So this is actually a very common occurrence but I'm wondering why they are making this specific noise. It sounds like a car when downshifting if that makes any sense. They'll be flying along, and at a certain point in the path the engines double in volume. A few people think that this is the landing gear coming down, but I think they re way too far away for that to be the case. I'm sure someone here knows what it is. These are jets, they are still relatively high up and I believe the ones that make the noise are approaching the airport to land.

I get this all the time and i dont even live near an airport, at first it will seem fairly quiet for a plane and then all of a sudden the volume of it becomes craazy lol, thought it was a nuke the first time i heard it

I am no aviation pro, i am sure someone will come up with a good explanation...but it could be simply that they compensate with increased thrust once the airbrakes/flaps are down or something.

Hello all,

Yes, I know the exact noise you are describing and some of you may note that particular types like the 777 seem to do it whilst others dont appear to.

It is not as one poster here suggested, the engine Thrust Reverser's(T/R's) engaging. That is forbidden, highly dangerous and in fact virtually impossible due to multiple safeties designed to stop it from ever happening. If it did the end result would be something akin to the Lauda Air 767 accident that killed everyone onboard. These days it should be impossible for the T/R to cycle until you have weight on wheels and your throttle setting and air speed have reached there thresholds. The CF-6 for example (as used on the 767) has mechanical and electro-mechanical locks and brakes designed to compliment each other. In fact after the Lauda Air tragedy all CF-6 engines were mandated to be fitted with the second system to prevent such an accident from happening in the future.

Although I am in the business I must confess that I dont know the exact cause of the noise but I can make an educated guess. It is almost certainly the auto throttle system cycling to maintain a selected airspeed and altitude. The noise may be caused by the engine's Engine Electronic Control unit (EEC) changing the scheduling of say the Variable Stator Vanes (VSV's) in the compressor and therefore how it sounds. It is definitely not the doppler effect however.

As I said I dont know the exact cause but that is my educated guess. I have asked one or two other colleagues for an explanation but they were not sure either. It is something I do note that we dont hear around the immediate vicinity of the airport, or during takeoff, or engine runs we conduct on the ground whether idle, low or high power runs, so that is why I believe it may be the auto throttle maintaining a selected airspeed in flight. I have as one other poster eluded noticed it some 5-10 mins before they would touchdown at a height of 2-5,000ft. Anyone who can answer that here I would also appreciate it as well.

LEE.

I hear this noise sometimes as planes come over my place descending to land at ABIA. Yeah. some of them are revving their engines. In coming down from about 30,000 feet, they sometimes find that they are gliding down too fast to be at where points X and Y merge and so they must increase power to maintain the correct rate of descent.

I think the weird sound is more noticeable on certain aircraft more than others. The first time I heard it, I thought a plane was in serious trouble because we sometime hear in the details of a crash that witnesses heard the engines revving seconds earlier.

The first few times I heard it I thought it was some hot-rod pilot. I tend to believe that those a/c with the dark (blue?) undersides (United?) are the ones I typically notice producing that sound. So it could be the type of plane or their company's SOP procedure

Had to google a bit, but yes:

Approach and land. Again the flaps and landing gear have to be extended, so expect similar noises to that experienced after take-off. Sometimes pilots have to use their "speed brakes" to conform with Air Traffic instructions. Speed brakes are metal panels that are located on top of the wing and allow the pilot to create drag. Pilots use these when Air Traffic Controllers hold the plane high to meet some requirement.

The speed brakes will cause a slight turbulent feeling throughout the plane and can create a change in wind noise. This is totally normal. During the approach engine noise will increase because the pilot wants to fly a constant airspeed approach to the runway.

To any old timers or cool youngsters like myself... It sounds like forcing a truck into granny gear going too fast.

Thanks everyone who has answered. I never thought it was anything sinister, just always weirds me out. I'll be in bed (hopefully with a nice buxom young lady in my arms) and all of a sudden VVVVVAAAAAAAROOOOOOOOOOoooooooommmmmmmm!

Nice young lady: 'Baby come back to bed.'

Domo: 'Shutup woman we're all gonna die!'

Moment..... ruined.

The extra noise is wind-noise from flaps, gear and/or spoilers. Like wind blown through a whistle. If you've ever sat above the wing on a commercial flight you can see all the "holes" in the wing appear when the flaps come down. The wind is suddenly being blown through all those "holes" and crannies at several hundred knots and being redirected. If you've ever heard the wind through the trees or stuck your hand partway over the opening a vacuum cleaner or out the window of the car at free way speed, you may have noticed the roar produced by redirecting airflow.


With a high-bypass ratio turbofan engine spool-up (and -down) time takes longer than with smaller turbojets. This means a delay to add or subtract power. This is potentially dangerous. To eliminate some of this, the fans are kept at a higher RPM and the plane is made "dirty". The introduction of drag helps reduce airspeed without changing the engine setting. It can be much faster/safer to "clean up" the plane by retracting flaps, spoilers, gear, etc and thereby increase airspeed than might be possible by waiting for the engine to spool up and start producing thrust.