Frequently Asked Questions (FAQ's)
- Are four engines better than two?
- Are jet engines safe?
- Are older airplanes safe?
- Are some models safer than others?
- Are some parts of a flight more at risk?
- Can the doors open in flight?
- Can the wings break off?
- Is turbulence dangerous?
- What are those weird noises we hear during flight?
- Where's the safest place to sit on a plane?
- Why can't airplanes be as strong as black boxes?
Are four engines better than two?
Commercial airplanes with two, three and four engines are equally safe. In fact, the record shows that twinjets have fewer engine problems than airplanes with more than two engines. What's more, twinjets are designed to fly on only one engine for extended periods of time, and oceanic routes are laid out to keep them within easy landing distance of an airport at all times, just in case an engine fails.
What are the chances of both engines failing at the same time? The probability of that happening has been calculated at one in less than a billion per flight-hour.
At least 90 percent of jetliners delivered today are twinjets. They safely serve every type of route, from short-haul shuttle flights to the longest globe-spanning nonstop.
Are jet engines safe?
They are incredibly safe. In fact, engine failure is rarely the cause of either accidents or diversions. Human error accounts for most airplane accidents. On-board medical emergencies cause most diversions.
Concern about engine failure is an understandable holdover from the days of piston powered aircraft. Jet engines are far more reliable than propeller engines. Since the introduction of the jet age in the 1950s, airplane reliability has increased markedly. Based on current engine design, today's engines have fewer problems than ever before.
Are older airplanes safe?
Older airplanes have the same stringent safety requirements as newer planes. The key to keeping them safe is good maintenance, and there are extensive maintenance requirements for all airplanes, young and old, that airlines typically exceed.
In the early '90s those requirements were stiffened for older planes. As airplanes reach certain operational milestones, airlines perform extensive inspections and modifications to the airplane's structure. Sections of skin are replaced. So are door frames, lines of rivets and other structure that may weaken from repeated pressurization and environmental conditions encountered through the years. All of this is done according to a scheduled maintenance plan that's based on years of operating experience.
Many older airplanes also have the latest avionics systems aboard. If an airline decides to keep an airplane in service, it often incorporates new systems that help flight crews do their jobs more efficiently and safely. In fact, the FAA has mandated some of them -- like collision avoidance and ground proximity warning systems.
So, in reality, "older" airplanes have a lot of new parts. They're not as old as you may think.
Are some models safer than others?
Some models have been involved in more accidents than others, but that's because they're more widely used. The only valid comparison to make is of accident rates -- that is, the number of accidents per million departures for each model of aircraft.
When we do that kind of comparison what we see is that all of the commercial jets in service have extremely good safety records. There are slight differences in the accident rate from model to model, but none that would support the conclusion that some airplane models are safer than others -- especially since accident investigators have found the airplane itself the primary cause of only 13 percent of the serious accidents. (About two-thirds of the accidents are due to errors by the flight crew.)
The fact that all models have extremely good safety records is not surprising. All commercial airplanes, whether designed and manufactured by Boeing or by some other company, must meet the same stringent safety requirements before they are certified to enter service.
Are some parts of a flight more at risk?
Some parts are riskier than others, although none are anywhere near as risky as many of the other things people do regularly (like drive a car).
Airplane travel consists of three phases:
- Takeoff and climb.
- Cruise.
- Descent, approach and landing.
Looking at accident rates for each phase, cruise is the safest part of flying. Only about 6 percent of all accidents occur during this phase. Approximately 35 percent of all accidents occur during takeoff and climb. Nearly 60 percent of accidents occur during descent, approach and landing.
Because so few accidents occur during cruise, long flights are not significantly riskier than short ones. If anything, a single, long, nonstop flight is safer than multiple short flights.
Can the doors open in flight?
Hollywood has made quite a few thrillers through the years depicting people getting sucked out of airplanes. It's some people's worst nightmare! It's also extremely unlikely.
