Super Puma Down – II

CSI Metallurgy


So! There were chip detectors fitted and working on that day, 1st April 2009, in the gearboxes of the Super Puma G-REDL. How was it then that they had given virtually no warning that the main gearbox was a time bomb that was about to explode at any minute?

Mike M, in the business, told the Lad that a helicopter was mostly a flying collection of gearboxes. The passenger cabin is not much more than an appendage bolted to the engines and the mechanisms.

Gearbox and speeds
This shows the gears to the Main Rotor


For most engineering, structural failures, the earliest symptom is a crack. It, mostly, begins to open at the surface of a component. It extends, speedily or slowly, into the interior of the piece, some pieces [chips] breaking away as it does so. Final failure occurs when the crack makes the component unable to carry out its function. has not got enough sound material in its cross-section that is not cracked to cohere under tensile stresses. There is another type of failure that is particularly relevant to a helicopter. Underneath a rapidly rotating ball or roller in a bearing track [race], pieces of the track can begin to crumble away. This does not often proceed to fracture of a race as it is due to compressive stresses. These tend to keep the part pushed together rather than as tensile stresses tend to pull the component apart

The AAIB report tells us, in summary.

One chip had been found on one of the detectors some days before. The mechanics consulted the manual as to what should be done. They thought that it was just a piece of scale. They spoke to the manufacturer’s engineers by phone and email. At each end of this communication channel there misunderstandings as to what had been found, what had been done, had not been done and what should be done. The upshot was, terribly, nothing further was done because no significance was attributed to the ‘piece of scale’ In fact it was bearing steel – of dreadful import. 

In the middle of the last flight, one of the eight planet gears abruptly shattered into massive fragments.

One fragment was over-run by the next planet gear. If it had been the size of a matchstick, a piece of metal would, at the speed of this gearbox, have been crushed, passed through and flung out. There would have been some damage to the gear teeth but no more. This fragment however was of an awful, irresistible size. In the subsequent examination of the wreckage it was never found but everything else was. The size of the gap of its absence tells us in itself a grim story. It would have been a hellish boulder the size of a man’s fist: quite uncrushable. It burst through the strong metal shell of the gearbox outer case, splitting it like an over-ripe tomato with a shattering explosion.

The crew saw the emergency, on-screen warning of the catastrophic fall in oil pressure to almost zero. Two seconds later the craft ceased to respond to any flight controls. The grip of the gearbox on the main rotor was broken. The helicopter rolled and yawed and pitched as though it were a paper windmill in the hand of a child. Twenty seconds later the rotor lifted – free – away from the fuselage; it tilted and then hacked and severed the helicopter tail and its control rotor. The rotor then spiralled away into the air; freed from the burden of the fuselage. What was now left, the cabin and engines together, streamlined like an egg: plunged uncontrollably towards the sea far below, carrying the desolate passengers and crew.

As there had been only one chip found in the oil system, how did the failure start and progress without many more? Call in the metallurgists.

The metallurgists are the brothers in arms of the engineers. Tony T told The Lad that he had the best job in the world, as a failure metallurgist in an engineering organisation with an international reach. He travelled widely to study forensically a variety of failures. Luckily, none of his problems involved loss of life but even if they had, perhaps he would have helped with an understanding as a kind of memorial. If the study of metals appeals to you, go for metallurgy.

Metals are complex structures when you look at them with a microscope. Most people imagine, if asked, that even at that level metal is smooth like a bar of chocolate is smooth. Far from it. Solid metals are crystalline. In a crystal, the overwhelming numbers of atoms are lined up neatly in rows, sheets or repeating patterns. Tiny examples of crystals of this sort are sugar and salt. However a piece of metal is not one single crystal. It is almost always made up of millions of tiny crystals jammed together and each adhering to its neighbours.

Why is this? When the metal is molten, every atom is rushing madly about in all directions. As it cools, pairs of atoms begin to adhere to each other in millions of places, called nuclei. Then other atoms arrive and stick to the first two but only in a neat, repeating array. Imagine 4 footballs: three touching each other to form a triangular pattern and the fourth sitting on top and in the middle of the triangle below.. Such an arrangement could extend as far as you like if you have enough footballs. As the atomic pattern grows, forming a crystal, it continues until it hits another nearby. This is happening in all the nuclei but in a direction depending on the orientation of the first pair of atoms. Each crystal array is at a different angle to that of its neighbour. Thus as the metal cools, each of the millions of atoms in a single crystal is rushing to slip into its place in the pattern. Until, thud, – thud, – thud – and every crystal is jammed up against its neighbours and the whole mass jerks into a solid, rigid mass of thousands and millions of crystals.

