Tag Archives: Langewiesche

Ignorance, Incompetence, and Arrogance

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document.write(" serif;">Three Good Men

Two good men died last month. From opposite sides of the office, they left us with the same message: it is important to actually know what you are doing. There is another good man who died in 1988.

Robert Ebeling was an engineer at Morton Thiokol, the company that made the solid rocket boosters for the space shuttle. On his way to watch the shuttle launch, he told his daughter, “The Challenger is going to blow up. Everyone's going to die.”

It was January 28, 1986. I was flying a B-767 (ship number 612, registration C-GAVF) between Toronto and Vancouver. The Captain was S.R. (Rod) MacDonald. I was the First Officer. It was my leg. We heard about the Challenger disaster when we were over Winnipeg, listening to the news on one of the ADF radios. I can still remember how stunned we felt, how sad for our fellow aviators.

Andy Grove was the tough and brilliant manager who founded Intel in 1968 with Gordon Moore and Robert Noyce. In a 2010 article he wrote for Bloomberg Businessweek, he said, “But what kind of a society are we going to have if it consists of highly paid people doing high-value-added work—and masses of unemployed?”

He wrote when we were still reeling from the Great Recession. Even now, six years later, the people in the trenches have not recovered. The “recovery” part of the economy has gone mostly to the top 1%.

But income distribution is only part of the story. In the same article, Andy Grove also said this about exporting jobs to fatten the bottom line: “Not only did we lose an untold number of jobs, we broke the chain of experience that is so important in technological evolution.”

Richard Feynman died at 69, in 1988. He was a Nobel physicist, but he was also one of the great teachers of the last century. A member of the Rogers Commission which investigated the Challenger disaster, he famously squeezed a rubber O-ring in a C-clamp and put it into a glass of ice water. When he removed it and undid the clamp, the O-ring did not spring back – it kept its distorted, squeezed shape.

The shuttle solid rocket boosters were built in sections. The joints were sealed with large O-rings. The shuttle had never been launched at such a low temperature. That's what Bob Ebeling was thinking about when he talked to his daughter that day. He had spent the previous (week) trying to convince managers at both Morton Thiokol and NASA to postpone the flight.

The other shuttle disaster was Columbia, on February 1, 2003. It disintegrated on re-entry because a few thermal tiles were missing. They had been knocked off during launch. Pilots do a walkaround before every flight. These pilots were not allowed to do a space-walk to inspect the vehicle before re-entry. From safe seats in Houston, managers took control. Seven astronauts paid with their lives. For the curious: William Langewiesche published his Columbia's Last Flight in the November, 2003 Atlantic Magazine. (William is the son of Wolfgang Langewiesche, who wrote the wonderful how-to-fly book Stick and Rudder in 1944). It is a good read and worth the time.

Andy Grove said, “we broke the chain of experience.” But it is worse than that. We are losing knowledge. In this day of the internet, where we can theoretically teach ourselves anything we want to learn, knowledge is actually disappearing.

As a pilot I study accidents, trying to learn and survive. Recently there has been another tragedy. The Board has not completed its study, but from what I (and many other pilots) know already, the cause(s) were well known to the trade. For me, that is the tragedy of the tragedy. It happened because trade knowledge was not being passed on.

It gets worse yet. In aviation, we are well into to age of robots. Fly-by-wire was introduced into commercial aviation in the Airbus A320 in 1988. Knowledge and skill have been coded with varying degrees of success. The hard-earned legacy of many crashes and many pilots' lives lies hidden on a chip. Today's pilots (still critical to survival) may or may not understand the code or (increasingly) their job.

Why?

Andy Grove, in the article mentioned above, put it succinctly and with more than his usual tact: Our fundamental economic beliefs, which we have elevated from a conviction based on observation to an unquestioned truism, is that the free market is the best of all economic systems—the freer the better. Our generation has seen the decisive victory of free-market principles over planned economies. So we stick with this belief, largely oblivious to emerging evidence that while free markets beat planned economies, there may be room for a modification that is even better.

Ideology blinds us, making learning – true learning – more vital than ever.

A very old friend – we have known each other since kindergarten – recently took up the subject of learning. He is retiring gradually from the practice of medicine, and he is re-examining the mathematics and science he learned forty-five years ago. Recently he showed me his derivation of the number e. It would be an exaggeration to say that I now understand e, but he has taken me parsecs closer. He himself, through his efforts, now owns the number e in his heart and soul.

