What path will determine the future of Air Traffic Control?
Currently Air Navigation Service Providers (ANSPs) pretty much universally determine (excluding regulators), based on ICAO principles (or framework), the standards and the manner in which Air Traffic is managed.
The ICAO framework is under constant review; with a view for a long term plan. Europe, Asia, Africa, Australia, USA, Canada, South America all have various national and international plans; but is there a true global vision? Well is that not the role of ICAO? Are they doing their jobs? Is ICAO determining a future plan, if so how? Who has a seat at the right tables in the decision making processes?
Boeing and Airbus have become the dominant Civil Aircraft manufacturers, with a few ‘specialists’ doing their bit; but not in the league of the big boys. Boeing and Airbus have commenced work on Air Traffic Management, Boeings programme is now defunct or about to be by all reports. The inference is that the End User (the airlines) like the products they buy and wants the airlines to develop the best methods for flying them economically (and most profitably); to do this, the effect of ATM must be known, how do you know it? You own it.
Who is the key player in the future ATM, IATA?
4D trajectories rely upon increased accuracy and different intervention methods by the ATM systems. 4D essentially is the tracking and projection in space along the lines of latitude, longitude, altitude and time. That is that the 4D trajectory will always be know, always be accurate, always be compatible with flight elements and always be adaptable.
The 4D dreamers will have you believe that there will be essentially no role for Air Traffic Controllers in the post 4D system introduction. So what is the time line? From the information passing via this tech head, it’s beyond 2025; but reading some papers you will see full (limited to a specific area) implementation by 2015.
Aircraft rolling off the factory floors today don’t have the appropriate avionics to do 4D; some of the elements, but not everything; particularly up-linking integrity and flight accuracy. So what of 2025 implementation? How many years is equipment being purchased today going to last? One suspects it will be well beyond 2025; thus there can’t be full implementation by 2025. Let’s not mention GA, or military ops; UAVs and the like. Did someone say weather? Did someone say non normal ops?
The ‘technology’ will need to be 100% accurate, 100% variable, 100% reliable and 100% unbelievable. Is this the realm of “pie in the sky BS” or really going to become a reality.
Recent trials have scene Constant Descent Approaches and CPDLC (Data link) routing uploads (makes for great PR for airlines and ANSPs); with the time elements, the crucial crux of 4D, described as a roaring success because the aircraft involved were flown within 95% target range.
Flights are contained within 2 ‘bubbles’, the first nominally being called a ‘freedom bubble’ and the second a ‘safety bubble’. Essentially no other Hazard shall enter the Freedom Bubble, cause that means near miss; it's a bubble to allow changes to heading, potentially altitude and speed without the need to calculate a whole new 4D trajectory; but at all times must stay inside the freedom bubble. The Safety Bubble will need to take account of things such as wake turbulence displacement; navigation accuracy, safety margins etc.
From what I can guesstimate that need to remove ATCs and ANSPs is to increase safety and capacity; great goals. But what really reduces capacity; often it is nothing to do with ATCs; it’s more to do with infrastructure; such as surveillance availability or runway and airport capacity; this will not be dramatically increased by airborne automated systems; although we do concede there is great potential to have “finals spacing” regulated and improved; this may save 2 or three minutes across the hour for a couple of aeroplanes.
But whilst in the real world, the likelihood of an automated system actually providing increased capacity is extremely limited as all the variables will be defaulted to minimum safety in all circumstances.
ACAS (such as TCAS) enhancements allowing for pilot to pilot collision resolution and in trail climb/descent procedures etc. will enable increased airborne capacity far more readily than the concepts surrounding 4D; but to what end? Airborne capacity is reduced by two factors, workload and technology. These two things go hand in hand; improved technology means less workload.
As an example one $5M radar site strategically placed in a current non surveillance area could reduce sector numbers (by about 3) and thus controller numbers (by about 12); increase capacity, increase safety, increase efficiency and reduce industry charges. Investment in the new (like that 90 year old radar thingymajig) will pay off in spades; by why won’t they listen? One off investment of a trivial amount of money would be recovered in 3 years worth of ATC wages alone; forgetting the economic benefits directly into the airlines pockets.
The investments in the future is ‘gearing’ towards 4D, User Preferred Trajectories, flex tracks, automation, ADS-B (in and out), CPDLC.
But my real question after all that is should existing ATM systems be enhanced with more modern and known (trusted) technology or should we be jumping ship into a new direction with gusto; knowing one day it will leave port we just don’t know when.
Friday, December 7, 2007
Thursday, October 25, 2007
Increase capacity or build more runways/airports?
We often hear commentary that air traffic control systems need to be modernised to increase capacity, but what actually limits capacity, poor air traffic control equipment, low numbers of air traffic controllers, complex airspace structures and rules, or available bitumen to land and depart aeroplanes?
As demonstrated in a recent European Parliamentary Report, tabled on 11 October this year, whilst ‘optimising existing capacity’ plays an important role, growth figures for Europe of 5.2% per annum, mean that additional airports are going to be required. The report calls for 25 new airports, 10 majors and 15 medium size aerodromes, to be fully operational by 2025, according to Eurocontrol.
This growth rate means that in 2025 demand will be 2.5 times the amount of movements compared to 2003 levels.
The lead in time for a major airport is approximately 8 years; this means that within 10 years the developments must commence.
The report called for a Master plan to be developed by 2009 to "promote and co-ordinate any national and cross-border initiatives for building new airport capacities".
"Airports are so congested that if one flight gets slightly delayed, it affects many other airports. The lack of airport capacity is therefore not just a national problem - it is a European problem", pointed out Danish Liberal MEP Anne Jensen, who drafted the report.
The report adds that building new capacity would also be a first step towards averting unnecessary air pollution caused by en route or ramp congestion, but says that additional measures to limit greenhouse gas emissions and noise - such as including aviation in the EU's Emissions Trading Scheme taxing fuel or differentiating airport charges according to environmental performance - would be necessary.
But what about capacity now, well there are limitations imposed on routings and sector through put right now; a way to increase capacity is to bring online new technologies, such as airborne procedures, where pilots are assigned separation responsibilities relating to other aircraft, but these are still years away from being operational and are based on ADS-B technology, including ADS-B-IN where aircraft receive information about other aircraft in the vicinity and display that to the pilots; currently ADS-B-OUT is in use, where by aircraft transmit information based on satellite derived positions.