In recent, two or three decades some special components such as aero-engine gas turbine blades have each been made of a single crystal. But this can be done only with enormous difficulty, technical cleverness and great expense that are not justified for any other components.

In addition to the conventional processes that are equivalent to standard police work or ‘boots on the ground’ Lots of cutting, polishing and etching with acid to show the structure under the microscope.

Then they zoomed in on the critical areas. The materials engineer has an army or techniques and instruments to study his materials??? Because of the critical importance of the investigation of this accident, she brought to bear some of the Special Forces of the army. There was conventional optical microscopy but also 3D surface optical mapping, 3D X-ray tomography, high resolution Field Emission Scanning Electron Microscopy, and (FESEM) Transmission Electron Microscopy, TEM.

The pictures below show the view, like a geologist overflying a mountain range, of the fracture surface that they had to study to tease out answers.


Raw fracture
This is the metallurgist's first sight through a microscope at low magnification
Fracture with areas defined
After a lot of close examination, the metallurgist decides that these areas of the fracture had different causes


One of the significant, engineering features of the planet gears is that the bearing track or race and the gear teeth are all in one piece. As we have said before, most of the stresses caused by the bearing rollers are mainly compressive and tending to close any cracks; but here’s the rub, with the integral gear teeth much of the stress field produced is tensile and crack opening. The result with the two fields is that in this double function component, once a crack has crept beyond the race stresses, it enters the gear, tensile stress region opening and, perhaps accelerating. It can eventually pass through the whole gear pinion and break it into pieces.

The morphology [the shape] of the fatigue crack in the second stage planet gear, 13. suggested that it had initiated from a point at or close to the surface of a highly loaded section of the bearing outer race,

The following pictures show a 3D view of their conclusions.

3D image for crack origin
The metallurgist, after much work, was able to calculate the origin of the crack.


Ultimately, this suggests to The Lad that the failure and any chips began, if not entirely internally, then at least, within the compressed area of the gear pinion material body. The result? Nothing – no crack – broke the surface to provide chips until the fracture was almost complete and only minutes away from catastrophe.

What can we do about this problem, this type of behaviour? Let’s look at this in the next post.

Engineers’ responsibility

Engineering is one of the three drivers in the advancement of the human race. This blog aims to give to career seekers and also to the general public a taste of how this might be so. They are not well served by the current media. It is an engineer posting: not a ‘scientist’. It describes real professional engineering as it is in the real world usually in the present and occasionally as it was in the recent past.

Super Puma Down – I

Without Warning?

It was April 1st 2009 and the Eurocopter Super Puma L2 helicopter was expecting to land at Aberdeen at 1314 hrs. This was still 20 minutes away but, at the 2000 feet cruising altitude, the coast landfall 10 miles away was just in sight.

Super Puma
The crashed helicopter was one like this

It was about half way through its busy schedule to and from the rigs that day, flying at nearly full speed with a full complement of 2 pilots and 14 passengers. The co-pilot radioed base that all was normal. Only twelve seconds later came two MAYDAY calls

Below, was a modern, powerful, rig supply ship, the ‘Normand Aurora’, on a so-far uneventful trip. Someone on watch on the bridge changed all that. It was good visibility and there was a shocked shout of alarm. Two miles away, the helicopter was hurtling into the sea with separated rotor following it. Then came the bangs, the black smoke and the explosion. The ship swung towards the smoke.

Normand Aurora
Normand Aurora was the nearest ship to the crash site and rushed to the rescue.


Launching their fast,-rescue inflatable. It hit the water with a loud slap and accelerated away. Leaving the mother ship quickly far behind as its helmsman gripped the steering wheel with white knuckles and stiff-armed the throttle fully forward. He and his crew were desperate with hope that there would be something that they would be able to do: that there would be someone that they could help among the unfortunates in the helicopter cabin that had plummeted into the sea at high speed. But fearful at the same time. After the headlong two miles, its crew found a large circle of churning water. Within there were life rafts and debris. They also saw eight people; none were alive.

Epicyclic Gears

Planet gears recovered
Recovered from the sea bottom. Note the missing pinion at four o'clock.


Above are planet gears from the downed helicopter showing corrosion from their immersion in the sea. They are without an outer casing destroyed in the accident. There should be eight gears but it can be seen that one is missing. The destruction of the one, missing planet gear was the cause of the tragedy. Above shows only a part of the gear boxes and trains in the Super Puma [and other similar helicopters].

Had there been no advance warning of the impending catastrophe at all?

