Near miss over East London [Archive]

slip and turn

16th Aug 2007, 17:18

Interesting view WaGA

As you will have gathered, I am not so confident of the routine nature of this one. Do remember that the LCY aircraft will have been airborne no more than about 30 seconds when this occurred. Also the LCY aircraft would have been in a right turn to the north and the Air Canada would almost be just completing a right turn south onto base.

Both we are told were changing level.

That's a hell of a lot of conflict resolution to expect from an automatic system which is trying to resolve closure rates which at first seem manageable and then both aircraft almost simultaneously actually turn towards each other!

Ever see the movie "Red October" ? What did Sean Connery remember about the closure rate resolution on the torpedo warhead after he turned at the last possible moment and faced it down head-on? Might be a bit cheesy, but you get my meaning.

Not sure how the accuracy of the original report is verified but if they really got "within 500 feet" per the report, then I am sure this one is being investigated.

LHR and LCY were using the same set up again this morning. It is probably the most common in daily use. Without the plates in front of me just now I am guessing, but that bit of sky just north of Canary Wharf where conflicts could occur in the overlapping STAR and SID might be as small as a cube with 2000 foot sides but usually when there's a LCY SID and LHR arrival converging, you see the Heathrow traffic either turned early nearer Tower Bridge or extended a bit downwind almost to overhead LCY 10 Threshold whilst the LCY traffic is obviously directed to keep its head down in the climb.

When the sky is free of LHR traffic, many of those RJs skyrocket out of City and in one sweeping turn exit to the north and/or then round to the east quite literally like bats out of hell. They often remind me of the Lightnings and Canberras skimming the horizons of my childhood!

Snapshots of the cubic mile centred on that overlap cube when both types of traffic are in view (as they frequently are at peak periods) would yield shots of a myriad of different dances indeed !

My point is that this tiny corner of London's airspace is becoming ever more concentrated, it is where the converging aircraft' crews have their hands full during take-off and approach, and it is the classic opposite track climb and descent scenario. Added to that is the wildcard for the LHR traffic is that LCY aircraft likely to launch off 28 out of LCY mightn't even be on the menu when you are about to turn towards Canary Wharf, but they very soon are up and at you by the time you are coming out of the turn unless the controllers and LCY pilots are right on the ball. The odds of a potential rapid onset conflict during normal operations are then surely as great as can be found anywhere ?

A possibly useful TCAS overview is at http://techaidproducts.com/PDFs/TCASUncovered.pdf

Mrs-rodge-bless-her

16th Aug 2007, 17:18

LeFreak : 146 and high climb rate in the same sentence...

Stop it now, its a lovely plane... especially with its 5 APU's! :)

Wanabee,Gunnabee,Am

16th Aug 2007, 17:26

SLIP AND TURN

Agreed. If indeed the separation was 500' then clearly something went wrong with one of the aircraft. As I am sure you are aware the TCAS doesn't take account of whether the aircraft are turning. Each calculation is based on rates of descent in protected areas from each aircraft. The collision threat is re-assessed irrespective of direction, So no more calculations would be made than if both were in a straight line.

Also both aircraft are on different frequencies which doesn't help. The only answer (short of moving one of the airports) is to ensure that rates of climb and descent are not excessive. This was part of my line training, even for my current airline that doesn't fly to City. In busy airspace we should reduce the climb rate to not more than 1500'/min when within 2000' of assigned level. Not written down, just good airmanshap.

Now RAs with military fast jet having a bit of fun in Pennine Radar, thats another thing.

Roffa

16th Aug 2007, 17:40

slip and turn,

LHR and LCY were using the same set up again this morning. It is probably the most common in daily use. Without the plates in front of me just now I am guessing, but that bit of sky just north of Canary Wharf where conflicts could occur in the overlapping STAR and SID might be as small as a cube with 2000 foot sides but usually when there's a LCY SID and LHR arrival converging, you see the Heathrow traffic either turned early nearer Tower Bridge or extended a bit downwind almost to overhead LCY 10 Threshold whilst the LCY traffic is obviously directed to keep its head down in the climb.

When the sky is free of LHR traffic, many of those RJs skyrocket out of City and in one sweeping turn exit to the north and/or then round to the east quite literally like bats out of hell. They often remind me of the Lightnings and Canberras skimming the horizons of my childhood!

I don't wish to be rude but much of what you write here just indicates you don't really know what you're talking about.

LCY and LHR operate autonomously of each other. Simply put LHR arrivals descend to 4,000ft and cannot go below that until a set point that is clear of the LCY SID track. LCY departures climb to 3,000ft and cannot go above that until outside of the lateral boundary of the LHR RMA.

There's no interaction between the two units at all bar unusual circumstances i.e. LHR don't alter their vectoring if there's a LCY departure or not. The only thing that dictates where the LHR base leg is is how busy it is and how many are off the stacks on intermediate approach, there's a natural ebb and flow in and out and I stress again it's nothing to do with what LCY are up to.

Obviously if either an LHR arrival or LCY departure busts its level in the area you're talking about there's potential for an incident, but the same is true in many other parts of the TMA. This little corner of it is in no way unique.

Not Long Now

16th Aug 2007, 19:12

Blimey a 146 at 3000' within 30 seconds of take off. Maybe the lightning analogy wasn't too far off...

slip and turn

16th Aug 2007, 19:27

Well I do think its a bit rude of you Roffa old chap, as even though I am not an overworked controller with not enough meal breaks, I have had quite a few hot dinners whilst watching that piece of sky in the last few years :)

I still haven't studied the plates but all I can tell you is that when they LHR & LCY are using these western runways (which of course is frequently) and when there is no cloud obscuring my view or theirs, more often than not, the LHR traffic turns south around the eastern edge of CW and then turns roughly west around my gaff.

Sometimes it extends downwind and might then turn 135 degrees back toward me, and less frequently it might turn earlier down near Tower Bridge.

I am little surprised but not overly so when you say that barring unusual circumstances the traffic from each airport is handled autonomously.

I guess you must be a controller.

I can equally well tell you that the City departures yield a more consistent pattern with usually at least 90 degrees of the right turn out completed by the time they reach abeam Canary Wharf. Not always however. An hour ago while I was having another hot dinner I noticed what appeared to be a merry dance of City traffic extending on the runway heading well past CW then turned north while something heavy joining the LHR approach from the north made a kind of S on the LCY side of the departing traffic.

I am sure what you say about the published procedures is correct but I am just reporting what I see. I am sure that if videos of the traffic were overlaid Red-Bull-Air-Race style then the overlaps would be quite apparent. Not too many level overlaps we would hope, and no simultaneous ones, but the tracks certainly would all the time and that just leaves our 1000 feet to do all the work.

If Red Bull had left their cameras in place the other week covering the sky just next door to this bit then maybe you could be more sure ...

The difference between this corner and any other in the London TMA is rather more obvious than you seem to be suggesting Roffa. As I am sure you appreciate, they are up to a rate of around 2.5M per annum passengers out of LCY I think and in small aircraft that's a lot of movements, especially if they are sometimes only half full!

Bradley Marsh

16th Aug 2007, 19:50

If this is yet again a mis-set altimeter setting you would have to ask:

"Isn't it about time that we all started using QNH in Hectopascals/Millibars?"

Come on USA, if the rest of teh world can use it would it really hurt to conform?

Not a wind-up, just a question.

