Sydney Airport Delays Continue

Ultimately, the parallel runway will provide some added capacity at Sydney airport, however, this is not expected to be completed until mid 1995 and indications are that the total number of fixed wing movements this year, will exceed that of our record year in 1988, when over 207,000 fixed wing movements were recorded.

CAA continues to examine and implement ways of increasing the capacity of Sydney Airportfor the critical period before the parallel runway is operational. Currently, CAA staff are examining new methods of directing traffic to busy airports, similar to the “star system” in the US and they are also examining the use of separate runways for takeoff and landings, which should provide added capacity. CAA has also offered industry the services of its Air Traffic Flow Management Unit and in particular, its departure control programme which has the potential to keep airborne delays to a minimum.

Sydney Airport Runway Capacity

The capacity of Sydney Airport primarily depends on the runway orrunways in use at any given time. Air Traffic C ontrol selects the runway(s) in accordance with established noise abatement procedures and the prevailing weather conditions. Other significant factors that affect runway capacity include the use of Simops, and the traffic mix during Simops.

Information provided by CAA at an industry meeting in December 1991, revealed acceptance rates for the number of arrivals per hour at Sydney Airport that can be processed by the air traffic system. The maximum arrival acceptance rate was 26 movements per hour which applied from 0700hrs to 2100hrs except during the peak hours (0800-0859hrs and 1800- 1859hrs) when the acceptance rate dropped to 23arrivals per hour due to a poor traffic mix.

Given that acceptance rates for aircraft arrivals at Sydney Airport are afunction of capacity, the practical capacity ofthe Airport for any given hour can be defined as twice the arrival acceptance rate forthat hour. Therefore, the practical capacity of Sydney Airport on a typical busy day with simultaneous operations and noise abatement procedures in effect, is 52 movements per hour. However, when peak period surcharges apply, the capacity drops by 6 movements per hour to 46, simply because of the reduced number of smaller aircraft, such as the J31, Dash 8 and Twin Otter. These aircraft are generally not available, because of the surcharge, to take advantage of independent arrival and departure sequences which are a feature of simultaneous runway operations. These six slots could be used by the smaller regional aircraft without detriment to congestion and delays during the periods when charges apply.

Cause of Delays

The cause of arrival and departure delays is simply that too many aircraft are positioned to use the same facility,for example the runway, at the same time.

To take a hypothetical scenario, assume that aircraft can take off at one minute intervals from a given runway and that ten aircraft taxi out to that runway at the same time. The first aircraft takes off without any delay, whilst each of the remaining nine aircraft experience a delay of one minute. The second aircraft takes off and each of the remaining eight aircraft experience a further one minute delay and so on until the last aircraft departs nine minutes after arriving atthe runway. The total delay is the sum of all the individual delays that the aircraft experience, that is 9 + 8 + 7 + . . . + 1 minutes which add up to 45 minutes.

This cluster of aircraft would cause 45 minutes of fuel to be wasted unnecessarily in a ten minute period. If the same ten aircraft were presented at the runway at one minute intervals, then no delays would occur.

Atfive minute intervals,the total delay would be ten minutes which equates to 120 minutes per hour.

The same principle also applies to arriving aircraft and in practice, particularly at Sydney Airport, both arriving and departing aircraft vie for the same runway concurrently, many times throughout the day, forming serious clusters that cause extended delays. Whilst departing aircraft can sit on the taxiway awaiting their turn to use the runway, airborne aircraft must be held in patterns until they can be sequenced into an available landing slot.

There are many variables that can cause aircraft to cluster, such as thunderstorms, fog, wind, visibility and some aircraft unserviceabilities, which cannot be controlled by industry.

However, one factor that can be controlled by industry is scheduling. If airlines schedule more movements than the airport can handle at any given time, then serious delays are likely to occur. This applies both to short term clusters as well as to the hourly capacity. Industry is best placed to schedule movements within the capacity of the airport, to determine the right mix of aircraft, to ensure maximum operating efficiency of the Airport and to establish rescheduling guidelines when weather conditions are less than optimum.

Failure to do this will encourage the Federal Government to impose more stringent regulations to control the number of aircraft accessing airports during the busy periods.

Traffic Management

Options for managing traffic within the maximum capacity of an airport include slot allocation, surcharges, industry schedule coordination and use of CAAATFMU.

• Slot Allocation System – A system of slot allocation would place rigid constraints on operators to arrive and depart within allocated times. Those unable to meet their slot allocation on arrival would be required to hold until the next appropriate slot becomes available or divert to another aerodrome. This would be a Government imposed restriction that offers little flexibility.

• Surcharges – Current figures indicate that the peak period surcharge will need to be increased and be extended into the shoulder periods, if this remains the only method of reducing demand during these busy periods.

• Industry Schedule C oordination – The Industry Schedule Coordination Council has the potential to control the mix and the rate of aircraft movements by industry consensus. It has the potential to be flexible and to allow for new entrants. Unfortunately, it appears to have been completely ineffective since its formation.

• CAA ATFMUDD – The CAA Air Traffic Flow Management Unit (ATFMU) has offered to provide its departure control programme and flow management services to industry in an effort to reduce airborne delays at Sydney and Melbourne Airports. However, despite tests that have proven the ATFMU system in practice, industry has surprisingly shown little interest in the service.

The potential of the ATFMU to correct anomalies in real time should not be overlooked. Despite the best efforts of industry to coordinate schedules, the possibility still exists for congestion and delays to occur, particularly through the effects of weather. The ATFMU departure control programme, in particular, has the potential to save industry millions of dollars annually by real time rescheduling and by holding aircraft on the ground instead of in airborne holding patterns.

Peak Period Surcharges

The effect of the peak period pricing regime on GA movements at Sydney Airport over the last year has had the desired effect of drastically reducing demand. However, the effect of the surcharges on RPThas simply been to move the traffic peaks to the shoulders and to reduce the capacity of the Airport during peak periods. This inefficient system will be perpetuated if the pricing regime is extended into the shoulder periods. Unfortunately, in the absence of any other initiative to match demand to capacity at Sydney Airport, FAC will have little choice but to increase the peak period surcharge and to extend it into shoulder periods.

If the FAC intends to continue or extend the peak period pricing regime, then it should release the six slots per hour that jet aircraft cannot use to regional aircraft for use during simultaneous operations. This could release as many as 36 slots per day, depending on the extent and level of the new surcharge regime, during prime time without causing any additional delays. Further, such action will be essential to increase the ATC acceptance rate during those hours when surcharges apply and to maximise the efficiency of Sydney Airport.

Industry Control

There is only one method by which industry can control its own destiny in relation to access to Sydney Airport during the busy periods. That is by having an active and effective industry schedule coordination council. Schedules need to be contained within the capacity of the airport and the right aircraft mix must be used to maximise airport capacity during simultaneous operations.

In conjunction with controlled scheduling, industry should also support the CAA ATFMU departure control programme. This programme will modify schedules and adjust movements in real time, when necessary. Such action will ensure minimum airborne delays and should result in a huge cost saving benefit to the industry.

An industry controlled system also has the advantage of being readily adaptable to take advantage of any increases in capacity that may occur though further CAA initiatives.