A320 aerodynamic "whoop" sound

[Galdom]

Living about the mid downwind right hand position at Auckland (close to position LOSGA) we tend to get quite a few A320's flying over coming in from the Tasman that are beginning to slow to join either the ILS or set up for a Visual Approach.

Often there is quite a loud whoop sound that starts with a low aerodynamic rumble but increases in pitch fairly strikingly.

Has anyone else noticed this or are there any NZ A320 pilots that might be able to clue me in on the cause of this?

I have two guesses, the speed brakes lowering at the bottom of descent or the first notch of flap being selected and the air rushing through the opening of the LE slats.

Any help appreciated.

[Otto Throttle]

Almost certainly the selection of flaps and slats. It can be so noticeable for those under approaches to airports that often this is the first sound you hear, long before any engine noise.

[Double Hydco]

Not a NZ A320 pilot, but a UK one.

I think what you are talking about is the "howl" that the speed brakes make at high speed.

During the summer we often get a straight in approach across central London in the wee small hours, and have to use some high speed/speed brake to get the height off. I often wonder if the people below get woken up by that noise?

DH

[Galdom]

Thanks for the replies, it is most certainly one or the other!
Certainly, at my location the loudest noise is a 747 with a lot of flap out, oh except for the occasional BN2 at 4am IFR heading to WRE, now that noise drills its way through the deepest sleep.

[JEM60]

I used to live under the Lakenheath approach. The F.15s frequently lowered gear and flaps over my bungalow. A most defiinte shriek from the change in airflow, which went away when the gear had extended. Next door neighbour was a Thomson Captain who enlightened me as to the cause of the noise.

[LN-KGL]

I live direct below one of the fix point (SONER) used on approach to Oslo Airport (OSL) from the south and this whoop is a familiar sound (and an easy way to pick out the single aisle Airbuses if you are not looking). Usually the A32Xs then have a ground speed of around 220 knots, and this is the speed the flaps position 1 is usually selected. Flap position 1 means the slat only is extended (max speed for 1+F is 215 kt), and I suspect it is the air that start to rush through the opening between the slat and the wing that makes this sound. A very short time after this whoop the engine start to spool up a tiny bit (from idle to approach idle), and the sound of this spool up reveals if the engines are CFM56 or IAE V2500. It is indeed still possible to "spot" planes only by sound, and with sites like flightradar24.com you get the definitive answer to what you hear almost instantly without bins

[BusDriver947]

As an A320 driver I think the whoop noise comes from the Speedbrake (spoilers) retracting.

Often stow them over my house on the way into LHR to let the wife know I'll be home soon.

[Galdom]

Ok, it looks like two votes to each possible explanation.

My thinking is its the speed brakes retracting as the pitch of the noise increases which gives the impression of an air gap closing as opposed to opening.

Would love to hear from an NZ A320 driver who would know straight away what normally happens at LOSGA while on the 23L STAR at NZAA.

All said and done, its a neat noise, sounds for all the world like the Jet is coming out of hyperspace or something and is unique to the A320 (we dont seem to get the shorter or longer versions into Auckland)

Thanks again.

[OntimeexceptACARS]

As far as aviation sounds go, nothing was as evocative (for me) when I was growing up, as when I was lying in bed as a schoolboy, half asleep around 10pm, and hearing the distinctive whine of a Vanguard (Merchantman/Mudguard, your choice) trundle to the holding point of my local, then strangely sound quieter under full beans than it was when starting up or taxiing. I lived about a mile from the departure threshold, and on some clear winter nights it was spookily loud. But strangely soothing...

[Ian Brooks]

Yes I remember that well ontime Lol


Ian B