The Flying Book

by David Blatner

  After tower control gives the pilots permission to take off, and once the aircraft is in the sky, tower control hands the pilots off to Terminal Radar Approach Control (TRACON), which handles all air traffic within about thirty miles of the airport. The TRACON controllers supervise all arrivals and departures for one or more airports. For example, the TRACON in Oakland, California, manages traffic into and out of three major airports in close proximity—in San Francisco, San Jose, and Oakland—plus a handful of smaller airports, like those in Hayward and Palo Alto. There are about 185 TRACONs spread out across the United States, each based at or near an airport.

  However, the TRACON controllers only oversee air traffic up to an altitude of 17,000 feet, so the pilots are only in communication with TRACON for a matter of minutes before they’re handed off to an Air Route Traffic Control Center (ARTCC, or just Center), which handles all high-altitude flights en route to their destinations.

  The windows in an airport control tower must always be tilted out at exactly fifteen degrees from the vertical to minimize reflections both inside and outside the control cab.

  In a small country, there may be only one Center controlling all the traffic. In the United States, however, there are twenty-one Centers: in Albuquerque, Anchorage, Atlanta, Boston, Chicago, Cleveland, Denver, Fort Worth, Houston, Indianapolis, Jacksonville, Kansas City, Los Angeles, Memphis, Miami, Minneapolis, New York, Oakland, Salt Lake City, Seattle, and Washington, D.C. Because a single ARTCC may oversee several states and hundreds of thousands of square miles, each Center is broken down into sectors, which are typically between 50 and 200 miles wide. Each air traffic controller at a Center (which is usually a windowless building nowhere even near an airport) is assigned a sector to manage, and as an aircraft travels from one sector to another, the pilots are handed off from one sector controller to the next, and (on long flights) from one Center to the next.

  The system is much the same on international flights. When flying from New York to London, for example, the pilots are passed from New York to Gander Ocean Control (in Newfoundland, Canada) to Shanwick Ocean Control (which is actually located in two cities: Shannon, Ireland, and Prestwick, Scotland).

  Finally, when the aircraft is approaching its destination, the sector controller leads the pilots down to a lower altitude and then hands them off to the destination airport’s TRACON arrival controller, who lines up each incoming aircraft properly before handing the pilots off to a tower controller. Once on the ground, the pilots are handed off to the local ground controller, who directs them through the taxiways to the proper gate.

  Keeping the Distance

  About 50,000 airplanes fly over the United States each day, from private single-engine aircraft out for joyrides, to “puddle jumpers” flying commuters over short distances, to jumbo jets on intercontinental flights. Air traffic controllers must constantly be aware of where each airplane is, as well as where it is headed, so that no two airplanes get too close to each other. They obtain this information primarily through the use of radar, sophisticated computer software, and information received from each airplane’s transponder (a device that responds to radar signals by transmitting a code back that identifies the particular aircraft, its position, and its current altitude).

  Air traffic control laws are complex, but they can be boiled down to a few rules.

  Radar can be compared to a flashlight shining into the night sky: When the light hits something, like a bird flying by, it bounces back into your eyes so you can see it. Radar uses light waves that the eye can’t see; if the radar beam hits an object, it bounces back (echoes) where it can be picked up by a sensor. Light waves travel so fast that the whole process happens in less than one hundredth of a second.

  Takeoffs and landings generally need to be separated by at least two minutes, though this interval is extended after the takeoff of “heavy” aircraft, such as a wide-body Boeing 777, so that subsequent aircraft won’t get caught in wake turbulence.

  Near an airport, aircraft must be separated by three miles (in good weather) or five miles (in bad weather). At higher altitudes, aircraft are kept at least ten or twenty nautical miles apart (or even more, in poor weather).

  However, when flying over areas of the world that don’t have en route radar systems—such as the Atlantic and Pacific Oceans, inner Australia, and much of Africa—pilots must maintain ten or fifteen minutes’ flying time between themselves and other aircraft. At cruise speeds, that means between 80 and 140 miles apart, when they’re at the same altitude.

