4 miles here, 5 miles there - Wake turbulence spacing in different countries

[Jerricho]

A little instance last night at work where a 757 decided to try and prove it can still fly while flying slower than the cars on the highway below.....with an Airbus on the visual behind got me thinking about the difference in wake turbulence separation requirements in different countries.

Here in Canada, A320 behind 757 requires 5 miles. Over in the UK, 4 miles. Here, PA31 behind 747, 6 miles. Uk requirement, 8 miles. Same PA31 behind A320 in Canada, 4 miles. UK requirements, 6 miles. And this is all before we even get into the "SMALL" category ;)

I find the differences a little amusing, tis all.

[cossack]

Mr J, the long winter nights must just fly by...

I agree though, it is odd. Maybe the air in different parts of the world causes differences in wake turbulence dissipation.
Whenever we in the tower are about to receive an aircraft with less than the required spacing, the second aircraft miraculously becomes "visual" and all is well again! C208 2 miles behind a heavy, issued a cautionary but still flies on or even below the glide.:ugh: :confused:

[Gonzo]

You sure are a bundle of laughs, Jer! :p

[Jerricho]

Whaaaat? What I say?

[Gonzo]

Ironic* reference to your flagrant use of the word 'amusing'.

*http://en.wikipedia.org/wiki/Irony

[despot]

Wtb Icao


..

[Jerricho]

Well, we are not amused now.

;)


Hey, back to the thread..............

[Gonzo]

Yes, back to the thread. Of course, there are differences within nations..... Heavy followed by a Light at Heathrow and other major airports is 7 miles, but elsewhere it's 8 miles.

[BOK2GO]

Approach spacing in SA is 8nm behind a heavy and 5 miles behind a medium. Yet a tower controller can squeeze in a VFR trainer 2 miles behind the heavy. Go figure.
I've always wondered if our heavies are heavier than yours....?:confused:

[KiloKilo]

How I love ACC or UAC for this it is 5NM all the time.

(Just don't dump fuel!! Then it is 50NM!!)

[judge11]

Wake vortices can kill, I and every pilot knows that but....it strikes me, as an airframe operator, that the ATC world does exercise its collective angst and concern about vortex spacing more than crew. I recall reading that there's a review on spacing going on at the moment which might come up with more realistic and practical spacing.

[OscarTango]

How I love ACC or UAC for this it is 5NM all the time.
(Just don't dump fuel!! Then it is 50NM!!)

Hate to break it to you, Rob, but Light behind Heavy is still 6 NM, even in Upper Airspace ( at least in the DecoSector :E ). Oh, Mediums don't always like to go 5 NM ( 4.8 in your case ) behind a Heavy either...

:ouch: Ok, I'll shut up now...

:} :} :}

[Married a Canadian]

BOK2GO

"VFR 2 miles behind heavy"

If the pilot stays high and lands long he can avoid the wake of the guy in front. So I've been told by a couple of light aircraft pilot chums anyway.

[flybymike]

BOK2GO
"VFR 2 miles behind heavy"
If the pilot stays high and lands long he can avoid the wake of the guy in front. So I've been told by a couple of light aircraft pilot chums anyway.

Living dangerously if you ask me...

[bekolblockage]

Just want to drag this one to the top again and ask for more info from ATCOs in different parts.
How does your ANSP treat the application of the laid down wake turbulence minima? To simplify things a bit, I'm talking specifically about final spacing in IMC conditions in a radar environment.
How rigidly must it be applied? i.e. is it as strict as radar sep or are you allowed some leeway? If so, what is the a mandatory cutoff? 1/2 mile under? No limit as long as you pass traffic and the pilot is happy to continue? What rationale is used to justify such a reduction?
Look forward to your responses.

[KiloKilo]

Upper Area all is 5NM except Heavy behind a Heavy then it is 6NM. However the seperation minima remains 5NM. Mind you sometimes had complaints about wake turbulence when trailing behind as much as +/- 12NM.

[Jerricho]

How rigidly must it be applied? i.e. is it as strict as radar sep or are you allowed some leeway?

Wake turbulence separation are separation standards that are outlined in various Civil Aviation Regulations and Manuals of operation for Air Traffic Services (Air Traffic Bibles if you will). They are not open to interpretation. The is no rationale to reduce the standard.

[bekolblockage]

Jerricho
Thanks for the reply.
OK, that sounds like a nice "official" line but at the operational level, what does your Check controller/Stream Manager/Team Leader expect you to do if , for example, the separation between a Heavy and a following Medium erodes to 4.8 NM on late final in IMC? Are you obliged to send the Medium around? How rigidly is that policed in your organization?

