The big picture

Whether it is the rapid-fire chat at LAX, or the measured responses at London’s Heathrow Airport, air traffic controllers seem to have a style that reflects their national identity. As I entered the reverse fish-bowl of Sydney Airport’s control tower, the truism was immediately apparent once again. The team of controllers gave an air of relaxed efficiency, attired in golf shirts and runners, moving aircraft around at an even pace with an even tone. It was distinctly Australian.

Controllers communicated with pilots and co-ordinated with each other in a very calm surrounding, void of extraneous noise and raised voices. Every move and word was executed in a style that suggested a minimum of fuss, yet wary that any number of selected spanners could be thrown into the works without notice. Such choreography doesn’t just happen, but results from thorough training and ongoing monitoring and like a well executed dance sequence, it only seems effortless.

Overseeing proceedings on the day of me visit to Sydney Tower is Philip Mulhall. Carrying through the relaxed professional theme of his surroundings, Phil is cordial and accommodating, but can switch mid-sentence to attend to any issue arising from his team. His team is seated radially about the tower’s generous glass windows, performing varied functions. There is Surface Movement Control (SMC East and West), Air Traffic Control (ATC East and West), Airways Clearance Delivery (ACD), a roving co-ordinator and Phil in his supervisory role. Fundamentally, SMC West handles the taxiways on the international side of the airport, while East works the domestic taxiways and aprons. ATC East manages runway 16L/34R, while his western counterpart is responsible for the longer 16R/34L and the cross runway of 07/25 when it is in operation.

The controllers man their stations for about two hours between breaks and during peak periods there is not much reprieve. Controllers can ultimately fill any seat in the tower, though generally they are qualified on half of the ‘seats’ initially before being fully endorsed after two years. Such interchangeability offers more than flexibility, but an intimate understanding of the other controllers with whom they must co-ordinate seamlessly.

Each work station consists of three primary ‘screens’. There is the TAATS airborne radar, the ASMGS ground radar and unique to Sydney Tower, the MD-PDS which gives provides constant access to meteorological data, the ATIS, maps, navaids and so on. For ergonomic efficiency, the layout of each station is the same, further assisting any transition between the positions. Yet for all of the high-tech wizardry, there remains the ever-present ‘strips’; paper forms on colour-coded plastic holders that are managed and sorted depending on the aircraft’ status and position. When it comes time for the SMC controller to hand over responsibility for an aircraft to ATC, or vice versa, the strip is pushed around the rails that border the consoles like a slot-car track.

As aircraft after aircraft arrives and departs, Phil explains that the main threat to the operation exists in the form of runway crossings. To safeguard, there are physical separation buffers required as well as the positive co-ordination between controllers in addition to their current focus. And this can take time. This is why the crew of an aircraft waiting to cross a runway sometimes queries why they didn’t cross in an apparent lull. Unfortunately, there is often a lot happening during that ‘lull’ to safely execute a crossing.

The weather also plays a major hand in the intensity of the operation. The worse the weather becomes, the required separation between aircraft becomes greater and this reduces the movements per hour. The Standard Instrument Departures (SIDS) on the parallel runways have an inbuilt design to diverge the aircraft by 15 degrees, but when the storms roll in and vectors are required after take-off, this separation falls to a more manual means.

The controllers are also working within a system that limits their flexibility to a degree. The noise-sharing requirements at Sydney Airport that call for changes to runway configurations, the default assignment of runways unless otherwise operationally required and most recently, the ‘cap’ on movements. This latest operational requirement limits the airport to 80 movements per hour and is another aspect that needs to be managed. Phil acknowledges that it’s a “work in progress”, but already a system has been designed to meter the movements. It involves an additional person counting the arrivals and monitoring the departures with a threshold of 70 movements set to signal that the ‘cap’ is approaching. Roughly equating to 9 departures in a 15 minute block, if 70 movements is flagged to be exceeded Phil and his team need to manage the situation closely.

Yet for all of the equipment, co-ordination and system parameters, one of the most impressive aspects of the operation is the management of the constant interruptions. Distraction and interruptions are a constant threat on the flight-deck, but in the control tower they seem to be ever-present. For all that was happening, within about two minutes there was a reported bird-strike, a query from a recently arrived overseas carrier and an A330 taking a slightly different scenic taxi route. In isolation, none of these were major events, but considering their ramifications and co-ordinating them while maintaining normal operations is undoubtedly a challenge. In many cases, the relevant controller refers it to Phil to handle and carries on with the primary task of controlling. As I speak to him, Phil senses the issue with his third ear, attends to it immediately to his satisfaction and then walks back to me and picks up the sentence where he left off. The whole operation in the tower hardly breaks stride. It’s an impressive example of teamwork and focus.

Even so, the team in the tower are just one aspect of the greater traffic management system. Just as they co-ordinate amongst themselves, they also need to co-ordinate with those controllers transitioning the arrivals and departures from the air routes to the terminal airspace; the team at the TCU.

The Guys Downstairs.

As I watched the goings-on in Sydney Tower, they frequently referred to the “guys downstairs”. Having passed a security guard and a coffee room on my way up the tower, it was not obvious to me who they meant. In fact, rather than being downstairs, they were referring to the controllers situated on the far side of the airport at the site of the former control tower. The ‘guys downstairs’ are actually the Terminal Area Controllers located at the TCU, or Terminal Control Unit.

