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User Needs
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The best starting point
for developing an operational concept is to review the issues and needs raised by the
future users of the AOAWS. User needs were developed during meetings held in Taipei in
1996, 1997 and 1999. Organizations represented in the meetings included the Taiwan Civil Aeronautics Administration (CAA), Far
Eastern Transport (FAT), China Airlines, EVA Air, Air Force Meteorological Center, Central
Weather Bureau (CWB), TransAsia, Hwa Hsin Airlines, Formosa Airlines and U-Land Airlines.
Chun-Ming Jou (So-So), visiting
engineer from the CAA in Taipei, is working on the MDS display at the AOAWS
lab in Boulder. |
Major issues and user needs
considered in the development of AOAWS concepts:
Convective
windshear (including microburst) detection in the terminal areas has higher priority than
other advanced aviation weather products.
Terrain-induced
windshear and turbulence in the terminal area has the second highest priority.
Thunderstorm
hazards in the terminal area are important followed by thunderstorm hazards in the
domestic enroute region and lastly in the FIR region. Thunderstorm hazards include
windshear, turbulence, lightning, and to a lesser extent, icing.
Knowledge of
airport surface winds and ceiling and visibility are necessary for safe operations. Better
forecasts of those conditions are highly desired.
For flight
planning, accurate information (current and forecast) of winds and temperature aloft are
required.
The users
agreed that better weather detection and forecasts accuracy for all aviation weather
information is desired.
With this in
mind, a number of considerations for AOAWS development were reviewed and accepted. AOAWS
design considerations include:
The
windshear systems - Low-Level Windshear Alert Systems (LLWAS) and the Windshear Processor
(WSP) - should have a high Probability of Detection (POD) and low False Alarm Rate (FAR).
If more than
one sensing system is used for hazards detection, the resulting alert information should
be based on an integrated approach.
Terminal
alert information should be concise to keep the controller workload low.
The AOAWS
should use standard terminology for describing weather phenomena. For example, products
such as flight categories should use standard definitions for IFR, VFR, etc., and standard
terms should be used for turbulence and windshear. Event intensities should also be given
using standard terminology.
Alert
conditions should be reserved for operationally significant (safety critical) events.
Crosswind
shear may be an operational problem at some airports, particularly at CKS and Kaohsiung.
Vertical
windshear is thought to be a common occurrence at CKS. More research is needed to
understand this phenomenon and determine whether it is an aviation hazard.
The windshear
alert generation strategy should be consistent with FAA and other established systems. For
example:
Alerts
should be provided, where possible, out to 3 nm on approach and departure.
Alert update
rate should be approximately 60 seconds or faster.
The alert
corridor around the runways should be 1/2 nautical mile wide on either side of the
centerline to account for windshear event movement.
Windshear
alerts should be provided as gains or losses in wind speed (knots).
The minimum
windshear alert threshold should be 15 knots.
The minimum
microburst threshold should be 30 knots (windspeed loss).
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Advanced Operational Aviation
Weather System (AOAWS) in Taiwan 
