Cockpit Confidential (25 page)

The Boeing 787 has the healthiest air of any commercial plane, thanks to filters with an efficiency of 99.97 percent. Humidity too is substantially higher. The plane's all-composite structure is less susceptible to condensation, and a unique circulation system pumps dry air through the lining between the cabin walls and exterior skin.

None of this is disputing that people don't occasionally become unwell from flying. While the air is clean, the dryness is bad for sinuses and can break down mucous barriers, making it easier to catch what bugs might be present. Usually, though, it's not what passengers are breathing that makes them sick, but what they are
touching
—lavatory door handles, contaminated trays and armrests, etc. A little hand sanitizer is probably a better safeguard than the masks I occasionally see passengers wearing.

Neither am I disputing that the airplane isn't a potentially exquisite vector for the spread of certain diseases. The benefits of high-speed, long-range air travel are obvious—and so are its dangers. Once after arriving on a flight from Africa, I noticed a lone mosquito in the cockpit. How easy it would be, I thought, for that tiny stowaway to escape into the terminal and bite somebody. Imagine an unsuspecting airport worker or passenger who has never before left the country, and suddenly he's in the throes of some exotic tropical malady. Actually, it's been happening for years. Cases of “airport malaria” have been documented in Europe, resulting in several deaths after faulty or delayed diagnosis. It's just a matter of time before this happens in America, if it hasn't already. It is instructive, fascinating, and frankly a little scary to see just how efficiently global air travel can spread pathogens from continent to continent.

This is one of flying's most enduring fallacies, similar to the one just covered about reducing airflow to save fuel. Not only is it patently false, but it also would have a rather undesirable effect on a plane's occupants: shortage of oxygen brings on a condition known as hypoxia. Although hypoxia can, at first, make a person feel giddy and relaxed, it also induces confusion, nausea, and migraine-strength headaches. A pilot would have to be pretty sadistic to provoke that kind of mass agony. I remember the multiday hypoxia headache I endured some years ago in Cuzco, Peru—an experience I wouldn't wish on my worst enemy, let alone a planeload of customers.

Oxygen levels are determined by pressurization, and almost never are the pressurization controls tinkered with during cruise unless there's a malfunction. Crews set up the system before departure; the rest happens automatically. While en route, the cabin is held at the equivalent of somewhere between 5,000 and 8,000 feet above sea level, depending on aircraft type and cruising altitude (
see pressurization
).

And pilots are breathing the same air as everybody else. An aircraft fuselage does not contain separate compartments with different pressure settings. The entire vessel is pressurized equally from front to back. This includes the cabin, cockpit, and lower-deck cargo holds.

At the gate, planes are cooled or heated one of two ways. The first is through an external air supply plumbed into the cabin through a valve in the lower fuselage. This is the heavy yellow hose that you sometimes see running between the airplane and the jet bridge. The second way is via the plane's auxiliary power unit (
see APU
). This small turbine engine supplies air and electricity when the main engines aren't running. Although the APU tends to be more effective, the general rule is to rely on external air, if available, because it's cheaper. Pretty much all carriers, however, have a policy that allows crews to start the APU if conditions become uncomfortable. Despite the emphasis on saving fuel, no captain would be penalized for using the APU to cool down an overheated cabin (or warming up a cold one).

So why do passengers find themselves sweating in a crowded cabin? The culprit might be an inoperative APU or an insufficient or malfunctioning ground source. If things get bad enough, speak up. It is well within your rights to complain to a flight attendant. They, in turn, can request we turn on the APU or check out the ground connection. Although we have cabin temperature readouts in the cockpit, we often rely on the cabin crew to let us know when temps are becoming extreme.

One small but effective way of keeping a plane cooler is to close the window shades between flights. Flight attendants will sometimes ask passengers to lower their shades as they disembark.

That's called a packs-off takeoff. The air-conditioning packs run on bleed air from the engines and, in the process, rob some of their power. Therefore, certain heavyweight takeoffs require that one or more packs not be used until safely airborne. It depends on weight, runway length, and temperature. The predeparture performance data—a printout of all relevant speeds, power, and flap settings—tells the crew if this is necessary. The packs will be switched off just prior to the roll, then turned on again during the early portion of climb—usually around the time of the first scheduled power reduction, at a thousand feet or so (
see climbout cutback
).

It seems that a week can't go by without hearing or reading a story about a passenger who went cuckoo and tried to yank open an emergency exit, only to be tackled and restrained by those around him, who thought they were on the verge of being ejected into the troposphere. While the news never fails to report these events, it seldom mentions the most important fact: You cannot—I repeat,
cannot
—open the doors or emergency hatches of an airplane in flight. You can't open them for the simple reason that cabin pressure won't allow it. Think of an aircraft door as a drain plug, fixed in place by the interior pressure. Almost all aircraft exits open inward. Some retract upward into the ceiling; others swing outward; but they open inward
first
, and not even the most musclebound human will overcome the force holding them shut. At a typical cruising altitude, up to eight pounds of pressure are pushing against every square inch of interior fuselage. That's over 1,100 pounds against each square foot of door. Even at low altitudes, where cabin pressure levels are much less, a meager 2 psi differential is still more than anyone can displace—even after six cups of coffee and the aggravation that comes with sitting behind a shrieking baby. The doors are further held secure by a series of electrical and/or mechanical latches.

