The Flying Book

by David Blatner

DEAD RECKONING: An unfortunate twist of the abbreviation ded. reckoning, from deduced reckoning. If you know where you started, you can deduce where you are by calculating compass direction, your air speed, wind direction, and so on.

  CELESTIAL NAVIGATION: You can approximate where you are by watching the stars.

  INERTIAL NAVIGATION: If you set a gyroscope spinning on a North-South axis, it will by its nature keep spinning in that direction. If you put that gyroscope on a platform that can rotate freely, you can measure how much the platform turns to always know the direction in which you’re heading. Match that with sensors that measure acceleration, and you (or a computer) can calculate exactly where you are.

  RADIO NAVIGATION: If you know exactly where two or more radio signals are coming from, you can accurately measure where you are in relation to those signals. There are several types of radio navigation, including VOR (Very-high-frequency Omnidirectional Range) and GPS (Global Positioning System). These days, pilots and autopilots generally use radio and inertial navigation systems to get where they’re going. Passenger airliners are always fitted with several different technologies, just in case one isn’t functioning correctly.

  Cockpit Instruments

  If you’ve ever glanced into a cockpit (also called the flight deck) while boarding a flight, you probably noticed that the pilots seem to be completely surrounded by dials, knobs, buttons, and gauges. Many passengers wonder how the pilots ever make sense of it all. It turns out that it’s not as complicated as it seems.

  First, remember that there are two of every important indicator—one for each pilot. In some cases, there’s even a third, which can be checked if one of the other two seem faulty. Second, many of the buttons you see (especially those little black ones on the cockpit’s ceiling) are circuit breaker switches. There are hundreds of these things, and if a breaker trips (which isn’t a big deal), it pops up so that it’s easy to spot.

  Also, there are often two or more instruments that do more or less the same thing, but in different ways. For instance, there are at least four different navigation controls, some that use gyroscopes, others that detect radio signals from the ground, a GPS unit, and so on. This kind of redundancy is one reason flying is so safe.

  Pilots don’t focus on any one indicator for very long; rather, they scan the instrument panel for deviations from the norm, much as you might scan the dashboard of your car to see if a warning has lit up or any dials are too high. Remember that pilots have typically flown more than 2,000 hours in other airplanes before they are even considered for a job at an airline—they’ve had plenty of time to get used to what looks normal in a cockpit.

  The word cockpit originally referred to a place for fighting roosters, and in Shakespeare’s time the word described the lowest seating area in a theater (where the poorest people would stand). Later, it came to mean the area from which a boat was steered, usually near the stern and lower than the rest of the deck. This nautical term was first applied to airplanes in 1914.

  The world’s record for consecutive loops in an airplane—2,368—was set in 1986 by David Childs in a specially designed acrobatic aircraft.

  Why Use Instruments

  You may have also noticed how small the cockpit windows are and wondered if the pilots have a good enough view of what’s going on around them. Sure, it’s usually important for the pilot to see when taxiing around the airport, and the windows provide more visibility than you’d think. On clear-weather days pilots are responsible for paying attention and visually avoiding other aircraft (over and above the instructions from air traffic control). However, from takeoff to landing, almost every decision is based on what the pilots read on the instruments, not on what they see. In fact, the pilots could probably fly the airplane even if there were no windows at all.

  The same goes for what the pilots feel. Commercial airline pilots are trained to trust the instruments more than what they feel in their bodies because it’s possible to mistake sensations and become disoriented, especially when flying in a cloud or at night. For instance, the human body can sense when an airplane speeds up and slows down, but it’s terrible at figuring out how fast the airplane is actually moving, especially when the speed isn’t changing.

  Worse, our senses cannot detect a banked turn. (In a banked turn, the wings are tilted and the airplane turns through the sky like a racecar on a banked racetrack.) It’s not just our senses. If you hang a small weight from a string (what carpenters call a plumb bob), you expect that gravity will keep it pointing directly toward the earth. However, even in a steep turn, the weight actually stays pointing toward the floor of the airplane. This is why you can sit for thirty minutes oblivious to the fact that your airplane is turning in circles in a holding pattern above Chicago.

