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BmPilot21
16th Aug 2001, 01:12
LHR always give the number of track miles to touchdown on giving a descent below transition level. Do they have special technology to do this, as they seem to be the only people that give this valuable information.

Going into Madrid the other night, given the notorious 'downwind snatch', plus kept high and fast. Asked how many track miles to go, and the guy didn't know! No wonder we have so many 'interesting approaches' into some of these airports. He obviously asked someone else, and came back a minute later.

My point is that he was giving descent and speed control without knowing how many miles we had to touchdown! How do LHR get this info. and why doesn't anybody else seem to know (or care it seems)?

Gonzo
16th Aug 2001, 01:28
BmPilot21,

I'm sure one of my colleagues in TC will jump in, but I'm not aware of any special technology! It's all just down to working back from the a/c that's just establishing.

Gonzo.

(PS You may want to repeat this question in the ATC forum.)

[ 15 August 2001: Message edited by: Gonzo ]

411A
16th Aug 2001, 02:06
BmPilot21---
MAD is not so bad, once you get used to the place.

Edited by moderator - wielding my big stick tonight to keep the forum purely Tech based. Any other comment is unnecessary to the discussion. Comment furthur down relating to this removed as well.

[ 16 August 2001: Message edited by: Checkboard ]

compressor stall
16th Aug 2001, 06:58
Cairns in Australia does it too, although I cannot think of any other Oz airports that do it.

Very useful as when they vector you around the hills traffic dictates how far you get vectored before bringing you in, so situational awareness is not really an issue - your descent point is in the lap of the Gods. um er controllers. :D :D

esreverlluf
16th Aug 2001, 11:27
As many of you probably know, Sydney does give track miles to run just about every arrival. Of course they are, without exception, woefully inaccurate, but then again, that would take the fun out of the traditional Sydney slam dunk... :cool:

Pointer
16th Aug 2001, 13:23
Even in Europe there are more places that give it, in GVA they sometimes do and in germany i've been given trackmiles more than once!

I agree with 411a, that you should base your approach on your own situational awareness and see the trackmiles given as an extra confirmation.

cosmo kramer
16th Aug 2001, 14:38
Comment relating to post above removed, as it is no longer necessary.

[ 16 August 2001: Message edited by: Checkboard ]

BmPilot21
16th Aug 2001, 15:09
411a, yes I'm a junior guy, flying a glass 737 (as my profile says). I agree that its up to me to know how many miles to touchdown IF I know what routing I'll be doing. My point is that MAD continuously cut the corner on the descent as well as keeping you high and fast. I cannot predict how many miles we've got to run as they keep cutting us in early. Yes, I can predict a snatch on the FMS, and so work out the 'worst case' profile. Unfortunately, ATC have other ideas and won't let us descend.

My point is that the ATC guy is controlling our descent and speed, and HE doesn't know how many miles I've got to run. We can ask for repositioning etc. but this is obviously undesirable.

Also, some ATC guys just don't understand that we can't 'go down and slow down'. Doing a Riviera approach into Nice the other day, we were asked to maintain 180 to 4 dme!!!!
Yeah, right! Gear down, flap 30, 135 knots at 4 miles and we were still struggling to make the steep approach and get it stable.

elandel
16th Aug 2001, 15:37
As a TC person I'd better jump in then. Firstly at TC we do not have any technology apart fron the four or five times table (thanks CP) to work out your distance from touchdown.
We give it because we are required to, once on initial descent and again on handover to the No. 2 director (120.4)- the latter should be more accurate.
In defence of our foreign colleagues, the Heathrow pattern is well established and because of continuous descent approaches, you will usually get a distance of 20 - 25 miles from initial descent from min stack.
I assume other airports dont have to conform to the ridgid rules laid down for us.
Hope this helps. :)

411A
16th Aug 2001, 18:59
BmPilot21--
Very simple solution, simply TELL the Madrid controller that you must reduce speed, if it looks like the plot will not work out and you are kept high. If you say nothing, how are they to know?
Has worked for me many times. If you should land long and overrun (for example), you could hardly tell the Board of Investigation that...the controller made me do it.
Speak up if you don't like the situation.

mutt
16th Aug 2001, 20:55
BmPilot21,

In the case of LHR, could it have to do with the fact that they have a vested interested in you conducting a constant descent approach??

Mutt.

