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Japan Aerospace Exploration Agency

Weather information technology

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Vortex turbulence that forms behind a passenger aircraft is referred to as wake turbulence. Consecutive take-offs and landings require an interval, or separation, during which wake turbulence by a preceding aircraft fades out. That interval is about 2 minutes in the case of a large aircraft. Evidently, the current practices of operations will be insufficient to cope with the expected increases in airplane passenger traffic.

In reality, it is not always necessary to wait for as long as 2 minutes because wake turbulence moves and recedes as a result of atmospheric phenomena such as wind. Weather information technology predicts changes in wake turbulence behavior according to phenomena such as wind, and computes a safe interval according to weather conditions, which is usually a shorter interval than the rigid system used today.

Hills and valleys or buildings around an airport may alter air flow and thereby cause wind shear (unexpected wind change) or turbulence. Such disturbance of the air (low-level turbulence) affects the operation of aircraft flying at low altitudes so much that a flight might be cancelled because of aborted landing. Instructions on the danger of low-level turbulence in advance allow a pilot to judge the timing of the optimal approach.

These technologies offer promising solutions for expanding airport capacity and improving the in-service rate.

Conceptual view of system operation to reduce aircraft separation with wake turbulence prediction

Low-level Turbulence Advisory System (LOTAS)

Using the latest weather remote sensors that are less expensive than conventional components, JAXA has been developing the LOw-level Turbulence Advisory System (LOTAS), a system that provides real-time turbulence information in the landing approach path, together with prediction data for 10 minutes later, to support airline pilots and dispatchers.
Pilots can receive the turbulence information via the Aircraft Communications Addressing and Reporting System (ACARS), a text-based digital datalink system that is installed in aircraft cockpits.

ACARS Text Information

The turbulence information at each altitude level and the prediction for 10 minutes later supports the airline dispatchers when giving landing instructions to pilots.

Radar Echo Display

Wind Information

By making it possible to prepare for local wind disturbances including low-level windshear, such turbulence information assists in making landing timing decisions to reduce wasteful go-arounds, and thus enables safer and more efficient operations.

In addition, JAXA and the Japan Meteorological Agency (JMA) jointly developed the Airport Low-level Wind InformatioN (ALWIN) system, a turbulence information system based on LOTAS technologies but which uses the existing weather Doppler LIDAR* systems already installed at some airports, instead of using LOTAS weather remote sensors.Developed ALWIN was put into practical use in April 2017.

* Airport weather Doppler LIDAR: A device that measures the wind at low altitudes under non-precipitation conditions by using laser beams to detect the movement of aerosols (fine particles) in the atmosphere.

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