Other Air Traffic Control technology including separation or conflict detection tools may increase capacity because controllers will become more reactionary rather than planning forward to avoid conflictions. But this needs to be 100% accurate, at present the algorithms are getting close, it’s still not good enough; one slipping through the “cracks” is one too many.
Surveillance (including ADS-B, Multilateration and radar) and synthetic displays are the way of the future; but who pays for all this infrastructure? So far the airline industry is equipping themselves with ADS-B; but what use is it while light aircraft have access to the same piece of the sky without requiring the technology?
To use all this equipment, and develop it, it requires bodies at the coal face. We have significant anecdotal evidence that there is a world wide shortage of controllers. In the USA we have seen retirements far exceed the forecasts, mostly down to poor industrial relations with the employer, this is exacerbated by the fact that eligible to retire controllers may receive higher ‘pension wages’ and bigger annual increases in retirement than staying in the workforce.
Elsewhere we have seen limited recruitment campaigns where pass rates are still globally measured around 60%. Most ANSPs are becoming or have become privatised, or if not are run as separate profit making divisions (government owned businesses, run in business models). In order to return profits, staffing levels are reduced to the core requirements (or below them) and recruitment's are undertaken to meet the retirement forecasts and little else.
So who will be available to implement and develop this new technology? Who will be able to perform increased ATC duties at additional facilities (aerodromes) that will be built to meet current growth forecasts? Ask your managers what is being done to cater for long term growth? In some parts of the world growth is in the double % digits.
As demonstrated in a recent European Parliamentary Report, tabled on 11 October this year, whilst ‘optimising existing capacity’ plays an important role, growth figures for Europe of 5.2% per annum, mean that additional airports are going to be required. The report calls for 25 new airports, 10 majors and 15 medium size aerodromes, to be fully operational by 2025, according to Eurocontrol.
This growth rate means that in 2025 demand will be 2.5 times the amount of movements compared to 2003 levels.
The lead in time for a major airport is approximately 8 years; this means that within 10 years the developments must commence.
The report called for a Master plan to be developed by 2009 to "promote and co-ordinate any national and cross-border initiatives for building new airport capacities".
"Airports are so congested that if one flight gets slightly delayed, it affects many other airports. The lack of airport capacity is therefore not just a national problem - it is a European problem", pointed out Danish Liberal MEP Anne Jensen, who drafted the report.
The report adds that building new capacity would also be a first step towards averting unnecessary air pollution caused by en route or ramp congestion, but says that additional measures to limit greenhouse gas emissions and noise - such as including aviation in the EU's Emissions Trading Scheme taxing fuel or differentiating airport charges according to environmental performance - would be necessary.
But what about capacity now, well there are limitations imposed on routings and sector through put right now; a way to increase capacity is to bring online new technologies, such as airborne procedures, where pilots are assigned separation responsibilities relating to other aircraft, but these are still years away from being operational and are based on ADS-B technology, including ADS-B-IN where aircraft receive information about other aircraft in the vicinity and display that to the pilots; currently ADS-B-OUT is in use, where by aircraft transmit information based on satellite derived positions.
Other Air Traffic Control technology including separation or conflict detection tools may increase capacity because controllers will become more reactionary rather than planning forward to avoid conflictions. But this needs to be 100% accurate, at present the algorithms are getting close, it’s still not good enough; one slipping through the “cracks” is one too many.
Surveillance (including ADS-B, Multilateration and radar) and synthetic displays are the way of the future; but who pays for all this infrastructure? So far the airline industry is equipping themselves with ADS-B; but what use is it while light aircraft have access to the same piece of the sky without requiring the technology?
To use all this equipment, and develop it, it requires bodies at the coal face. We have significant anecdotal evidence that there is a world wide shortage of controllers. In the USA we have seen retirements far exceed the forecasts, mostly down to poor industrial relations with the employer, this is exacerbated by the fact that eligible to retire controllers may receive higher ‘pension wages’ and bigger annual increases in retirement than staying in the workforce.
Elsewhere we have seen limited recruitment campaigns where pass rates are still globally measured around 60%. Most ANSPs are becoming or have become privatised, or if not are run as separate profit making divisions (government owned businesses, run in business models). In order to return profits, staffing levels are reduced to the core requirements (or below them) and recruitment's are undertaken to meet the retirement forecasts and little else.
So who will be available to implement and develop this new technology? Who will be able to perform increased ATC duties at additional facilities (aerodromes) that will be built to meet current growth forecasts? Ask your managers what is being done to cater for long term growth? In some parts of the world growth is in the double % digits.
Friday, October 19, 2007
Sleeping a criminal offence or a sign?
We reproduce an article from the "Scotsman" link provided below.
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Thu 18 Oct 2007
Air traffic controllers suspended for sleeping on duty
NICK PISA IN ROME
FOUR air traffic controllers have been suspended at an Italian airport after it emerged they had been sleeping while on duty.
The group, based at Milan's Linate airport, scene of a disaster in 2001 when 118 people were killed after a passenger jet collided with a private plane, were suspended after an internal investigation.
Officials at Italy's national Agency of Air Traffic Controllers launched an inquiry after being tipped off about the incident.
It discovered that pilots who had been due to land in the early hours of the morning had been met with silence when radioing the tower.
Controllers at nearby airports, who were monitoring communications, stepped into handle the flights while calls were made to Linate to wake up the dozing controllers.
In a statement the agency confirmed that four controllers, including a shift manager, had been suspended for failing to "respect night shift duties".
The statement added that at no time was any plane in danger as there was a back up system, adding the agency had "full faith in its air traffic controllers whose professionalism and preparation was recognised the world over".
It is not the first time that air traffic controllers at Linate airport - used by British Airways and the budget airline Easyjet - have been at the centre of controversy.
In an investigation seven years ago it emerged that controllers had skipped work to play football while colleagues covered for them.
During that six-month period, there were 45 near misses in the skies above the airport, although officials denied the absenteeism was to blame.
In 2004 a Milan court found four people guilty over the 2001 disaster including the airport director and an air-traffic controller who were both sentenced to eight years in prison.
This article: http://news.scotsman.com/international.cfm?id=1661802007
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Is this more a case of potential criminal negligence, or a sign that duty hours and fatigue management programs are inadequate? We refer to our previous post talking of a just culture. Does this happen more than it is reported, of course it does!
