Validation and Verification of Future Integrated Safety- Critical Systems Operating under Off-Nominal Conditions

Abstract

Loss of control remains one of the largest contributors to aircraft fatal accidents worldwide. Aircraft loss-of-control accidents are highly complex in that they can result from numerous causal and contributing factors acting alone or (more often) in combination. Hence, there is no single intervention strategy to prevent these accidents and reducing them will require a holistic integrated intervention capability. Future onboard integrated system technologies developed for preventing loss of vehicle control accidents must be able to assure safe operation under the associated off-nominal conditions. The transition of these technologies into the commercial fleet will require their extensive validation and verification (V&V) and ultimate certification. The V&V of complex integrated systems poses major nontrivial technical challenges -particularly for safety-critical operation under highly offnominal conditions associated with aircraft loss-of-control events. This paper summarizes the V&V problem and presents a proposed process that could be applied to complex integrated safety-critical systems developed for preventing aircraft loss-of-control accidents. A summary of recent research accomplishments in this effort is also provided.

Online Safe Flight Envelope Prediction for Damaged Aircraft: A Database-driven Approach

“…The National Aeronautics and Space Administration's (NASA) Aviation Safety Program is developing technologies that address aircraft LOC prevention and recovery under a wide range of hazards and uncertain conditions. [3][4][5] Furthermore, some researchers are trying to quantify LOC events from flight data by defining metrics consist of five envelopes that are related to airplane flight dynamics, aerodynamics, structural integrity and flight control use. 6,7 Their results can help investigators decide whether or not the accident should be classified as a LOC, and identify the axis in which each event started as well as the chain of events that led to the lost controls, which will suggest valuable clues on how best to prevent future LOC events.…”

“…Alternatively, there are also various analytical methods to calculate the flight envelopes due to different definitions and numerical tools. 4,11,12 One important research in the area was the computation of attainable equilibrium/trim states and observing how control properties change with flight conditions and parameters via bifurcation analysis, 5, 13, 14 which has been developed to examine equilibrium structure of the aircraft at or near bifurcation points, indicating highly nonlinear upset conditions. Moreover, many nonlinear methods based on Lyapunov's stability theory have been proposed as a region of attraction (ROA) prediction tool.…”

Loss of Control Prevention and Recovery: Onboard Guidance, Control, and Systems Technologies

“…As indicated in Ref. 29, this requires a validation capability that enables comprehensive technology evaluation under varying levels of integration. It also requires evaluation under realistic LOC scenarios that enable an evaluation of the level of coverage related to current and future LOC risks.…”

“…29 The objective of the evaluation process is to expose system weaknesses and vulnerabilities, and to identify safe and unsafe operational conditions, regions, and boundaries. The evaluation results should include a clear delineation of the coverage of LOC hazards provided by the proposed integrated system technologies.…”

Future Integrated Systems Concept for Preventing Aircraft Loss-of-Control Accidents

“…Section IV summarizes the results of the paper and provides some concluding remarks. A detailed process for the validation and verification of the integrated systems technologies of this paper is presented in Reference [5].…”