Stan Woolley
17th Aug 2001, 14:06
Bmpilot21

All these local anomalies are fine -once you know what to expect!For example for MAD R33 I always plan from the SLP to a point three miles west of Perales VOR, if they make me go to PARLA then change it and go V/S.Some guys leave the whole arrival in but put in a hard altitude lower than normal somewhere on the arrival.

Nice is another place you occasionally just have to shake your head in disbelief and say NO Thanks :rolleyes:

I was in MAD last week and I said to the FO that the UK controllers would have a heart attack with some normal ops there, especially on the ground, where I use all available lighting! I enjoy it though, you can't afford to snooze thats for sure. :)

CRP5
17th Aug 2001, 16:43
Why not try ARN or FRA they both give track miles to run as well as GVA (on a Good day) LYS and others, also experienced track miles to run in MAD! Your argument does not stand up, in a place like MAD always compute the worst case scenario, if you end up well under the profile well so be it , better than doing a rushed approach followed by a go around. :eek:

fly4fud
17th Aug 2001, 20:32
oh, you get track miles in ZRH as well. Well, I guess they have to, as they will keep vectoring you around to no end (ever done the Black Forest 1 arrival?), all to suddenly tell you "blubair 123, 25 track miles, is that good enough for u?". As your still at FL120 u would worry, but, flying the split a.. mini 4 holer, just open up and dive for it :D

Paturuzu
17th Aug 2001, 21:28
Amen Fly4fud!!
That's ZRH.I know that,but hey,you get your track miles and they always ask u if that's ok for u.99% of the times we say yes!
Cheers. :eek:

Bright-Ling
17th Aug 2001, 23:53
As elandel says, there is no special hardware for working this out.

Basically - you are taught a way (by CP!!) that is really easy:

1. Find an a/c on the final approach at the 10-15 mile mark.

2. Then add up in 5's - as a 3 mile spaced aircraft will catch up one mile going downwind to base (and reducing speed to 180) and one mile on the closing hdg (and speed back to 160/170)

3. Obviously, if there are a lot of heavies then they need 4 miles so some add up in 6's then. But if there is a mix, it is easier to just add up in 5's!! (my 5x table is better than addin a few 4's, a couple of 3's, a 5 and a six!!!!)

Interstingly, a lot of the experienced controllers went to the Air Traffic Management Development Centre recently to conduct a trial with a new computer which works out miles and helps get the aircraft off the stacks at the right time. EVERYONE was proved to be UNDERESTIMATING this range from touchdown! Still at trial stage though!!!

Hope the range is given correctly, as CDA's are becoming increasingly important at LHR.

Ranges should be given when handed over from No 1 Director (119.72/134.97) which is an estimate as the No 2 will fine tune and will give a more accurate range on first contact. That is why they may be a bit different before you ask!!!

-----------------------

B-L

Oliver James
18th Aug 2001, 01:50
Evenin'

I believe another of the reasons we concern ourselves with ranges is so that we provide a good service to you flyboys; it helps you to know where you are and what you need to do in order to achieve a good descent profile.

Having been invloved at the ATMDC I am able to pass on a little bit more: One of the tools we are working on is SASS (Stack Advisory Support System). It uses the landing order, known speeds (corrected for TAS), wind data and "standard" tracks off the stacks to compute stack departure times. They are VERY good. Once off the stack the time changes to a range which is computed from the same factors. The ranges count down as the aircraft gets closer.

An interesting point has come up in the development process: If your track to touchdown is 24 miles long and have a strong tailwind for a significant part of that track then, because your groundspeed is high, you spend less TIME in the air than if there were no wind at all. The question is therefore, when we give you a TRACK mileage to run do you assess what the wind is when you set up your rate of descent? If not, how do you know what rate to set up? Would you prefer to be given AIR miles to run?

This piece of kit is very good, to the extent that it will "regularise" the intermediate approach and reduce much of the doglegging. It is also less likely that we will miss the correct stack departure which means there will be fewer occasions where we chase the approach, which will reduce the chance of a rushed approach. It therefore enhances safety.


Twenty point four. :)

[ 18 August 2001: Message edited by: 120.4 ]

Christopher James
18th Aug 2001, 02:00
When do we get it?

