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Constraints on HKIA Dual-runway Operation and Airspace Issue

Mr Norman Lo, Director-General of Civil Aviation
April 2, 2015

Recently some members of the public have challenged the planning of the three-runway system (3RS) at the Hong Kong International Airport (HKIA) on two issues: (1) whether the current capacity of two-runway system (2RS) can be expanded (and hence, the third runway would be unnecessary); and (2) whether the airspace issue can be resolved.

The maximum capacity of the existing two runways

Various studies had been conducted in the past to assess the capacity of the 2RS. The latest study was the Airspace and Runway Capacity Study commissioned by the Airport Authority of Hong Kong (AAHK) and carried out by National Air Traffic Services (NATS) in 2008, which was based on the latest air traffic control technology and international standards. According to this study, in full compliance with the safety standards/requirements of the International Civil Aviation Organization (ICAO), the maximum practical capacity that can be achieved with the existing 2RS would be 68 movements per hour.

Can the maximum capacity of the existing 2RS be further increased?

The capacity of the existing 2RS is constrained by two factors in which the ICAO has strict requirements and standards: (1) the need for spacing between aircraft due to the spiral air turbulence generated by operating aircraft (known as wake turbulence); and (2) the surrounding terrain near the runway.

Wake turbulence

Strong wake turbulence can cause the following aircraft to lose balance, thus affect flight safety. Therefore, the ICAO requires that a minimum spacing be maintained between aircraft during takeoff and landing. The heavier the aircraft, the stronger the wake turbulence and the larger the spacing would be required. Consequently, the capacity of a runway is limited.

Terrain constraints

The report of New Airport Master Plan (NAMP) in 1992 from the former Provisional Airport Authority, pointed out that, a pair of parallel runways under different modes of operation could in theory achieve different capacity ranging from 52 to 86 movements per hour (See table below). However, the NAMP report made clear that due to the mountains on the nearby Lantau Island, in order to achieve higher runway capacity, it would not be possible to operate in compliance to relevant ICAO standards on flight procedure, hence such operation was neither safe nor practicable.

Mode of Operation Practical Hourly Capacity Estimate
(a) Single-runway system 43 movements
(b) Dual-runway system with Segregated Operation (i.e. one runway used exclusively for approaches and the other exclusively for departures) 52 movements
(c) Dual-runway system in Mixed Operation
(i) Dependent Mixed Modes: departures and approaches on one runway must take into consideration an aircraft landing or departing on the parallel runway. The possible modes are as follow:
     (a) Dependent Approaches and Departures 69 movements
     (b) Independent Approaches and Dependent Departures; and 71 movements
     (c) Dependent Approaches and Independent Departures 79 movements
(ii) Independent Mixed Mode: Operation on one runway can take place completely separately and without interference from the parallel runway, as if the two runways were two different airports. 86 movements

The consultant commissioned by the Civil Aviation Department (CAD) in 1994 also pointed out that, due to the constraints from surrounding terrain, the maximum capacity of the 2RS could only be about 63 movements per hour. As previously mentioned, in 2008 NATS had conducted a thorough review of runway capacity of HKIA and confirmed that after implementing some 40 improvement recommendations, in full compliance to ICAO safety standards/requirements, the maximum runway capacity of 2RS could be increased to 68 movements per hour.

Some comments suggested that if the peak of Tai Yam Teng (610 feet) and Fa Peng Teng (810 feet) which are located at the North East of Lantau were removed, the runway capacity of the 2RS could be further increased. These comments claimed that removal of Tai Yam Teng and Fa Peng Teng were suggested in the 1992 NAMP report. In fact, the suggestion in the NAMP report was made in connection with possible options to enhance the climb gradient of contingency departure procedures for departing aircraft on engine out during initial climb (i.e. to reduce restriction on the aircraft engine out climb performance). In order to attain the theoretical maximum runway capacity outlined in the NAMP report, i.e. 86 movements per hour, and conforming to the safety standards/requirements of the ICAO, most of the high peaks on Lantau Island, including Lantau Peak, Sunset Peak and other high mountains, would have to be levelled. Major infrastructure and landmarks like Ngong Ping Cable Car, Big Buddha and Po Lin Monastery would also be affected, not to mention that most of these areas fall within the boundaries of the Lantau Country Parks. . Therefore, the proposed removal of high peaks is neither practical nor feasible.

The "Air wall" issue

There have also been concerns on the constraints imposed by the so-called "air wall". In fact this is not an appropriate term as in reality there is no "wall"-type segregation between different airspaces. To ensure that aircraft in adjacent airspaces can operate concurrently in a safe and efficient manner, every aircraft must reach a certain altitude and geographic location before an air traffic control (ATC) unit may hand over control of that aircraft to another ATC unit. This is to ensure that aircraft in adjacent airspace flying in opposite directions can fly at various altitudes and prevent collisions. This air traffic management arrangement of "Transfer of control point" aims to safeguard flight safety, and is commonly applied at busy airports all over the world, including those in London and New York.

Airspace issue

The Tripartite Working Group (TWG), set up by the Civil Aviation Administration of China (CAAC), CAD of Hong Kong and the Civil Aviation Authority of Macao (CAAM), drew up the "Pearl River Delta Region Air Traffic Management Planning and Implementation Plan (2007 Plan)" after three years of work and more than 10 rounds of meetings at various working levels. The maximum capacity of 102 movements per hour under the 3RS operation at HKIA as proposed by AAHK is based on this 2007 Plan.

2007 Plan

The 2007 Plan has clear objectives and contents. As per the press release issued by the CAAC on 15 February 2007, the Plan "aiming at strengthening the synergy of collaborative operations between all three parties, taken into consideration of terminal airspace structure, ATC operation standards and ATC operation procedures, defined three phases of the planning and development of Pearl River Delta (PRD) air traffic management. With the use of state-of-the-art computer-simulation and evaluation techniques, technical experts from the three parties conducted analysis and concluded that the Plan could generally satisfy the development needs of aviation industry in the PRD region in 2020".

At the TWG meeting held on 18 June 2012, all parties expressed their support for HKIA adopting the 3RS as the future development option, and to the CAD using such a proposal for air traffic management and planning purposes. The Central Government has always supported Hong Kong in cementing its position as an international aviation hub and developing the 3RS. We strongly believe that the Mainland, Hong Kong and Macau will be able to implement, in accordance with the 2007 Plan, all enhancement and collaborative measures conducive to the development of the five major airports in the PRD region.