EGLL vs EGSS

[N4641P]

As an active pilot flying both to Heathrow and Stansted on a regular basis I am wondering about the separation required for departure. Can anyone provide me info or a link to the UK separation rules as well as the rules used for avoiding wake turbulence? It seems I am waiting on the runway for take-off clearance a lot longer at Stansted than at Heathrow.

Secondly, does ATC consider two minutes timing from the time the preceding aircraft starts rolling or rotating?

Any usefull comments appreciated. Greetings from the mainland. :cool:

[Grasscutter]

The 2 minute vortex separation is taken from the time of rotate of the first aircraft to the time of rotate of the following aircraft. If you are in the following aircraft and it is a 2 minute vortex separation expect to be given takeoff clearance at about 70 -75 seconds after the first aicraft rotates, thus achieving a 2 minute vortex separation at the rotate point.

[Dan Dare]

Link to UK AIC Vortex Wake (http://www.ais.org.uk/uk_aip/pdf/aic/4P188.PDF)

I agree with grasscutter, except that at the busier SE airport the 120 seconds is not used. Take off clearance is given when the previous departure reaches 2 nm so that the flight paths are probably about 95 seconds apart, it is then up to the pilot to decide whether he values his life sufficient to delay departure or not (I don't know if anybody would admit this though)

As for separations not based on Vortex wake, then as the airport grows, these are gradually reduced and procedures put in place to cope. Heathrow has various departures where 1 minute can but used between sucessive aircraft (no, not 60 seconds, but clearing the following aircraft once the first is showing daylight beneath the wheels), Stansted doesn't. But when conditions permit, then reduced separation in the vicinity of the aerodrome (visual separation) can be used instead.

[Muppit]

Woh there Dan,

Vortex separation is 120 seconds!!! Regardless!

At the two busy SE airports I've worked at, vortex is taken very seriously.

Professionals tend to be picky like that!:mad:

The two mile launch you refer too is to separate aircraft on the same routing....for aircraft of the same vortex or higher, and of the same speed. That rule of thumb provides lateral separation at the end of the SID, it is not sufficient to ensure vortex spacing!

Grasscutters rule on rotation to rotation is correct and has been the subject of much discussion on this BB (e.g when does the wing start to generate lift and therefore generate vortex?) and it is a technique taught at the College of ATC.

As for sitting on the threshold longer at STN than LHR, do STN have to request a release from radar before they can launch the departure, where LHR & LGW have free flow? (I'm sure someone from STN or Essex will reply sometime)

[HEATHROW DIRECTOR]

Dan.. at EGLL is obviously the busiest airport in the SE I'd be very glad to know where the "2nm" rule came from? VORTEX separation is based on time on departure, not distance as I'm sure my Heathrow colleagues will very quickly point out. Unless, of course, procedures have been changed during my six days off..

[N4641P]

Thanks much so far,

the problem I encounter when flying a somewhat underpowered turboprop is flying into the wake of a medium size aircraft which climbs quickly. The vortex then sinks and we end up in it. Highly uncomfortable.

Don't want to upset folks in the tower but don't want to have the aircraft taking a course of it's own either. A dilemma I guess.

Thanks for the link, at least I now have an official procedure to consult, because the rules seem to differ from the one's used on this side of the channel.

Happy landings (or take-offs for that matter)
:)

[Standard Speeds]

Whilst we're on this subject, what consideration do LL Deps give to a/c following the infamous A340 on the same route, same vortex cat?

The number of panicked 'phone calls fielded by those who look at their ATM oh so late and see the XXX A340 struggling out of 2k', doing 165kts and not having reached Bur (West) or turned for Kilba (east) as their next heavy on the same route trundles towards V1!

Now I realise there are pressures in the tower, but stopping the following a/c off at 2k' (outside CAS) is not really the answer! Well, it is as a last resort, but perhaps some extra seconds before clearing the following for take off - you know, for luck!?

I'm not having a pop (honestly) I just thought perhaps some LL ATCOs can put their side forward as there is never time (nor is it the place) to do so in the said panicked 'phone call!

Regards to all,
SS.