First of all, commercial jets are made of extremely strong stuff. The materials are lightweight, but the structure is designed to be incredibly strong. It's also designed to be "fault tolerant," meaning that if one part of structure fails, other parts will take up the loads and the airplane will continue to fly safely. There's also a comprehensive program in place to ensure the structural integrity of older planes through periodic inspections, replacement of structural components, and modifications.
As for the doors, they cannot be opened once an airplane is airborne and pressurized. To facilitate breathing and passenger comfort, airplanes are pressurized to the equivalent atmosphere of 8,000 feet. Since airplanes typically cruise above 30,000 feet, the air pressure inside the plane is much greater than the pressure outside -- and that pressure differential makes it impossible to open the door, even if somebody wanted to do such a thing.
If an emergency landing is necessary, as the plane descends, the pilots slowly depressurize the plane, so the doors can open immediately after the plane touches down. Emergency exits are designed to open once a plane has landed.
Can the wings break off?
Actually, they can, given enough force. For every new model Boeing designs, the wings are bent until they break. Breaking a wing requires far more force than anyone has ever come close to experiencing in actual flight. You may see the wings flapping a bit during turbulence. They're designed to be flexible, in part to ensure they don't fracture. Airplane wings are very strong.
Is turbulence dangerous?
It can be dangerous, which is why it's a good idea to stay seated, with your seat belt fastened. Pilots often know when they're about to enter turbulent air because they regularly review weather information and talk by radio to other pilots ahead of them. However, sometimes they're caught by surprise, especially by "clear-air" turbulence, which can't be seen. Airplanes are designed to ride out turbulence, even severe turbulence, but people on board can easily lose their balance if they're standing or walking down the aisle when turbulence occurs. Even seated passengers can hit their heads on the overhead bins in severe turbulence if they're not strapped into their seat. So the best protection is to stay seated, wear your seat belt, and hold on to the overhead bins or seat backs if standing or walking in the aisles.
What are those weird noises we hear during flight?
In the early days of aviation it was common for people to refer to airplanes as "flying machines" -- and that's exactly what they are. When you're flying, you're inside a large, complex machine, so it's common to hear a lot of strange sounds. Here are some of them:
A drilling sound prior to takeoff and on approach to landing-- That's the sound of the flaps and slats being extended on the wings. These panels, which increase the area and curvature of the wing when extended to facilitate low-speed flying, are driven by a screw mechanism that causes the noise you hear.
A high-pitched whine prior to takeoff-- That's the sound of the engines spooling up for takeoff. Once airborne, the pilot will throttle the engines back, and during cruise the sound of the engines becomes more of a hum than a whine.
Rattling during takeoff or turbulence-- That's the sounds of things being jostled in overhead bins and other parts of the cabin due to engine vibrations on takeoff or turbulence during flight. It's not the sound of the airplane breaking apart!
A thump beneath the floor following takeoff-- That's the landing gear going up into the belly of the plane and the doors to the landing gear bay being shut.
A loud roar following touchdown-- That's the sound of the thrust reversers, which help slow the plane once it's on the runway. They literally reverse the flow of the air through the engines, which is why they are so loud. Airplanes are designed to stop using brakes alone, but flight crews typically deploy the thrust reversers to help save wear and tear on the braking system.
Where's the safest place to sit on a plane?
While some people believe the safest spot is near the wings or toward the rear of the cabin, there's no evidence to support either theory. One seat's as safe as another, especially if you stayed buckled up.
Why can't airplanes be as strong as black boxes?
They could, but then they would be too heavy to get off the ground.
The so-called black boxes house the flight data recorders and cockpit voice recorders that investigators use to help them determine the cause of a crash. They are made of steel so they can survive the impact of a crash as well as fire and immersion in water. Steel is much too heavy for an airplane, which mostly is made of aluminum and various lightweight composite materials.
Still, airplanes are designed to be strong as well as lightweight. In many of the accidents that have occurred, the airframe has remained largely intact following impact with the ground. Much of the destruction has occurred as a result of post-crash fire, which is why a speedy evacuation of an airplane that's gone down is so critically important.