Brad

Roffa

16th Aug 2007, 20:17

slip and turn,

I'm glad you've enjoyed a few hot dinners watching the traffic out of the window, I've enjoyed twenty odd years watching the same bit of sky from a radar display :)

Hopefully one of my colleagues will come along and back me up, but I assure you LHR traffic and LCY traffic is primarily separated vertically, not laterally, in that area. To do the former would simply not be practical. The respective controllers do sit only a matter of feet apart in the same ops room but can go a whole shift without having to speak to each other operationally, the procedures are set up such that in all configurations the two airports operate independently of each other (well when LHR are on the 27s and LCY on 10, though still independent ops the LHR folk take a close interest in how far downwind the Thames folk take their traffic, but that's another story).

If you see LCY departures doing slightly different things it's either because they're not following the SID track exactly or Thames, for their own reasons, have taken it off the SID early... but that is 99.9% certainly nothing to do with LHR traffic.

Below is an fairly old plot of inbound tracks to LHR, where you see the plots of traffic joining final approach at different ranges that's nothing to do with avoiding LCY traffic. It's just the natural way that the final moves in and out depending on the volume of traffic.

http://mysite.orange.co.uk/roffa/images/radarplot.jpg

slip and turn

16th Aug 2007, 20:30

Very much appreciate the trouble you've gone to Roffs but the fact remains that laterally the LHR inbound and LCY outbound tracks overlap all the time, and the adjustments I thought I was seeing weren't much to do with the various joins but all occurred around the final 180 degree turn sector.

Your plot doesn't show any of the LCY plots of course but does show the variation in LHR tracks in the area of the reported conflict i.e. around a point 70% up and 80% right on your plot (I am guessing).

Is there a Thames plot you could overlay?

As you say, its the vertical separation that keeps us safe.

Edit: Roffa it just dawned on me that you said you'd been looking at that sky on those screens for 20 years. I don't think I'd last 20 weeks. You deserve a medal if they haven't already given you one. Seriously. I'm sure they must have.

Cremeegg

16th Aug 2007, 20:34

Any chance of any more of those "old" plots of inbound traffic to LHR or LGW?

Taffy1

16th Aug 2007, 21:30

Slip n Turn

I must step in and back up roffa here
London City departures do NOT affect Heathrow inbounds. City departures climb to 3000 then further climb on the SID when instructed by radar, Heathrow arrivals decend to 4000 = separated in my book.
In regards to where the Heathrow aircraft do their turns onto base and finals, this is purely down to conditions of the day (winds etc), amount of traffic and runways in use at Heathrow, and also who's controlling at the time I guess!! (I dont do radar!)
Hope that helps Slip n Turn
Roffa hope this backs you up!

slip and turn

16th Aug 2007, 21:57

Look sunshines, I didn't report the conflict, someone else did and THAT hasn't been denied :{

Actually I see taffy has toned down his post a bit so I am smiling more easily :)

Neither am I arguing about how separation is planned to be obtained.

I am just telling you what happens outside my window which has a bloody great 800 foot high glass steel and concrete pointer 4500 feet from my eye dividing the view almost East and West. If I say LCY departures routinely complete a turn to the north before they get west of Canary Wharf they do. If I say LHR arrivals usually turn onto base at the same place albeit higher, then that's what I've seen.

Why take potshots at the messenger ? I am sure that's not what Roffa intended when he asked for backup, or do you know better?

The only contentious opinion I have given (I think?) is that vertical separation alone in this uniquely busy corner seems to push up the chances of an error.

Take that last sentence apart if you like but don't question my ability to use my own eyes please to take bearings against known landmarks please.

Roffa has given us the luxury a nice plot to look at and thanks be to him. How about you guys showing us some LCY 28 departure tracks overlayed on the LHR 27 arrival ones and then you can tell us typically how many times a day LCY traffic climbs reaches or exceeds 3000 early in that right turn out. If it rarely if ever does, then my contention dissolves into oblivion, but if 3000 is frequently achieved that early in the climb out then please read or write on.

Roffa

16th Aug 2007, 21:59

slip and turn,

Very much appreciate the trouble you've gone to Roffs but the fact remains that laterally the LHR inbound and LCY outbound tracks overlap all the time, and the adjustments I thought I was seeing weren't much to do with the various joins but all occurred around the final 180 degree turn sector.

The LCY departing traffic follows pretty much the same track all the time because it's on a SID, there will be deviations but only small ones.

The LHR traffic will fly over quite a wide area. Sometimes it will fly directly over LCY departing traffic, sometimes it will fly east of the LCY departure, sometimes it will fly west of the LCY departure. At all times it will be vertically separated from the LCY traffic until such times as it's at least 3nm laterally from either the LCY SID track or from a specific LCY departure if there's one airborne. Only at that point (3nm lateral sepn) will it be descended further.

I'll say it one last time, yes the LCY deps and LHR arrivals overlap but the path that you see the LHR arrival fly has absolutely nothing to do with where any LCY departures are and all to do with sequencing on to final at LHR. There is no interaction or co-ordination between the two sets of controllers required under normal circumstances, it's all taken care of by each set of controllers following specific procedures.

There's little more I can say, that's the way it works. Accept or not as you wish :)

Sorry, I don't have any more track plots but if you google the various noise monitoring web sites for each airport they might have some on-line.

splitduty and taffy1, thanks :}

Roffa

16th Aug 2007, 22:04

slip and turn,

Why take potshots at the messenger ? I am sure that's not what Roffa intended when he asked for backup, or do you know better?

You seemed to be questioning my explanation of the way traffic is handled in that area, that is all. I know how it works...

The only contentious opinion I have given (I think?) is that vertical separation alone in this uniquely busy corner seems to push up the chances of an error.

Believe me when I say that this scenario is by no means unique in the London area. Arrivals and departures are crossing each other at minimum vertical separation hundreds if not thousands of times a day.

It doesn't matter how quickly traffic out of LCY reaches 3,000ft as long is it doesn't bust it because there's no guarantee of lateral separation at any time. LCY deps or LHR arrivals level busting in that area are very infrequent.

slip and turn

16th Aug 2007, 22:08

Thanks again Roffa

I'll say it one last time, yes the LCY deps and LHR arrivals overlap but the path that you see the LHR arrival fly has absolutely nothing to do with where any LCY deparatures are and all to do with sequencing on to final at LHR. Got that the first time :) - if you were reading anything more into it, then I was just toying with the notion of how many occasions the two controllers might need to liaise on a shift, but you've kindly answered that too.

tom775257

16th Aug 2007, 23:49

<<The only contentious opinion I have given (I think?) is that vertical separation alone in this uniquely busy corner seems to push up the chances of an error.>>

Is RVSM a real concern in your life as well? Perhaps you could give us an expert opinion of 1000' vs. 2000' vertical separation in the en-route environment with PRNAV 0.3nm able aircraft.

Hartington

17th Aug 2007, 07:45

Go to http://lhr.webtrak-lochard.com/template/index.html and set the start time as 0940. Set the zoom out to maximum. AC866 (a 767) is in the Bovingdon hold. If you hover over the aircraft it gives various data items. You have to keep moving your mouse off the icon and then back on to refresh the data. You can't see all the altitude for the critical time (the data tag moves off the viewable area) but he does seem to bounce back up to 4k as he turns finals.

