In other news, wake turbulence liberates tile(s); car damaged, expert called in

[JamesT73J]

http://www.thisissouthampton.co.uk/hampshire/southampton/news/SOTON_NEWS_NEWS0.html

This made the local paper today. I hadn't heard of wake turbulence causing problems for houses before, is this possible or is this slightly exciteable reportage?

[Notso Fantastic]

It can happen and is not that rare. But Southampton doesn't get the heavy stuff- I should think the odd 757 is the biggest. Tiles do fall off roofs- a near neighbour had one dislodge and fall 3 floors to hit her soft-top Jaguar (on a not soft bit). We are near no airports. But if a heavy was on a low approach, then maybe the vortex would come to the surface.

[Basil]

Strange that this should come up (as the actress said to the bishop) but in 40 years in the business I've only experienced it once and that was just a couple of months ago, in the evening, at the poolside of a US airport hotel.
An aircraft had passed close to overhead and then we heard a roaring wind noise followed by trees being shaken and palm leaves blown about. We were so shaken that we had to have another beer. ;)
I guess that the surprising thing is that it doesn't happen more often.

[eal401]

Bit of a non-story to me.

Should have read:

"House and car damaged, aircraft blamed, airport rectified damage before proof it was aircraft's fault."

[sedburgh]

I live about a mile further from the airport than the site of this incident, about 100 m N of the normal approach, and I regularly hear vortices from 146s and see the effect on the trees surrounding my garden. Other types, including 737/757, do not seem to be so noticable. I heard the lady in question being interviewed on Radio Solent yesterday and she described a scheme that the airport had put together to investigate and compensate people for this sort of incident.

[Mr Chips]

I hadn't heard of wake turbulence causing problems for houses before, is this possible or is this slightly exciteable reportage?
Oh trust me, there is a very real phenomenon, especially in the LHR area. Heathrow Airport Limited (HAL) have had a scheme in place for years to repair roof damage. Tiles can be torn off a roof by aircraft votices, but nobody really understands how or why. I used to live around 4 miles out 27R and our neighbours house lost tiles when ours, a mere 5 feet or so away didn't...

HAL have paid to totally re-rrof a huge number of houses in the area with a different tile or fixing to prevent further damage...

Chips

[Bystander]

As you pass along Ringway Road to the immediate Northeast of the 24R threshold at Manchester, you will see more than a dozen homes with partially or fully re-tiled roofs.
An ex-colleague of mine had a relative living there for many years and she said the worst culprits were Concorde (a rare visitor and maybe the vibration caused by re-heated engines caused the problems) and PIA 747s on what did always seem to be very long take off runs! :-)

[Notso Fantastic]

Vortices are horizontal mini-whirlwinds trailing off the wingtips. They descend slowly (I think about 600\'/min) to hit the ground if not blown apart by a reasonable wind. Then they will obviously roll over the ground dissipating rapidly. Being a rotating phenomena, the pressure will be lower in the vortex, which when strongest is at its smallest. Hence roof tiles could be dislodged by a combination of low pressure and wind close to other areas unaffected. They stop the moment the aeroplane touches down and unloads the wing. Concorde was a powerful vortex generator because of the large, heavily loaded delta wing.
I would think a 146 might give a sparrow a shock, but roof tiles? Maybe the lady\'s roof needs replacing! I would bet the tiles were lying loose on the roof already! \'Southampton Airports fault\'? Naah!

[Avman]

This was at one time (before they were banned) a regular event in Ostend with departing fully-laden IL-76s.

[broadreach]

A few things come to mind.

I haven't much sympathy for people who decide to live near the threshold and then complain about the inconvenience so the tone of the airport rep's apology for the damage grates somewhat.

Always wondered how accurate that lunatic stunt in "Pushing Tin", lying down at the end of the runway while a 747 lands, was. And what's it like on the beach at St Maarten?

Where I live I get a good view of 737s and 319s landing at SDU from the Sugarloaf end. On a calm day and if the aircraft is slightly low it will leave a distinct ruffle on the water, which I've always attributed to the blast from the engines. On one occasion I thought a 737 was going to wet its feet half a mile from the threshold; the blast as he powered out of that raised two small roostertails.

[fritzi]

Ehh, the new title of the article is TWO DIE AT HOTEL.

Seems like they changed the news page... :*

[Mr Chips]

Broadreach what point are you trying to make?

