WHAT’S THAT NOISE AND WHAT DOES IT MEAN?
WHAT SOUNDS TO EXPECT FROM BOARDING TO LANDING
An operating airplane makes many different noises. They can be divided into categories: engine noise, landing gear, wing/tail moving surfaces and auxiliary equipment.
As you board, you are likely to hear what sounds like a subtle, but high-pitched whining. This is simply the APU, auxiliary power unit, which provides electricity and air-conditioning to the aircraft while docked at the Jetway. The APU is used instead of the engines to supply this power. It saves gas and keeps the engines shut off until they are truly needed.
Preparing for take-off: The aircraft needs a lot of power to accelerate along the runway and then lift-up (or take-off). The noises you hear are the pilots winding up (or revving) the engines in preparation. Well before actual take-off, your flight crew calculates exactly how much power they’ll need. Many things are taken into consideration, such as weight of the fully-loaded aircraft, weather conditions, length of runway and other things that will ensure a safe and effective take-off. These are some of the tasks the pilots are performing up-front, while you are finding your seat.
While taxiing down the runway, getting in line for take-off, you will hear increased engine noise. Since the plane is now moving, the engines are needed to facilitate that movement. You may hear brakes squeal slightly, this is completely normal. You’re likely to feel a bump or thump as you taxi; the aircraft is simply rolling over small imperfections on the runway itself. It’s just like when you’re driving your car on a road that is not completely smooth. As when driving, bumps and/or a slight shifting cannot hurt you.
During actual take-off, you will hear loud noises emitting from the engines. This is somewhat like the noise you hear when starting your car and stepping on the gas. Obviously, since the vehicle is much, much larger, the noise level is greater. Loud engine noise is completely normal and actually confirms the plane is in good operating order. Without engine power, the plane will not fly. There must be airflow over the wings to create the force which lifts the planes. Keep in mind, the engines are now also supplying power for the entire plane and also provide the cabin air used for pressurization and air-conditioning. Usually several minutes into the flight (sometimes longer) you’ll hear the landing gear being lifted. It is being lifted back into place, until it is needed again for landing. The sound that is made by the lifting of the landing gear (wheels which allow the plane to taxi while on the ground) is a somewhat high-pitched squeal. That’s the gear actually being mechanically lifted. Once in storage mode, you’ll hear a “thump” or “clunk”, which indicates all is well and the gear is where it is supposed to be.
As you climb, you’ll hear some different noises and may experience a slight shift or dip. Climbing to the actual cruising level involves use of the wing flaps, which aid the aircraft during ascent. The wing and tail flaps may be raised (making a mechanical whirring noise), lowered or moved several times, until they ease back to their original position. Because it is not possible for all aircraft to take off in the direction they are heading, you will probably experience the plane turning left, right, or completely around. While adjusting direction, you may feel a slight tilt of the plane; this is completely normal and is nothing to be afraid of.
When you reach your ideal cruising altitude (this is where the airplane will remain for the majority of the flight) you’ll hear something a bit different. The engine power is reduced and the noise level is greatly decreased. Once again, compare this to driving your car. When you reach 50 miles-per-hour and decide to stay there, you simply keep your foot level on the gas pedal and you “cruise”. The car sounds nothing like when you started it, causing the engine to roar. While cruising, you may hear the engines rev slightly; this is the pilot calling on more power. If you do hear an increase in engine noise while cruising, it is more than likely due to: a.) Instructions given by the control tower to the pilot, telling them to fly higher or lower, to accommodate air traffic control. Or b.) The pilot anticipates turbulence and is simply trying to move around it for your comfort.
When you near your destination, you’ll begin descending. Descent often takes anywhere from 20-45 minutes, depending upon many things (air traffic in the area, weather, etc.). Keep in mind, the plane was flying at many thousands of feet and now needs to reach the ground. This is a time when you most likely will feel your ears “pop”. They are only adjusting to the change in altitude. You will “feel” the plane descending and may hear engines rev up and slow down during the process. Once again, you’ll hear the sound of the landing gear; this time being lowered, then locked in place for landing. Once locked in place, you may hear a metal “clunk”; this simply signifies the landing gear is ready to touch down.
When approaching the airport for landing the pilot will reduce the engine power, almost to an idle. The engines are not needed as much during landing and the pilot will be gliding the plane down to the ground.
When the pilot touches down, he redirects the engine thrust that propels the plane forward in order to slow the aircraft down. You will hear the engines rev up once again as the pilot must increase the power to produce enough reverse thrust to reduce speed for landing.
You’ve landed, you’re on the ground! Landing is felt more than it is actually heard. As the wheels (landing gear) reach the ground, you may experience your body being thrust forward slightly. You may feel the plane touch down just once, or bounce ever-so-slightly a couple of times before completing landing. There is no reason to fear a less-than-perfect touch-down; it’s normal and happens often.
The plane will taxi to the boarding gate and you will begin to deplane. During deplaning, you’ll hear the engines begin to unwind. Depending on the aircraft, this may sound like a shrill “weeeeeeeeeeeee” and/or “bzzzzzzzzzzzz”; either is completely normal. You may hear the wing flaps (no longer needed) return to their resting position, ending with a slight “thump”.
If you hear anything we have not discussed or that sounds unusual, do not panic! Just like an automobile may emit a “ping” or clinking noise from time to time, aircraft may too. Also, just like in your car, the noise disappears and, in no way, places you in danger. Do not be afraid to ask a member of the crew to explain any noises you think are strange. The crew is onboard to assist you in having the best possible flying experience. They have usually flown many thousands of miles, have heard every noise possible and can explain them to you.