09L :)

Oliver James
18th Aug 2001, 13:41
We are waiting for a dynamic wind input which both SASS and FAST need for accuracy. Also SASS has to be NODELised and technically scrutinised before it can go operational so I believe the time scale is late 2003. Pity really because it is a most desireable piece of kit.

point four

[ 18 August 2001: Message edited by: 120.4 ]

BmPilot21
19th Aug 2001, 15:29
Sounds great, point 4. You alreadt to a good job, so anything that enhances that and reduces stack times has to be good. The only thing I can see, is that the computers will become so accurate, but pilots won't! For instance this will rely on '160 to 4', but obviously the exact time that people slow down varies - some start to slow down at 4, others at 5 etc.

This also leads onto your other question - I don't take too much notice of the wind UNLESS there is a tailwind, then the alrm bells start ringing and we try to slow it up and get down ASAP, as they can really screw you up. So, we will generally slow up a bit before 4 dme if we have a tailwind. If you could accurately give AIR miles to run, that would be brilliant! That would make things far easier.

burp
19th Aug 2001, 20:02
The next SASS trial, due in September, has been "postponed" for around six months.

B.

Oliver James
19th Aug 2001, 23:20
Yes, that was correct but I know that things were constantly changing at the ATMDC last week. My understanding on Friday morning was that they decided on November, using the dates previously set aside for the Gatwick FAST trial, but can't swear to that.

I will pass on the info about airmiles rather than track. Thanks for the complement! :)

BmPilot21
19th Aug 2001, 23:53
Responding to CRP-5, yes of COURSE I plan for the worst case, and if left to my own devices would have no problem with a shortcut - it gets us on the ground quicker, uses less petrol etc.

This happened to me yesterday:
They make you start descent early (up to a hundred miles) down to say 270. This interrupts briefings etc. if they're ongoing, and costs more fuel (I've now learnt to get everything done VERY early).
They keep you at typically FL200-270 until you are high so you have to ask for descent :The usual reply:
"Contact 123.xx for further descent" You bring the speed right back to reduce energy.
A minute later the new frequency gives you a descent of just a thousand feet - not enough time to increase speed or use the speedbrake. You're now well above the profile: "request descent"
"Standby, or contact the next frequency". This maybe happens several times more with small step descents.

Eventually you get a decent descent to an altitude, but you may be approaching 10000', and getting close to the localiser, so the chance to increase the speed to 300 kts against speedbrake is limited as you want to be slowing down. In the meantime each controller cuts the corner more, vectoring you eventually to the centrefix. And as the saying goes, "you can go down or slow down, you can't do both"! You don't want to ask for repositioning as it costs time and fuel, and you may lose your place in the landing order, so you give it a go. Yes, we were stable by 500', but only just and it was so unecessary - the same doesn't happen in the UK, so why in Spain / Italy?

Fair enough if its due terrain, but each controller doesn't seem to co-ordinate with the next one, and none seem to understand that jets can't do a steep approach at 250/210kts and make a comfortable profile. None seem to attempt a constant descent, ideally intercepting the glide at 180kts from very slightly below it.

Yes, I enjoy the challenge in some ways, and it certainly keeps it interesting - in a lot of ways it was good fun. BUT it leads to an unecessarily high workload on the flight deck with PF shouting for flaps/gear etc, usually having to fly manually as the autopilot will not hack it. The PNF is trying to talk to numerous ATC frequencies, read checklists, ID navaids, plus work the MCP panel as the PF is hand flying. Plus you have rapid high speed descents into possibly terrain critical airfields (Milan?) - the capacity to monitor everything is less and the potential for error is increased due the high work load. The approach is unsatble up until 1000' when it should become stable (ideally), plus a much increased chance of a go-around if it isn't (or isn't going to be) by 500'.

That's what I don't like, and there isn't a lot you can do about it except ask for repositioning, more track miles etc. which is unpopular, causes delays, uses fuel etc. etc. I will do this in the extreme case if it's obvious you're not going to make it, but its usually marginal, so we normally give it a go and make a successful landing. However, it does lead to the much increased workload as I said above.

Oliver James
21st Aug 2001, 00:16
An addendum to my last.

The reason we currently underestimate mileage is because when we say TRACK miles few of us have taken account of the wind and so the figure given is really AIRmiles.

As was pointed out by Bright-ling we have always just added up in separation plus catchup with no serious allowance for the wind. SASS takes full account and even corrects IAS for TAS in its calculations. Last week's trials showed an insignificant difference between the SASS estimate and the actual mileage flown. If it seems more appropriate to the crews to give airmiles it is easily done, its just that the discrepancy has been picked up by BA before. It seems likely to me that if we give you true track miles more aircraft will level off. :)

[ 20 August 2001: Message edited by: 120.4 ]