IMPACT OF NEAR-COINCIDENT FAULTS ON DIGITAL FLIGHT CONTROL-SYSTEMS

The effects of near-coincident faults must be taken into account in de signing highly reliable digital flight control systems. In this paper closed-form solutions for permanent and transient near-coincident Faul t factors are derived, based on the behavioral decomposition/aggregati on technique and Markov version of the CARE III coverage model. Parame ters of the model are assumed to be exponentially distributed, The inf luence of fault detection rate, fault detectability, error production and propagation rates, error detectability, and transient fault/error transition rate on the near-coincident fault factors is discussed. Eve ntually, a homogeneous, continuous-time Markov chain is used for descr ibing a triple modular redundant (TMR) system. The near-coincident fau lt factors are employed for analyzing the effect of the interfering fa ults on reliability of the TMR computer System reliability and near-co incident fault unreliability are plotted as functions of mission time, fault detectability, and weight of permanent and transient fault/erro rs. The impact of near-coincident faults can be curbed by increasing f ault detectability, That impact is also lower when the percentage of t ransients is higher.