The Limits of Technology, A Chilling Reminder
Who can forget the horror of learning, a few years back, that a modern Airbus A330-200 aircraft simply vanished over mid-Atlantic, initially without a trace?
Over the weekend, the Telegraph published a chilling analysis of the June 1, 2009 crash of Air France Flight 447 from Rio de Janeiro to Paris. After the autopilot disconnected in a thunderstorm--a fail-safe response to faulty airspeed data from frozen pitot tubes--the pilot flying AF447 commanded excessive nose-up trim, entering a deep stall. Incredibly, the pilot held this attitude throughout the plane's descent.
For most of its four-minute, 7-mile plunge, AF 447 could have resumed controlled flight if the pilot flying had lowered the nose and held the attitude long enough to regain flying speed. This basic stall recovery procedure is taught to every pilot in initial training and drilled repeatedly in flight checks.
What went wrong? In a word: technology. Too much technology in between the pilots and the aircraft.
But there is another, worrying implication that the Telegraph can disclose for the first time: that the errors committed by the pilot doing the flying were not corrected by his more experienced colleagues because they did not know he was behaving in a manner bound to induce a stall. And the reason for that fatal lack of awareness lies partly in the design of the control stick – the “side stick” – used in all Airbus cockpits.
Cockpit controls in most modern airliners are connected to computers, not directly to engines and flight surfaces. Both Boeing and Airbus make extensive use of such "fly-by-wire" systems. Where Airbus goes further--a step too far in the case of AF447--is in eliminating the tactile signaling provided by the older controls. In a conventional aircraft, the pilot flying commands a nose-up attitude by pulling the stick back and the stick on the other side of the cockpit likewise moves aft, providing feedback to the PNF (pilot not flying). Boeing emulates this control behavior in its fly-by-wire aircraft, Airbus does not. Relax back-pressure in a new Boeing airliner and the nose will lower to its previously trimmed position, just like an old-style cable-and-hydraulics plane. In an Airbus, the computer carries on with the last command input until receiving a new one, even though the stick is visibly in the neutral position.
Under normal circumstances, the Airbus approach provides a lower pilot workload--a better "user experience" in Web 2.0-speak. However, in the corner case of an emergency with multiple instrument failures, overloaded pilots lack the physical cues that would likely have saved 228 souls on board AF447.
And the problem of too much well-meaning-but-intrusive technology goes beyond the flight controls: even the design of the computer-automated stall warning contributed to the disaster.
Bonin’s insistent efforts to climb soon deprived even the computers of the vital angle-of-attack information. An A330’s angle of attack is measured by a fin projecting from the fuselage. When forward speed fell to 60 knots there was insufficient airflow to make the mechanism work. The computers, which are programmed not to feed pilots misleading information, could no longer make sense of the data they were receiving and blanked out some of the instruments. Also, the stall warnings ceased. It was up to the pilots to do some old-fashioned flying.
With no knowledge of airspeed or angle of attack, the safest thing at high altitude is to descend gently to avoid a stall. This is what David urged Bonin to do, but something bewildering happened when Bonin put the nose down. As the aircraft picked up speed, the input data became valid again and the computers could now make sense of things. Once again they began to shout: “Stall, stall, stall.” Tragically, as Bonin did the right thing to pick up speed, the aircraft seemed to tell him he was making matters worse. If he had continued to descend the warnings would eventually have ceased. But, panicked by the renewed stall alerts, he chose to resume his fatal climb.
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Comments:
Mar '11
Re: The Limits of Technology, A Chilling Reminder
I'm an old stick-and-rudder pilot, myself. Not instrument-rated as I prefer to see where I am going.
I'm not sure I would blame technology, per se. More a case of bad design. Boeing seem to be much better in this respect, in keeping the plane feeling and behaving like a real plane, rather than a computer game. That way, pilots can respond in the way they were trained to respond.
Re: The Limits of Technology, A Chilling Reminder
To guys like me who struggle through incredible fear and stress to get on an airplane, you've made matters worse, George.
Ignorance is bliss. I did not need to know this!
Wish I had a mind eraser.
Dec '10
Re: The Limits of Technology, A Chilling Reminder
George,
This isn't really about the limits of technology but about the limits of reality. How we function successfully in the world can be presented very simply by a sequence: Idea..Reality..Idea..Reality..Idea.. Reality..etc. Each time we form our idea we then accept the results of its interaction with reality. When we try to short circuit the loop and lock reality out we are in for it. This is what Obama and company are doing politically. They shrill out the reality and rush on to their next idea. Of course, their next idea is very much like the last idea because it wasn't tested against reality.
The control system of the A330 didn't provide better "control" it provided the better "illusion of control". This is also what Obama does. His smooth delivery of banal bromides provides the superior illusion of control. However, now that many many people in this society have experienced the reality of his illusion they will be looking for a new algorithm in the White House.
