What are you bus drivers doing over my house ?
 

I live in West Swindon (I know - someone has to !) I often sit in the garden watching you guys tootal over but I've noticed with certain aircraft (and I think its limited to orange and white inbounds to Bristol so I'm guessing Airbus?) that you make a most peculiar engine noise approaching my house. It sounds like a hoover being switched on or like a bottle filling up with water (whooo - ooop sort of sound). From Casper it looks like you're in the descent at about FL15 - FL12 approaching POMAX. Just sort of wondered what you were doing to make that sound and why it's only certain aircraft.

As you can tell I'm not a commercial pilot so an idiot's guide would be appreciated and I'll enjoy a gin and tonic in the sun even more knowing what you're up to.

It could be anything really, from deploying speeds brakes. As we descend through 10000ft we have a speed restriction of 250kts, So it could have something to do with that. I fly the Bus and off the top of my head I really cant put a pin on it :confused:

The speed brakes do make a 'descending howl' when deployed. I've heard it several times from the flightdeck. Most noticable in the A319 but I can't recall hearing it on an A320 or 321, probably because the wing is further from the cockpit.

I've also noticed a similar noise when Flaps 1 is selected, this time when seated in the cabin near the leading edge of the wing.

If you lived in Slough instead of Swindon, you might be forgiven for worrying that it was the sound of the bomb-doors opening:

Come, friendly bombs, and fall on Slough!
It isn't fit for humans now....

(J Betjeman, 1937)

Eckhard, I was also thinking about suggesting the flaps, but the gentleman suggested the Aircraft was flying overhead at FL150, Would be strange to start deploying flaps at that altitude on a regular basis.

Yes that's right; probably the speedbrakes in that case.

What! Can't you Poms slow down to 250 without speed brakes? Us colonials would never use the chicken stick on a routine basis like that! :p

Just to back up the original poster.

Aircraft that fly into BHX pass near my house, at appprox 10,000 to 15,000 feet and you can always tell it is an Airbus aircraft, A320/A321, by the sound it makes. Definately an 'air' noise. Not engine.

Also curious.

I live on the Wirral under the flight path into Liverpool.Used mainly by Easy and Ryan.I can tell who is who without looking.The Airbus of Easy has a distinct whine to it,while the Boeing Ryan sounds like a normal plane....if there is such a thing.

Usually around that point we are trying to empty the toilets

Could be an engine intake noice. USN S-3 Viking's nickname was the 'Hoover' because it makes a very distinct noise when power is applied at low/medium power.

Used to play golf at NAS North Island in KSAN and they'd overfly the golf course at very low alititude - whooot, whoooot, whoot. You immediately realize how it got it's nickname.

A-10 and CRJ's have similar engines but different cowlings and the sound is completely different.

Some aircraft wing/flaps make distinct airflow noises as the flaps are extended/retracted. DC-9/MD-80's leading edge extension/retraction is an example. It's probably not loud enough to hear from the ground, especially 10,000-15,000'.

I've also often heard a distinctive whooshing howl on a descending note - duration ~5 seconds - over my home ~20nm west of KDEN. Not associated with climb-thrust (or other) engine noise, so I've assumed it was related to inbound aircraft.

Definitely an "aerodynamic" sound, rather than engine thrust, and at an altitude (~8-10,000 ft. AGL) much too high/far away to be the sound of the mechanical movement/drive systems themselves. So I've always assumed it was flaps or speedbrakes being pushed into the airflow.

I've never been able to spot the specific aircraft type visually. I kinda thought it might be 757 flaps, since they are known to be uniquely "powerful" in affecting airflow, and United flies a lot of them in here. But I'll bow to Tomahawk if he's linked the sight and sound to 'Buses. United, and especially Frontier, fly a lot of those, too.

HOWWWWWOOOoOoOooooouuuuuu....

Pretty sure it's an acoustic effect from the engine,s and additionally as you know, doppler effect adds to the effect as the transmitter speeds past the receiver.

Hello all, after a long time of read-only, this topic finally made me write something on this board.

I have been hearing those noises for quite some time, visiting my parents' house in the approach of TXL.

