Safety Assessments for Avionics Modification Programmes

The Portuguese Air Force uses C-130 aircraft for a broad range of missions, including personnel and cargo transport, search and rescue, and firefighting. 

A Portuguese MRO (Maintenance, Repair, Overhaul) company was selected as the main contractor for the Avionics Modification Programme involving the Portuguese Air Force (PoAF) C-130 fleet. This consisted of the almost complete replacement of aircraft communication, navigation and flight control systems and instruments to upgrade the aircraft to the latest CNS/ATM requirements. To complete this task, however, they required the assistance of Critical Software safety experts to complete documentation and gap analysis, guaranteeing the airworthiness of the aircraft.

A safety team of Critical Software’s worked in coordination with the MRO, the assigned design organisation authority for the project, to ensure airworthiness requirements were recorded and that the system was being fully and correctly analysed via safety assessments. The objective was to find gaps related to missing advisory circulars and interfaces between multiple OEM equipment and respective safety assessments.

Critical developed the Preliminary System Safety Assessment (PSSA) and the System Safety Assessment (SSA), as well as an overall safety plan. We were responsible for safety management and communications support, provided in line with the National Military Aviation Authority standards, the OEM responsible for each integrated component.

Critical’s activities with the MRO were performed both on-site and off-site during the safety planning, PSSA, and SSA phases. Airworthiness requirements were validated, and important gaps identified, tracked, and closed together with the support from the MRO’s design and compliance verification teams. 

All safety documentation was integrated into a complete and understandable PSSA including fault tree analysis, failure modes, effect analysis and common cause analysis leading to the provision of new or missing airworthiness requirements covering not just the modification design but also aircrew training and manuals detailing operational and maintenance procedures.

• FAR CFR Part 21 and Part 25.1309
• DOD MIL-HDBK-516B
• SAE ARP 4754A and 4761
• FTA, MTBF, CCA, FMEA