This kind of learning is possible in our age, but even with the ubiquitous internet we have not yet figured out how (Although Sugata Mitra is getting warm).

So there is hope. But so far I see more loss than gain. Knowledge is leaking away.

The Cycle We Have to Break

There is a tragedy. We don't want to assign blame or upset the apple-cart, so we don't learn from our mistakes. Managers, once again, become arrogant and complacent. Engineers have to feed their families. They keep their mouths shut. When teachers are leaned on, they are already paid so little they are more likely to leave the profession entirely. But not all of them. Some stand up and say what needs to be said. Thank you, Andy Grove. Thank you, Bob Ebeling, And thank you, Richard Feynman.

AF 447: Let’s Talk About Why – 1

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Thanks to the work of David Learmount at Flight Global, and that of the Wood's Hole Oceanographic Institution and the Bureau d’Enquêtes et d’Analyses, enough is now known about this accident to start looking for useful lessons and to analyze the data along with the BEA. Flight safety and the future of the piloting profession depend on this becoming a wide and serious conversation.

Pilots obsess about accidents for good reason. There is always so much to learn. The AF447 tragedy is an epochal example.

There is a mind-boggling number of lessons to be learned here, in a host of areas and disciplines: Pilot Training, Standard Operating Procedures, Instrument Flight, and Aircraft Design are but a few of them.

I will commit today to joining the conversation. I begin with a consideration of Angle of Attack.

Angle of Attack

Wolfgang Langewiesche (father of William) emphasized Angle of Attack in his excellent Stick and Rudder, published in 1944. Advocacy of AoA was an uphill battle then and it still is today. Instead of talking about AoA, we prefer to use airspeed and explain why certain speeds we use change with aircraft weight and G loading. Many or even most aircraft flying today have no Angle of Attack indication. The accident aircraft had two AoA sensors. The flight recorders had access to the signals from these sensors but the pilots did not, at least not when they needed it most.

Lift is produced when the air flowing over the top of a wing has a longer distance to travel than the air flowing underneath. The air “stretching out” over the top produces a lower pressure, allowing the higher pressure underneath to push the wing up. There is a caveat, however. The airflow must remain attached to the upper surface of the wing.

Imagine a cross-section of wing, with a line drawn from the middle of the rounded leading edge to the pointed trailing edge. This is the chord line. Now imagine an arrow pointing at the leading edge. This is the airflow.

If the arrow meets a (symmetrical) wing head-on there will be no lift. But let the wing meet the air at a slight angle and the airflow around the wing will no longer be symmetrical: it will meet the rounded leading edge at an angle and it will divide lower on the curve of the leading edge. The air flowing over the wing will have a longer distance to travel. Lift will be produced.

The angle at which the airflow meets the chord line is called the Angle of Attack. Up to a point, increasing the Angle of Attack will increase lift. But beyond a certain point – usually about 16° – lift will instead decrease because the airflow is beginning to separate from the upper surface of the wing. This is called the aerodynamic stall, and it always happens at the same Angle of Attack.

Angle of Attack is controlled by the elevators, the control surfaces on the trailing edge of the horizontal tail. When the pilot pulls back on the stick, the elevators lift, causing a down-force on the tail and forcing the wing to meet the air at a higher Angle of Attack. Trim tabs (small surfaces at the trailing edge of the elevators) can be moved to change the neutral position of the stick. (Another way to think of it is the trim tabs change the Angle of Attack at which there is zero stick force.)

In a modern jet transport the entire horizontal tail is usually moveable. This is because of the very wide speed range of the jet and because flaps and leading edge slats also change the “trim.” The other side of the coin is that this horizontal tail, or stabilizer, is very powerful in modern jet transports. A runaway stabilizer is a true emergency. Traditionally there has been a STAB IN MOTION aural warning, and an emergency cutout switch close to hand. Most cases where the stabilizer ran all the way up or down in flight have resulted in the loss of all on board.

In most aircraft the pilot is used to trimming as he flies. A change of speed or configuration, be it in a Beech Bonanza or a DC-9, will require a trim change. With some experience on type the pilot knows (for example on a DC-9) that extending the leading edge slats will require two beeps (of the STAB IN MOTION aural warning) of nose-up trim. He can use the thumb switches on the yoke to move the stabilizer as the slats are extending and thus remain stick-neutral during the configuration change. This is part of anticipation, or staying ahead of the aircraft.

