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Wind Shear |
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| (1) What is low level windshear and microburst? |
| (1) What is low level windshear and microburst? |
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Windshear is the fierce change in wind speed and direction of two points in the atmosphere. Low level windshear means the sudden change of wind direction or wind speed below 1600 ft (500 m) which is the main factor that affects flight safety of the aircrafts. Microburst is the strong low level windshear in a small horizontal range which lasts only 0.1 to 0.25 hour. |
| (2) What kind of windshear information could we get in the Taipei Flight Information Region? |
| (2) What kind of windshear information could we get in the Taipei Flight Information Region? |
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1. Windshear alerts issued through ATIS: The broadcasts issued through ATIS include the windshear existing near the runway within METAR and SPECI reports to remind the pilots.
2. The windshear, low level windshear and microburst alerts issued by the Air Traffic Controllers (ATC):
(1) After acknowledging pilot reports about windshear, ATCs would transmit the information to other pilots until there's no pilot reports about windshear.
(2) If there are LLWAS installed in the airports (like Sungshan and Taoyuan airports), ATCs would transmit the information about the low level windshear and the microbursts to the pilots according to the alerts from the LLWAS. |
| (3) What kind of low level windshear detection facilities are installed in Sungshan and Taoyuan airports? |
| (3) What kind of low level windshear detection facilities are installed in Sungshan and Taoyuan airports? |
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1. The Low-level Windshear alert system (LLWAS) installed at Sungshan and Taoyuan airports are the latest LLWAS developed by the National Center of the Atmospheric Research (NCAR) for Federal Aviation Administration (FAA). The LLWAS system are not only installed at over 100 airports around US, but they are also installed in Korea, Singapore, SAUDI ARABIA, Spain, Italy, Kuwait. Mainland China and Brunei also plan to install LLWAS at their airports.
2. There are two kinds of alerts of the LLWAS installed at Sungshan and Taoyuan airports:
(1) Wind Shear Alert (WSA): the decrease of wind speed between 15 kts and 29 kts or the increase of wind speed over 15 kts. For example, “28-D WSA 25K+ 2MD” means windshear alert at runway 28 departure with 25 kts of wind speed gaining at 2 miles departure area.
(2) Microburst Alert (MBA): the decrease of the wind speed over 30 knots. For example, “10-A MBA 40K- 3MF” means microburst alert at runway 10 arrival area with 40 kts lost of wind speed at 3 miles final approach area. |
| (4) What is the accuracy of the LLWAS installed in Sungshan and Taoyuan airports? Why are the pilots not aware of the low level windshear while the alerts are issued? |
| (4) What is the accuracy of the LLWAS installed in Sungshan and Taoyuan airports? Why are the pilots not aware of the low level windshear while the alerts are issued? |
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1. According to the data offered by NCAR, the accuracy of the LLWAS installed at Sungshan and Taoyuan airports could reach 90% under regular operation.
2. The area influenced by low level windshear or microburst is possibly small or randomly appeared within a short period. Therefore, the pilots flying through the same area could have different experience about the low level windshear and microburst. |
| (5) Is the microburst accompanied with thunderstorm weather? Why is the MBA issued at Sungshan and Taoyuan airports even if there are either no thunder or no rain after typhoon passing by? |
| (5) Is the microburst accompanied with thunderstorm weather? Why is the MBA issued at Sungshan and Taoyuan airports even if there are either no thunder or no rain after typhoon passing by? |
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Although typical microburst accompanies with thunderstorm, it's not necessarily the case. When the typhoon strikes, the airflow around the airport is affected by the circulation of the typhoon which is windy with changeable wind directions that induces strong low level windshear which threatens the aircrafts. For flight safety, it's possible and reasonable to issue MBA from the LLWAS continuously. |
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