The drive shaft from each of the two engines in the helicopter runs at 23 000rpm [that is, the internals of each engine is rotating 380 times in one second or around 5 times as fast as a family car engine!]. The main rotor blades rotate at 265rpm. This means that the helicopter design engineer had to design a gear box to give a reduction of nearly a factor of 100. It has to fit in as small space and have as low a weight as possible.

When the designer needs to slow down the rate of rotation of a shaft by a large amount like this, she usually goes for an epicyclic gear design. These are commonly known as a sun and planet gear sets. This is what is found in a Super Puma between the fast spinning engines the relatively slowly rotating main rotor.

This epicyclic design was shown in the textbooks of The Lad like this, and similar diagrams are still shown today.

Textbook diagram
The textbook version is rather lightweight compared to the real thing.


In real life where very large power has to be transmitted in as small a space as possible, there are more planet gears than in the textbook diagram. They fill the circumference and each is wide and massive. Such planets of half of the Super Puma epicyclic gear train are shown in the salvage photograph above.

To see how designers calculate the variables in a real design of epicyclic gears see –

Magnetic Chip Detectors

Even though the designers seek to make engines and gearboxes as reliable and free from the risk of components failing as possible there is still a need to keep a check on machinery health. For a Power Station generator or a car engine there is no great, inherent problem to be anticipated if it rapidly comes to a halt after 30 sec of noisy running. It is quite a different problem if the engine is powering an aircraft flying several miles high over the ocean. Here a significant risk of such a sudden stop is not acceptable. They must head off such failures before they happen. They must search for signs of any problems well in advance.

The magnetic chip detector is one of the neat ideas that help maintenance teams do this. It is a simple concept. Many of the most highly stressed components are made of steel which is magnetic. One of the commonest symptoms of failure, when such a component wears or suffers fatigue cracking, is that chips of metal are generated and released from the parent component. The oil, as it is circulated throughout the engine, washes such chips away and usually takes it to the lowest part of the engine. En route, if it washes over a single small magnet, it will be captured by the magnet. The maintenance team simply unscrew the magnets at regular intervals and an early alarm can be raised if any chips are found sticking to the magnet.

Such detectors are positioned at various places within the engine oil flow where any chips may be washed over them. An alternative design is to provide twin magnets close together. Coupled to this type of device is a power supply and electronic detector to signal to the helicopter pilots, even in flight, when a chip bridges the two magnets. Such a design is shown below.

Chip detector
This is the operating principle of the more capable design that can provide a signal in flight


There are many such detectors designed into the Super Puma. Several are in the vicinity of the main gear box. The design of such detectors is another one of the many examples of the nexus where the design principle of “simple and reliable” approaches close to the principle of “too crude for the risk burden”. The designer has to consider which is the truth in every such case. Did the detectors work this time or not? If not, why not? See the next post.

Memento Mori

Engineering turns the forces to the benefit of mankind and the results have immense consequences. These consequences are, on the whole, beneficial but sadly, as with any efforts of the human race, for some individuals can be malign.

Bloody skirmishes to understand each way that a structure can fail and to avoid them all are a repetitive feature in engineering history. For ordinary structures most of the skirmishes have been avoided and, nowadays, fewer new ones appear. But fresh demons occasionally burst forth to confound us in new campaigns to complete new tasks or use new materials. When they do, they extract their price in blood or treasure.

Professional engineers have to be continually alert. The engineer knows that the nature of her or his work usually brings great benefit. But it can, also on occasion, bring tragedy.

So it was with G-REDL on 1st April 2009.

RIP deceased

Engineers’ responsibility

Engineering is one of the three drivers in the advancement of the human race. This blog aims to give to career seekers and also to the general public a taste of how this might be so. They are not well served by the current media. It is an engineer posting: not a ‘scientist’. It describes real professional engineering as it is in the real world usually in the present and occasionally as it was in the recent past.

Madeleine trumped by Ruby Loftus

Trefolex and Tufnol ride again in Mechanical Engineering 101.

Famously, the hero of Marcel Proust’s multi-volume novel, “A la Recherche du Temps Perdu”, found that memories of a period many years before were triggered by a smell and taste of tea and a dipped madeleine.

Immediately the old gray house on the street ….. rose up … and the entire town, with its people and houses, gardens, church, and surroundings, taking shape and solidity, sprang into being”

Risking the bathetic after such a graceful idea and prose, The Lad found the opposite the other day: smells from his youth were triggered by this striking picture. It had been featured in a recent exhibition, Women War Artists (now closed), at the Imperial War Museum, London – website .