  Below 29,000 feet, aircraft must maintain a 1,000-foot (305 meter) vertical separation. Older altimeters (instruments that measure altitude) are less accurate at great heights, so above 29,000 feet, aircraft need 2,000 feet (.6 km) of vertical separation. Newer systems are far more accurate, and the rules are slowly changing to accommodate the higher number of airplanes in some areas.

  Above 18,000 feet, pilots and ATC discuss altitude in terms of flight level. Flight level 210 (FL210) is 21,000 feet, FL320 is 32,000 feet, and so on.

  Below flight level 290, eastbound aircraft (those traveling between 0 and 179 degrees on the compass, where 0 is due north) fly at odd-numbered altitudes, such as FL230. Westbound aircraft fly at even-numbered elevations, such as flight level 240. However, above FL290—at typical cruising altitudes for large jets—all flights are set to alternating odd-numbered altitudes, with eastbound aircraft flying at FL290, 330, and 370, and westbound flights at FL310, 350, 390, and so on.

  Of course, there are always exceptions to these rules, and different countries have slightly different regulations. For example, both China and Russia use the metric system for speeds and altitudes.

  Old Systems, New Systems

  Air traffic control has been the focus of a lot of concern around the world, and especially in the United States, where much of the equipment used would be considered obsolete in any other industry. Yet because of the enormity of safety issues involved in air travel, change happens extremely slowly. Nevertheless, in the years to come, old-fashioned radar screens will increasingly be replaced by computer screens fed by satellite-based Global Positioning System (GPS) information, and communication among various controllers and airlines will likely become much easier.

  Hang gliders and other unpowered aircraft in the United States can legally fly up to an altitude of 17,999 feet in powerful updrafts of air. Technically, they could fly even higher, but all aircraft at 18,000 feet or higher must be regulated by the federal air traffic control.

  Air traffic control is already becoming increasingly computerized, as software tools at traffic controller’s fingertips make it possible to manage more aircraft than ever before in busy airspaces, such as those around Chicago and over the North Atlantic. Some researchers today believe that future air traffic controllers will work in computer-generated, three-dimensional environments, complete with virtual-reality goggles and gloves, where they could “fly” through the airspace and see a complex matrix of aircraft from any angle.

  Commercial pilots who fly on international flights and the flight controllers whom the pilots talk to are required to be able to speak English, the international language of flight. When a French airline travels to Germany, all air traffic communication is handled in English. However, pilots making domestic flights within their own countries sometimes speak with the controllers in their own language.

  Airplanes often cruise at around 35,000 feet. That sounds like it’s pretty far up, but compare this altitude to the size of the Earth itself: If the Earth were shrunk down to the size of a typical desktop globe, the airplane would be cruising at only one-tenth of an inch (2.5 mm) off the surface.

  Note that when you’re flying at cruising altitude, the stars don’t appear to twinkle—the lights on the ground do. The twinkling is caused by heat and particles in the lower atmosphere.

  The larger the airplane, and the slower it is flying, the more powerful its wingtip vortices. If you stand below a jumbo jet when it lands, yo
u may even hear a flapping sound and see ribbons of water vapor, both created by the wingtip vortex.

  From Point A to Point B

  In theory, the shortest distance between two points is always a straight line, but figuring out the shortest distance between two airports isn’t so simple. Airplanes almost never travel in straight lines from place to place (except on very short flights). Rather, they take a route based on legal restrictions, optimum fuel efficiency, and shortest time in flight.

  For example, it’s obvious that the fastest way to travel from San Francisco to Tokyo is directly west, over the Pacific Ocean, right? Not so. Using a string and a globe, you can see that the shortest distance is to fly north toward Alaska, then west toward Russia. You’re still flying in more or less a straight line, but it’s over the curvature of the Earth, so the path appears bowed on a map. In general, the farther east or west you need to travel, the closer to the poles you’ll fly.

