If you know what's going on, you're less likely to be anxious when you fly. Trouble is, the normal sounds of an airplane are mysterious — and therefore scary — to many passengers.
Tom Roberts, a retired Northwest Airlines captain who works with that carrier's fear-of-flying programs, teaches nervous passengers exactly what is behind every bump, grind and whir during a typical flight.
With the idea that a little knowledge is the best help in facing fears, here's a rundown on what's happening on the runway.
You're still on the ground sitting in your seat, and you hear a soft whining sound that seems to come from the tail.
The pilots are starting the small auxiliary power unit that provides air conditioning and electrical power to the airplane on the ground.
The lights flicker for a moment.
That happens when the external electrical cord, connected to the plane's nose, is disconnected and the on-board electrical system takes over. Using external power is a lot cheaper, so the plane is connected to the airport's power supply most of the time it's on the ground.
There's a funny hissing noise.
As the pilots begin turning on the air-conditioning systems, you hear the hiss of an air-driven air conditioner and feel the cool air.
Thump, thump, thump . . .
That's baggage being loaded.
A really big thump.
That's the cargo bay doors closing. You'll also hear them lock; if the system on the plane is hydraulic, there'll be another whirring sound.
Whir, whir, whir.
The plane has three hydraulic systems and uses a little electric pump to pressurize one of them on the ground. You'll hear it first, then the other ones starting "to talk to each other."
The air conditioning quits.
Pilots are shifting power to the engines to start them. As Roberts explained it, "We need that air to start the engines."
There's a big roaring sound.
The engines have started, and their noise drowns out the other whirs.
The engines sound louder, and the plane moves forward fast.
First, the plane taxis toward the runway and takes its place in the lineup of other planes waiting to be cleared for takeoff. When its turn comes, the engines are boosted to takeoff level — they'll sound much louder — and the plane zooms forward.
It's bouncing.
You'll feel the plane bounce slightly because its tires are still on the pavement. The moment its wheels leave the pavement, the ride becomes smoother. The plane now climbs at about 1,500 feet a minute.
About 10 seconds into the flight you'll feel the landing gear withdraw into the compartments in the fuselage — the body of the plane — followed by thumps when the doors close over them.
The plane feels like it's slowing down.
In less than a minute, when the plane is between 1,000 and 1,500 feet up, you feel a slight reduction in power because the pilot now backs off from maximum power to climb power.
At this point, the plane is going about 270 miles per hour — 250 knots, or nautical miles per hour — the fastest it's allowed to fly below an altitude of 10,000 feet.
"Level-off altitudes are always given to pilots to provide distance between flights," Roberts said.
But, said Roberts, "If you've been climbing at 1,500 feet a minute and the plane levels off, it feels like the airplane went down, when in actuality, we're level."
It will take six to seven minutes to get to 10,000 feet. Above that level, the plane's climb speed goes to about 320 knots. It will level off again at its cruising altitude. There's less friction at higher altitudes, and the airplane's jet engines are more efficient there.
Uh-oh, turbulence.
This is simply bumpy air, Roberts said. Planes fly fine in bumpy air, and it's a normal phenomenon.
Landing already? But we're so far out.
"For every 1,000 vertical feet, this airplane can go 4 miles," Roberts said. "So if you're at 30,000 feet, how far from Minneapolis do you start the descent? About 120 miles."
Why do I feel lighter?
In descent, the engines are pulled back to idle, and the airplane is coasting gently downward, "like a kid coasting downhill on a bike," Roberts said.
Why are we turning so much?
The plane is gradually gliding downward. As it gets closer to the airport, it joins the inbound traffic pattern of flights arriving at the destination airport.
Little noises, funny feelings.
You feel the slight vibration and soft whoosh of air as the flaps are positioned for landing. Next you'll hear the landing gear doors open and the gear come down and lock in position, and you'll feel "lots of little corrections" as the pilot aligns the plane with the runway.
Bump! Roar!
In quick succession, there's the jolt of the huge tires hitting the pavement, the roar of the engines reversing to slow the plane, the sight of the panels or "speed brakes" on the top of the wings coming up to help slow the plane's speed.
Then the pilot starts braking the plane, retracts the speed brakes and steers the plane off the runway and begins to taxi to the gate.