  National Geographic explorer Mike Fay reports that many Africans in small villages (few of whom have ever flown) have a word for the human-made objects that they occasionally see flying overhead. They call them Boeings.

  On a smaller, more nimble aircraft, you could even pour water into a cup sitting on a horizontal surface while the airplane peforms a barrel roll (banking and rolling all the way over, as though it were spiraling along the inside of an imaginary barrel).

  In the early days of aviation, before proper instrumentation, flying in the clouds was incredibly dangerous as aircraft would turn and spin without the pilots realizing it, resulting in death spirals. When a pilot cannot clearly see the horizon, he or she must never make a decision based on a bodily sensation, especially if it disagrees with the cockpit instruments.

  The Instruments

  Flight deck instruments come in all shapes, sizes, and configurations. However, whether you’re in a little Cessna or a big Boeing 777, the aircraft always has four basic instruments right in front of each pilot, indicating air speed, altitude, compass heading, and attitude (that is, the artificial horizon, which offers a pictoral representation of the airplane against the outside world). In older aircraft, these are usually dials and gauges; however, most newer aircraft have “glass cockpits” in which many of the traditional instruments have been replaced with computer screens that provide the same information and more.

  These are, of course, accompanied by dozens of other instruments, including engine indicators (which show engine thrust, rate of fuel consumption, speed of engine rotation, temperature of exhaust gasses, and so on), hydraulic and electrical system gauges, anti-icing controls, and radios for navigation and communication. The autopilot (plus its backup systems) usually sits between the two pilots at the top of the “dashboard,” just above the landing gear controls.

  On most aircraft, each pilot sits in front of a control wheel mounted on a control column. Moving the column (or “stick”) forward or backward adjusts the elevators in the aircraft’s tail to lower or raise the nose of the airplane. The wheel adjusts the ailerons on the wings, which—along with the rudder—help turn the aircraft. At the pilot’s feet are pedals; the lower part of the pedals controls the rudder (if you press gently on the right one, the airplane turns to the right); the upper parts are wheel brakes, which of course have no use while in flight. The two sticks and wheels are connected, so that as one pilot moves a set, the other set moves, too.

  There are always exceptions, however. On the jet airliners built by Airbus Industries, the control wheel is replaced by a joystick set off to the side; the pilot can move the joystick forward, backward, to the left, and to the right to control the elevators and ailerons.

  Fly by Wire

  There is another difference between Airbus aircraft and most other airplanes: Airbus jets are based on fly-by-wire technology. In a jet like the Boeing 737, the control wheel and pedals are attached to cables, pulleys, and hydraulic lines that travel from the flight deck back to the wings and tail. In fly-by-wire aircraft, however, the cockpit controls send electrical signals to computers, which in turn pass on electrical signals to mechanical actuators that adjust the flaps, ailerons, and so on.

  Most newer mi
litary jets use fly-by-wire technology, as does the Boeing 777. Not only is fly-by-wire technology easier to build, maintain, and control, but it can considerably reduce the weight of an aircraft, as computers and wire weigh much less than hydraulic fluid, cables, pulleys, and the trappings of the older control systems.

  If you look closely at the control wheel or the control joystick in the cockpit, you’ll notice one or more finger triggers or buttons. Though they look like gun triggers, the truth is much less exciting: One button lets the pilot turn the autopilot off. There is also a control for adjusting the angle of the horizontal stabilizer.

  The pilots can only see about half the wing from the flight deck, and they can’t see the tail at all. Some airlines are exploring the use of tiny video cameras mounted outside the aircraft to transmit images to the pilots.

