Flight paths and tall buildings in Melbourne explained

Earlier this year issues regarding the impact that flights paths around Melbourne's airports and development of tall buildings in central Melbourne were raised following the then approval of Australia 108 tower which at 388 metres high would have been the tallest building in Melbourne and the Southern Hemisphere. Since this issue was initially raised there has been a lot of confusion and misunderstanding in relation to how airspace restrictions work and how they impact upon development in Melbourne. With developers proposing increasingly taller buildings in the Melbourne's CBD and Southbank, this issue will become even more prominent in the future.

Airspace around airports in managed so that aircraft can take off, land and maneuver around airports without risk of colliding with buildings or other structures. To do this the areas surrounding airports are protected by two invisible surfaces which define at what height planes can fly safely without encountering unexpected obstacles. These surfaces are known as the:

  • Obstacle Limitation Surface (OLS); and
  • Procedures for Air Navigational Services—Aircraft Operations Surface (PANS-OPS)

OLS is generally the lowest surface and is designed to provide protection for aircraft flying into or out of the airport when the pilot is flying by sight. PANS-OPS is generally above the OLS and is designed to safeguard an aircraft from collision with obstacles when the aircraft’s flight may be guided solely by instruments, such as in poor visibility conditions. Buildings and other structures cannot penetrate these surfaces without the approval of the relevant Airport or the Department of Infrastructure and Regional Development.

Permits can be granted for permanent or temporary buildings or structures to penetrate the OLS and approval would usually involve a requirement that the building have prominent navigation beacons at the highest point of the building. An example of this is Eureka Tower which was required to have four navigation beacons on the roof as it penetrated the OLS.

Essendon Airport OLS

A permit can also be granted for temporary structures to penetrate the PANS-OPS surface, an example of this were the construction cranes for Eureka Tower that were issued a permit to penetrate the Essendon Airport PANS-OPS on a temporary basis during the construction of the building. However a permit cannot be issued to allow for structures to penetrate the PANS-OPS surface on a permanent basis. In order to construct a building that would permanently penetrate the existing PANS-OPS surface, the PANS-OPS surface has to be amended so that it shifts above the height of the proposed building.

An example of which was the PANS-OPS surface over the Gold Coast which was amended in 2005 to allow for the development of Q1 Tower. The PANS-OPS surface surrounding the site of Q1 tower was 304m above sea level and the spire on Q1 was originally approved at this height. The developers of Q1 successfully applied to have the PANS-OPS surface increased to 335.3 to allow for the spire to be extended to a height of 328m above sea level.

The location and orientation of Melbourne Airport means that the controls to protect Melbourne Airport have very little impact upon development in the Melbourne CBD (including Docklands and Southbank). However the controls for Essendon Airport have a much more significant impact upon the Melbourne CBD, as the Essendon airport OLS map above shows. OLS over the Melbourne CBD (including Southbank and Docklands) is 228.5, while the Essendon Airport PANS-OPS map shown below indicates heights of between 265m and 315m over Melbourne CBD (including Southbank and Docklands).

Essendon Airport PANS-OPS

As a result of the above requirements buildings in the Melbourne CBD cannot exceed a height of between 265m and 315m depending on their exact location. For example, the PANS-OPS over the site of Australia 108 is 312m and the design of the building is currently being amended so that it is below this height.

One issue that was raised during the processing of the application for Australia 108 was that it was clear that the developer, the City of Melbourne and even the planning department were not aware of these requirements or presumed that a permit could be granted to penetrate the PANS-OPS. Currently there is nothing in the City of Melbourne Planning Scheme that notifies developers where these restrictions apply or that buildings above a certain height may be prohibited or need additional permissions. This had led to situation where buildings have been approved that penetrate the PANS-OPS such as Australia 108 and the tallest proposed building on the Carlton Brewery Site. The tallest of the four proposed towers at 250 Spencer Street would also penetrate the PANS-OPS.

Essendon Airport have recently prepared a new draft master plan for the airport which is on public exhibition until the November 29th. The master planning process can include changes to prescribed airspace although the draft master plan does not include any proposed changes to the prescribed airspace around the airport. It is understood that the PANS-OPS restrictions over the CBD are not required to protect a direct flight path for aircraft taking off or landing at Essendon Airport but to provide a safety buffer for planes in emergency situations where they encounter difficulty after take off or have to perform a go-around where a pilot discontinues a landing approach when they are not completely satisfied that the requirements are in place for a safe landing.

Victorian Planning Minister, Matthew Guy, has informed Urban Melbourne that he is currently lobbying the Federal Government to amend the PANS-OPS restrictions so that they do not apply to the Melbourne CBD. It is considered that the current PANS-OPS requirements for what is only a secondary airport place unreasonable restrictions on the development of the second largest city in Australia. It is also believed that the PANS-OPS restrictions could be removed from the Melbourne CBD while maintaining aviation safety standards, which if realised would likely propel a number of Melbourne's proposed towers into a whole new stratosphere.



MelbourneGuy's picture

Thanks for this comprehensive and detailed explanation. It does explain a lot and hopefully these restrictions will be lifted.

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troy's picture

I Agree.

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Planet Dweller's picture

Thanks Nicholas for an excellent article, not an easy task when trying to give some clarity to airspace regulations.

I will add an additional bit of information that might help others understand, the OLS and PANS-OPS surfaces are considered to be hard surfaces and aircraft have a further regulated distance they need to fly above those surfaces called the minimum safe altitude, this will generally be at least a kilometre or more depending if you are flying visually or on instruments.

If the OLS or PANS-OPS surface was shifted upwards to take into account, as an example, an additional 88 metres for Australia108, the minimum safe altitude requirement would just push aircraft up the additional 88 metres.

As a last point, whilst not supporting in any way the intractability of CASA to changes, it needs to be acknowledged that any change to the current OLS and PANS-OPS surfaces will need to be communicated to all pilots who may fly into Melbourne and a data update to all flight management systems of aircraft that fly into Melbourne.

The challenge is not the shifting of the OLS or PANS-OPS surface but making sure everyone is aware of the shift.

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