Airbus aircraft, from the A320 onwards, are different. They are fly by wire, where computers are interposed between the pilots' sidestick inputs and the control surfaces. This arrangement allows some elegant additions to aircraft design, such as envelope protection (which among other things makes it impossible for the pilot to stall the aircraft) and, relevant to our discussion today, stick force per G and autotrim.

In Normal Law, which is where the Airbus is most (and the pilot hopes, all) of the time, configuration changes can be made hands off, even flying by hand. Of course the pilot has the tips of his fingers on the sidestick, but he can make a configuration change with no pitch input because the control system, in Normal Law, will maintain 1G flight. When he calls for FLAP 1 and the leading edge slats extend, the nose-down pitch is sensed and countered by the system, maintaining 1G flight. (1G is what you experience sitting in a chair at home or in an aircraft at cruise in smooth air). In effect, the airplane is doing the anticipation for the pilot.

Like the transition in the late 1950's from props to jets, fly-by-wire has been a major change for pilots. In general we welcome it for the many advantages it offers.

Experience has shown that to do his job, which is to ensure the safe arrival of his aircraft, the pilot must fully understand a much more complex airplane. Chesley Sullenberger reached up and started the APU (the Auxiliary Power Unit, a small turbine in the tail which can supply electrical and hydraulic power on the ground or in flight) as soon as his engines lost power. Why? Because he knew his airplane and he knew he wanted to keep it in Normal Law until touchdown.

The transition from props to jets was all about speed range, speed brakes and spoilers, high Mach number, coffin corner, Dutch Roll and super-stall, but in everyday life it was more about high drag on approach, no propwash, slow spool-up times, and operating on the back side of the power curve. This change took some adjustment on the part of pilots: the more experienced pilots had more adjustments to make. The same is true with the transition to fly-by-wire.

In a traditional airplane the pilot controls Angle of Attack with the elevator and the trim tabs or stabilizer. (More often he will be thinking of Airspeed, which is the constant-weight, 1G manifestation of AofA). He is used to feel, which is essentially the change in elevator neutral point with AofA. Should the aircraft slow on approach, the nose will get “heavy”, prompting him to pull back or trim nose-up.

That feel is totally absent in Airbus aircraft. (Boeing, in the B777, have added artificial feel to their fly-by-wire system). The Airbus pilot points and shoots, so to speak. Flying by hand he can take the bird, turning on a symbol (like a bird or an aircraft seen from behind) on his Primary Flight Display. The bird shows where his velocity vector is pointed; in other words, where is airplane will be so many seconds from now if he makes no further adjustments. On approach he can pin the bird on his flare point on the runway and either let the autothrust take care of the speed or adjust the thrust levers manually. If he does the latter, he must remember that there is no feel or feedback in the sidestick.

Obviously there are quite different assumptions operating during an approach in a Bonanza, one one hand, and an Airbus, on the other. This is not necessarily a bad thing. Take for example driving a car versus riding a motorcycle. In a car you steer with the steering wheel. In a motorcycle you counter-steer, putting pressure on the inside foot-peg and forward pressure on the inside bar, in effect trying to steer the front wheel the opposite way.

But you know you're on a motorcycle and not in a car. You have learned how to ride a motorcycle.

Consider, however, flying an Airbus if something goes wrong with a sensor or a computer and you wind up in Alternate Law or Direct Law. You are in the same vehicle but suddenly the rules have changed; the assumptions have changed. It is, in effect, no longer the same machine. This is a recipe which messes with a pilot's head.

Unfortunately, experience has shown that Direct Law, where control displacement is proportional to stick force and the airplane handles like a wet fish, is actually the more benign of the two degraded modes. There is a big message in red on the ECAM saying USE MAN PITCH TRIM. The pilot moves the THS (Trimmable Horizontal Stabilizer) by moving a wheel almost a foot in diameter. This is old-style, normal airplane flying, commanding AofA with stick force and trim. There is still no feel in the sidestick, but the procedure is familiar.