Reduced Ruby
IWM2850 Dame Laura Knight - 'Ruby Loftus screwing a Breech-ring'. 1943, Oil on canvas


Instantly, the workshop with its high roof appeared; it’s the Fifties. Machine tools are ranked in bays each controlled now by an apprentice in a white boiler suit. Each bay patrolled by its white coated Instructor. There was the low rumbling of the milling machines, the hum of the lathes just like the one in the picture, the hiss of the grinding machines. Equally pervasive was the smell of cutting oil and often the raw, burning smell of machined Tufnol – a composite material of linen and resin – still going It seems, [ ].

But if it is a really vile smell you are after then it is in the fitting bay in the corner of the machine shop. Here are the benches and vices where there was hammering and a continuous swish of filing. There, on the bench were the pots of Trefolex, a thread-tapping paste, green coloured and with a vile stench. You can still get it today [ ] though they may have got rid of the smell by now.

The Training School entertained both Trade Apprentices and Technical Apprentices. The Trade Apprentices were being aimed at careers as skilled machinists; whereas the Technical Apprentices were intended for the draughtsman’s career. Notice the suffix ‘man’. No women or girls then in the Fifties: they were all long gone after the Second World War. Not even an office girl. “Disturb the youths, you know”.

But, contrary to the popular vision, the Training School does not represent the milieu of the professional engineer. It is Mechanical Engineering 101 where, then, he or nowadays often she discovers the basics before moving on. The mechanicals move on to design or work on new products for the machines to make, the production guys to introduce better machine tools or ways of dealing with difficult materials.

It was here, in the Training School, that The Lad first tried cutting an external screw thread on a lathe with a single point tool. He found it difficult while the Trade Apprentices seemed always only to thrive on the challenge. Then they moved on to using the same technique to cut an internal thread. This is what Ruby Loftus in the picture is doing: under intense pressure in War time using the high skill of cutting what would be a buttress thread for a breech block of an artillery piece.

This magnificent picture though is much more interesting than just for the memories of The Lad. The picture is, most importantly, but also so powerful, painted in 1943 the middle of the War, shows only a one male, a single small figure in the distant background. The thunder on the Home Front had changed everything. The painting of this picture shows that the changes were so radical that they had to be recorded. It was a peak in women’s employment never reached again even today. However, almost 70 years later, girls and women do take their proper place as apprentices and professional engineers.

The dignity of Ruby and her concentration on the complex machine and work piece stands four-square with the haughty gaze of Henry VIII in Holbein’s painting.  The painter was Dame Laura Knight who had, pre-war, specialised in painting dancers and circus performers. . Though less important, The Lad believes this powerful painting is also the most accurate, realistic canvas of a rare subject – a snippet of Production Engineering. Unless, that is, someone else knows better.

There is the contained poise and tension of the lean of Ruby. It is that of a dancer yet with stillness. Countering the figure of Ruby and closely observed, are the dark, gleaming masses of the lathe: the tool post, the carriage and the tail stock. The tools are there too: a scraper to remove burrs, an internal calliper for measurement, parting–off tools and tool holders and a ring spanner for the bolts on the carriage.

Ruby is gazing intently at the spot lit tool. It is cutting the thread inside the breech ring during the very brief period as the tool passes from the side of the work piece nearest her out of the side within the rotating chuck. Her hands are not just supporting her but a part of her vital control of the machine. She rests the fingers of her left hand on the tool post to check and confirm the faint, continuous, humming vibration showing that all is well with the single point cutting tool. Her right hand performs the same check on the gearbox driving the feed screw and confirms that the carriage is moving. That same right hand was also well placed to switch off the drive to carriage and work piece in an instant when it left the inside surface of the work piece before reversing it back out in the same helical groove of the buttress thread but with a slightly deeper cut.

Now, in the Twenty First Century, a CNC Turning centre does it all more quickly, just as accurately but with less involvement of a human operator – male or female.


Engineering is one of the three drivers in the advancement of the human race. This blog aims to give to career seekers and also to the general public a taste of how this might be so. They are not well served by the current media. It is an engineer posting: not a ‘scientist’. It describes real professional engineering as it is in the real world usually in the present and occasionally as it was in the recent past.

Some machines swim

One, unseen, already-submerged diver was filming near to a hole in the thick ice sheet above: as the elegant cylinder dropped vertically at high speed through the still, -1°C, water below. Immediately, as though alive, the vehicle swung gracefully into level flight towing a tail of yellow cable behind it. Ministering to and checking on the machine on this, one of its early test swims, was a black-clad, scuba diver.

