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2. Elements of Unease: Turbulence, Windshear, Weather & Worry

Turbulence: spiller of coffee, jostler of luggage, filler of barf bags, rattler of nerves. But is it a crasher of planes?

Judging by the reactions of many airline passengers, one would assume so; turbulence is far and away the number one concern of anxious passengers. Intuitively this makes sense. Everybody who steps on a plane is on some level uneasy, and there’s not a more poignant reminder of flying’s innate precariousness than a good walloping at 37,000 feet. It’s easy to picture the airplane as a helpless dinghy in a stormy sea. Boats are occasionally swamped, capsized, or dashed into reefs by swells, so the same must hold true for airplanes. Everything about it seems dangerous.

Except that, in all but the rarest circumstances, it’s not. For all intents and purposes, a plane cannot be flipped upside-down, thrown into a tailspin, or otherwise flung from the sky by even the mightiest gust or air pocket. Conditions might be annoying and uncomfortable, but the plane is not going to crash. Turbulence is an aggravating nuisance for everybody, including the crew, but it’s also, for lack of a better term, normal. From a pilot’s perspective, it is normally seen as a convenience issue, not a safety issue. When a flight changes altitude in search of smoother conditions, this is by and large in the interest of comfort. The pilots aren’t worried about the wings falling off, they’re trying to keep their customers content and relaxed (and everybody’s coffee where it belongs).

In the cockpit we see the altimeter jiggle ever so slightly while the anxious flier perceives a free-fall, overestimating the roughness by orders of magnitude. “We dropped like 3,000 feet in two seconds!” In truth altitude, bank, and pitch will change only slightly, and inherent in the design of airliners is a trait known to pilots as “positive stability.” Should the aircraft be shoved from its position in space, its nature is to return there, on its own and with no drastic input from the crew.

I remember we hit some pretty rough air one night on the way to Europe, about halfway across the Atlantic. It was the kind of turbulence people tell their friends about. It came out of nowhere and was bad enough to knock over some carts in the rear galley. I had my seatbelt on, as pilots always do, but reflexively put my hand against the cockpit ceiling to brace myself. During the worst of it, to the sound of crashing plates, I recalled an email. A reader had asked about the displacement of altitude during times like this. How many feet is the plane actually moving up or down, and side to side? I kept a close watch on the altimeter. Fewer than 50 feet, either way, is what I saw. Ten or twenty feet, most of the time. Any change in heading — i.e. the direction our nose was pointed — was all but undetectable.

At times like this pilots will slow to a designated “turbulence penetration speed” to ensure high-speed buffet protection (don’t ask) and, worst case, to prevent damage to the airframe. This speed is close to normal cruising speed, however, so you probably won’t notice the deceleration from your seat. They can also request higher or lower altitudes, or ask for a revised routing. (This is common domestically, but difficult to coordinate on oceanic crossings. Over the ocean, unless conditions become severe, you’re more or less stuck with a crappy ride.)

You’re liable to imagine the pilots in a sweaty lather: the captain barking orders, hands tight on the wheel as the ship lists from one side to another. Nothing could be farther from the truth. The crew is not wrestling with the beast so much as merely riding things out. Pilots will sit back and allow the plane to buck and buffet rather than attempt to recover every lost foot or degree of heading. Even in the roughest air a jet stays pretty much on an even keel. Indeed, one of the worst things a pilot could to during severe turbulence is try to fight it. Some autopilots have a special mode for these situations. Rather than increasing the number of corrective inputs, it does the opposite, desensitizing the system.

Up front, you can imagine a conversation going like this:

Pilot 1: “Well, why don’t we slow it down. [reaches for the speed control selector and dials in the reduced Mach value]

Pilot 2: “Ah, man, this is spilling my coffee all down inside this cup holder.”

Pilot 1: “Let’s see if we can get any new reports from those planes up ahead.” [Reaches for the microphone]

Pilot 2: “Do you have any napkins over there?”

There will also be an announcement made to the passengers, and a call to let the cabin crew to make sure they too are belted in. Pilots often request that the flight attendants remain in their seats if things look menacing up ahead.

Planes themselves are engineered to take a remarkable amount of punishment, including stress limit criteria for both positive and negative G-loads. The level of turbulence required to dislodge an engine or bend a wing spar is something even the most frequent flyer — or pilot for that matter — won’t experience in a lifetime of traveling.