  Legal Restrictions

  Sometimes airlines are forbidden to use the shortest path because of sensitive geographic politics. American aircraft have to get special permission to fly over countries such as China and Russia. And even domestically, they’re prohibited from flying too close to nuclear power plants, military installations, and other “no fly” zones.

  All U.S. airlines (as well as those of most other countries) have to follow another important legal restriction: Two-engine aircraft must remain within a designated amount of flying time from an airport, in case an engine fails. These aircraft are designed to fly just fine at a lower cruising altitude with just one engine, but no one wants to take a chance that the other engine might fail, too. The rule used to be 60 minutes from an airport, but in 1985 the Federal Aviation Administration (FAA) instituted the ETOPS (Extended Twin-engine Operations) program, which specified that these aircraft could fly up to 120 minutes from an airport, as long as the airline followed more strict maintenance and operations guidelines.

  [Flying across the American Midwest] is really one of the odd sights of the world, and it is strictly an air sight: a whole country laid out in a mathematical gridwork, in sections one mile square each; exact, straight-sided, lined up in endless lanes that run precisely—and I mean precisely—North-South and East-West. It makes the country look like a giant real-estate development; which it is. One section has 640 acres. A quarter section, 160 acres, is the historical homestead.

  —Wolfgang Langewiesche, A FLIER’S WORLD

  The difference between 60 minutes and 120 minutes was dramatic: Before 1985, almost every trans-Atlantic flight was on a four-engine aircraft, like the Boeing 747, because a twin-engine would have to follow a circuitous route that was far from fuel-efficient.

  In 1989, based on extensive studies of the integrity and durability of modern jet engines, the FAA extended the ETOPS limit to 180 minutes. This allowed airlines to fly twin-engine aircraft almost anywhere in the world, including Hawaii. In the year 2000, the FAA extended it even farther, letting some Boeing 777s fly 207 minutes from an airport, which permits even more direct routing between the United States and Asia. Today, the majority of flights across the North Atlantic are flown on the twin-engine Boeing 767.

  Of course, the ETOPS limits still don’t allow for the most efficient routes on some international flights. For example, flights between the United States and Japan still have to hug the coast of Alaska a bit more than airlines would like.

  In the near future, the FAA may raise the ETOPS limit for some aircraft to 240 minutes. One likely result of this decision would be the closure of some very remote airports—such as the one in the Midway Islands in the Pacific Ocean—which are kept open at great cost by the aviation industry for the sole purpose of extremely rare emergency landings.

  Flights, flight maps, and flight speeds are always measured using nautical miles, which are different from ordinary miles or kilometers. One nautical mile is equal to one minute of arc along the length of a great circle (a circle that encompasses the Earth, like the equator). That means 1/60 of 1/360 of the length of a great circle. Unfortunately, the Earth isn’t a perfect sphere, so to avoid confusion over which great circle, the official nautical mile equals 6,076.1 feet (1,852 meters). That makes it about 1.15 times a mile, and 1.85 times a kilometer. A knot means “nautical miles per hour,” so 100 knots equals 115 mph.

  Weather

  Many people don’t realize that the same flight may use a different route each day. The reason? The weather.

  Each airline has its own team of meteorologists who forecast the weather and help figure out the best routes to fly. Of course, commercial airplanes always avoid the centers of thunderstorms or clouds of volcanic ash, which can sometimes make for indirect routes. But airplanes may also fly seemingly odd routes in order to avoid or get closer to jet streams, which are very powerful high-altitude winds that blow from west to east (in both the northern and southern hemispheres), especially during the winter months. Streams can be 100 miles wide and 2 miles from top to bottom, often blowing at more than 150 mph (130 knots) at the center.

  A jet stream moving at this speed would either add or reduce 150 mph from a plane’s air speed, depending on whether the aircraft is heading east or west. That is why it often takes about an hour longer to fly to the United States from Europe than the other way around. So, each day, airlines and government officials adjust the long-distance flight routes, directing eastbound airplanes into the jet stream, and westward flights out of it.