The Lad was transfixed by the magic sight in the vast under seascape of a thousand shades of blue and green. The voyager looked as though it had been born there instead of being designed by human beings. Tell-tale features, though, were the lights: a white searchlight beam for a camera and a pair of scarlet, laser beams lancing through the gin-clear water from each side of the nose of the vehicle. Another was the complex internal structure clearly visible with, not the fluent curves of a living body, but the lineaments of straight lines and exact circles of a densely packed machine. It was about 2m long and 20 cm in diameter.

It was the 30 November 2011 and “The Frozen Planet” Part 6, ‘The Last Frontier’ on BBC Television that was the unexpected carrier of the strikingly beautiful images of this example of the art of the engineer.

Then the vehicle darted straight ahead at least twice its previous speed into a corridor among the irregular blocks of the ice pack above. It gave an impression of a shark but without any sweep of a muscular tail but with a rapidly accelerated spin of a propeller.

The Lad was captivated and vowed to find out more of this masterpiece. A search only just begun and the results will be reported here. This machine seemed to The Lad to encapsulate what engineers do.

Engineering is one of the three drivers in the advancement of the human race. This blog aims to give to career seekers and also to the general public a taste of how this might be so. They are not well served by the current media. It is an engineer posting: not a ‘scientist’. It describes real professional engineering as it is in the real world usually in the present and occasionally as it was in the recent past.

UK enters Swedish Turf

The Queen Elizabeth Prize for Engineering” certainly has a ring to it.

The Lad is glad to see the announcement of a big new prize devoted to Engineering excellence. Its aspiration to be equivalent to a Nobel Prize by being open to engineers across the globe shows admirable boldness and determination.

Was it a problem The Lad wonders, that this global reach made it more or less difficult to raise the money from the financial backers in the engineering industry . Depends if they have a global presence themselves, he supposes. The website says they are BAE Systems, BG Group, BP, GlaxoSmithKline, Jaguar Land Rover, National Grid, Shell, Siemens, Sony, Tata Consultancy Services and Tata Steel Europe. That’s seven UK or UK based companies and four non-UK based companies.

A group of the great and the good have so far have been appointed to be Trustees to manage the endowment fund and thus deliver the Prize. The Lad is reluctant to venture into the political [with a small ‘p’] snake pit but he thought it worth having a quick look from an idiosyncratic standpoint at their engineering antecedents.  They are

Lord Browne of Madingley [Chairman of the Trustees] who seems to have started as a Physics graduate and a BP apprentice forty-four years ago. The plan seems to be that he is there to provide serious gravitas via the enormous chemical and petroleum engineering clout of his BP past.

His fellow trustees are

Sir John Parker, who studied Naval Architecture and Mechanical Engineering at the College of Technology and Queen’s University, Belfast and began as a member of a shipbuilding design team forty-seven years ago. He is chosen as, presumably, the nearest they knew in the London network to an engineering creative;

Sir Paul Nurse is a geneticist [geneticist!?] and cell biologist and won a Nobel Prize in Physiology or Medicine in 2004 and can only have been chosen to offer, one imagines, judgement on the benchmark to the Nobel standard, and

Mala Gaonkar is a Harvard economics graduate and 1996 MBA presumably will monitor the care of the endowment funds in the maw of the City.

The Government Chief Scientist, Professor Sir John Beddington is a biologist and has accepted an invitation to be an adviser. His is the task of advising the Trustees on how, when required, to screw a response out of the government departments. Sorry! Guess it would be better to say ‘how to press the hot buttons‘.

Anji Hunter, who was an history graduate 23 years ago and sometime advisor and Director of Government Relations to Tony Blair, has been appointed Director of the Prize. Because ‘administrator’ is no sort of term for an engineering outfit, can The Lad suggest that she takes to herself the title of ‘Clerk of the Works’. Now this has a good engineering flavour and a long pedigree. Nay! An ancient pedigree it has; far older than that of ‘Prime Minister’ for example. As a job, it dates back to the reign of Edward the First when such a Clerk was the vital organiser of the building of those mammoth civil engineering feats: the Castles in North Wales around 1285.

A fine group. All the men have lately spent many more long years at the stellar managerial, coal face than at the engineering design scheme. They will appoint a judging panel next year who will include additional members presumably. It will be interesting to see who they turn out to be.

He notes that all, or at least the head office, has not ventured to far from the warmth of Westminster. Carlton House Terrace,SW1, darling!

Well, even if the current staff, sorry – Trustees, do not clearly have ‘engineer‘ running right through them like seaside rock, The Lad wants to give them the benefit of any doubt and wishes them success in making the Prize a glittering success and all engineers proud of them. He will be watching them.

How will the MacRobert Award fare now?

Ignorance, quarrels and the feedback loop

Or people shouting at each other

Some commentators are a constant irritation. The grand panorama of modern media allows any ideology by any believer to be broadcast. This is a complex world and some have little underpinning of demonstrable truth and others have an unwavering fixation upon only one of several alternative world views.

