheduled and over fixed routes. Even for helicopters in an emergency response context, flight plans are submitted and fixed routes in an (air) traffic controlled environment are generally followed. The AAM environment however, will be over very short distances – typically of less than a dozen miles – be unplanned and ad-hoc and, if the dream is realised, not much above roof-top height and from any door to any door – in short AAM holds the promise of low level bedlam! S o, the revolutionary element here is less one of vehicle technology and more one of the huge levels of anticipated production of these small flying craft and how they will be used, with the associated automated control software – IF such can be satisfactorily developed and certified. This article will give an overview of each of these elements.

First the vehicles themselves. This article will be limited to the passenger carrying, so-called ‘Air-Taxis’. This is because the freighting variants have lower certification thresholds (Aerial Work rather than Transport Category) and will anyway merge into the already established Drone market. As one would expect, all the prospective Air Taxis use VTOL (Vertical take-off/landing) technologies. While largely based on rotary wing principals, there is one significant difference. In place of the very large main rotor(s) of the helicopter, powered by a couple of engines through a large reduction gearbox, the eVTOLs use multiple small rotors each individually and directly powered by an electric motor – much lighter and with a higher level of failure redundancy. Forward flight will be either by tilting the overall rotor disc (à la helicopter) or with a separate pusher propeller. Like the smallest light helicopter types, the power-to-weight ratio of current eVtol types is low. This negatively impacts hover precision and also make them susceptible to gusting winds, thus predicating fairly substantial landing pads – currently referred to as Vertiports (more on which below) – and probably, with low certified weather thresholds.

In product development terms we are exactly where we were in aviation a hundred years ago, with scores of start-ups proposing a myriad of different iterations. Aviation authorities (which did not exist 100 years ago) are struggling to keep things under control and have yet to develop a standard. Developers, being entrepreneurial by definition, are promising in-service dates a year-after-next. Given the absence of a formalised standard and the lack of experienced personnel within aviation authorities to produce it, such dates are surely fictional. This author was involved in the commercialisation of modern airships, so has had first-hand experience of this challenge which, in the lighter-than-air case, was resolved by running the development of platforms and regulations in parallel over several years with the OEM typically preparing the regulatory drafts. The same is unlikely to occur in the AAM context due to the high level of competition between protagonists reducing cooperation, and the massive envisaged number of  air vehicles in end-use complicating regulatory controls. That said, the Big Boys in main-line aviation are now becoming deeply involved including DARPA and some defence ministries, some large airlines, Boeing and Airbus and uniquely, two major car manufacturers, Stellatis and Toyota. Also, among the large helicopter operators, Bristow is dipping its toe in the pond with regard to off-shore applications. So buckets of money are being thrown at the problem with investments now measured in billions of dollars (in one’s Airship days, we only ever enjoyed investments in units of millions!). This will likely both speed up certification and reduce numbers of Newco OEMs on the playing field.

Some Leaders of the ‘Air-Taxi’ pack (top left, clockwise) Lilium(Germany), Archer-Midnight (USA), BetaTech.(USA), Joby(USA), Volocopter (Germany), Ehang (China)

Being based on investment pressures rather than technical requirements, all information in the certification context needs to be taken with ‘a bucket of salt’, but there are clear indicators of progress in the ‘real world’ as summarized in the table that follows. This AAM (Advanced Air Mobility) Reality Index (ARI) has been put together by SMG Consulting, a US based business management consultancy working in conjunction with the Vertical Flight Society and Aviation Week. The top half-dozen players are shown in order of their assessed ARI, which generally reflects their level of investment capital. Stated EIS (Entry into Service) dates here are likely based more on financial imperatives than technological fact so, as discussed below, there is little risk of an air-taxi buzzing in your neighbourhood any time soon……

* ARI –
AAM Reliability Index.           **  EIS – Entry Into Service.          *** PP – Production Prototype flying

The Chinese Ehang was one of the first iterations in this field. With capability limited to a single Pax. over 30 km range – a 12 minute flight – it is more reflective of the Wright Brothers’ initial creation than a commercial prospect! That it aspires to claim CAAC certification is surely a factor of not-too-subtle CCP (Chinese Communist Part) influence. Besides anything else, those knee-capping rotors would not pass any serious risk analysis! It is anyway understood that the initial certification is limited to Cavok (ie. perfect weather), within sight of its ground staff and not over built-up areas – thus somewhat limiting its utility as a taxi even if the planned EIS is achieved! The current 1000 unit sales projection, being almost entirely within China, is possibly also a function of gentle arm-twisting.

Volocopter’s ‘Volocity’, also a two-seater and an early iteration, is little better. But at least one has to reach up for an amputation by one of the 18 rotors (although, in fairness, a new 4 seat iteration has one third the number of the rotors and lifts them out of reach). But capacity and capability are marginally less than the Ehang. So, even if a restricted EIS capability was certified by next summer as advertised, in time for the Paris Olympics, the nature of the transportation service it will provide for a single passenger over the spread-out Olympic events, defies imagination. The series has achieved some 2000 test flights in total which, while more than any of its peers, still only equates to a total of only some 350 flight hours. A lot more will surely be required even to achieve a minimum Aerial Work certification to allow it to fly with a (non-paying) passenger over Paris next summer.

Archer & Joby aspire to reasonable aircraft flight parameters. This is largely because their rotors partially / completely tilt (respectively). While  the two early iterations described above achieve forward flight through a marginal tilt of the overall rotor disc – hence their low forward speed (unlike helicopters their rotors have a fixed angle of attack, increasing lift by increasing rpm so limiting said ‘tilt’). These latter tilt rotor types aspire to light helicopter performance (hence the USAF interest) but, due to current battery limitations, not the range.  Based on what the USAF has agreed to pay to acquire a half-dozen test units, the AAM cost-efficiency appears considerably less than light helicopter types, being some 4 times the cost with half the gross disposable load. Of course this is not representative of the envisaged production run which, unlike aircraft, is intended to be more akin to that of the ground vehicles (taxis) it is nominally intended to replace, hence in the hundreds of thousands. But is such a taxi replacement concept feasible?

To judge that one needs to consider AAM operating parameters and particularly landing sites and ‘refuelling’ (ie. recharging) requirements. The latter first. A wheeled taxi, if used 24/7, typically will refuel once a day. A light chopper shuttling, maybe after every 2½ hours of flight. But even the most capable AAM birds will need to recharge every half-hour and likely, sooner. While to recharge car fuel takes a minute and a light chopper maybe 5 minutes, a full AAM recharge will be more than five times that. As we all know from our computers and cell phones, constant topping up destroys battery life. So a regular half-hour full charging is likely an essential requirement. OEMs suggest a typical transit distance for an AAM of some 50km, which at typical stated cruise speeds will take approximately 15 minutes. On landing, the stated battery recharging time is about 12 minutes. So it appears that, in general, flight times and recharging times will be similar – while not an impossible situation, it would seem to be a less-than-optimum state of affairs.

Then there is the small matter of parking. From this diagram it is clear that this air taxi will not be able to pick up passengers in the same way as a standard (4.5x2x1.9m (l-w-h)) London Cab. So the door-to-door ethos of taxis will be inapplicable to the so-called air-taxi.  And, in aviation safety terms, the low power-to-weight ratio of AAMs will predicate a fairly substantial landing pad. And indeed, from glossies provided by prospective, so-called, Vertiport service providers, it would appear that CAP-437 heliport criteria will remain generally relevant for AAMs (see overleaf). So hailing an air taxi will be less like hailing a Cab or ‘Apping’ an Uber and more like hailing a helicopter – so not done on a whim! And then there is the likely weather limitations to consider. Since the developed AAM end-product will be fully automated, low visibility should not be an issue, but wind will. Low power-to-weight ratios and lack of inertia will make AAMs sensitive to updrafts & general turbulence caused by wind – and in the city-scape environment, there are plenty of sources of both in high winds. One would therefore expect a (say) 25knot wind limitation to be imposed – hence, essentially limiting AAMs to fair weather flying. So it would appear that, just when a taxi is most required, these air taxis will be unavailable – not a good prospect!

