feeder fix time/ required time of arrival (RTA)
 

Quite often ATC will specify to cross a waypoint at a particular time.

How accurate must the aircraft be crossing this fix ?

Is within +/- 30 seconds good enough ? (considering that our timepiece only needs to be accurate to within +/- 30 seconds)

Some pilots aim to cross exact on time using whatever thrust/speed brake to make it happen whilst others happily accept anywhere within +/- 30 seconds.

Any ATC care to comment ?

just a pilot but..
 

Depends on what equipment you are on. Dare say they expect the 320/73 guys to be pretty accurate (GPS Clocks).

I try as hard as I can to meet their request and if it looks as though I can't let them know. It kills the fuel savings and is annoying when they give it to you 1 second after top of descent. I do try to keep in mind how understaffed they are and thus don't ever complain.

Find most are quite appreciative if you help however/wherever you can.

Computer Derived Threshold Times will be accurate only if the captain throws the computer out the storm window as he overflies the threshold in the go-round after being too intimate with the aircraft in front.

My bad forkie!

Bet your machine has better stuff in it than mine any bloody day!

The times are designed to give a specific distance between a/c; ie 10nm, 15nm etc. Ideally everyone would get it perfect, and it would all work. However, pilot preceding may be +30 seconds, so pilot following, although spot on time, will need to slow down/ be vectored to meet the required spacing. Add to the mix differing a/c types, speeds and altitudes and there are just too many variables for it to work perfectly every time.

I always assumed that it was the same as leaving a holding fix. On time to 1 min early.

As I typed this I realised how involved it can get depending on Duty runway,traffic mix, and acceptance rates at SY. This is just part of my perspective as a SY arrivals North controller.

ATC are allowed a tolerance from the SY flow of +/- 1 minute on the feeder fix time, i.e Cross Boree/ Yakka at time XX +/- 1 minute. How this tolerance is applied by the arrivals sector can cause headaches for Sy Approach or make it run smoother. Remember this is the ATCs tolerance, not the pilots.

We are planning on the pilot getting it as close to the time as possible. Appreciating that the winds are not always as forecast, and this may throw things out for the FMS.

From the North of SY the jets are usually STAR'ed to go through Boree, and the turbos through Yakka for the Calga STAR. Domestic jets from the North when on 16 or 34 usually are programmed for the shorter runway 16L/34R on the Eastern side as this fits better with the traffic from the South. They will fly to the East and southern arrivals to the West. It makes sense.

Heavies B747, B777, A340, A380, International A330,etc are programmed for the the long runway 16R/ 34L.

The flow system we use computes a landing time from the feeder fix to fly the usual approach path to the runway and and computes backwards. i.e. if the aircraft is going to land at time XX they need to cross the feeder fix at time YY. i.e XX minus the approach path.

What the computer doesn't allow for, to the Arrival controller, is spacing . It does not show the first 2 minutes of delay to the Arrivals controller as it assumes the SY approach controller can stretch them in the terminal area. The arrivals controller can work out whether you can shorten the aircraft up or lenghten them out to work the best sequence into SY, according to the flow.

When we have the mix of jet aircraft for 16L/16R or 34L/34R, MAESTRO (the acronym for the flow tool) doesn't differentiate, it displays that the aircraft for the differing runways need to go through the feeder fix (Boree) at the same time. This is when it gets interesting. Our display can give us feeder fix time which shows the MAESTRO order, and at the click of a mouse, also the runway view which shows us whose landing first. We can then assess who we will make No.1 and No.2,3,4,5, etc through the feeder fix and adjust the time/ spacing to suit.

Depending on the mix with the turbo props , we can also send the domestic jets down through Yakka for the amended Calga STAR to make the sequence work. We do appreciate that domestic jets don't like being pushed down low on this STAR because of the increased fuel burn but we are endeavouring to make the sequence work. We can't send them down the Calga track if we have the slower turbo props as the jets eat them up on descent. ( Personally I love the Dash 8 D's, they hold their own and more against the jets).