Now, so that I’m not accused of sugar-coating, I concede that powerful turbulence has, on numerous occasions, damaged planes or injured their occupants. With respect to the latter, these are typically people who fell or were thrown about because they weren’t belted in as requested. About 60 people, two-thirds of them flight attendants, are injured by turbulence annually in the United States. That works out to about 20 passengers. Twenty out of the 800 million or so who fly each year in this country. Repeat: twenty out of 800 million.

When pilots pass on reports to other crews, turbulence is graded from “light” to “extreme.” The worst encounters entail a postflight inspection by maintenance staff. There are definitions for each degree, but in practice the grades are awarded subjectively.

I’ve never been through an extreme, but I’ve had my share of moderates and a sprinkling of severes. One of those severes took place in July, 1992, when I was captain on a 15-passenger turboprop. It happened during, of all flights, a 25-minute run from Boston to Portland, Maine. It had been a hot day, and by early evening a forest of tightly packed cumulus towers stretched across eastern New England. The formations were short — about 8,000 feet at the tops — and extremely nice to look at. As the sun fell, it became one of the most picturesque skyscapes I’ve ever seen — buildups in every direction forming a horizon-wide garden of pink coral columns. They were beautiful and deceptively violent — little volcanoes spewing out invisible updrafts. The pummeling came on with a vengeance until it felt like being stuck in an upside-down avalanche. Even with my shoulder harness pulled snug, I remember holding up one hand to brace myself, afraid my head might hit the ceiling.

Anecdotal evidence suggests that turbulence is becoming more prevalent as a byproduct of climate change. Turbulence is a symptom of the weather from which it spawns, and it stands to reason that as global warming intensifies certain patterns, experiences like the one I had over Maine will become more common.

Thanks to the vagaries of turbulence, I am known to provide annoying, noncommittal answers when asked how best to avoid it. “Is it better to fly at night then during the day?” Sometimes. “Should I avoid routes that traverse the Rockies or the Alps?” Hard to say. “Are small planes more susceptible than larger ones?” It depends. “They’re calling for gusty winds tomorrow, will it be rough?” Probably, but who knows. “Where should I sit, in the front of the plane or in the back?”

Ah, now that one I can work with. While it doesn’t make a whole lot of difference, the smoothest place to sit is over the wings, closest to the plane’s centers of lift and gravity. The roughest spot is usually the far aft.

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If you can picture the cleaved roil of water that trails behind a boat or ship, you’ve got the right idea.  With aircraft, however, wake effect is exacerbated by a pair of vortices that spin from the wingtips.  At the wings’ outermost extremities, the higher pressure air beneath is drawn toward the lower pressure air on top, resulting in a circular flow that trails behind the aircraft like a pronged pair of sideways tornadoes.

The vortices are most pronounced when a plane is heavy and slow — that is, when the wing is working hardest to produce lift.  Thus, prime time for an encounter is during approach or departure.  As the vortices rotate — at speeds that can top 300 feet per second — they begin to diverge and sink.  If you live near an airport, stake out a spot close to a runway and listen carefully as the planes pass overhead; you can often hear the vortices’ whip-like percussions as they drift toward the ground.

As a rule, bigger planes brew up bigger, most virulent wakes, and smaller planes are more vulnerable should they run into one.  The worst offender is the Boeing 757.  A mid-sized jet, the 757 isn’t nearly the size of a 747 or 777, but thanks to a nasty aerodynamic quirk it produces an outsized wake that, according to one study, is the most powerful of any airplane.

To avoid wake upsets, air traffic controllers are required to put extra spacing between large and small planes.  For pilots one technique is to slightly alter the approach or climb gradient, remaining above any vortices as they sink.  Another trick is to use the wind.  Gusts and choppy air will break-up vortices or otherwise move them to one side.  Winglets (see Chapter 1) also are a factor. One of the ways these devices increase aerodynamic efficiency is by mitigating the severity of wingtip vortices.  Thus a winglet-equipped plane tends to produce a more docile wake than a similarly sized plane without them.

