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32 other user leases. Users would execute a waiver with respect impending weather data that could affect their specific flight to the accuracy of the data provided, acknowledge such in- activity. formation as advisory, and recognize that they have respon- sibility for its application to their operating decisions. Threat and Risk Levels Decisions to more aggressively monitor lightning poten- United Airlines--ORD Only tials, stop ramp activity, and restart operations have been made Supports a single system provided all users can agree to the by all the airports and airlines surveyed. There is variability in risk levels and associated responses. the threat and risk levels, and there is also an element of judg- ment, especially with respect to restarting ramp activities. It is interesting to note that airport- and airline-defined threat United Parcel Service--Louisville Only and risk levels focus on the distances within which a lightning Supports the installation of lightning detection and warn- strike occurs and, at times, when the EFMs reach their alarm ing systems by the airport, but users must have flexibility in threshold limits. the interpretation and application of the data. Recognizes Ramp restart levels usually include a period of time during that each airport has a different operational environment, which no lightning events occur within a specified distance. distances between activity centers (cargo terminals versus air- The decision to restart ramp activity varies among the users line passenger terminal complexes), and that meteorological surveyed and highlights the subjectivity employed. Use of the conditions and lightning climatology also differ from airport "30-30 rule," which suggests that outdoor activities be limited to airport. or curtailed whenever a lightning strike is detected within 6 mi and within the past 30 min, does not appear to be employed in practice. Survey Observations The threat and risk levels are determined by consideration The preceding information yields several points of interest of the following two primary factors: for each category of investigation. Typical direction of thunderstorm movements and passage time, and Lightning Detection Equipment Input from labor unions representing the interests of those With the exception of one airport (DEN) and one airline operating on the ramp (UPS), all the airports and airlines contacted utilized a light- ning detection system complemented with one or two EFMs. Notification Process Those employing the Vaisala TWX1200 (or predecessor ver- sions) or other weather monitoring systems also obtain the The responses to questions about means by which airport, feed from the NLDN. airline, and other tenants are advised of pending, onsite, and passing lightning events reflected the greatest degree of vari- ability. Airports were focused on contacting their personnel Weather Data Support Systems by radio communication. This includes those personnel oper- Each of the airports has access to other sources of weather ating in open areas on the airport distant from terminal facil- data on which to base their decisions about stopping and ities, such as those maintaining airport grounds or operating restarting aircraft ramp activities. There is variability in the heavy and noisy machinery. Most airports also shared their use of such weather data sources that may be airport-owned lightning detection outputs on an advisory basis to the air- or readily obtained from tenants. For example, airports with lines and other tenants that have ramp access, such as fuelers, operations communications centers have television news caterers, and aircraft cleaning crews. Audible and visual alarms broadcasts continuously turned on and can thus monitor were used at some airports. Other airports have purposefully the Weather Channel and other programs when warranted. avoided the use of these means of notification and rely on "all- AM and FM radio broadcasts are also readily available at call" or direct telephone contacts. Other airports have installed these centers. In addition, links to weather radar displays, remote alarm units at airline operating areas in accordance with contract services, and regular telephone contact with airline lease agreements. One airport (ORD) has a policy of not advis- station operations personnel are employed. Airline station ing any tenant of lightning events because of liability concerns. managers may have some of these sources onsite and also Airlines act to notify their staff, and they accomplish this can contact their flight dispatch and operations centers for by one or more actions involving visual alarms (beacons at