Friday, July 29, 2011

For Want Of A Nail

I have a fascination with the last irretrievable moment. In every accident, in every major event, there's almost always a definable moment where disaster could have been averted. If only key people had had one key piece of information, if only they'd made one decision differently, everything could have been different.

There was one such moment during the last tragic mission of Columbia. If the manager in charge had pushed for satellite images of the shuttle's underside, the extent of the damage might have been known, and it might have been possible to mount a rescue effort. There's a lot of mights involved ... but we also might have gotten those seven people back alive. And we might be seeing one now, in Washington. But that's not the one I'm talking about today.

On the first of June, 2009, Air France Flight 447 disappeared over the Atlantic Ocean. Its automatic systems had blurted out signals of danger, and then, silence. At the time, I had speculated about what might have gone wrong. Speculation was all it amounted to. Without the flight data recorders, no one would ever know the truth of the matter, and the data recorders were buried under eleven thousand feet of ocean. I fully expected no one would ever see them again.

I vastly underestimated the tenacity of France's Bureau of Investigation and Analysis. In May 2010, they had narrowed the location down to a five by five kilometer area. That gave them a small enough zone to allow a team from the Woods Hole Oceanographic Institute to make a more detailed search. In April of this year, they found the wreckage, and with it not only the flight data recorder, but also the cockpit voice recorder. If that wasn't amazing enough, they were able to recover all of the data from both devices. Truly, this was astounding work, and my hat's off to them.

Now, after sifting through the reams of data available to them, the BEA has issued some preliminary reports. It turns out that some of my initial speculations were right, some less so.

The data clearly tells us that the pitot probes had iced over, corrupting the data going into the air data computers. This meant that the data feeding the primary flight displays weren't any good. What's not clear to me yet is exactly what happened next. They don't say if an updraft lifted the nose of the aircraft, or if the ice on the aircraft caused it to slow to a dangerously low speed. I'm guessing the latter, because they say that the crew pulled the nose of the aircraft up, which they probably wouldn't have done if the aircraft was already nose-high. The main point is, the aircraft was already on the verge of a stall, and lifting the nose made a bad problem worse. The aircraft then simply fell out of the sky.

The preliminary report released today says that it's basically a pilot training problem. Pilots typically have little to no training flying an aircraft manually at that speed and altitude, and therefore have little intuition on how they should recover from a situation like this. The BEA recommendation is to add this condition to the pilot training syllabus.

After thinking about it a bit, I have a few observations of my own.

1) Standby instruments rarely get the respect they deserve. Ideally, your cockpit scan should include your standby instruments, especially in a glass-cockpit airplane. If your air data computers are hosed for whatever reason, your standby instruments may still have good information on what your airplane's doing. If your standby instruments don't agree with your primary displays, you've got a problem. Exactly what kind of problem you won't know, but at least you can start looking. This particular failure cascade seems to indicate that the crew were still flying by the primary displays, up to the point where they no longer had any aerodynamic control. Respect your ISIS, ladies and gents, that's what it's there for.

2) Airbus makes an exceptionally sturdy fuselage. Really, this could apply to any modern composite-structure fuselage. They're absurdly strong. From the initial reports, I expected that the aircraft would have broken up in midair from aerodynamic stresses. A mostly aluminum structure probably would have. But from the wreckage, we know that it was intact when it hit the water. It was doing some pretty serious gyrations on the way down, and didn't come apart. That's solid construction.

3) These days, we can find damn near anything, damn near anywhere. I was sure those recorders were gone forever. Fish food, if there are any fish that live two miles down. Apparently, modern sonar is as good as a searchlight. I don't know exactly how those French submarines were able to narrow the field down as close as they did, and for obvious reasons they're not telling. But it's clear that if they want something found on the ocean floor, it can be found. And that wasn't a guarantee ten, or even five years ago.

4) There's a good reason for all this, besides morbid curiosity. The reason people like me pick disasters apart like this isn't that we're morbid toads. We may be, but that's beside the point. We want to know what happened, and how it happened, so we can stop it from happening next time. If that's even possible. The important lesson to come out of all this is that we've uncovered a gap in pilot training. We have the means at our disposal to close that gap. Thirty minutes of simulator time a year, and a pilot will have "experienced" this situation with enough fidelity that he or she will know what to do if the real thing ever happens. The next time this happens we'll probably never hear about it. The passengers will experience a bout of worse than normal turbulence, the pilots will experience five minutes of bowel-freezing terror, but the airplane will arrive at its scheduled destination. We'd have not known this, if we'd let it alone. Poking and prodding is part of our job. Our duty. Not always the most pleasant part, but an essential part nonetheless.