Groundloop

17th Aug 2007, 08:16

The last readable altitude on the AC is down to about 3300 over Canary Wharf (may have gone even lower off screen) before climbing back up to 4000!

slip and turn

17th Aug 2007, 09:10

Is RVSM a real concern in your life as well? Perhaps you could give us an expert opinion of 1000' vs. 2000' vertical separation in the en-route environment with PRNAV 0.3nm able aircraft. Not especially, no, but if you see some relevance then perhaps you could enlighten us, tom?

paull

17th Aug 2007, 09:42

1-Vertical separation is the only thing that is enforced between LCY and LHR tracks.
2-There was none in this case.
That leaves me wondering why all the ATC chaps on here did not say
"Yes, we know about that it was a level bust" , instead we seem to have pages of discussion telling us that it did not happen. Scary.
Of course if the LCY pilot had been equally bad at sticking to his assigned level he would have passed above this AC plane with a bigger separation than they had in this case. (3700 , 3300) versus (3000, 3300) . ;)
Actually the tracking SW shows 3369 as the minimum. If you select the tag contents by left clicking on it and dragging the mouse over the data then you continue to see the values even when they go off the side of the screen.

Flightman

17th Aug 2007, 12:53

Oi, who's using my screen shots? :eek:

:ok:

Flightman

17th Aug 2007, 13:15

<< Go to http://lhr.webtrak-lochard.com/template/index.html and set the start time as 0940. Set the zoom out to maximum. AC866 (a 767) is in the Bovingdon hold. If you hover over the aircraft it gives various data items. You have to keep moving your mouse off the icon and then back on to refresh the data. You can't see all the altitude for the critical time (the data tag moves off the viewable area) but he does seem to bounce back up to 4k as he turns finals.>>

If you RTM, you'll see you can leave the flight detail tags on. :ok:

Roffa

17th Aug 2007, 13:41

paull,

1-Vertical separation is the only thing that is enforced between LCY and LHR tracks.
2-There was none in this case.
That leaves me wondering why all the ATC chaps on here did not say
"Yes, we know about that it was a level bust" , instead we seem to have pages of discussion telling us that it did not happen. Scary.

Can you point out where I or anyone else said the incident in question did not happen?

I was responding to (incorrect) assumptions about the way the airspace in the area is managed in order to try and clarify things for at least one contributor to the thread.

I have no first hand knowledge of the incident in question as I wasn't working when it apparently happened so have refrained from commenting on any specifics and if I did have inside knowledge of a specific incident it's unlikely I'd share it here to any great extent anyway.

threemiles

17th Aug 2007, 14:19

From the lhr.... website:

AC866 goes down to 3369 feet displayed on base leg before coming back up to 4232 feet shortly before intercepting.

Taken from the succeeding 747: 3925 feet displayed equals 4000 ft QNH, so the lowest of AC866 was around 3450 ft QNH.

While Mode-S altitude resolution is 25 feet (Mode-C 100 feet), where do these altitude data come from?

slip and turn

17th Aug 2007, 15:12

From this thread, in Summary for LHR and LCY pilots
1-Vertical separation is the only thing that is enforced between LCY and LHR tracks.
2-There was none in this case.
3-LHR 27 approach traffic be extremely careful not to sink and bust 4000 in vicinity of LCY
4-LCY 28 departure traffic be extremely careful not to climb above 3000 same vicinity.

...even the BA behind the Air Canada is right on the limit according to Webtrak.

For LHR/Thames ATC
Know of any other major hotspots worth discussing in the interests of safety?

paull

17th Aug 2007, 15:12

Roffa
Can you point out where I or anyone else said the incident in question did not happen?
I guess the answer is no, if I look at exactly what was said, perhaps I should have said I was left with the impression that you were saying S&T was not only technically wrong, but you were also dismissive of the point being made which was (to my mind)
Quote:
The only contentious opinion I have given (I think?) is that vertical separation alone in this uniquely busy corner seems to push up the chances of an error.
To which the reply was
Believe me when I say that this scenario is by no means unique in the London area. ....level busting in that area are very infrequent.
I just think that the professionals on this thread are missing the opportunity for a productive discussion here along the lines of:
Is there any way from an ATC standpoint that we can do better in this particularly busy spot?
I would also feel happier if I felt that ATC folk could immediate check on all level busts, that way I would feel happier that they were systematically captured, and then I might feel more confident that they are rare. For example, if your first reply had started "Yes there was a level bust 8:48am....." then I for one would say "Good these guys are on the ball" It is difficult when you sell a service, particularly one of which the ultimate end client has little visibility, to reassure people that the service is good. I think ATC needs some PR!
Busts will appear very rare if we only count the ones that get noticed, but I have no idea of the technology implemented so I will just hope that it is comprehensive in its data capture (historically) and effective in its ability to avert disaster (real-time).
As I read the numerous threads on Pprune, I am surprised the significant number of pilots (particularly the less experienced ones) who think they know it all. It is a little worrying, but it seems that most grow out of it. On the ATC side, I see no such equivalent of the over-confident cowboy (thank heavens) I do however sense a significant defensiveness of attitude, and the fact that your pals in the playground ran over and jumped in so quickly, just reinforces for me this sense of "we are being victimised". What you said was correct, but If I were "slip and turn" , I would feel as thought I was getting a hard time.

Roffa

17th Aug 2007, 15:57

paull,

My first reply was unlikely to ever start "yes there was a level bust at time whatever..." as I'm not at work 24hrs a day 365 days a year and so don't know about every single level bust that takes place either in the airspace I work or the wider TMA and I also don't consider it my place to necessarily confirm or deny anything that's reported here from apparently someone listening to a scanner.

S and L was wrong in his assumptions about how traffic is handled in that area... I wasn't looking to give him a hard time, merely trying to get over the correct information which to start with didn't appear to be being accepted. I wasn't offering any opinion on the reported level bust that started the thread, just clarifying basic procedures used in the area.

I'll say this again, the interaction between LCY deps and LHR arrivals is not in any way unique in the TMA. Arrivals and departures are crossing in similar circumstances (minimum vertical separation, no lateral separation) in and out of every London airport.

NATS is very much aware of the level bust issue and spends a great deal of time and effort on the subject, forgive me if I think there are better forums and ways for tackling the wider issues than PPRuNe.

I'm not here to give anyone a hard time, nor do I feel ATC is victimised or overly defensive. I will however do my best to correct anything that I know to be incorrect but not necessarily comment on any particular incident.

Finally, if you want more info on NATS and level busts, have a look here... http://www.levelbust.com/

gone_fishing

17th Aug 2007, 16:11

@Paull, ATCOs at West Drayton (currently where the TC sectors, and the major London airports Approach Control Service Units are situated) do the best job possible in such a busy piece of airspace. Vertically is the best way to maintain separation and laterally is generally the best way to create separation. Obviously, in such busy airspace like the LTMA this is not always the case, but certainly in inter-TMA aerodrome separation it is. Although you might already understand this, I will give you a specific extract from the current SID charts for the SAM departures from LCY off 28:

SAM4T
LON D23 at 3000' (6.1%)
LON D27 at 3000'
LON D31 at 4000'
DET VOR at 4000'.

As you can see, they climb initially to 3,000ft. Until they are past 27DME from LON (London VOR) they cannot climb any further. Once past 27DME, they can climb to 4,000ft, which they must reach by 31DME from LON. Now, just as a reference for you, in a normal (if that applies in TC) day, at any given time, aircraft inbound LHR would not normally be below MSL there, which is dependant on the QNH, but is no lower than FL70. As you can see, plenty of separation in that part.