Costs similarly reflect this. The London Cab illustrated above can be bought for 150-160,000 pounds – say $200k. The USAF has just agreed to purchase a half dozen each Archer and Joby AAMs at a unit cost just short of $25m. United Airlines are expecting a unit cost of an early production AAMs of $2m. Let us assume an established production run is half that. Given the thrill and high transit speeds, a factor of 5 in unit cost seems not unreasonable but again, unlike taxis, one would not use it on a whim. This is made the more so because, to ride in said AAM ‘Taxi’, one will need to first hail a cab to get to the nearest Vertiport atop a multi-level parking lot, take the lift to the upper level (in such salubrious areas, with risk of a mugging) and at the destination Vertiport reverse the process again – in short, such seems low in convenience and high in cost!

Vertiports will likely be of similar dimensions as existing Heliports

And then there is operating cost. The USAF is budgeting AAMs at $1500 per flight hour – roughly twice that of a 4-seat helicopter (which has twice the payload). This is similarly reflected in the Volocity’s suggested seat price for a 10 minute transit (jaunt?) during the Paris Olympics next year which is currently pitched at $385.  Again, for the well-heeled, paying five times the normal taxi fare to cover a distance in one fifth of the time is not unreasonable – but again, for us normal folk, not on a whim! (…..and then one needs to also take into account the cost of that ground taxi (and the time lost) to get to/from the Vertiports at each end…..).

Finally there is the issue of control. Based on outline specifications, AAMs will be buzzing around between 1000-3000ft. So interfacing will national ATC systems should not be a significant issue. But given the high numbers of AAMs envisaged in any city, and the very large number of destination Vertiports required, to operate reliably and safety will require an automated control system of enormous complexity (and cost), the more so because it will also need to cater for massive inter-vehicle 4D positional/vector communication and with passenger reservations in time-frames measured in minutes rather than a day or two as now with existing commercial aircraft types.

Since, given the envisaged nature of the service, pilots will be in insufficient numbers and anyway, too expensive, this massively complex system will have to operate fully autonomously with no ‘human in loop’. Such appears to be a mind-boggling challenge but likely, not beyond the capabilities of Artificial Intelligence. That currently, all are piloted, is in order to simplify the certification process. All proposed types have built-in autonomous capability which, it is expected, will be introduced some years downstream once the flight infrastructure / software is in place. This reflects the anticipated reality that AAM will evolve from the existing low level airspace helicopter management infrastructure which, initially, it will use and from which an Urban Air Mobility (UAM) system is expected to evolve.

Swishing quickly and quietly around the world’s megacities in air-taxis is a worthy dream but, from this elemental overview, it is clear that there are a range of killer issues that may prevent its realization. That said, AAMs will almost certainly come into service albeit in timeframes more likely stretching into the next decade and with only a very few of the dozen’s of current OEM players surviving. In this stretched timeframe, Battery technologies will surely improve, thus resolving the currently ridiculous situation of requiring the same charging times as flight times, and also correcting the present low endurance flight hazard. Green electricity will also surely soon be the norm as Nuclear Fusion becomes a reality (given present trends by 2050). So UAM transportation has good environmental credentials, which however, will apply equally to electric ground vehicles (EVs).  Both AAM and EVs are intended to be fully autonomous with similar risk of systems’ failure leading to accidents. The difference here is that, accidents involving the flying vehicles will likely be very much more serious in terms of damage to both human life & infrastructure. Hence, the associated autonomous UAM management software will need to be very much more demanding and byzantine which, one suspects, is at the limit of human capability, so likely be a productive job for Artificial Intelligence. So, in short, notwithstanding all these challenges, with respect to technologies, this next aviation revolution could happen.

However, the EV ground vehicle revolution which is running in parallel, may prove to be the ‘killer threat’ to the UAM concept. It is lower risk, significantly lower cost and far more advanced. Within the same suggested ten-year AAM certification timeframe all production cars will become electrically powered and (likely) autonomously controlled. Already there are autonomous taxi services in the USA and the use of Apps world-wide to rapidly book a lift through a small number of very large ground vehicle service providers such as Uber, is now a routine matter. As such car ownership in cities is already inessential. In addition, the software systems allowing inter-vehicle communication for effective traffic management are already in service with Google Maps and Waze to name but two.  Once ground vehicles are fully autonomous, vehicle ownership will likely become an anachronism.

It is thus very probable that, using adaptations of existing Apps., within the next decade, vehicle sharing will likely replace vehicle ownership. It is a simple fact that privately-owned vehicles spend some 90% of their life parked. But the new generation of autonomous EVs will run 24/7 and never be idly parked except when recharging. Accordingly, within AAM certification timeframes, individual vehicle ownership will have become an anachronism for rich eccentrics and hence, the numbers of vehicles on the road may be expected to reduce dramatically (by something approaching that 90% of previously parked units) thus eliminating traffic jams and hence, the need for those airborne taxis.

Another threat to AAM is a new generation flying cars. Ground-vehicle-to-fixed-wing conversion types have been around for a couple of generations, but the need for an airstrip at each end has limited their use to that of an eccentric plaything rather than serious transportation. However, a new generation of e-VTOL type cars, now in the early stages of certification, will surely negatively impact the current larger AAM market. While their range and payload limitations /control issues are the same as for AAMs, the fact that flying cars are of the same size as road cars, and are to be offered at the same price as an expensive car, and its ability in principal to go door-to-door, will drive nails into the coffins & demise of AAM. The 2 person-on-board limitation will obviate their use as air-taxis but as a play-thing of the rich, it is in every respect most attractive.

Subaru motor company (1/2) & Alef Aeronautics (3) will lift Flying cars form affluent dream to certified Reality

For these reasons Advanced Air Mobility, while a certain future prospect, may not be revolutionary but, similar to Concorde, more likely will be just another plaything for the rich and famous.  So while these small AAM air vehicles, produced a few small niche manufacturers, will surely soon be swishing over cities quietly, smoothly and safely in the sunshine, the currently booming, multi-billion dollar, prospective AAM industry will most likely ‘crash and burn’!

Aladdin’s Chopper – Brand-New Helicopters vs. As-New

Aladdin’s Chopper – Brand-New Helicopters vs. As-New

Folk typically do not fantasize over buying second-hand used vehicles, least of all a chopper. However, sometimes needs must. Such will be the case in any situation where limiting cash-flow or cost-efficiency are driving parameters. In the mineral resource recovery sector, such is likely to be the case in exploration projects.

In highly profitable production situations, aircraft services, as part of a logistic support framework, are effectively a tax-deductible accessory. In exploration they are not – they are a ‘lost’ expense that could be better spent on the main aim of the project they are supporting. So, for the former, the newest and best, with all bells & whistles, can be considered: for the latter cost-efficiency should be a main driver.  

Also, in production situations, demand for air support is typically high due to the need to move large numbers of personnel and support equipment. In Exploration, personnel numbers are usually lower and the operations more self-contained. The former thus tends to high flight hours predicating the best equipment: for the latter, flight hours are generally low with air support mostly on immediate standby for emergency response, again predicating cost-efficiency as the main driver.  So, for the former ‘brand-new’ is a feasible option but the latter necessitates older, cheaper, aircraft. But ‘old’ need not mean ‘clapped-out’: as explained below, old helicopters can readily (i.e., over a few months) be refurbished to an ‘as-new’ condition.

Ball Park costings (per. Chopper) for the two options are along the lines indicated in the table below – in this regard, an ‘as-new’ aircraft is assumed to be more than 10 years old (as such, typically fully amortised and depreciated). The table shows that, while the operating costs of an older chopper may be some 35% higher than its new counterpart, the fixed financial charges – the more significant element – are some 60+% lower. As a result, overall, an ‘As-new’ aircraft has the capability to achieve the required project air support function with equal safety & equal reliability (as explained hereafter) but at some half the overall cost.


Cost Line Item


As-New (10+ y/o)

Aircraft Book Value



Typical Fixed Monthly Charter Cost  (FMC)*



Assumed Monthly Utilization (flt.hrs)



Cost per flight hour (including fuel)



Typical Monthly Flight-hour Charge  (FHC)



  Total Monthly Cost per Helicopter



Cost (pfh) for normal operations (100/50 hrs p.m. respectively)



* Amortization/Depreciation + Insurance + Air & Ground Crews + Operator overhead & profit

That said, bottom line (literally in the above table), while in monthly cashflow terms the Brand-new Chopper represents a very much higher financial outlay, in production situations, the total operational cost makes this fully justifiable as, with the utilization typically being twice that in an exploration environment, the total cost per flight hour (pfh) in each case is similar. If then, in addition, tax due on highly profitable production operations are taken into account, at least a third of the cost of the brand-new production chopper cost can be offset against tax that would otherwise be paid on said profits, thus making the net cost significantly less than that of the exploration team’s ‘As-new’ chopper. So, the highly profitable production world can treat themselves to the best which, in terms of net value, is still highly cost-effective.