[bekolblockage]

P.S. Jerricho. I gather from other posts that you are a former UK controller and would therefore be aware of NATS policy regarding the application of the standard. Its not quite as clear-cut as your last post wold indicate.

[Quokka]

KiloKilo,

I had the same experience on shift a few years ago. A Medium turbo-prop 18NM behind a B767 on a high speed descent through his level. The turbo-prop reported encountering "Severe Wake Turbulence" and ever since then I've past a caution whenever I thought that a smaller aircraft was going to transit the wake turbulence of a heavy, even if the distance between the aircraft was in excess of the Wake Turbulence Separation Standard behind.

Interesting that on one occasion when I did this, one of my colleagues turned to me and said... "you don't know your Wake Turbulence Standards" because I'd chosen to pass a caution when the distance between the aircraft was in excess of the Wake Turbulence Standard in MATS.

I thought we were in the business of saving people's lives, regardless, but not in spite of, what is written in the books.

[Jerricho]

You are correct mate regarding being ex-UK. And the grey matter pertaining to some of the policies of my previous employer are a little on the hazy side.

Here in Canada, the Wake Turbulence standards are in black and white in the CARs. The reason I say black and white, in this now wonderful lawyer filled world we now live, I would hate to be standing next to someone in a court of law who had a nasty due to wake turbulence and you have no defence if you didn't have the standard.

To me, asking a pilot "are you happy to continue" means you're not.........why would that be?

[Jerricho]

Bekolblockage, I've been having a bit of a hunt around UK docs, and am a bit of a loss regarding your "NATS policy". Has there been a change sine AIC 17/1999 (that's the one I remember)?

[bekolblockage]

To me, asking a pilot "are you happy to continue" means you're not.........why would that be?
I agree with you on that Jerricho.
Not sure how "official" the policy is at Heathrow, but from this:
http://wwwe.onecert.fr/projets/WakeNet2-Europe/fichiers/pastEvents2005/bretigny-november/Paul_Johnson.pdf
comes this:
"•Wake Vortex Separation applied to 4DME from
touchdown.
•When the lead aircraft is inside 4DME and a reduction
of ½ mile or more in the required wake vortex separation
occurs, the pilot of the following aircraft must be
informed."
... meaning no need to say or do anything down to 1/2 mile below the standard?
Not saying I agree with it, just seems there's some fairly liberal interpretations of Doc 4444 out there.
Also seems to me the last 4NM is when you DO need it, as the chance of a recovery from a major upset at low altitude/low control effectiveness is fairly unlikely.

[bluerider777]

Just for the record in dunnunder:

L following M 5nm (except light medium then nil)
M following H 5nm
L following H 6nm

A380 lots - hopefully under review
special standards for 757 (meduim when following, heavy when leading)

Bust any of these standards and you are stood down pending investigation.

Interesting how different they all are! I thought we were pretty well ICAO standard...

Blue:hmm:

[bekolblockage]

bluerider777
Thanks for that. Our sep standards are the same here as Oz, including H-H 4NM.
I recall the change in attitude to WT in Melbourne in the mid 90's when it went from "do your best to get it" to " its non-negotiable". I remember several instances when the Tower started sending people around if a/c were handed off without the required WT sep, much to the chagrin of the APP controller.
It all seems logical of course, but its interesting to see how busy airports have interpreted the rules on a "needs must" basis. I'm sure Heathrow's capacity would fall way short of demand if controllers had to start applying a buffer.
Any other places out there that allow some "infringement" of the sep standards?
P.S. Out of around 900 movements a day here, more than 600 are Heavy. Light = zero!

[Gonzo]

The 'grey area' is due to the differing speeds that aircraft fly after 4DME. We cannot legislate for that, so cannot guarantee separation.

[bekolblockage]

Just playing Devil's Advocate Gonzo.
Presumably you guarantee radar separation in IMC even though there is compression inside 4NM, so what is the difference?

[throw a dyce]

Heathrow have a version on the UK system,with slight differences from what we use up north within Nats.For example Light following a Heavy in the UK Mats part1 is 8 miles.At LL it's 7.Light following a lower medium would be 6miles.At LL it's 5.
I suppose they could argue that they are very busy,and it's as near to ICAO standard that they can lose a mile.If I put a light 5miles behind a lower medium,it could well cause problems.LL it's OK.
With helis such as the AS332 (Small) and say a Saab 340 behind(Light) the requirement is 4 miles.With the speed differential,especially if the heli want 80kts inside 4 miles,then we always go for the buffer.Aim is to get 4miles when the heli is at touchdown.We don't have the 1/2 mile below standard at all.

[Jerricho]

You can guarantee the separation Gonze me old buddy.......unfortunately it means having your wake turb at 4 miles requires MORE further out. Bye bye landing rate.