Saint Sully: How About Some Credit for Airbus?
The more I read about USAirways Flight 1549's dip in the icy Hudson River last winter and the more we beatify Chesley Sullenberger, the more I think there's not much more to learn from this accident; nothing below the surface, so to speak. The engines choked on birds, the pilots did a masterful job of ditching, everyone survived. It's that simple.
William Langewiesche's new book, Fly By Wire: The Geese, the Glide and the Miracle on the Hudson which I just completed this morning, doesn't change that view. There are now four books on this subject, according to Amazon, three of them with the word "miracle" in the headline. I'm surprised that Langewiesche's essay characterizes the outcome with this word, for to read his book you can only conclude that the Airbus 320 performed exactly as the engineers who created it designed it to and that Sullenberger and F/O Jeffrey Skiles did everything right. Why is this miraculous? Does not screwing up now merit religious overtones? If there's anything exceptionally fortuitous here, it's that everyone survived. The law of averages dictates some small number would die—just because. Stuff happens. But evidently, 10 to the 9th didn't come calling. (More like 10 squared, I guess.)
Langewiesche is an exceptional stylist with a flair for making lucid for a general audience the determinative minutiae of aviation, specifically the much-maligned fly-by-wire system used in the 320. "Much maligned" deserves qualification here. Boeing aficionados have fought a persistent rear-guard whisper campaign against the Airbus control system and to this day, every accident seems to re-ignite the dying embers of this argument, fanning it to new levels of white heat.
But a core contention of Langewiesche's analysis is that while praise was heaped upon Sullenberger and Skiles (deservedly), the airplane itself deserved a measure of credit. Accordingly, he artfully details the history and philosophy of the Airbus control system, including its tri-level slow-speed/high alpha control law architecture which gave 1549's pilots an edge they wouldn't have had in a Boeing.
"…Sullenberger and Skiles disarmed a bomb on a three-minute fuse. They did it by concentrating on the two really important matters—how to get the engines started, and where to land. 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 [Airbus design engineer] Ziegler's mind, in which computers took care of the menial chores, then conjured up a magic carpet for them to fly."
Although this book doesn't reveal any now-it-can-be-told factoids, it adds interesting texture to the story. For example, moments after the bird strike but before he took the airplane from Skiles, Sullenberger flipped on the APU. When he was asked later why he did this, he had no clear answer, other than to say it seemed like a good idea at the time. With aux power already flowing from the APU, Skiles was able to roll back the left engine—as the checklist directed him to do--to attempt a restart. Up to that point, the barely turning left had been providing the airplane's only electrical power, plus a warm breath of thrust. The right engine was crumped entirely. Had the left side spooled back without the APU on line, the airplane would have reverted to basic control law. Still flyable, but less optimal than the full control, protections and panel Sullenberger had to finesse the ditching.
As Langewiesche reports it, many of Sullenberger's replies at subsequent hearings were plain vanilla responses devoid of detail and perhaps partially calculated to favor the cause of the airline union of which he is a member. The investigation boards convened thus far have evidently been remarkable for their incuriousness on the part of the questioners.
In Sullenberger, we find a man who, for the space of three minutes and 31 seconds, was as focused and as engaged with a machine as it is possible to be, yet not much detail describing what drove his decision making and how the unique design of the Airbus may have shaped it has emerged. But there was one nugget. Here's his reply when asked by an Airbus representative how he picked an airspeed to fly.
"As we were not configured for landing...we didn't have a reference speed displayed on the PFD...so I chose to use a margin above VLS." In the Airbus, VLS is "velocity lowest selectable." With no stored configuration data for what he was about to do, Sullenberger had to guess and guess right the first time.
He did, although not perfectly. Airbus engineering analysis predicted that at full flaps, a pitch angle of 11 degrees and 3.5 feet per second descent would allow the hull to remain intact during impact. Ten seconds before impact, the descent rate was six times that, but Sullenberger—with help from the automation—pulled enough pitch to hit 11 degrees at impact, but at a higher-than-optimal descent rate. He split the difference. As the engineers might have predicted, the hull was damaged, but not so much to preclude complete evacuation.
Speaking of which, the cabin exit brought out both the best and worst in human nature, but probably more of the best. One man forced a woman to the floor during the exit, but prior to touchdown, another offered to take a woman's baby and brace the child against the looming impact, at no small risk to himself. "What more can be said of anyone?" Langewiesche asks.
The NTSB's accident report on 1549 will be done sometime after the first of the year. I'll be surprised if there are any eye-raising revelations, although I'm looking forward to reading the powerplant report to see what kind of damage those geese did. Oh, and for those who complain about the tree-huggers wailing about goose extermination around the New York airports, there's this bit: the ingested geese were determined to be from Canada, not the New York region. They were in their traditional Mid-Atlantic flyway.
If your curiosity about 1549 is insatiable, Fly By Wire is worth a read, if for no other reason than to inform what you think about the Boeing vs. Airbus debate.