Preliminary safety assessment of circular variable nacelle inlet concepts for aero engines in civil aviation

Preliminary safety Assessment on System Design Level for Broadband Acoustic Liner Concepts for Aviation

“…This process is continued until only basic causes exist, which are defined as external influences, unchangeable operating conditions or influences of surrounding systems and structures. Depending on the TRL of the development process, a qualitative or quantitative FTA can be carried out [07], [10].…”

“…Delamination and core failure can lead to loss of integrity of the FHR-Liner and small to large parts of the sandwich structure can be sucked into the cold gas path. Depending on the position of the affected liner structure, the aerodynamic flow contour (Intake, BPD) or even direct subsystems (Fan, TRU) can be impaired and damaged [10]. In case of the PR-Liner, a top layer failure can be equated with damage to the flexible foil, which covered the entire upper liner surface.…”

Evaluation of Variable Pitot Inlet Concepts for Transonic and Supersonic Civil Aviation

“…Leakage of any fluid in proximity to electrical equipment of the adjustment system can cause damage and hazards, which are avoided by design adaptations, e.g. over-pressure breakout panels, ventilation, drainage and heat protection for the adjusting system [8], [9]. Due to the physical adjustment of the inlet geometry, a flexible design of wiring and pipe installation to minimise stresses, as well as a minimum clearance between those components to avoid friction and collision are required [9].…”

“…probes, acoustic treatment or a potential adjustment system, and in the vicinity of the inlet. These interactions between components within the inlet zones, as well as zones in the vicinity are investigated best by conduction of a Zonal Safety Analysis (ZSA) [9].…”

“…Hence, within the scope of a feasibility study for variable inlet concepts, the methodological development process is combined with the safety assessment process in aviation according to Aerospace Recommended Practices ARP 4754A [5]. Among others, this process comprises  the identification of ideal geometries for variable inlets concerning drag and flow uniformity for flight speeds up to Mach 1.6 and their potential range benefit [6],  the development of inlet concept groups that adjust the geometry by rigid segment repositioning, by elastic surface deformation or by boundary layer control [7],  the application of the safety methods Functional Hazard Assessment (FHA), Fault Tree Analysis (FTA) and Common Cause Analysis (CCA) [8], [9],  the integration of ice detection and protection systems for variable inlet concepts [10]  as well as subsequent design adaptations. This paper describes the selection of the ideal group of variable inlet concepts by utilising results of aerodynamic investigations, system safety analyses and integration studies.…”