Federal Aviation Administration officials will have their hands full trying to emulate in software what no less than 50 government and industry specialists attempt to accomplish on bad weather days at the FAA's Air Traffic Control System Command Centre (ATCSCC) in Herndon, Virginia. Such days are particularly common in late spring and summer months when thunderstorms are prevalent.
The morning of Wednesday 16 May started out with unfavourable winds at New York's Newark and LaGuardia airports, forcing a slowdown in arrivals due to runway configuration.
At the ATCSCC, government and major airline officials, during the first of their nine daily telephone calls, decided to put a ground delay program in place at the airports feeding the two New York facilities.
That meant aircraft destined for LaGuardia or Newark would hold for a predetermined time on the ground before take-off,set by a computer program that considers the arrival rate, then assigns take-off slot times based on an airline's percentage of the scheduled arrivals to the two airports. For example if Continental Airlines accounts for 74% of the scheduled arrivals into Newark, Continental will get 74% of the slots per hour, says Dan Smiley, facility manager for the ATCSCC.
Delays became more complicated when thunderstorms leading an eastward-moving cold front appeared in the Cleveland and Chicago area. The ATCSCC group reacted by setting up an airspace flow program in the area, meaning pilots could either deviate around the weather in the air or wait out the storms on the ground. In either case, the effect was to reduce the amount of traffic in that airspace. Along with saving fuel, aircraft on the ground were assigned a take-off slot, again by the computer program, based on their airline's schedule at the destination.
The number of aircraft deviating around the storm, however, led to the ATCSCC setting up another AFP in the vicinity of the North Carolina and South Carolina border, in part because of the amount of traffic deviating around the Cleveland and Chicago AFP. "Sometimes we create our own congestion problems," says Smiley.
Ultimately, as the front reached the east coast the group cancelled the Cleveland/Chicago AFP but had to put a ground stop in place at airports being pounded by a line of thunderstorms. With ground stops, aircraft destined for the closed airports are not allowed to take off and aircraft already in the air are either given holding patterns to wait out the storm or sent to alternative airports.
Source: Flight International
