Conditional Descent Clearance'a

[SPEEDBIRD5FP]

This had always been a topic for discussion for the place i work.
If, for example, you were flying to Stanstead from Dublin. Head to WAL then Lorel STAR into stanners. Descent clearance is usually FL200 20nm b4 clipy then FL150 by Clippy then further to 130 etc towards Barkway.
My question is this. Once youve been given 200 20 b4 clipy then your given 150 at clipy does the previous restriction still apply, On a quiet nights in london i asked a couple of controllers, got different responses. What are your thoughts??
Thanks a lot
5FP

[radar707]

The official libe is that once a new clrearance is issued, then unless the previous restriction was repeated then it no longer applies.

From our point of view there are often a lot of standing agreements which is why we have be level or below 20 before etc, so it would be nice if you comlied with the restriction anyway, or if you were a bit unsure then just asked "do you still want us FL200 20 b4 clipy?"

[Smokie]

I have had similar into LGW, "cleared FL200 75d before MID." Then re-cleared "FL150 50d brefore MID" this is a big bone of contention in our Airline, with various Training Captains (Chief ) included.
I have asked ATC on the day when on a Line Check with Training Captain in the RHS. ,
ATC response was that the last clearance is the "Legal and over riding one".
Unless there was a precondition, ie, "but still to be at FL200 75d before MID. "

Also a similar article appeared in a CHIRP edition a few years ago saying the same thing.

Air Traffic, any help on this one from you guys ?

[LostThePicture]

A restriction on a descent clearance "Descend FL### and be level by (POINT)" is usually applied so that an aircraft is in the right place, at the right level, to be transferred to another sector.

In ATC circles this is a "standing agreement" and is great for us as it enables all traffic inbound to say, Gatwick, to be transferred to the next sector without the workload of having to make a phone call as coordination.

So if you're cleared FL200 level 75DME before MID, then we expect you to make that level by that point. As you're approaching the level, you should expect a frequency change to the next sector receiving you on that standing agreement. So, they give you further descent. As 707 said in his post, if the restriction you were given previously is not restated, then technically it is cancelled and you do not have to comply with it.

I know of no controllers who would restate the restriction after giving further descent; the new instruction would probably mean that your profile would come pretty close to complying with the original restriction anyway.

A major commandment of radar control is "thou shalt not throw an aircraft to another frequency unless it is 'clean' (unless thou works at Manchester ACC :D )", i.e. you pilots should be assured that when you're instructed to change frequency, you won't hit anything that's still in the sector you've just been talking to (and you should hope so too). The point is, if the next sector gives you a clearance which doesn't include a prior restriction, then the previous sector probably doesn't care.

Most standing agreements also build in a little bit of a buffer zone to allow for unforeseen circumstances, such as a flight having to level off due to other traffic, pilots taking the *!?%, etc. So if you inadvertently miss it by a couple of miles, you probably won't annoy anybody (much). But then you wouldn't do that to us chaps on the ground would you? ;)

Hope this answers your concerns.

LTP

[GroundBound]

This question was raised before in this forum, and revealed a mixture of replies from (UK) ATC - some expecting the previous restrictions to be complied with, some indicating that the restriction need to be repeated if it was still applicable, and some "expecting" that it would be complied with through the natural profile of the flight. It also included a "lively discussion" between controllers about the contents, correctness, and interpretation of their own Ops manuals. The discussion also related to not repeating the previous restriction because of the frequency loading.

What concerned me then, as it does now, is that an ATC clearance should not be "interpretable" depending on the country in which you are flying.

I believe, as has been said here (so far) that a new clearance replaces a previous clearance, and that any previous restriction must be restated if it still applies.

It still bothers me that there appears to be some doubt about this, and that this always seems to relate to UK ATC examples. So, are such clearances used elsewhere, and what is the expectation in those locations?

[PPRuNe Radar]

What concerned me then, as it does now, is that an ATC clearance should not be "interpretable" depending on the country in which you are flying.

It is crystal clear and not open to interpretation in the UK ATC Manual (the MATS Part 1). The restriction is cancelled by any subsequent clearance unless restated. Those who choose to 'expect' pilots to still comply without restating a restriction they require are possibly setting themselves up for a fall. They will have NO ONE to blame but themselves, regardless of any excuses such as 'the RT was too busy'.