Despite all the safeguards, every pilot has, at one time or another, had a run-in with wake, be it the short bump-and-roll of a dying vortex, or a full-force wrestling match.  Such an encounter might last only a few seconds, but they can be memorable.  For me it happened in Philadelphia in 1994:

Ours was a long, lazy, straight-in approach to runway 27R from the east, our 19-seater packed to the gills.  Traffic was light, the radio mostly quiet.  At five miles out we were cleared to land.  The traffic we’d been following, a 757, had already cleared the runway and was taxiing toward the terminal.  We’d been given our extra ATC spacing buffer, and just to be safe we were keeping a tad high on the glide path.  Our checklists were complete, and everything was normal.

At around 200 feet, only seconds from touchdown, with the approach light stanchions below and the fat white stripes of the threshold just ahead, came a quick and unusual nudge — as if we’d struck a pothole.  Then, less than a second later, came the rest of it.  Almost instantaneously, our 16,000-pound aircraft was up on one wing, in a 45-degree right bank.

It was the first officer’s leg to fly, but suddenly there were four hands on the yokes, turning to the left as hard as we could.  Even with full opposite aileron — something seldom used in normal commercial flying — the ship kept rolling to the right. There we were, hanging sideways in the sky.  Everything in our power was telling the plane to go one way, and it insisted on going the other. A feeling of helplessness, of lack of control, is part and parcel of nervous flyer psychology. It’s an especially bad day when the pilots are experiencing the same uncertainty.

Then, as suddenly as it started, the madness stopped.  In less than five seconds, before either of us could utter so much as an expletive, the plane came to its senses and rolled level.

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As air flows around a wing at high velocity, its temperature and pressure change. If humidity levels are high enough, this causes the cores of the wingtip vortices described in the previous question to condense and become visible, writhing behind the plane like gray vaporous snakes. Moisture will condense around other spots too, such as the engine attachment pylons. You’ll witness what appears to be a stream of white smoke pouring from the top of an engine during takeoff. This is water vapor caused by invisible currents around the pylon. Other times the area just above the surface of the wing will suddenly flash into a white puff of localized cloud. Again this is condensation brought on by the right combo of humidity, temperature, and pressure.

Not only can you sometimes see wingtip vortices, but even cooler, you can often hear them from the ground:

You need to be very close to a runway — preferably within a half-mile of the end. The strongest vortices are produced on takeoff, but ideally you want to be on the landing side, as the plane will be nearer (i.e. lower) at an equivalent position from the threshold. A calm day is ideal, as gusts will dissipate a vortex before it reaches the ground. About 30 seconds after the jet passes overhead you’ll begin to hear a whooshing, crackling and thundering. It’s a menacing sound unlike anything you’ve heard before. See — or hear — for yourself in this footage captured on my iPhone.

It was taken at the Belle Isle Marsh Reservation, a popular birdwatching spot about a half-mile north of runway 22R at Boston’s Logan International Airport. The plane is a straight-wing (no winglet) 757. Excuse the atrocious video quality, but the sound is acceptable and that’s the important thing. You begin to hear the vortices at time 0:45, and they continue pretty much to the end. Note the incredible gunshot-like noises at 0:58.

Play it loud!

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One of those buzzwords that scare the crap out of people, windshear is a sudden change in the direction and/or velocity of the wind.  Although garden variety shears are extremely common and almost never dangerous, encountering a powerful shear during takeoff or landing, when airplanes operate very close to their minimum allowable speeds, can be serious.  Remember that a plane’s airspeed takes into account any existing headwind.  If that velocity suddenly disappears or shifts to another direction, those knots are lost.  It can happen vertically, horizontally, or both, as in the case of a microburst preceding a thunderstorm.  Microbursts are intense, localized, downward-flowing columns of air spawned by storm fronts.  As the air mass descends, it disperses outward in different directions.

Windshear and microbursts got a lot of press in the 1970s and 1980s when they were still misunderstood phenomena.  The crash of Eastern flight 66 in New York in 1975 is considered the watershed accident after which experts began to study them more carefully.  Since then, conditions that propagate dangerous shear have become relatively easy to forecast and avoid.  Major airports are now equipped with detection systems, as are planes.  Pilots are trained in escape maneuvers, and can recognize which weather conditions might be hazardous for takeoff or landing.  The last headline crash attributed to windshear was in Dallas in 1985.

