Air Traffic Control (ATC). Simply monitoring ATC frequencies (available on aeronautical charts) along the way is one way to keep abreast of changing weather conditions. For example, are other GA aircraft along your route requesting diversions? You can also request information on the present location of weather, which the controller will try to provide if workload permits. When you ask ATC for weather information, though, you need to be aware that radar – the controller’s primary tool – has limitations, and that operational considerations (e.g., use of settings that reduce the magnitude of precipitation returns) will affect what the controller can see on radar.
Datalink and Weather Avoidance Equipment. Radar and lightning detectors have been available in some GA aircraft for many years. These devices can contribute significantly to weather awareness in the cockpit. An increasing number of GA aircraft are now being equipped with weather datalink equipment, which uses satellites to transmit weather data such as METARs, TAFs, and NEXRAD radar to the cockpit, where it is often shown as an overlay on the multifunction display (MFD). Handheld devices with weather datalink capability are also a popular source of en route weather information.
There are several basic methods for transferring weather data from a weather data network provider to an aircraft:
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Request/Reply - In these systems, the pilot must decide what is needed and then request the specific information and coverage area. This request must then be sent from the aircraft to the satellite, from the satellite to the ground, processed by the ground system and transmitted back to the airplane. Transmission time can require as long as 10 or 15 minutes. Since weather can change very rapidly, this delay can significantly reduce utility of the data.
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Narrowcast - Some providers offer “narrowcast,” which automatically sends data directly to the aircraft according to the pilot’s pre-established preferences for products, update rate, resolution, coverage area, and other parameters.
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Broadcast - Broadcast systems continuously send available weather products to every user in the area through a satellite network and a system of interconnected ground stations. Satellite broadcast systems use high-power geosynchronous satellites to deliver large amounts of data in a very short time.
One of the most important, and critical, things to know about datalink is that regardless of the transmission method, it does not provide “real-time” information.
Process – (Honestly) Evaluating and Updating In-flight Conditions
Safe weather flying requires continuous evaluation of in-flight weather conditions.
Visual Updates. Seeing is believing – or so we are conditioned to think. Although you should certainly use your eyes during the flight to perceive the weather, you need to be aware that our prior visual experience largely determines our ability to “see” things. In the narrow runway illusion, for instance, the aircraft appears to be at a greater height over the runway because we have learned through previous experience what a typical runway should look like at a given altitude. The human brain prefers to adjust the apparent height of the aircraft rather than adjust the concept of what a runway should look like. 中國航空網 www.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：General Aviation Pilot’s Guide to Preflight Weather Planning, Weather Self-Briefings, and Weather Decision Making(12)
