Automation Purpose

For large airports with high density incoming traffic during peak periods there was a need for a tool to assign flights to runways in an efficient sequence. This tool was to complement a capability in the en route center that assigns aircraft to a spot in the sequence of arriving flights and an assigned time of arrival over an inbound fix in the center’s airspace near the TRACON boundary. Once the aircraft made the transition to the TRACON, pFAST would provide the terminal controller with recommendations to make the most efficient use of airspace and runway resources by making a runway assignment and sequence number recommendation. pFAST was developed during the 1990s and fielded in 2001.

Automation Development Background

The pFAST tool was part of a larger suite of tools developed by NASA in the Center TRACON Automation System (CTAS) program. There was extensive simulation and prototyping activity including substantial human factors expertise. Prototypes of the tool were installed and used on a limited basis at two TRACONs to get user input. The initial fielding of the tool went to six sites.

Human Performance Requirements

There is no evidence that Human Performance requirements at the system or functional level were ever generated prior to the onset of full scale system development. Since there was general acknowledgement that the arrival stream of aircraft at a major airport such as Dallas-Fort Worth could be more efficient with the application of the proper algorithms, the system was introduced gradually as part of the evolution of technology. When the appropriate Technology Readiness Level was reached there was an expectation that the technology would be adopted and adapted for field use to enhance air traffic control efficiency. However, numerous inputs regarding detail design requirements for the display were made by human factors researchers.

pFAST Implementation

As part of the CTAS program there was a long history of laboratory development including simulations that progressed to high fidelity full mission capability. The technology made a partial transition to the field as part of risk reduction by being introduced on auxiliary displays for controllers to use initially for familiarization and informal evaluation. Later, the auxiliary displays were used for situation awareness at controller workstations to determine if the recommended runway assignments and sequence numbers were reasonable and valid as judged by local subject matter experts (SME). On-site researchers recorded SME comments and fed them back to programmers and algorithm engineers to enhance the quality and acceptability of the recommended solutions. Eventually, the tool was at least partially installed at six major TRACONs. At the request of the controller’s union, the tool implementation was halted.

Human factors researchers participated heavily in automation development. They were involved in the early stages of development, laboratory simulations, and field trials. Extensive use was made of SMEs, including union representatives, during all stages of development including simulations at various levels of fidelity, prototyping, and field trials in “shadow mode” where the tool was available only for situation awareness.

Tool development and implementation was halted in a contentious environment. It was clear that this was a case of premature introduction of automation in the air traffic control domain. While the en route center portion of the automation tool (Traffic Management Advisor) was generally well received and functioned as advertised, pFAST was not ready for use in the Terminal domain. The experience was viewed as negative.

Lessons Learned

The introduction of this automation was definitely not a success. A lessons learned report was generated, but not widely circulated. Key elements of the report cite the following concerns as contributors to the demise of this piece of air traffic control automation:

  • Confidence in the tool and ease of use are critical to controller acceptance
  • Any tool that is perceived to threaten job security will meet resistance
  • The prototype must be a success story: negative reports travel fast
  • Prototype development should identify the variables and conditions under which the tool will perform at other sites
  • Infrastructure necessary to support the use of a tool must be in place before deployment is begun
  • Controllers want certainty about when and how a new tool is to be used and by whom
  • The tool must have a clearly defined operations concept
  • Ensure that tools are not introduced to the field until they are at a sufficient maturity level to gain controller confidence (accurate, easy to use, and can show benefits)

Additional citations from the “lessons learned” report:

  • All 6 sites said runway allocations performed better than sequence numbers.
  • All 6 sites stated that runway allocations were not accurate all the time so the tool could not be used with confidence.
  • Four sites stated that the system could not react dynamically to variables such as holding, weather, go-arounds, and differences in controller abilities.
  • Four sites stated that the system worked well when traffic levels were low. As soon as traffic levels increased, the system could not perform as needed.
  • Two sites responded that procedures for situations such as satellite arrivals, no fix arrivals, and hsolding created problems for pFAST.
  • Two sites noted problems with pFAST because it took the system 20 minutes to make any configuration change.
  • All sites felt that implementation of pFAST could have been successful if the tool had provided accurate advisories and was used by all controllers
  • Responsibilities were never really determined. It was never decided if controllers could be held accountable for disregarding the advisories. Felt use of the tool must be mandatory to work. Workforce wanted management to determine that it should be mandatory and management didn’t want to make this decision

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