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In their attempts to put people at ease, pilots can oversimplify things to the point where people begin giggling instead of nodding.  What he was talking about was a “compressor stall,” a phenomenon where airflow through the engine is temporarily disrupted.  The compressors of a jet or turboprop consist of a series of rotating airfoils, and if air stops flowing smoothly around these airfoils, or backflows between the sequential stages, your compressor is stalling.  It can damage an engine, but chances are it won’t.

Miscellaneous engine peculiarities, compressor stalls included, can sometimes put on a show.  The visuals and aurals that accompany them aren’t always comforting.  Aside from a bang, you might see a long tongue of flame shooting from the exhaust.  Tough as it might be to accept, the engine is neither exploding nor on fire.  This is the nature of a jet.  Any time the engine is running, fuel is combusting, and certain anomalies will unleash this combustion rather boldly.

The stalling compressors of an Alaska Airlines 737 once made the news when, by chance, a burst of flame was captured by somebody’s camcorder on the ground.  The video was alarming, but the phenomenon effectively harmless.  When this sort of thing happens at the gate or during taxi, passengers have been known to initiate their own evacuations.  One such panic took place aboard a Delta 757 in Tampa, Florida.  A stampede of frightened passengers made for the exits, refusing to heed flight attendant commands.  Two people were seriously hurt.

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Failure of all engines is, to be clear, a full-blown emergency. Yet there’s no more a prospect of instant calamity than taking your foot off the accelerator when coasting downhill in a car. The car keeps going and a plane will too. In fact the power-off performance of a large jet is better than that of a light Piper or Cessna. It needs to glide at a considerably higher speed, but the ratio of distance covered to altitude lost — close to a 20:1 ratio — is almost double. From 30,000 feet you could plan on a hundred miles worth of glide, give or take. While it may surprise you, it’s not the least bit uncommon for jets to descend at what a pilot calls “flight idle,” i.e. with the engines run back to a zero-thrust condition. They’re still operating and powering essential systems, but providing no push — not a lot different from switching them off entirely. You’ve been gliding many times without knowing it.

Total engine loss is about as probable as a flight attendant volunteering to give you a shoe-shine, though it has happened a dozen or so times since the 1970s. That might seem like a long list, but in the grand scheme of things such incidents are exceptionally rare, and in most of those incidents there were no fatalities.The culprits have included everything from volcanic ash encounters to hail ingestion to multiple impacts with birds, as seen in the 2009 Hudson River splashdown (see bird strikes later in this chapter).

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Without pressurization, there would not be enough oxygen to breathe.  We could stray into definitions of things like “partial pressure,” but we’ll keep it easy: as you go higher the air thins, which is to say the amount of oxygen decreases.  Pressurizing the cabin effectively squeezes the air back together, re-creating the dense, oxygen-rich conditions on the ground.  Or close to it, as during cruise the atmosphere in a jet is actually kept a bit higher than sea level, usually on the order of 5,000-8,000 feet.  In other words you’re breathing as you would in Denver or Mexico City — minus the pollution.  (Pressurizing all the way to sea level is unnecessary and would put undue stress on the airframe.)  Pressurization is maintained via air from the compressors in the engines and regulated through valves in the fuselage.  That’s all there is to it.  Something about the word “pressurization” makes people envision the upper altitudes as a kind of barometric hell.  I’ve been asked, “If the plane wasn’t pressurized, would my eyes pop out?”  Cruising in an airplane is not the same as dropping to the Marianas Trench in a deep-sea diving bell.

If a malfunction arises, tie on your mask and breathe normally, just as the flight attendants tell you.  If it needs to, the crew will descend to a height where the masks aren’t required.  (Depressurization “escape routes” are published for flights over high or mountainous terrain.)  This will take only a few minutes, and there’s more than enough oxygen for everybody.  The presence of those masks, I know, is a source of angst for many.  Should they spring from the ceiling, try to resist shrieking or falling into cardiac arrest.  Even in a worst-case decompression, which it won’t be, you’ve got time to get the plastic on.  There have been very few instances of airline passengers dying from a pressurization problem.

Directly, anyway.  Cruising along, there’s little inherent danger in terms of pressure per se, either inside or outside.  The inherent danger is the difference between the two.  A pressurized cabin is, if you’ll let me make the kind of alarmingly suggestive analogy I hate making, like a toy balloon.  Losing pressurization is not, by itself, deadly, and in some cases a plane could lose every last psi. and it would hardly be noticed.  What’s potentially deadly is losing it explosively, with resultant forces damaging or destroying the plane.  A bomb might cause this, as could ruptures of the fuselage, bulkheads, windows or doors.  Awful to consider, yes, but such misfortunes have been pleasantly few.

