Minimum Separation on Approach at LHR

[shoey1976]

Hi all
I've learned that while the minimum separation of aircraft in UK airspace is usually 3nm, in the LHR area this changed not so long ago to 2.5nm. Why and when was this done, and is it wise? To increase / help maintain the present landing rate -- I read somewhere that typically LHR operates to 98.5% capacity (hence the nightmare scenarios we see on tv every time it's a bit foggy).
Any thoughts very welcome.
Best wishes
Ian Shoesmith
BBC News

[HEATHROW DIRECTOR]

The 2.5nm approach spacing at Heathrow (and elsewhere?) has been in use for many years. I retired nearly 6 years ago and it was in force long before that so it has probably been in force for 10 years? It may only be used under certain conditions and between particular types of aircraft and only on final approach. Not every flight is subject to 2.5nm spacing. The simple reason for it is to achieve greater runway utilisation.

[Dan Dare]

If on an average day LHR operates at 98.5% capacity, then a day with stronger than average wind will quickly create delays. An extra 10 mph headwind loses 10 miles of available approach spacing or about 3 landigs every hour - something like a 7% reduction in available landing capacity, with stronger winds being even worse. There is no spare capacity to absorb this, so it turns in to large for aircraft waiting to go to LHR and for those holding in the busy London skies wanting to land there. The reduction in arrival spacing can go some way to reducing this delay, but only under strict weather criteria which allow the following pilot to see what is 2.5 nm ahead of him. It is specified that there should be no increase in missed approaches as a result of the use of this procedure, so by implication it is only really used when ther is a bit of a headwind and it is not used to increase declared arrival capacity.

Other airports are also allowed to use the procedure, but it is usually less essential as they tend not to operate at full capacity and most other UK airports use the same runway for arrivals and departures so that inound spacing can be reduced from 6 to 5 miles still allowing a departure to take off in between.

Glad to see someone from the BBC taking an interest and not just making it up like many media types seem to.

[anotherthing]

Alt Flaps

I often despair of the inability of some journalists to get facts correct, or to even check those facts. Not just restricted to the journos writing the piece, but the sub editors as well.

To be fair to Ian, he is always upfront about who he is and what his intentions are. There are plenty 'professionals' on here who whinge about the professionalism of journalists, no doubt you are amongst this number.

Surely even you can see how contradictory it is to lambast the ethics of journalists who do not write factually (many lurk on PPRuNe pretending to be something they are not), yet give a journalist like Ian (who is trying to be upfront and honest) a hard time?

You can't have it both ways!

[Defruiter]

HD - I think you are refering to the 2.5nm spacing on final approach but Ian is talking about the 2.5nm separation (2.5nm radar separation within 20nm from touchdown)which I believe has not been in force as long.

[HEATHROW DIRECTOR]

Humble apologies then....

[Del Prado]

Why and when was this done, and is it wise?

Ian, which do you think is safer

a)3 miles and tangential tracks or even head on at a closing speed of up to 10 miles a minute,

or

b) 2.5 miles going the same direction at the same speed with a closing speed of 0?

[AltFlaps]

I'll try that again then ...

I posted earlier in response to Mr Shoesmith's post. It seems that I have brought the wrath of 'mod' down upon me, because my post was deleted.

This forum is for threads that specifically affect the working lives of professional pilots.

I took great issue with Mr Shoesmiths attempt to extract and publish the names of the crew directly after the BA 777 incidient last month.

He may be 'up front and honest :yuk:', but that doesn't alter the fact that had he succeeded, the lives of those pilots (and possibly their families) would have been made significantly more difficult in those first couple of days.

Now forgive me here, but I am a professional pilot, and I will continue to look out for my colleagues where I can ...

Moderator, is this post acceptable to you, or would you like me to start a seperate thread on the topic ?

[PPRuNe Radar]

This forum is for threads that specifically affect the working lives of professional pilots.

It's now in the ATC Forum, as separation standards are more of our domain.

We tolerate journos to some extent here, and even pilots :ok:

[Standard Noise]

shoey 1976 - journo or not, asked a perfectly reasonable question.

I took great issue with Mr Shoesmith's attempt to extract and publish the names of the crew directly after..........

I suppose you'll be blaming him for making them go to the Sunday papers to sell their stories when there were a few shekels in it, will you?

I am a professional pilot, and I will continue to look out for my colleagues where I can.

A professional pilot you may be, but the question wasn't one for which a professional pilot's opinion was sought since it's not a professional pilots job to provide separation.
As for your two colleagues, they seemed capable of handling much more than a journalists enquiry last month, both during the incident, and after it as well.
It's doubtful they need anyone's 'protection'.

