Data-Linked Pilot Reply Time on Controller Workload and Communication in a Simulated Terminal Option

Civil Aerospace Medical Institute2001PDFResearch PaperPrinzo, O. V.Civil Aerospace Medical InstituteUnited States. Office of Aviation MedicineAir traffic controllersAir traffic controlWorkloadReaction timeTerminal operationsCommunication and controlCommunicationAir traffic control systemsAir traffic controllersAviation safetyCommercial aircraftCommunicationData linksPilot reply timeSimulationWorkloadDOT/FAA/AM-01/8Task AM-B-98-HRR-516This report describes an analysis of air traffic control communication and workload in a simulated terminal radar approachcontrol environment. The objective of this study was to investigate how pilot-to-controller data-link acknowledgment timemight affect controller-perceived workload and operational communication. Eight controllers provided air traffic services tosimulated arrival aircraft during a moderate-traffic density simulation in which voice radio and data link communicationswere available. The effect of a delay in downlinked pilot acknowledgment time to controller uplinked messages was theprimary variable of interest. Each controller completed the same scenario twice, with the order of presentationcounterbalanced. That is, for the first simulation, half the controllers received immediate responses to their data linkmessages while the other half received pilot acknowledgment time delayed by about 11 seconds. The primary finding was ageneral, albeit not statistically significant, tendency among controllers towards an increase in subjective workload overall andon individual dimensions of the NASA Task Load Index when the simulation environment supported mixed, rather thanimmediate pilot responses. The analysis performed on communication measures revealed that controller workload wasaffected by the communications capability onboard the aircraft but not ghost pilot response type (immediate, delayed).Transmissions to data link-equipped aircraft took longer to complete and contained longer pauses than transmissions tonon-data linked aircraft. The mode of communications selected by controllers also influenced workload but ghost pilotresponse type did not. When controllers used data link, their transmissions took nearly 2 seconds longer to complete thancomparable messages sent by voice. When compared with voice radio messages, controllers took longer to formulate andtransmit messages over a data link-communications system, but their messages were more accurate and contained fewermessage elements. This finding was replicated when messages with courtesies, salutations, and those involved in the initialcontact services were removed. Often, the data-link transmissions that contained longer pauses resulted from deliberateactions on the part of the controllers. Longer latencies did not result in a loss of efficiency but reflected innovations on thepart of the controllers to optimize performance. For example, by placing data-link messages in a pending status, controllerswould communicate with a non-data-link-equipped aircraft. When the data link-equipped aircraft arrived at a transitionpointalong their filed flight plan (generally approaching a hand-off point or transition altitude or fix), controllers uplinkedtheir already composed messages to those aircraft.119