If Sydney Tower is the bottle, then the TCU is the funnel that empties and fills it. Air traffic control radiates from airports in a series of arcs and the TCU handles the airspace out to 45nm and up to 28,000 feet (F280). Through approach and departures controllers who in turn feed into a series of ‘directors’, the aircraft are brought from their inbound routes and established on the centerline of their arrival runway. Similarly, they are fed from their take-off and established on their outbound tracks. The controllers themselves are seated at a bank of radar screens, flanked by maps of the surrounding airspace and unfortunately not supplied with the outstanding view shared by their tower workmates.

As always, separation between the aircraft is of prime importance. Many of the arrivals and departures are designed with tracks and crossing heights to ensure separation, but once again the many variables including weather can serve to interrupt the best laid plans. Furthermore, in addition to safely sequencing the aircraft, the goal is to maximise efficiency. Much of this responsibility falls to the ‘flow’ controller.

Utilising the ‘Maestro’ system, the flow controller aims to time the arrivals from pre-designated inbound points, or ‘feeder fixes’, to touchdown with to-the-minute accuracy. To facilitate this, the controller feeds ‘Maestro’ in a wealth of information including the runway configuration, wind and the predicted, or assigned, time at the feeder fix. However, the situation is so dynamic that it needs to be continually monitored and fine tuned by the controller, who today is Peter Brackley. Inadequate separation may result in vectors, speed reduction or holding for the aircraft, while a window of time can translate into track shortening or a cancellation of speed restrictions.

As the weather fluctuates and separation standards ‘on approach’ increase, this timing needs to be absorbed well before the aircraft turn onto final. Similarly, a change in runway configuration, particularly a 180 degree direction change takes time. This loss of minutes equates to a reduction in movements and needs to be co-ordinated and often with minimal notice as the wind can be a fickle friend. Similarly if the delays on one runway build up, the flow may intervene and reassign runways to inbound aircraft. The ‘flow’ may utilize a computer system, but it is a case of art meeting science when the myriad of variables arise.

In addition to their scheduled arrivals from controlled airspace, the TCU has to deal often unscheduled traffic ‘popping up’ out of uncontrolled airspace, such as Sydney Harbour scenic flights. Similarly, the arrival of the regional operators into their airspace, whilst not unannounced, can only be accurately scheduled into the flow when they are positively identified by radar. For most of the sequencing, the floe starts to get good radar data at around 160 nautical miles from Sydney, depending upon altitude.

The TCU is also home to the ILS PRM approach system with a dedicated screen and station for the purpose. The Precision Runway Monitor (PRM) is a highly accurate air traffic surveillance system designed to maximise air traffic flow to parallel runways during periods of inclement weather. However, it also requires additional staff to man the station and often their simply aren’t enough hands on deck to operate the PRM. Even so, the PRM is giving way to the Wide Area Multilateration (WAM) system, to Supplement Existing Radar Coverage and
provide Precision Approach Monitoring for Parallel Runway Operations by utilising 16 ground based sensors.

Another system designed to assist the flow into Sydney Airport is the Central Traffic Management System (CTMS). Only utilised in Sydney and Perth, CTMS is designed to minimise airborne delays by controlling departure times on the ground at the place of origin. To many flight crews, the system doesn’t seem to work as holding is still a way of life even when the departure is delayed. Interestingly, the controllers highlight that a limitation of the CTMS is that arrivals into Sydney outside of a radius extending to Adelaide are all factored in as being on time; obviously this is not the case. As a consequence, these errors in time impact upon all arrivals. Like PRM, CTMS is set to be superceded by a new system known as Metron Traffic Flow in an effort to enhance airspace efficiency.

Like their counterparts in the Tower, the team at the TCU seem to be expert in managing the unexpected without becoming distracted or perturbed. It is a hive of activity without the corresponding noise level one would experience in a similarly sized office space. All in all, it seems to be all about efficiency.

The Big Picture.

As a pilot or passenger, disruptions stemming from air traffic control are often frustrating. However, much of this frustration stems from an inability to readily understand the reason behind the delay. Yet like the flight deck, an absence of chatter is rarely an indication of a lull, in fact the contrary is more often the case. For a single instruction or slot time, a great deal of co-ordination, communication, procedural application and judgement has taken place. All of this is necessary to ensure that safety remains the overriding factor in efficiency.

As with so many aspects of life, it is the thankless work behind the scenes that determines the quality of the finished product. And so it is with air traffic management and the men and women who man the binoculars and radar screens. Day after day they safely sequence a mass of aircraft into and out of our capital cities while working within the constraints of the system and coping with the unbelievable amount of variables that are thrown up before them.

In reality, if our worst complaint is a delay, then safety may well have been the winner. Given the dynamic nature of co-ordinating air traffic in the ever-changing environment of the sky, the vast majority of operations through our airports may appear seamless. However, to the controllers that ‘push tin’ safely around our skies they know just how many aspects of the plan have to come together. Maybe they really do have the ‘Big Picture’.