Everyone should report for duty in an appropriate state of health to be able to perform those duties; but was does that mean? Most Air Traffic Controllers we know say that night shift (and early starts) are just part of the job and you "just deal with it". The strange thing about fatigue is that when you are suffering from it you are less able to judge that you are fatigued and thus more than likely will report for duty in an inappropriate state. If you realise this at 2.30am, do you say you need relief, or soldier on and try and stay awake?
Largely across the globe fatigue has bee ignored; or has been self managed at work, by sleeping at or under consoles, waking up to respond to co-ordination or aircraft, then continuing snoozing as if nothing happened. In many parts of the globe night shift operations are insignificant; one or two aeroplanes a night over the entire 6-10 hour shift. Hardly a stimulated environment!
This is not true in many locations, night time operations can be busier than day time operations; for example the gulf states or West Asian nations have many transiting aircraft at night as aircraft leaving Europe for East Asia etc. hit that part of the globe in the dead of night. Generally speaking in these locations staffing levels and stimuli are as adequate as during the day and thus the work environment is less conducive for snoozing. Also the full staffing complement means that there are 'normal' breaks and rest periods away from the consoles; unlike single manned positions where the stimuli is low.
Many ANSPs reduce night time staffing to levels up to 1/10th of day time staffing; this primarily is based on lack of traffic, complexities and workload. But what does that mean for the staff attending night shift operations? A long, tedious night where staying awake is the biggest challenge and next to impossible due to the lack of stimuli.
We've all heard stories of people asleep at night, do you have one, please comment.
I remember a story of the sleeping freighter pilot in the middle of nowhere about 3 in the morning at FL220 with an open mic, snoring could be heard over the air-ground frequency.
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Thu 18 Oct 2007
Air traffic controllers suspended for sleeping on duty
NICK PISA IN ROME
FOUR air traffic controllers have been suspended at an Italian airport after it emerged they had been sleeping while on duty.
The group, based at Milan's Linate airport, scene of a disaster in 2001 when 118 people were killed after a passenger jet collided with a private plane, were suspended after an internal investigation.
Officials at Italy's national Agency of Air Traffic Controllers launched an inquiry after being tipped off about the incident.
It discovered that pilots who had been due to land in the early hours of the morning had been met with silence when radioing the tower.
Controllers at nearby airports, who were monitoring communications, stepped into handle the flights while calls were made to Linate to wake up the dozing controllers.
In a statement the agency confirmed that four controllers, including a shift manager, had been suspended for failing to "respect night shift duties".
The statement added that at no time was any plane in danger as there was a back up system, adding the agency had "full faith in its air traffic controllers whose professionalism and preparation was recognised the world over".
It is not the first time that air traffic controllers at Linate airport - used by British Airways and the budget airline Easyjet - have been at the centre of controversy.
In an investigation seven years ago it emerged that controllers had skipped work to play football while colleagues covered for them.
During that six-month period, there were 45 near misses in the skies above the airport, although officials denied the absenteeism was to blame.
In 2004 a Milan court found four people guilty over the 2001 disaster including the airport director and an air-traffic controller who were both sentenced to eight years in prison.
This article: http://news.scotsman.com/international.cfm?id=1661802007
--------------------------------------------------------------------------------------------------------
Is this more a case of potential criminal negligence, or a sign that duty hours and fatigue management programs are inadequate? We refer to our previous post talking of a just culture. Does this happen more than it is reported, of course it does!
Everyone should report for duty in an appropriate state of health to be able to perform those duties; but was does that mean? Most Air Traffic Controllers we know say that night shift (and early starts) are just part of the job and you "just deal with it". The strange thing about fatigue is that when you are suffering from it you are less able to judge that you are fatigued and thus more than likely will report for duty in an inappropriate state. If you realise this at 2.30am, do you say you need relief, or soldier on and try and stay awake?
Largely across the globe fatigue has bee ignored; or has been self managed at work, by sleeping at or under consoles, waking up to respond to co-ordination or aircraft, then continuing snoozing as if nothing happened. In many parts of the globe night shift operations are insignificant; one or two aeroplanes a night over the entire 6-10 hour shift. Hardly a stimulated environment!
This is not true in many locations, night time operations can be busier than day time operations; for example the gulf states or West Asian nations have many transiting aircraft at night as aircraft leaving Europe for East Asia etc. hit that part of the globe in the dead of night. Generally speaking in these locations staffing levels and stimuli are as adequate as during the day and thus the work environment is less conducive for snoozing. Also the full staffing complement means that there are 'normal' breaks and rest periods away from the consoles; unlike single manned positions where the stimuli is low.
Many ANSPs reduce night time staffing to levels up to 1/10th of day time staffing; this primarily is based on lack of traffic, complexities and workload. But what does that mean for the staff attending night shift operations? A long, tedious night where staying awake is the biggest challenge and next to impossible due to the lack of stimuli.
We've all heard stories of people asleep at night, do you have one, please comment.
I remember a story of the sleeping freighter pilot in the middle of nowhere about 3 in the morning at FL220 with an open mic, snoring could be heard over the air-ground frequency.
Sunday, October 14, 2007
"JUST" CULTURE
We note the recent decision in a Swiss court regarding the Uberlingen mid-air collision of 2002 and reproduce the words from the IFATCA press release issued in response to the decision.
MEDIA Release-----------------------------------------------------------
The district court in Bülach, Switzerland, has found four middle managers of Skyguide guilty in the case surrounding the Uberlingen mid-air collision of 2002. The same court has acquitted four others, including air traffic controllers and technicians.
That the court has gone beyond the front-line operators represents a new development from the legal aftermath of recent ATC-related accidents (we think of Brazil, for example). It is encouraging to note that accountability in a complex socio- technical system is expected at all organizational levels, not just at the sharp end.
We continue to be troubled, however, by criminalization of so-called human errors, whomever these errors may be attributed to. Whether those accused are controllers, technicians, managers, or directors legal pressures and criminalization hamper the free-flow and exchange of safety-related information across all organizational levels within a strong safety culture.
IFATCA believes that all personnel should be held accountable for their decisions and actions in a safety-critical system; however, experience has shown that criminal prosecution makes no contribution to improving system safety. IFATCA is signatory to the October 2006 joint resolution on the detriment to aviation safety of the “criminalization of error” issued by the Flight Safety Foundation (FSF), the Civil Air Navigation Services Organisation (CANSO), the Royal Aeronautical Society in England (RAeS) and the Academie Nationale de L’Air et de L’Espace (ANAE) in France. We repeat our call for all stakeholders to recognize the valuable contribution a just culture environment will make to aviation safety.