As another poster said, most people with a bit of experience will issue the next clearance without a restriction because they have assessed that the profile will be met without the need for it to be restated. Or they have the comfort of a little buffer zone which they decide to utilise. If things are tight against other traffic in the offering sector (with separation being achieved by use of the restriction), then the 'clean transfer' procedures would ensure that the controller hangs on to the traffic until the separation was achieved or would contact the receiving controller to agree an alternative plan.

[Phoenix_X]

As another poster said, most people with a bit of experience will issue the next clearance without a restriction because they have assessed that the profile will be met without the need for it to be restated.

The danger there is, if (like at Manchester) the restriction puts the a/c well below the optimum descent profile (sometimes up to 8000'!). This is, for example going into LPL from AMS, when given FL170 or below by Goles.

When the new clearance is issued without restating the previous, then the 'assessed profile' mentioned above might well change instantly when the pilots decrease their descent rate to minimum (500fpm in UK?) to recapture the optimum path!

[PPRuNe Radar]

then the 'assessed profile' mentioned above might well change instantly when the pilots decrease their descent rate to minimum (500fpm in UK?) to recapture the optimum path!

That's where the experience behind your assessment comes in ;) I think most Boeings for example would go to around 1250 fpm descent rate until the profile is regained.

[Phoenix_X]

The automatic mode will level off :).
Most pilots will reduce to 1000fpm but some even 500fpm.

However, I see your point about experience, once you've seen it many times you can estimate it accurately. But it's still a very sore point that's not as clear as it should be...

[EuroATC]

I am a controller and have worked in Toronto ACC, Geneva ACC and now I am in Bahrain ACC. Alot of controllers including myself are no longer using restrictions. What I use is rate of climb and descent. If I need you to get down by a certain point I choose a descent rate that will get you there. I have been burned way to many times just by giving a simple restriction ie: "descend to FL270 reach 30 nm before torino" .. and still I have had aircraft 2000-3000 feet high. I agree some instructions are not always clear... now my standard... "descend to xx, min rate xxxx".

[eyeinthesky]

The 'Descend at xxx FPM or more' or 'be level in y minutes' are the bain of our lives at London because we get them all the time from certain watches/controllers at Maastricht. The flaw in them is that they are based upon an assessment of the traffic's performance at high level, and take no account of changing TAS or G/S in the descent. Often the traffic goes in high. The 'level 15NW of COA' or whatever we have as a restriction is to keep traffic out of S13's airspace and it can be embarassing if the assessment is wrong. Most of the pilots I have asked say they would prefer to be given a point by which to be level, and let them work it out.

I must confess that I used to be one of those who assumed a certain amount of common sense, especially amongst our home-based airlines who fly the routes regularly, and expected that they would comply with previous restrictions on the way to new ones. Since the exchange on here, however, I now restate the restriction if I think it is necessary. The wonders of PPruNe, eh?!

As an aside, I don't think I'm alone in the following:

Say I give you an intermediate descent: "Descend when ready FL310, expect FL250 by LOGAN". This will be against other traffic. If I then step you down in stages to FL250, I would expect you to make FL250 by LOGAN without me NEEDING to restate it every time. You were given the restriction in the first clearance. If of course the stepped descent has meant you CAN'T make it, then I will remove the restriction and place a new one (e.g. expect FL150 by SABER).

My point is that I don't want to take up R/T time by repeating restrictions in every transmission. You are professionals and I think it is fair to assume a certain amount of nouse!

[PPRuNe Radar]

Say I give you an intermediate descent: "Descend when ready FL310, expect FL250 by LOGAN". This will be against other traffic. If I then step you down in stages to FL250, I would expect you to make FL250 by LOGAN without me NEEDING to restate it every time. You were given the restriction in the first clearance.

But an 'expected level' isn't a restriction so you haven't actually given the pilot one ;)

[BOAC]

PROBABLY the FIRST time I've heard it in several years of flying (wonder if he's a Pruner reading this thread?!), but inbound TIMBA 2E this afternoon, (BA2891 ex Krakow) standard "200 at ERING", recleared "130 by TANET" before we got to ERING......and..........."be 200 or below by ERING".

