Cockpit Confidential (13 page)

Which isn't to say that no plane has ever aborted its takeoff and gone skidding off the end. It happens from time to time—meaning very infrequently. With hundreds of tons moving at hundreds of miles per hour, things don't always work out exactly the way the data says they will. To help the cause, modern airplanes are equipped with extremely sophisticated brakes
and
extremely sophisticated pilots.

Bigger planes have incredibly powerful engines and fancy high-lift devices (flaps, slats, and such) that allow them to take off and land at relatively low speeds. The leviathan A380, for example, has the same approach and landings speeds as the much smaller A320. It's wrong, therefore, to assume a bigger plane, by its nature, requires a longer runway than a smaller one. It might or it might not. A lightly loaded 747 might use
less
runway than a maxed-out 737, a quarter of its size.

The amount of thrust used for takeoff is always more than enough, so typically at a thousand feet or so, depending on the profile, it's reduced to what we call “climb power.” This saves wear-and-tear on the engines and keeps the plane from exceeding low-altitude speed restrictions. The plane is neither descending nor decelerating; it's just not climbing as rapidly.

It might surprise you to learn that despite the impressive roar and acceleration, airliners seldom take off at full available power. Maximum thrust is used when conditions (weight, runway length, and weather) dictate, but normally they don't, allowing for a reduced setting. This is healthier for the engines, and the power is still there if you need it.

Time again for this book's two most important and annoying words: it depends. Certain planes always use higher speeds than others, but from there it differs with the usual suspects: weight, flap settings, wind, and temperature. To ballpark it, a regional jet might take off at 130 knots and land at 110 knots. An Airbus or Boeing could be doing 40 knots faster on either end. On the 757s and 767s that I fly, liftoff speeds fall anywhere between 140 and 170 knots. Touchdown speeds range between 130 and 150 knots. Landing speed will always be the slower of the two, and landing uses up considerably less runway than taking off.

There aren't. The numbers correspond to the runway's magnetic (compass) orientation. Picture a 360-degree circle, with the cardinal points (north, south, east, and west) of 360, 180, 90, and 270. To figure out which way a runway is aligned, add a zero. Runway 31 is pointing 310 degrees, toward the northwest. The opposite end of the same strip would be designated 13, pointing 130 degrees, or southeasterly. Thus one runway is actually two runways. When laid in parallel, runways are given a letter suffix of L or R, designating left or right. (Taxiways, if you're wondering, use alphabetical or alphanumeric designations—A, N, KK, L3, and so on—referred to using the phonetic alphabet: Alpha, November, Kilo-Kilo, Lima-3.)

An airport can have several runways aligned in all manner of geometry—triangles, perpendiculars, parallels, crisscrossing, tic-tactoe—or just one (which is to say two). Seen from above, Chicago's O'Hare looks like an aerial view of the Nazca Lines, with seven separate strips for a whopping fourteen total runways. There's no standard length, which like the dissimilar outfield fences of Major League Baseball stadiums, adds some, uh, character to particular airports. La Guardia and Washington-Reagan are known for short, less forgiving runways of about 7,000 feet. Runway 31L at JFK is more than twice that. Ten or eleven thousand feet is a classic “long” runway.

Excavated, paved, lighted, and instrumented for all-weather ops, building a runway is a much more serious undertaking than slapping down asphalt and painting stripes on it. The sixth runway at Denver International carried a tab of $165 million.

Maybe you've seen those “world's scariest landings” and “world's most dangerous airports” lists that pop up time to time on the web and elsewhere. Take them with a grain of salt, because no commercial airport is unsafe. If one were, no airline would be flying there. Pilots speak of certain airports as challenging, which is a completely different thing. As in any profession, some tasks—in this case, some takeoffs and landings—are more difficult and work-intensive than others, but they remain well within the capabilities of the people trained to perform them.

What makes an airport challenging is usually one of two things, either alone or in combination: runway length and surrounding terrain. Many Andean, Himalayan, or Rocky Mountain airports feature complicated arrival and departure patterns due to nearby peaks. New York's La Guardia, Chicago's Midway, and São Paulo's Congohnas airports are among those known for their stubby runways.

Those complicated patterns might be work-intensive, but that doesn't make them scary. Likewise for short runways. As we saw a few questions ago, a runway must always be long enough to ensure a safe takeoff. Landings work much the same way; a pilot does not eyeball the runway and conclude “that looks about right,” then hit the brakes and hope for the best. Taking weight and weather into account—including penalties for a surface slickened by ice, snow, or rain—data must show that a plane can stop within a maximum of 85 percent of the total available distance. Takeoffs and landings are more scientific than people realize. We hear a lot about pilots needing to possess expert judgment and seat-of-the-pants skill. While that may be true, there is almost nothing subjective about choosing where to land or take off from.

It goes without saying, though, that shorter runways leave limited margin for error, and history records numerous overrun accidents, some of them fatal. During severe weather, things can get squirrelly. Low visibility, gusty crosswinds, and slippery surfaces can combine to throw an approach off kilter. The best way—indeed the right way—of dealing with an unstable approach is to discontinue it. Which brings us to the next question…

There you are, belted in for landing. The approach is smooth, the weather clear. Down, down, down you come. At 500 feet or so, you can make out the writing on billboards; touchdown is only seconds away. Then, without warning, the engines roar. The aircraft pitches up sharply and begins to climb, groaning and shuddering as the landing gear retracts and the flaps are reset. The ground falls away; the plane banks sharply. You grip the armrest. What the heck is happening? A long minute later, the PA crackles and the captain speaks. “As you're aware,” he says, “we had to abandon our approach and make another circuit. We're circling back around for another approach and will be on the ground in about ten minutes.” If you fly often, you have experienced this scenario at least once. The maneuver is called a go-around, and it holds a special place in the fearful flyer's pantheon of worries. I read about go-arounds all the time, luridly described in emails from terrified travelers who wonder if they've narrowly escaped with their lives.

