Human Factors Issues of Tcas: a Simulation-Based Study

Since its introduction in the 90’s, TCAS II, presented as a straightforward and very reliable technological tool, has significantly reduced the risk of collision. Paradoxically, the introduction of this system has been accompanied with numerous incidents and one major accident in 2002, mainly due to unclear rules, poor air-ground cooperation and poor human decision. In order to investigate these potential human factors issues, a part-task air-ground simulation was conducted: 10 pilots and 10 controllers were involved in the simulations of 4 scenarios containing TCAS occurrences. Data collected included video camera recordings for behavioral analysis, Heart Rate (HR) for stress evaluation, questionnaires and debriefings for perceived risk levels and situational awareness assessment. The observations and errors were analyzed through the CREAM methodology. The debriefings were led through a self-confrontation technique, together with pilots and controllers. Results show that the simulations of TCAS situations were able to produce a significant physiological stress response with significant increase of HR when a resolution happens. Questionnaires and debriefings show that, in most of the observed cases, aircrew, and controllers are not sharing the same mental picture of the involved traffic and the risk of collision. This raises important issues in terms of cooperation between controllers and aircrews in such demanding occurrences. This should allow identifying risky situations and the related generic causes. The results will be discussed, aiming at a potential improvement of the system, in terms of Human Machine Interface, training and consistency of procedures

Simultaneous observations of Polar Stratospheric Clouds and HNO3 over Scandinavia in January, 1992

Simultaneous observations of Polar Stratospheric Cloud (PSC) aerosol extinction and HNO3 mixing ratios over Scandinavia are examined for January 9-10, 1992. Data measured by the Microwave Limb Sounder (MLS), Cryogenic Limb Array Etalon Spectrometer (CLAES), and Improved Stratospheric and Mesospheric Sounder (ISAMS) experiments on the Upper Atmosphere Research Satellite (UARS) are examined at locations adjacent to parcel trajectory positions. Regression coefficients, obtained from Mie calculations, are used to transform aerosol extinctions into aerosol volume densities. Graphs of volume density versus temperature, and importantly, HNO3 mixing ratio versus temperature, show volume increases and simultaneous loss of HNO3 as temperatures decrease. The data is consistent with initial PSC growth processes which transform sulfate droplets into ternary droplets or nitric acid dihydrate (NAD) particles