Pre-Departure Clearance (PDC) at All 29 Continental U.S. Airports
On June 2, 1991, the Federal Aviation Administration (FAA) announced pre-departure clearance (PDC) operational at all 29 continental U.S. airports designated to receive the system, which used data link to speed departures and reduce voice radio frequency congestion.
At the time, the Air Traffic Control (ATC) clearance delivery process had the potential to be cumbersome, labor intensive in terms of controller voice-communications workload, and susceptible to human error. Particularly at facilities where upwards of 1,000 clearances were delivered daily. Also, frequency congestion with its consequent blocked and garbled communications had reached highly undesirable levels at many facilities.
PDC’s goal was to assist the Airport Traffic Control Tower (ATCT) clearance delivery position in relaying departure clearances to flight crews via data link. Data link delivery of clearances was to relieve much of the voice congestion on the ATCT clearance delivery frequency by eliminating voice clearance delivery to airlines participating in the program.
The PDC system was going to provide a solution to voice communications problems by using digital data communications instead of voice to relay departure clearances to aircrews. The PDC system could be used by tower personnel to compose clearances for data link delivery based upon information contained in the departure flight strips plus local operational instructions selectable from menu lists. After reviewing and appending any local information, the clearance would be transmitted from the PDC system to participating airline operations host computers. The airlines then would take responsibility to deliver the clearance directly to the appropriate aircraft utilizing Aircraft Communications Addressing and Reporting System (ACARS) data link or by delivery to departure gate printers. That eliminated the need for voice contact with the tower for clearance delivery to the flight crew. The PDC system would communicate directly with the airline operations computer to deliver clearances and would not affect in any way the FDIO system or flight strip printing in the tower cab.