  Sky Highways

  Navigation and air traffic control also keep airplanes from flying in straight lines from departure to destination. In the early days of aviation, pilots had to watch for landmarks on the ground to know where they were; sometimes airmail companies would even light bonfires on hilltops as beacons that their pilots could follow. It’s not so different these days, except the beacons are radio transmitters sending out VOR (Very-high-frequency Omnidirectional Range) signals.

  The Earth is spinning in space, and any given point on the equator is traveling eastward at over 1,000 mph (higher latitudes travel more slowly, as they have fewer miles to cover in the same amount of time). Fortunately, pilots never have to adjust for the rotation because the atmosphere spins at about the same rate. Wind speeds can make an even greater difference—an airplane flying eastward in the jet stream would be traveling at more than 1,700 mph (as seen from outer space).

  Before takeoff, the airline gives the pilots a flight plan detailing each point along their route. A 1,000-mile flight might include five VOR beacons, over which the airplane will fly as it makes its way in a relatively straight line from signal to signal. The paths between these beacons—often called corridors or highways in the air—are about nine miles wide and are clearly marked on aeronautical charts.

  For instance, a flight from San Francisco to Seattle would likely be “vectored” over four cities, each with a VOR station named with a three-letter code: Oakland (OAK), Red Bluff (RBL), Medford (OED), and Portland (PDX). Some VOR stations are in towns with small airports, and others are transmitters in the middle of nowhere set up by the government.

  If your flight is running late, the pilots may ask air traffic control for a more direct flight, perhaps picking different VOR stations or even bypassing one or more beacons. This is increasingly possible due to Global Positioning System (GPS) technology that enables pilots to determine their exact location based on signals from satellites. In the future, GPS combined with longer-range airliners will make more direct paths possible, shortening flights and saving fuel and money.

  From the air, the distinctions between residential, commercial, and industrial areas are easily understood while town, county, and state boundaries go unseen.

  —Oliver Gillham, THE LIMITLESS CITY

  Things That Go Bump in the Flight

  It’s a natural human reflex to attempt to make sense of our experiences. So if you hear a series of loud noises, you’ll wonder what caused them, and you’re not likely to feel at ease until your imagining
s are either confirmed or replaced with a more plausible explanation. Similarly, if someone tells you that you can’t use your cell phone on an airplane but you’re welcome to use the expensive built-in phone in front of you, your curiosity might naturally be piqued.

  The next few chapters should help make sense of your experiences while flying—the bumps, the noises, and the announcements. Plus, there are some suggestions in case you experience anxiety or are concerned about your general health in airplanes.

  Bumps and Noises of a Typical Flight

  The next time you’re a passenger in a car, try this experiment: Sit in the backseat and keep your eyes closed from the time the ignition is turned on until you’re parked and the ignition is turned off. Of course, you probably won’t actually be able to keep your eyes closed that long because the experience will be too disorienting and scary. When we can’t see what’s going on and why, every bump in the road is a surprise, every sound is magnified, and every sudden deceleration feels like impending doom.

  Sound familiar? Even people who aren’t fearful of flying often find the plethora of noises and bumps on an airplane mystifying, if not downright anxiety-provoking. It doesn’t have to be that way, though.

  If you could sit in the cockpit with the pilots, the source of most sounds would be immediately obvious (“Oh, I heard that whump sound because the pilot just retracted the landing gear”). Unfortunately, that isn’t possible, so the rest of this chapter is devoted to explaining all of the things that go bump in the flight.

  The Push Back

  When you first step onto an airplane, it’s often “plugged in” to the airport’s power supply in order to run the lights, air-conditioning, and other electrical devices. However, depending on the airport and aircraft, sometimes the power comes from the airplane’s Auxiliary Power Unit (APU)—a small jet engine near the tail which may sound like a high-pitched whine.