Unusual ground noise following A320

[algis]

Hi,

The following is a consistent noise that I hear from Jetstar (Australian domestic/international carrier) A320's approaching to land at Sydney airport.

Practically any Jetstar A320 (and possibly all other A320's) coming in to land at a height of about 500m is trailed by an unusual ground noise. The ground noise is the sound of a jet/vortex that trailing the plan some 20 - 30 seconds after it has passed. When I first heard it I thought it was a high speed fighter jet flying overhead, although it is never that loud. The noise seems to be greater in cloudy weather.

I have tried to look for an explanation on this one on the net but with luck. Anyone know what this noise is and why its only from the A320's?

[HEATHROW DIRECTOR]

Used to hear something like that from 757s.. Soon after they passed overhead around 200ft on final approach a sound like a whiplash would be heard as the vortex hit the ground. Strangely, I never noticed it with heavy jets. I'm quite interested that the effect could be heard when the aircraft was at 500m (1600 ft..ish) as I am not aware that ATC provides wake turbulence procedures to aircraft which are vertically separated..

[JEM60]

HD Whilst lying on a sun lounger very close to Fuertaventura airport, it always amused me when I saw a 757 coming in. The wake vortex was, of course, guaranteed, and it was always amusing to watch everyones head come up after half a minute or so, as this strange noise washed its way around the swimming pool area.
I enlightened several people near me of it's origin, but they mostly disbelieved it, until such time as I pointed the next one on the approach, and, sure enough.........................
I think I am right in saying that the 757 was treated for seperation purposes as a 'heavy'
and that the vortex mainly originated from it's large flap area. Regards.

[treadigraph]

Think you are right about the 757 JEM60.

About thirty years ago I attended the BAe Families Day at Dunsfold (not-that-smallish stray boys on bicycles were admitted, whether via a hole in the hedge or a more official entrance I recall not).

Anyhows, a certain Stefan Karwowski was in the hot seat of Spencer Flack's Hunter; he wound up a sizzling display with very fast banked run in from slightly behind crowd right, just clipping the corner of the crowd line where I was on pole position to cycle round to the production hangars for a quick tour before skedaddling back to school in time for high tea... Stefan, being Stefan, was low... very low... and the aural boxing of the ears that slightly trailed the Hunter was rapidly followed by a considerably more solid punch of air as the vortices came to roost at ground level.

Closest I've ever been to a fast jet at speed and the only time I've encountered vortices.

I don't know if the CAA had a word with him afterwards; the next time I saw him, he was heading straight up in a half cuban from take off, mounted in Stephen Grey's Bearcat at Biggin Hill - his second flight on type.

[mickjoebill]

For those musically inclined take a trip to Hounslow and loiter in Waye Avenue, in line with the approach to Heathrow 27R.

Stand directly under the telephone pole, half way down the street and listen to the telephone line "strings" play the tune from the wake of the heavies.


Mickjoebill

[algis]

I've been encountering this noise from about 7km north of Sydney Airport and so I'm guessing the altitude is some 500m (engine noise follows after perhaps just less than 2 seconds from when aircraft are directly overhead)... I could be wrong.

It has been a long time since I last saw a 757 here in Sydney.

Thanks for letting me know your thoughts.

[JEM60]

Aaaaahhhhhh Stefan Karwoski. First time I encountered him was West Malling, coming unannounced from behind the crowd and very slightly above it in the glorious Bearcat. How sad that he lost his life in a Pitts that refused to recover from a spin!.Treadi, I think you and I appreciate the same things!.

[D120A]

The Lightning had particularly strong wingtip vortices when pulling 'g'. When a returning four-ship did a low run-and-break over Binbrook on day with a light breeze, the 30 seconds or so of quiet as the aircraft disappeared down-wind to land were often punctuated by the whistling and thumping of what must have been 8 vortices as they reached the ground, bounced off the hangar walls etc. On a calm evening with no other noise about from vehicles, ground equipment etc., the effect was as eerie as it was interesting.

[ground_star]

You get a similar noise following the 738s here at BHD - quite eerie sometimes - but somehow enjoyable

[Grifmeister]

I live 3km from SYD directly under the flight path. We regularly hear very similar sounds described above about 20-30 seconds after an aircraft has passed on final approach. It seems the smaller planes have a larger effect but particularly Virgin-Blue 738s where we hear a sound like the plane is flying overhead again, followed by weird whirling whistling sounds and sometimes a sound of a cracking whip.
Question is does these aircraft wake or vortices somehow descend as they seem to travel downwards and impact with the ground. Also I assume the bent up wing tip of the 738 is somehow related to increasing the affect. Larger 767s have a lesser effect and 747s and 380s none (although I will look out for these).

Thanks

[JEM60]

Grifmeister. Yes, they sink and drift with the wind. If operating a light aircraft from an airport which has jet aircraft, it is important to note their lift-off/landing point in respect of where you will be in respect of their wake turbulence. You may well get a cautionary call from ATC to be wary!!. [Good practice from ATC!!]

[nojwod]

Best i ever heard was a BAE146 coming into Canberra on a cold day, sounded like a continuous whip crack hitting the ground 10 metres behind me... once heard never forgotten

[Mike X]

Yup. I live under the flight path in Cape Town (base and 30*). Heard it first a couple of years ago, mostly 738's. Can't comment on the heavies. 99% of them come in straight.

The sound reminds me of a town in the western movies with the wind blowing and tumbleweeds rolling around. Must say, it is eerie.

[beamender99]

I lived at Hhounslow near the OM to Heathrow and the sound was a regular feature.
I left there 30+ years ago so it is hardly a new event.
I seem to recall that Vanguards were the most consiistent performers.