Alas, in Alternate Law there is no such familiarity. It is still point-and-shoot, sort of, but autotrim is still working. As long as there is back pressure on the stick the THS trims nose-up, and vice-versa. There is NO Stabilizer in Motion warning except the movement of the trim wheels. That would seem to be an easy thing to detect, but I can testify from personal experience that it is not. On every landing (in Normal Law) the flight control computers memorize the attitude at 50 feet Radio Altitude and at 30 feet start rolling in nose-down trim, in effect trying to mimic the feel of a normal aircraft slowing in the flare. In almost a decade of flying as Captain and Training Captain, whether as Pilot Flying or Pilot Not Flying, I cannot remember ever seeing the trim wheels move.

In two recent accidents an Airbus has hit the ocean with the THS wound to full nose up. In both cases the aircraft was in Alternate Law.

I am not an engineer. There are likely many ramifications that have not crossed my mind. But sitting here this afternoon my personal recommendation would be as follows:

Disable Autotrim in Alternate Law

AF 447: Let's Talk About Why – 1

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Thanks to the work of David Learmount at Flight Global, and that of the Wood's Hole Oceanographic Institution and the Bureau d’Enquêtes et d’Analyses, enough is now known about this accident to start looking for useful lessons and to analyze the data along with the BEA. Flight safety and the future of the piloting profession depend on this becoming a wide and serious conversation.

Pilots obsess about accidents for good reason. There is always so much to learn. The AF447 tragedy is an epochal example.

There is a mind-boggling number of lessons to be learned here, in a host of areas and disciplines: Pilot Training, Standard Operating Procedures, Instrument Flight, and Aircraft Design are but a few of them.

I will commit today to joining the conversation. I begin with a consideration of Angle of Attack.

Angle of Attack

Wolfgang Langewiesche (father of William) emphasized Angle of Attack in his excellent Stick and Rudder, published in 1944. Advocacy of AoA was an uphill battle then and it still is today. Instead of talking about AoA, we prefer to use airspeed and explain why certain speeds we use change with aircraft weight and G loading. Many or even most aircraft flying today have no Angle of Attack indication. The accident aircraft had two AoA sensors. The flight recorders had access to the signals from these sensors but the pilots did not, at least not when they needed it most.

Lift is produced when the air flowing over the top of a wing has a longer distance to travel than the air flowing underneath. The air “stretching out” over the top produces a lower pressure, allowing the higher pressure underneath to push the wing up. There is a caveat, however. The airflow must remain attached to the upper surface of the wing.

Imagine a cross-section of wing, with a line drawn from the middle of the rounded leading edge to the pointed trailing edge. This is the chord line. Now imagine an arrow pointing at the leading edge. This is the airflow.

If the arrow meets a (symmetrical) wing head-on there will be no lift. But let the wing meet the air at a slight angle and the airflow around the wing will no longer be symmetrical: it will meet the rounded leading edge at an angle and it will divide lower on the curve of the leading edge. The air flowing over the wing will have a longer distance to travel. Lift will be produced.

The angle at which the airflow meets the chord line is called the Angle of Attack. Up to a point, increasing the Angle of Attack will increase lift. But beyond a certain point – usually about 16° – lift will instead decrease because the airflow is beginning to separate from the upper surface of the wing. This is called the aerodynamic stall, and it always happens at the same Angle of Attack.

Angle of Attack is controlled by the elevators, the control surfaces on the trailing edge of the horizontal tail. When the pilot pulls back on the stick, the elevators lift, causing a down-force on the tail and forcing the wing to meet the air at a higher Angle of Attack. Trim tabs (small surfaces at the trailing edge of the elevators) can be moved to change the neutral position of the stick. (Another way to think of it is the trim tabs change the Angle of Attack at which there is zero stick force.)

In a modern jet transport the entire horizontal tail is usually moveable. This is because of the very wide speed range of the jet and because flaps and leading edge slats also change the “trim.” The other side of the coin is that this horizontal tail, or stabilizer, is very powerful in modern jet transports. A runaway stabilizer is a true emergency. Traditionally there has been a STAB IN MOTION aural warning, and an emergency cutout switch close to hand. Most cases where the stabilizer ran all the way up or down in flight have resulted in the loss of all on board.

In most aircraft the pilot is used to trimming as he flies. A change of speed or configuration, be it in a Beech Bonanza or a DC-9, will require a trim change. With some experience on type the pilot knows (for example on a DC-9) that extending the leading edge slats will require two beeps (of the STAB IN MOTION aural warning) of nose-up trim. He can use the thumb switches on the yoke to move the stabilizer as the slats are extending and thus remain stick-neutral during the configuration change. This is part of anticipation, or staying ahead of the aircraft.