--------------------------------------------------------------------------
It is very important that pilots and ATCs require a "JUST CULTURE"; in every accident or incident there is a natural tendency to seek out the reasons why it occurred. In fact from a systemic view point it is required.
Unfortunately human nature, particularly involving loss of life, in searching for the reasons of why something went wrong the quick concept is to proportion blame; normally to the humans involved in the process. This is particularly true in aviation; probably more so than in any other industry, with the exception of massive accidents like Chernobyl nuclear accident or the Bhopal tragedy.
In an aviation accident, normally what happens it the "air traffic controller" made an error which led to the events; particularly so when it involves mid-air collisions.
The person who was at the console at the time (or the previous controller) made an error; but is that the same thing as being negligent, or worse criminally negligent?
Whilst the controller directly involved in the Uberlingen accident was never charged, I wonder if he lived longer (he was murdered by a family member of a victim of the collision) whether he would have been.
Of interest in this case is that 'back office' decision makers were charged, because the accident happened during the night where single staffing was prominent, where the system and back-up systems were in a state of degradation (not functioning correctly). They have been held accountable for decisions which may have been allowed to occur without the appropriate safety assessment prior to the event.
I wonder if this accident was two buses, involving the same level of loss of life, whether people from the roads authority would have been charged for approving road works on the highway?
Human errors will always occur, "to err is human", the air traffic system is designed around systemic barriers for error prevention and error detection; modern systems advise the controller when conflicts are about to or are occurring. But at times of degradation these sometimes do not work; these systems very much rely on the use of radar surveillance; so over the majority of the worlds skies no collision detection system exists.
TCAS (ACAS - Airborne Collision Avoidance System) is the 'ultimate fallback' to controller or ATS systemic error; but TCAS relies on the correct application from the pilot view point (which was a significant factor in this case). TCAS uses the information from onboard equipment of the other aircraft in the vicinity; it may 'over react' at times and suggest avoiding action when a separation standard actually exists. If this reaction occurs due to false data (e.g. faulty height read-out) from the other aircraft then TCAS can make a disastrous avoiding action decision.
Every-time there has been a significant error in aviation, the media in particular looks for the person(s) to blame. In recent times controllers from Switzerland, Japan, Brazil and Kenya have all been prosecuted for making an error; not that the error itself was negligent or deliberate, but because of the consequence of that error.
A key advantage of a JUST CULTURE is accurate reporting for investigation and thus development of improved error prevention strategies; where a JUST CULTURE does not exist, errors are hidden or covered up to possibly prevent the retribution of the system. Controllers making mistakes are normal, systems catching the mistakes is required.
A "JUST CULTURE" would treat every like type error in the same manner, regardless of the consequence; despite the emotions involved.
MEDIA Release-----------------------------------------------------------
The district court in Bülach, Switzerland, has found four middle managers of Skyguide guilty in the case surrounding the Uberlingen mid-air collision of 2002. The same court has acquitted four others, including air traffic controllers and technicians.
That the court has gone beyond the front-line operators represents a new development from the legal aftermath of recent ATC-related accidents (we think of Brazil, for example). It is encouraging to note that accountability in a complex socio- technical system is expected at all organizational levels, not just at the sharp end.
We continue to be troubled, however, by criminalization of so-called human errors, whomever these errors may be attributed to. Whether those accused are controllers, technicians, managers, or directors legal pressures and criminalization hamper the free-flow and exchange of safety-related information across all organizational levels within a strong safety culture.
IFATCA believes that all personnel should be held accountable for their decisions and actions in a safety-critical system; however, experience has shown that criminal prosecution makes no contribution to improving system safety. IFATCA is signatory to the October 2006 joint resolution on the detriment to aviation safety of the “criminalization of error” issued by the Flight Safety Foundation (FSF), the Civil Air Navigation Services Organisation (CANSO), the Royal Aeronautical Society in England (RAeS) and the Academie Nationale de L’Air et de L’Espace (ANAE) in France. We repeat our call for all stakeholders to recognize the valuable contribution a just culture environment will make to aviation safety.
--------------------------------------------------------------------------
It is very important that pilots and ATCs require a "JUST CULTURE"; in every accident or incident there is a natural tendency to seek out the reasons why it occurred. In fact from a systemic view point it is required.
Unfortunately human nature, particularly involving loss of life, in searching for the reasons of why something went wrong the quick concept is to proportion blame; normally to the humans involved in the process. This is particularly true in aviation; probably more so than in any other industry, with the exception of massive accidents like Chernobyl nuclear accident or the Bhopal tragedy.
In an aviation accident, normally what happens it the "air traffic controller" made an error which led to the events; particularly so when it involves mid-air collisions.
The person who was at the console at the time (or the previous controller) made an error; but is that the same thing as being negligent, or worse criminally negligent?
Whilst the controller directly involved in the Uberlingen accident was never charged, I wonder if he lived longer (he was murdered by a family member of a victim of the collision) whether he would have been.
Of interest in this case is that 'back office' decision makers were charged, because the accident happened during the night where single staffing was prominent, where the system and back-up systems were in a state of degradation (not functioning correctly). They have been held accountable for decisions which may have been allowed to occur without the appropriate safety assessment prior to the event.
I wonder if this accident was two buses, involving the same level of loss of life, whether people from the roads authority would have been charged for approving road works on the highway?
Human errors will always occur, "to err is human", the air traffic system is designed around systemic barriers for error prevention and error detection; modern systems advise the controller when conflicts are about to or are occurring. But at times of degradation these sometimes do not work; these systems very much rely on the use of radar surveillance; so over the majority of the worlds skies no collision detection system exists.
TCAS (ACAS - Airborne Collision Avoidance System) is the 'ultimate fallback' to controller or ATS systemic error; but TCAS relies on the correct application from the pilot view point (which was a significant factor in this case). TCAS uses the information from onboard equipment of the other aircraft in the vicinity; it may 'over react' at times and suggest avoiding action when a separation standard actually exists. If this reaction occurs due to false data (e.g. faulty height read-out) from the other aircraft then TCAS can make a disastrous avoiding action decision.
Every-time there has been a significant error in aviation, the media in particular looks for the person(s) to blame. In recent times controllers from Switzerland, Japan, Brazil and Kenya have all been prosecuted for making an error; not that the error itself was negligent or deliberate, but because of the consequence of that error.
A key advantage of a JUST CULTURE is accurate reporting for investigation and thus development of improved error prevention strategies; where a JUST CULTURE does not exist, errors are hidden or covered up to possibly prevent the retribution of the system. Controllers making mistakes are normal, systems catching the mistakes is required.
