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Do you know how this can happen?

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Do you know how this can happen?

Old 25th May 2015, 13:07
  #81 (permalink)  
Join Date: Jun 2001
Location: Prison Island (WA)
Posts: 1,343

Thanks for the great detail you went into with your explanation, helps us understand things a bit more.

. Which is why MAESTRO often tries to put the cheeky bugger in his F100 ahead of the 737 even though he's 20nm behind and 20kt slower).
Glad to hear that you are aware this stuff goes on. Very frustrating for us too, as we know exactly where he/she is thanks to TCAS and we all know a 737 cruises faster than an F100!

Transition Layer is offline  
Old 25th May 2015, 15:32
  #82 (permalink)  
Join Date: May 2009
Location: YMML
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Originally Posted by angryrat View Post
To the ATCer's on this thread, thanks for the great job you do day in day out. Yes I admit I've sworn under my breath at you most days but it has never been personal and is more out of frustration than because of the job you are doing(I'm sure you have done the same with me). Like haughtney I get frustrated with the late notice, however, I get it is the system and I'd rather be given the option of losing that time myself than just being sent to a hold.
Thanks, I think most of us realise we're there to provide a service and do what we can within the confines of the system and the situation at hand. Sometimes it just all goes to poo and there's little we can do about it. Occasionally we're not on our game and make it harder. And yes, you get sworn at too, although I take the approach that life is too short to get overly worked up - I have to deal with the situation anyway so might as well fix it and move on.

Whatever you guys do please don't punish us all because of one airline. By all means send planet haughtney and his airline to the hold every time they need to lose time. Please let the rest of us make the situation work and beat them on efficiency.
It's a lot easier and safer for everyone to be doing the same thing. Yes, it's possible to run aircraft through holding traffic but it's complicated and easy to screw up. Like many things, it's possible but the extra workload is a threat. That said I'm sure we could accommodate haughtney and co. if it was made known their preference was to hold.

Since the ground delay program and this airborne strategy has been introduced, I have had to do very little holding in Oz. In fact we managed to lose 12 minutes without a vector into BNE the other night and yes we could hear the doubt in the controllers voice as to whether we would make it or not. Yes we had to work harder to make it happen but I believe that we saved my company 800kgs of fuel in one sector while some others just bleat.
And that's the crux of the discussion - by necessity you take the bottom up approach of managing a single aircraft while I have to take a more top down approach of managing a chunk of a whole system. You naturally want to optimise your single aircraft while I'm driven by system optimisation and the two don't always coincide. It's just the nature of the beast.

On average that means someone gets screwed for the benefit of the greater good. Better luck next time?
le Pingouin is offline  
Old 25th May 2015, 19:29
  #83 (permalink)  
Join Date: Jul 2011
Location: Melbourne
Posts: 46
Originally Posted by Transition Layer View Post

Thanks for the great detail you went into with your explanation, helps us understand things a bit more.

Glad to hear that you are aware this stuff goes on. Very frustrating for us too, as we know exactly where he/she is thanks to TCAS and we all know a 737 cruises faster than an F100!

No problem.
Yeah we try and police it to the best of our ability, and the fact that we can see exactly where all of you are on ADSB helps spot the obviously 'ambitious' estimates... It also used to be a pain in the ass switching aircraft around as it involved lengthy conversations with the flow, but MAESTRO has given us the license to use a bit of common sense in that situation.

That being said, it all comes down to the controller working too. Some of the newer, fresh faced and recently rated controllers still take a pilot's word as gospel, whereas those of us who have been around for a little longer have learned to be a bit more cynical when it comes to trusting all FF estimates.
WhisprSYD is offline  
Old 25th May 2015, 21:48
  #84 (permalink)  
Join Date: Sep 2002
Location: Eastside
Posts: 593
Similar to when pilots give an unrealistic estimate for JULIM, become number 1, then despite getting direct and pushing 310 on the descent to JULIM they end up 2 mins late and every behind gets shafted...
. This [email protected] behaviour seems to be happening a lot lately - and it's just as likely to be a 737 as f100.