When you get the situation that MAESTRO is telling you to put 4 jets through BOREE within 2 minutes (roughly 10-12 miles) , you look at the RWY view and work out the order that they need to be for landing. You then might make the front one a bit earlier and the last one a bit later and hand them off 10 miles between each to SY approach, they then have something to work with.

Also, there is no use in using your +/- 1 minute tolerance to SY if you allow your turbo-prop through Yakka to be 1 minute early and your jet through Boree to be 1 minute late when SY are sequenced to have the jet landing before the turbo-prop on the same runway.

The upshot of all this.
Please get as close to your feeder fix time as you can, and when we muck you about even though you have done everything right in meeting your RTA, it is probably because someone in front ( reduce further/ turn right or left) or someone behind (increase now to 300kts/ track direct to ZZ and buggering up your profile), or maybe me, has stuffed up the feeder fix time.

When you get the "Track to direct to Boree/Yakka , maintain max speed cruise and descent, cancel speed restriction below 10'000ft" We want you to go for it!

P.S. I am always bemused on the very rare occasion that a pilot complains about being held or vectored, that they think I or my colleagues are enjoying holding or vectoring 10 or more aircraft when we could be giving them direct feeder fix/ unrestricted descent and getting them out of our airspace. Anyone who flew into or north of sydney the last 3 afternoon/ evenings will know what I am talking about. Have a nice day.

Not having a go at props just a question or two
 

max1,

From an ATCers perspective would it make much difference (or negligible) if props and jets went to respective airports. For example PH seems to be one of the worst. But you have a look at the variety of types in and out and think "well its no wonder!".

How come we get make max speed to the field shortly after Top of Descent? Or worse - min speed. Having said that max speed seems to be the one that gets handed out the most.

With regard to the feeder fixes I usually manage to get there within 0 to 0.2 of a minute. At what point would the controllers like to know 0.4 0.5?

When you ask for say 220 knots do you want it asap (as in manually intervene V/S speed brake etc) or just slow as the FMC would do it?

Just a couple of things I'm often wondering..

Wondering the same thing. In the Q400 on a 3 degree descent at around 260-270kias, if we get told to slow down to say 220-230, it's going to take a loooong time unless we back the descent off.

They'll slow down or go down but not both! :E

This stuff you wont find written anywhere...
 

And while we're asking questions,

When STAR speed restrictions are cancelled, but without any other instruction (ie max speed to the field, reduce to 250 kts etc) does that imply that you WANT us to go fast? Or does it mean that you dont really care either way if we speed up or stick to the speed limits?

Of course given the option and conditions permitting I'm willing to bet most would open the taps :ok:

Yeah mince I've wondered that as well.

What about this. 250kts below 10,000. Is there a 10kt buffer either side as with other speeds? Some guys I fly with say yes others no. I go for 250 no buffers just in case.

If you cross a fix a minute early (as allowed) you'll more than likely get a vector or an earlier than usual speed reduction to 230/210kts etc (for sep or the sequence).

If you are doing 260 kts when you were asked for 250, you may get a vector or a further reduction to 230kts.

You can trust a Boeing to cross a fix at a stated time, you can NEVER EVER (EVER) trust an airbus to cross a fix at a stated time (or meet a level requirement). Airbuses get you stood down, Boeings are trustworthy.

Eeeeerrrrrr ---- Aaaaas long as you don't fall ( or "plummet", the media preferred technical tern) out of the sky doing it, as did a BA 747 over Turkey a little while back !!!!! True story, all graphically witnessed by the QF1, about 4nm behind, and 4000 lower.

Times when I wish I had had a camera, No.5791.

What is known in the trade as having a "Nigel" as an F/O, when the Captain is having a quick leak.

Tootle pep!!

RTA function.
NOTE: Arrival time control performance will be ±30 seconds when accurate forecast winds have been entered and the airplane is not thrust or speed limited

Although intended to be used on weigh points at least 1 hr down track, they will do the job as described above, even at relatively short notice.