A "JUST CULTURE" would treat every like type error in the same manner, regardless of the consequence; despite the emotions involved.
Friday, September 28, 2007
Airspace & Risk
At the IFATCA annual conference held in Istanbul Turkey in April 2007 IFATCA amended it’s policy regarding ATC at aerodromes; the policy now reads:
Air Traffic Control service shall be provided at aerodromes that:
have published IFR approach, departure or holding procedures, and where control is required for the safety of air traffic.
for VFR operations, where required to ensure that appropriate safety levels are met.
I find the policy to be incredibly non descriptive about the airspace classifications, levels of ATC service and that there essentially are no ‘trigger points’ to which allude to levels of safety.
In Australia we are having a ongoing debate about airspace classifications in general then whether a UNICOMs/CAGRO, ATC tower services ranging from GAAP (similar to the VFR TWR model), to Class D (regional towers), to Class C tower services (provided at capital cities). See the recent debates about AVALON.
In Australia we have 3 prominent examples of UNICOM/CAGRO services, Ayres Rock, Broome and Jandakot Tower (outside tower hours). These have all proved to be successful in increasing safety, based on the lack of available statistics to prove otherwise; but are they "safe enough"? Is the Unicom/Cagro as safe and as cost effective as a GAAP or regional Class D tower? Is there another way? Is it safer, see below about vigilance.
Australia has much Class E airspace ‘rolled out’ progressively since about 1998; the majority of this Class E is outside radar or ADS-B surveillance.
The benefit of Class E for IFRs is like Class D/C/A they are separated from other IFRs; however there is no requirement for VFRs to be known to the system when flying in Class E. It is up to the pilot of a VFR to comply with the Visual Flight Rules and remain in VMC, and adjust course as necessary to avoid IFR operations; this may include avoiding IFR routes; this doesn't always happen, but to what consequence?
How does a VFR avoid an IFR route; obviously if operating to a particular aerodrome there is no opportunity to avoid the destination; if however flying via GPS (or VFR direct) point A to point B, cross referencing to the IFR routes is next to impossible; similarly many VFR points ‘closely replicate’ IFR tracking points; thus encourage the VFRs to be at the same place as IFRs.
Thinking back to the IFATCA policy above, “ensure that appropriate safety levels” and “is required for the safety of air traffic” whilst both of these are great motherhood statements they don’t describe the when, how’s and why’s about safety.
Safety is about managing risk. Risk is present in everything we do; minimising the effect of that risk essentially becomes managing safety. In simple terms lowering the speed limit on a road is reducing risk, but only if you have compliance to the limit. A without "cause" reduction is more likely to increase non-compliance thus not altering the risk; enforced compliance helps.
Statistically the most dangerous phase of flight is landing and departure; this is because this is the phase of flight (logically) where contact with the ground is present; improper contact causes injury and damage.
In terms of airspace risk the most dangerous area of sky is close to the runway, because that is where the concentration of traffic is likely to occur; i.e. the planes want to use the runway; and often it’s only one runway.
That does not mean no risk in other areas of sky.
The risk of collision in the middle of Australia at 5500 feet (in class G) is “vanishingly small”; that doesn’t mean no risk just really really low; it assumes that there is compliance; i.e. VFR aeroplanes will ‘see and avoid’ other aircraft and that due to the density and size of the airspace available compared to the ‘footprint’ of the aeroplanes involved it is statistically improbable to think that two random events (trajectories of aeroplanes) could intersect at the collision point together. This is often referred to as "BIG SKY THEORY".
Things that conspire against BIG SKY THEORY; GPS accuracy, height locks in aeroplanes, Restricted Area avoidance, terrain avoidance, bad weather, towns, aerodromes, topographical features, ERC routes. All these things add up to increase the risk; yet at 5500 feet in the ‘middle of nowhere’ the risk of hitting another aircraft is still “vanishingly small”; this is because compliance still applies, aircraft should be operated by ‘trained’ pilots; who have received training in VFR and/or IFR flying, there are rules designed to segregate aircraft flying on the same track (or hemispheric track); crossing tracks makes it trickier; TCAS, visual reference, radio calls all make flying in Class G safer; avoiding IFR routes or way-points (if VFR) etc.
Which brings me back to when is ATC ‘required’; Air Traffic Control improves safety of flight, because conflictions should be avoided (ground and aircraft conflictions); but that is dependant on airspace classification Class E doesn’t provide a VFR with any form of protection above that of Class G; in fact it could be argued that Class G is safer as IFRs (probably the most likely confliction) are more vigilant in Class G without ATC ‘protection’ than in Class E with ATC ‘protection”, they conflict with “unknown unknowns”.
Surveillance greatly mitigates against that risk, because the VFRs can be seen “known unknowns” and thus the IFRs alerted, the VFR may hear the IFR getting the information and thus themselves become more aware; the controller is working in less difficult conditions when surveillance is available and is less concentrating on “proving the standards” being used between IFRs and providing a service to them.
Class D and Class C airspace provide extra protection; as the only elements able to use the airspace are known to the system (air traffic controller). This doesn’t mean no risk, just less risk; “known knowns”; but that assumes compliance.
Aircraft often ‘penetrate’ restricted or controlled airspace without clearance; this is usually due to pilot error, but sometimes it is deliberate non-compliance. The only place where these ‘penetrations’ are recorded and reported is where surveillance in available; or where a controller or pilot visually sees the non-compliance and reports it. There are approximately 1000 penetrations of control or restricted areas each year; many of these lead to conflictions with other aircraft, where the ATC or pilot may not even be aware of the other aircraft; or it's simply avoiding action only.
It’s not as simple in saying then make everything Class D or Class C or higher; there is a trade-off in capacity when increasing safety; this also comes at great cost. Equipment, controllers etc. all add up to increase the costs associated with increasing risk mitigation. Capacity is often reduced when increasing service as 'standards must be used'.
Remember that Class G in the “middle of nowhere” the risk is “vanishingly small”; but that doesn’t mean no risk.
Air Traffic Control service shall be provided at aerodromes that:
have published IFR approach, departure or holding procedures, and where control is required for the safety of air traffic.
for VFR operations, where required to ensure that appropriate safety levels are met.
I find the policy to be incredibly non descriptive about the airspace classifications, levels of ATC service and that there essentially are no ‘trigger points’ to which allude to levels of safety.