At the real ATCOs in TC, correct anything I stated incorrectly, I'm sure there might be something.... because I seem to be one of the only people that recognise I'm not a real ATCO anywhere, let alone in TC and I don't know everything :ok:

glad rag

17th Aug 2007, 17:16

As a regular SLF at LCY I'd just like to say thanks to all the contributors as this has been most interesting and I have to say slightly unnerving.

As an aside on the 6th of August I was inbound to LCY and as the aircraft turned onto base I observed a light aircraft pass under the Dornier offset approx 250" and below by slightly more, couldn't comment on the slant range but it was quite alarming, but as they say, what's hit is history what's missed is mystery......won't stop me flying from LCY but something else to ponder of course.

rgds

glad rag

ps what's a "RJ" they sound cool although the Scot Air Dorns don't hangabout either.

Roffa

17th Aug 2007, 17:46

gladrag,

If you were landing on 28 at LCY you'd likely have been at 3,000ft as you joined the ILS.

The base of controlled airspace in that area, before reaching the LCY control area and zone, is 2,500ft so you can have light aircraft operating at 2,499ft there and not talking to anyone as the airways traffic flies over them at 3,000ft.

It's quite common all round the London area where IFR traffic inside CAS descends to 500ft above the base of controlled airspace with unknown traffic operating 501ft below i.e. up to just below the airspace base and not talking to anyone.

If landing on 10, inside the Class D of the LCY control zone or control area there's no actual separation required between IFR (airways) and VFR (light aircraft) assuming both are talking to ATC, just traffic info and visual avoidance according to the rules, though ATC will tend to build in a certain amount of vertical or lateral but not necessarily 1,000ft or 3nm.

RJ is a Regional Jet, BA146 as was.

gone_fishing

17th Aug 2007, 17:47

Three things happened which I can think of:

1. The aircraft you were on, left CAS, highly unlikely I think on a base to land at LCY.

2. That aircraft entered CAS without clearance, or got clearance, but was just a prat and went disregarding ATC traffic information.

Third, is again highly unlikely, for the fact that I doubt, unless you were on a very long base, there's not any CAS down to the SFC (which would mean your outside definitely outside the CTR) and the ATCO descended the aircraft close, or down to the border of CAS (again, unlikely IMHO - certainly if he is aware there is other aircraft down there outside CAS) and the other guy was operating very near the base of CAS.

My thoughts are no.2 - someone busted the CTR / TMA.

EDIT: Got beaten too it (atleat one of my suggestions is in there as the correct answer :rolleyes:)

glad rag

17th Aug 2007, 18:19

Thanks for those replys they sure cleared things up in my mind,

Hmm......

does this controlled airspace height restriction remain at 2500 all the way to the airport boundary or does it follow the glidepath down?

thanks again

glad rag

Roffa

17th Aug 2007, 18:27

Simply put, if you think of an upside down wedding cake there'll be some controlled airspace around busier airports that goes down to ground level and then steps up as you go further away to a control area, then terminal control area and then in to airways.

An airline flight in and out of LCY will be conducted totally inside controlled airspace.

This might be (http://www.caa.co.uk/docs/7/Dap%20facts3.pdf) of interest.

slip and turn

17th Aug 2007, 18:54

Good to see these matters are only a technicality now :suspect:

Hope the big boys got the message before it was dulled.

As if to reinforce gone fishing's point number 2, we just had another dance in the same sky just 20 minutes ago. The light single (PA28 maybe) looked like it was on a VFR South to North transit clearance at "not above 2400" ... he got as far as Canary Wharf and then turned back to the safety of the shadows behind my gaff. While he was orbiting back there, an executive jet took off from City on 28 and departed right turn out to the sky where the light aircraft would have been had he not done a 180. Then undaunted, the light aircraft had another go, this time making good a nice straight path just to the east of CW while a heavy manaevred for the LHR approach well above him (maybe still at 7000) but with his landing light on:-)

Don't get me wrong, I like to see a bit of live and let live when there is plenty of slack (there was nothing else in the sky right then) and it is more or less CAVOK this evening.

bookworm

17th Aug 2007, 19:08

As an aside on the 6th of August I was inbound to LCY and as the aircraft turned onto base I observed a light aircraft pass under the Dornier offset approx 250" and below by slightly more, couldn't comment on the slant range but it was quite alarming

It's very difficult to judge the vertical separation of other aircraft. You may well find that your 250 ft was actually 500 ft and no one entered CAS without clearance. It is very common for aircraft to fly right up to the 2500 ft base.

Roffa

17th Aug 2007, 19:09

Now a VFR transit is being turned in to some sort of event?

Sorry, I give up.

slip and turn

17th Aug 2007, 19:21

Forgive me now Roffa but I may have held my tongue once too many times already. I think that as experienced and as unassailably knowledgable as you are, you are perhaps inadvertently straying into pedantry by continually pointing the finger at me as if we all need to learn something from the finger-pointing. Can I not gently get you to agree that perhaps that might be risking deflecting the main issue in this thread?

Those of us that are focussed on the main issue have been in www.levelbust.com (http://www.levelbust.com) long since.

You have also several times asked us to believe that this piece of airspace is no more risky than any other which relies on 1000 foot separations.

As you know I haven't accepted that view which I think is too general. You got me thinking ok perhaps he means fast executive jet traffic so what about Fairoaks to the south, and Biggin Hill, and Northolt of course, and Stansted traffic at the upper levels ? But none of those is quite like the 'in your face' peak flows from London City is it?

To me Roffa, your latter posts sound much the same as saying "close the thread - there is nothing new to learn".

As you know, I reckon this East London bit of airspace is unique. You seem to be saying it's no big deal. I have easily accepted your statements of fact but I am less comfortable with the subjective stuff.

I mean for goodness sakes, I don't mean to spoil it for the hoards of Biggin Hill and Elstree clubbers who've been crossing it for years, but not only has this bit of sky got all the ingredients discussed, but on some balmy sunny days it has occasional Cherokee drivers teetering across it at "not above 2400". Sometimes I wonder if they are under any control at all judging from the fact that one or two have sometimes been west of Canary Wharf when they do it

And then I check myself - nearly two decades ago I WAS on a clearance from 132.7 so I wasn't completely without hope, but I was too far west to be able to land clear on the few green bits remaining! So I got a fine view of the western face of the single CW tower that existed on that Sunday teatime just before dusk and the controller kindly double-checked my type, then bit his lip while the ramifications of the query sunk in to my wetware - hell it might even have been you !

Getting as far as Canary Wharf on a transit in a PA28 and then having to scuttle back out of the way is not how it was planned by either Thames or the pilot I think. Being stopped a mile or two further south and told to orbit when it is realised that departing IFR traffic is being held on the 28 at LCY is of course more easily acceptable.

Share more of your views with us please if you can. I guess after 20 years you have to balance all sorts of interests when away from the screen and the accommodation of low-level single engine traffic in this zone is is just one you'll have regularly offered a view on, no doubt. but do please continue to enlighten us on the hotspots.

Roffa

17th Aug 2007, 20:10

slip and turn,

It's not finger pointing, it's just replying to stuff that you post.

Those of us that are focussed on the main issue have been in www.levelbust.com long since.