I am always bemused by the fact that we can take off from a capital city, fly several hundred miles, at a time and speed known to ATC, only to be told in the last few minutes of cruise that we need to lose several minutes or hold. :ugh: As though we all magically popped up from nowhere. :ugh:

Most of us are too busy muttering expletives to complain on air.

You may not have magically popped up from nowhere but the aircraft that departs from a considerably closer aerodrome did. Giving delays a long way out (as per ALOFT into SY) works well when the arrivals are well known and orderly but once things get busy and less orderly it becomes harder to manage.

You might be able to lose 18 minutes flying PH to ML but we then have to get you through the six aircraft holding ahead physically but landing after you. Far easier and safer to do it first in first out.

Also once you've lost that time there's no way to make it up if the sequence changes drastically such as LAHSO becoming unexpectedly available. Fabulous, you lost your 18 minutes. Pity that in the end you really only had to lose 6.

In the end, yes your magic box can work miracles, unfortunately the magic makes no allowance for the other 53 aircraft doing their own thing too. You're just as likely to run up the @rse of the guy ahead because you chose to lose the time on descent and he was doing it in the cruise. Until all that can be coordinated it's down to a decidedly basic box of tricks called me!

mince, generally it means it's optional & that you can continue your current speed below 10. If we want high speed we'll ask for max or nominate a speed. If you feel the urge to floor it then ask.

Personally if I'm not fussed I'll just say "cancel speed restriction". If it's to retain spacing in the sequence I'll say "cancel speed restriction, continue current speed".

Mr. Hat, it'd actually work better based on speed inside say 30 miles than type. A turbo-prop will run an Airbus down any day - not knocking the bus just that they're often slow down final.

We know that giving you speed changes once you've commenced descent is a pain but the sequence is a dynamic beast, particularly when many aircraft are nominally arriving at around the same time - a small change can shuffle the sequence significantly. There are a myriad of things that cause this.

A couple of aircraft who clearly have incorrect estimates (say a turbo-prop is grounding 20kts faster than expected or an International heavy is on an early descent & has already lost three minutes). We try to allow for this but sometimes we guess wrong. Sometimes these things get spotted later than is ideal because we're busy separating.

A heavy has a rethink & decides he needs a longer runway, or the wind picks up a bit & is too much for the guy we were sneaking onto a different runway ahead of everyone. Conditions improve and we can shorten a few up, opening the sequence up ahead of you. Or vice versa & we have to wind the acceptance rate out a bit, as well as allow for the loss of track shortening. Etc.

Wouldn't these be RPT with a known schedule.

It could work miracles if it were allowed to. RTA + - 5 seconds, efficient descents, the whole bit. Why would the 52 other RNAV equiped aircraft be 'doing their own thing'?

Unfortunately, like me it doesn't like normal descent + now min speed descent + holding + vectors + re-intercept star + max speed to the field + track shortening + cancel height rqmt + cancel speed restriction + on second thoughts slow back down to min speed; all in the one descent.:hmm: The idea of 52 other aircraft crews having this sort of schizophrenic workload at the same time, at the same place is just scary.

I recall about 25 yrs ago, going into Sydney, we were tracking Calga - Sydney for runway 16, in a light turbo prop. At around 15 nm on final we were instructed to turn left heading (about) 080 and maintain max speed.
I remember having a dummy spit ( quietly). I simply didn't get it.

I think I have a better understanding now, I understand the " merging" concept, and that we all just can't keep heading towards the runway unhindered.

I imagine how easy it would be if we all maintained 310 kits to about 20 nm and then decelerated at the same rate to the same Vapp on the same descent profile. Predictable controllable enjoyable, and then I go to Darwin, it reminds me of the iPhone ATC game.Go fast, go slow, not given descent, when it gets busy "cancel Star" and vector here vector there, you name it, they have no idea of our limitations.:yuk:

Having said that and probably upset our RAAF friends, I think most ATC do a fine job, if I wasn't a pilot I think I could really enjoy the challenge, probably more "back then" but hey, that's life.

