Modelling distributed crewing in commercial aircraft with STAMP for a rapid decompression hazard

Abstract

Changes to crewing configurations in commercial airlines are likely as a means of reducing operating costs. To consider the safety implications for a distributed crewing configuration, system theoretic accident model and processes (STAMP) was applied to a rapid decompression hazard. High level control structures for current operations and distributed crewing are presented. The CONOPS generated by STAMP-STPA for distributed crewing, and design constraints associated with unsafe control actions (UCAs) are offered to progress in the route to certification for distributed crewing, and improve safety in current operations. Control loops between stakeholders were created using system-theoretic process analysis (STPA). The factors leading to the Helios 255 incident demonstrated the redundancy that a ground station could offer without the risk of hypoxia, during a decompression incident. STPA analysis also highlighted initial UCAs that could occur within the hypothetical distributed crewing configuration, prompting consideration of design constraints and new CONOPS for ground station design. Practitioner Summary: SPO in commercial aircraft is likely as a means to reduce costs. This paper makes a case for distributed crewing using STAMP-STPA. Comparing current operations with a distributed crewing configuration, the redundancy offered by a ground station is demonstrated. Design constraints and new CONOPs for distributed crewing, and current operations are proposed.

Keywords: SPO; STAMP; STPA; distributed crewing; rapid decompression; safety.