So clear and so non-confusing! A delight to hear. There was none of the "do you think he still wants us 200 at ERING - shall we ask him?"

I know this subject has been done to death on PPrune but it keeps on coming around :{

[MacDoris]

As said time and again any descent clearance cancels the previous one, I dont think anyone in the UK would disagree nowadays. It is the controllers resposibility to assess you rate of descent to ensure you comply with the agreement and dont end up in another sectors airspace. Eg the 75D MID restriction is to give one london sector a chance to get you below another but to do this a descent must be given thereby canceling the 75D restriction so now the clearance should go "descend FL150 lvl 50D mid, fly heading 150 be FL 200 or below 75D Mid" assuming you dont have to stopped off due other traffic. (Say that to all your inbounds during a busy period and you will find youself very short of time. (not an excuse))
Throwing lots of numbers like this at some pilots for who english is not their best language can lead to problems, the clearances such as 130 by tanet be 200 by ering are less confusing as less numbers.
The point being although we are all aware that previous clearance is canceled it really helps the sectors out when busy if you can still comply without them having to be repeated and if given an expect lvl xxx by xxx although its not a clearance its an important bit of info in planning your descent for us to ensure you stay safe and sound in the appropriate peoples airspace.
Come visit london centres and see how many level by restrictions keep you away from other sectors and their traffic.
It may not be the best system but its what we have to work with.

[StillDark&Hungry]

Following on from MacD, wouldn't it be an awful lot easier if the most commonly used restriction points all had names? Getting fed up with giving 3 consecutive TMA inbounds "Level 40 before OCK", "Level 40 before MID", then "Level 15 before NIGIT" to the third when I want them level at approximately the same place!! It would also help with the abeams!

[BOAC]

Seconded! Let's move NIGIT 14 miles back!:{

[ferris]

Firstly, it seems you guys are really having problems with your standards and checking. There seem to be an awful lot of assumptions, expectations of "common sense" etc. etc. (see recent thread about 'radar heading' as another example). Is this indicative of the system working at it's limits, creaking at the seams?

Secondly, why can't these monotonous restrictions, which are (or should be;) ) clogging the R/T be written into the AIP, or arrival, or some such thing? eg. "All a/c inbound to xxxx inbound via yyyyy, shall cross yyyyy at FLzzz, or cleared FL, whichever is higher." It's easier to cancel said restriction when it's quiet, than to state them over and over when it's busy.

[StillDark&Hungry]

Ferris

Are we to take it from that comment that you'd be happy to give someone an unrestricted descent clearance on the assumption that he will comply with a level restriction which you haven't given verbally, but that may be essential to provide seperation from crossing tracks???

hhhmmmmmm . . . . . . . . . . . . . . . . .:oh:

Now where are those 1261's??? Ferris might need a few:rolleyes: :rolleyes: :rolleyes:

[ferris]

Aaaaahhhhhhh, yeah!

1261s?????? Why? There are lots of reaallyy busy places that use the technique (I know you lot have a propensity for wheel reinvention).

How do you think SIDS and STARS work?

[055166k]

Dear pilot buddies, please bear in mind that the office-bound controllers that write out all these instructions are not the sharpest operators, and the turnover means a lack of consistency in the application and interpretation of procedures. I share a lot of what has been said ; for example a new-ish instruction for the KEGUN 1D into EGGP is "cleared FL200 level 20 miles before MONTY".........20 miles before MONTY is actually NITON, however the days of clearing such instructions through operational controllers via the now-defunct technical committees before promulgation are long gone. By the way SDH, spot on buddy!, the STAR charts show target descent points under "level planning" and in two of the cases you highlight we are instructed to issue a descent restriction which is not in accord with that published.......so much so that when a foreign pilot asked if he had to be level so many miles before NIGIT the Tactical controller said "No, be level 40 miles before..xxxxx"/////// why?......because when I pointed this out it transpires he had never seen the STAR chart!.....the controller that is! PS for BOAC, obviously a pilot because as I have said, most controllers won't appreciate your 14 before NIGIT which I am expressly forbidden to say by written order from ATC Ops.