And there are still many variables; using SY example, BTH, CB, NWA, WLM, ORG etc (will have known RPTs at times), but as you know they don't get away on time every time, some operators in the past didn't follow their departure times at all accurately. Pretty easy to get a 30 sec to 3 minute delay (or the delay removed because the CB jet didn't go on time) from somewhere to back up against an otherwise perfect sequence... Which means the whole thing is going wrong somewhere... Pigeon/Statue?

Then there are those pesky issues, such as a go-around, a medical flight, an emergency, an extra space due to taxiway congestion in an effort to get a few more airborne, weather (changing winds not scheduled, low vis etc.), a blocked frequency, unknown operational speed issue, etc. etc. If it were as simple as one follow the other etc then ATC would've been automated a long time ago.

I have also experienced FF (feeder fix) times given with 200+ miles to go getting completely bolloxed up... where speeds and vectors were needed to make it work... etc... Modern boeings seem to be more accurate, but there are also "how to get there on time" issues, go normal in cruise slow in descent vs go slow in cruise and normal on descent etc... It's not as simple as giving times and forgetting if the aircraft are a dead heat 80-120 before the fix...

In enroute we used to say "nail the first, stream the rest"... Which is easy when it's your stream, but if APP/DIR are merging arrivals alternatively from North East and West then what happens coming through RIVET etc is totally irrelevant if if the ones coming from the other ends aren't where they should be etc... I'm sure you'd rather comply with speeding/up/down as needed too to keep SY at 80 movements an hour rather than 75 etc... because everyone knows an airport not working at capacity isn't working... (let's not discuss political movement caps...)

PS you could fix almost everything if you went the European way and accepted delays in the holding stacks and on gates or airfield parking bays and forgot all about slowing down enroute, except for separation... I think the Australian way is much more 'efficient' even if pilots don't think so. Pilots don't seem to complain over here maybe because it's busier??? The reality it isn't, the busy bits are no busier they just last longer.

You need to get out a little more Joe! Out of your cockpit, into a TMA and watch what goes on. And not at a bull**** time of the day (unfortunately you'll only get in there when it's nice and quiet, PR have control of these now :ugh:. You need to get in there when it's busy.

I find that I have to be pretty proactive to achieve the fix times.

RTA in my machine works but does things that would work ok in a sim but in real life is a case of the machine over estimating its ability to handle turbulence and big wind changes. The speed bug sitting suddenly on MMo and then 1 knot above up/green dot speed is an example of RTA in my machine.

Personally I opt to not criticise as I don't have the full picture. I can say however a controller palming me to another frequency for further descent as I'm about to capture an altitude at high speed is very very annoying and is very uncomfortable for everyone on board. It seems also enroute to Perth from the east coast that the clearance seems to arrive a bit later than it should and we end up all arms and legs when its not what we expect.

Other than that I've accepted that when you fly along the east coast expect the worst.

One other thing. Max speed into say Gold Coast or Launceston doesn't work for Jets as the profile will bust just about every CTA step there is so why give it? Send us on a vector rather than put the workload to that level..

Mr Hat, I don't get why a high speed descent would give you a shallower descent profile, I.e. Busting CTA steps?
I am guessing a bus?
Does it build in a long slow down level segment, if not I would have thought high speed = steep descent.

No was saying high speed=steeper descent and it clips the steps at the end (say last 45 miles). Box says shallower profile for slower speeds (no step problems).

The steps in these two locations in particular don't work for higher speed descents is what I was saying.

Mr. Hat, sorry but does not compute. If you're higher & on a steeper descent how can you end up clipping steps that are under a shallower & lower profile? It only makes sense if you're ending up being lower further out on a steep profile....

So you're saying you're happy to lose a stack of time en-route on the off chance everyone departing from closer aerodromes gets away exactly on time?

