Whazat Noise

The noises that go along with a flight can tell you a lot about what’s going on.

All of this applies to the Boeing. Those weird French airbusters make different noises. If it ain’t a Boeing I ain’t going…. Yea, ‘Merica and all that.

Before pushback you may hear:

A irregular thumping from under the floor. This is the sound of guys cramming suitcases in the cargo bins. This is always done by hand, since we haven’t come up with a machine that can break things and pull the handles off effectively. 

 The “belt-loader” is a small car chassis with an engine driven conveyor mounted on it. These make a squealing noise when the conveyor bearings are bad. Otherwise they just help to move the bags from the wagon to the airplane.

 On a windy day you may hear a regular clackaty clackaty sound, this is the fan blades of the engine flopping around and touching the sies of the fan shroud as the wind makes the engine turn. With a strong tail wind the engines might even turn backwards. The engines turning like this doesn’t hurt anything but some times it makes a hydraulic system sense a fault and creates a simulated leak.

Near the rear of the plane you might hear a small turbine engine. A loud exhaust noise usually obscures the turbine noise. This little engine is the APU, or Auxiliary Power Unit. It is the power plant for our little airplane kingdom that makes us independent from the world for our power and air conditioning needs while the main engines are shut down.

Many airlines are limiting the use of the APU in an  attempt to save money on fuel. The APU normally provides air for starting the main engines so it is started  about five minutes before push back. Or when the cockpit gets uncomfortable.

The majority of announcements you hear before boarding are FAA required. You already know where the exits are, and the oxygen mask thing will just give you something to mess with while the crew figures out what the hell is going on in the event of blah …blah…

The air conditioning is ALWAYS turned OFF during engine start. This isn’t out of  orneryness, the air systems are needed for the engine’s starter. Generally, an attempt to start an engine with the air conditioning running won’t work and could cause several million dollars in engine damage. And a delay while a new engine is installed.

Occasionally the APU won’t be working and you might hear ground service equipment that provides air for starting the engines. This thing sounds like a low pitched siren and  is really loud. When these things are used both engines will be started at the gate before brake release.

If you are seated at mid-cabin over the wings you might hear a “bareeeep ” sound when the brakes are released. This is the parking brake valve opening. Any time the airplane is stopped for a moment the parking brake is usually set so you might hear this faint noise a few times during taxi.

Wing flaps and leading edge flaps and slats change the shape of the wing and increase the size of the wing . This allows the airplane to takeoff and land at much lower speeds than it ever could without them. If you watch a large bird land you will notice that they always spread feathers out and curve their wings to slow down. It doesn’t make much noise when they do this since birds aren’t hydraulic.

As the wing flaps are extended for takeoff these is a raa raa raa raa raa raa rrrrrr rrr noise from under the floor at about mid cabin. The flaps are mostly mechanical and hydraulically driven. This involves quite a bit of machinery. Most airlines extend the flaps before taxi out. Some complete the before takeoff checklist during taxi out.

If you watch closely you will see the ailerons move up then down and back to neutral at the pilot exercises the controls. This is done to ensure freedom of movement. The ailerons are on the trailing edge of the wing toward the tip.

After takeoff there is a whooosh bathump sound. This is the landing gear retracting.

The flaps are usually retracted in stages after takeoff. This makes more of the raa raa noise.

The assorted bells and chimes are different for each airline. Things that signal disaster for the crew at one company mean that every thing is fine at another. The bells, chimes, and codes change all the time anyway so it would be pointless to explain them even if it weren’t a secret.

You may notice on occasion that engine power is actually increased after takeoff. This is a normal part of power management and will take a few hundred words to explain. The short version is that we usually don’t use all of the power.

The sound of the crew saying thank you is authentic gratitude. Our industry is in big trouble.  Happy Landings.

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4 Responses to “Whazat Noise”

  1. Ornyness? Like part ornery and part horny?

    These Whazat posts are so cool! This one reminds me of people calling into car talk and trying to make the car noises.

  2. Hehe, again a great read. I’m always happy to see that you’ve uploaded a new batch of posts (now Feb 20, 20, and 19). Besides, you write well! Thanks!

    One question: what’s the momentary feeling of uplift during the take-off, maybe a minute or two after becoming airborne? Like when you’re on an elevator going up, and the vertical speed decreases just before the elevator stops and you feel the gravitation weaken for a second. Conversely, on a flight it feels like the plane is beginning to fall down for a second.

    It usually happens after the landing gears have been pulled in, but I’m not sure if it’s related to that as the timing is not always linked to landing gears too directly.

    It also feels like the pilot would be levelling the plane to a more horizontal angle, but again the visual cues and my sense of orientation don’t support this. I feel that the climbing angle usually remains pretty steep for the first five minutes or so, and this effect happens earlier.

    Recognize this? What is it?

    -y

  3. This is a realistic perception. A post explaining some of the sensations we feel during flight is coming soon.

  4. I just started reading your blog and want to say that I really enjoy it. Keep up the fascinating writing, there are people reading!

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