One reason an airplane’s cabin windows are small — and round — is to better withstand and disperse the forces of pressurization.  (Their size and shape also best assimilate the bending and flexing of a fuselage in flight.)  I know what you’re imagining: a burst window and people being sucked through the hole, head first.  Has this ever happened?  To find out we’d have to dust off some old archives or give Google an electronic heart attack, which basically tells you not to bother worrying.

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The short answer is no.  No commercial aircraft is unsafe, or anything remotely close to it.  The long answer is more nuanced.  Whether or not regional aircraft are, on some level, less safe than mainline jets is open to debate.  It’s a debate of statistical minutia, and there is no practical reason why anybody should outright avoid smaller planes, but still it’s a debate worth having.

Size, strictly speaking, isn’t the issue.  The metric correlating bigger with safer is a tough one to uproot, and for the most part it’s wrong.  I can’t speak to claustrophobia or absence of legroom, but there is almost nothing about an airplane’s size that correlates one way or the other to the likelihood of it crashing.  A modern turboprop or regional jet (RJ) can cost tens of millions of dollars, and if you haven’t noticed that money isn’t going into galleys and sleeper seats; it’s going toward the same high-tech avionics and cockpit advancements you’ll find in a Boeing or Airbus.  These planes might be small, but quaint they are not.  And so you know, pilots bristle at the term “puddle-jumper” the way an environmental scientist bristles at “tree-hugger.”

Of course, a plane is only as safe as the crew flying it, and there has been a good deal of controversy surrounding the training and experience levels of regional pilots.  With the entire airline industry in turmoil, and with wages and working conditions at regional carriers notoriously substandard, it has become increasingly difficult for these companies to recruit and retain the best pilots.  New-hires have been brought on board with very low flight time totals and thrust into a high-stress, high-workload environment.  More on this later.

Love them or hate them, smaller planes are here to say.  The regional airline sector has grown tremendously over the last twenty years, and now accounts for a full 50 percent of all domestic departures.  There are literally dozens of different “Express” and “Connection” affiliates hitched up with the majors.  For the most part they operate independently from their major airline “parents,” sharing little more than a flight number and paintjob.  They are subcontractors, with entirely separate management structures, employees, training departments, etc.

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If you’re impressed by big numbers, you’ll be grabbing for the highlighter when you find out a 747 tops off its tanks at just over 45,000 total gallons.  It takes about 11,000 to fill a 757, or 6,000 for a 737 or A320.  A 50-seater with propellers might hold less than 1,000 gallons.  Paltry in comparison, but still enough to drive your car from Washington to California six times.  Fuel is stored in the wings, in the center fuselage, and even in the tail or horizontal stabilizers.  The cargo jet I used to fly had eight separate tanks, and much of my job was moving their contents around to keep them balanced.

Flights rarely depart with full tanks, as lugging around excess tonnage is expensive and impractical.  Fuel loads are determined in advance by an airline’s dispatchers and flight planners, in strict accordance to a long list of regulations.  The regs are intricate and can vary country to country (a plane is beholden to its nation of registry, plus any local requirements if they’re more stringent), but the U.S. domestic rule is a good indicator of how conservatively things work:  There must always be enough to carry a plane to its intended destination, then to its designated alternate airport(s), and then for at least another 45 minutes.  The resulting minimum is non-negotiable.  Sometimes two or more alternates have to be filed in a flight plan (another batch of rules), upping the total accordingly.  If long delays are expected, even more might be added.  The preflight paperwork includes a detailed breakdown of anticipated burn.  En route, the remaining total is cross-checked against the predicted total as waypoints are passed.  Although dispatchers and planners devise the figures, pilots have the final say and can always request extra.  Carrying surplus fuel costs money, but not nearly as much as the hassles of diverting.

Or crashing.  Considering all of the above, the idea of running the tanks dry would seem far fetched.  Yet fuel depletion accidents have occurred.  To explain how, exactly, would entail pages of boring (for both of us) analysis, which I choose to withhold, but suffice to say it’s a little more complicated than a half-asleep copilot tapping a gauge and going “Holy shit we’re almost out of gas.”  If you’re a techie type, the Web can furnish in-depth explanations.