Opportunity Mitt.
Regards,
Jim
Edited on May 1, 2012 at 2:42amRe: The Limits of Technology, A Chilling Reminder
David Williamson: I'm an old stick-and-rudder pilot, myself. Not instrument-rated as I prefer to see where I am going.
I'm not sure I would blame technology, per se. More a case of bad design. Boeing seem to be much better in this respect, in keeping the plane feeling and behaving like a real plane, rather than a computer game. That way, pilots can respond in the way they were trained to respond. · 7 minutes ago
David, I agree: the Airbus design flaw is putting the technology between the pilots and plane--the aviation equivalent of bubble-wrap--rather than deploying it, as Boeing does, to intimately connect the pilots to the flying machine at the other end of the microprocessor.
I am instrument-rated and the old adage drilled into my head is "power plus pitch equals performance." At no point during the AF447 tragedy, before the captain intervened in the final seconds, did anybody mention pitch. All the blanked displays, conflicting warnings and erroneous readouts distracted the pilots from basic flying. The way Airbus implements its fly-by-wire is surely a contributing factor.
Aug '10
Re: The Limits of Technology, A Chilling Reminder
Remember that flying the scheduled airlines is by far the safest way to travel.As a long time pilot and a computer usability engineer, I've long thought that airbus's cockpit usability had serious issues. This isn't the first accident in which the fly-by-wire system in that plane was at least a partial cause. Hopefully cockpit design engineers will learn valuable lessons from this.
Mar '11
Re: The Limits of Technology, A Chilling Reminder
Was the fly-by-wire system in this aircraft the same as the one on the Airbus plane which overshot the runway and crashed in the forest during a demo flight?
I heard a program several years ago on NPR (yes, go ahead and stone me!) about the philosophy behind Airbus' computer overrides when an airplane reaches certain limits, and how it arguably causes as many crashes as it prevents.
Re: The Limits of Technology, A Chilling Reminder
James Gawron: The control system of the A330 didn't provide better "control" it provided the better "illusion of control". This is also what Obama does. His smooth delivery of banal bromides provides the superior illusion of control. However, now that many many people in this society have experienced the reality of his illusion they will be looking for a new algorithm in the White House. · 3 minutes ago
Edited 2 minutes ago
Jim, given our predilection for public policy hereabouts, I thought long and hard before posting a purely aviation-related item. In the end, I decided to give in to the under-appreciated Nerd Side of the Force. Now, thanks to you, I have a connection to the coming campaign.
Edited on May 1, 2012 at 2:52amNov '10
Re: The Limits of Technology, A Chilling Reminder
George Savage
I can't understand this part. Stall warning -> pitch up? Where's the logic in that?
Jun '10
Re: The Limits of Technology, A Chilling Reminder
It's true that a lot of accidents these days are caused by overreliance on technology. But then, one most not lose the bigger picture: Many fewer accidents occur due to the increased use of technology.
Airbus' automatic and fly-by-wire systems tend to get the brunt of this criticism, I suspect, because they have tended to have lousy user interfaces and feedback mechanisms (this one being one example) -- why, exactly, I'm not sure. But remember that most accidents are still caused by pilot error, whether it's a massive blunder or CFIT (controlled flight into terrain; e.g., flying a perfectly functioning plane into the ground)
Jun '11
Re: The Limits of Technology, A Chilling Reminder
As a Delta Technical Operations guy, I can say that it was a beautiful thing in aircraft maintenance when we whittled our fleet down to an all Boeing fleet ( I don't remember the years). Now we are back to a hodge podge again including Airbus.
I like Boeing a lot.
Oct '10
Re: The Limits of Technology, A Chilling Reminder
I am commercially and instrument and type rated in a very light jet aircraft. The moral of this story is that automation can be deadly. The three pilots kept trying to understand computer messages when they should have simply flown the airplane. In fact, if they all would have put their hands up in surrender, the airplane would have recovered, since the design of all modern aircraft is inherently stable. The copilot in the right seat apparently panicked and kept pulling back on the controls, i.e. climbing, although the plane was stalled and sinking. The Airbus controls are not mechanically linked and so the left seat pilot control was not the same as the right seat. Burt Rutan did a great analysis of this this accident on line some time ago. He was not complimentary of the pilot skills exhibited.
Mar '11
Re: The Limits of Technology, A Chilling Reminder
Two thoughts:
1. This issue was handled decades ago for fighter pilots. I believe it was the early F-16's that had a NON-MOVING stick that responded to pressure. It was a gee-whiz device that was put into the early test birds simply because they could do it. The pilots hated it and demanded a normal stick. Airbus made a bunch of design choices not out of need, but of gee-whiz this would be cool if...