I'm not sure what you mean by the above? If you're somehow involved with the NATS Level Best campaign maybe you could let me know in what capacity just so that I know what level to pitch any further responses at. I'm well acquainted with the main folk running it from the NATS side and it would give me a better idea of your level of knowledge and understanding, your profile doesn't give much away.

slip and turn

17th Aug 2007, 20:16

Roffa just think of me as the guy with the big north pointer and the hot dinners. I am nothing whatever to do with the folks in the levelbust project, just an interested bystander :hmm:

paull

17th Aug 2007, 20:48

it would give me a better idea of your level of knowledge and understanding
Ok, I know you think that there is no possible value to be had by discussing things on Pprune, after all we are not knowlegeable. Well, I have spent more that 20years putting together the appropriate measurements and goals that tell me whether someone is delivering the service they are supposed to be and I am horrified that you do not appear to have a systematic way of knowing whether someone actually busts a level unless one or other party cares to report it. (Currently estimated at 30%).
For heavens sake, even the network management guys I worked with over 20 years ago worked out that a pre-cursor to a site being isolated was one of the two routers being down and so we knew when it happened, every time. AND you did not have to be working to know it had happened, ANYONE authorised to work on it could connect and say "We had a Router down at 8:30".
How you can let someone build a system for you that does not allow you to know with certainty how often you have lost separation when we know that that is a pre-cursor to a collision is absolutely beyond me and it is WAY WAY off best practise in performance management. Of course it might be the tops in the closed world of ATC but I think you could really do to cast your net a little wider. I too have visited the link you pointed me to for Level Busts and it needs a lot of work if it is pitched at the man in the street, if it is pitched at professionals then things are in a sorry state. (IMHO)
Flame Off - Bye, will not bother you further.

Roffa

17th Aug 2007, 21:10

paull,

We do have a Separation Monitoring Function that tells us automatically when we've lost separation (subject to certain parameters).

We don't have anything that will automatically record a level bust on its
own at this point in time.

The reason for asking level of knowledge is that there's little point in going on about flight rules, separation standards, ATC rules, procedures and how the airspace around London is organised in any great depth if the other party doesn't know exactly, or at least have a reasonable knowledge, of what is being talked about. This thread has already demonstrated that to some extent, limited knowledge has lead to false assumptions. That's in no way meant to cast any aspersions on any contributer, it's just a fact. The amount of time I can spend here is finite, I can and will answer questions to a certain degree but I can't spend enough time to always go in to great detail to cover for the lack of knowledge for those outside the ATC/commercial pilot world.

Sorry.

slip and turn

17th Aug 2007, 21:53

OFCOL Roffa!

When was the last time you made a false assumption about things well within your grasp had you but looked at it, lately? How much sugar is in 100g of your regular bowl of Kelloggs Rice Krispies, for example (assuming you do have time for breakfast!). You are like a dog with a bone, you old war horse you :ugh: .... go on, SMile :} ... you know we love you really !

Use any jargon you feel comfortable with. We are all here simply in the pursuit of knowledge and you have that in Spades so if we get stuck we'll sort ourselves out and put our hands up or you'll correct us (just the once oughta do it!)

Flightman

17th Aug 2007, 21:54

<<From the lhr.... website:
AC866 goes down to 3369 feet displayed on base leg before coming back up to 4232 feet shortly before intercepting.
Taken from the succeeding 747: 3925 feet displayed equals 4000 ft QNH, so the lowest of AC866 was around 3450 ft QNH.
While Mode-S altitude resolution is 25 feet (Mode-C 100 feet), where do these altitude data come from?>>

Data is supplied into the noise and track keeping system direct from the NATS SSR.

gone_fishing

17th Aug 2007, 21:59

Paull and slip turn, there is a systematic way of checking level busts - they look at the level readout from the Mode C / S transponder :}. There is a new radar type being used in TC that will show the level set in the AP, aswell as the current level, so that can help - but again, I know of a Captain who will make his FO fly a 742 freehand from FL150 to landing to make him, "gain experience" (the FO loves it by the way - seriously) - but it shows that this is useless. At the end of the day, human factors are always apart of aviation, and I don't know if I wish for them to be gotten rid of - then there wouldn't be any "Roffa"s and "Taffy1"s around to answer your questions, because they will have all been replaced if we go on your sort of realm of let technology take over. You know, they were bringing in a TCAS type III, and in the RA, aswell as trying to regain seperation through vertical adjustments, it will apply horizontal instructions - however it was scrapped - one of the reasons I believe because it was deemed to take too much control away from the pilots (they should be able to apply there own lateral manoeuvres themselves).

Level busts are not the only thing, there are CAS busts (aircraft entering CAS without clearance) and in fact one guy did so, and flew for an hour over Heathrow without talking to anybody halting departures and arrivals until Northolt got the flare guns out :D You must understand, and respect that there are humans up front, and on the ground and they do an amazing job (so much so, I hope to join the "family" when I'm older), but they can make mistakes. That may seem crazy to you. Yet, you are safer flying to Alicante than you are to catch a taxi to the airport. It's a matter of just having to accept the statistics. Safety is always a prime concern for the aviation sector, and pilot error has dramatically decreased over the years as the cause for error - however, it still exists. A book I once read, I feel appropriately sums it up: "Accidents are so rare in America and Europe that virtually anything that the authorities and the airlines do to make flying safer will not reduce the accident rate by any appreciable statistical means." You may ask yourself, why is he rambling on about this, but I feel at the end of the day, that is what you are venturing towards - flight safety in general and within the UK. Well, let me remind you that we have some of the safest and most efficient Aviation authority and Air traffic service providers. The LTMA is very busy airspace. Although I do not know the exact percentage, about half of the UK airspace is known as "open FIR" or class G airspace (Class F and G are uncontrolled). We cannot manage to make all of it controlled airspace, not even Canada - where ALOT of there airspace is controlled - they still have uncontrolled airspace and aerodromes. I hope you start to see what is being said.

Regards,
G_F.

slip and turn

17th Aug 2007, 22:43

G_F perhaps I led you astray / set a bad posting example with the old PA28 anecdotal stuff. I'm sorry...Can we please return to the main issue in this thread and either leave it at that, or develop it with info about more airspace hotspots without losing the crux of the matter. That was surely: to inform all those commercial pilots and airspace planners that might not already have it foremost in their minds that airspace hotspots do exist in places where it perhaps hasn't been much highlighted before ...

From this thread so far, in Summary for LHR and LCY pilots
1-Vertical separation is the only thing that is enforced between LCY and LHR tracks.
2-There was none in this case.
3-LHR 27 approach traffic be extremely careful not to sink and bust 4000 in vicinity of LCY
4-LCY 28 departure traffic be extremely careful not to climb above 3000 same vicinity.

"forewarned is forearmed"

I suspect that this is all too much of a political hot potato for any others to be highlighted ... but we live in hope ...

Spitoon

17th Aug 2007, 22:53

I think I have to come in and give Roffa some support for what he seems to have done in this thread. Before I go into any detail about the thread itself I will offer my credentials as a controller for the last 30 years or so. I have not worked the London area so I cannot give expert opinion on the procedures in the specific area in question (and, frankly, I don't have the charts to hand - or the will - to try an analyse the situation).

The first post appears to give details of a loss of separation followed by a TCAS RA. I don't see anyone who has suggested that an occurrence did not take place. If the events originally reported are correct it will be subject to investigation.

Roffa profile says he does ATC and his posts on this thread and others in the past show him to be both technically expert and very patient in explaining how the ATC system works in terms that can be easily understood by those with only a passing or no knowledge of aviation. If he makes a comment on the way that ATC in the London area is done then it must carry some weight!