But in the exploration environment, where profits are less certain, this argument does not hold, and cash-flow becomes the driving consideration. But does lower cost predicate lower quality & safety? We all know that in life, generally one gets what one pays for – as such, it is typically expected that expensive vehicles will not only be more luxurious but also more reliable and safer. The thesis of this article is to demonstrate that for helicopters, while high expenditure will buy (marginally) more comfort in brand-new types, with regard to reliability and safety there is no difference – indeed, as explained below, the older aircraft may even have an edge in this regard.

Helicopters (indeed, any unpressurised aircraft) over a period of a ‘couple’ of weeks, can be stripped down to a bare skeleton so that every frame can be readily inspected for corrosion or damage and replaced as necessary – effectively making its refurbishment more-or-less the same process by which a brand-new unit is built. Hull sections displaying weakness can be strengthened or replaced and any showing corrosion can not just be replaced but provided with additional corrosion protection to prevent reoccurrence. External panelling is taken down to bare metal (in older choppers with several layers of paintwork being removed, based on previous experience, weighing as much as 80kg!). Any badly corroded panelling is replaced with brand-new units from the OEM and the entire hull is covered with several layers anti-corrosion paint.

New lamps from old – how aging helicopters can be reborn ‘As-new’ with analogue cockpits digitized

New lamps from old – how aging helicopters can be reborn ‘As-new’ with analogue cockpits digitized

With the helicopter thus stripped down to bare frames, ageing wiring looms, anyway, made by specialist companies not by the aircraft OEM, can now be readily replaced. At the same time, the installation of the automated wonders of digital early warning of critical systems’ failure, can be easily installed. Similar to HUMS in brand-new helicopter types, these systems comprise a couple of dozen sensors feeding data into a similar AVMS (Automatic Vibration Monitoring System) computer. At the same time analogue cockpit instrumentation (as shown above) can be readily upgraded to a digital computerised ‘Glass Cockpit’ standard.

The helicopter ‘Roteables’ – principally the engines, gearbox and landing gear (the rotors are a (very expensive) lifed consumable) – are actually not integral to the aircraft, each being designed and built by separate OEMs and each with its own maintenance schedules and documentation. If nearing their TBOs (time before overhaul) they too can be sent back to their respective OEMs (not the aircraft manufacturer) to be zero-houred (ie. also, to be rebuilt to an ‘as-new’ condition) – in passing, it is worth noting that all these items, if properly maintained, can have very long lives measured in dozens of years.

So, after some six months of work and an expenditure typically of some $3m, any aging helicopter, however poor its initial condition, can be bought back to an ‘as-new’ condition, typically with similar technical guarantees as a brand new one. In addition, there are a couple of big (and positive) differences between as new and Brand-new types.

  • The first is the quality of engineering on each of these aircraft types. Brand-new aircraft are built on factory production lines, partially robotically, supported by ‘lightly’ qualified personnel essentially taken off the street and given a ‘couple’ of months training to do a single specific task. On each factory shift, typically, there are only a couple of licensed engineers (LAME) with quality control oversight over a score of aircraft.

An As-new unit, however, is hand-crafted with the same number of LAMEs on EACH aircraft overseeing technicians each normally with many years engineering experience. It is worth noting that a LAME is rather more qualified than a doctor in that it takes some 10 years to be awarded the generic licence (a doctor is 8 years). They then have to attend certificated courses on each aircraft type on which they wish to work (another 3+ months).

THEN they need to work on the type (if new to them) for a further 6 months, effectively as an unlicenced technician, in order to be awarded certification approval by the national Aviation Authority and subsequently by the AOC company for which they work. So, unlike OEM factory personnel, they know the aircraft inside-out, its strengths, weaknesses and piquilloes. In short, an As-new helicopter is a hand-crafted product, not ‘spat-out’ from a production line. I will let you draw your own subjective conclusion as to which is likely to be the ‘better’ quality product…….

  • The second difference is an ‘As-new’ aircraft is a known quantity – a specification supported by some million hours flight time globally with each unit itself will have flown many thousands of hours. So, an ‘As-new’ product has no secrets. A brand-new production build however, while benefiting from the same proven specification, will only have flown a very few hours flight test before being put to work. As a very complex piece of electro-mechanical engineering, typically there will typically be teething troubles galore as the systems bed themselves in.

Worse still, a newly developed, brand-new helicopter type will add to these teething issues, the surprises inherent in an unproven specification – unproven because during the new type certification process, each prototype only flies a few hundred hours. As such, no one knows what the future holds as early in-service units rack-up a few thousand hours (in case you missed it, you can get a lot of additional information on this in PFT-7 ‘Aircraft Certification – an uncertain compromise’).

So, not only is an ‘As-new’ helicopter type easier on cashflow, but typically, it will also be more reliable (if a bit less capable) than Brand-new and, in that there are no ‘known unknowns’, arguably a little bit safer than its glossy counterpart. OK, with respect to a corporate image and individual passenger appeal, a glossy, brand-new aircraft has its attractions. And there is merit in the argument that in a high-utilization environment, brand-new is better. But, similarly, for all the reasons stated, in a low utilization environment, ‘as new’ is certainly optimum. As such, taken overall, if you want to get a job done predictably, cost-effiently and in a trouble-free fashion, an ‘as-new’, proven work horse, is still likely the better bet.

SAF for the Savvy

SAF for the Savvy

Sustainable Aviation Fuels (SAF) is about as dull a subject as one can imagine writing about and for you, my one reader, to read. But the hype and quality of the ‘BS’ generated over it is more interesting. In elucidating on that subject, the scope of the discussion inevitably must expand into a wider environmental context and risk ecological excommunication. So here we go………

The Tropopause (the bit we breathe and fly in) is just 12 miles thick – the distance of a healthy walk. So, to keep this fearfully thin, life-giving gas veneer of the planet ‘clean’ is just simply good husbandry. So how bad is pollution today? The short answer is, that 99% of the atmosphere comprises good clean, largely inert Nitrogen (78%) and live-giving Oxygen (21%) – the other 1% is all other gases and pollutants most of which is harmless hydrogen: the greenhouse gas cocktail (CO2 / Methane / Nitrous Oxide) is less than 0.04% of that 1% comprises 25% Methane, a trace of poisonous nitrates (<0.5%) with a smidgeon of trace gases: most of that 0.04% of the 1% is the harmless human-generated exhaust gas CO2 – rather less than 400 parts per million (or 0.004% – statistically speaking not a significant number). So, in short, the air we breathe (taken overall) appears to be in good shape.

So, what are the environmentalists screaming about? Based on the above, it would appear that they live in a self-inflating bubble, apparently headed in social media by an articulate teenage Jeanne d’Ark battling the Barons of industry knowing little of the messey realities of this world. From within the security of an upper-middle class Nordic family, this environmental heroine rallies her virtual green army of well-meaning lap-top environmentalists – a vociferous media-friendly amateur among hard-bitten but no less shrill professionals – all creating a lot of noise signifying nothing that holds deductive reason. But like during the Covid pandemic, the multi-media cacophony makes it hard for politicians to think straight. That one is an environmental cynic is a function of the apparent self-serving nature of these practitioners. Their cultivation of the concept of ‘Global Warming’ – that element due to mankind’s impact – appears to be more of a carefully nurtured hypothesis, now not so different to a religion – developed by men of faith, stating fiction as fact, and making a good living from it.  

That said, climate change is an indisputable fact: there is absolutely no doubt that planet earth is warming.  It is a singular and undisputed FACT that there is a 100,000-year sun-cycle due to the elliptic path of the planet’s solar orbit. Today we are some 15,000 years into the warming phase after the last Ice Age – the so-called Inter-Glacial period – as the planet slowly gets closer to the sun. This makes it very likely that the principal cause of this planet’s warming is astronomical not chemical. The graphic below on the right shows the change in concentration of CO2 in atmospheric air bubbles over the last million years taken from ice cores in the Artic and Antarctic regions: this is clearly cyclical and sinusoid. The changing concentration is a function of Dalton’s Law of partial pressures. In this, the concentration of the cocktail of gasses that make up the 1% of the atmosphere that is not Nitrogen or Oxygen, increases with temperature – the graphic below is just the CO2 element.