Airbus aircraft, from the A320 onwards, are different. They are fly by wire, where computers are interposed between the pilots' sidestick inputs and the control surfaces. This arrangement allows some elegant additions to aircraft design, such as envelope protection (which among other things makes it impossible for the pilot to stall the aircraft) and, relevant to our discussion today, stick force per G and autotrim.

In Normal Law, which is where the Airbus is most (and the pilot hopes, all) of the time, configuration changes can be made hands off, even flying by hand. Of course the pilot has the tips of his fingers on the sidestick, but he can make a configuration change with no pitch input because the control system, in Normal Law, will maintain 1G flight. When he calls for FLAP 1 and the leading edge slats extend, the nose-down pitch is sensed and countered by the system, maintaining 1G flight. (1G is what you experience sitting in a chair at home or in an aircraft at cruise in smooth air). In effect, the airplane is doing the anticipation for the pilot.

Like the transition in the late 1950's from props to jets, fly-by-wire has been a major change for pilots. In general we welcome it for the many advantages it offers.

Experience has shown that to do his job, which is to ensure the safe arrival of his aircraft, the pilot must fully understand a much more complex airplane. Chesley Sullenberger reached up and started the APU (the Auxiliary Power Unit, a small turbine in the tail which can supply electrical and hydraulic power on the ground or in flight) as soon as his engines lost power. Why? Because he knew his airplane and he knew he wanted to keep it in Normal Law until touchdown.

The transition from props to jets was all about speed range, speed brakes and spoilers, high Mach number, coffin corner, Dutch Roll and super-stall, but in everyday life it was more about high drag on approach, no propwash, slow spool-up times, and operating on the back side of the power curve. This change took some adjustment on the part of pilots: the more experienced pilots had more adjustments to make. The same is true with the transition to fly-by-wire.

In a traditional airplane the pilot controls Angle of Attack with the elevator and the trim tabs or stabilizer. (More often he will be thinking of Airspeed, which is the constant-weight, 1G manifestation of AofA). He is used to feel, which is essentially the change in elevator neutral point with AofA. Should the aircraft slow on approach, the nose will get “heavy”, prompting him to pull back or trim nose-up.

That feel is totally absent in Airbus aircraft. (Boeing, in the B777, have added artificial feel to their fly-by-wire system). The Airbus pilot points and shoots, so to speak. Flying by hand he can take the bird, turning on a symbol (like a bird or an aircraft seen from behind) on his Primary Flight Display. The bird shows where his velocity vector is pointed; in other words, where is airplane will be so many seconds from now if he makes no further adjustments. On approach he can pin the bird on his flare point on the runway and either let the autothrust take care of the speed or adjust the thrust levers manually. If he does the latter, he must remember that there is no feel or feedback in the sidestick.

Obviously there are quite different assumptions operating during an approach in a Bonanza, one one hand, and an Airbus, on the other. This is not necessarily a bad thing. Take for example driving a car versus riding a motorcycle. In a car you steer with the steering wheel. In a motorcycle you counter-steer, putting pressure on the inside foot-peg and forward pressure on the inside bar, in effect trying to steer the front wheel the opposite way.

But you know you're on a motorcycle and not in a car. You have learned how to ride a motorcycle.

Consider, however, flying an Airbus if something goes wrong with a sensor or a computer and you wind up in Alternate Law or Direct Law. You are in the same vehicle but suddenly the rules have changed; the assumptions have changed. It is, in effect, no longer the same machine. This is a recipe which messes with a pilot's head.

Unfortunately, experience has shown that Direct Law, where control displacement is proportional to stick force and the airplane handles like a wet fish, is actually the more benign of the two degraded modes. There is a big message in red on the ECAM saying USE MAN PITCH TRIM. The pilot moves the THS (Trimmable Horizontal Stabilizer) by moving a wheel almost a foot in diameter. This is old-style, normal airplane flying, commanding AofA with stick force and trim. There is still no feel in the sidestick, but the procedure is familiar.

