Aviation Impact on Building Development in the Melbourne CBD
Airspace regulations surrounding Essendon Airport are placing a restriction on the maximum height for high rise building developments being planned for the Melbourne central business district (CBD). The development community is fast learning the impact of these regulations and contemplating how to undertake proposed developments in light of these restrictions.
By way of background, the state planning laws administered by the Department of Transport, Planning and Local Infrastructure (DTPLI) are distinct from the federal airspace regulations administered by the Department of Infrastructure and Regional Development. These aviation regulations apply in all states of Australia and are contained in the Airports (Protection of Airspace) Act 1996 (The Act).
In essence The Act seeks to protect the airspace around an airport that are required for aircraft operations from proposed building or other physical encroachment. It is intended to ensure that aircraft operations in, out and around an airport can be performed safely.
The Act requires that an airport owner-operator designate prescribed airspace when air transport operations take place. There are two types of prescribed airspace, an obstacle limitation surface (OLS) and PANS-OPS surface. It is important to emphasise that a planning permit granted by DTPLI does not enable a building to enter the prescribed airspace around an airport. Separate approval must be gained from the Department of Infrastructure and Regional Development.
An OLS provides protection for general aircraft operations around an airport. It caters for aircraft flying visually or under instruments. An OLS defines various categories of obstruction surfaces surrounding a runway. It extends outward to a maximum of 15km from the airport. Regulations prevent the construction or placement of obstructions in the surfaces closest to the runway. However, obstructions can be placed in other surfaces subject to there being no significant risk to aviation safety.
The other form of prescribed airspace is the PANS-OPS surface (an abbreviation for Procedures for Air Navigation Services-Operations), which protects airspace for aircraft flying under instrument flight rules (termed-IFR) around an airport. When an aircraft is flying IFR it is presumed that it cannot see the ground until it is close to landing, or perform its own separation from other aircraft or physical obstructions on the ground. These aircraft determine their position from ground based navigation aids or satellites. They fly on defined flight paths when arriving and departing an airport. Most air transport operations are undertaken in accordance with IFR requirements.
Regulations governing the PANS-OPS surface are significantly more restrictive than those for an OLS. No permanent obstruction is permitted in a PANS-OPS surface. A permanent obstruction includes buildings plus items such as lift overruns or aerials that may be placed on top of the building.
The Act does provide the opportunity for temporary penetration of a PANS-OPS surface. A temporary penetration can extend for a maximum of three months. Penetration of the PANS-OPS surface by a construction crane would fall within this categorisation. However, it is important to note that this temporary penetration of the PANS-OPS surface is subject to achieving the agreement of the airport operator-company.
Four organisations are identified in the Act. The Civil Aviation Safety Authority (CASA) is responsible for assessing the safety implications from a temporary or permanent application to enter an OLS or PANS-OPS surface. Airservices Australia is responsible for developing instrument flight procedures around an airport. It has ultimate responsibility for determining the height of the PANS-OPS surface. An airport operator-company manages the application process to enter prescribed airspace. The federal Department of Infrastructure and Regional Development is the agency responsible for granting approval for the application. An appeal process is available through the Administrative Appeals Tribunal.
The Melbourne CBD falls within the prescribed airspace of Essendon Airport. Essendon Airport Ltd (EAL) developed prescribed airspace (i.e. OLS and PANS-OPS surface) around the airport. The Melbourne CBD is located beneath an area designated as the ‘Outer Horizontal’ surface of the OLS.
This outer horizontal surface is a flat plane extending from around 5km to 15km from Essendon Airport. It has a lower level of 150m above the height of Essendon Airport aerodrome reference point. This means that the height of the OLS above the Melbourne CBD is 228.5m AHD. Building and other obstructions can enter the OLS provided there is no significant risk to aviation safety and with the approval of the Department of Infrastructure and Regional Development.
Helicopters operate in the OLS around the Melbourne CBD. One of the main strategies to mitigate risks to these operations is by placing lights on the top corners of the buildings. Cranes are required to have alternating colours along the boom. Strobe lights are also required to be placed at the top of the boom.
The height of PANS-OPS surface above the Melbourne CBD is governed by the missed approach associated with the ILS runway 26 at Essendon Airport. This missed approach procedure requires the aircraft to climb on a 130 deg track, toward the CBD. Unlike the OLS, the PANS-OPS surface rises at a 2.5% gradient from Essendon Airport. A 2.5% climb gradient is a commonly adopted performance standard. It assumes a modestly performing aircraft that has one engine inoperative.