In Australia we are having a ongoing debate about airspace classifications in general then whether a UNICOMs/CAGRO, ATC tower services ranging from GAAP (similar to the VFR TWR model), to Class D (regional towers), to Class C tower services (provided at capital cities). See the recent debates about AVALON.
In Australia we have 3 prominent examples of UNICOM/CAGRO services, Ayres Rock, Broome and Jandakot Tower (outside tower hours). These have all proved to be successful in increasing safety, based on the lack of available statistics to prove otherwise; but are they "safe enough"? Is the Unicom/Cagro as safe and as cost effective as a GAAP or regional Class D tower? Is there another way? Is it safer, see below about vigilance.
Australia has much Class E airspace ‘rolled out’ progressively since about 1998; the majority of this Class E is outside radar or ADS-B surveillance.
The benefit of Class E for IFRs is like Class D/C/A they are separated from other IFRs; however there is no requirement for VFRs to be known to the system when flying in Class E. It is up to the pilot of a VFR to comply with the Visual Flight Rules and remain in VMC, and adjust course as necessary to avoid IFR operations; this may include avoiding IFR routes; this doesn't always happen, but to what consequence?
How does a VFR avoid an IFR route; obviously if operating to a particular aerodrome there is no opportunity to avoid the destination; if however flying via GPS (or VFR direct) point A to point B, cross referencing to the IFR routes is next to impossible; similarly many VFR points ‘closely replicate’ IFR tracking points; thus encourage the VFRs to be at the same place as IFRs.
Thinking back to the IFATCA policy above, “ensure that appropriate safety levels” and “is required for the safety of air traffic” whilst both of these are great motherhood statements they don’t describe the when, how’s and why’s about safety.
Safety is about managing risk. Risk is present in everything we do; minimising the effect of that risk essentially becomes managing safety. In simple terms lowering the speed limit on a road is reducing risk, but only if you have compliance to the limit. A without "cause" reduction is more likely to increase non-compliance thus not altering the risk; enforced compliance helps.
Statistically the most dangerous phase of flight is landing and departure; this is because this is the phase of flight (logically) where contact with the ground is present; improper contact causes injury and damage.
In terms of airspace risk the most dangerous area of sky is close to the runway, because that is where the concentration of traffic is likely to occur; i.e. the planes want to use the runway; and often it’s only one runway.
That does not mean no risk in other areas of sky.
The risk of collision in the middle of Australia at 5500 feet (in class G) is “vanishingly small”; that doesn’t mean no risk just really really low; it assumes that there is compliance; i.e. VFR aeroplanes will ‘see and avoid’ other aircraft and that due to the density and size of the airspace available compared to the ‘footprint’ of the aeroplanes involved it is statistically improbable to think that two random events (trajectories of aeroplanes) could intersect at the collision point together. This is often referred to as "BIG SKY THEORY".
Things that conspire against BIG SKY THEORY; GPS accuracy, height locks in aeroplanes, Restricted Area avoidance, terrain avoidance, bad weather, towns, aerodromes, topographical features, ERC routes. All these things add up to increase the risk; yet at 5500 feet in the ‘middle of nowhere’ the risk of hitting another aircraft is still “vanishingly small”; this is because compliance still applies, aircraft should be operated by ‘trained’ pilots; who have received training in VFR and/or IFR flying, there are rules designed to segregate aircraft flying on the same track (or hemispheric track); crossing tracks makes it trickier; TCAS, visual reference, radio calls all make flying in Class G safer; avoiding IFR routes or way-points (if VFR) etc.
Which brings me back to when is ATC ‘required’; Air Traffic Control improves safety of flight, because conflictions should be avoided (ground and aircraft conflictions); but that is dependant on airspace classification Class E doesn’t provide a VFR with any form of protection above that of Class G; in fact it could be argued that Class G is safer as IFRs (probably the most likely confliction) are more vigilant in Class G without ATC ‘protection’ than in Class E with ATC ‘protection”, they conflict with “unknown unknowns”.
Surveillance greatly mitigates against that risk, because the VFRs can be seen “known unknowns” and thus the IFRs alerted, the VFR may hear the IFR getting the information and thus themselves become more aware; the controller is working in less difficult conditions when surveillance is available and is less concentrating on “proving the standards” being used between IFRs and providing a service to them.
Class D and Class C airspace provide extra protection; as the only elements able to use the airspace are known to the system (air traffic controller). This doesn’t mean no risk, just less risk; “known knowns”; but that assumes compliance.
Aircraft often ‘penetrate’ restricted or controlled airspace without clearance; this is usually due to pilot error, but sometimes it is deliberate non-compliance. The only place where these ‘penetrations’ are recorded and reported is where surveillance in available; or where a controller or pilot visually sees the non-compliance and reports it. There are approximately 1000 penetrations of control or restricted areas each year; many of these lead to conflictions with other aircraft, where the ATC or pilot may not even be aware of the other aircraft; or it's simply avoiding action only.
It’s not as simple in saying then make everything Class D or Class C or higher; there is a trade-off in capacity when increasing safety; this also comes at great cost. Equipment, controllers etc. all add up to increase the costs associated with increasing risk mitigation. Capacity is often reduced when increasing service as 'standards must be used'.
Remember that Class G in the “middle of nowhere” the risk is “vanishingly small”; but that doesn’t mean no risk.
Friday, September 21, 2007
It's my managers money right?
Yesterday at work I was extremely discouraged by two events in particular.
Number 1:
We run a roster of 5 staff in the morning, with staggered start times:
The shifts run 0500-1100, 0600-1300, 0630-1430 X 2 and 0700-1500; these shifts are replaced by 4 afternoon shifts, a 1200-2000, 1400-2100, 1400-2200 and 1500-2300.
So our staffing requirement in the afternoon is reduced by 1. This effectively is amended when bad wx is forecast and we get in someone on Overtime to cover the peak from 1600-2000 (4 hours minimum OT payment).
The reason for the disparity in staffing levels is traffic demand; the morning peak is always busier than the afternoon peak. I guess businesses always start their day early; but finish meetings etc. at different times; at least this is how is seems.
So what was the issue: The Supervisor decided that the 0500-1100 did not need replacing when the person called in sick. So this would put us below minimum staffing; which we often do due to not having an option. Why in the case? Lack of staff to fill the vacant shift, no, simply management discretion.
