Abstract
The Doppler Lidar windshear alerting system at the Hong Kong International Airport (HKIA), the first of its kind in the world, has been in operation since 2006. This paper reports on an enhancement to the automatic windshear detection algorithm at HKIA, which aims at filtering out alerts associated with smoother headwind changes spread over longer distances along the aircraft glide path (called “gentle ramps”) which may nonetheless exceed the well-established alerting threshold. Real-time statistics are examined over a 46-month study period between March 2016 and December 2019, covering a total of 2,017,440 min and over 1500 quality-controlled pilot reports of windshear (PIREP). The “gentle ramp removal” (GRR) function is able to effectively cut down the alert duration over the 5 major runway corridors, inclusive of both landing and take-off, which together account for over 98% of the PIREP received at HKIA during the study period. In all 5 runway corridors this is achieved with a proportionately smaller decrease—even with no changes in 2 cases—in the hit rate, highlighting the efficiency of the GRR function. The difference in statistical behaviour across the runway corridors also echo literature findings about the differences in length scale of wind disturbances at different locations within HKIA. This study serves as a unique documentation of the state-of-the-art in operational Lidar windshear detection and can provide useful reference to airports and aviation meteorologists around the world.
Highlights
Low-level windshear, operationally defined as sustained headwind changes at an altitude of 500 m along the aircraft flight path [1,2], is a recognised aviation safety hazard
The above studies highlight the fact that, while advanced remote-sensing instruments such as the Doppler light detection and ranging (Lidar) are demonstrated to be effective in capturing the phenomena of low-level windshear, the underlying meteorological and geographical factors contributing to its occurrence may differ considerably across airports
We present the real-time performance of the “gentle ramp removal” (GRR) function, which is an enhancement to the Lidar windshear alerting algorithm operationally implemented at Hong Kong International Airport (HKIA) with aviation users’ support
Summary
Low-level windshear, operationally defined as sustained headwind changes at an altitude of 500 m (interchangeably with 1600 feet) along the aircraft flight path [1,2], is a recognised aviation safety hazard. During the landing or take-off phases of flight, the aircraft is in close proximity to the ground while having relatively low airspeed (e.g., as compared to the level phase of flight at cruising altitude). The above studies highlight the fact that, while advanced remote-sensing instruments such as the Doppler Lidar are demonstrated to be effective in capturing the phenomena of low-level windshear, the underlying meteorological and geographical factors contributing to its occurrence may differ considerably across airports. We present the real-time performance of the “gentle ramp removal” (GRR) function, which is an enhancement to the Lidar windshear alerting algorithm operationally implemented at HKIA with aviation users’ support.
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