On the topic of separation, 1000ft vertical separation (or a metric value which is broadly equivalent) is 'standard separation' and is used the world over between aircraft either under active control (i.e. following specific instructions from a controller) or in pre-defined procedures which are intended to ensure separation between aircraft in the same locality. The pre-defined procedures used in this area - where operations into Heathrow and London City are largely independent of each other - are designed to reduce/minimise the need for co-ordination between the controllers providing the service to traffic using the two airports. This is a technique that not only increases capacity but also reduces the risk of errors occurring during co-ordination.

From the perspective of applying vertical separation, there is absolutely no reason for the airspace under consideration to be treated in a special way. It is true to say that traffic density has increased over the years but the hazards that this may create are mitigated by the development and implementation of both ground-based and airborne systems to provide what are commonly referred to as 'safety nets'. These provide a warning that the normal separation criteria may have been eroded (perhaps as a result of an error) in sufficient time for action to be taken to avoid any further deterioration of the situation and, ultimately, to avoid a collision.

Whilst paull may be '...horrified that you do not appear to have a systematic way of knowing whether someone actually busts a level...' it is not for want of trying - much effort has been expended trying to do this and it is getting closer. Sadly it's not as simple as the router example you give. Routers are are fairly straightforward devices that will do what they're told to, know what they've been told to do and can monitor how well they are performing (or can be monitored) without substantially affecting their performance. The ATC system includes a human within the system and a multitude of potential circumstances and rules with which to resolve the traffic situation. The fundamental problem is that most radar systems are not aware of the cleared level of each aircraft, and thus able to detect deviations. There are clearance adherence monitoring systems under development which are showing promise for the en-route environment but impose too heavy a workload penalty in the terminal environment to be practical at present (although developments are continually taking place and perhaps someone with more recent experience in these systems may be able to offer some comment).

slip and turn's posts appear to be becoming more and more eccentric and I am not inclined to waste my time and try to respond to the few points that have not already been comprehensively addressed by Roffa. It does appear that the proverbial little knowledge may be causing a problem here. However I will apologise if I have used any jargon in my post that causes confusion.

gone_fishing

17th Aug 2007, 23:07

I'd like to add, seeing as slip and turn doesn't seem to understand - one method of seperation - either vertical seperation or lateral seperation more than adequate means of safely dealing with aircraft. If you had to have both in place, I think that the air traffic management in the LTMA would collapse. There would be extensive delays, aircraft would have to carry more and more fuel because they would be holding for longer in the stacks, ATCOs would become more stressed, so would pilots, and your perhaps looking at more chance of a collision. Lateral and vertical seperation is not an option. It's one or the other. And that's perfectly fine. Now you could get really fussy and never have aircraft go over each other, because even with 4,000ft of seperation, if that pilot decides too, in certain aircraft, he can cover that descent more than quick enough to cause an airprox and possibly a collision. Such seperation is impractical and unnecessary aslong as pilots comply with ATC instructions when inside CAS. If they don't it backs down to TCAS and (unreliable at the speeds most commericial jets travel at) the "see and avoid" principal.

Regards,
G_F.

slip and turn

17th Aug 2007, 23:42

gone_fishing

18th Aug 2007, 00:00

Separation was lost, but as I said again, any other way and it will have terrible consequences. The way I see it, I think your trying to make a point that is something that is actually more insensible than it is worth. As for "sucking eggs lesson", please provide your experience and I will apologise. As it seems from one of your posts, you seem to make a reference that you went flying "a long time ago" in a PA28 (after commenting seeing somebody else fly one near City). Now, I don't see how that means you really have anymore experience than me in ATC providing seperation for you. Sure, you may have got the old, "Extend your downwind, your number 2 to the Boeing 727 on 5 mile final, orbit right if necessary" stuff, but hardly seperation of this grade. Then again, if it was more than 10 years ago then I have no way of commenting seeing as the rules, procedures etc are way different to know from them.

I'm sorry to make the following comment, but it almost feels like I'm hitting a wall, because you are not taking the important bits out of my comments, and are only picking at anything you find that might give you something to say.... the experts have spoken above, I have siad my little bit (from what very little knowledge I have) and you still seem to be arguing. :ugh:

Roffa

18th Aug 2007, 10:28

I suspect that this is all too much of a political hot potato for any others to be highlighted ... but we live in hope ...

Not at all. There's a great deal of open information exchange within the industry between ATC and operators and subsequent modification of or introduction of new procedures on both sides to mitigate as much as possible against level busts.

slip and turn, if you have the "credentials" you'll know how and where to raise any concerns, issues or serious solutions you might have such that something will actually be achieved over and above an obscure thread on PPRuNE. I look forward to continuing any further debate there.

Spitoon

18th Aug 2007, 10:55

Spitoon nice to have your input. I understand everything you say except a couple of things:
1. Why having written so much you haven't got the will and inclination to have a look at this bit of airspace in a little more detail.
2. Why you think that my mentioning that politics might compromise safety is "eccentric". The TAM/Congonhas thread might be worth a read on that one.1. Because you have demonstrated that you are not prepared to accept what those with valid credentials state and rather than to respond with reasoned argument you go off at a seemingly irrelevant tangent. If I took the time and trouble to look at the charts and procedures I have no doubt that I would find them to be well designed and appropriate for the environment in which they are used.

2. I found references to Rice Krispies for breakfast to be eccentric. Safety is always in balance with other things - it has to be if we want the lifestyle to which we have become accustomed. Comparing today's environment outside your window with that of 20 years ago may well lead you to think that traffic density is greater now but the rest of the system has also evolved in that time - both from the safety perspective and politically.

It takes some years to train to be a controller and many more years to understand today's ATM system. A passing aquaintance with some of the rules often causes confusion as appears to be the case with some of the posts on this thread.

Your powers of analysis haven't even come close to establishing my credentials and because aviation is a small world and I value my anonymity especially when discussing safety issues I shall not be divulging any more than you can (or cannot) read between the lines. One day you might know as much as I have forgotten.And finally, whilst I am happy to debate many technical issues with others on this forum, I'm afraid I won't waste my time with someone who is not prepared to provide even a modicum of creedence for their supposed expertise - whilst still maintaining their anonymity - and then resorts to childish insults.

slip and turn

18th Aug 2007, 11:49

Good day Spitoon
You make a good point:A passing aquaintance with some of the rules often causes confusion ... I guess that's partly why line checks are necessary (knowledge of the rules isn't enough to be safe).

On the questions of Rice Krispies on the one hand, and childish insults on the other, the first was I agree a perhaps eccentric attempt at lightening the dialogue and the second was a less than perfect put-down for the child (because he got up again!)

Can I put my overall point another way perhaps? Will you consider an analogy between airspaces and airframes?

We all know each airframe is different. Many of us remember the picture of the 737 with the lid rolled back like a sardine can. Many of us can think back much further. The DH Comet. Stressline hotspots for want of better words, leading to material fatigue, and finally failure.

My point is that every different airspace whilst designed by experts, nevertheless will be discovered to contain hotspots. Airframes get older, and so do airspaces. Whilst refits are sometimes economic, you can analyse the hell out of a problematic airframe but ultimately the best place for it generally is on a scrapheap in the desert. Airspaces can't so easily be scrapped so the way they evolve is of immense interest surely? One might also be forgiven for imagining that from time to time the 'expert' controllers, pilots, airspace designers and regulatory authorities might be firefighting to keep them operating ? We actually know this is so on a macro scale - look at the hoo-ha we have in the London area on the question of increased runway capacity alone. All kinds of non-expert interests are involved and interesting things happen like the set up of that fascinating Webtrak (noise-lobby induced) site which I had no idea existed until I read this thread.