It's not much consolation for the people who lost loved ones two years ago, but this knowledge, painfully gained, may allow us to save the next one. That's certainly worth something.

Dedicated to the memory of Dr. Don Seath, my first professor in Aerospace Engineering, who passed away in May from pancreatic cancer. You taught me well.

Friday, July 22, 2011

Sesquicentennial, Part XVI: First Clash


There is a misconception common to all belligerent parties in virtually ever war that has occurred in human history. It is a misconception so common that the catchphrases associated with it are almost impossible to link to a particular conflict. "Our boys will be home before the leaves fall." "They'll be home before Christmas." While the second can at least be placed confidently after the reign of Constantine the Great, the former has probably been said in every human language that has ever existed.

For one, while it's true that at a war's outset both sides believe that they will win, one side must be wrong. For another, at a war's outset, each side usually believes -- mistakenly -- that the other side is made up of ineffectual pushovers that can't stand the heat. For recent examples, you need only look to the phrases "Mother of all battles" and "Shock and Awe" for prominent cases on both sides. The same was true a century and a half ago. The same was true throughout recorded history. Truly, some things never change.

The fever produced by the simultaneous forces of a fervent belief in victory coupled with a fixed belief in the other side's inherent cowardice caused the major papers of the North to temporarily push Lincoln away from the plan drafted by his army commander, Lieutenant General Winfield Scott. Scott, you remember, had proposed to first surround the Confederacy, then cut it in half. This would take years, but would be the surest way to bring the Confederacy to defeat. No one was balking at the "sure defeat" part, it was the "it would take years" clause that had them dismayed. With such a fine army encamped, and with such a pusillanimous foe, how could our fine boys but win glorious, prompt victory?

In such passions are horrifying disasters born.

The Army of Northeastern Virginia had come into being out of the various companies, brigades, and divisions that had been assembled from the troops gathered to defend Washington, immediately after the bombardment of Fort Sumter in April, 1861. President Lincoln appointed Brigadier General Irvin McDowell as its commander. General McDowell was under immense pressure from the Northern press to go out and do something. President Lincoln was, as well. McDowell initially resisted such pressure, sure that his men weren't yet ready for such action. McDowell was well-suited to make such a judgement, having been an instructor of tactics at West Point. It was an objection swept aside by Lincoln: "You are green, it is true, but they are green also; you are all green alike." So, on July 16, General McDowell left Washington with the largest army that had yet been assembled on the North American continent, with the assignment to go out, find the enemy, and engage him closely. Their initial objective was a rail junction at Manassas, Virginia.

The rail junction was held by a much smaller Confederate force under Brigadier General P.G.T. Beauregard, of whom we've heard already. In a coincidence that would become commonplace in the years to follow, Beauregard and McDowell had been classmates at West Point. Beauregard, initially, only commanded 20,000 men against McDowell's 30,000. But one of the advantages of sitting on a rail junction? Reinforcements can ride in as soon as you know you need them. Beauregard held all the crossings of the Bull Run, so while McDowell searched for ways to outflank his old classmate, Beauregard sent dispatches by telegraph calling for extra men.

They almost didn't arrive in time. McDowell held Beauregard's attention with part of his force, while he sent 20,000 men in a flanking move to threaten Beauregard's left flank. They forced a crossing at Stone House, and all that stood between them and Beauregard's rear was a single reduced brigade of Confederate infantry. If the orders had been given and received properly, this might well have been the end of it. But they weren't: the Union brigade that had been intended to lead the attack held up to wait for further orders, and the brigade that had been intended to feint in support found itself out in front all alone. Meanwhile, fresh reinforcements arrived, and Beauregard was able to plug the hole, and the battle was properly joined.

In their defense, flanking maneuvers are very complex, and require very close coordination and communication to pull off, even today. In an era when orders had to be delivered by hand, it required well-trained officers and well-drilled troops to have a realistic chance of doing it at all. At this point, the Union had few of either. For while Lincoln was right, and the Confederacy had this problem also, the Confederate President had guessed right, and had put his best men and best troops on the line between Washington and Richmond, expecting that is where the heaviest blow would fall, first.

I've mentioned this hidden advantage before. It's not so much that the Confederacy had better officers, or better soldiers. It's that, having no previously-existing officer corps to placate, Davis could put his most able men in the most crucial commands. It's no mere coincidence that Beauregard was present at both Fort Sumter and at Bull Run.