I'll be honest, I don't understand why, in this age of technology, you need to be relying on a verbal fix estimate. However, why not give aircraft unable to make their fix time a 180 degree vector to the back of the queue - I reckon that might sort out the problem.
grrowler is offline  
Old 26th May 2015, 03:12
  #85 (permalink)  
Join Date: Jun 2006
Location: Brisbane
Posts: 81
In general I find I only burn half the holding fuel by descending to say FL250 vs continuing at flight planned cruise altitude then entering the pattern to lose the same time.
Huh? You just provided figures that show 1% or less burn difference at holding speeds between cruise altitude and FL250.

Additional fuel (up to 5% as per your figures) can be saved by flying in a straight line vs a racetrack hold. Vectors (if they are long ones) will consume less fuel than a holding pattern due to less turns. Turns burn more fuel (more thrust required to maintain speed).

So, yes, descending early and slowing with vectors will be slightly more fuel efficient than maintaining cruise and entering a holding pattern.

This saving will be something less than a theoretical maximum of 6%, as some turns are still required with vectors. Not "half the holding fuel" as you claim.


So, to the ATC'ers wondering which we prefer - the fuel savings are small so our answer may depend on other more significant factors which will change from day to day.

Such as:

1. Turbulence (why would I want to leave smooth air early?)
2. Icing
3. Workload (yours or mine?)
4. Fatigue (what's easiest?)
5. Personal preference of the pilot flying.
6. Personal experience of the pilot flying (e.g. first time in Oz? or fly 4 sectors/day out of BNE?)

So, if you have time, yes please ask our preference. I often request an early descent if it means achieving a short delay without vectors, but I won't if I suspect turbulence at lower levels, and I might not for a longer delay because vectors/holding is inevitable regardless.

Thanks for the explanations guys. Most of us get it, and most of us appreciate you are doing a great job with the resources and systems available. And yes, ATFM has helped quite a bit.
Derfred is offline  
Old 26th May 2015, 10:01
  #86 (permalink)  
Join Date: Jul 2010
Location: East Coast Australia
Posts: 14

I can't believe I just read 5 pages of what might just be the actions of a slack / busy / inexperienced / 'not having a good day' ATC.

As a controller some days I know my "Service level" is better than others. Who doesn't go home occasionally thinking they didn't perform at 100%...

Needless to say, long haul aircraft arriving on the east coast rarely get a slowdown from me outside 200nm, would have to be stable 15-20+ minutes to warrant moving attention away from my holding/vectoring/sequencing to slow you down.

The main reason being is that I can control my sequence that is inbound via my feeder fix (spacing, arriving order, track shortening), and if I lock you in early and slow you down, the system continues to update your radar "estimate" for the feeder fix (noting you are now slower!), meaning you can actually drop behind traffic from another feeder fix that is not locked in! Talk about screwing you over!

We get by just fine nearly all of the time peoples.
Undercover Brother is offline  
Old 26th May 2015, 12:30
  #87 (permalink)  
Join Date: Nov 2002
Location: meh
Posts: 660
Why does it make you feel better to be given a 10 minute hold at 200 miles than us telling you to reduce speed to lose 10 minutes with the implicit understanding that you'll tell us what you want to do?"

The last part of this quote I think sums up the bones of the topic starters issue. It is Air Traffic Control not Air Traffic Negotiation. Due to attitudes, training and culture in Australian Aviation, controllers let the aircraft tell them what they want to do as opposed to the other way around.
Plazbot is offline  
Old 26th May 2015, 13:25
  #88 (permalink)  
Join Date: May 2009
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C'mon, ATC the world over is full of negotiation and letting aircraft do what they want when that option is available. They get to pick the level they want to fly on the route they want to fly at the speed they want to fly. It's called flight planning. "Request flight level....". "Request direct.....". "Request ILS approach......". Sounds a lot like negotiation to me.