I don't claim to be an expert in anything other than paddling my own canoe, otherwise I'd spend my time in courtrooms getting paid for it, but on the other hand I am loathe to accept that my knowledge is proverbally dangerous just because I sometimes use it to pose awkward questions and conjure up uncomfortable analogies.

You experts now work in an ever more transparent environment - myths get debunked very quickly ....

gone_fishing

18th Aug 2007, 12:31

There is still nothing dangerous about that particular part of airspace. You do realise that even at places like Cardiff, they sometimes bring aircraft under / over each other with only a 1,000ft of seperation?

It is more than a safe standard to separate aircraft by - level busts happen, and no matter where they happen, it's dangerous. But that doesn't mean that we shouldn't use 1,000ft sep. Regarding, "tough questions", I don't believe your questions are tough to answer at all - they have been answered by the ATCOs, and they stand by, and still don't see what the problem is - funnily enough because a problem doesn't exist.

If your going to be like that, why don't we have aircraft not lining up on a runway as another departs, why don't we scrap the "land after" clearance, etc... get real. :rolleyes: These things are perfectly safe - just like the vertical seperation. In the UK, safety is paramount. If there was a problem, why wouldn't the authorities do something about it? Not everyone in aviation is out there just to make money. In fact, we go beyond ICAO requirements. We are "that safe". For example, our minimum wake vortex seperation is usually greater than ICAO values (category depending), we use modified ICAO RTF and list the modifications in the back of CAP413 with the explanation always being from a safety stand point. Why do they do all these things and more, and yet leave a "hotspot" in LTMA airspace alone? Sure, it maybe a hotspot - but then vertical seperation ensures things are kept safe. At the end of the day - the CAA CANNOT get rid of human factors. Nothing can be done short of absolutely destroying British aviation... because that's what would happen if we start applying massive amounts of seperation both vertically and horizontally. The LTMA would just break down:ugh:

Now, let me ask you my question. What do you think should be done? Bearing in mind, this new option has to ensure the same expeditious movement of aircraft at the moment. I think you will find that the solution has already been implemented.:ok:

slip and turn

18th Aug 2007, 13:35

Good afternoon Gone_Fishing ! Hope you slept well, growing lad needs his sleep !

I am sorry about the sharp put down last night but my feeling was that you were allowing your confidence to get in the way of basic good manners.

With your obvious application to your studies so far, you undoubtedly have a career in aviation to look forward to, but do wake up to the fact that people who might not wish to make a thing of it might have "been there done that" eons ago and they have might also have complimented their knowledge by the study of or by working in a completely different field.

Take a look at that TAM/Congonhas thread again. You'll see some real pros at work there biting their tongues so hard that they must hurt, and opening their minds to all kinds of uncomfortable hypotheses and revelations. You'll see for example PBL leading a sizeable chunk of the discussion. In aviation credential terms he was just a PPL when he started offering views on commercial aviation safety, but of course, he developed his interest over many years and steadily built up his credibility so that he is now a world-leading academic on an extremely important subject. You will notice how responsibly most posters are conducting themselves over there. People died and that alone demands reverence.

As Spitoon or Roffa said, this thread here has become obscure in PPRuNe.
Reasons might include:
1. The near miss analysis isn't any where near as baffling as Congonhas, and
2. It simply hasn't generated much interest due perhaps to some irreverence, indifference, some possibly boring denial (on both sides of the argument), veiled insults and perhaps my bad attempts at breathing some life into it.

I do take responsibility for my part in degrading the discussion. I was biting my tongue, but then I yielded to repeated goading. I am weak !

When you study a subject you love as hard as you have G_F, it becomes second nature to recall pages and headings and sentences and bullet points and jargon. Trust me, it really does. And you can get straight As in all your exams that way including all the aviation exams. I remember doing the same. I wouldn't do it differently. You feel very good about it. I always do. Many people actally pass exams but never get the feeling they are completely in command of a subject so far .... in a way they are life's true achievers when they ultimately do get to command very important things.

For those that find exams easy and those that find them hard, the real knowledge will come later when you apply and experiment with what you learned from books, "annotate it in the margins" so to speak with your own observations, and then balance the whole lot of it with other worlds around yours.

My apologies again for the put down. I hope you understand a little of why I weakened and tried it.

Now look what I've done ... the thread is way off topic and perhaps without hope of recovery ...

You ask me what I would do, and suggest that a solution has already been implemented.

Well, a very long time ago I was given a definition of the word "Management". It is not the only definition of course but I suggest it is still good for some problems in ATManagement as well as any other ... it is this "Management is the ceaseless pursuit of small improvements"
One possible foil to that of course is "If it ain't broke don't fix it"

gone_fishing

18th Aug 2007, 14:08

No problem sir. I do also owe you an apology. I over stepped my mark, for which I regret.

Back on topic:

I see some of things you are saying in the fact that you wish for the NATS management and perhaps the CAA to discuss alternate means of providing seperation and a back-up in case seperation degrades (am I sort of along the lines?). The only problem I see is that it's very difficult to implement anything other than is in place, because there must be a balance between safety and expeditious movement of traffic - and I think NATS has that down to a detail.

slip and turn

18th Aug 2007, 15:20

I see some of things you are saying in the fact that you wish for the NATS management and perhaps the CAA to discuss alternate means of providing seperation and a back-up in case seperation degrades (am I sort of along the lines?).Well yes if you like, that's part of the "ceaseless pursuit of small improvements" in general terms that I guess has yielded initiatives like Level Best and the AP Set Altitude Mode S downlinks for example. But there isn't much evidence that either of these initiatives helped in this case.

You are right, airspace design changes are no doubt hugely problematical and expensive to test and certify, just like introducing new airframes.

For example, simplistically, the STAR procedure that brings LHR traffic in over the LCY SID might be raised 500 feet or more at that point just to build in an extra buffer - in practice such a change might not exclude too many actual paths, but I don't know. Even if it were possible, such a change would have some knock-on effect perhaps in controller workload or cockpit workload whilst LHR traffic establishes on the localiser and extended glidepath whilst simultaneously managing the little "hump" I have just introduced and the slightly now more hurried need to manage speed o the extended glidepath.

I emphasise that my last paragraph is undoubtedly simplistic. But if not overly so, then perhaps the extra workload could in turn be alleviated by special ATC discretion to authorise earlier decent when LCY wasn't moving. But then we are already told that ATC prefer to keep things separate(sic) vis-a-vis LCY and LHR for tried and tested general reasons. LHR are not interested in information about LCY traffic. That's Thames' bag. Or maybe some of the problems couldn't be improved by use of ATC discretion because very often both procedures are simultaneously at peak activity anyway.

I am sure a lot of what ATC have to do is a bit like 100 per cent successfully threading the proverbial camel over and over again several times a minute without blinking, so I do understand their reluctance to wet their thread/camel just because I suggested it !

So then for experts whose job it is to already have considered these things, it might boil down to a question of proceeding with new downlinks / back up systems, plus the more general Level Best awareness campaign, all glued together with the assertion that for the moment the current procedures ain't broke very often at all. That seems to be what we are seeing from the 4 ATCO contributions.

