Steven Estes

The Workload Curve Subjective Mental Workload

Objective: In this paper I begin looking for evidence of a subjective workload curve. Background: Results from subjective mental workload assessments are often interpreted linearly. However, I hypothesized that ratings of subjective mental workload increase nonlinearly with unitary increases in working memory load. Method: Two studies were conducted. In the first, the participant provided ratings of the mental difficulty of a series of digit span recall tasks. In the second study, participants provided ratings of mental difficulty associated with recall of visual patterns. The results of the second study were then examined using a mathematical model of working memory. Results: An S curve, predicted a priori, was found in the results of both the digit span and visual pattern studies. A mathematical model showed a tight fit between workload ratings and levels of working memory activation. Conclusion: This effort provides good initial evidence for the existence of a workload curve. The results support further study in applied settings and other facets of workload (e.g., temporal workload). Application: Measures of subjective workload are used across a wide variety of domains and applications. These results bear on their interpretation, particularly as they relate to workload thresholds.

GDTI: A ground station display of traffic information for use in sense and avoid operations

This paper describes novel Unmanned Aircraft Systems (UAS) displays designed to alleviate conflicts between UAS and aircraft operating in the National Airspace System (NAS). Further, we present results from evaluating these display concepts via a low-fidelity, distributed evaluation environment focused on Ground-based Sense and Avoid humandisplay interactions. When pilots used the new situation awareness capabilities, they had consistently fewer events where an intruder breached the well-clear buffer (Beyond Well-Clear Buffer, or BWCB) (our definition of well-clear is defined later in this document), often with shorter duration. In contrast to a formal research laboratory environment, the distributed nature of our evaluation environment allowed rapid prototyping, quantitative analysis, and subjective feedback without the UAS pilots having to travel any farther than their nearest internet connection.

Wake turbulence avoidance automation: Evaluation of feasibility and impact

Wake turbulence encounters are a significant concern to pilots flying in the National Airspace System (NAS). The MITRE Corporations Center for Advanced Aviation System Development (CAASD) has worked with the Federal Aviation Administration (FAA) to increase efficiency and capacity in the NAS that will come with the FAAs Next Generation Air Transportation System (NextGen). By increasing efficiency and capacity, there will be a corresponding reduction in required separations that exist in operations today. As operations are optimized and these separations are reduced, it is important that there is not an increase in wake encounter rates that would tend to limit the acceptance of NextGen. NextGen technology, however, may enable the community to provide better tools to pilots and controllers for avoiding wake, thereby bounding the wake encounter rate at no more than todays operationally acceptable level. In this paper, arrival and departure procedures that take advantage of Automatic Dependent Surveillance-Broadcast (ADS-B) and Cockpit Display of Traffic Information (CDTI) technology in the cockpit are reviewed and their performance during a human-in-the-loop evaluation discussed.

Evaluation of Flight Deck Procedures Used in the Designation of Traffic for Tailored Collision Avoidance Logic

The Airborne Collision Avoidance System (ACAS XO) allows a pilot to select traffic for tailored collision avoidance advisories during simultaneous approaches to parallel runways. In the study reviewed in this paper, pilots evaluated ACAS XO procedures during a series of simulated approaches and departures. Half of the pilots were given the traffic to select by Air Traffic Control (ATC), while the remaining pilots had to determine the appropriate traffic to select on their own. Pilots who received the traffic from ATC selected targets more quickly and earlier in the approach. Pilots felt the process was easy and the workload was operationally acceptable. Analysis showed that earlier selection increased the utility of ACAS XO and was preferred by pilots as it allowed the crew to complete the procedure in a lower workload phase of flight.

Controller assigned airborne separation (CAAS) result of strategic pairwise study

A study of the controller-assigned airborne separation (CAAS) strategic crossing application has been completed by the MITRE Corporations Center for Advanced Aviation System Development (CAASD). The strategic CAAS procedure permits delegation of separation authority from the air traffic controller to the aircrew in specific situations, while assisted by ground-based automation for conflict detection and resolution, as well as data communication for clearance delivery. Nine former air traffic controllers worked various simulated air traffic scenarios both with and without strategic CAAS. Controller performance measures and subjective responses were collected and analyzed. Overall, results indicate that the concept of CAAS is promising. Controllers reported that it could be a useful procedure for reducing workload and therefore contribute to a more productive work environment. They also indicated that it is a reasonable step in the evolution of more sophisticated tools and procedures. Further research is proposed in four areas: (1) additional controller applications for CAAS, (2) pilot evaluations, (3) integrated pilot-controller experiments, and (4) analysis of benefits and costs.

Enhancing Airport Surface Markings to Support Pilot Awareness About Runway Location

Enhancements to airport surface markings were developed to facilitate pilot awareness of the runway location and to increase the conspicuity of the holding position markings, see Olmos, Andrews, and Estes (2003). The marking enhancements were evaluated in a simulation and two field studies. In a simulation study, general aviation (GA) pilots as well as transport category pilots performed taxi operations using a cockpit simulator. The simulated airport surface included enhanced surface markings and the distance at which pilots detected the runway environment was measured under various conditions. The results indicate that marking enhancements were associated with an earlier detection of the runway in some but not in all conditions. Specifically, transport category pilots detected simple taxiway-runway intersections with enhanced markings earlier than with current markings. No such perceptual advantage was found for GA pilots or at complex intersections. Most pilots, however, subjectively preferred the marking enhancements over the current marking standard. These positive evaluations of enhanced markings were confirmed by two field demonstrations where two sets of enhanced markings were implemented at two US airports. Pilots perceived the benefits of the marking enhancements to depend on pilot experience, familiarity with the airport, aircraft type, and knowledge about the marking enhancements. For certain airport situations, the enhanced markings in the hold-short environment of runways can be expected to aid pilot awareness about the runway location.

Cognitive Impacts of CAAS on Air Traffic Controllers and NAS -wide Controller Productivity

§Over the last several years, MITRE has been investigating the concept of delegated separation within the context of Controller -Assigned Airborne Separation (CAAS). CAAS is a procedure that allows t he air traffic controller to delegate responsibility for separation to the pilot. Two Human -in -the -Loop evaluations of CAAS have been completed, gathering subjective measures of workload, survey information, and data on the type and number of commands iss ued with and without CAAS. The most recent evaluation was designed to explore a new, strategic implementation of CAAS. This paper reports on the results of two components of the study, eye tracking and cognitive modeling, used to determine changes to co ntroller strategy and cognitive workload. The results suggest that, whereas a strategic usage of the CAAS procedure provides cognitive controller benefits, pure tactical usage of CAAS does not.