[ATCO Two]

Dan please do not comment emotively on subjects you are not directly involved in! Are you a Heathrow Tower Controller? Thought not! Vortex separation is a safety matter and is not taken lightly. 120 seconds vortex separation is applied - it is perfectly legitimate to take into account the take off roll which takes 40 - 50 seconds, as vortex is not produced until the nosewheel lifts off the ground. The two mile rule is, as has been stated a DEPARTURE separation - not a vortex separation and can only be applied between aircraft on diverging routes. In the USA they can apply five miles vortex separation on departure for vortex but not in the UK. Any departure separation based on time is only designed to achieve one aim - five miles separation on radar on the same route.

"Up to the pilot to decide whether he values his life sufficient to delay departure or not (I don't know if anybody would admit this though)" - just what are you implying here? An emotivre and unhelpful statement.
:mad:
Vortex spacings are minima - if a pilot wishes to delay departure because he feels that the vortex separation being applied is insufficient, he is within his rights to do so! (We prefer to be told if more than the UK standard of 1 minute for a Lower Medium behind a B757 is required so we can adjust the departure order if necessary).

Separations not based on vortex wake are NOT being reduced!!! The 2.5 nm spacing procedure is perfectly safe in the appropriate weather conditions, and merely caters for the situation we had in the past when aircraft initially 3nm apart reduced to 2.5 nm apart within 4 nm from touchdown, due to differing final approach speeds or different rates of speed reduction. All the Heathrow procedures are closely monitored by the Safety Regulation Group of the CAA. Are you suggesting that the CAA are approving unsafe practises? "Wheels up" take off clearances are perfectly safe - I have been using them for 25 years without a glitch. When both aircraft are the same weight category and their tracks diverge by 45 degrees or more there is absolutely no problem! If we waited for the full one or two minutes between departures the airport would grind to a halt and operations would be no safer than they are now. As Stansted develops and has freeflow departures, as will happen, I am sure that they will adopt similar procedures.

[ATCO Two]

Hi SS,

There is a recent Instruction that states that a full 120 seconds separation must be applied between an A340 and a following Heavy on the same route. Having said that, I am personally very mindful of the problem and sometimes use the goundspeed function of the ATM to check the A340 speed. If it is excessively slow I apply another minute separation for good measure. It happened last night actually between a VIR A340 and a SAA B744 on MID departures. VIR was showing 165kts and passing about 1800ft 3 nm South of the airport, therefore an extra minute was applied. But then I am an experienced radar controller. Maybe it is part of the legacy of having ADC only controllers that they do not so easily appreciate "catch up" situations

[Gonzo]

Regarding A340s being followed on departure.

I think most LL tower ATCOs appreciate the problems to be encountered with A340s, but there are some who don't. (Nice to see I'm not the only one who uses the groundspeed on the ATM!)

Another factor is perhaps the new blood coming validating not having a grounding in 'anorakism'?

Gonzo.

[Dan Dare]

Oops! Touched a raw nerve didn't I? No offence was intended, but I know for a FACT that 120s vortex separation was not rutinely used by Heathrow in the past, but exactly as I put it (if it has changed, then I stand corrected). It is very easy to get 120s between successive flight paths and I'm sure that clearances at Stansted are issued to achieve this. Why then does N4641P wait for a lot less time at Heathrow? Perhaps other Heathrow Tower controllers could comment?

Having experienced vortex wake from the cockpit at low level (from same category aircraft) I would never be tempted to squeeze the minima, but I know that it is done. The minima are enforced to save pilots from themselves as many of them are champing at the bit to go reguardless (hence "it is then up to the pilot to decide whether he values his life sufficient to delay departure"). The minima are also just that. They will not rule out the possibility of a vortex incident (see above), but lessen the likelyhood of it.

As for A340s, why aren't they put in a lower speed group to formalise things if they are such a problem for young ADC only controllers to grasp?

[120.4]

Dan Dare

For as long as I have been in ATC (21 years) 120 secs has been the standard. I am sure you wouldn't be suggesting that we have been routinely ignoring that, would you? No, I thought I mis-understood you.

Wake vortex is a killer and we mess with it at your peril.

Point 4
:)

[HEATHROW DIRECTOR]

Dan. I was a Tower controller at Heathrow for 23 years and have never seen any controller reduce VORTEX separation, even when pilots said "We're happy to go now" 20 seconds after a heavy departure - which I've heard many, many times... and they were the guys prepared to take the risks, NOT ATC.

