And hang on, fumbling over the physics of deceleration wasn't my only mistake:

"Patrick, your analysis of the JetBlue 292 mishap gives the false impression that landing gear anomalies are by nature innocuous. As you should know, some are and some aren't. Remember, it was a blown tire that led to the Concorde crash some years ago."

That's a good point, actually, though it tends toward apples and oranges; nose gear versus main gear. Malfunctions involving a plane's forward (nose) landing gear are by nature innocuous. Those involving main-gear tires beneath the wings and fuselage? Well, that's a little different, and occasionally dangerous.

How so? Failure of a main-gear tire at high runway speed, particularly on takeoff and when a plane is heavily loaded, can induce all sorts of trouble, from greatly reduced braking capabilities to the chance of explosion or fire. Making things worse is the possibility that a single failed tire will propagate the failure of those around it. On most larger planes, the main-gear units are split into bogies of four tires each. On the 747 for instance, 16 wheels are grouped in four separate assemblies. On the 767, 757, and Airbus A330, among others, you'll find two groups of four. It's not unheard of for a blown tire on one bogie to quickly become a blowout of two, three, or four.

Ironically, with JetBlue in mind, tire trouble is, to a pilot, considerably scarier on takeoff than on landing -- the velocities are higher, the plane is heavier, most of the runway is behind you, etc. A high-speed runway abort with multiple expired tires can be a dicey operation. For this reason, a crew will in most cases opt to continue the takeoff, if at all possible, and deal with the problem once airborne.

Not that it happens very often, and most modern airliners are protected with highly sophisticated anti-skid systems, brake-temperature readouts in their cockpits, and wheel-well fire suppression systems in the landing-gear bays.

Notice I say "modern." One such plane sorely lacking such features was that old DC-8 freighter I used to fly. Ask the typical flier what he or she fears most, and you'll hear things most pilots rarely worry about: turbulence, lightning, wings snapping off. People don't think much about landing gear, but after almost four years of crewing that ancient Douglas I'd developed a hierarchy of potential nightmares, and tire disasters were tops on the list. A story:

Late one night in 1998 we were going from Brussels to New York. The plane was at its highest allowable taxi tonnage and the ground controllers gave us a long, circuitous route to runway 25R. Rolling along the apron in predawn darkness, we suddenly heard a bang and felt a shudder. A small pothole, we concluded, and kept going, as otherwise the aircraft felt normal.

Then, just as we turned onto the runway and were cleared for takeoff, we heard a second bang, followed rapidly by a third, and then a fourth. And with that, the airplane -- all 355,000 pounds of it -- seized and wouldn't move.

Turns out the first noise we'd heard was one of the DC-8's eight main tires violently giving up the ghost (like a 757 or 767, they are paired in two sets of four). At max weight and after several sharp turns along the taxiways, it was only a matter of time before the adjacent one met a similar fate. With two gone, stress on the remaining two sent them popping as well. We were lucky things happened when it did, and not at 150 knots, with the threshold lights fast approaching.

The runway was closed for more than seven hours until the crippled plane could be unloaded, de-fueled, and towed away for repairs.

Aircraft tires are filled with inert nitrogen, not air, to reduce the likelihood of explosion or fire, and fuse plugs are designed to trigger automatic deflation should temperatures exceed a certain value, such as following an abort. In 1986, a Mexicana 727 went down after takeoff from Mexico City, killing 167 people. An overheated brake caused one of the plane's four main tires to burst, with shrapnel severing fuel, hydraulic, and electrical lines. The tire had been erroneously serviced with air instead of nitrogen. According to one summary: "The air, under high temperature and pressure, resulted in a chemical reaction with the tire itself. This led to a chemical explosion of the tire." (The '86 crash is one of the few black marks against Mexicana, one of the world's oldest airlines.)

Inflation pressure too is important. At high speeds, an underinflated tire can generate tremendous amounts of heat. In 1991 a Canadian-registered DC-8 crashed near Jeddah, Saudi Arabia, killing 261 people (it was a charter flight, bringing Hajj pilgrims home to Nigeria). A single, underinflated tire transferred energy to a second tire, and both came apart during takeoff roll. Bits of material then began to burn after gear retraction. Fire spread through the cabin as the plane circled back for an emergency landing, with seats and their occupants ejected through the fuselage.

And as we've been reminded, the fiery crash of an Air France Concorde five summers ago was linked to a fuel tank puncture brought on by an exploding tire.

Exactly what role that tire played, and why it burst in the first place, is the topic of some debate. After weeks of lambasting the media for its distortion-laden aviation coverage, I'm pleased to point readers to David Rose's outstanding analysis of the Concorde disaster. It's not a new piece, written in 2001 for Britain's Observer, but timely to this discussion. Moreover, in addition to his provocative indictment of Air France and the official investigation itself, Rose superbly illustrates how air crashes are rarely the result of a single, definitive cause.

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