AbstractHuman information processing consists of multiple and limited resources; some of them are shared while some are separate and non-interchangeable. High pilot mental workload (PMWL) - and the subsequent decline in performance - results from the imbalance between the mental resources available to perform the task and the amount of resources needed to perform it. When the pilot’s proficiency is evaluated, s/he should deliver an acceptable performance while being able to reserve enough mental capacity for the unexpected, additional resource demands. The task demands and cognitive stressors of air combat have potential to degrade pilot performance to an unacceptable level. Therefore, it is important to understand the amount of mental workload the pilots are experiencing and how much spare capacity they have available to cope with the possible additional resource demands. This thesis was aimed at understanding the relationship between PMWL and performance. The approach presented in this thesis was expected to support the development of reliable metrics for predicting the pilot performance under the stress of combat. In terms of practical applications, this thesis contributed to the development of the methodological principles that could help assuring the pilots’ ability to cope with the task demands higher than those experienced during training or proficiency checks.
Heart rate (HR) and heart rate variation (HRV) were used as indexes of PMWL. The selection was done for several reasons. HR and HRV measures were accepted by the pilots as they were non-intrusive and they appeared to be objective. In addition, the implementation requirements were by no means excessive. Considering the aims of this thesis, the low diagnosticity of HR/HRV was not an issue. Finally, HR and HRV proved to be sensitive measures of varying task demands – especially when measured together with the pilots’ awareness of the mission requirements. Simulated fighter missions were used to manipulate the pilots’ task demand and to measure their performance and HR/HR.
The thesis is constructed around three studies. In the first study, the subjects were required to fly instrument approaches in a high fidelity simulator under various levels of task demand. The task demand was manipulated by increasing the load on the subjects by reducing the range at which they commenced the approach. HR and the time domain components of HRV were used as measures of PMWL. The findings indicated that HR and HRV were sensitive to varying task demands. HR and HRV were able to distinguish the level of PMWL after which the subjects were no longer able to cope with the increasing task demands and their performance fell to a sub-standard level. The major finding of the first study was the HR/HRV’s ability to differentiate the sub-standard performance approaches from the high performance approaches.
In the second study, fighter pilots’ performance and PMWL were both measured during a real instrument flight rules proficiency check in an F/A-18 simulator. PMWL was measured using HR and HRV. Performance was rated using Finnish Air Force’s official rating scales. Results indicated that HR and HRV were able to differentiate varying task demands in situations where variations in performance were insignificant. It was concluded that during a proficiency check, PMWL should be measured together with the task performance measurement.
In the third study, fighter pilots’ HRV and performance were examined during instrument approaches and air combat. The subjects’ performance was rated by a weapons instructor. In addition, the subjects’ HRV was measured and used as an indicator of PMWL. During the instrument approaches, low performance was associated with high PMWL as expected. However, during the combat phases of the mission, low performance was associated with low PMWL. When the subject’s awareness of the mission requirements was studied, it was found that the combination of low performance and low PMWL was associated with the subjects’ low awareness of the mission requirements. The major finding was that unless the subjects’ awareness of the mission requirements is examined, the relationship between the mental workload and performance during a complex combat mission may be difficult to explain.
It is concluded that HR and HRV are sensitive measures of PMWL in a simulated fighter aviation environment. HR and HRV proved to be associated with the changes in task demands and pilots’ performance during simulated instrument approaches and air combat. However, the results of this thesis suggest that measuring just PMWL and performance is not sufficient – especially if the task of interest is complex and dynamic. To fully understand the pilot performance in such environment, the relationship between awareness of the mission requirements, workload and performance needs to be untangled. While this thesis provides encouraging results to understand this phenomena, further research is still needed before awareness of the situation requirements (or more broadly, situation awareness), performance and mental workload can be measured simultaneously, objectively and in real time.
|Date of Award||2016|
|Supervisor||Don Harris (Supervisor), Kai Virtanen (Supervisor) & Petteri Simola (Supervisor)|
- Human Factors