The Flying Book

by David Blatner

  Antennae: Three or four small fins spaced out along the top and bottom of the fuselage. Antennas are used for air traffic control communication, inter-company communication, navigation, and so on.

  Empennage: The entire tail section of the airplane (pronounced “empa-najh”).

  Did you know that the propellers on most propeller-driven airplanes can be rotated while in motion? At takeoff, when the need for thrust is greatest, the propellers are set at a low angle so they’re almost perpendicular with the oncoming air. At cruise altitude, the pilots adjust the propellers so that they’re at a fairly sharp angle (closer to parallel with the airflow). It was the Wright brothers who first realized that propellers should be shaped like small wings (airfoils) that are twisted so they have a large angle of attack near the center and a small angle of attack at their edges. This way, they actually both push air back and pull the airplane forward.

  The Concorde and other aircraft with delta wings (wings that look like giant triangles, or the Greek letter Delta) don’t have slats and flaps because their wide wings are already good at flying at low speeds. However, these wings also cause a lot of drag, forcing the Concorde to fly at much higher altitudes, where the air is thinner.

  When describing airplanes in flight, it’s helpful to remember three terms:

  PITCH: The movement of the nose of the aircraft up or down; also called the airplane’s attitude.

  ROLL: The movement of each wing up or down.

  YAW: The movement of the tail pivoting to the left or right.

  Airplanes can adjust each of these angles separately or simultaneously. When turning, airplanes typically roll and yaw; plus, to maintain altitude, the pitch is increased slightly.

  Look closely at the exterior of an airplane, near the nose, and you’ll find several oddly shaped sensors like angle of attack vanes and air temperature probes. Static ports are circular and set flush with the fuselage so that air flows across them. Pitot tubes are L-shaped so that they capture air flowing directly into them. The faster the airplane travels, the more pressure builds up in the Pitot tube. However, the static port always registers the ambient air pressure. By measuring the difference in air pressure between the Pitot tubes and static ports, the airplane’s computer can determine true airspeed.

  Boeing’s design for the Sonic Cruiser.

  Studies show that replacing the horizontal stabilizer on the tail with a set of small wings in the front of the aircraft—called canards—can significantly increase efficiency. A few business jets have canards, and Boeing’s design for the now-scrapped, futuristic Sonic Cruiser aircraft incorporates them.

  The large bulbous objects hanging under the wings (no, not the jet engines; the other things) are called canoe farings because of their boatlike shape. They enclose the bulky mechanisms that extend and retract the flaps and slats during flight.

  Airplanes must have a red light at their left (port) wing tip and a green light at their right (starboard) wing tip. This rule extends back as far as 1864 when the British navy first started placing red and green lights on their ships. Airplanes also typically have a brightly flashing white light that makes them easier to distinguish at night. Sometimes, when flying in or near storm clouds, passengers mistake this flash of light for lightning.

  If you look closely at the top of a jet airliner’s wings, you’ll probably find a row of small metal tabs standing about one inch (2.5 cm) tall, especially in front of the ailerons. These are vortex generators, which actually help the air follow the shape of the wing during flight by creating tiny whirlwinds over the wing. You can sometimes find vortex generators on the tail in front of the rudder, too.

  Like water, air is actually slightly sticky. Just as ski racers wear very smooth clothes to reduce the amount of friction from the air, airplanes must have glassy-smooth exteriors in order to fly efficiently. Don’t let how an airplane looks on the ground fool you; the air pressure inside the airplane at cruise altitude actually expands the fuselage slightly like a balloon so that it’s taut. In fact, doors and windows are often inset a few millimeters from the fuselage so that they’ll expand to be flush with the fuselage during flight.

  Airline windows are built with two or three layers of glass or acrylic to help insulate the aircraft from the harsh outside climate, and they’re actually larger than the window frame in the fuselage, so there’s no way for them to pop out. The plasic window you can touch is actually part of the interior wall, and not the window itself. The small hole drilled near the bottom of the window (which sometimes looks like a small metal cylinder) lets the air pressure equalize between the layers while minimizing the movement of air in the window. As the aircraft reaches cruise altitude, where the outside air is almost sixty degrees below zero (Fahrenheit), the moist air inside the airplane often crystalizes around this small hole. However, as the flight continues and the air inside the cabin dries out, the crystals usually evaporate.

