To withstand the landing weight of a fully laden jumbo jet (more than 900,000 pounds), commercial airport runways are between two and four feet thick, typically with various layers of concrete and asphalt. Taxiways are often less thick, perhaps eighteen inches of concrete. It took over 2.5 million cubic yards of concrete to build Denver International airport’s five 12,000-foot runways, plus taxiways.
The choice of runway is based on the prevailing wind direction because airplanes usually take off and land more or less facing into the wind.
One runway always has two numbers (one for each direction), and one number subtracted from the other always equals 18. For instance, Runway 12 and Runway 30 are the same strip of pavement because one side faces 120° (southeast) and the other faces 300° (northwest).
Commercial airports also have a wide variety of antennae around the grounds. For instance, one of the most obvious is the VOR (Very-high-frequency Omnidirectional Range) antenna, which looks like a white missile head coming out of a round plate. The VOR antenna beams different radio signals in each direction so that pilots can determine where they are in relation to the airport, even in low-visibility weather.
Similarly, the ILS (Instrument Landing System) antenna looks like a kids’ jungle gym next to a red-and-white shack (which houses the electronics for the system). Commercial jets have special radio receivers that pick up on the ILS signal to help in the runway approach, guiding the flight path both horizontally and vertically.
Tired of airplanes flying over your home? Unfortunately, you don’t have much say in the matter. If you own your home, you control only about 500 or 1,000 feet of airspace above it. The law states that airplanes are allowed to fly freely above that. Individual countries do have sovereignty over the airspace above their territory, however.
Runway numbering is always based on magnetic north rather than geographic (or true) north. Because the Earth’s magnetic poles are about 1,000 miles (1,600 km) away from the geographic poles, true north (“up” on a map) and magnetic north (what you see on a compass) are rarely the same thing. In some places, like the state of Washington, they may differ by more than twenty degrees!
The blast of air from jet engines at takeoff is so great that it would quickly erode any soil behind the runway. (Even 100 feet away, the exhaust from a 747 engine causes a 150-mph wind.) Instead of soil, some airports use precast concrete slabs seeded with hardy grass.
King Khalid International Airport in Riyadh, Saudi Arabia, is the world’s largest airport; it covers 55,040 acres (22,016 ha). However it only serves about 8 million people each year. Chicago’s O’Hare airport is about 7,000 acres (2,800 ha) and serves more than 65 million people each year.
The hotter the temperature or the higher the altitude, the thinner the air so the faster airplanes need to travel to take off (because thin air gives less of a boost). So in hot climates the runways have to be longer. The Doha runway in the Persian Gulf is 15,000 feet long. The longest runway in the world is at Edwards Air Force Base in California: 7.5 miles long.
The Fear Factor
Studies show that as many as half of all passengers have some qualms about flying these days. That’s not surprising given the threat of terrorism, media exposés about the aviation industry, and the fact that the majority of passengers know less than you do about how airplanes work (now that you have this book). But how dangerous is flying, truly? If flying is as safe as everyone insists, why do airplanes sometimes crash? And is there anything you can do to better your chances of surviving one of those extremely rare events?
While the next few chapters look at some of the less-fun aspects of flying, they also explore the role of the flight attendant, why airplanes cause some folks so much anxiety, and why the media sometimes appear obsessed by aviation disasters.
Flight Statistics
Human beings have a difficult time comprehending very large or very small numbers. In fact, many folks have a hard time thinking about numbers at all! But the statistics, percentages, facts, and figures involving the aviation industry are fascinating, and they help put the whole experience of commercial flight into perspective.
For instance, imagine a sports stadium filled with 45,000 people watching a game. That’s not too difficult to see in the mind’s eye, right? Now imagine forty of these stadiums. Most people find this harder to picture, so try pretending you’re floating in a balloon over an array four stadiums wide and ten stadiums long. That’s a lot of people. In fact, that’s about the number of people who fly each day on American-based airlines: about 18 million.
Who Is Flying?
About 665 million passengers fly on American-based airlines each year—14,500 sports stadiums’ worth. Include the rest of the world, and the number jumps to about 1.6 billion passengers each year. That breaks down to about 4.25 million people (approximately the entire population of Norway) getting on airplanes every day of the year.
New Scientist magazine figured that given the total number of people flying each day and the average distance flown per flight (around 1,100 miles, or 1,750 km), there are about 366,144 people in the air at any given time. While that’s the equivalent to the population of a medium-sized city, it’s only about .0061 percent of the world population. Of course, in reality the number of people fluctuates greatly depending on the time of day, day of the week, and week of the year.
Airplane travel is nature’s way of making you look like your passport photo.
—Former vice president Albert Gore
According to the National Transportation Safety Board (NTSB), in the year 2000 U.S.-based commercial airlines alone flew a total of 11,022,759 flights, covering 7,148,928,000 miles in 17,474,405 flight hours. That’s equivalent to 13,000 round-trip voyages to the Moon.