You don't control their descent point unless it's required. You don't control their rate of climb unless it's required. You don't control their descent speed unless it's required. You don't control how they meet their fix time unless it's required. I'm not flying their aircraft. If they request 20 miles left due weather I don't vector unless required.

How is letting an aircraft decide how much time they want to lose with speed and the rest with vectors or holding any different? I'm still controlling things. If I can safely and sensibly accommodate a request then why shouldn't I? I guess I can wave my willie around and shout "thou shalt do it my way or the highway" but why bother when there's an option and I don't care which way it's done?
le Pingouin is offline  
Old 26th May 2015, 14:10
  #89 (permalink)  
Join Date: Nov 2002
Location: meh
Posts: 660
Which is my basic point. This thread is Australian specific and I am assuming you are a current Australian controller and therefore you have the luxury of all that airspace to have options such as giving aircraft the choice. Much of the world is extremely limited with airspace size and complexity and therefore choice. I did have a bit of a smirk when I read a few of the other airports around the world being used as examples of better places to fly.

The US for example has a very mature ATFM system where they have many people dedicated to the task of moving aircraft all over the sky hundreds of miles away from their destination to manage not only landing capacity but sector capacity without making a single transmission themselves. Euro Control are similar. The Dubai example is an odd one. Aircraft arriving first hear about their delay somewhere between 6 and 15 minutes from their feeder fix. As a result they all go to the hold. In the extremely small airspace there, allowing an aircraft to truck on down on their own profile would see an enormous mess form in just a few minutes. Of note, No one ever complains or questions why any control instruction is given.

I recall in the early days of Maestro, techniques for sequencing turbo props consisted of turning them into the wind, telling them their feeder fix time and having them tell you when they had sat on the heading long enough to comply. Most major airports around the world would see that aircraft not only in the next sector but in some places the next country.

I'm not saying which is better just that the nature of the evolution of delaying techniques in Australia was influenced by available resources and in my opinion allows the controller to be 'lazy' for want of a better word.

The one aspect of the Australian method that baffles me us allowing aircraft to depart outside of their slot. This is an example of the overall culture of aviation in Australia I mentioned. This leads to the controllers feeling anxiety when hey have to give an aircraft the bad news because you know full well the pilot is going to question you and you need a pretty quick answer meaning that you end up double guessing everything you do.
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Old 26th May 2015, 16:03
  #90 (permalink)  
Join Date: Feb 2015
Location: Santa Barbara
Posts: 917
How hard is it?

'Adjust speed to cross _ _ _ _ _ at time _ _ at 250kts'

'Best we can do is time _ _'

'Turn right heading _ _ _, advise when the FMS shows time _ _ at _ _ _ _ _'

The name is Porter is offline  
Old 26th May 2015, 23:00
  #91 (permalink)  
Join Date: Jul 2010
Location: East Coast Australia
Posts: 14
"The one aspect of the Australian method that baffles me us allowing aircraft to depart outside of their slot."

One of the many things that baffles me is an Australian controller is how overseas long-haulers depart on their slot time, we have 'trackmasters' in the hallowed "National Operations Centre" aka NOC who approve wondrous flextracks to allow aircraft save time and fuel, the then the same boffins at the NOC run ALOFT v3 aka "SEMAP" to tell which aircraft are non-compliant with their Sydney arrival times!

How brilliant do you think controllers feel telling them they are 10-30 minutes ahead of their time, only to have some slow down and be overtaken by trafic that should have been sequenced behind them. When Sydney Flow does arrive at 5am, they promptly ask WTF has happened?

How embarassing..
Undercover Brother is offline  
Old 27th May 2015, 01:07
  #92 (permalink)  
Join Date: Sep 2003
Location: Dunnunda
Posts: 478
Personally I don't think it is that hard though I believe all our hands are tied.

There are two things which have to be considered for any new system. They are:

1) Controllability
2) Flexibility

As a pilot there is only one thing I can control when it comes to ATC flow management and that is what time we actually cross the feeder fix. Simply, the earlier I know, the more efficiently I can achieve that. If I have to hold inevitably so be it, though I shouldn't be told this approaching TOD. Personally I would like to be given an estimated crossing time on first contact with centre.