You also need to get your head around the idea that times at fixes doesn't separate you from other traffic. All this you beaut automated stuff works wonderfully well when you're on your own but is ****e when there's other traffic in proximity.

Ah I forgot to say that this is a problem mainly when we get the cancel speed below 10,000 ft + make max speed to the field (i said it in my mind couldn't you hear me:ooh:? )

The 250/10000 ft shallows us out but when we take it out we run into trouble with the steps. Increases workload significantly where the steps are tight to begin with. I'm not spinning you a yarn i promise! Just my experience with it.

Ah, makes more sense. Push nose down to gain speed & whoops, there's a step.

Mr Hat
Personally I see airports as a vital piece of infrastructure, Farmer Bloggs coming in from Moree on a Dash, should have the same rights as Holiday maker Bloggs on a jet from Cairns, to use SY airport.
I won't go into the politics, there are far too many people making an industry out of that conundrum.

I read (somewhere) the other day that there are very few major airports that don't have parallel runways, we just happened to 'blessed' with a few.

Some of the cavalry have arrived to discuss points on this topic. I would urge any pilot who is interested to visit a centre. We get the rare frustrated comment about what is going on.

As regards to RTA, under radar we have a fairly good idea about who is trying to make good their RTA and who is taking the liberty of bullsh!tting. The vast majority of domestic pilots are endeavouring to get it right, and thank you. We also have some internationals, especially in the morning, who we watch like hawks. The SY flow are also adjusting the sequence based on the actions of the odd domestic and some internationals.

The joy of having some international carrier advise 3 minutes (15-20 miles) from the feeder fix that they are negative PRM, relaying this to the SY flow, and dealing with the fallout and revision to the RTAs is an interesting experience that I recommend to no-one.

As others have said, the sequence is a dynamic beast, the jet out of Canberra gets away with a 25 minute flight time. The jet out of Port Macquarie had a 37 minute flight time and held for 50+ minutes on Monday due to storms. As we sat there with 4 holding stacks going, I mused why the hell did they depart? Shouldn't someone have told them?

I see some press blurb about a project with lots of shiny suits patting themselves on the back because the SY-KLAX flight got unrestricted climb to cruising and direct tracking thereby saving the airline XX tonnes of fuel, I think we try to do that everyday.

I then look at MAESTRO as everyone is getting held into SY for 10+ minutes due to noise sharing, times that by the 15 aircraft that I can see, and think there's that fuel and then a fair bit more, plus all the poor buggers that are waiting for Farmer Bloggs from Moree, and Holiday maker Bloggs from Cairns to land, so they can pay their parking fees and get going. 40 on the Dash, 110 from Cairns. Thats a fair bit of excess parking, even given that not everyone is there to pick up just one punter.

Understood max1 thanks for the reply I read with much interest.

I suspected all along that those times were to be adhered to as best as possible. Am happy with my 0 to .2 at a maximum tolerance.

le Pingouin, if programmed from before top of descent it just stays steep until a deceleration segment (simplistically put). Normally that happens at 10,000 and its shallower thereafter. If the cancel speed + max speed happens after top descent generally the profile says your says something like 4560ft low and the power comes right up till it intercepts profile and then dives at idle. Either way certain ports have airspace that make the workload go ballistic should the crew opt to take the max speed below 10. Personally I've learned which ones do and don't and limit it accordingly.

Feel free to tell more. Its interesting to me. Gives me and others a bit more of a picture.

keep it up max - great reading.

may even be a Chairman's award in it for you! :ok:

Dizzy Llama,

Or more chats from mangement?

Most of what max1 says goes for PH as well, without the noise sharing (thankfully), the parallel rwy and MAESTRO.

PH, I think because we don't have MAESTRO, has slot times. All RPT operators submit schedules the night before, a sequence is worked out and landing times sent back to the companies. Some days it works better than others, some days it doesn't work at all. Unfortunately, we never go back and look at the days it doesn't to see if anything can be learned.