Accident happened, attributable to aircraft, airport apologised. There is no slagging of the airport in the article, just an annoyance that this could have caused more serious injury, which is true. I have been around when this kind of thing happens and it is very frightening. You have no idea how long these people have lived near the airport, how big/busy it was whan they moved in etc...

eal401 said
Bit of a non-story to me.
I agree!

Notso fantastic
Hence roof tiles could be dislodged by a combination of low pressure and wind close to other areas unaffected.
Trust me - they can be dislodged by vortices, and are. Ask anyone in Hounslow, anyone at Heathrow Airport Ltd or anyone at Richardson Roofing who have spent the last three or more years on this project...

Chips

[BigHitDH]

Always wondered how accurate that lunatic stunt in "Pushing Tin", lying down at the end of the runway while a 747 lands, was. And what's it like on the beach at St Maarten?

It's crap, although I have personally been "dislodged" by a 752, no, not sucked up into the air, but almost knocked over!

The figure of 600fpm for a vortex's decent seems about right. The worst ones always seem to stream from the outboard edge of the trailing edge flaps. If it's really humid and you can see the condensation in the low pressure region, you can watch them strike the ground. They don't seem to spread out (span-wise) much at all, but grow into fairly large "cones".

You certainly know when one touches down near you - a tearing sound followed by severe buffeting - make sure you stand with your legs apart, or you will fall over. :\

[Lu Zuckerman]

An Air Force B-36 landed and was in the process of shutting down on the hard stand when an Air Force PBY landed (some fifteen minutes after the B-36 touched down). The wake turbulence was still quite pronounced and it flipped the PBY on its' back killing the entire crew in the process.

:E :E

[Notso Fantastic]

Lu. Approach vortices are of very short duration. If that was the case, no light aircraft could follow a heavy into anywhere for long periods. When the vortex rolls down, it dissipates quite rapidly. Cruise vortices can last for a minute or two. Following one about 10 miles ahead and 1000' above, we kept running into its vortex, but 15 minutes? Too long.

[Compass Call]

Notso Fantastic

Two posts without a tirade!!!!!!!!!!!!

What ails you man?? Surely you must be under the weather :E :E :E


CC

[BigHitDH]

Oh joy - marshmellows at the ready guys - let the flames commence!

[Notso Fantastic]

Good Heavens you're right! I think it must be the hay fever- seems to be bad this year. Rest assured normal service will be resumed as soon as possible- just carry on without me.

[broadreach]

Chips,

I wasn't trying to make a point at all. The newspaper article's factual, no problem with that. Non-story. And I take your point re how frightening it can be. But I think I did say the little sympathy was for people who decide to live near the threshold but I do also understand there were a few there before the threshold existed.

What niggles me a bit, really, is the apologetic tone the airport reps have to take. Ok, call it conciliatory. But contacting the aircraft manufacturer, a promise attributed to the rep in the article? Come on, please. Just seems a bit groveling.

Let's not let this thread descend into a pro/con airport noise/annoyance issue. The main subject, i.e. effect of vortices close to the ground, is interesting in itself.

So I have a question. NSF, assuming still air, at how low an altitude would a heavy aircraft have to pass over a house to dislodge rooftiles? And am I right in assuming that as the cone diameter increases, the speed of the vortex decreases?

[Yankee_Doodle_Floppy_Disk]

I seem to recall a bit of "kerfuffle" about the wake-turbulence behind a DC3 at NZAR a few years back...

Maybe hectorus rex could tell us about that... :p

[ShyTorque]

I saw quite a surprising demo of this at Old Warden (Shuttleworth Collection) just a couple of weeks back.

As part of a "Flying Evening" they had a balloon bursting event. Small helium balloons were released into the path of light aircraft, including a Miles Magister, which came past at about 150 feet. The Magister pilot missed a rising balloon which got entrained in the slipstream vortex. The vortex caused the balloon to rotate very rapidly, around a radius of about two feet. It pulled it all the way to the ground.