As for the 2.5NM separation, sounds good. Wonder if we can get that into our MATS Pt2?:}

[Spitoon]

Been using it myself for years......just didn't realise it was official!

[Hotel Tango]

Been using it myself for years......just didn't realise it was official!


:ok::) Good one Spitoon

[ILS 119.5]

Talking about separations, how do you answer this. When I was a controller the MATS Pt 1 stated that for a light aircraft to follow a heavy aircraft on final approach the vortex spacing has to be 8 miles. However for an en route or intermediate approach a light can be 5 miles behind a heavy. Doesn't this contradict its self. How can you have 2 different rules.
Fly a lot into EGLL & EGKK now and the vortex spacings are not a problem, but again my question is how does the MATS Pt1 state different rules and EGLL have different rules.

[Spitoon]

Greater/stronger vortices are generated in landing configuration than in cruise config.

The variations from national procedures are described in the unit MATS Part 2 (and, in some cases, will be included in the AIP) and will be subject to approval by the regulator. Approval will only be given if a suitable safety case is produced. Well, that's the theory anyway.....

[Gonzo]

Before the change:

LL has a 3nm spacing requirement, which is the same as the minimum radar separation, which can decrease to 2.5nm when certain conditions (daylight only, and good weather conditions etc) exist.

After the change:

LL still has a 3nm spacing requirement, but now the minimum radar separation is 2.5nm on final approach, bringing LL into line with ICAO guidelines on radar separation on final approach.

[Del Prado]

why you bother with the extra 1/2 mile

At a rate of 40 movements per hour (arrival runway) the extra half mile equates to 20 extra miles or 6/7 extra movements per hour. It is worth it.

[Greg_ATCO]

I've got a question for you guys! Doesn't quite come under seperation but its the closest thread to it...B757 at FL 300.... Dash 8 at FL 290. The 757 is directly above the Dash 8. As you can see it is seperated by the required 1000 feet. What is wrong with this scenario? Question is open to everyone!!

[BOBBLEHAT]

Is it that the service ceiling on a Dash 8 Q 400 is 25000ft so your scenario is rather unlikely?

Can we get back to the thread?

[A good headin]

The Dash 8 crew therefore have nosebleeds at FL290!:}

That was easy....next!

[PPRuNe Radar]

Is the Dash-8 RVA ??

Thread drift ....

[Greg_ATCO]

Well yeah...the Dash 8 isn't RVSM approved..But I've asked a number of people the same question and Wake Vortex just kept coming up!?!We like thread drifts!!!!!!
Good heading, here's one for you...Who controls the tracks on the Eastern side of the Atlantic???

[shoey1976]

excuse my ignorance on this, but why is the limit set at 4nm for heavy immediately followed by heavy (or any other aircraft)? and are those limits ever broken?
thanks
Ian Shoesmith
BBC News

[Gonzo]

Aircraft create wake vortex from each wingtip.

The violence of this is dependent on the weight of the aircraft, so we provide more separation for a smaller aircraft following a larger one.

For example, at Heathrow, a 747 following a 747 would be 4 miles. A 737 following a 747 would be 5 miles. However, a 747 following behind a 737 does not require any vortex separation, because in that case the smaller aicraft is in front.

[Airbus Unplugged]

Dear Shoey,

Imagine firemen sliding down their pole. You jump onto the pole before the previous guy's reached the bottom, and you know you won't get off before the next man's bearing down on you from above.

Luckily the firemen are skilled acrobats, and we get it right most of the time:ok:

[Greg_ATCO]

Gonzo...I assume your comments are based on limits set for controlled airspace??

Because outside controlled airspace the distance between all aircrafts are 5nm right? Regardless of size and wake vortex?

Or...Do smaller aircrafts travelling behind bigger aircrafts (E.g. Dash 8 travelling behing a B757) have to have a bigger distance than 5nm in uncontrolled airspace??

