Back story

On 14 September 2017, without prior notice or consultation, Airservices Australia implemented a new automated satellite-only air navigation system (RNP1 SIDs and STARs) which concentrates aircraft on narrow paths over quiet rural and coastal communities.

Hobart is a test case for the rollout of this system at many regional airports in Australia.

Currently, up to 40 flights per day travel directly over, or immediately adjacent to areas on Tasmania’s South East Coast - most of which have never been overflown by commercial jet aircraft.

How is the new system different?

Prior to September 2017, there were no ‘flight paths’ as such at Hobart. Pilots were given instructions by local air traffic controllers to occupy a specific sector of airspace, and the authority to navigate the most efficient route to and from the runway. Navigation was either by ‘visual’ means, via a ground-based navigation beacon (known as a VOR) or using instruments in conditions of poor visibility.

Example pre-September 2017 arrival spread - visual (purple), VOR (green), instrument (blue) navigation

Example pre-September 2017 arrival spread - visual (purple), VOR (green), instrument (blue) navigation

This provided maximum flexibility to deal with changing weather and traffic conditions.

The new system replaced all of these options with a single satellite-based system, similar to GPS. All capable aircraft are required to use their on-board computer and GPS to safely navigate along a fixed path - somewhat like using Google Maps to drive your car for you.

Although in theory this reduces the need for manual (human) control, like many automated processes, the new system lack flexibility. It must therefore be carefully designed to avoid conflict, be compatible with aircraft capability, and have sufficient back-up in case of failure. The fact that all aircraft are on the same path and travelling at different speeds also requires careful ‘longitudinal separation’ to minimise the change of a rear-end collision.

Current arrival corridor post September 2017 - RNP1 navigation (green).

Current arrival corridor post September 2017 - RNP1 navigation (green).

SYSTEM FAILURE

Post-implementation it was discovered in Hobart that aircraft were incapable of adhering to the paths as designed, creating potential conflicts at a crossing point above the township of Richmond. A string of incidents, including two ‘loss of separation’ events (the most serious class of incident) involving commercial passenger jets, occurred within 3 months of implementation.

Consequently, Airservices was forced to issue a temporary instruction to local controllers to revert to manual management of aircraft. Unfortunately the removal of the previous navigation options meant that aircraft have to continue flying along the new tracks, resulting in an increased workload for pilots and controllers and longer miles than the previous system.

It was also discovered that many aircraft did not have the required technology, certain paths (e.g. to Antarctica and South West Tasmania) had been ‘forgotten’. Since all aircraft travel on the same track, it was also realised that slower aircraft tend to slow down faster jets, further contributing to excess flight times and fuel costs.

AIRSERVICES REVIEW

The incidents, sustained pressure from airlines and affected residents, a Federal Court challenge, questions in federal parliament and an investigation by the Aircraft Noise Ombudsman forced Airservices to conduct a ‘greenfields’ review of the flight paths.

After spending $1 million on the review, Airservices’s new proposal - which has a 20 year planning horizon - still retains the problematic RNP1 SIDs and STARs, but adds a confusing array of ‘special purpose’ paths, to cope with the lack of flexibility

No radar, no visual flight options, no ground-based navigation, and the major jet paths are left essentially unchanged.

And Hobart International Airport’s classification as a regional airport remains unchanged.

If the Airservices proposal is allowed to go ahead, Hobart will be left with a less safe, less efficient and more environmentally damaging system than before.