The figures showing the CO2 concentration in the left margin of the graphic appear enormous until you read the small print and see they are parts per million: so that massive spike right at the end on the right-hand side, that is causing such angst in the environmentalist community, represents an increase of 200 parts per million or 0.002% – so don’t panic!!! And, with a 100,000-year spacing on the horizontal axis of this graphic being barely one centimeter, inevitably a 50–100-year timeframe will appear vertical and, possibly (ok, not surely), might be an aberration that would, in such circumstances, disappear when smoothed-out over the 100,000-year cycle.

The Environmental lobby talks in billions of tonnes of CO2 pollution in the atmosphere which sounds terrifyingly impressive, until one realizes that all those billions represent less than 0.004% – a statistical non-entity. And, as explained in the next paragraph, there is surprisingly little science to demonstrate that a trace substance in such a minute quantity (in percentage terms), can have any impact on anything.

That greenhouse gases warm the atmosphere by absorbing Infrared energy is not in dispute – recent experimentation at the Max Plank Institute has clearly shown that, as does the above graphic of the CO2 density cycle. What is more doubtful is the impact of CO2 as an atmospheric trace gas at 0.004%. Making an AI-BOT research on the experimental evidence for this, produced information on observations made with respect to the Pliocene era (3-5 million years ago) when CO2 was at similar or greater concentrations. A further input into the AI-BOT that his was an observation, not experimental, the AI-BOT ‘agreed’ and could only find a single experiment, recently conducted at Harvard in 2015 which showed that even at that low concentration, ‘significant’ quantities of IR radiation are indeed absorbed causing the gaseous mix to warm. The experiment does not appear to have specified or quantified the degree, merely confirming the common experience that in sunny climes, IR radiation warms anything in its path. As to the former observation, with the Pliocene predating mankind altogether, this simply demonstrates the wholly natural character of the increase in CO2 density in the atmosphere that is being experienced right now.

But I disagree: all this is only the background to the argument here, namely the environmental impact of the polluting gases from the efflux of aircraft jet engines. How bad is it?

The graph to the right shows the environmental impact of the whole hydrocarbon sector, now producing some 10 billion tonnes of CO2 pa. Of that, only one third appears to be from ‘engines’ (the blue petroleum line), and of those engines, the few hundred jets touring the globe each day are, but a relatively small element compared to the tens of millions of cars clogging up metropolitan streets around the globe. And if the other two-thirds of hydrocarbon gas and coal elements are also considered – in the main used in the production of ‘clean’ electrical power – the aircraft emissions become even less significant.

Yet, 10 billion is a very large number and in tonnes of anything such is huge but let us put that in perspective. Each of us, through respiration, on average produces about 1kg of CO2 per day. There are now 8 billion of us. So that equates to some 3 billion tonnes of gas each year – almost the same as all the powered motion machinery on the planet, of which the high-profile aviation element is, in truth, only a relatively small part. But, in bowing to multi-media pressure, would the use of SAF in place of Kerosene have any impact on the issue of limiting greenhouse gases or the pragmatics of atmospheric husbandry.?  The short answer is ‘No’.

It is claimed by the environmental clerics (…. sorry, lobbyists) that SAF offers – and here I am quoting BP – an 80% reduction in ‘lifecycle’ carbon emissions as compared to jet fuel (which I reiterate is but a small element of a minute portion of the greenhouse gas problem).  The important word here is “lifecycle”.  Being drawn from the green of pleasant lands and human waste, SAF is still a hydrocarbon so, like kerosene, its exhaust will still flood the atmosphere with CO2, water, and noxious nitrates – that is by the very nature of the natural components from which it originates. It’s just a question of vintage. Those in kerosene are of a several million-year-old vintage – that in SAF is ‘benzene nouveau’. They are essentially the same, the younger vintage perhaps being cleaner and ‘fresher’ (like Beaujolais Nouveau wine, a question of taste if you will) in that, as stated, it is produced from current environmentally friendly vegetation and human waste (admittedly the latter element being particularly good news).

The energy-heavy processes that get SAF from ‘waste to wingtip’ (a great marketing lyric that!) and the associated energy outlay, are similar to those pertaining from ‘crude to kerosene’ (my factual lyric!). So, the science supporting said 80% reduction is likely more related to the math of carbon credit calculations (with electrical production from sustainable sources) than the nature of the polluting chemicals released in the jet efflux from the useful generation of energy from SAF. In short it appears to be little more than a clever, if harmless, ploy to keep the crusading hordes of the environmentalist army at bay until hydrocarbon power sources in aircraft can be replaced with hydrogen and (maybe) electricity. This is reflected in the aviation industry itself in that no serious R&D has been allocated to optimize the production of SAF or its conversion to energy in engines. This is in part evidenced by a recent report in the Air transport Digest (an Aviation Week magazine) that the US government Audit Office (GAO) has discretely recovered some $200m set aside by the Pentagon to assist in the general development of SAF production facilities.

Instead, the industry R&D focus is on the more worthy zero-emission hydrogen and electrical propulsion systems in the next generation aircraft.  And this will happen, likely in a 15-year timeframe. ‘Green’ Hydrogen, electrolyzed from water or other sources, is designated thus because the electricity to extract it, is sourced naturally from Hydro, solar/wind, or geothermal power.  In that, unlike SAF, the fuel efflux comprises only clean water, this will, in an environmental context, truly be a fundamental game-changer and therefore worthy of such focus.  One challenge with hydrogen is its high volatility – storage is mildly challenging but the crash case in the aircraft that it is powering, is more thought-provoking. Counter-intuitively, initial studies show that hydrogen fuel is less dangerous than kerosene. For while very much more volatile, being the lightest of elements (Atomic Weight – 2) it is also very much less dense. Being stored at high pressure, in the event of tank rupture, the massive jet of the gas that will shoot out will always be in the vertical. It has been shown that this vertical sheet of flame, while very hot, immediately dissipates. As such, its impact is very much less than that of a pool of burning viscous liquid fuel typically emanating from the ruptured wing tanks of a conventional aircraft accident – be it kerosene or SAF. For all these reasons, the environmental impact of using SAF in place of kerosene is negligeable while that of ‘green’ Hydrogen will be considerable.

Returning to a more general environmental context, the negative raving in this piece is not to say that climate change should be ignored. Of course not! It is rapidly topping and tailing the planetary ice caps which, whatever else, will raise global sea levels by a meter or more, which is an existential threat to, maybe, a billion people. What has changed in this, our current sun cycle, is that, the last time around, mankind was numbered in millions and, like every other species with which they shared the planet, they were nomadic, hence upwardly mobile.  So, as water levels slowly rose over a few generations in some areas and desertification occurred due to drought in others, all could easily migrate to greener pastures. Today the issue is that, as a function of numbers and our technological advances, the fixtures of our metropolitan civilization and the associated agrarian infrastructure has made us all – man and beast alike – more or less immobile. Hence, faced with the fact of climate change, the emphasis should logically be on protection from its effects rather than futile ‘Canuteian’ attempts at its prevention.

But, given the current latter focus, what can be done to prevent the snail-paced inevitability of this environmental tsunami? Sustainable energy from renewable sources, while largely an irrelevance in this specific context, in the perspective of good husbandry with respect to the thin veneer of the planet’s atmosphere, it is surely worth pursuing. Of more significance is Nuclear Fusion which is now expected to start powering the grid by 2050 thus providing a perfect, sustainable, and unlimited power resource. Taken together, the imminence of these two, deeply green sources of energy, reduces global warming from an existential matter to one of a serious short-term safety issue. Given the imminence of a truly effective fusion solution, like all safety matters, controls and mitigation should meet ALARP (as low as reasonably practical) criteria.  The commercialization of renewables surely meets that criterion: but tinkering with aviation fuels, while a harmless distraction, is essentially a wasted effort and anyway, a total irrelevance.

In passing it is worth highlighting the imminence of fusion power. For more than a generation such has been 10 years away – this may now finally be the case. An outfit in California (Tri Alpha Energy – TAE) expects to have a prototype system capable of producing net electrical power in 2025, with a production prototype in 2035 and OEM supply connected to the grid five years later producing unlimited, (eventually) inexpensive, emission-free (truly green) power source to drive the planet. Such will solve the whole greenhouse gas issue, clean up the planet’s atmospheric veneer and finally put my environmental lobbyist nemeses out of work.