[Dan Dare]

We don't use Ausy rules here in blighty - here's a simple table of the arrival spacings I have to apply

Leading.......Following.............Minimum Distance...Minimum Distance
Aircraft.......Aircraft................MATS 1.................London MATS 2

SUPER........SUPER...................4 miles
(A380)........HEAVY..................6 miles
.................MEDIUM................8 miles/3 minutes
.................SMALL..................8 miles/3 minutes
.................LIGHT.................10 miles/4 minutes
HEAVY........HEAVY..................4 miles.................4 miles
.................UPPER MEDIUM.......5 miles.................5 miles
.................MEDIUM................5 miles.................5 miles
.................SMALL..................6 miles................ 6 miles
.................LIGHT...................8 miles.................7 miles
UPPER.........UPPER MEDIUM.......4 miles.................3 miles
MEDIUM.......MEDIUM................4 miles.................4 miles
.................SMALL..................4 miles..................4 miles
.................LIGHT...................6 miles..................6 miles
MEDIUM......MEDIUM................3 miles...................N/R
.................SMALL..................4 miles..................3 miles
.................LIGHT...................6 miles..................5 miles
SMALL........MEDIUM................3 miles..................N/R
.................SMALL..................3 miles..................N/R
.................LIGHT...................4 miles..................3 miles
Upper medium = B757, DC8, B707, IL62 or VC10
N/R - Not required
UK categories by MTOW
Heavy 136000+ kg; Medium 40000-136000 kg; Small 17000-40000 kg; Light -1700kg.

Although these are minima for IFR final approach spacing it is recognised that as aircraft slow down durng the final stages of approach these minima will be slightly erroded so the spacing is normally applied until 4 nm final by use of rigid speed control.

I don't believe that stats are kept of the number of times less than minimum spacing is applied (doesn't happen very often) but pilots are always encouraged to report a vortex wake encounter in order that the phenomenon can be better understood. I'd probably have 2 pilots a year filing a vortex report and that would normally be when the minimum spacing has been applied. The minima are to reduce the likelyhood of a vortex encounter, they do not claim to erradicate all chance of an encounter.

VFR traffic is allowed to self position behind heavier aircraft. We use the phraseology "...caution vortex wake, the recommended spacing is x miles." and allow the pilot to use judgemet as to how much spacing to apply.

Remind me never to try to PPRuNe a table again:\

[BOBBLEHAT]

Greg ATCO,

I think your name may be misleading . . . . . (and not the Greg bit)

Aircraft outside controlled airspace are uncontrolled. . . . . they can fly 2cm away from each other if they want to.

[Spitoon]

BOBBLEHAT, I wonder if your stated profession may be misleading. ;)

In the UK we have some wonderful, if completely non-standard, services which provide 'control' and separation outside CAS. Granted, to most sane-minded controllers, and to ICAO, this is a peculiarity, and one which creates many problems, but it is a fact. As far as I am aware, with many years of working such an environment, wake vortex spacings should be applied to those aircraft if the circumstances meet the criteria specified in MATS Part 1. In reality, this will rarely happen but I think the wake vortex spacing rules still apply.

Sometimes I feel so proud to be British.

[BOBBLEHAT]

erm. . . we're not talking about ATSOCAS.

[Spitoon]

erm. . . we're not talking about ATSOCAS.Quite so. But you said 'Aircraft outside controlled airspace are uncontrolled. . . . . they can fly 2cm away from each other if they want to'.

I was simply pointing out that in the UK we can have aircraft outside CAS that are effectively receiving a service that is equivalent to control. And if two such aircraft get close enough together that wake turbulence spacing is an issue then, as far as I'm aware (and I haven't gone looking in the books so I stand to be corrected), WT spacing should be applied.

So yes, aircraft operating outside CAS and not receiving a RAS (or whatever it's called this week), can fly 2 cm away from each other. But if they are under a RAS then the controller should do the approprate thing wrt WT spacing if necessary.

[Greg_ATCO]

Spitoon - In the UK...when aircrafts are flying in uncontrolled Airspace...do they have to request the service from 'RAS' or is it mandatory?

[HEATHROW DIRECTOR]

Greg_ATCO.. Just curious, why do you use the term ATCO in your name when you obviously aren't??

[Greg_ATCO]

I just needed a username...i didn't create it to state my position, I wasn't pretending to be something I'm not, If I did I wouldn't be asking questions would I? I hadn't used the forum before so wasn't aware it was such an issue...and 'Greg'...was Taken, unfortunately! I hope I have put your mind at ease...I will change it!!

[HEATHROW DIRECTOR]

OK Greg.. Well from my point of view it did cause confusion. I wondered why an ATCO in the UK would ask such questions. My "name" comes from the fact that I used it as a radio callsign for most of my working life.

[Greg_ATCO]

Ok, well I'm sorry for the confusion...I have changed it to - Here2BroadenHorizon - Hopefully that doesn't cause confusion and will let you guys understand why I ask such questions, and just for the record, your question was a bit smart and patronising and I didn't appreciate it.