[HectorusRex]

Y_D_F_D possibly needs to supply more detail as the grey matter is getting quite congealed these days.
Was I exceeding Vne on short finals, or did I infringe the airspace around an orange house on the hill on approach to R03?
=^.*.^=

[GOLF-INDIA BRAVO]

Sitting down by the lagoon at Kerkira(Corfu) whenever a B757 landed you could always see the water being disturbed as it left
large vortix trails and you could hear it as a swishing sound, very strange but impressive

Golf India Bravo

[Notso Fantastic]

Broadreach- look at it like this. Take cross section areas of the vortex a little behind the aeroplane, and say a kilometer and compare. The first will be narrow and rotating very rapidly. The second will be wider and rotating far slower. There will be a slight loss of energy due to friction with the surrounding air. If you remember the ballet dancer theory, the rotational velocity will be reduced on the second, so as the vortex expands, it loses speed. Why does it expand? Haven't a clue! Sucking in free air?

[broadreach]

NSF, thanks. As to why the vortex expands, cd it be centrifugal force.

[ettore]

Back to the topic, Zurich "Unique" Airport is spending millions of Swiss Francs to clip tiles on the roof of houses standing under the newly opened southern airpath to the airport.

The airport is even diverting funds from an anti-noise fund to do so. I guess that if it does so, it means there is a real problem with turbulences on the southern approach.

[blue belly]

yes houses around zurich airport have their special due to the problems caused by aircraft... it's a well known fact around there I heard!

[PaperTiger]

Probably been posted before but have a look at the CX 747 here (http://www.aviationpics.de/pretty/pretty.htm) (at the bottom of the page). Loose tiles would be fair game, I'd say.

And yes, Maho Beach (SXM) is great entertainment watching the tourists watching the planes. Most learn quickly that a departing heavy will blow their towels, belongings and even small pets into the sea. Takes them a bit longer to understand WIHIH after a 757 lands ;) .
*Edited to add video link http://www.storeitonline.nl/funny/reality/movies/af747-depart-09.mpg :D :D :D

[Yankee_Doodle_Floppy_Disk]

hectorus rex

supply more detail as the grey matter is getting quite congealed these days
:rolleyes:

You were observed (through the smoke haze at Warbirds) on at least one occasion to pause between "Rouble Dum"s to debate the merit/futility of providing wake turbulence separation behind the "Dak" with a certain Senior ATCO.

Many hours later an agreement was reached...................



................ to disagree.

:hmm:

[411A]

Not many paid a whole lot of attention to wake turbulence until many years ago a DC9 (crew trainer) was turned upside down by a previously landing DC10 at the old Greater Southwest airport in Fort Worth, Texas.
Fatal to all on the DC9.:(

As for flying rather low and damaging roof tiles, some years ago a TriStar operated by AirLanka, during crew training, was completing circling approaches at the old Colombo airport, and blew the roof completely off a house.
Now for those that have actually been to SriLanka, will realize that houses there can be rather ah...flimsy.:ooh:

[HectorusRex]

Thanks for the memory jog, Y_D_F_D.

It surely was needed as I have neither smoked nor Rouble Dum'ed for nearly 10 years:ok:

Not in jest wake turbulence can really spoil one's day in the wrong circumstances.

In conclusion, was I for or against, or neither?

[currawong]

Believe it.

Depends a lot on the stability of the atmosphere at the time as to how fast they dissapate. Presence of an inversion may be a factor, such as early morning.

Fly across your own, it is like a speed bump.

Fly along your own in ground effect and you will experience sudden uncommanded roll.

Seem worse if the aircraft is dirty, my own worst experience involved running into one where the previous spray run involved a sudden/steep pull up with flap. So it persisted at least long enough to get the aircraft back to nearly the same spot.

Can be quite embarrasing to hit one approaching an overhead obstacle...

Nothing theoretical here - only what I have seen myself.

[Yankee_Doodle_Floppy_Disk]

HectorusRex

was I for or against, or neither?

You were most indignant that your precious DC3 was accused of producing wake turbulence and quite insistent that said wake turbulence was not of any great consequence to other traffic.

I think the Dak had been doing circuits on a Sunday afternoon and the Wake turbulence separation of 2 to 3 minutes was creating huge delays to those who didn't know they could ask for their own separation.

As an aside here, some pilots don't seem to realise that the wake turbulence delay to a subsequent departing aircraft is 1 minute longer from an inset position than from the full length holding point, therefore, it is sometimes quicker to taxi further when wake turbulence is a factor.
:)

I have neither smoked nor Rouble Dum'ed for nearly 10 years

Just as well you've quit. Look what they've done to your memory. :p

[edited for typos]

[HectorusRex]

Perhaps if that had been explained initially, Y_D_F_D there would have been no need to resort to emphasis.