Tinkering with greenhouse gases (should such, at a density of 0.004%, actually be a problem at all!) won’t change that. A measure of the futility of such ventures has been demonstrated by the Shell petroleum company (hence possibly not without some bias) which has shown that carbon capture through current methods of sequestration of the CO2 produced by the hydrocarbon sector alone each year would require some 66 exajoules (that’s 18 zeros!) of energy – or enough to heat/cool all the world’s homes). While such a comparison lacks indisputable clarity, it clearly shows the futility of such politically correct ventures and, unless this associated electrical power is sourced solely from green energy, it will anyway only be exacerbating the problem!

Aircraft Certification – an Uncertain Compromise

Aircraft Certification – an Uncertain Compromise

Stifle your initial yawn – our lives depend on a technical oxymoron of innovation & certitude.

You have surely wondered at the checks & balances, the machinations & controls that go into realising the approvals on the aircraft in which you fly. Fear not – they are extensive, but fear(!) – inevitably there is an element of compromise.

First and foremost, aircraft certification is not given in the belief that it will prevent accidents. Anything that defies gravity and leaves terra-firma, is certain, now-and-again, to come down unexpectedly and with a big bump. The aim of regulatory authorities is to seek to minimize design and human error as a cause, and to put controls in place by exacting technical and operational systemization. But as is now common in any risk analysis, acceptable risk is not zero risk.  In aviation it is 0.002%. In other words, when you fly you have a 99.998% of reaching your desired destination (albeit, not always in a timely manner !!). As a measure of overall safety, this far exceeds that of ground transportation that you use most days. But, notwithstanding this elevated targeting, the process is not without surprising discrepancies.

The world of aviation is based on a baseline set of regulations (in massive tomes) drawn up by the International Civil Aviation Authority (ICAO), now effectively the aviation arm of UNO (the United Nations). Dull as puddle water, its origins were a riveting bit of history, dating back to 1944 during the still uncertain and intense hostilities in the latter years of WW-II.  

Recognizing that aircraft now transporting bombloads of destruction, would one day carry passengers and freight in similar quantities, all parties to the war gathered in Montreal, Canada to agree a set of baseline regulations for the conduct of commercial aviation once the war was over – whoever won it. The logistics of getting everyone to that meeting and the underlying diplomacy which produced the final declaration (below), is as extraordinary as the regulatory document is dull – and it is very dull! Also, to this day, ICAO remains based in Montreal.

On that foundation three main aviation genus have evolved, inevitably based aviation hubs of design, innovation, and manufacture – the American FAA, the European EASA, and the Russian ‘WhatevA’!  Roughly 90% of aviation is controlled by the first two and that in most of the former Russian empire (the USSR) by the latter. As is true for most things Russian, the devil is in the (lack of) detail. That doesn’t make Russian designs bad – indeed they build robust aircraft, particularly helicopters. But historically lower levels of control and verification have led to higher levels of risk**, albeit matched by significantly lower cost of purchase (an 18 Pax. helicopter in ‘the West’ costs more than 5 times that of an equivalent manufactured in Russia).  Fortunately, now (or at least until the invasion of Ukraine), with most commercial aircraft operated by Russian airlines being of western manufacture, there is a better alignment in accident statistics.

(**By way of example, there are similar numbers of aircraft on the Russian and UK registers but, over the last 50 years, with more than five times the accident rate in Russia)

Not surprisingly there is a high level of commonality between the two western systems which themselves form the basis of most other global national regulatory practices (even in China) – with nations’ choice of US or EU alignment typically being based on countries’ historical alignments.

So, the regulatory big picture is multi-tiered. ICAO approves a country to operate the aircraft on its register internationally but has no control, only influence, in what goes on within each country’s internal airspace. There, the National Civil Aviation Authority, going under many different names, but to which here we will refer as ‘the NCAA’, certifies each air operator by periodic award of an AOC (Air Operator’s Certificate) and each registered aircraft by issue of an annual CofA (Certificate of Airworthiness). You’ve guessed it – the potential for corruption is rife!!  And there is another issue, the dual hatted nature of NCAAs – to both promote and to regulate their national aviation industries. These two roles are, in the main, incompatible and is an issue that remans largely unresolved as exemplified, in part, by the Boeing Max-saga discussed in an earlier article on this site. As such, while the regulations are based on the ICAO baseline with FAA or EASA alignment, the quality of the detail and consistency of its implementation by NCAAs varies enormously.

The principal control in this regard is ICAO through a single sanction – the right to deny corrupt nations’ aircraft the right to use international airspace. Of course, they don’t shoot down a sanctioned nation’s aircraft if they stray outside their national airspace, but ICAO can decertify any international airport which allows them to land – a fully effective commercial sanction. Unfortunately, such NCAA declassification by ICAO is only used in extremis, with less than a dozen (mostly small and backward) countries thus black-listed.

The certification process, like everything in life, is subject to financial limitation. In all aspects of regulation, there is just not enough money available to do things ‘properly’ across the board. So, under ICAO rules, the regulatory focus is on the carriage of passengers. Hence, as a general principal, the less the passengers on an aircraft type or mission profile, the less the regulation. This is reflected in the ICAO specified levels of certification, with increasing degrees of monitoring at each level along these lines: –

  • Experimental – this is what all aircraft fly under during the certification process under FAA/EASA. Aircraft are limited as to when and where they can fly, what flight profiles are followed and with whom on board. Each series of test flights is endorsed by the National Authority with approvals of subsequent steps being subject to the reporting of the previous series. Some wild things can go on within this category and it is here that most aviation technical development occurs.
  • Aerial Work – this is the lowest level of certification under which aircraft can fly ‘for hire & reward’ basically only for freighting or specialist missions. Pax. on board are limited to crew members. This includes such things such as cargo carriage, heavy-lifting, forest firefighting, logging, aerial advertising, aerobatics, paramilitary agency marine surveillance and pilot training. Transport Category aircraft (see below) can recertify themselves at this lower level to do specific jobs. So, if you want to do something ‘extra-ordinary’ with an aircraft, this is the way to go.
  • Transport Category – this is for the carriage of fare-paying passengers (Pax.) and under ICAO regulations is evidently the most highly controlled. However, within a national context, this again is to various levels.
    • Part-91: is for private aircraft servicing a restricted & specified range of Pax. such as corporate business jets, flying clubs and the like. Controls & limitations are kept to a minimum, it being very similar to Aerial Work. Even more lofty service providers such as Airforce-One in the USA and the Queen’s (now King’s) Flight in the UK, nominally are also likely to be operated under this category.
    • Part-135: is for General Aviation (GA) including all charter operations. So if a business jet is offered for charter, it must upgrade to this level. On the technical side, the level of service provider surveillance and controls is essentially the same as Part-121 (below) but with less stringency on operating criteria and passenger controls.
    • Part-121: is for Commercial Aviation. As such, any Airline accepting ad-hoc, fare-paying Pax., must operate to these most stringent criteria where everything is done to the highest standard, in accordance with a proscribed and documented methodology from which no deviation is permitted.

Not surprisingly, the US-FAA and the European EASA use the same certification benchmarks, but separately developed.  But with their respective aircraft designs now only differing in the detail, the two set of regulations have steadily become more aligned to the point of being almost identical. Only the Russians hold out to their own (lack of) rules and for that reason, while designing robust and relatively inexpensive aircraft, they can only use them for carriage of Pax. within their (albeit massive) national borders. As yet, and not for want of trying, none of the established Russian-built airliners have achieved EASA/FAA certification standards. However, a new generation of Russian (and Chinese) aircraft designs are stumbling uncertainly towards that goal.

The big difference between EASA and the FAA is in the method of certification of new aircraft types.  The US-FAA is a tortuously labyrinthine bureaucracy, while the Europeans, while still ever the bureaucrat, the style is more corporate than governmental. So, while in the US certification is at fixed rates based on the nature of the task, in Europe it is man-hour related. So, while this makes European certification more expensive (which, since the OEMs there have access to low-cost government loans, to the fury of their US competitors, the European counterparts can afford), it is also quicker and more adaptive, as the Authority is as much a Service Provider as a Government Agent.

The Brits (as is their eccentric way) have taken this to an extreme. In the 1930s, as aviation became a mainstream service and the government sought to legislate, the industry kicked back and formed a self-regulating body – as such the UK-CAA fulfils the same regulatory role but, as a Non-governmental Organisation (NGO), it is largely funded by the industry it regulates. As such, in the UK, certification is a contractual task with obligations on both sides and the ability to sue if the Regulator fails to provide the agreed certification within the contracted timeframe.