  Nevertheless, Airbus and Boeing still differ in their fly-by-wire philosophies. Ultimately, in fly-by-wire systems, the computer is really flying the airplane, with input from the pilots. Of course, the computer is programmed not to exceed certain constraints—maximum speed, maximum turning angle, minimum speed to avoid stall, and so on. But although an Airbus jet pilot cannot override these limitations, a Boeing 777 pilot can in an emergency.

  Some industry insiders argue that Airbus trusts computers to make better decisions than pilots; others hold that Boeing is playing to characteristic American bravado. However, at the end of the day, each manufacturer has convincing arguments for why its method is better.

  Warnings

  Pilots also get help from the cockpit’s many electronic warning systems, which flash lights, sound sirens and bells, or “speak” messages with an electronic voice to get the pilot’s attention when necessary. For example, the Traffic and Collision Avoidance System (TCAS)—standard on jet airliners—backs up the air traffic control system by monitoring all other aircraft in the vicinity during flight and constantly calculating whether any of them are on a collision course with the airplane in question. In the very rare instances when two airplanes are headed for the same airspace, the two TCAS systems sound a cockpit alarm and then shout at the pilots with an electronic voice to ascend or descend (the TCAS units communicate with each other, so both aircraft aren’t given the same signal).

  The brakes on a jet airliner can take forty-five minutes to cool down after landing. And while jets do have parking brakes, the normal brakes cool down faster when the parking brakes are turned off, so to keep the airplane in place at the gate, the ground crew uses triangular chocks in front and back of the nose wheels.

  Similarly, the Ground Proximity Warning System (GPWS) constantly compares the current location of the aircraft with built-in electronic maps of the Earth’s terrain. If the aircraft is headed toward the ground or a mountain, the GPWS activates an alarm that literally yells, “Pull up! Pull up!” Since 1976, when this system became standard equipment on airlines, the number of crashes due to something euphemistically called controlled flight into terrain has dropped radically.

  Other cockpit warning systems include weather radar, wind shear detection devices, and alerts that sound off if the airplane exceeds the maximum speed, deviates from the autopilot settings, or is in danger of stalling. There are even warnings that squawk if the flaps, spoilers, stabilizers, and other control surfaces aren’t in the proper position at takeoff or landing.

  What Is Used?

  Believe it or not, during a typical flight, pilots use about 80 or 90 percent of the knobs, dials, and switches in the cockpit (not including the circuit breakers, of course). This is one reason most pilots are rated to fly only one type of aircraft at a time. They must be able to find the right switch at the right time without hesitation, almost by reflex, and even though the Boeing 747-400 has all the same instruments as an Airbus 340, they’re arranged differently. Pilots can change from one type of jet to another, but in most cases it requires intensive training.

  Cockpit

  Weight and Balance

  Airplanes have to be balanced in order to fly, without too much weight on one side or the other, or too far forward or back. Engineers figure out the exact place on each airplane from which—if you had a rope big enough—you could dangle the aircraft like a giant mobile. It is then the job of the pilot and the airline to maintain that balance as much as possible when loading passengers, luggage, cargo, food, water, and fuel.

  Theoretically, once an airplane is cruising along through the sky, even a single flight attendant walking to the back of the cabin could tip the aircraft’s nose up very slightly. In reality, however, airlines build in such a large safety buffer to accommodate the vagaries of flying that a large jet can easily stay in balance even if 100 people got up and walked around. It’s easy for the pilots (or, more likely, the autopilot) to offset imbalances by making adjustments to the power or the control surfaces on the wings and tail. However, if the airplane were really off balance—say a few tons of cargo were too far forward—the pilots would have a harder time controlling the problem.

  So before each flight, the airline works out the airplane’s weight and balance, taking into consideration the number of passengers in first and economy classes, the number of crew members, the amount of luggage and cargo, and so on. Instead of weighing each person before he or she flies (which was done in the early days of aviation), airlines use average weights, such as 100 pounds for a child, 150 pounds for a male flight attendant, and 25 pounds per regular bag of luggage. An adult passenger in the summer averages about 160 pounds, but in the winter weighs 5 pounds more (those heavy coats add up). Food and water add a surprising amount of weight to the airplane (water alone weighs 8.35 pounds per gallon), and where all that food is stored at the beginning of the flight is crucial.