2. Airbus is a government-owned and government-operated manufacturer. They exist, and will continue to exist, only because they are too politically important to fail. I've read too much to believe that their products are reliable.
I'd feel safer on a Russian IL-86 (clunkier than a Airbus, but good workhorse planes).
Sep '10
Re: The Limits of Technology, A Chilling Reminder
Tommy De Seno: To guys like me who struggle through incredible fear and stress to get on an airplane, you've made matters worse, George.
Ignorance is bliss. I did not need to know this!
Wish I had a mind eraser. · 1 hour ago
Any Obama speech acts as a mind eraser.
Aug '10
Re: The Limits of Technology, A Chilling Reminder
142 Plane Crash Victims Were Statistically More Likely To Have Died In A Car Crash - The Onion:
Edited on May 1, 2012 at 3:45amRe: The Limits of Technology, A Chilling Reminder
Aeromir, I differ with you on one small but important point. You are of course correct that modern aircraft will tend to recovery if left unmolested, but the Airbus design does not allow this to occur. If you let go of the stick on an Airbus that is in an unusual attitude, such as the deep stall described above, it will stay there. This is because the computer executes the last command input by the stick: you do not need to maintain pressure on the stick for it to stay put. If you want to lower the nose, you need to command it to do so. Sadly, releasing the controls is insufficient.
You are absolutely correct that the pilots dropped the airplane while tending to the computer. Aviate, navigate, communicate, in that order.
Re: The Limits of Technology, A Chilling Reminder
Not JMR
George Savage
I can't understand this part. Stall warning -> pitch up? Where's the logic in that? · 50 minutes ago
I speculate that the pilot may have seen a factitiously high airspeed indication, which can occur with a frozen pitot tube when climbing, as occurred early in the accident sequence. With no angle-of-attack indication and a stall warning that stopped with sustained nose-up inputs but then resumed after the pilot flying briefly entered the correct recovery inputs, it was a confusing situation. He may have erroneously thought he was experiencing a mach overspeed upset (speed brakes were deployed at one point during the descent).
It is very tempting to dump on the pilots. Clearly, they mismanaged an eminently survivable situation. However, once a pilot falls behind an airplane in instrument conditions cognitive performance declines dramatically. It is impossible to describe the extent of the IQ hit unless you've been there (ask me how I know). It feels as though your brain is a runner trapped in molasses. Not a great place to be when seconds count.
Edited on May 1, 2012 at 4:11amRe: The Limits of Technology, A Chilling Reminder
Tommy De Seno: To guys like me who struggle through incredible fear and stress to get on an airplane, you've made matters worse, George.
Ignorance is bliss. I did not need to know this!
Wish I had a mind eraser. · 2 hours ago
Sorry to alarm you, Tommy.
The Airbus cockpit design issues are very real, as is the opportunity for improved training. Even so, I won't hesitate to hop on an Airbus aircraft for a commercial flight. Statistically speaking, the company makes very safe airplanes.
Edited on May 1, 2012 at 4:16amDec '10
Re: The Limits of Technology, A Chilling Reminder
George Savage
James Gawron: The control system of the A330 didn't provide better "control" it provided the better "illusion of control". This is also what Obama does. His smooth delivery of banal bromides provides the superior illusion of control. However, now that many many people in this society have experienced the reality of his illusion they will be looking for a new algorithm in the White House. · 3 minutes ago
Edited 2 minutes ago
Jim, given our predilection for public policy hereabouts, I thought long and hard before posting a purely aviation-related item. In the end, I decided to give in to the under-appreciated Nerd Side of the Force. Now, thanks to you, I have a connection to the coming campaign. · 27 minutes ago
Edited 25 minutes ago
George,
The Nerd-Side is under-appreciated. Unfortunately, we have too often absorbed this and under-estimated the worth of the Nerd good judgment.
No fad, no trend, no money, no technology will ever be able to substitute for good judgment. Good Judgment has a couple of friends, Pure Genius and Earnest Faith.
Regards,
Jim
Re: The Limits of Technology, A Chilling Reminder
James Gawron
No fad, no trend, no money, no technology will ever be able to substitute for good judgment. Good Judgment has a couple of friends, Pure Genius and Earnest Faith.
Regards,
Jim · 9 minutes ago
Flight of the Phoenix is an awesome movie. One of my favorite Jimmy Stewart pix. Thanks for reminding me.
Feb '11
Re: The Limits of Technology, A Chilling Reminder
The lack of a tactile interconnect between Captain and First Officer sidesticks seems like a very bad idea...I presume the justification was that a handoff phrase ("your airplane," or something equivalent in French) would always be used when changing who has the controls, but clearly this is not always realistic under extreme pressure.