IF I recall it correctly the DC-3 was accused of delaying the departure of waiting aircraft because of wake turbulence separations being applied, when the said DC-3 was making a full stop landing?

Perhaps you can convince me and others, that wake turbulence, in the form of wing tip vortices, does not cease on touch down?

I have always been well aware of the effects of wake turbulence on other aircraft, so I doubt if I was making any such assertion.

The effect of wake turbulence was brought home to me very early on when I had the misfortune when solo flying a "Devon" and encountered the wake of a Vampire ahead which had not made a normal power-off approach, and when the jet wash hit one wing the Devon nearly became inverted at a precariously low altitude.
The "Checkers Van" Controller got nearly as bad a fright as I did.

You are quite correct that the DC-3/C-47 was, and still is, a most precious aircraft, and probably no more than in those days being commemorated at Normandy this weekend.:ok:

[Yankee_Doodle_Floppy_Disk]

Funny how the louder the voices got, the harder it was to hear what was being said.
Perhaps you can convince me and others, that wake turbulence, in the form of wing tip vortices, does not cease on touch down?
The aircraft might stop creating a wake at touchdown, but the trail behind it doesn't instantly dissolve. My understanding is that the wake turbulence is at its greatest immediately prior to touchdown. So, if the Dak touched down by the Waitemata taxiway and vacated at the end, it is conceivable that a C172 departing from full length could get airborne into what was left of the Wake Turbulence. Of course, if the C172 held it on the runway until the Waitemata taxiway, he would be clear of the risk. That would be his decision to make.

The standards required to be applied can be downloaded at:
NZAIP - Wake Turbulence (http://www.aip.net.nz/pdf/ad_1.6.pdf)

It's a PDF file
Between Arriving and Departing Flights
1.4.4 The minimum time separations applied between arriving and
departing aircraft, if the flight path of the following aircraft will cross the
projected flight path of the leading aircraft (e.g. when an arriving aircraft is
operating onto a runway with a reduced landing threshold) are provided in
Table AD 1.6-4.

Sourced from www.aip.net.nz

The table gives the example of a MEDIUM ARRIVAL followed by a LIGHT DEPARTURE and the required separation is 2 minutes.

Then further on:
1.5.3 Notwithstanding the wake turbulence separation standards
previously outlined, if pilots consider that the effect of wake turbulence can
be nullified by ensuring that flight profiles do not cross, they may request
and be granted exemption from these separations. ATC will advise the
category or type of the other aircraft where that aircraft is a HEAVY weight
category or is a B757 aircraft.
Sourced from www.aip.net.nz

This was probably pointed out to you at the time. Like many things, the pilot is entitled to decide that the situation is safe, the Controller mustn't assume that it is.

Now, here's a question to get you thinking. Does all the Wake Turbulence cease at the moment the mains are on the runway? Or does the tailwheel have to be on the ground as well?

[HectorusRex]

Thanks for all the chapter and verse, Y_D_F_D.

I'm not sure what the relevance of all this is, some nearly 10 years hence.

Strange as it may seem, Ardmore, still the busiest airport in NZ based on aircraft movements, manages to continue operating safely without the assistance of ATC.

In conclusion I understand that wing tip vortices cease with the unloading of the wings at touch down.
I do not think that the fact that an aircraft is a tricycle or tail wheel type makes any difference to this.:hmm:

[BOAC]

To be pedantic, vortex turbulence (which is what I think you are all talking about, not 'wake' which is behind every moving body at all times) is produced by a surface when that surface is producing lift. In the case of a tailwheeler, the wing is still at a positive incidence during the landing run, so there will be some (small) vortex generation along with some lift generation. With a nosewheeler, the roll-out incidence is minimal as is the vortex and lift.

[Yankee_Doodle_Floppy_Disk]

In the case of a tailwheeler, the wing is still at a positive incidence during the landing run, so there will be some (small) vortex generation along with some lift generation. With a nosewheeler, the roll-out incidence is minimal as is the vortex and lift.

I always thought that might be the case. I also wondered how much vortex was generated by the tail-plane.

Anyway, Bill, I knew you'd take the bait.;)

[broadreach]

Late-night rambling perhaps but I find it difficult to believe that any taildragger could generate vortices threatening to anything larger than an ultralight on. Speed surely has a bearing on it, i.e. the faster the speed the faster the vortices spin so the longer the cone.