Airport congestion in New Zealand

Abstract

The phenomenon of airport congestion at New Zealand's major airports is the subject of this research thesis. A growing problem in New Zealand, the importance of understanding this problem and identifying options for solution is high. The intention of this research was to identify the extent of congestion at New Zealand airports; to estimate the industry cost of congestion; to identify the causes of congestion; to estimate future levels of congestion; and to offer suggestions for solution of this problem.

Actual levels of airborne delay for flights arriving at these airports have been measured, and the industry cost of this delay in terms of time and fuel burn is estimated. Airport capacity for Auckland, Wellington and Christchurch airports is established and compared with the levels of demand for service. The level of delay attributable to excess demand is thus established. Comparison of differing airports' capacity levels indicates some level of delay attributable to air traffic control procedures. The majority of current delay is directly attributable to demand schedules which are characterised by grouping of demand - i.e. the scheduling of several aircraft at the same time, followed by periods of little or no demand. At Auckland and Christchurch airports, the current levels of airborne delay is due exclusively to scheduling patterns. Demand exceeds available capacity for many short periods throughout the course of the day, but is interspersed by a greater number of periods where capacity exceeds current demand. The delays experienced at these airports is also low – averaging approximately three minutes per aircraft.

Similar levels of delay are experienced at Wellington airport during weather conditions which meet visual or instrument above circling minima criteria, but delays rise markedly when weather conditions fall below this criteria. This is due to the differing air traffic control procedures which must (for safety reasons) be invoked during these conditions, and result in a decrease in airport capacity. Instrument conditions below circling minima occur approximately 11% of the time at Wellington, compared with approximately 3% for Auckland and Christchurch. Moreover, weather conditions below circling minima do not necessarily reduce the capacity of Auckland or Christchurch airports.

Forecast increases in demand over the next twelve years, when compared with available airport capacity indicate future levels of delay at extremely high rates for Auckland and Wellington airports which are currently operating at levels close to capacity. At Auckland, management of aircraft schedules is sufficient to provide a solution until 2005. Forecast levels of demand beyond this indicate that a greater level of solution will be required. These issues are likely to be addressed by the addition of a second runway.

At Wellington airport the problem of congestion is more severe. Capacity is well exceeded by present levels of demand during weather conditions below circling minima, and is reached during instrument conditions for significant periods. There is little available capacity for future growth. Terrain and cost issues make additional runways for Wellington airport unfeasible options. It is essential then, that the available capacity of Wellington airport be managed with regard to available capacity. This must take the form of schedule management, and restrictions on aircraft types during busy periods.

The primary cause of capacity degradation during weather conditions below circling minima is increased separation provided by air traffic control to keep aircraft safely separated in the event of a missed approach. Where the performance characteristics of the aircraft using an airport are similar, and minimal wake turbulence separation applies, then it is not necessary to increase separation between aircraft to provide this protection. In other words, if all aircraft using Wellington airport are restricted to a similar size and have similar speed and climb performance, then capacity will not be degraded during weather conditions below circling minima. As well as providing a constant capacity, standardisation of aircraft types will provide a small increase in that capacity.

This is the only feasible solution to a growing problem at Wellington airport. It should be implemented immediately to both relieve current congestion and to prevent future levels of delay which are forecast to reach 1 hour duration by 2000 and exceed 6 hours by 2005.