MBSA in Aeronautics: A Way to Support Safety Activities

Abstract

MBSA models were used for the first time in the frame of an aeronautical certification in 2007 (for the Flight Control System of the Dassault Aviation Falcon 7X). 15 years later, MBSA method has been integrated into aeronautical standards which present guidelines for performing safety assessments of civil aircraft, systems, and equipment, the so-called SAE ARP4761A [1] and its EUROCAE complement, ED-135A.

The “A” version of SAE ARP4761 introduces the MBSA as a new method which achieves results that are equivalent to those obtained from the classical e.g., Fault Tree Analysis (FTA) safety analysis methods. It describes, in detail, a contiguous example of the safety assessment process for a function on a fictitious aircraft design, the “Decelerate wheels” function, performed by the “Wheel Braking System”. More particularly, it gives an example of how a MBSA method may be carried out to support the safety analysis during a Preliminary System Safety Assessment (PSSA).

The purpose of this article is to present and illustrate the way to support a PSSA process with a MBSA model, based on a representative Wheel Braking System model with various analyses (Functional Failure Set computation/DAL allocation, Minimal Cut Set computation/fail-safe principle, Failure Condition probability computation and Common Cause Failures identification/Independence principles). The MBSA model will be presented in a graphical tool dedicated to safety analyses and based on the formal language AltaRica [2].