As a result, while with EASA and the FAA, the onus is on the OEM to demonstrate that a product is safe, in the UK it is the other way round, with the onus is on the CAA to substantiate that a product is unsafe to require its modification. The path to certification in the UK is thus surer, but a lot more expensive. The one bonus of FAA certification is that the experimental category which, being a domain dominated by DARPA (the Defence Advanced Project Agency), extremes are acceptable. The European experimental counterparts are typically more conservative. It is for this reason that the USA now leads in most aspects of aeronautical development.

Underlying the above systemisation and controls are financial realities – money still talks! In truth, no electro-mechanical device testing and certification is fool proof. But at least in cars it reflects the vehicles’ guarantee period. With aircraft, as a function of operating costs and development timeframes, the level of testing during the certification process gets nowhere near to this. Typically, the process from first flight to type certification takes some 3-5 years and with barely a couple of a thousand hours of test flying – and with the latter flight hours typically spread over several test aircraft (hence, with only a few hundred hours on each unit).

This is driven purely by commercial pressures and ALARP principals.  So, notwithstanding certified airworthiness by the FAA/EASA, the parties in the sale any new aircraft type, will have little idea of what will happen in the latter part of the 5 year or 5000 flight-hours typically covered in an aircraft guarantee period, and not an inkling of what might occur thereafter (a typical aircraft life being some 30 years and/or more than 40,000 flight hours – choppas rather less). So, even the best and most exacting of aircraft designs can have awful incidents.  

An example of this occurred in one of the most powerful, hence safest, of helicopters. Having passed the normal certification process with flying colours and taken the market by storm, as a function of its very high-power output, after 3000+ hours of flying a few individual aircraft experienced serious tail-rotor problems with a few of them dropping-off in flight!!  With the half-dozen test vehicles each having only flown less than 1000 hours under test, there was no way such failure could have been reasonably predicted.

A detailed design review immediately imposed by the OEM Regulatory Authority quickly produced an effective solution, and there have been no problems since.  But sometimes, driven by commercial pressures, technical solutions can be fudged. There is an example of a much-used Part-121 Airliner flying to this day with such an egregious compromise. Like any cell phone its lithium battery at the core of the electrical system risks severe overheating and associated fire-risk. The Authorities of course suggested a different battery be used.  However, there was none on the market with the required capability and output. Such predicated a restructuring of the aircraft electronic design which at such a late stage in the certification process was commercially unthinkable. The fudge therefore was to accept the risk but to mitigate it by locating the battery in a specially designed fireproof compartment. So, to this day, hundreds of these airliners are flying with a potential fire-bomb encased in its technical core.  While such has been shown to meet acceptable ALARP and Risk Management criteria, subjectively it is somewhat unnerving and clearly shows the financial constraints on the certification process.  

Unfortunately, almost every new aircraft type experience something similar. Regulatory Authorities therefore oblige and formalize the end-user community reporting of all failures and, where deemed a risk to flight safety, aircraft by type or batch can be immediately grounded by issue of an ASB – Alert Service Bulletin (ASB) – by the manufacturer. This is then rapidly endorsed by the OEM Regulatory Authority by issue of an ASR (Aircraft Servicing Requirement) or an AD (Aircraft Directive). These remain in force until the failure is corrected or mitigated. Typically, this will be measured in days or weeks, but in the case of the B737-Max, it took almost two years.

And talking of the Max., one of the aspects of this sorry tale that the scandalising multi-media made a feast of, was that the OEM Quality department did many of the FAA certification tasks in-house. This was seen as corporate duplicity. It is, in fact, a norm throughout the aviation industry.  The FAA annual budget, along with every other NCAA in the world, is insufficient for the task.  So, there are never enough inspectors not least because, anyone qualified for that role, can earn a lot more money in the commercial sector that is being inspected – so there is no waiting list of applicants. As a result, QA (Quality Assurance) managers world-wide are twin-hatted, reporting both to the CEO of the Airline and the Technical Directorate of the NCAA. 

This works because it takes a lot of graft to get an engineering license – at some 10 years, it is significantly longer than, say, a doctor: and a QA license is only awarded to folk having many years experience in engineering management.  As such, it is effectively the top of the technical tree, and no-one there will allow an ‘amateur’ CEO/CFO to put his valuable and hard-earned license at risk by demanding he cover-up any incident that may occur within an air operator! The Boeing Max saga was a very rare exception to this rule.

In summary, the only way to guarantee safety in aviation, is not to fly. So, while the process of aircraft certification is far from flawless, the systematic and frequent checks and balances of every process, and every electro-mechanical part of an aircraft, ensures that the level of risk is significantly less than that relating to an outing in your car. But systems are only as good as the humans that implement them so, as on the road, one should keep a beady eye out for folk who do not look after their vehicles properly!

An Unexpectedly Safe Place – Part 4

An Unexpectedly Safe Place – Part 4

Summary – It is a pleasing paradox that possibly the least preferred seat on a commercial airliner, is probably the safest one.

But to begin with a few general words on seats. Firstly they, along with the interiors of all aircraft, are not actually made by the aircraft OEM but by specialist companies that compete to supply aircraft interiors. That said, Boeing specify an economy seat that is a couple of centimetres less wide than that of Airbus and with a 28” separation – the so-called seat pitch – (Airbus specify 30”) to squeeze in a few more passengers into their slightly smaller airframes. Small difference maybe, but over a 3–5-hour flight this makes a big difference.

Then there are some interesting technical issues.

  • Firstly, on most aircraft, seats are certified to carry 150kg which is surely the 99-percentile man – that he will anyway likely overflow the typical 18” width of a Boeing economy seat, offers two justifications for airlines’ wishing to charge for two seats under those circumstances.

    (Note – in our OGP charter world, it is also worth noting that cargo can thus be secured into seats using the safety harness: a seat cares not if cargo is self-loading with two feet or static and placed there by a third party).
  • Today seats are now stressed to 9’gs (9 x gravitational pull) – it used to be 5. All well and good but at those forces, unless an astronaut or fighter pilot, Passengers will anyway most likely be unconscious!
  • More importantly, in the event of such ‘9g’ crash, if not actually cut in two by the lap strap, folk will suffer such bad organ damage that, in the event of survival of the event itself, an ensuing slower death is assured. A shoulder strap (better two) is a lifesaver. Such has always been known but, until now, only airline staff have been thus privileged (and, most recently, First & Business class also).
  • The seats also face in the wrong direction. In the event of a crash, aft facing seats would largely mitigate the above two problems, increasing the chances of survival significantly. Airlines don’t do anything about this principally due to a perception that passengers like to see where they are going. And then there is the cost. Sadly, one cannot just turn the seat around – the seat structure is completely different. To do so on a new aircraft type would be easy, but that would highlight this safety issue: for any airline, the thought of then having to retro-fit the rest of a large fleet of in-service older aircraft will assure that this, and shoulder harnesses, will never happen – in coach anyway…….!

As stated above, in airline manufacture, unlike cars, the OEMs do not fit the interiors. This is done by specialist service providers contracted directly by the end-user airlines and to design limitations set, and overseen, by national regulatory authorities.  So, this element, so fundamental to an airline image and passenger satisfaction, has little to do with the aircraft OEM. It also represents only slightly more than 1% of an airliner’s cost.  Indeed, while on the subject, with respect to airliner cost, OEMs are directly responsible for the manufacture of only about a quarter of the end-product. Having developed and certified a new design (at huge expense) they actually only build the cockpit and hull structures and sometimes the wings and tailplane. The rest is furnished by other specialist service providers and only bolted on, or fitted into, said hull by the aircraft OEM. As such, were an aircraft manufacturer to go bankrupt or withdraw from the market, the impact on their aircraft end-users is little more than an administrative inconvenience.

 In previous articles we investigate how airliners are controlled of which increasingly, the near-total reliance on digital technologies, makes gloomy reading for analogue man. It also makes the subject at hand, namely, the safest seat on an airliner if one of these flying whales goes out of control, a subject of considerable relevance.

In first class one pays for luxury, a premium service and to be the first off, the aircraft: but one is also the first to die. The cockpit module is manufactured separately to the main hull onto which it is bolted. It is a very strong structure, with significantly higher stress tolerances than the main passenger carrying hull, and into which, in the event of an emergency, most of the working crew strap themselves (using said four or five-point seat harnesses).  The rest of the hull, where we the fare-paying, single lap-strapped masses are seated, is relatively flimsy in comparison. So, in the event of a crash-landing, it is certain that the hull will concertina into the strongly reinforced cockpit section, thus crushing to death all those high-paying premium flyers at the front.