Alas, in Alternate Law there is no such familiarity. It is still point-and-shoot, sort of, but autotrim is still working. As long as there is back pressure on the stick the THS trims nose-up, and vice-versa. There is NO Stabilizer in Motion warning except the movement of the trim wheels. That would seem to be an easy thing to detect, but I can testify from personal experience that it is not. On every landing (in Normal Law) the flight control computers memorize the attitude at 50 feet Radio Altitude and at 30 feet start rolling in nose-down trim, in effect trying to mimic the feel of a normal aircraft slowing in the flare. In almost a decade of flying as Captain and Training Captain, whether as Pilot Flying or Pilot Not Flying, I cannot remember ever seeing the trim wheels move.

In two recent accidents an Airbus has hit the ocean with the THS wound to full nose up. In both cases the aircraft was in Alternate Law.

I am not an engineer. There are likely many ramifications that have not crossed my mind. But sitting here this afternoon my personal recommendation would be as follows:

Disable Autotrim in Alternate Law

Your Roof is Gonna Leak . . .

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Tradespeople

I am a pilot. I am lucky to have retired without incident from a career at an airline. Flying is still in my bones.

Mine is an apprenticeship trade. You can’t learn it in a classroom or by reading a book, although both help. You have to get your hands on an airplane.

Most trades are like mine. It takes constant study to stay current in the field. The reference books, software, and reams of data relevant to the job are huge and growing. But the essential learning, the learning that serves as backbone and basis for all the stuff in the reference books, is hands-on experience taught by a mentor and teacher. In turn you should pass this knowledge on to the next generation.

Tradespeople are no better and no worse than others. The majority of them like going to work and doing the the best job they can. There is satisfaction in building something or in accomplishing a mission. You can look back and say, I built that, or I did that.

But like rule of law or paying taxes, plying a trade with skill and devotion is a social contract. Protect me from lawbreakers, ensure others pay their fair share. Give me a living wage so I can support a family, and respect my work for what it is.

Nor are we tradespeople to be divided from business people, put in a separate category. On the contrary most small businesses are founded and powered by tradespeople, be they plumbers, machinists or software engineers with ideas. Entrepreneurship and the trades are interdependent and have been since the days of the guilds. Perhaps what we are less compatible with is management.

Hubris

I was lucky also to have spent most of a decade flying and teaching on Airbus aircraft. The design of the A320 is revolutionary, extraordinary, and even beautiful. She never failed to delight me (like mariners, I thought of my ship as a person, a female) and she remains one of the loves of my life.

But she is not perfect. Call it my fallacy of anthropomorphism if you will, but I believe that a man-made object cannot be more perfect that the sum of its creators. It can be outstanding, it can be beautiful, but it cannot be perfect. Lovely as she is, my Airbus is no exception. She has her faults.

Her qualities have been called to review by two recent events with very different outcomes: Chesley Sullenberger's heroic handling of a ditching in the Hudson River, and the crash of an A330 in the Atlantic Ocean with the loss of all on board.

All airplanes have what is called an envelope. Fly faster than Va (maneuvering speed) and turbulence or rough handling can result in damage to the airframe. Fly slower than Vs (stall) and the wing can no longer generate enough lift to hold the airplane up. Fly faster than Vd (dive speed) and all manner of bad things can happen, from Mach tuck to control flutter to loss of control. The technicalities of the flight envelope can fill a book and have, many times over. The parameters include aircraft weight, air density (altitude, temperature) and G loading. But the bottom line is that it is the pilot's responsibility to keep the airplane in the envelope, to fly it as it was designed to be flown.

Bernard Ziegler had a different idea.

He was my love's Daddy. You see him in her everywhere you look. She is beautiful, intelligent, accomplished, and refined. She is uncompromising. She is very French.

She has an envelope like any other airplane. She flies with the same aerodynamics as they do. But her Daddy added a new feature to her design: envelope protection.

With the A320 and subsequent models, the pilot cannot “push the envelope”. He can push or pull as much as he wants and she will go to the edge, but not over the cliff. She is impossible to stall.

As long as she is in NORMAL LAW.

Her fly-by-wire control system is impressive in the extreme. There have been no known failures in service. But like us she depends on sensors, eyes and ears. And of course electricity to power her hundreds of computers. Starve her, blind her, or deafen her and you are asking for trouble. Chesley Sullenberger understood her. His first act was to reach up and start the Auxiliary Power Unit. This one strategic move kept power on the aircraft busses as Jeffrey Skiles, the First Officer, went through the engine restart drills. This one strategic move kept her in Normal Law until touchdown.