How Safe Is Flying?
Thinking about extremely small figures can be just as mind-numbing as trying to comprehend the very large ones above. For example, one way to reckon airline safety is by the percentage of airplane flights that crash with at least one fatality. What if air travel were 99.99 percent safe? That would result in three fatal air crashes every day of the year. In fact, air travel is approximately 99.9999996 percent safe. That means only about .0000004 percent of airplanes crash.
But that number is simply too small to be meaningful for most people. Instead, they just think, “Well, it seems like I hear about a lot of disasters.”
Let’s look at some real safety numbers:
More people die in car crashes in the United States in six months than have died in all the airplane accidents worldwide in the last 100 years.
If air travel were as safe as driving in a car, a jet aircraft carrying 120 people would crash without survivors every day of the year.
Of the approximately 2.5 million Americans who died in 1998, more than 700,000 died of heart disease, some 500,000 died from cancer, at least 50,000 died from medical mistakes in hospitals, and more than 20,000 died in car crashes. But not a single passenger died from U.S.-based airliners crashing. Even in 1994, a year with a higher-than-average number of disasters, only 239 people died.
The Bureau of Travel Statistics reports that in 1995 (the most current information available) Americans took approximately 505 million automobile trips of 100 miles or more, and about 22,000 car passengers died. That same year, U.S. air carriers flew about 8.1 million flights, and there were two crashes in which 166 people died. If the average car had 2 people and the average flight had 150 people, there were 22 fatalities per million automobile trips and only .14 fatalities per million air trips—air travel was 157 times safer than driving.
Because people generally drive much more than they fly, let’s look at the relative safety of cars and airplanes based on the distance they travel rather than the number of trips. The U.S. National Safety Council calculates that between 1993 and 1999, passengers were thirty-seven times more likely to die in a car crash than on a commercial flight. Using more conservative crash data, the U.S. Bureau of Transportation Statistics calculated the
number of fatalities per 100 million miles of long-distance travel: 9.3 for cars, 5 for trains, and 1.22 for commercial airlines. Here, flying is almost eight times safer than driving, and almost twice as safe as taking the train.
Those of us who have been around safety statistics long enough eventually get to the point where we are more nervous driving to the airport, and then when we get there and take our seat on the airplane we relax and feel more secure.
—Norman Mineta,
U.S. secretary of transportation
According to a study by Arnold Barnett and Alexander Wang of the Massachusetts Institute of Technology, the odds of dying in an airplane crash vary slightly depending on whether you’re on an international or domestic flight, and whether the airline is from an industrial or developing nation. For domestic flights on an industrial nation’s airline, the odds of dying are about one in 8 million (you have a better chance at winning many state lotteries). Small commuter airplanes in the United States fare slightly worse: The odds are about one in 2 million.
According to the Air Transportation Association, 26 percent of Americans took at least one airplane flight in 1978. By 1997, the numbers had swelled to 48 percent. The U.S. Bureau of Travel Statistics reports that one out of six adults in the United States has never flown on a commercial airline.
The odds of your flight crashing are always the same, no matter how often you fly. However, the more frequently you fly, the higher the chance you will someday crash (just like the more lottery tickets you buy, the more likely you are to win). Fortunately for frequent flyers, the difference is incredibly small. If 1,000 people flew every day for thirty years, only one of them would likely crash.
For international flights, the odds of a fatality drop to one in 5 million—curiously, this figure is about the same whether it’s an industrial or developing nation’s airline. Finally, domestic flights on developing nations’ jet airlines have the highest fatality odds of all: one in 500,000. That sounds bad, but one in 500,000 is like saying “one day out of 1,300 years.”
Vast Quantities
The infrastructure necessary to maintain millions of flights each week is staggering. For instance, Delta Airlines (the third largest airline in the United States) sells approximately 316,000 airline tickets each day for its 2,660 daily flights (that’s 3 tickets every second and an airplane departure every thirty-two seconds around the clock). Each day, Delta flights burn about 7.5 million gallons of jet fuel and carry about 2,333 tons of mail. To keep the passengers happy, flight attendants on this airline alone serve 164,400 meals or snacks, 461,000 soft drinks, and 225,500 cups of coffee (give or take a few).
So the next time you’re on a flight, munching happily on your pretzels or nuts, consider the numbers, the odds, and the percentages…and as your mind begins to boggle, sit back and smile, knowing that you’re not alone and you’re very safe.
According to the National Safety Council, more Americans die each year by drowning in their bathtubs, falling from ladders, or freezing to death than by flying on commercial airlines.
Why Airplanes Sometimes Crash
There is something about airplane crashes—something gruesomely compelling—that makes people take notice. Perhaps airplane crashes capture our attention because so many people die at the same time. Even a crash that kills only 10 or 20 people becomes national or international news. Of course, more than 2,000 people die each day from heart disease in the United States alone, but they’re spread out geographically so this doesn’t have the same impact.