A couple of keywords to start with are Air Canada and Air Transat.  A 767 belonging to the former, and an Airbus A330 of the latter, a Canadian charter airline, had starring roles in the most recent out-of-gas embarrassments.  Maybe it’s a Canada thing.  Air Transat’s incident stemmed from mechanical trouble, while Air Canada’s was principally human error, including a litres-to-gallons foul-up.  In both cases crews managed to glide to a landing with no casualties.  A bizarre chain of mistakes found a United DC-8 gliding into trees near Portland, Oregon, in 1978, and an Avianca 707 crashed on Long Island in 1990 after a series of arrival delays at JFK.  Going back even earlier, a DC-9 once ditched near St. Croix, and in 1963 an Aeroflot jet glided into the Neva near Leningrad. Commercial jet travel in the ’60s Soviet Union wasn’t exactly state-of-the-art, so it’s tempting to ignore that one entirely.  In any case the plane remained floating and everybody escaped.  A half-dozen blemishes over five decades?  Compute those odds next time you’re doing the rounds in a holding pattern and it’ll help you relax.

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People will sometimes complain to authorities about what they take to be streams of jet fuel trailing behind airplanes low to the ground.  What they’re actually looking at are trails of water vapor — the condensed cores of wingtip vortices (see wakes, this chapter).  You will sooner see sacks of hundred-dollar bills being heaved overboard than fuel being spit away for no good reason. 

And then, yes, it’s to lighten the load. With larger planes, maximum weight for takeoff is often greater than the one for landing.  True for a few reasons, the obvious being that touching down puts higher stresses on an airframe than taking off.  Normally the suitable tonnage will be burned away enroute.  Now, let’s say something happens soon after takeoff and a plane must return to the airport.  Rather than tossing passengers or cargo overboard, it will jettison fuel through plumbing in its wings.  I once had to dispose of more than 100,000 pounds this way over northern Maine, a procedure that took many minutes and afforded me a lavish night’s stay at the Bangor airport Hilton.  Unless the trouble is urgent, dumping takes place at high enough altitudes where the kerosene mists and dissipates long before reaching the ground — and no, engine exhaust will not set the discharge aflame.

Know that a plane dumping fuel and executing a precautionary return is, nine times out of ten, not in the throes of an actual emergency. The term “emergency landing” is used generically by passengers and the press, but crews must formally declare an emergency to air traffic control, and will do so only in situations when time is critical, there’s the possibility of damage or injury, or if aircraft status is uncertain. The great majority of precautionary landings are just that, precautionary. Even most formal emergencies are pretty benign. And don’t let the fire engines scare you; report a missing soda from the galley and the fire engines will likely be summoned.

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Planes are hit by lightning more frequently than you might expect — an individual jetliner will struck about once every two years, on average — and are designed accordingly.  The energy does not travel through the cabin electrocuting the passengers; it is discharged overboard through the plane’s aluminum skin, which is an excellent electrical conductor, nine times in ten leaving little or no evidence.

Once in a while there’s damage or upset, most commonly to the plane’s electrical systems.  In 1963 lightning caused a wing explosion aboard a Pan Am 707 over Maryland.  Afterwards, the FAA decided to enforce several protective measures, including fuel tank modifications and the installation of discharge wicks aboard all aircraft.  That was almost fifty years ago and I know of no other lightning disasters to date.

You can’t have lightning without thunder, and using their radar units, along with help from ATC, pilots avoid thunderheads the way ships avoid icebergs.  Weather, though, can be sneaky, and smaller cumulonimbus tough to detect.  In 1993 I was captaining a 37-seater when lightning from a small embedded cell got us on the nose.  What we felt and heard was little more than a dull flash and a thud.  No warning lights flashed, no generators tripped off line.  Our conversation went:

“What was that?  Lightning”"
“[Shrug].”
“Lightning?”
“I don’t know.”

Mechanics would later find a black smudge not far from the cockpit windshield.