There are those who advocate a particular belief system. Some such are militant proselytisers for religious beliefs. Others are those, finding the world behaving incorrectly, setting out to drive everyone down the ‘correct’, usually narrow, path

Then there are those who are driven less by unwavering urgency and more by a plan to make a comfortable living from the commentating process. They have a facility with words; access to the prints; and no restraint from knowledge of their ignorance. They do like the sound of their own voice and their words in print are, for them, like a nice, warm bath.

These latter, articulate writers are insidious in their effects when they comment on engineering topics. None are engineers and many are politicians. Too often it is here that the irritation develops due to a faulty premise.

Faulty premise.             If some project is not yet completed then it is obvious that it cannot be done or will be too difficult.

This premise is applied widely but has appeared in connection with safe burial of nuclear waste and, more recently, Carbon Capture and Sequestration.

Forsaking the phrase “Let us be clear that….” destroyed by politician when matters are obscure or untrue, let us go for a bald statement instead.

Correct premise.           Engineers create something when it is needed and has some apparent economic basis. If a project does not violate one of the laws of physics or thermodynamics, it can probably be done.

If you ask them in advance, engineers will take the line boldly, and not unreasonably in the evidence of the historical record, that if a project does not violate one of the laws of physics or thermodynamics, it can probably be done.

What is it that inflames this irritation by lathered ideologues or flushed commentators? There is heat when each holds forth in isolation. But it is the process of interaction with each other that increases the din greatly due to the engineering effects of positive feedback and synergy.

Feedback is a widespread and important operation in control engineering. Feedback is the process of measuring changes in a process as it proceeds. There is negative and positive feedback. Negative is changing a process to reduce the measured change. Positive feedback is changing the process to increase the size of the measured change. A problematic feature of positive feedback is that it is frequently unstable sending a process rocketing to some far off regime. Thus it is with the irritating commentators.

There is also synergy which is defined as increased effects produced by combined action. Working together, even if it is in opposition, means that both sides of an argument work each other up to a frenzy.

There is a interesting example roaring away in the field of climate change where all these features can be seen. There are a multitude of websites. Just visit one of each and you will be rapidly flung into many others There is Greenpeace of course at for those who discuss how worrying are the changes and what should be done to reduce them. Then there is another, The Global Warming Policy Foundation , that believes that climate change is not what it appears and that many plans to modify the changes are misbegotten.

Speaking above of Carbon Capture and Sequestration, this is a topic of the next post.

Engineering is one of the three drivers in the advancement of the human race. This blog aims to give to career seekers and also to the general public a taste of how this might be so. They are not well served by the current media. It is an engineer posting: not a ‘scientist’. It describes real professional engineering as it is in the real world usually in the present and occasionally as it was in the recent past.

A step in the long road.

Give thanks to the Sunday Times in the 23 October 2011 issue, or more especially Joe Watson of Swansea, for a letter that moves a little way down the road. That is the road to an understanding of engineering reality by the general public and those thinking about choosing a career.

Mr Watson rightly chides a previous writer for suggesting that engineering is a manual job. His own definition of the properties of an engineer is hard to better. The engineer is a ‘graduate who has competence in physics, mathematics, IT and design – to mention a few’. This is not true of the tradesmen or women who are the artisans. While this tells us what they are, and is fine as far as it goes, it does not tell us what the engineer actually does. But, fair do’s, it is progress.

Why, though, is such a simple definition still necessary in the modern world? Think about this. The distinctions between patients, doctors and nurses and even finer graduations such as Registrar or consultant seem to be quite clear to everyone. The Police uniformed branches and its sub-branches compared to the detectives are well-known. Is it because each of those professions is the subject of a vast number of programmes on television? Is that the reason: people learn through the TV stories?

The Lad will not support this as he does not want to encourage the already over-mighty, super-confident denizens of that medium. No, the ignorance is more likely to be because the general public does not normally come into any contact with engineers in person or read about them. Yet, for goodness’ sake, they come into contact with their products every hour of every day. Perhaps this blog will add a few bricks so that the profession rises into view a little more.

Engineering is one of the three drivers in the advancement of the human race. This blog aims to give to career seekers and also to the general public a taste of how this might be so. They are not well served by the current media. It is an engineer posting: not a ‘scientist’. It describes real professional engineering as it is in the real world usually in the present and occasionally as it was in the recent past.

An Engineer’s must-have

It was years ago when The Lad first reached for the spanner for the usual 3/8 UN nut. It wasn’t there.