 Business class passengers are even worse off because, in addition to the crushing element described above, they are in the vicinity of the wing in which many hundreds of gallons of flammable aviation fuel are stored – so for them crushing and incineration are in delightful prospect (typically not highlighted in the glossy advertising). And if that wasn’t bad enough, any very dangerous cargo goods (DG) needing transportation are typically loaded in the wing box section, it being the strongest part of the hull hence, in the cargo area beneath the business class seats. Such cargo includes killer viruses, poisonous gases, explosive chemicals, and even radioactive waste to name but a few of the more delightful possibilities. This is due to the considerable bulk and associated greater weight of the DG packaging, which, of necessity, needs to be located near the aircraft centre of gravity and in the strongest part, of the hull – and one pays a significant premium for the privilege of being seated above this refuse…………?!

The high passenger density in economy, inevitably, is an inherent danger. But the biggest single hazard are the overhead baggage bins. Their design specification is to 7kg per pax – need one say more………?  The effect of the almost universal abuse of this baseline criterion is that, in the event of a crash, the locker structures are overwhelmed by the force of the impact and come crashing down with great force, mercifully breaking the necks of virtually all beneath.

 Only one row of seats remains completely unaffected by this mayhem – the back row. With it being located forward of the toilets, and with the lockers above usually taken over by the cabin staff and blessed with a general ‘pocky’ seat appearance, such makes this place less than a ‘des-res’ for the duration of any flight. But consider this. When those overburdened overhead lockers come crashing down, the forces of impact will also direct them forwards in the direction of flight. Hence, those in the last row will, typically, not be ‘topped’ by the falling overhead bins. Far from the wings, neither will they be burned to death. There is also no cargo space in the tail, so the horror of DG is not an issue. Finally, as the hull concertinas, it whip-lashes and weakens, often causing it to break, typically some three-quarters of the way aft. Hence, those passengers still alive in the broken tail-plane unit (typically, only those in the last row), will likely be able to simply walk or swim out of the open hull.  A recent example of this was in an Eva Air crash-landing at Los Angeles whereby the tail fin unit broke off, spinning across the airfield. When it came to rest, the four Flight Attendants strapped in their seats in that section (of course, with their 4-point harnesses) simply got out and walked away without even a bruise to show for it.!

The (less) good-old days….

Tail seat on WW-II Bombers with Elsen toilet
Imperial War Museum Collection

Today – good seats, better Toilet

Turkish Airlines Brochure

Back against the wall

Daily Mail Newspaper

So, safer though it may be, when should the use this essentially undesirable seat row be considered.? Firstly, for any airline, when there is an expectation of heavy rain, or worse still, heavy snow, at the destination airport. In such circumstances, it is possible that a combination of minor piloting errors, possible gusting crosswinds and/or heavy braking on a slippery runway surface, is a quite frequent cause of runway excursions into the grass or worse.  In a more general context, the discomforts of the rear row should also be considered when using airlines in developing countries and with all but the largest LCCs (low-cost carriers).  

For LCCs this is not a structural issue.  The cost and method of operating a given type of airliner is very much the same whether operated by an established legacy airline or an LCC – the substantial fuel costs are exactly the same. Hence the savings necessary to reduce (LCC) ticket costs, in addition to slashing administrative overhead and infrastructural elements, are found largely in three ways – all with negative attributes in a safety context.

Firstly, in the use of lower capital cost (i.e., older) aircraft which typically are using previous generation flight technologies and inevitably which, through wear-and-tear, are more likely to suffer unscheduled technical events. Similarly, by maximizing aircraft utilization, through reduced turn-round times, can only have negative maintenance implications.  And thirdly, crew costs: experienced pilots will generally seek to work with legacy airlines where pay and perks are better. So, by dint of lower wages, LCC airliners are flown by less experienced Captains and First officers, the latter, on occasions, almost fresh out of Pilot school.

In terms of general safety, all the above are negatives. Hence, by way of mitigation, to subject oneself to the minor discomforts of the last row for the couple of hours of a short-haul flight makes good sense. And there are positives. LCCs generally forgo the use of flying bridges resulting in the back row passengers being among the first off the aircraft and onto the bus using the rear doors. Further to that, the back rows of economy, along with the front rows, are also generally the first to be served. Finally, one is near to the location where flight attendants are typically hiding when ignoring the passenger staff call button, making them more responsive to a good-old analogue shout which is more difficult for them to ignore!

In short, notwithstanding all the negatives highlighted above, the chances of a flight accident are minimal – travel on roads is significantly more dangerous. But, for any given flight, should the negatives impacting safety be perceived to increase, just as in the workplace, mitigating the associated risks, even if a cause for minor discomfort, is simple common sense.  

The B737-Max Saga – A Technical or a Management Failure ? – Part 3

The B737-Max Saga – A Technical or a Management Failure ? – Part 3

Summary – In previous articles we discussed automated flight systems in general. In this article we examine in detail a nominal systemic ‘tweek’ in the flight automation by Boeing of their dominant 737-series regional airliner which has developed into a major scandal. Boeing is as synonymous with commercial aviation as Bell is to helicopters. They invented the quality systems on which ISO-9000 is based. So, how is it that they appear to have lost the plot in this regard? It is a long story, so we have done it in three parts. The first was a brief history of how the Boeing Aircraft Company achieved total market dominance: the second analysed how this hegemony has been successfully challenged by Airbus. This final article is an analysis of how the useful MCAS concept became a killer.

Part-III:  A Technical Fudge (Sales wags Engineering)

In the first two parts of this article we saw how the Boeing Aircraft Company changed its core value from engineering excellence to optimised financial management, supressing technical innovation and excellence to favour of the bottom line to become a Wall Street darling. This allowed their rival Airbus in the last 10 years to assume the lead both technically and commercially. While just holding their own in the wide-body market, in the larger narrow body sector, Boeing are getting trounced. Having neither the time nor the money to bring a new game-changer design into play, they opted instead to seek to match the competition by re-engining the venerable 737 design with a new, fuel-efficient, by-pass engine type. However, by its very ‘by-pass’ nature, the new engine was significantly larger than its direct-flow predecessor powerplant and thus no longer fitted in the space under the wing. As described in the second part of this series, it was therefore moved forward and raised on a structural pylon. This changed the aerodynamics of the aircraft, risking a stall condition at high power settings. This negative and potentially dangerous impact was overcome using technical trickery, MCAS – Manoeuvring Characteristic Augmentation System – a simple but clever automated device to overcome this negative aerodynamic norm at an insipient stage. The new powerplant, combined with a unique winglet design to maintain laminar airflow on the wings, increased the efficiency of this new 737 iteration by some 20%. However, while looking much the same as its 737-900 predecessor, it was arguably, a new aircraft type.  But to minimize the requirements relating to the associated certification and subsequent conversion-to-type for the client airlines, the Sales department was allowed to obfuscate and minimise the engineering issues. The result was bumper sales – a commercial triumph – and an latent disaster.

Airbus & Boeing - head to head adversaries

Airbus & Boeing – head to head adversaries

The latter demon soon woke. Within a few months of entry into service, a Lion Air Max crashed into the sea shortly after take-off from Jakarta on a mild day with light breezes. With the Captain being a foreign national and the co-pilot relatively inexperienced, it suited both operator and manufacturer alike to initially blame it on Pilot error. While the detailed accident investigation followed it’s protracted course, that was the generally accepted view in the aviation industry. But then, just five months later, a very similar accident occurred in Ethiopian Airlines, also just after take-off and also in fair weather. Now, while Lion Air is an LCC in a poorly regulated developing nation, the national airline of Ethiopia is highly respected internationally, being run to very high standards by a bunch of experienced expats from the developed world. So the event was not so easily fobbed-off. As a result, led by the Chinese, more and more developed nations grounded the Max. The last to do so was the USA and then only after the Pilot’s Union wrote an open letter to the President of the USA resulting in it being grounded, not by the FAA, but by a Presidential Decree !