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Although bird strikes are very common, the damage tends to be minor or nonexistent — unless you’re talking from the bird’s point of view.  As you’d expect aircraft components are built to tolerate such impacts, and on the Web you can see videos of bird carcasses being fired from a sort of chicken-cannon to test the resistance of windshields, intakes, and so forth.  I’ve personally experienced several strikes, and the result was at worst a minor dent or crease.  Occasionally, however, a strike can be serious.  This is especially true when engines are involved, as we saw in 2009 when US Airways flight 1549 glided into the Hudson River after colliding with a flock of Canada Geese.  Modern turbofans are resilient, but they don’t take kindly to the ingestion of foreign objects, particularly those slamming into their rotating blades at high rates of speed.  Birds don’t “clog” an engine but can bend or fracture the internal blades, causing power loss.

The heavier the bird, the greater the potential for harm.  Flying at 250 knots — in the U.S., that’s the maximum allowable speed below 10,000 feet, where most birds are found — hitting an average-sized goose will subject a plane to an impact force of over 50,000 pounds.  Even small birds pose a threat if struck en masse.  In 1960 an Eastern Air Lines turboprop went down in Boston after an encounter with a flock of starlings, killing 62 people.  Three of its four engines had failed or were damaged.

Your next question, then, is why aren’t engines built with protective screens in front?  Well, in addition to partially blocking the inflow of air, the screen would need to be quite large (cone-shaped, presumably) and incredibly strong.  Should it fail, now you’ve got a bird and pieces of metal going into the motor rather than just a bird.  The incidents above notwithstanding, the vast improbability of losing multiple engines to birds renders such a contraption impractical.

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During flight, ice can accumulate in different places — on wing edges, engine inlets, etc.  Mostly it sticks to the thinner, lower profile areas, and not to larger expanses or the fuselage (a function of aerodynamics; let’s not go there).  This occurs during visible precipitation, or when suspended moisture sublimates directly.  The monster here isn’t the weight of the frozen material, but the way it changes the contouring of the airfoils.  Even a quarter-inch ridge can wreak havoc — highly important during takeoff and landing when speed is slow and lift margins are thin.

On smaller planes, pneumatically inflated boots will break ice from the leading edges of the wings and stabilizers.  On larger ones, air bled from the engine compressors heats wings and inlets.  Windshields, together with various probes and sensors are kept warm electrically.  Deicing systems use redundant sources and are separated into independently functioning zones to keep a failure from affecting the entire plane.

Planes are scouted for ice before departing, and an airline’s preflight deicing checklist can take up several pages of a pilot’s manual.  The delicious looking spray (apricot-strawberry) used for ground deicing is a heated combination of propylene glycol alcohol and water.  It removes existing material and prevents the buildup of more.  Different mixtures, varying in temperature and viscosity, are applied for different conditions.  How long a plane is good for follows something called “holdover time.”

Deicing fluid is collected and recycled, but at $5 per gallon airlines loathe snowstorms almost as much as strikes, wars, and recessions.  When handling and storage costs are considered, relieving a single jet of unwanted winter white can cost tens of thousands of dollars.  Making a messy situation worse, certain additives to the glycol — itself harmless — are potentially toxic.  What does our de-icing future look like?  It looks like a hangar — like the pioneering facility built at Newark by Continental, where planes are steered through enclosures that melt away ice using powerful infrared lamps instead of fluid.

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Several years back I was on a train going from Malaysia into Thailand when I stepped into the restroom and lifted the toilet seat.  I was presented with a mesmerizing view of gravel, dirt, and railroad ties, all passing rapidly beneath me.  Those who travel will encounter this now and again, and maybe it’s people like us who get these nutty myths off and running.  The answer is no.  There is no way to intentionally jettison the contents of the lavatories during flight.

A man in Santa Cruz, California, won a $3,000 suit against an airline when two pieces of “blue ice” came crashing like neon meteorites through the skylight of his boat.  This was not the result of a couple of pilots prankishly reliving their days flying Air Force bombers.  What happened was a leak, extending from the toilet’s exterior nozzle fitting, caused runoff to freeze, build, and then drop like an icicle.  If you think that’s bad, a 727 once suffered an engine separation after ingesting a frozen chunk of its own leaked toilet waste, inspiring the line, “when the shit hits the turbofan.”

Your contributions to the airplane’s plumbing, provided their composition isn’t at violent odds with the blue fluid, are vacuumed into a tank and disposed of later.  On busy multi-leg days, “We need lav service,” is something a pilot — especially a regional pilot — says almost as much as “roger” when talking over the company frequency before landing.  A truck then pulls up and drains out the contents.  (The truck driver’s job is almost as lousy a job as the first officer’s, but it pays better.)  Afterwards the man wheels around to the back of the airport and furtively offloads the waste in a ditch behind a parking lot.