Airline crashes are extremely rare (see the preceding chapter, “Flight Statistics”), and fatal crashes are even rarer. Even so, studies show that most air travel passengers believe that in 75 percent of airline accidents some or all the passengers die. After all, they reason, how could anyone survive an airplane crash? However, in 86 percent of commercial airline accidents, nobody dies at all. Even in crashes where there is a loss of life, over half the passengers survive on average.
Nevertheless, as rare as airplane crashes are, there’s no denying that they do happen and that they are scary. With this in mind, let’s look at why airplanes can crash and what has been done to make flying safer.
Determining the Cause
When discussing an airline disaster, people like to point to one or two major problems and say, “That’s why the airplane crashed.” But airplanes almost never crash because of one or two problems. For example, ever since 1982, when an Air Florida jet crashed just after takeoff from National Airport in Washington, D.C., the public has remembered “there was ice and snow on the wings.” But in fact, ice and snow don’t necessarily make an airplane crash, and if it hadn’t been for other circumstances this one certainly could have flown given those conditions.
“Ladies and gentlemen, this is your captain speaking. We have a small problem. All four engines have stopped. We are doing our damnedest to get them going again. I trust you are not in too much distress.”
—Captain Eric Moody
Captain Moody made this announcement after his British Airways 747 flew through the volcanic ash shot into the sky by the 1982 eruption of Mount Galunggung in Indonesia. The 747 lost power in all four engines but glided long enough to exit the ash cloud and get three engines working again. The airplane’s windshield was so sandblasted by ash that the landing had to be made almost entirely by instruments, and the airplane had to be towed to the gate because the pilots couldn’t see enough to taxi around the airport.
There are many ways to make airplanes safer, but there is also a point of diminishing returns. Each safety feature costs money, which makes the price of flying higher, which means more people would drive instead of fly, which would lead to more injuries and fatalities (because driving is significantly more dangerous than flying).
The true story is always more complicated, and it usually involves at least five or six factors. Yes, ice played a part in the Air Florida crash, but few people remember the other details—for example, the pilots relied on a particular engine pressure gauge, even though there was plenty of evidence to suggest that the reading was incorrect. If any one factor of many had been different—if only there were no snowstorm, if only the airplane had been deiced more recently, if only a sensor hadn’t malfunctioned, if only the pilots had given the airplane more thrust at takeoff, and so on—the disaster would have been averted.
One factor that almost always appears in airline accident reports is human error—whether by the flight crew, air traffic control, mechanics, or airport security. Paradoxically, the most important reason flying is so safe—the reliance on the extraordinary training and skill of the people involved—is also one of aviation’s prime weaknesses. Airplanes crash for all sorts of reasons, from mechanical failures to acts of terror, from miscommunications to misunderstandings, but it is almost always an extremely rare combination of factors that leads to a disaster.
Attempting to emergency-land an aircraft in the water is called ditching.
The airline industry has come a long way since the first decade of commercial flight, when thirty-one of the first forty airmail pilots were killed in crashes.
It’s understandable that people who have plans to fly get nervous after seeing a news story about a crash; after all, it’s difficult not to compare your flight with the one that crashed. However, air disasters these days rarely have anything to do with the particular kind of aircraft, the time of day the crash occurred, or even the weather. Changing your reservations makes little sense since the chances of the same five or six incredibly improbable events happening at the same time are so slim.
Making Flying Safer
The aviation industry has developed two basic methods for improving flying safety over the years. First, every important system on an airplane has at least one backup system and often three or more redundant backups. The aviation industry simply assumes that there will be occasional human or mechanical errors, and takes this into account when designing airplanes. For instance:
&nbs
p; There are two pilots when one could do the job in a pinch.
There are typically four or five separate navigational devices, including three or four different radio systems.
If one engine of a twin-engine airplane quits (flames out), even on takeoff, the other engine is powerful enough to fly the airplane by itself.
On airplanes that rely on hydraulic power to move the control surfaces on the wings and tail, there are usually two or even four separate hydraulic systems (pumps, fluid lines, and so on). If one goes out, another can take its place in an instant.
Every important instrument or indicator in the cockpit has an identical twin (or even triplet). That’s like having two or three speed dials in your car, just in case one fails.
Airlines tend to avoid showing in-flight movies that include even a mention of airplane crashes. Or they may show an edited version. For example, in the film Get Shorty a brief scene showing an airplane crash was replaced by a scene of a train crash. Similarly, in the film Rainman, Dustin Hoffman’s character insists that Quantas is the only airline that has never crashed. Every airline except Quantas cut that scene before showing it on their flights.
In older aircraft, emergency oxygen is stored in heavy, high-pressure tanks. However, newer aircraft have chemical systems that burn chlorate fuel to generate emergency oxygen. These compact devices are typically stored along with the masks in the seat back or overhead compartment. Don’t touch them, however; they become extremely hot when functioning.
The Flying Book Page 11