Wide-scale integration of unmanned aircraft systems into the National Airspace System through a fault tree analysis approach

The introduction of Title 14 of the code of Federal Regulations (14 CFR) Part 107 by the Federal Aviation Administration (FAA) has begun widespread integration of Unmanned Aircraft Systems (UAS) into the National Airspace System (NAS). Manned and unmanned aircraft will be occupying the same volumes of airspace for which the safety levels must be upheld. In order to preserve these levels of safety, a thorough scientific and systematic integration approach must be implemented. Until this point, aircraft certifications for operation in the NAS have been based upon the assumption that a pilot flies the aircraft from an in-fuselage cockpit. To maintain equivalency for unmanned aircraft operations, these implicit assumptions must be identified and translated to an unmanned aircraft context. A formal system safety assessment approach was initiated with a fault tree analysis to identify assumptions contingent on the pilot's presence inside the aircraft and areas of weakness in operational equivalency. A UAS fault tree framework is proposed as a translation from the accepted manned aircraft fault tree model. This framework is applicable to UAS of different classes, sizes, and operational modes. A database of international UAS accidents and incidents occurring 2001–2016 was used to categorize reported failure events and develop trend data identifying areas of concern for integration. This database was categorized by the UAS Fault Tree Framework Level 1 Subsystems and ICAO/CAST Aviation Occurrences. The most commonly occurring Aviation Occurrence was System/Component Failure (Non-Power plant). Trend data indicates areas of integration and reliability concern including the Aircraft/System and Flight Crew/Human Factors Level 1 Subsystem categories. The common ICAO/CAST Aviation Occurrences identified were different than those for fatal accidents in manned commercial aviation operations. High system reliability and formal aircraft system certification are needed to achieve equivalent levels of safety between manned and unmanned operations in the NAS. Additionally, pilot/crew training requirements for unmanned operations must be developed independently of existing manned aircraft training standards and must be evaluated to ensure effective systematic risk mitigation to the appropriate levels of safety.