The airplanes pass overhead at approx. 2000-3000ft. The sound can be heard quite often - maybe 5-8 times on some days.

Most noticeable about the sound is that it's usually the first thing you hear of the airplane. It can be heard on both CFM and IAE birds - therefore, I'd say it's definately not engine-related.

At this alt. both landing-lights and spoilers are usually where they are for final, so they're propably not a candidate either.
Somethimes, the pitch does not just go down (WHOOooop) but down-up (-ooooOOOP), so there has to be a parameter-variation that can not just be explained by the Doppler-Effect.

Possible contenders (apart from Spoilers) are:

1) Flaps. (usually don't go out-in)
2) Aerodynamic noise of other components on the airframe.

There's a paper by DLR (German Aerospace Agency) about noise-sources on airplanes. http://www.fv-leiserverkehr.de/pdf-d...t%20070123.pdf (in German)

Page 55 of the pdf / page 45 of the document will take you to the sound generated by the Tank Overpressure Relief Valves/ Openings.
The tones are in the region of 530Hz and 580Hz at over 110dB, which is quite consistant with the "blowing over a bottle" analogy.

This might be our patient here, with a change of AoA creating different noise-pitches. AoA-changes might be a result of flap-extension over here, so flap-travel might cause the noise on a secondary level.

The frequency of the noise-occurances (5-8 times a day at times) makes me discard the Spoilers as a source, as I have not that frequetly experienced the use of spoilers that low (though I have seen it happen once or twice).

First thing, no I am not a spotter, enthusiast etc etc... However this phenomenon has had me confused for many years. I have always thought it would be pointless to bring it up since I could never explain it properly.

What I can say is it has nothing to do with configuration changes, thrust changes or IAE,CFM,PW,RR

What I have noticed is it only happens in certain areas (for me in a small radius near where I live in London) and it seems to be only with smaller aircraft like the A320

My conclusions is it must be an acoustic phenomenon, that is dependent on the buildings around you. It's definitely not the aircraft itself but a sound reflecting in a bizarre way.

As I said, very hard to explain but I understand what the op is saying.

When you are a pax, and the aircraft descends through 3000 - 4000 (maybe 5?) thousand ish you can hear a tone change, which isn't linked to configuration, lights, flaps etc.
Something aerodynamic, and it is quite noticeable.

S-3 engine 'hoover' was both an increasing, or decreasing, noise depending upon power setting and amount of power increase or decrease and the rate of change.

Another interesting aerodynamic event is to listen to wingtip vortices. Different a/c have distinctly different vortices noises. Learned that playing golf at the golf course just south of KSEA. Got to the point that we'd try to guess the a/c type by the vortice noise in the trees.

It is definitely the deployment and retraction of the speedbrakes. 9 times out of 10 they are used totally unnecessarily by very inexperienced pilots (and some who should know better) unable to cope with energy management. Unfortunately easyjet does not covet experience, result : more noise and fuel wastage.

If I recall, inbounds to BRS are always held high due to the London TMA (Terminal Manoeuvring Area) so if you're landing "straight in" to runway 27 you always end up "hot and high" i.e. you've got a lot of energy to loose and not enough distance to do it without some help. Hence the use of speedbrakes. I'd put money on it that the noise you're hearing is indeed the speed brakes being deployed - you'll only hear it very briefly as the noise footprint passes you (like the sonic boom of Concorde :ok: - it moved continuously across the surface but you only heard it very briefly).

It is the engine thrust changing.

Think about it, it sounds like when an aircraft normally flies overhead, but sped up and with a 'whoosh' to it. If it's what I'm thinking of, the first second or so is VERY abrupt and breaks the silence nicely!

It is the changing engine thrust compounding the doppler effect which makes that cool sound and requires a specific change of power setting, altitude from the observer, and relative wind for it to be heard.

People here who are doubting this are probably thinking of the wrong sound. Or I am...

Well I have been on dozens of 320's (pax), never heard anything out of the commonplace, and have seen speed brakes deployed in descent (sitting by the wing) and again don't recall anything (and I am curious about these things so would have noticed).

I do hope the following is true..

Usually around that point we are trying to empty the toilets

which is nicely symmetric as just about that point I am trying to fill them.