So what mitigation is offered to overcome the 'stupid management decision'? Traffic Management strategies; so for the cost of about $500 (gross, the cost of the call out) We force the traffic to be delayed and avoid, enter the airspace in a particular manner so as to not overload the 4 controllers working the 4 sectors without breaks; or the 3 sectors when there should be four, so that some toilet breaks etc can occur; did someone say breakfast?
I think that the cost to industry in this scenario would exceed $5,000 (much higher if holding delays resulted), due to all the delays created in managing the traffic; for what reason, so the company didn't spend a lousy $500. Was this in the name of safety? Hell no, management stooge economics 101.
Number 2:
Almost 7 months ago a controller was "promised in writing" a pay rise on achieving their next set of ratings; this happened 5 months ago and guess what, no pay rise.
The individual in question was given a BS excuse initially about high sick-leave, 7 days in the year all consecutive, when an immediate relative was effectively on his death bed.
The individual has been 'strung along' with multiple meetings, e-mails, phone calls about a 'decision pending'; the decision now rests with a manager at head office; who apparently has being "mulling over" the decision for 2 months now; in my experience it's most unlike that individual to not make a snap call.
All the while the controller involved has been 'required' to perform extra non console duties in all this time to prove his 'worth' whilst the decision is pending.
Makes me wonder if the manager has being BSsing him the whole time; or whether the administration really is that incompetent and can't approve a pay rise ($5K or so per annum) without the say-so of someone 1 wrung below the CEO; hell by the time it is approved he'll have achieved the annual increment anyway.
It does actually come out of the purse or wallet of the relevant manager right, that's why that are so reluctant to pay; well perhaps not; it's a disgrace.
Number 1:
We run a roster of 5 staff in the morning, with staggered start times:
The shifts run 0500-1100, 0600-1300, 0630-1430 X 2 and 0700-1500; these shifts are replaced by 4 afternoon shifts, a 1200-2000, 1400-2100, 1400-2200 and 1500-2300.
So our staffing requirement in the afternoon is reduced by 1. This effectively is amended when bad wx is forecast and we get in someone on Overtime to cover the peak from 1600-2000 (4 hours minimum OT payment).
The reason for the disparity in staffing levels is traffic demand; the morning peak is always busier than the afternoon peak. I guess businesses always start their day early; but finish meetings etc. at different times; at least this is how is seems.
So what was the issue: The Supervisor decided that the 0500-1100 did not need replacing when the person called in sick. So this would put us below minimum staffing; which we often do due to not having an option. Why in the case? Lack of staff to fill the vacant shift, no, simply management discretion.
So what mitigation is offered to overcome the 'stupid management decision'? Traffic Management strategies; so for the cost of about $500 (gross, the cost of the call out) We force the traffic to be delayed and avoid, enter the airspace in a particular manner so as to not overload the 4 controllers working the 4 sectors without breaks; or the 3 sectors when there should be four, so that some toilet breaks etc can occur; did someone say breakfast?
I think that the cost to industry in this scenario would exceed $5,000 (much higher if holding delays resulted), due to all the delays created in managing the traffic; for what reason, so the company didn't spend a lousy $500. Was this in the name of safety? Hell no, management stooge economics 101.
Number 2:
Almost 7 months ago a controller was "promised in writing" a pay rise on achieving their next set of ratings; this happened 5 months ago and guess what, no pay rise.
The individual in question was given a BS excuse initially about high sick-leave, 7 days in the year all consecutive, when an immediate relative was effectively on his death bed.
The individual has been 'strung along' with multiple meetings, e-mails, phone calls about a 'decision pending'; the decision now rests with a manager at head office; who apparently has being "mulling over" the decision for 2 months now; in my experience it's most unlike that individual to not make a snap call.
All the while the controller involved has been 'required' to perform extra non console duties in all this time to prove his 'worth' whilst the decision is pending.
Makes me wonder if the manager has being BSsing him the whole time; or whether the administration really is that incompetent and can't approve a pay rise ($5K or so per annum) without the say-so of someone 1 wrung below the CEO; hell by the time it is approved he'll have achieved the annual increment anyway.
It does actually come out of the purse or wallet of the relevant manager right, that's why that are so reluctant to pay; well perhaps not; it's a disgrace.
Tuesday, August 21, 2007
More on FLOW + PRMs
So the other morning we were using RWY 16 PRM Approaches; due to wind and low cloud on the approach path. The landing rate was a cool 3 minutes between arrivals; or 40 Arrivals an hour. This is an efficient rate to allow optimum aerodrome capacity.
Effectively the tower needs a radar standard between the arrival and the departure; so 3 minute spacing allows for a departure between each arrival. If the arrivals are more tightly spaced; i.e. 5NM apart on final (the normal rate) in such conditions due to not being able to sight the arriving aircraft the tower can’t ‘fire’ the departure. So you can arrive two closer than 3 minutes even in PRMs; but not get a departure away too.
During PRM approaches the general concept is, due to the huge length of final it’s inefficient; this isn’t actually the case; yes, it’s not as efficient as visual conditions but it’s better than full dependent ILS approaches; see more below.
So the other morning we were on 40 arrivals and 40 departures an hour = maximum capacity (by law).
However, CTMS was at play and on ground delays which are strategic by nature didn’t equal the arrival rate; the CTMS rate was 34. So we are ‘expecting’ 6 slots not fully utilised. Why? Well when the CTMS program was run at 0500; it looked like the capacity would have been 34 Arrivals an hour; 17 on each runway; this configuration happens when we use 16 Dependent ILS Approaches.
PRM in Sydney is only staffed for in an adhoc at call manner; i.e. we only use it when people agree to come in on their day off. So at 0500 it wasn’t likely that enough people were going to say yes (2 of them). So rather than running CTMS rate of 40 and only achieving 34; and costing heaps of tactical fuel burns they ran it at 34. The PRM consoles are independent positions; when PRM is open all 12 consoles in Sydney are open and the room buzzes; but what do I know about such things, I’m based in Melbourne. CTMS was re-calculated around 0700; but the extra slots created were not fully utilised.
This is where effectively we use a radar standard between arrivals operating to different runways; in the SY case there is less than 1NM between centre lines; so to establish them in a dependent stream it requires spacing such as this.
Dependent Approaches
PRM Approaches
The advantage of PRMs is that if required you can have arrivals tighter than the ‘nominate acceptance rate’ on the same ILS; possibly swapping a departure slot for an extra arrivals slot etc; without effecting what’s happening on the other runway with dependent approaches; what ever you do on one ILS in terms of spacing has an effect on the other runways spacing too.