The truth is pretty boring: go-arounds are fairly common and seldom the result of anything dangerous. In most cases it's a minor spacing issue: controllers aren't able to maintain the required separation parameters or the aircraft ahead has not yet vacated the runway. Not an ideal situation, but let's be clear: this is
not
a proverbial near miss. The reason you're going around is to
prevent
a near miss. Actual instances where a collision is narrowly averted do occur, but they are exceptionally rare.

Other times, traffic has nothing to do with it. A variant of the go-around, spoken of somewhat interchangeably, is the missed approach, when a plane pulls off the same basic maneuver for weather-related reasons. If, in the course of an instrument approach, visibility drops below a prescribed value or the plane has not made visual contact with the runway upon reaching the minimum allowable altitude, the crew must climb away (often followed by a diversion to an alternate airport). A go-around will also be initiated any time an approach becomes unstable. Glidepath deviations, a too-high rate of descent, severe crosswinds, a windshear alarm—any of these may trigger one.

As for the steepness or suddenness of the climb, that is the manner in which any go-around is executed. There's no need to dilly-dally around at low altitude. The safest direction is up—as quickly as practical. The abrupt transition from a gentle descent to a rapid climb might be noisy and jarring, but it's perfectly natural for an airplane.

For pilots, executing a go-around is very straightforward, but also quite work-intensive. The first step is advancing the power to go-around thrust, retracting flaps and slats to an intermediate position, and rotating to a target pitch—somewhere around 15 degrees nose-up. Once a climb is established, the landing gear is raised. Flaps and slats are then retracted, followed by additional power and pitch adjustments. Once at level-off, the FMS may need to be reprogrammed, the autoflight components reset, checklists run, the weather checked, and so on—all while taking instructions from air traffic control. There is a lot of talking and a rapid succession of tasks. This is one of the reasons you might not hear from the pilots for several minutes.

And when you finally do hear from the cockpit, the explanation is liable to be brief and, much as I hate to say it, maybe not as enlightening as it could be. The reality is, pilots and microphones aren't always a good mix (
see communications
). In our attempts to avoid technical jargon and simplify complicated situations, we have a proclivity for scary-sounding caricature. Granted, passengers do not need a dissertation on the nuances of ATC spacing restrictions or approach visibility minima, but statements like “We were a little too close to that plane ahead” paint a misleading, if not terrifying, picture. Later that night, passengers are emailing their loved ones (or me) with a tale of near death, whereas the pilots have probably forgotten about it.

The standard procedure for bad-weather approaches is, and has been for decades, something called the instrument landing system, or ILS. A plane follows two guidance beams, one horizontal and one vertical, transmitted from antennae on the ground. With the two beams centered in a kind of electronic crosshair, an airplane descends to a designated height—usually about 200 feet above the ground, though sometimes higher or lower—at which the runway must be visible for landing. GPS, now in general use for en route navigation, is still an emerging technology when it comes to approach and landing.

To organize the flow of traffic, ATC will commonly assign ILS approaches even when the weather is good. But on occasions when you really need them, there are three categories of ILS—Cat I, Cat II, and Cat III (in pilot-speak we say “cat” not “category”)—with different visibility and equipment requirements for each. Cat I is the standard. Cats II and III are more complicated and can take you all the way down to zero visibility—provided the runway, airplane, and pilots are equipped, authorized, and trained for it (this isn't always the case).

For departures it works similarly. When takeoff visibility drops to certain levels, the runway and the crew both require specific authorization. With the runway it's mostly about lighting and markings. For the crew it depends what minimums you're trained and approved for. We're in Amsterdam, and the visibility on runway 36R is 250 meters. Can we go? Better get the charts out and check.

Runway visibility is measured using something called RVR (runway visual range), where a series of light-sensitive machines arrayed along the runway provides values in feet or meters.

Now and then a pilot doesn't land as smoothly as he intends to. Although passengers put a lot of stock in the smoothness of a touchdown, this is hardly an accurate benchmark of skill. Judging a flight by its landing is a bit like judging an entire paragraph by a single awkward word or punctuation mark. It's a small, if occasionally memorable, part of a much bigger picture. And a firm or “crooked” landing is often exactly what the pilot is aiming for. On short runways, the priority is getting the plane safely onto the ground within the touchdown zone, not finessing it. The correct technique in a crosswind is a slightly skewed alignment, with one set of tires hitting the ground before the other.

Jet engines do reverse, and that's exactly what you're hearing. The pilot manually raises a lever, one for each engine, causing deflector panels to lift or slide into place. If you're seated with a view of the engines, you can see these deflectors quite clearly. Once they're positioned, which takes a second or two, engine power is increased—though only so far; full reverse thrust is only a fraction of available forward thrust. It's not a true, 180-degree redirection, but more of a semi-forward vector, like the effect of blowing into your cupped hand. (Turboprop engines reverse as well; the propeller blades rotate longitudinally, forcing air forward rather than backward.) The amount of power used ranges with runway length, brake settings, surface conditions, and, to an extent, which taxiway turnoff the pilots intend to use. Although reversing is helpful, it's the brakes that do most of the stopping, assisted by drag from the flaps and deployment of spoilers. That 85 percent runway length limit we talked about earlier is calculated
without
use of reverse. Whatever help it gives you is a bonus.