We know it ain't perfect. This incident shows one place where it might be a bit threadbare.

Gattaca

20th Aug 2007, 17:35

I flew into LHR that morning.After we landed an Aircanada landed after us.
The controller then on the ground frq informed the AC pilots that a report was going to be filed after their level bust.

I't wasn't that professional to say something like that on an open freq.They should have called thier agents or contacted them by telephone.

normally right blank

20th Aug 2007, 18:48

It wasn't that professional to say something like that on an open freq.
Not so fast, Gattaca. Maybe procedures say ATC must deliver this information ASAP, open frequency or not. "They" will find out anyway. I find it fair to the pilots, that they know something happened, that warranted a report. And very sensible to wait till they were on the ground.

Spitoon

25th Aug 2007, 19:20

Sorry, I've been having to work for my living the last few days but I've also been thinking about thius thread and, in particular, slip and turn's comments.

Responding to no particular earlier comments, perhaps it's important to remember why we separate aircraft - it's essentially to stop them banging into each other. Separation standards have a 'margin for error' built into them, certainly to take account of the accuracy of the instruments that are used to provide information about the relative position of the aircraft being separated but, I feel fairly sure, to provide a buffer for when us humans make errors. We are conditioned, perhaps more so in the case of controllers than pilots, to achieve separation rather than avoid collisions, but ultimately the latter is the event/situation that all of the rules are designed to avoid.

In the case that we are talking about it looks like some of that buffer was used - but the aircraft did not collide. We now have to learn from the event and see if there is something we can do to prevent recurrence - but, sometimes, it's just human error that is out of character for someone highly trained and competent in what they do and, as yet, we (or the pshrinks) don't understand the causes or how to stop it happening. Of course, if it is part of a series of errors that may indicate a deterioration in competence there are things that can, and should, be done.

Thinking about this, if we increased the vertical separation used in this piece of airspace - and, presumably, all other pieces of airspace which share the same hazards and risks - to 1500ft as suggested, what would the reaction be in the event of a level bust? To suggest increasing the separation to 2000ft??? In all probabaility (because there are lots of other barriers in the system) the outcome of the level bust would be the same - the aircraft do not collide but we use up some of the buffer that is built into the system.

Thinking now specifically of s and t's analogy between airspaces and airframes. Yes, I remember the picture of the 737 with the lid rolled back like a sardine can and I certainly know about the fatigue problems in the DH Comet. In the airframe/airworthiness world things changed after both of those issues were recognised. In very simplistic terms, after the DH Comet crashes we got round windows and after the Aloha Airlines 737 incident the inspection regime for older airframes was substantially. These changes came about because we learned from what had gone wrong - and took actions to prevent recurrence.

Although I have no connection with NATS I feel fairly confident that the organisation is learning from all incidents that occur and taking measures to prevent recurrence. It is important also to recognise that the environment is continually changing. ATC now routinely uses tools to monitor separation achievement far more closely than has happened in the past. As I tried to indicate earlier, this is partly mitigation against increased risk because of higher traffic densities, and to identify any systemic 'hotspots' (that are then 'managed').

So, overall, whilst I understand that an incident may cause concern, I see no reason to be concerned that there is a hotspot that is being ignored in that particular piece of airspace.

slip and turn

16th Apr 2008, 14:04

I don't scan this bit of London sky anywhere near as continuously as those in charge, (or anywhere near as often as some of my critics think I do :p) but since it is one bit of England's sometimes blue and pleasant sky out of a handful which I often stare into when I am seeking inspiration, I sometimes can't help noticing aircraft movements in it ...

Despite my now infamous typo on 17-Aug-07 I think we established last time that the LHR 27 inbounds when turning and descending south over over Canary Wharf (if that's where they happen to be vectored) were never supposed to decend below 4000 until south of LCY 28 extended RWY centreline?

I saw one recently that looked a bit low, with the proverbial opposite track LCY departure in the same bit of sky albeit below by some margin, and so I in the fullness of time I checked Webtrak. Sure enough I found one at about the right time which seems to have dropped to 3907 or something when abeam LCY. Webtrak doesn't show the LCY traffic unfortunately.

Most on Webtrak if vectored this way seem to be at least 500 above that and often a lot more.

I am sorry it rubs some of you ATC folks the wrong way, but I haven't gone trawling through hours and hours of Webtrak to find this, so surely breaches(?) like this should not still be happening?

Edit: Oh dear, I left Webtrak running while I was typing this and when I went back to it I noticed something else slightly odd ... a different aircraft which I had marked as inbound had apparently reappeared from the West and appeared to be more or less glued to 3914 while it stooged around while (I guess) some poor ATCO was bravely trying to fit it in with the traffic coming off LAM north of the river - maybe it was a Go Around? But the point is that it was stooging around at 3914 (according to Webtrak) in that sensitive bit of airspace we discussed in this thread i.e. north of the LCY 28 extended centreline and finally crossed it at about the same reported sub-4000 altitude...

Sorry :uhoh:

Dont Hang Up

16th Apr 2008, 14:32

Don't know much about Webtrak but unless the altitudes are QNH corrected (unlikely I suspect) they can be out by a significant margin (easily a hundred feet and often more). Perhaps you should post an ATC thread rather than a Tech Log one so that those ATC guys can put you straight.

HEATHROW DIRECTOR

16th Apr 2008, 14:34

Aircraft MAY be descended below 4000ft in that area under certain conditions so it is not a rule set in concrete.

Webtrak and SBS do not take account of the relevant QNH setting so the height you see indicated on your screen will almost certainly not be the correct one - in fact it may be many hundreds of feet out when aircraft are below the Transition Level. On "real" radar, into which the current QNH is entered, aircraft may be accepted as being at their cleared level when the height readout is within 200 ft of that level. The Manual of ATC states:

<<a) An aircraft may be considered to be at an assigned level provided that the Mode C readout indicates 200 feet or less from that level>>

So, your examples of 3907 and 3914 could legitimately be assumed by ATC as level at 4000 ft. When aircraft are climbing or descending, they may be assumed to have left a particular level when the altitude readout changes by 400ft in the expected direction..

slip and turn

16th Apr 2008, 14:40

QNH corrected?Yeah I wondered that, but I'd have thought that it would be corrected because Webtrak was created mostly for the antinoise lobby to check what they think they saw/heard, and it wouldn't surely be a good idea to give them more excuses than they really need for complaining?

I won't bother the ATC folks in their den ... they'll soon spot it here where it always was and they'll soon comment again if they feel the need ;)

Edit: Aha! Told you ... Mr HD beat me to it :p ... they are sharp those guys, especially some of the oldies :ok: Cheers HD.

Spitoon

16th Apr 2008, 16:02

QNH corrected?At the risk of getting dragged back into this resurrected debate, a quick look at the Webtrak site will tell you that that the level data is, in fact, referenced to 'the primary airfield elevation' which I would assume means Heathrow QFE in this case. The aerodrome elevation is 83ft. So, the tracks for the aircraft that concerned s and t so much were flying at altitudes of 3907 + 83ft and 3914 + 83 ft respectively - that is to say at ALT 3990ft and ALT 3997ft. Given that the pressure could change by up to 1 hPa/mB without the QFE being updated, the altitudes could be up to 27ft in 'error'. I'd say that was pretty accurate if the aircraft were assigned ALT 4000ft (which seems to be the assumption).

s and t, how much more accurately do you want the aircraft flown and controlled?

Can't we just drop it now? :ugh: