Saturday, January 16, 2010

Book Reviews: "Highest Duty" by Capt. Chesley Sullenberger and "Fly By Wire" by William Langewiesche

Highest Duty, Capt.
Chesley Sullenberger
with Jeffrey Zaslow,
William Morrow, 2009
Yesterday was the anniversary of the brief flight of Cactus 1549, the USAir Airbus A320 that on 15 January 2009 departed New York LaGuardia Airport's Runway 4, encountered a flock of migrating Canada geese, and ditched in the Hudson River due to the consequent loss of both engines. As I had a five hour train ride in store I felt it would be a good time to read two accounts of that flight: Highest Duty, written by the Captain who flew the Airbus, Chesley Sullenberger ("Sully" to almost everyone), and Fly by Wire by William Langewiesche.

I wanted to read the two books together because a certain amount of media commotion had accompanied their publication a few months ago. I wanted to see whether the fuss was justified.

Immediately after it became clear that the crew of Cactus 1549 had pulled off a remarkable feat of airmanship and that, somewhat improbably, all 155 souls on board had survived, the main-stream media went into overdrive to crown Capt. Sullenberger as the Hero of the Day. To his lasting credit, he never postured nor claimed the hero's laurels and he has been consistently generous in praising the performance of the rest of his crew, controllers and first responders that were involved in the incident.

Fly by Wire,
William Langewiesche
Farrar, Straus
and Giroux, 2009

The problem was that while Capt. Sullenberger was being hailed far and wide as the sole savior of Cactus 1549 (his own protestations notwithstanding), Langewiesche's book was thought by many to cloud the issue if not actually to rain on the parade. Some claimed (and a few of them may even have actually read the book) that Langewiesche considered the A320's fly-by-wire flight control system to be more responsible for the successful outcome of the day than Sullenberger's airmanship. Howls of protest echoed in the land, fanned by media eager to lead with controversy.

"Sully" himself weighed in, fairly gently after his own fashion, saying in an interview with the NY Times' Christine Negroni, that Fly by Wire “greatly overstates how much it mattered” that the plane he landed in the river featured an automated cockpit. He added: “There are some situations where the automation will protect a pilot, but at the same time a highly automated airplane makes possible other types of errors, so it’s a mixed blessing...and greater knowledge is required to fly a highly automated aircraft.”

And so I sat down with both mens' books, to measure their success in retelling the story of Cactus 1549 and to decide for myself whether the contretemps was justified.

Captain Sullenberger's book is a charming memoir of a decent, steady life. It is well written without being beautifully written. His collaborator, Jeff Zaslow, seems to succeed in remaining unobtrusive...the voice that comes through is very credibly Sully's. He goes back to his north Texas roots and describes the life experiences that formed his values system and readied him to face the challenge of that cold day last January. The portrait is clear - there is nothing not to like about this man.

He addresses briefly the role of automation in the cockpit. In a chapter titled "Managing the Situation" he suggests:

Automation can lower the workload in some cases. But in other situations, using automation when it is not appropriate can increase one's workload. A pilot has to know how to use a level of automation that is appropriate.

He concludes, "...technology is no substitute for experience, skill and judgment."

Then, Captain Sullenberger gets, I think, to the real point and the crux of controversy if one indeed exists:

One thing that has always helped make the airline industry strong and safe is the concept that pilots call "captains's authority." What that means is we have a measure of autonomy - the ability to make an independent professional judgment within the framework of professional standards.

Given that quote, it is easy to see how the full-authority digital control system of the Airbus, with its limits that no pilot can override, may be distasteful to a skilled airman who grew up believing in "captain's authority".

Every few years, I take down from the shelf one of my copies of Stick and Rudder by Wolfgang Langewiesche, and read it again. During the early years of the Second World War, Wolfgang wrote articles for Leighton Collins' Air Facts. He and Collins were intensely interested in improving aviation safety. In particular they were horrified at the regularity with which pilots killed themselves in stall-spin accidents. To Langewiesche, one key to alleviating this ongoing disaster was to spread awareness of the vital role of angle of attack. That became the central theme of Stick and Rudder, published in 1944 and still saving lives today.

Wolfgang Langewiesche was a writer of uncommon skill and lucidity. His son, William Langewiesche, has evidently inherited the DNA that provides for those skills and has added his own remarkably graceful style. The man cannot craft an awkward sentence. Besides his skill with language, he is an aviator of much experience who has displayed a willingness to challenge difficult situations aloft and conventional wisdom on the ground. If anyone was about to get pinned with the label of Contrarian with respect to Cactus 1549 it would be Bill Langewiesche.

And yet...I've read the book. At no point is the author less than respectful and admiring of the airmanship exhibited by Sullenberger and his crew. Very early in the book Langewiesche says that Capt. Sullenberger:

...possessed an attribute that those who mocked him (over the "Hero" tag) had overlooked: he was capable of intense mental focus and exceptional self-control. Normally these traits do not matter much for airline pilots, because teamwork and cockpit routines serve well enough. But they had emerged in full force during the glide to the Hudson, during which Sullenberger had ruthlessly shed distractions, including his own fear of death. He had pared down his task to making the right decision about where to land, and had followed through with a high-stakes flying job. His performance was a work of extraordinary concentration, which the public misread as coolness under fire. Some soldiers will recognize the distinction.

