1. Improving the TCAS System: A Work Domain Analysis Approach (TCAS: Traffic Alerts and Collision Avoidance System) Course: COG SCI 600 Instructor: Prof. Paul Thagard Presenter: Danny Ho Date: November 27, 2002

2. Perspective On July 1, 2002: Over Southern Germany, Bakshirian Airlines Tupolov 154 collided with DHL Cargo Boeing 757-200. Sequence of events: 1)Onboard safety system told Boeing to climb 2)Onboard safety system told Tupolov to descend 3)Air traffic control (ATC) told Tupolov to climb 4)Boeing climbed 5)Tupolov climbed 6)Midair collision occured The system FAILED! How?

3. High Level System View

4. Abstraction Hierarchy (Vicente, 1996) WHY HOW

5. Work Domain Analysis Cont’d –Decomposition Classify Abstraction hierarchy elements: system to component level Whole / Part relationships

6. TCAS II Version 7 (simplified decomposition) 2 Levels of Alerts - TA : traffic advisory - RA : resolution advisories - ‘climb’, ‘descend’, etc… Data Inputs - intruder range, altitude, bearing - ownship range, altitude, bearing Operational Parameters - protected volume varies with airspeed - threat based on time, not distance - no RA’s under 1000 ft AGL - system accounts for slow convergences - if intruder doesn’t react to their RA, ownship RA can be modified or reversed - pilot must respond to RA (U.S. regul’n) - pilot must inform ATC of RA maneuver - pilot must return to ATC course after RA (FAA, 2000)

7. Fast Forward >>> System Errors –Pilots often forget / slow to report RA maneuvers (FAA, 2000) ATC isn’t aware of such maneuvers, chain reaction… (DANGER!) –Communication breakdown Misunderstood directions, physical malfunctions –Pilots sometimes ignore RA’s (FAA, 2000) Potential Solutions –Automation can inform ATC of RA alerts issued by TCAS ATC and pilot(s) will be on the same page ATC can remind pilots to perform maneuvers –Automation can inform both pilots of intruder intentions and reactions Future Work –Research in automation, work domain analysis, cognitive work analysis –Define a framework for devising interfaces to improve upon TCASS II, Version 7 Q & A ?!?

8. References -Vicente, K., (1996), Improving dynamic decision making in complex systems through ecological interface design: A research overview. System Dynamics Review. (pp. 251-279) -Introduction to TCAS II Version 7, U.S. Department of Transportation, Federal Aviation Administration. November, 2000 (pp. 11)

9. Full Abstraction Hierarchy (condensed) Extra Slide