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Meeting	ACGS Committee Meeting 98 - Williamsburg - October 2006
Agenda Location	4 GENERAL COMMITTEE TECHNICAL SESSION 4.1 Government Agencies Summary Reports 4.1.4 NASA 4.1.4.3 Langley Research Center
Title	Langley Research Center
Presenter	Chris Belcastro
Available Downloads*	presentation
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Abstract	The long-term mission of the Integrated Resilient Aircraft Control (IRAC) Project is the development of technologies to reduce aircraft loss of control accidents and to ensure safe flight under adverse, upset, and hazard conditions in the current and next-generation air transportation system. Loss of control is a leading and complex aircraft accident category, and over the period 1987-2004 resulted in 2,524 fatalities (approximately 26%) across the worldwide commercial jet fleet. Numerous causal and contributing factors can be cited for loss-of-control accidents, with multiple factors often combining to result in loss of control. Causal and contributing factors can be categorized as adverse conditions, vehicle upset conditions and external hazards. Numerous overarching technical challenges must be overcome in developing advanced control technologies that will be effective in improving aviation safety and in supporting safe operation within the next generation air transportation system – particularly under abnormal conditions. A long-term research framework has been developed for IRAC to systematically solve these challenges with progress scoped over 5-year research phases. Technologies for reducing aircraft loss-of-control accidents during the first five years will focus on the following problems: icing effects, damage effects, and vehicle upset. In order to solve these problems, icing and damage conditions must be detected, characterized, and mitigated in flight, and vehicle upset conditions must either be prevented or recovered. The following three areas are seen as the key technical challenges to solving these problems and will form the basis of technology deliverables during the first five years of the IRAC project. • Modeling and Simulation: Aircraft prevention and recovery from loss-of-control requires the ability to identify and assess, via physics-based modeling and simulation, loss-of-control precursors, causal or contributing factors, and their impact on aircraft safety of flight and recoverability. These factors lead to coupled vehicle dynamics effects, and must therefore be characterized using an integrated multidisciplinary modeling approach that includes aerodynamics, vehicle dynamics, structures, and propulsion. Current modeling and simulation methods enable some coupling between aerodynamics and propulsion, and between aerodynamics and aeroelastic structural effects. However, current methods do not include the capability for high-fidelity modeling and simulation of coupled, massively separated flows resulting from upsets, damage, or icing conditions, which poses enormous technical challenges in the disciplines of aerodynamics, vehicle dynamics, structures, and propulsion. Towards solving this technical challenge, we will focus on technologies for the integrated multidisciplinary modeling of aerodynamics, vehicle dynamics, structures, and propulsion in order to characterize abnormal conditions and their impact on aircraft dynamic response. • Vehicle State Assessment and Resilient Control: Recovery from loss of control requires advanced multidisciplinary, multi-objective control methods to detect, identify, and mitigate a variety of dissimilar causal and contributing factors onboard and in real time. Since loss of control under these conditions can occur very quickly and the time available for recovery is limited, the vehicle state must be continually assessed and all available control power utilized to maintain or regain control, in order to ensure safe flight within the current and future air transportation system. Current adaptive and reconfigurable control methods are not multidisciplinary since they often address only the vehicle dynamics. The lack of multi-objective stability, control, and trajectory management functions in the current adaptive control methods render them ineffective in dealing with abnormal conditions whereby dissimilar and coupled effects exist. Our research will focus on the development of coupled adaptive flight, engine, and airframe control technologies that are integrated with trajectory, thrust, and loads management technologies. Control autonomy requirements for effective trajectory management under abnormal conditions will also be considered in the presence of vehicle dynamics constraints including propulsion and airframe effects. • Verification and Validation: The transition of simulation models and resilient control methods for onboard control under abnormal conditions requires new validation and software verification methods that include predictive capability assessment techniques. Rigorous methods for adaptive software verification and system validation must be developed to ensure that control system software failures will not occur, to ensure the control system functions as required, to eliminate unintended functionality, and to demonstrate that certification requirements can be defined and satisfied. Current methods focus on models and systems designed for normal operation under nominal conditions. Validation methods to be developed include analysis methods for adaptive control systems, simulation based methods for guided Monte Carlo evaluations, and experimental test methods for ground and flight-testing under abnormal conditions. Methods and tools for probabilistic uncertainty characterizations and risk analysis will also be developed for experimental risk mitigation and as a prerequisite for establishing predictive capability assessment methods. Research into software verification and safety assurance methods for safety-critical adaptive systems will also be initiated.