“What scruff  [actually, a less repeatable name] has nicked the spanner?”

One of his compatriots had either left it lying around near where he used it last or nicked it for his tool box. In a busy workshop, it cannot be surprising if any tool goes walkabout. It happens even in the best, practical, production engineering school. But then everybody needed to use them so it was worth putting one that you have used back where it came from and everybody else could find it when they needed it. At least that’s what the instructors said – piously.

It was round about that time that The Lad first saw an advert for  tool sets. The big ones with dozens of spanners within a steel tool box that attracted his covetous, young eye. The biggest and most complete ones even had castors as they were too heavy to carry. Have a look at one – product TKU 1014 at   ,
212 pieces and 67 kg! The Lad supposes that you could call it the secret of the engineer’s inner Nerd. But then who does not have such a secret?

Why so many pieces? Well, if the golden path and self-styled foundation of the modern world – Information Technology – can suffer from legacy systems even in its youth; then so can Engineering, that has been around many times longer. As well, the spanner has several forms for different jobs such as open jaw; socket; ring spanner etc.

The spanner is  important to a mechanic. The screw thread has an ancient lineage and so has the regular shape of a nut or bolt head, most often a hexagon, that is required to manipulate it. Both are still ubiquitous in all engineering structures. The ancient lineage means that in its early days many different standard sizes of nut, bolt or screw were used. A major  problem was that interchangeability of fasteners between manufacturers and machines was impossible.The thing about screw threads is that they are likely to be in use in some machines for decades or even longer. If you want to maintain one of those machines, you need a matching spanner.

It’s not just the diameter of the bolt that allows it to fit in a screw hole. Put simply it’s both the shape, usually a triangle, and also the depth of the spiral groove. The screw or bolt will not even begin to do its job if the bolt diameters match but both these features do not.

After an initial push in the early 19th Century when an accepted range screw thread designs that pairing a nominal screw or bolt diameter with a standard angle and depth of grooves was early seen to be useful subject for agreement between even competitive entrepreneurial engineering firms.   A series developed by the great pioneer, Whitworth, and named after him became widely accepted. Around the same time also very widely used was the BA [British Association] series. This latter series had the advantage that the series went to much smaller diameters of screw which made it suitable for small instrument applications. The United States had its own, non-interchangeable series’s known as the US Standard developed by the engineer, Sellars. For pictures of any of these threads without The Lad infringing any copyright consult any engineering handbook.

It was only after the Second World War in the early 1940’s that further significant strides were made to reduce the still remaining variety of ‘standard’ designs. It was the unprecedented explosion of engineering production during  and supporting the recovery after the war that led to the realisation of the  serious inefficiencies and wasted costs were caused by the lack of an even more widely standardised, and interchangeable system of threads. At this the national engineering bodies of the USA and Canada and the UK  came together to design a more rational series which they called the Unified series. Even this series was still restricted to the Imperial units of measurement. The final stage, to date, was to derive the ISO Metric series based upon the metric unit of length; that is the millimetre in the case of the thread. The Lad says the final stage but that will  be completed only when everyone across the world uses the metric screw series. That’s certainly not easy and indeed he can’t say that it has yet happened. The USA still uses its standard AF [Across Flats] series widely.

The Lad has described a simple outline of the field. There’s a lot more to it of course: many professional engineering designers have to move, for good reasons, into much more detail such as fine and coarse thread series and limits and fits and indeed other more specialised thread forms such as ‘buttress’ and ‘knuckle’. Then of course there are the very different components called power screws……

As engineering is the most powerful and essential tool in the advance of human civilisation across the globe and the management of force is at its core; so the screw thread in its principal task of storing force grew to be and remains vital to most engineering structures and power plants. It is a most subtle adaptation of the wedge whose unknown inventor must be saluted as a genius on a par with Isaac Newton and above Leonardo da Vinci.


Can You Stand the Engineering Heat?

Large scale engineering projects often have to be designed to withstand thunderous events: sometimes in reality and sometimed figuratively. The engineers of such projects need the technical knowledge, the professionalism and, yes, the courage to master the challenges. The Lad is talking here to those who may be thinking about an engineering career. For some of those it is just these challenging aspects that will appeal to them and perhaps give meaning to their careers. Do you look to having the opportunity to address and master major challenges? Do you?

More details are slowly emerging of a tragedy that is an example of a, thankfully rare, concomitant of such challenges: a real thunderous event. It is that of the Airbus A330-203 flight AF 447 which, on 1st June 2009 in the dead of night during storms over the Atlantic Ocean, vanished with every one of the 228 souls aboard. The aircraft was an example of the most modern and enormously powerful technology in flight.