There is a 2 minute departure (NOT VORTEX) separation between a/c on certain routes which can be reduced if we can maintain them in sight until the tracks diverge, or we can say "With the XXX traffic which is turning left/right in sight, cleared for take-off". This is what you might be thinking about.

I simply do not believe that anyone would break the VORTEX rules and I think you owe us all an explanation as to who you are. You're obviously not an ATCO and most definitely not a pilot with any reliable experience of Heathrow.

As for why Stansted take longer to clear a./ for take-off there could be several reasons. Some of their departures have to be cleared with "departure radar" before they can go whereas the majority of Heathrow deps are free-flow.

[ATCO Two]

Dan for Chrissakes!:mad: So you know for a "FACT" that 120 seconds was not used at Heathrow in the past do you? This is my 25th year at Heathrow and 2 minutes vortex separation has ALWAYS been used. If you read the AIC you posted you will see that the amount of time taken for the departure roll can quite legimately be factored into the two minutes. NOTHING has changed! The separation has been applied that way ever since I arrived at Heathrow.

Of course "it is very easy to get 120s between successive flight paths" and that is EXACTLY what happens! If we waited the full 120 seconds between successive departures we would be wasting 45-50 seconds per aircraft pair. Total that up during one day and that is a HUGE loss of capacity with no increase in safety. Pilots are NOT champing at the bit to depart; they are all too mindful of the dangers of vortex wake encounters exactly as we Controllers are.

You choose to ignore my point about safety regulation - if we were operating in a dangerous manner then SRG would soon intervene. We get VERY few, (in fact hardly any) vortex wake reports in an average week, so obviously we are applying the procedures correctly.

Of course you are touching a raw nerve, because you are questioning the professional integrity of Heathrow Controllers with no hard evidence to back it up!

Differing A340 departure speeds is a training issue. Different companies operate their A340s in different ways, therefore the suggestion that the type is placed in a different speed group would be nugatory.

[Only A Few More Seasons]

Here I go again!

Do any of you consider what the large fan engines are doing on T/O - probably far worse than any wide body wing vortex - Please try reading Chirps it is a real problem, 4 bloody great engines each moving 75 tonnes of air backwards up the railway bankment at EGKK it's not nice.

Please think of the Guy with the "Expect Late Landing Clearance"

You can always turn your air conditioning down!!

[hooplaa]

Head above the parapet - at Stansted it depends on what has happened ahead of your departure - are you taking a departure from an intersection following heavier full length departures, following a heavy both full length or flying a route which Stansted has to apply 3min dep separation ie DVR LAM or LYD following a DVR LAM or LYD off R05 or CPT following a CPT.
We operate to the same rules of separation as the 'big' movers do, but have local rules to also consider

[Captain Windsock]

120 secs is the standard vortex wake separation for aircraft following the same route. However 2mins is the standard for aircraft of the same category and this is designed to achieve 5nm separation for the first 25nm of flight. The A340 is just about the slowest jet off the blocks and the B757 about the fastest. If the tower controller applies 120 sec vortex wake separation they are achieving their immediate requirement but that 5nm separation will be out the window by Burnham. If any tower controller puts a B757 only 120secs behind a A340 they need their brains testing. Hopefully there are none of those reading this, but there are a few.

Question. Why isn't the A340 in a lower speed group? Sensible answers only.

[halo]

As mentioned by ATCO Two earlier on in this thread, the A340 doesn't need to be in a slower speed group. The speed differential between them comes solely from the way the airlines operate the aircraft and to what extent they derate the engines for departure. Any controller with any appreciation of aircraft performance will monitor the ground speed and rate of climb using the ATM so that we don't put something faster up his chuff. Only the other day I launched the Air Mauritius A340 on a Dover departure and had to wait almost 4 minutes before I could go with another southbound due to the poor aircraft performance and the strong headwind that he was encountering. The same principal applies to the BAe146... Compared to most jet aircraft it is slow on departure, and so we don't blatt another aircraft off as soon as its wheels leave the runway!

As for the wake vortex issue, I think you will find that all controllers give a full 120 seconds behind a heavy departure. Feel free to monitor the seconds that pass between the nosewheel lifting of the first aircraft and the nosewheel lifting of your aircraft.... Always 120 seconds!! If you want more, then ask!!! But please bear in mind that if we are operating single runway procedures or we are taking landing traffic on the departure runway then there may be something screaming in down the approach!