  Most airplanes that fly internationally have their home country’s flag painted on or around their tails. Generally, the flag is facing the proper way on the left (port) side and is painted backward on the right (starboard) side. Why backward? Because that’s how it would look if a real flag were hoisted on a pole above the airplane during the flight.

  Airplane Engines

  Pilots have a saying: “You could fly a barn door if you put a big enough engine on it.” True, a powerful engine is often more important than an elegant wing design. However, in the real world, aircraft engines must not only provide a lot of power (forward thrust) but also be lightweight and fuel efficient. It’s a tough challenge; in fact, the Wright brothers couldn’t have succeeded ten years earlier than they did, simply because a suitable engine hadn’t been invented yet. Sixty-five years later, the first Boeing 747s rolling off the assembly line looked great but couldn’t fly because no aircraft engines on the market were powerful enough. (Fortunately, engine manufacturers caught up within a few months.)

  The engines that drive propellers are more or less like automobile engines—they combust fuel to move piston heads, which turn a crankshaft, and so on. However, jet engines are totally different. In an airliner’s jet engine, air is sucked in by a large rotating fan, then moved through a series of smaller and smaller fan blades, which compress the air down into a small chamber. These fan blades (there are more than 1,000 of them) must be precisely positioned; otherwise, when rotating at high speeds, they could cause an imbalance that could ultimately destroy the engine.

  How powerful are jet engines? In May 2000, a chartered jet carrying the New York Knicks basketball team taxied too close to a line of cars parked on the tarmac. The blast from the taxiing jet flipped head coach Jeff Van Gundy’s car into the air and over three other cars, completely demolishing it.

  In the center of the engine, jet fuel is sprayed into the compressed air and then ignited. Unable to move out the front of the engine, the incredibly hot air expands and shoots out the back, providing forward thrust. On its way out, this hot air moves through a series of small turbine blades, spinning them like windmills.

  Each engine on a Boeing 747 weighs almost 9,500 pounds (4300 kg), costs about $8 million, provides about 60,000 pounds of thrust, and burns about twelve gallons of fuel per minute when cruising. Altogether the four engines account for about 5 percent of the total weight of a full 747 upon takeoff.

  Scientific investigation into the possibilities [of jet propulsion] has given no indication that this method can be a serious competitor to the airscrew-engine combination.

  —British undersecretary of state for air, 1934

  Commercial airliners built since the 1970s operate what are called high-bypass jet engines. In a high-bypass jet, the energy created by the turbine blades not only generates electricity to power the airplane but is also transferred through a shaft back to the front of the engine, where it spins a set of larger blades (the ones you can see from outside the airplane). These large blades are much bigger than the jet engine itself, and they act much
like propellers. Surprisingly, the large fan blades create the majority of the forward thrust—not the “suck, squeeze, burn, and blow” action of the jet combustion chamber. Most of the air that is shot out the back of the engine actually flows over and around the turbine system—hence the name high-bypass.

  Jet engines are very reliable because there are few moving parts. However, because the fans turn at such high speeds, it’s crucial that they be extremely strong. When testing a new engine design, manufacturers strain it to the limits by shooting whole dead chickens into the moving fan blades at 180 mph (to simulate a bird getting sucked in at takeoff or landing), blasting torrents of water and ice into the engine, and even detonating dynamite inside it to ensure that broken fan blades won’t pierce the engine’s exterior shell.

  Even if you strapped on giant wings, you could never fly because the human heart can’t pump blood quickly enough to satisfy the enormous strain of flapping. When flying, a sparrow’s heart pumps more than 450 times each minute!

  Each engine on a Boeing 777 can produce 115,000 pounds of thrust and is wider than the fuselage of a Boeing 727 (about eleven feet, or 3.4 meters, across).