  A false balance is an abomination to God, but a proper balance his delight.

  —Proverbs 11:1

  If everyone on an airplane jumped into the air at the same time, would the airplane get lighter? In fact, the opposite is true. Because of a basic law of physics, every action has an equal and opposite reaction, so if you jump into the air, you actually force the airplane downward a little bit, thereby increasing its weight momentarily.

  The Boeing 747-400 can carry more than its own weight. Empty, it weighs close to 200 tons, and it can carry more than 235 tons of cargo, passengers, and fuel on top of that. Total maximum weight is 875,000 pounds (about 437 tons or 400,000 kg), though it must burn off enough fuel during flight so that it weighs less than 652,000 pounds (about 325 tons or 296,000 kg) for a safe landing.

  The airline figures out how best to balance the airplane by determining how much cargo and luggage should go in which compartment under the cabin. On a very light flight with few passengers and little cargo, the airline may ask people to move forward or backward in the cabin—it’s pretty rare, but it happens.

  Finally, after all of the weight variables are inputted, a computer spits out the amount of fuel necessary to take off, fly to the destination, circle around for a while, and then fly to a different airport if necessary. Too much fuel can be expensive in more ways than one: It weighs more than six pounds per gallon, and the heavier the airplane, the more fuel it burns. Then the pilots calculate the proper takeoff speed based on all this information (the heavier the airplane, the faster they need to go).

  On one flight out of Chicago in 1980, the pilots reported that takeoff acceleration was slower than expected and that the jet required more than the normal amount of power to take off and cruise. The flight was completed without trouble, but a later investigation found that most of the passengers on board were coin collectors traveling to a convention, and their carry-on luggage contained over a ton of coins—a bizarre circumstance not factored in by the pilots or the folks in the airline’s weight and balance department.

  Runways

  In many ways, taxiing around airport runways is more difficult for pilots than flying. Any large airport is sure to have at least two runways and over a dozen taxiways filled with airplanes at close range.
In fact, it can be so confounding that pilots often familiarize themselves with detailed maps of airports before landing. Fortunately, most of the strange signs, markings, and antennae that you can see around the airport are not nearly as mysterious to pilots as they may seem to you.

  For instance, runway numbers seem random, but they’re not: Add 0 to the number, and you’ve got the runway’s compass reading. On a compass, 0 degrees and 360 degrees both point north, and 180 degrees points south, so when you land on Runway 11, you’re facing almost due southeast (110 degrees). The same strip of concrete approached from the opposite direction is called Runway 29. Runway 17L indicates that the airport has two parallel runways, and this is the one on the left (the other runway would be numbered both 17R and 35L).

  Taxiways are named, too, and air traffic control typically instructs the pilots which runway to land on and which taxiways to use. (There’s some flexibility here, however, and if a pilot misses a taxiway, he or she can usually take the next one.)

  Taxiway names begin with a letter, like B6 or A2, but unfortunately, each airport has its own naming conventions, so these names are somewhat arbitrary.

  The airport runway is the most important main-street in any town.

  —Norm Crabtree,

  aviation director for the state of Ohio

  Runways at major air carrier airports are painted with a series of large white stripes that pilots can see from a distance. First there are eight stripes along with the runway number (each digit is usually thirty feet long and ten feet wide). Five-hundred feet beyond that are six stripes—this is officially the beginning of the touchdown zone. Another 500 feet down the runway are two really thick stripes, which are what pilots aim for when landing. Finally, there are four stripes that mark 1,000 feet and 1,500 feet from the touchdown zone. Many runways also have a series of Vs at each end, ends pointed toward the center of the runway, even before the first set of stripes. In addition, there are standard lighting patterns that provide pilots with visual runway information at night.