A few issues. If you are on the same route as traffic immediately ahead/behind in the sequence, separation becomes an issue. For example, two jets, same route, same distance. #1 issued with a FF of x, calculates profile cruise, slow descent. #2 issued a FF of x+2, calculates profile cruise, slower descent. Now the top jet can't have descent until the distance opens up to 5 miles, the distance won't open until there is a speed difference, and there won't be a speed difference until they are on descent.

Another, for PH anyway, is sequencing prior to radar. If the flow waits until all the traffic is on radar to calculate the sequence, you will get significant delays at only ~120-140 miles out, so the sequence is now done further out and based on pilot estimates. (As an aside, PH ATC cannot see ADS-B.) Pilot estimates only have to be revised if they differ by 3 min or more. It's not unknown now for us to issue a fix time the aircraft can't meet because its now earlier than possible.

Additionally a lot of aircraft struggle to get +/- 1 minute, particularly if the winds are bad. In a sequence of 20, even an average of 5 seconds late adds up, and sod's law says the early ones never balance out the late ones.

Is that assigned A100 from ML Centre and then call PH APP for further? It is poor technique, but sometimes its quicker to tell you to call rather than coord a lower level with PH and then give it to you. What should happen of course is that you are transferred to APP before you need further descent. I was taught that arriving aircraft should never have to ask for descent. I have to confess I never knew leveling out on descent was a workload issue, I'll bear it in mind. We really do have very little understanding of how things that affect pilots unfortunately.

With regard to speed reductions and tolerances, we only see a radar calculated groundspeed rounded of to the nearest 10 knots. The speeds we issue tend to be 'suck it and see' because we issue indicated speed to control goundspeed. If you are doing 255 IAS instead of 250 we wouldn't know. If you are still catching, we'll slow you down more.

Re. having to maintain when on a high speed descent. Sorry, but sometimes sh!t happens. We try not to let it but the hand-off process isn't automatic - I have to initiate it & the next controller has to accept you. All it takes is me being busy & starting the hand-off later than is ideal & him being busy so slow to take the hand-off. I can't just assign a lower level in someone else's airspace without their say-so, so you maintain. At least you that way you don't hit anyone.....

Unlike you I'm not staring at the one aircraft ;)

No magic about it, simply other, possibly much smaller & slower aircraft departing from aerodromes within 20 - 30mins flight time. Could make an even bigger difference if your destination doesn't have capital city priorities.

And seriously, what would your complaints be based upon, or hope to achieve?

TBH, known schedules mean nothing at the destination end. It's only actual times that have any bearing.

As for feeder fix times, +/- 30secs is workable so long as all other aircraft are that accurate, and fly expected speeds (and therein lies the crux). We regularly have an international MD80 series operator that can take anywhere from 9 to 15 minutes inside 40nm. Unfortunately we have no idea if today is Capt. Slow or Capt Quick's leg until well after the sequence is determined.

If you are early, just don't be surprised if you score a few extra track miles or further speed reductions. Likewise, if you're late, you might get asked to increase above normal profile speed.

Me too, psycho joe.

Can one of you guys tell me what descent speed above 10,000' you expect from RPT jets? A few years ago it was 300kts, but I have been told recently that it is now 280kts.

At EK we are expected to fly 'econ' descents & I have seen as low as 258kts & as high as 285kts on the 777, depending on weight & forecast winds. I imagine that this sort of speed variation would make the controller's job a little difficult to say the least so, when flying into the airports in Oz, I used to always program a 300kt descent above 10,000'. Now I am not sure what is required.

We also use the FMC default 240kts below 10,000' unless given a specific speed to fly.

Hi Max1
I did tell the pilot of the Port Flyer that there was significant delays verging on 1hour and would he prefer to take the delay on the ground, but the pilot said he'd get airborne and take his chance.

All the fun of the fayre but without the goldfish on monday.....

Rb