[javelin]

So, when we come off the Ocean and head towards MAN, we get a descent clearance - be 290 abeam LIFFY or DUB. This isn't published anywhere on the arrival planning charts and is given most times but not all. If it were published somewhere it would save precious R/T time. Also, as previously stated, when handed on and given a direct, the restriction automatically comes out and the Big Bus reverts to 1000 fpm. Up 'til now I have asked chaps to maintain the rate but apparently we don't have to. I may be back to these pages in a week or so :O

[bekolblockage]

I am intrigued if the UK ATC Manual does in fact confuse the mere issuance of a lower level with the cancellation of a restriction. If I instruct an aircraft "descend to FL130, reach FL150 by X" and hand off to APP 10 miles before X, and they subsequently descend the aircraft to 8000 ft, I still expect you to cross X at or below F150. Nobody said anything about cancelling the restriction!
As Ferris says - isn't that how SIDs and STARs complement each other?

[BOAC]

which I am expressly forbidden to say by written order from ATC Ops.

055166k - can you begin to explain why?

[055166k]

Well I'll try, but you really will not believe and it is so insulting as to be completely off the scale. You will have gathered that I do Bristol/Brecon/Strumble; I suggested that when issuing target descent point we refer to the point as it is depicted on the STAR chart . The chap in the office thought that [a] pilots might get confused by the multiplicity and complexity of the arrival routes[b] controllers might get confused[c] some controllers don't know which arrival route is which and cover themselves by saying things like "standard arrival" "expect the usual" or just ignoring the process completely. This made a little sense up to the time the LOREL 1S STAR was introduced for EGSS/GW etc. , the chart shows target descent 15 before NIGIT and that is how I am ordered to say it. When I pointed out that this point was on the way to OCK and could I say 42 miles before OCK, the answer was "NO" because it might be confusing!!!!!!One thing you do learn after a quarter century in this outfit is that you can't debate a reasonable and logical point with a closed mind. Nice chatting to you, I,ve had a soft spot for BOAC ever since a fabulous day in 1971 when you chaps took me up to EGSS for 22 circuits in a VC10...ahem! a "super "actually, GASGA

[eyeinthesky]

0551166k: I agree with what you say about the closed minds in certain areas, I am constantly running up against them!

However, I suppose his/her point was that the LOREL star does not go to OCK (it turns NE well before then, doesn't it?) and in the days of RNAV the crew might well be using Lat and Long reference rather than a range and bearing from OCK. So to refer to OCK might throw them off. I have not checked the STAR and if it does go to OCK then I'm back with you that they are a bunch of idiots!

I often have this debate with people who send traffic direct to LAM and then later tell them to be level at LOGAN. Many, apart from those who know the score, will have deleted LOGAN and would prefer to be told 55DME LAM, but the closed mind scenario takes over again: 'Not my problem, they should know what they're doing!"

[BOAC]

OK guys - I see your problem; but for a simple man, why is NIGIT there, then? Why not xxx radial MID/40nm.? BTW, I DO get level 40 before MID sometimes, so obviously a rebel or two there!! :-))

[055166k]

Yes the low level STAR LOREL2L goes KENET WESTCOTT but the 1S goes NIGIT OCK VATON BPK etc. for traffic FL180+. Another stomach churning process, now fairly widespread, is the "expect level" e.g.........Descend when ready FL270 expect FL140 40 miles before OCK. This came about because several years ago a foreign pilot missed the descent point .......and of course the famous London overkill sledgehammer to crack a nut philosophy came to the fore. I don't therefore understand why all my traffic gets to the right place at the right level when I have never passed an "expect level" in my life, could it be that my long held and genuine respect for the professionalism of aircrew coupled with the fact that most of them either know the route or have read the STAR is entirely valid. On my watch we even have a chap who says"expect the usual".......talk about nonsense content! By the way I think the original reason referred to above was a result of bad controlling rather than inappropriate flight profile, it must have been difficult to get rid of a lot of height with a stonking tailwind! Good copy on your LOGAN point too, I have a practice of only clearing an aircraft direct to a point which I may subsequently use as a descent target...for the sectors that I do it might for example be EXMOR rather than MONTY for a Manch TMA inbound from the south.