  How do you calculate an engine’s horsepower? Horsepower is, by definition, based on velocity, so you can only describe horsepower at a particular speed. At takeoff speeds, (about 160 mph or 290 km/h) each pound of thrust is about 1/2 horsepower, so the 100,000 pounds of thrust from each engine on a Boeing 777 produce 50,000 horsepower, the equivalent of about 200 Porsches. At 375 mph, the horsepower is twice that (one pound of thrust equals about one horsepower at this speed).

  The human arm provides pretty good thrust: The farthest a paper airplane has ever been thrown from the ground indoors is 193 feet (about twice the length of a basketball court), by Tony Feltch in 1985. Ken Blackburn holds the record for longest sustained flight by a paper airplane: 18.8 seconds. He had to throw the airplane 50 feet straight up in the air to accomplish this feat.

  A turboprop airplane is powered by a jet engine with a propeller in the front—the propeller is rotated by the turbines.

  The Sound Barrier

  People have been talking for years about the “sound barrier” as though it were a physical obstacle, like some invisible gate that had to be blasted through to achieve supersonic (beyond the speed of sound) flight. Of course, before 1947 no one had been able to travel faster than the speed of sound—airplanes would literally fall apart as they approached this “barrier”—but that was simply because scientists didn’t yet understand the dynamics of high-speed flight. Today, military jets regularly surpass the speed of sound.

  So why don’t commercial passenger airplanes fly this fast? Because today the “sound barriers” are economic, environmental, and social. It is significantly more expensive to build and fly a supersonic airplane—some say as much as three times more than regular subsonic aircraft. For instance, the Concorde (the only commercial supersonic airline ever put into service) flies at twice the speed of sound, burns twice the amount of fuel per hour as a Boeing 747, but carries only 100 passengers and almost no cargo.

  There is also some evidence that supersonic aircraft, which tend to fly at high altitudes, can damage the atmosphere’s ozone layer. But one of the largest concerns is that supersonic aircraft create sonic booms, like window-rattling thunder, wherever they go. (It’s a common misconception that these airplanes make a single boom as they pass the speed of sound. Not so; the sound is continuous, but people on the ground only hear the shock wave briefly after the airplane passes.)

  Sound travels by molecules bouncing into one another. (When you talk, your vocal cords vibrate the air, and air molecules bounce all the way to your spouse’s ear). The speed of sound is the speed at which these molecules bounce into one another, and it’s called Mach 1, named after the man who first measured it, Ernst Mach (pronounced “mahk”; 1838–1916). It’s about four times faster in water than in the air, and it’s faster in hot air than in cold air. At sea level, Mach 1 is about 760 mph (661 knots, or 1,223 km/hr). However, it’s colder at airline cruising altitudes, and Mach 1 is only about 665 mph (575 knots, or 1,068 km/hr).

  The Concorde cruises at around 55,000 feet altitude at about Mach 2, over 110,000 feet (35,000 meters) per second. However, it takes off at only about 250 mph and lands at about 190 mPh. During takeoff and landing, the aircraft’s long pointed nose tilts down so that the pilots can see the runway.

  The reason sonic booms sound like thunder is that a crack of thunder is actually a sonic boom created by lightning, which heats the air around it so fast that it expands faster than the speed of sound.

  A boat moving in water pushes some water ahead of it, and airplanes do the same thing with the air. However, at Mach 1 the airplane is moving at the same speed that the air molecules can push forward, and beyond Mach 1 (Mach 2 is twice the speed of sound), the airplane moves faster than the molecules can move. This creates a sharp shock wave where the air transitions from not moving at all to suddenly being very compressed, and the shock wave ripples out for many miles, like a wake behind a boat.

  Unfortunately, as airplanes approach Mach 1, there is increased drag and they fly less efficiently. Today, almost all commercial airliners fly between Mach .80 and .86 (each airplane model has its own optimum speed). That’s about 560 mph (485 knots, or 900 km/hr) at cruise altitude. Also, remember that air speeds up as it travels over the wing, so some parts of the wing may experience supersonic flight even when the rest of the airplane is below Mach 1.