AF447 was approaching the Intertropical Convergence Zone, the ITCZ, the doldrums. It was night and as usual there was a long line of thunderstorms in the Zone, crossing their track obliquely. The Captain had just left the Flight Deck for his planned rest. The most junior pilot – the relief pilot – was in the left seat flying the aircraft.

Ahead of them a small storm was showing on the radar. Despite its size it was dense enough to reflect all of the energy from their radar. The result – a well-documented phenomenon called attenuation or blanking – was that a gap appeared in the line behind the small storm. AF447 flew around the corner and suddenly the gap was gone. They were plowing into the main line of thunderstorms.

Supercooled water is unusual at FL350 but not unusual in thunderstorms. Drops of supercooled water freeze instantly when disturbed – as for example by a fast-moving aircraft. The temperature that night was an unusually warm minus 40 C., just warm enough to keep the drops from freezing and cold enough so the heating elements in the A330's pitot probes were not powerful enough to keep the probes open. All three pitots were temporarily blocked, cutting off all airspeed information.

She was blind and deaf. Panicked, she shut down her envelope protection and called out to her pilots for help, shutting down the autopilot and autothrust and reverting to Pitch Alternate Roll Direct Law. Visual and aural warnings cascaded across the ECAM and into the speakers. Beautifully designed and prioritized for foreseeable failures, the warnings that night became a powerful distraction, demanding the pilots' attention at just the moment they needed to ignore her.

She was squealing like a stuck pig. If the pilots could have read her right that night, what they would have heard was, I'm gone, guys. I'm outta here. You have control.

Blind, deaf, and still squealing, the A330 handed control to the relief pilot. He pulled back on the sidestick. She zoomed upwards, climbing to FL380 at 7000 feet per minute, rapidly losing energy, her angle of attack increasing toward the stall. In Pitch Alternate Roll Direct Law the pilot's back pressure on the sidestick was also moving the powerful Trimmable Horizontal Stabilizer, moving it slowly to full nose-up, effectively locking them into the stall that would follow momentarily.

Today David Learmount of Flight Global posted a blog titled Being an airline pilot is “A profession in decline”. Is it really? He quotes from William Langewiesche's book Fly by Wire, citing Langewiesche's admiration for Bernard Ziegler and the Airbus and his ambivalent attitude toward airline pilots. I will add another quote from the book:

“What did Ziegler want? He wanted to build an airplane that could not be stalled – not once, not ever – by any pilot at the controls.”

She fell flat, nose and wings level with the horizon, falling not flying, her angle of attack near ninety degrees, her rate of descent 10,000 feet per minute. Four minutes later she hit the water.

Nemesis and Lesson

Here is another quote from Fly by Wire:

“If you design airplanes for (airline pilots) to fly, you must grapple with not only with the existence of a few who are incompetent from the start, but also with the fact that plenty of once-excellent pilots grow unsafe with time. They become arrogant, bored, or complacent. They drink, they fade, they erode.”

Bernard Ziegler is (was) a brilliant test pilot and engineer. (Like me, he is getting older.) He knew that he was on the far right flare of the bell curve. He knew (as do we all) some examples from the left rim of the bell.

I am from somewhere in the middle of the curve. I was lucky, worked hard to maintain my competence, and survived my job. I don't dispute the factuality of the above quote. But I would add a caution:

Underestimate a tradesperson at your own risk.

Chesley Sullenberger knew his airplane, respected her and treated her like an equal. He expected Jeffrey Skiles to act professionally and he did. He was proud of his profession, his trade. That was his true achievement. The successful ditching followed from it, a corollary.

David P. Davies gets it right-way-around in his classic Handling the Big Jets:

“Airline flying is just money for old rope most of the time . . .”

He recognizes, as pilots say, that flying is hours of boredom punctuated by moments of sheer terror.

But he also points out the need for training of the highest quality. That designing an airplane that is capable of landing safely with half its engines failed is of no use if you haven't trained the pilots to do the maneuver. If you haven't given them the confidence that they can.

So pilots: know your airplane. Treat her and your fellow-pilots well. Expect the best from them.

And to everyone, especially homeowners: respect tradespeople. Search out those who are proud of their work. Especially if you're looking for a roofer.