In truth I don’t know where it goes after that.  Time to start a new urban legend.

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Airplanes can depart with various inoperative components — usually nonessential equipment carried in duplicate or triplicate — in accordance with guidelines laid out in two thick manuals called the MEL (Minimum Equipment List) and CDL (Configuration Deviation List).  Any component in these books is “deferrable,” as we put it, so long as any outlined stipulations are met.  These stipulations can be quite restrictive, depending what’s broken.  One of the first things a crew does after signing in for a trip is scan the paperwork for deferrals, making note of any pertinent restrictions.  A malfunctioning anti-skid system for example, might require a longer runway for takeoff and landing.  An inoperative APU (auxiliary power unit), could mean a lower than normal cruise altitude, or it might prohibit flights across the ocean.

That’s inviting some cynicism, but honestly the books are not contrived to allow airlines easy hand at flying around with defective equipment.  Many things, as you’d hope, are not deferrable at all, and any malfunctioning item must be repaired in a set number of days or flight hours.  All deferrals have to be documented and coordinated between the crew and maintenance personnel, a process that entails a series of logbook notations and signatures.

Equipped with the latest diagnostic tools, some airplanes automatically transmit fault alerts while in the air, giving maintenance personnel advance notice of malfunctions.

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The walk-around inspection, while useful, is essentially a superficial perusal, not a whole lot different from checking your oil, tires, and wipers before a road trip.  The more technical preflight routine takes place out of view, in the cockpit.  While you’re bottlenecked at the mouth of the jet bridge, the various cockpit instruments and systems are being tested.  Mechanics and pilots each have their procedures to run through prior to flight.  And after too.  Watch a plane dock and you might spot mechanics fanning out beneath it while another heads up front to consult with the crew and review the logbook.

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Commercial aircraft are built to last more or less indefinitely, which is one of the reasons they’re so expensive.  Thus it’s not the least bit uncommon for a jet to remain in passenger service for 20 or 30 years.  If your concerns rest with cabin accoutrements or particle emissions from older-generation turbofans, go ahead and gripe, but statistically, with respect to accidents, there is little correlation between service time and safety.

The older a plane gets, the more and better care it needs in the hangar; inspection and overhaul criteria grow increasingly strict.  And age, strictly speaking, is only part of the equation.  It depends not only on the number of birthdays, but also the number of flight hours, as well as the number of takeoffs and landings — i.e. “cycles” — accrued over the years.  The FAA recently implemented tough new inspection and record-keeping procedures for certain geriatric aircraft, covering things like corrosion, metal fatigue, and wiring issues.  Up front, older cockpits are often rejuvenated with modern navigation systems and safety features.

Surprisingly — or maybe not — US airline fleets rank among the oldest.  Delta Air Lines still cares for several DC-9s that date from the Age of Aquarius, acquired during its merger with Northwest.  While Asian and European airlines tend to fly the newest planes, some of the most cutting-edge fleets pop up in surprising places — Brazil, Nigeria, Turkey.  Youthfulness might be fostered by government subsidies (or outright ownership) in some nations, while in Europe tough anti-noise restrictions essentially mandate newer planes.  Frequently too it’s the owner’s progressiveness or pride.  Lufthansa, Scandinavian (SAS), and Singapore are a few lauded companies that make a point of quick turnover.  In America, exponentially larger fleets and enormous, model-specific inventories (maintenance supplies, ground equipment, etc.), make short-term renewals more burdensome.

“Retirement” is an ambiguous term with airplanes. Planes are sold, traded, or mothballed not because they’ve grown old and are falling apart, but because they’ve become uneconomical to operate.  This may or may not be related to their date of construction.  Take the case of Delta and American, who chose to “retire” their MD-11s yet plan to hold on to substantially older MD-80s and 767s for many years to come.  Operators will speak of a particular model’s “mission,” one in which very fragile balances — tiny, shifting percentages of expenses and revenues — are the difference between red and black.  Poor performance means quick exit to the sales block.  To another carrier with different costs, routes, and needs, that same aircraft might be profitable.

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