The Confederates had another crucial advantage in this battle: interior lines of communication. The battle lines between two armies usually curve, the commander who sits on the inside of the curve has a shorter distance through which he has to move men and orders, which makes controlling the battle much easier.

The sum total of all of this is that, while McDowell initially enjoyed significant advantages in manpower and position, his inexperienced subordinates could not make enough use of those advantages to penetrate the Confederate lines. They certainly tried hard enough. And it was a near-run thing even so. During the battle, the Union artillery commander moved two of his guns to the far end of his line, hoping to fire from enfilade into the Confederate army. At about three in the afternoon, these two guns were overrun by the 33rd Virginia. The 33rd Virginia wore blue uniforms, and the Confederate Stars-and-Bars banner had horizontal stripes that, from a distance, looked almost like the Stars-and-Stripes used by the Union. Orders to fire on the captured guns were countermanded by an officer who mistook the Virginians for Union forces. The Virginians turned the guns on the Federals, marking the turn of the tide. McDowell had lost the initiative, and with the arrival of Confederate reinforcements he had lost the manpower advantage as well. He was forced to order a retreat.

The retreat began well enough, but the order of march was bungled by inexperienced officers. An overturned artillery wagon caught fire, sparking a retreat into a rout. Men who had been marching in good order suddenly turned and ran headlong towards their rear. They were joined by the wealthy citizens of Washington, who had turned out with picnic baskets to watch the glorious display. Retreating troops found the roads jammed with carriages.

One Union officer managed to distinguish himself in the humiliating rout: William Tecumseh Sherman was grazed in the knee and shoulder while leading his men against the enemy, and managed to keep his men in better order during the retreat than most. His superiors would remember this, later.

When he saw the enemy in headlong retreat, President Davis urged his commanders to pursue the enemy closely. But, now that the were on the offensive rather than the defensive, Beauregard discovered to his dismay that inexperience is a knife that cuts both ways. The day's fighting had left his men very disorganized, and it took quite some time to get them sorted back into their proper units again. Beauregard elected not to pursue. McDowell was initially afraid of a Confederate counterattack on Washington, but was able to employ aerial reconnaissance (Professor Lowe's balloon Enterprise) to verify that no such concentration of Confederate forces was happening. Both armies withdrew from the field.

The reaction on both sides could be fairly characterized as shock. The Northerners were shocked when their much-anticipated glorious victory had turned into an ignominious rout. The Southerners were shocked to discover that the Yankees would put up a vigorous fight, after all. Both sides came to the sudden realization that this would be a long war, far longer than many had anticipated. It was now clear that victory would come with a staggeringly high price tag. And it was equally clear that defeat would carry a price still higher. And, above all, one thing was now known with crystal clarity:

The only men who'd be home before the leaves fell would be the maimed and the dead.

Friday, July 08, 2011

Video Del Fuego, Part XLVI

Atlantis took to the skies today for the last time, closing the books on thirty years of Space Shuttle launches from Kennedy Space Center. For the sixth time, we've seen the last launch of an American spacecraft series. As a salute to NASA's fifty-year history of manned spaceflight, here they are: the swan songs.

First: Gus Grissom on America's second spaceflight, Liberty Bell 7, the last flight of the Mercury-Redstone series.

Second: The last flight of the Mercury program, Gordon Cooper aboard Faith 7.

Third: Jim Lovell and Buzz Aldrin on Gemini XII.

Fourth: Gene Cernan, Jack Schmitt, and Ronald Evans on Apollo 17. On this December day in 1972, some say the sun rose twice...

Fifth: That wasn't the end for Apollo, though. Apollo spacecraft would fly four more times, on Saturn IB rockets. The last one would fly in July 1975, carrying Thomas Stafford, Deke Slayton, and Vance Brand on a rendezvous with Alexei Leonov and Valery Kubasov during the Apollo-Soyuz mission.

Sixth: The next "last one" wouldn't come for another thirty-six years. Today, Atlantis flew into orbit for the last time, carrying Chris Ferguson, Douglas Hurley, Sandra Magnus, and Rex Walheim towards the International Space Station.

As of this writing (11AM Friday) no videos of the launch had been posted to YouTube yet. So, the roll-out will have to stand in for now.

(Addendum, 10Jul11: NASA TV comes through.)

Which spacecraft will be number seven? That isn't yet clear. What is perfectly clear, though, is that there will be one. Despite the problems we're facing, America isn't prepared to give up on this enterprise just yet. Besides, I've got a sneaking suspicion that we've already seen lucky number seven's prototype...

And the journey continues!