The root cause in each case was eventually found to be a failure of an angle of attack (AoA) indicator. This is a simple mechanical pendulum device allowing the easy measurement of aircraft flight angle relative to the horizontal, hence the aerodynamic Angle of Attack – (AoA).  In the Ethiopian accident the sensor was found to have been broken by a bird strike: in Indonesia, with the unfortunate aircraft having plunged into the sea at very high speed, no definitive prognosis could be made, but it was considered a reasonable assumption. Bird strikes are common hazard in aviation, so the two events could be considered appalling bad luck. But, as the investigations proceeded and multiple other casual factors came to light, it started to become abundantly clear that appalling management at the OEM was equally to blame – and herein lies the scandal. This has been exposed in an excellent Netflix documentary – Downfall – by Rory Kennedy (yes, of ‘that’ family) issued late in 2021 and on which much of this thesis is based. The failures cover almost every aspect of management within Boeing!  Let’s start with the technical.

In fully automated systems, everything must be duplex: if safety critical, then it’s triplex. The AoA indication, being the fundamental driver of MCAS, is surely in the latter category. Yet it was simplex! There are actually two such AoA sensors (to left / right of the nose) but no software provision was made to cover one or both failing except for a computing anomaly indication – thus effectively making this safety critical element simplex. At the time of writing, one can offer no logic for such a fundamental error: maybe it was a just factor of the sensor’s simplicity in that, being little more than a plumb line, it is was considered that there was nothing there to fail……. That said, with man-in-loop (an earlier article – PFT-2 – on Flight Automation refers), it would not in itself have been a big deal as the MCAS element could just be switched off and the aircraft flown manually.  

It is here that the second root cause, of commercial sales wagging the technical dog, came into play. There were two main issues. Management wanted a speedy certification process to get the aircraft into service as quickly as possible so as to better compete with the A320-Neo family; and the Sales strategy was to minimise the conversion to type for B737-800/900 pilots (again emulating said 320-family) to be little more than a in-house computerised aircraft differences training, with a standard line check by an authorised airline Training Captain on completion. This was to avoid the training typical for new aircraft types requiring pilots to fly to the USA for a couple of weeks conversion Training with the OEM and the need to build specific simulators to accommodate the emergency aspects of that training.  If conversion to the new type could be accommodated within the existing infrastructure, then time-lines and costs bringing the new type into service would be dramatically reduced for both the OEM and end-user Operators.  

So the OEM management decision was to ‘hide’ the MCAS within the existing auto-pilot as an auto-stabilization element (which, in effect, it indeed was).  As a result, it was not documented in any detail anywhere – not in the Pilots’ Ops. Manual, not in Technical Manuals, nor even in cockpit checklists. This technical subterfuge was so complete that the only mention of MCAS in all of the technical and operational documentation was in the Glossary of Terms at the very beginning of every Manual. (Typically Glossaries, being common to all the various Manuals pertaining to any aircraft type, are kept as a separate computer file).  As such, with all reference to MCAS removed in all other Manuals and Checklists, it appears to have been left in the Glossary by oversight – effectively a “typo”.  Such is indicative that, decisions with regard to the technical strategy of eliminating all reference to MCAS in both technical and operational Manuals and cockpit check-lists, was taken at the highest levels within the company.  In fairness, there is a logic in this regard, in that the automated elements were really very simple and, as long as there was no failure, the system inputs were so deeply embedded in the aircraft’s operating system, as to be unnoticeable. So MCAS was presented as a software ‘tweek’ to make this Max ‘feel’ like its 737-800/900 predecessors, which indeed, was essentially the case. The Wall Street Journal subsequent investigation as to its lack of elevation, advises of a Boeing statement being made to the effect that it was company policy “not to overload Pilots with too much information”!  As a result of this Sales ploy, no mention was made of two simple switches labelled ‘auto-stab.’, that would turn off the MCAS in the event of a software problem.

Rory Kennedy’s Downfall documentary includes footage in a simulator showing what happens when the AoA indicator fails. The effect of the broken mechanical sensor meant that, in maintaining a mechanical vertical, the  pendulum fed an apparent high nose-up input into the FMS computer: such is indicative of a stall. This causes various panel lights to start flashing, the (joy) stick shaker activates, a voice screams “stall, stall !” and the computer brutally shoves the nose down. The flying pilot, seeing that the aircraft was in a normal flight condition, pulls the nose back up manually and the cycle restarts again getting more brutal each time as aircraft speed increases. The non-flying pilot frantically searches through checklists for information – there is none – thus  leaving the crew trying to understand what heck was going on as they loose control of the aircraft in a cacophony of cockpit noise, no doubt further exacerbating matters, resulting in other mistakes. Such is the stuff of nightmares but, as a reality, there was no waking-up in a cold sweat, just a mercifully short screaming panic and oblivion…………  

Actually all that needed to be done was to close the aforementioned couple of normal looking switches labelled ‘auto-stab’ and the MCAS would have been disconnected and the aircraft flown normally. But not only were these switches not documented, they were also tucked away at the back of the center console and so not readily visible. This was stated nowhere in the cockpit checklists. In the USA the information as to the use and location of these switches had passed by word of mouth between crews, and was likely seen as a teething problem with auto-stabilization in a new aircraft type that would soon be sorted out, with the check-lists being amended accordingly at the next update and as such, no big deal. Crews further afield overseas were less well advised. Actually, the pilot that few the Lion aircraft the day before the crash, also had the MCAS problem but, with friends in the US, he was in-the-loop and knew what to do, switched-off the Autostab. and conducted the rest of the 90 minute flight ‘manually’.  On arrival in Jakarta, it is understood that, as is normal, he entered the auto-stab. unserviceability in the Technical Logbook. The engineers no doubt ground tested the system but, with the aircraft being horizontal on the ground, it of course worked normally. That being the case, they would have entered “tested and assessed serviceable” in that aircraft’s Technical Logbook (also a normal, and frequently used, procedure).  So, the unfortunate Indian Captain assigned to the aircraft the next day, inevitably suffered the same problem again but, being out of the US Pilots’ gossip-loop, was not so lucky and nor were his 180-odd passengers and crew!  The recovered Cockpit Voice Recorders shows similar confusion and panic in the final moments Ethiopian Airlines Max some five months later.


In the 18 months enforced down time since these accidents, the B737-Max has been virtually completely recertified by the FAA and the MCAS issue in particular is now fully resolved and properly documented, with pilots being properly trained in its use. The pendulum AoA sensor, through additional software, has now effectively been made duplex. So one may be confident there will be no repeat in future global Max operations of this sorry tale. The same cannot be said for the Boeing company. Their quality management issues in manufacture are still on-going causing 10s of billions of lost revenue, fines, law suites and capital expenditure. In such circumstances, one cannot imagine where they will find funds to develop a new mid-range aircraft design (the NMA – New Mid-range Aircraft) which they so desperately need to compete with Airbus. Indeed the Boeing CEO, David Calhoun, has indicated in an October interview that, for him, NMA has come to mean ‘No More Aircraft’ – at least until there are new engines types capable of offering some 20% in fuel savings.

Such engines are likely be similar to the new open-fan types currently being tested by Airbus on an A380 (see photo.). As such, there is a logic to this decision in that its location on the aircraft may likely be other than under the wing. However, since such power plants will only be available towards the end of this decade, the delay will mean that Boeing will have come up with no fresh design for more than quarter of a century. For much of this century, Boeing and Airbus have split the market between them approximately 50:50. Since the Max-saga, it has dropped to less than 40:60 in Airbus’s favour. For Boeing to not produce a new aircraft type for a full human generation will increase the negative impact on this balance, which will be further exacerbated by the fact that a whole generation of Boeing engineers will have had no experience in the field of commercial new aircraft development. 

This is while Airbus are busily developing new generations of airliners with hybrid-electric or hydrogen power plants. So 10 years hence a 30:70 split is not unimaginable. The June announcement of the intention to move of the Boeing corporate HQ from Chicago to Washington DC, is indicative of a Boeing acceptance of this and a shift of company focus to government military/space projects.

But, notwithstanding one’s harsh review of this recent scandalous history, the author of this piece, where possible, will always choose to fly in a Boeing over an Airbus. Why? Because, as stated in a former flight control essay (PFT-2 in Sepetmber’22), with the exception of the B-787, Boeing aircraft are flown by Pilots, while the more advanced (Fly-by-Wire) Airbus types are flown by a computer. Before one is sued for the publication of such an opinion, let it be said this is a subjective choice is based on no (accepted) objective evidence and hence, is solely a function of this Author’s personal lack of digital empathy – a peccadillo for sure, but one that is shared by many other analogue folk!