By Paul Bibby
FLIGHT path changes which produced a significant increase in air traffic over a string of southern Sydney suburbs are partly the result of a broader policy of concentrating aircraft movements across the country.
Residents from Five Dock to Miranda have borne the brunt of a tenfold increase in the concentration of aircraft movements over their homes since the middle of last year, which they say has resulted in excessive aircraft noise. Flight density maps show the frequency of flights over these suburbs increased from 180 per quarter to at least 1800, and the flight path corridor has been narrowed from 6.8 kilometres to just 200 metres.
Airservices Australia disputes these figures, saying there has only been a threefold increase in traffic. It said aircraft using this flight path were at heights between 5000 and 6000 feet, ''above the intrusive noise threshold''.
Yesterday Airservices Australia said the extra air traffic was primarily the result of runway safety works at the airport which meant flights had to be diverted from their normal paths.
But the regulator's own data shows the stream of aircraft began to appear in the second quarter of last year - at least three months before the runway works began. It has now emerged that the concentration on this flight path is partly the result of a series of changes introduced by the regulator over a number of years, in combination with the introduction of new avionics technology, which has funnelled aircraft into narrower corridors.
An Environmental Assessment prepared by Airservices shows that in 2004 it introduced a change to the standard arrival procedure - the path planes take as they come in to land - in the full knowledge this would increase the concentration of aircraft.
''The current lateral spread on the overland segment of the runway 34l … tracks is between six kilometres and eight kilometres … This [is] expected to reduce to between 1.1 kilometres and 1.6 kilometres,'' it said.
Four years later, in June 2008, Airservices made a further change to the arrival procedure. This change corresponded almost exactly with the emergence of an even more highly concentrated stream of aircraft. The regulator did not respond when asked whether the changes produced the increased air traffic.
However, it confirmed the introduction of new navigation technology meant planes were now following more concentrated corridors as they came into Sydney. ''The precision with which aircraft can fly the approach has improved over the years as new aircraft avionics have been developed,'' a spokesman said.
The concentration of air traffic as it approaches Sydney is part of a broader policy by Airservices Australia to improve the efficiency of aircraft movements to save time, fuel, and cope with limited space at airports.
The president of No Aircraft Noise, Alan Rees, said the policy flew in the face of the Long Term Operating Plan (LTOP) for Sydney Airport which says noise impact should be reduced by spreading out rather than concentrating aircraft movements. ''It's all very well to have high-tech computerised arrivals, but if you don't implement the operating plan it's completely counter productive,'' he said.
But the Federal Transport Minister, Anthony Albanese, said that the changes were not inconsistent with the LTOP. ''There is nothing new here - we're talking about a 4 per cent increase in arrivals and departures using this path and they are using it at a great height,'' Mr Albanese said.
''We have a … consultation process with the Airport Community Forum and the LTOP implementation committee and they agreed to what was happening.''