What I can't understand is why the system is not robust enough to allow for this? Ok, yes with 2 or 3 minute feed requirements and close in departures, weather diversions and go arounds the flow will change, however what I would like to see is a system developed that manages capacity. If too many aircraft are going to cross the feeder fix at time X and delays are developing greater than a couple of minutes, let the other guys know on departure well before the bottle neck, or before departure. We do it for Bad weather say between BNE and SYD with start approvals, why is it not the norm?

One method I find works quite well is the expected landing time.

"xxx123 Delays into Melbourne, expect landing time 0123, speed reductions approved"

Controllers, Just so you know when I hear this, this is what I do:

If it's a long week:

1. Select RTA Melbourne
2. Enter 0123


If it's not a long week

1. Assess the expected delay.
2. Reduce Cost index --> Assess time
3. Reaching CI 0, reduce descent speed to the minimum --> Assess Time
4. Reduce Airspeed from Max Range to Max endurance --> Assess time
5. Descend to a lower lever maintaining Max Endurance for an associated reduction in TAS/GS (dependant on forecast wind), to hold in a straight line.
6. Let ATC know if unable to make the crossing time.

Either way, the preference will always be to hold in a straight line at my most efficient holding altitude if need be with vectors/holding as a last resort.

I just wish the system had enough maturity and resources to have the information passed down the line earlier rather than later.
Bula is offline  
Old 28th May 2015, 13:11
  #93 (permalink)  
Join Date: Dec 2002
Location: Springfield
Posts: 248
How to game Maestro

SEMAP notwithstanding, fly as fast as you can, as direct as you can, and you will be numero uno. Sequence gets firmish about 40 minutes out. Too many nearby regional airports to do otherwise. The original complainant should pull their head in, ATC are effectively giving an EAT. Always better to vector/hold on the way down to FL230 than over the burbs at A070.

A380s and <25,000kg acft will get f*ed around at Sydney regardless, thanks to this.
Duff Man is offline  
Old 29th May 2015, 08:58
  #94 (permalink)  
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Interesting map Will, explains a good deal, but also creates a couple of questions in my mind.
As I've said previously having been in the airspace for 8-9hrs, the system is aware via satcom datalink (which is used for and to determine separation outside of radar range...my understanding) of all the ETA's to the nearest minute.
If as you say the sequence isn't finalised until 250nm, then at what range is the planning started? Surely from a planning perspective, if something is finalised, then the starting point begins with the available information..i.e. aircraft already airborne and providing accurate estimates.
All things being equal, from a planning perspective, I would have thought that already inbound aircraft would be allocated their place in the sequence..and popup aircraft closer to destination estimating the feeder fix at an earlier time would merely be allocated an earlier time or advised of a delay. Given that the delay is now a known minimum quantity, why can't this be passed on? Yes we all know the environment is dynamic, yes by now I am aware that in terms of a plan..nothing is in place until I am practically on top of the airport....but a little bit of info helps.
The alternative based upon the explainations on here relating to finalising the plan is to merely fly at warpspeed and get to the front of the line before anyone else.
FWIW the other morning into MEL I was advised of our inbound delay about 40 minutes from destination, superb is a word I would describe the level of service I received on that particular day.
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Old 29th May 2015, 13:56
  #95 (permalink)  
Join Date: Feb 2015
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The alternative based upon the explainations on here relating to finalising the plan is to merely fly at warpspeed and get to the front of the line before anyone else.
Come up to the front of the class you get 2 stars for paying attention
The name is Porter is offline  
Old 30th May 2015, 03:00
  #96 (permalink)  
Join Date: Dec 2002
Location: Springfield
Posts: 248
haughtney1, your thinking is sound. Your error is a misunderstanding of priorities as applied by ATC.