The controversy probably originates some pages later when Langwiesche broadens the focus of the discussion to include the A320's fly-by-wire controls. He says this of Sullenberger's flying:

In retrospect what mattered most to his ultimate success was not what he did, but what he chose not to do, his shedding of distractions, the concentration that he brought to the crisis. It was an exceptional performance, easy enough to dream up in the abstract, but extremely difficult to execute in practice. His physical control of the airplane, however, is another matter, and though nearly flawless, less reflective of unusual skill.

This is the author's introduction to the notion that the Airbus control system offered advantages that reduced the need for remarkable stick-and-rudder skill...as an aviator, Sully had to be without peer but as an airplane driver, he only had to be "good enough." Of course, howls of indignation arose from this "denigration" of Sully's skills.

At this point in his narrative the author introduces us to Bernard Ziegler, a French test pilot and engineer and the primal force behind the development of the fully digital controls of the A320 and its family. Ziegler's objective was to build what Langewiesche describes as "an airplane that could not be stalled - not once, not ever - by any pilot at the controls." And so the airplane incorporates multiple levels of speed and angle-of-attack protection with no provision for pilot override.

Of course, any design strategy has strengths and weaknesses. In response to a comment that the A320 is "easy to fly", Ziegler expressed ambivalence:

Yes, but you know sometimes I wonder if that was not our mistake. Sometimes I wonder if we made an airplane that is too easy to fly. Because in a difficult airplane the crews may stay more alert.

This concept is known in the human factors community as Automation Induced Complacency. I've written about it recently, in this post.

Langewiesche explores in some depth accidents like the Colgan Bombardier Q400 in Buffalo where an Airbus-like control system would probably have prevented the errant Captain from killing all on board, and the Habsheim A320 airshow crash where the Captain creatively found a way to drive the airplane into the ground despite the very best efforts of the control system.

Oddly, both Sullenberger and Langewiesche use the same accident -- AA965, a Boeing 757 that collided with terrain in December 1995 near Cali, Columbia -- to support their disparate views of the value of cockpit automation. To Sully, the story is a cautionary tale regarding automation because it was the Captain's confusion over the operation of the Flight Management System that put the airplane into jeopardy. But Langewiesche looks at how the Airbus control system might well have been just the small bit more efficient in the final emergency climb that would have allowed the flight to clear the mountain peak that it struck, a mere 200 feet below the summit.

In the end, however, despite the length and thoroughness of the author's detour through the thicket of fly-by-wire design philosophy, he agrees that its influence on the outcome of Cactus 1549's flight was not decisive:

They could have done it in a Boeing, too. But it was helpful to their immediate cause that they were working with the product of Ziegler's mind, in which computers took care of the menial chores...

Energy management. He had come to Ziegler's limit: alpha max. Given the circumstances his timing was astonishing and almost perfect. Years in the future...he will have proof in the data from this flare that he was a pilot at the peak of human performance. The fly-by-wire system took it from there. It was a very brief affair. Because of the airplane's inertia, it was probably unnecessary. But for the last few seconds of the glide, with Sullenberger's stick fully back, the computers intervened and gently lowered the nose to keep the wings flying.

So there it is. For three minutes, on the afternoon of 15 January 2009, Chesley Sullenberger flew an airplane as well as anyone has ever flown...and probably as well as anyone ever will. And as he did so, a remarkable digital control system made his job just a bit less difficult. One more quote sums up the reason that there ought to be no controversy here:

Across a lifetime of flying, Sullenberger had developed an intimacy with these machines that is difficult to convey. He did not sit in airplanes so much as put them on. He flew them in a profoundly integrated way, as an expression of himself. He lived through them. He knew their souls.

Captain Sullenberger flew the Airbus A320 in the way it had to be flown to preserve the lives of 150 passengers and the rest of his crew. If he had been flying a Boeing 737-800 he would have flown that airplane in the way that it had to be flown. Enough said.

So if all of this discussion of the Airbus control system is interesting but essentially peripheral to the results of the day, why does William Langewiesche devote such a large part of his book to it? It may be because he is his father's son. Because he knows that not every airline pilot is a Chesley Sullenberger. Because he has seen too many accidents like the Colgan Q400 where an airplane, correctly designed, could have avoided the loss of life. Perhaps the public attention drawn by the odyssey of Cactus 1549 has provided a platform from which to stir up new ideas...or to reinvigorate old ideas.

I'm sure William Langewiesche has read Stick and Rudder more times than I have. He is certainly very familiar with these words published by his father, Wolfgang, 65 years ago:

"Restriction of controls" is an important new trend in aviation. It is the main principal of all the simplified, "family", "foolproof" airplanes - a simple mechanical stop somewhere in the control system that makes it impossible for the pilot to pull the stick back far enough to stall the airplane. The actual engineering of such a control restriction is not quite simple."

Wolfgang goes on to explain a bit about why the engineering of control restriction is "not quite simple." In the 1940's he and his colleagues lacked the technologies that Bernard Ziegler had available in the 1990's. But Wolfgang Langewiesche knew what needed to be done. In a real way, whether created intentionally or not, William Langewiesche's Fly by Wire is an homage to his father's foresight.

Both books - Highest Duty and Fly by Wire - are fine efforts and well worth your time. The authors have my admiration, for their words and more, for the ideas and values behind them.


Christine Negroni said...

This is a lovely and thoughtful analysis of an over-reported and often mis-appreciated event in aviation history. It doesn't seem to me that you are either a writer or air safety specialist by profession but you've made a significant contribution to both fields in this blog. Well done.

Frank Van Haste said...

Dear Ms. Negroni:

Thanks for your kind words. You've made my day!

Best regards,