The Melbourne CBD spans an area approximately 9-10.5km from Essendon Airport. Taking into consideration the gradient of the PANS-OPS surface, developments in the Southbank area can be built to a higher level than those planned for the northern fringe of the CBD. Maximum building heights on the northern fringe can be around 280m AHD, while developments in Southbank area are able to reach 320m AHD.
The issue of cranes used to construct these high rise developments presents far greater complexity, particularly for those buildings planned for just beneath the PANS-OPS surface. Cranes cannot penetrate the PANS-OPS surface for duration greater than three months.
Construction companies favor the use of a luffing tower crane for high rise developments. These cranes often require the raised boom to penetrate the PANS-OPS surface. A three month penetration is not adequate to perform the necessary construction activities for develops that sit just beneath the PANS-OPS surface. These developments will also be restricted by the maximum height penetration permitted into the PANS-OPS by cranes.
Construction companies are currently evaluating alternative construction methodologies and crane solutions to address this height penetration problem. This includes exploring whether ‘hammerhead’ cranes could replace the luffing form. Despite these initiatives, without a change to the three month maximum duration and having a suitable height penetration for cranes, buildings will probably need to be constructed to a lower height.
A penetration of the PANS-OPS surface requires a change to the flight procedures. This can mean raised approach minima for aircraft on approach to land, different flight paths to avoid an area of building development or the requirement for a higher climb gradient on a missed approach procedure.
Presently over a dozen high rise developments are mooted for the Melbourne CBD that will likely penetrate either the OLS or have a crane seek to enter the PANS-OPS surface. These developments will likely penetrate prescribed airspace during the period 2017 through 2020. From an aviation perspective, although no one construction crane may penetrate the PANS-OPS surface for more than three months, the cumulative impact of these developments will likely require revised flight procedures for most of this period.
Essendon Airport Ltd is currently undertaking a study to evaluate the impact on local aviation users from short term penetrations of the PANS-OPS surface. An expected outcome from this study will be a determination about the maximum height that construction cranes can penetrate the PANS-OPS surface. Unfortunately Essendon Airport Ltd has not agreed to consult with the development community as part of their study. The construction needs of the development community will not be factored into their evaluation. Essendon Airport Ltd has also refused to disclose the outcomes of the study to the impacted development community once it is completed.
Some years ago the Eureka Tower construction crane had a 150ft penetration into the PANS-OPS surface. The application of The Act has tightened since this development. It is unknown whether a similar level will be approved or a lower height penetration set.
Once the study reflecting the outcome from consultation with local operators is completed, it will be provided to the Department of Infrastructure and Regional Development. It is likely that the reports recommendation will be provided to Airservices and CASA for review. Essendon Airport Ltd will not provide a timeframe when their study will be finalised.
In the meantime, Essendon Airport Ltd and the Department of Infrastructure and Regional Development have expressed an unwillingness to process applications for developments where the crane may penetrate the PANS-OPS surface. This means that it could be the New Year before applications can be submitted. In the meantime, a number of developments are on hold while this matter is resolved.
The Department of Infrastructure and Regional Development is aware of the study being undertaken by Essendon Airport Ltd. Although it is not known how the department will seek to resolve current problems, they appear focused on applying a narrow, literal interpretation, of the Act.
The impact on Essendon Airport of building developments in the Melbourne CBD, though, is very different to those that could occur close to a major international airport. Essendon Airport has moderate traffic density, few aircraft fly the missed approach instrument procedure toward the Melbourne CBD and the development area is at least 9km from the airport. These factors suggest that changes to flight procedures could be undertaken to enable a higher PANS-OPS surface, or a higher crane penetration of the surface for a period longer than three months.
The lead time to gain approval to enter prescribed airspace by the Department of Infrastructure and Regional Development is quite lengthy. Currently it is estimated that 22 weeks will be required before an approval is gained.
Aviation legislation is limiting the height of high rise building developments within the Melbourne CBD. Initiatives are needed to change existing flight procedures for Essendon Airport so that the needs of building developments planned for the Melbourne CBD can be accommodated alongside those of aviation users.
Ian Thompson is a director of an aviation consultancy firm specialising in airport and air traffic management strategy and operations. He is representing developers on most of the high rise developments planned for the Melbourne CBD and was keynote speaker at the recent Elenberg Fraser PANS-OPS evening. Ian can be contacted at ithompson@thompsongcs.com.