  How Fast Does It Fly?

  The common housefly beats its wings up to 200 times per second to fly about 4 mph.

  The woodcock is the world’s slowest-flying bird, clocking in at about 5 mph.

  The Wright brother’s original airplane, the Flyer, flew about 10 mph, though a later model could fly up to 30 mph.

  In 1979, cyclist Bryan Allen became the first pilot to fly across the English Channel using only human power. The seventy-pound aircraft, called the Daedalus, flew at about 18 mph.

  The dragonfly has been around for about 250 million years and can fly 30 mph.

  Blimps typically fly at about 35–40 mph. That’s about the same speed at which flying fish glide through the air for up to 150 feet.

  Boomerangs rotate about ten times per second at about 50 mph.

  The Canada goose has a six-foot wingspan and can fly hundreds of miles at 60 mph.

  Flying disks, like the Frisbee, aren’t just toys. They can soar at 74 mph.

  A hockey puck “flies” across the ice at 90 mph.

  The Voyager was the first airplane to fly nonstop around the globe on a single load of fuel, cruising at 122 mph.

  The popular Cessna Skylane private airplane cruises at about 170 mph, about the same speed as a fast-flying golf ball.

  Many helicopters average only 60 or 70 mph, but a fast helicopter like the AH-64A “Apache” can fly up to 225 mph.

  The peregrine falcon (Falco peregrinus) is the fastest animal on Earth: It can fly (in a dive) at 217 mph (about 90 meters per second).

  The Gulfstream III executive jet can fly eight passengers and a crew of three at 509 mph.

  The fastest propeller-driven aircraft is the “Rare Bear,” a Grumman F8F2 Bear Cat that has flown at 528 mph.

  The Boeing 747 has a cruise speed of about 580 mph.

  The U.S. Air Force’s F-86E “Sabre” flew at speeds up to 690 mph during the Korean War.

  In 1947, Chuck Yeager broke the sound barrier for the first time, flying at Mach 1.06, about 697 mph, in a Bell X-1 nicknamed “Glamorous Glennis.” The Concorde flies at a cruising altitude of 55,000 feet (16,765 meters) at Mach 2, or 1,336 mph. It can fly 3,740 miles without refueling. The McDonnell Douglas/Boeing F-15 “Eagle” can fly at about Mach 2.5, or 1,875 mph.

  The comic book character Superman is said to fly faster than a speeding bullet. The bullet from a .38 Special “flies” only around 600 mph. However, the bullet from a .22 cartridge rifle exits the muzzle at about Mach 2.6, o
r 2,000 mph.

  In 1974, the Lockheed SR-71 “Blackbird” set a transatlantic record by flying 3,470 miles from New York to London in just under two hours, and on July 28, 1976, it set a world speed record at Mach 3.2 (2,193 mph).

  The fastest airplane ever flown was the X-15, which in 1967 reached Mach 6.7 (4,520 mph). It was able to fly as high as 354,200 feet, or 67 miles above the Earth.

  The space shuttle reaches Mach 21 (about 18,000 mph) when it reenters the Earth’s atmosphere. The friction of the air moving over its special protective tiles heats them up to more than 2,200°F.

  The Gimli Glider

  The next time you’re at a party, ask your fellow guests: “What do you get when a jet airplane, flying at 41,000 feet, completely runs out of fuel?” Most people immediately picture an aircraft plummeting to the ground like a rock—after all, how can an airplane fly without fuel? Now tell them this story:

  On July 23, 1983, Air Canada Flight 143 took off from Ottawa on its way to Edmonton. The two-engine Boeing 767 had no trouble flying to a cruise altitude of just over seven and a half miles in the sky. Suddenly, halfway through its journey, just after the passengers had finished their dinner, the left engine went out. Airplanes are designed to be able to fly with one engine inoperative, but the pilots decided to reduce altitude and were beginning to redirect the airplane to a closer airport when the second engine flamed out.