The delivery of pre-departure clearances by the Clearance Delivery (CD) position in the airport traffic control tower cab is a tedious and repetitive task. The pilots called the tower for a clearance on the specified frequency. The CD controller then reads the clearance and checks the readback by the pilot. There are multiple opportunities for error during these lengthy voice communications, and frequency congestion was a problem at major airports. Since long distance flights may have many elements to the clearance, the process was time consuming. The repetitive nature of the task involving reading text from a flight progress strip was done by rote and was amenable to automation. The use of data communications to send the pre-departure clearance to the cockpit crew eliminated the need for tiresome voice communications and reduced the probability of human error for both the cockpit and tower crews. The CD controller’s task was reduced to assurance that there was an appropriate acknowledgement of clearance transmission with a reduction in frequency congestion. Attention could then be directed to off-nominal situations involving the CD position.
The system was developed in the late 1980s and early 1990s.
There is no evidence that HP requirements were generated or that there was any human factors/human performance program. The task was simple and the substitution of data communications for voice communications for this rote task was not complex. No decision-making was involved. The task involved few cognitive skills.
The implementation was a very positive experience. All indications are that user acceptance was high and the technology was seen as relieving a tedious burden. Ten years after introduction the technology was seen as essential at the high volume airports and the controllers saw the capability as a valuable tool.
This is a success story. While it is a simple story, it shows that technology can be introduced to the air traffic domain without undue drama and high user acceptance. Technology was used to relieve tower controllers of a routine, repetitive, time consuming task that was prone to error. The technology worked as advertised and provided the appropriate level of feedback to both the tower and cockpit crews that the required transfer of information was successful.
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