There is still much to discover about, and to learn from, the cause of the accident. here we can only allude to a small aspect. There have been some suspicions voiced that the cause of the destruction was an operating failure of a small device for measuring the aircraft speed. This device is called a pitot tube.

This is a device that could hardly be simpler. The idea that its malfunction could be such a catastrophe requires a particularly wide-ranging imagination. Either that or an innate engineering wariness; a wariness founded on the possibility that ANYTHING could lead to problems. The operating principles of the pitot tube can be shown by the simple diagram below.

Pitot Tube Operating Principle

” Pitot Tube Operating Principle [Apologies for the very bad image quality. I must get a decent CAD application.].

This simple device is vital to the control of the even the modern aircraft. Indeed it has been so since the days of the earliest airliners. It and the details of its detailed design are part of the hundred thousand design decisions that are made as every large scale project, in this case the airliner, takes shape.

The pitot really is so simple. How does it work? There are two tubes that face forward into the air flow and are supported by part of the aircraft structure, probably the fuselage or the wing. One of them, called B in the diagram has an opening facing directly into the airflow. The air in that tube is driven in by the impact of the plane’s forward speed. Thus the pressure in the  tube is raised and measured by the pressure gauge at its inner end. This you might think is a good measure of the total speed but it is not. Part of that pressure is that of the static atmospheric pressure. This is the pressure which at sea level is measured by a barometer. The static atmospheric pressure varies greatly for an aircraft as it climbs and descends in its flight. This is part of that pressure which is measured by tube B but which is nothing to do with the plane’s speed. So Tube A is tasked with measurement of the static air pressure throughout the flight and whatever the air speed. This it does because it has no opening pointing forward but only one at the side of the tube. The side opening does not see the impact pressure due to the speed but only the static air pressure that acts in all directions. This pressure is measured in Tube A by its own separate gauge and is subtracted form the pressure measured by Tube B. So there we have it: the resultant modified pressure is due solely to the speed. Simples.

But watch that neither tube or opening is affected by storms or icing during the flight. Closure or even change in area of any of the openings by ice build up will entirely destroy the accuracy of the airspeed measurement. This, in turn can then baffle the computer controls of the aircraft. The design engineers would not have wanted this to happen but, nonetheless, this is what is suspected to have happened.

The engineers, metallurgists, chemists, physicists and all the other professions do not work as lonely individuals in the bringing of such a project to fruition. They all work together, struggle and debate on solving known and predicted problems as men and women in teams from one company and with others from other companies over periods of months and sometimes years. Despite this each one person is a professional, responsible for the accuracy of her or his own work. It is here that any decision may prove to be pivotal in subsequent events. The decision may be small,: indeed so small as to go unremarked and not reviewed by the others in the team or by its leaders. It can be successful or it can be fatal. Each engineer must consider frequently as he or she works, if he or she can stand up in a court and answer for this decision as being a reasonable and proper thing to do.

This is where the heat is in the kitchen. Can you stand it?

The end of this flight came when all forward speed had drained away and so, inescapably, the sealed, metal vessel weighing around one hundred and fifty tons and full of over two hundred sentient human beings careened vertically downwards at about ninety miles per hour. After three and a half minutes, its whole structure and its entombed passengers were destroyed as it hit the sea, belly first. Poignantly, the stalled plane had slowly rotated at intervals as it fell till, at the end, it was facing almost back the way it had come.

The French Aviation Regulatory Authority is Bureau d’Enquetes et dAnalyses pour la securite de l’aviation civile, known more simply as BEA. Its latest technical report can be found in English at

The numbing details above of the horrifying plunge from the stratosphere to the chill depths of the Atlantic Ocean come from that report.

See my posting of “The eternal question: can you answer for it?” on December 9 2010.

What intrigues us?

This week in a motoring supplement to the Sunday Paper, someone was describing a new car coming soon onto the market. It was to be a new higher powered version of an existing sports car. The is was one of the things said in the piece.

“Behind the scenes, the engineers of the AMG division of Mercedes are putting the finishing touches to a test and development programme  ….. But as they worry about such things as noise, vibration, harshness and torsional rigidity, prospective owners  may be more concerned  which colour to order roof in and whether to choose the optional Bang and Olufsen sound system for added serenity.

For those who are concerned with future career paths yet to be chosen either for themselves or others that they may be mentoring, this is a useful snippet to consider, debate or discuss.

What topic catches the fancy?

 What is the correct approach or is there one?

What do the engineering topics mean?

What is the difference between ‘design’ and ‘development’?

[From the Sunday Times, 15 May 2011, ‘ingear’ supplement, page 2, ‘Car of the Week’]