So, while I wouldn't recommend it, and unless you enjoy being pummeled and placed in a choke-hold by panicked passengers, you could, conceivably, sit there all day tugging on a handle to your heart's content. The door is not going to open (though you might get a red light flashing in the cockpit, causing me to spill my Coke Zero). You would need a hydraulic jack, and TSA doesn't allow those.

On the nineteen-passenger turboprop I used to fly, the main cabin door had an inflatable seal around its inner sill. During flight the seal would inflate, helping to lock in cabin pressure while blocking out the racket from the engines. Every now and then the seal would suffer a leak or puncture and begin to deflate, sometimes rapidly. The resultant loss of pressurization was easily addressed and ultimately harmless, but the sudden noise—a great, hundred-decibel sucking sound together with the throb of two 1,100-horsepower engines only a few feet away—would startle the hell out of everybody on the plane, including me.

On the ground, the situation changes—as one would hope, with the possibility of an evacuation in mind. During taxi, you
will
get the door to open. You will also activate the door's emergency escape slide. As an aircraft approaches the gate, you will sometimes hear the cabin crew calling out “doors to manual” or “disarm doors.” This has to do with overriding the automatic deployment function of the slides. Those slides can unfurl with enough force to kill a person, and you don't want them billowing onto the jet bridge or into a catering truck.

Cabin windows need to be small—and round—to better withstand and disperse the forces of pressurization. This size and shape also helps assimilate the bending and flexing of a fuselage that results from aerodynamic forces and temperature changes. For these same reasons, it's beneficial to place the windows along the flattest portion of a fuselage, which is why they're sometimes aligned in a less-thanoptimum viewing position.

The Caravelle, a French-built jetliner of the 1960s, had triangular cabin windows—rounded at the corners, but distinctly three-sided. The Douglas DC-8 was another exception. Not only were its windows squared-off, they were uniquely oversized, with almost twice the glass of today's Boeings or Airbuses. (And one of my favorite tidbits: Look closely at an Air India jet and you'll see that each cabin window is meticulously outlined with a little Taj Mahalian motif that makes each jet reminiscent of a Rajasthani palace.)

But what about cockpit windows? Aren't they much larger, and square-ish? That's true, but they also are made of multilayered glass thicker than a bank teller's and bolstered by high-strength frames—unbelievably resilient against pressure differentials, hail, and oncoming birds. I once saw a video of maintenance workers attempting—and failing—to shatter a discarded cockpit windscreen with a sledgehammer. Swapping out a single pane of cockpit glass can run into the hundreds of thousands of dollars.

Despite the many Hollywood depictions to the contrary, I am not aware of a passenger ever being sucked through a ruptured cabin window. I can, however, vouch for the story of a British Airways captain who was partially ejected through a blown-out cockpit pane. He survived with minor injuries.

Special thanks to Gregory Dicum's enjoyable book
Window Seat
for help with this one. The phenomenon described is called a “glory,” or a “pilot halo.” They're common under the right conditions of cloud cover and sunlight angle. The aura of colored bands is caused by sunlight diffracted and reflected by water droplets inside the cloud. Sometimes you do see the airplane's shadow directly in the halo's center; other times only the rings are visible.

At 35,000 feet the outside air temperature is about 60 degrees below zero and there is not enough oxygen to breathe. That's worse even than economy, and transporting animals in these conditions would not please most pet owners. So, yes, the underfloor holds are always pressurized and heated. Usually there is one zone designated specifically for pets. This tends to be the zone in which temperature is most easily regulated. Maintaining a safe temperature is straightforward during flight—there's not a lot to it, and controls are set the same way, pets or no pets—but it can be tricky on the ground during hot weather. For this reason, some airlines embargo pets for the summer months. The flight crew is always told when live animals are below. Passengers are known to send handwritten notes to the cockpit asking that we take special care. This isn't really necessary, and there's only so much we can do, but go ahead if it makes you more comfortable.

Few rules are more confounding to airline passengers than those regarding the use of cell phones and portable electronic devices. Are these gadgets really hazardous to flight? People want a simple, fits-all answer. Unfortunately, there isn't one. It depends on the gadget and how and when that gadget is used.

Let's take laptops first. In theory, an old or poorly shielded computer
can
emit harmful energy. However, the main reasons laptops need to be put away for takeoff and landing is to prevent them from becoming high-speed projectiles during a sudden deceleration or impact and to help keep the passageways clear if there's an evacuation. Your computer is a piece of luggage, and luggage needs to be stowed so it doesn't kill somebody or get in the way. This is why, after landing, flight attendants make an announcement permitting the use of phones but not computers. There's still the possibility, remote as it might be, of an emergency evacuation, and you don't want people tripping over their MacBooks as they make for the exits.

Next, we have tablet devices like Kindles, Nooks, and iPads. From an interference perspective, it's tough to take a prohibition seriously now that many pilots are using tablets in the cockpit. The projectile argument would appear similarly specious: nobody wants an iPad whizzing into his or her forehead at 180 miles per hour, but hardback books are just as heavy, if not heavier. If we're going to ban tablets during takeoffs and landings, why should books be exempt? The FAA is mulling this over as we speak. It's possible that by the time you're reading this, the tablet rules will have been relaxed.

And finally the big one: cellular phones. Can cellular communications
really
disrupt cockpit equipment? The answer is potentially yes, but in all likelihood no, and airlines and the FAA are merely erring on the better-safe-than-sorry side. You want something meatier, I know, but that's about as accurate an answer as exists.