So back to what I do. The sequence here.... Just talking about the RWY16R sequence.
I’ve taken the liberty to include the savings in time (due to high speed and track shortening) into account across the averages. Things to note; between 2017 and 2054 the runways is at effective maximum capacity; then the CTMS rate of 34 left a few holes, basically 3 nine minute gaps. From 2127 until 2151 again its a maximum capacity.
Another thing to consider is we deal in whole minutes for the purposes of MAESTRO and flow; but the realities of the beast is is we have 150 seconds (2.5 minutes) between arrivals or a rate of 48 arrivals an hour; we actually use this rate (or tighter at times). So early or late at a fix does transpose into the real sequence spaces not the flowed spaces.
The nuts and bolts about how this one happened: QFA42 was slowed to follow EA2202; VOZ401, VOZ809 and QFA730 were given 250Kts and a vector to follow QFA42. HVN783 was given DCT to RIVET with high speed to follow QFA730; as was JST761.
VOZ811 and QFA408 were actually vectored to follow JST761 for separation, even though it appears there was no delay. VOZ619 was given DCT RIVET with high speed. QFA412 was untouched and QFA130 joined in from BN sectors (using my runway); QFA586 was untouched and RXA514 was shortened up on the non-jet STAR.
Then there were the gaps and all aircraft got high speed descents. CPA023, CAL051 and CES561 joined the sequence via BN sectors. QFA414 was given a crew managed delay time for RIVET; i.e. “adjust speed to cross RIVET at 13 at 250K.” Note it’s 23 minutes from RIVET at 250K (45NM SY) via the PRM approach to touch down.
SIA231 was vectored at cruise and given slow speed on descent (250K) to make RIVET at time 19; but later it became apparent that they wouldn’t make 19 (cause they got low); so they were brought back to profile speed; QFA740, VOZ821 were vectored to follow SIA231 and descended at 250K.
QFA564 (Canberra Sydney) was given a ‘strategic’ slot for departure to make good a landing of 2150; they got away early so were estimating the field at 2145; but the delay was need to make a landing of 2151; so they got a vector at 250K.
We came off PRM approaches at 2151 and the folks that came in on their day off got to go home after about 3 hours work.
Effectively the tower needs a radar standard between the arrival and the departure; so 3 minute spacing allows for a departure between each arrival. If the arrivals are more tightly spaced; i.e. 5NM apart on final (the normal rate) in such conditions due to not being able to sight the arriving aircraft the tower can’t ‘fire’ the departure. So you can arrive two closer than 3 minutes even in PRMs; but not get a departure away too.
During PRM approaches the general concept is, due to the huge length of final it’s inefficient; this isn’t actually the case; yes, it’s not as efficient as visual conditions but it’s better than full dependent ILS approaches; see more below.
So the other morning we were on 40 arrivals and 40 departures an hour = maximum capacity (by law).
However, CTMS was at play and on ground delays which are strategic by nature didn’t equal the arrival rate; the CTMS rate was 34. So we are ‘expecting’ 6 slots not fully utilised. Why? Well when the CTMS program was run at 0500; it looked like the capacity would have been 34 Arrivals an hour; 17 on each runway; this configuration happens when we use 16 Dependent ILS Approaches.
PRM in Sydney is only staffed for in an adhoc at call manner; i.e. we only use it when people agree to come in on their day off. So at 0500 it wasn’t likely that enough people were going to say yes (2 of them). So rather than running CTMS rate of 40 and only achieving 34; and costing heaps of tactical fuel burns they ran it at 34. The PRM consoles are independent positions; when PRM is open all 12 consoles in Sydney are open and the room buzzes; but what do I know about such things, I’m based in Melbourne. CTMS was re-calculated around 0700; but the extra slots created were not fully utilised.
This is where effectively we use a radar standard between arrivals operating to different runways; in the SY case there is less than 1NM between centre lines; so to establish them in a dependent stream it requires spacing such as this.
Dependent Approaches
PRM Approaches
The advantage of PRMs is that if required you can have arrivals tighter than the ‘nominate acceptance rate’ on the same ILS; possibly swapping a departure slot for an extra arrivals slot etc; without effecting what’s happening on the other runway with dependent approaches; what ever you do on one ILS in terms of spacing has an effect on the other runways spacing too.
So back to what I do. The sequence here.... Just talking about the RWY16R sequence.
I’ve taken the liberty to include the savings in time (due to high speed and track shortening) into account across the averages. Things to note; between 2017 and 2054 the runways is at effective maximum capacity; then the CTMS rate of 34 left a few holes, basically 3 nine minute gaps. From 2127 until 2151 again its a maximum capacity.
Another thing to consider is we deal in whole minutes for the purposes of MAESTRO and flow; but the realities of the beast is is we have 150 seconds (2.5 minutes) between arrivals or a rate of 48 arrivals an hour; we actually use this rate (or tighter at times). So early or late at a fix does transpose into the real sequence spaces not the flowed spaces.
The nuts and bolts about how this one happened: QFA42 was slowed to follow EA2202; VOZ401, VOZ809 and QFA730 were given 250Kts and a vector to follow QFA42. HVN783 was given DCT to RIVET with high speed to follow QFA730; as was JST761.
VOZ811 and QFA408 were actually vectored to follow JST761 for separation, even though it appears there was no delay. VOZ619 was given DCT RIVET with high speed. QFA412 was untouched and QFA130 joined in from BN sectors (using my runway); QFA586 was untouched and RXA514 was shortened up on the non-jet STAR.
Then there were the gaps and all aircraft got high speed descents. CPA023, CAL051 and CES561 joined the sequence via BN sectors. QFA414 was given a crew managed delay time for RIVET; i.e. “adjust speed to cross RIVET at 13 at 250K.” Note it’s 23 minutes from RIVET at 250K (45NM SY) via the PRM approach to touch down.
SIA231 was vectored at cruise and given slow speed on descent (250K) to make RIVET at time 19; but later it became apparent that they wouldn’t make 19 (cause they got low); so they were brought back to profile speed; QFA740, VOZ821 were vectored to follow SIA231 and descended at 250K.
QFA564 (Canberra Sydney) was given a ‘strategic’ slot for departure to make good a landing of 2150; they got away early so were estimating the field at 2145; but the delay was need to make a landing of 2151; so they got a vector at 250K.
We came off PRM approaches at 2151 and the folks that came in on their day off got to go home after about 3 hours work.
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