All things being equal, arrival delay is distributed evenly amongst all aircraft. This delay figure becomes fairly stable about 40 minutes out from dest based on estimate for the feeder fix. "Popup" aircraft have the same priority as long haulers, and will take your position in the sequence if it means delay is spread evenly.

It's analogous to a deli queue in the supermarket. You don't get your ticket until you get to the counter - even though you phoned the manager from your Audi when you left home.
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Old 30th May 2015, 03:13
  #97 (permalink)  
Join Date: Aug 2007
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haughtney1 it's a bit more complicated then that. MAESTRO looks out to 2 and a half hours (I think, we don't use anything like that sort of lead time) but the sequence is subject to change until very close in. The sequence is sort of finalised at 250 miles ish but a short flight departing just ahead of you will still be placed in front of you. There is a point at which your position in the sequence is locked in, but for PH and I think the east coast as well that is set very close in (15 minuted rings a bell?).

Obviously long distance international flights would prefer that to be much longer, short range domestic wouldn't, and I guess there are more of them than you.

This means that the point at which we issue a FF becomes a trade off between giving as much notice as possible and waiting for a time that won't change much. Thats why for PH we use the system WhisprSYD described.

With regard to estimates, MAESTRO works on TAAATS estimates, which frankly for aircraft on descent aren't that good. They are based on miles to run, flight planned TAS, forecast winds and a table of standard descent profiles. For an international heavy, particularly an Airbus, the system estimate can easily be 4-5 early. So despite sitting in front of millions of dollars worth of computers that have been tracking each aircraft for hours, we still ask every aircraft for an estimate for the FF. Sometimes those estimates aren't that good either which leads to other problem as already alluded to.

Edited to add: PH still sets a max delay for flights form Africa and the Middle East to 5 minutes, but obviously AD and the east coast don't.
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Old 30th May 2015, 04:12
  #98 (permalink)  
Join Date: Oct 2009
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Do you know how this can happen?

The distance at which the sequence can be locked in can be extended somewhat by requiring aircraft departing from close by airports to obtain their feeder fix time before they depart. The flow will then lock that aircraft into the sequence and is able to then lock in the other aircraft around it. Those aircraft are usually departing from aerodromes that aren't very busy and they can usually takeoff whenever they want to make sure they meet that time. You just couldn't get that from airports like Sydney, they may have to wait in a queue to cross a runway, then for an aircraft to land then the next 4 aircraft in front to take off.

The sequence doesn't become stable until all the aircraft that will land before you are either airborne, or have phoned up the flow and locked in their feeder fix time.

I know it's not the first position most pilots would want to famil on when they visit a TCU. Director is much more exciting. But flow control is a bit of a dark art, and you're questions haughtney would be answered in one visit. I highly recommend it it. It's too complicated and drawn out to explain it on a forum.
1Charlie is offline  
Old 30th May 2015, 23:29
  #99 (permalink)  
Join Date: Sep 2003
Location: Dunnunda
Posts: 478
Out of curiosity, by how many minutes does the feeder fix time change on a normal day?

would an expected 15 min delay always lead to a minimum 5 minute delay 100% of the time?

Does a 5 minute delay always lead to a minimum 2 minute delay 100% of the time?

We can loose 2-4 minutes on the decent for little efficiency degradation. So if we know delays are 20 minutes into BNE, would it not be possible to assume you will atleast have 10 minutes holding, knowing realistically you will slide to 15 - 20 minutes given all other eventualities and if so is it possible to pass this information forward if one had the correct resources?

It's not perfect, however could be the balance, though it would be assessing the sequence at 500nm, not 250....

"ABC123, minimum MAESTRO delays of 5 minutes, speed reduction approved"
Bula is offline  
Old 31st May 2015, 06:53
  #100 (permalink)  
Join Date: Oct 2009
Location: at the computer
Posts: 153
Do you know how this can happen?

I don't think you can quantify the minimum delays but you're on the right track. Generally if the delays are 20mins or more they are passed to the aircraft much much earlier. Often times in this case aircraft will be told something like expect holding speed reduction approved
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