Plasma additive layer manufacture smoothing (PALMS) technology – An industrial prototype machine development and a comparative study on both additive manufactured and conventional machined AISI 316 stainless steel

Additive Layer Manufacturing (ALM) of metals is rapidly changing the landscape of industrial manufacturing. Its deployment is however still hindered by extremely rough native surfaces, and drastic difficulties in efficiently applying conventional finishing methods. This paper presents the PALMS process, derived from electrolytic plasma polishing, as a solution to this problem. The viability of the process on a scale compatible with commercial use is demonstrated with a prototype industrial implementation. PALMS was applied on AISI 316 stainless steel pieces produced either by ALM or by conventional machining (CM.) Surface states, microstructures and other properties were compared pre- and post-PALMS. Significant improvements in surface state were observed after a 10 min treatment, with a 5-fold reduction in roughness. ALM surfaces were not affected negatively by PALMS in any way measured, and showed slight improvements in hardness and pore density. Two PVD coatings (TiN and WCC) were finally applied Post-PALMS, to test the compatibility of the process with further industrially relevant surface treatments. PALMS enables good coating adhesion on ALM pieces, with improved friction and wear properties compared to their CM counterparts

Fleet Up-Gauging when Reducing Flight Frequency

Aircraft economies of scale do exist but are challenging to capitalize due to operational, technical and regulatory constraints. This study analyses the impact of a broad, systematic fleet up-gauging on COC (cash operating cost), fuel consumption, utilization and ATFM (air traffic flow management) delay for different frequency reduction scenarios. A fleet assignment model is applied to frequency-reduced, European high-density routes to generate COC-minimal fleet assignments. Due to the long-term nature of the required fleet adjustments the analysis is based on a timeframe of 20 years (2020 – 2040). Assuming traffic and ATFM delay levels as forecasted by EUROCONTROL, frequency reduction becomes increasingly beneficial from 2030 on. Particularly, in a scenario where up-gauging is limited to single-aisle aircraft COC-and fuel consumption benefits are the highest. In 2040 approximately EUR 74 million in COC, 12 million kg of fuel and 18 million minutes of ATFM delay could be avoided on the assessed routes. Up-gauging the fleet into the twin-aisle segment yields further ATFM delay reductions but increases COC and fuel consumption. The potential market entry of a NMA (new midsize airplane) could further increase the economic and ecologic attractiveness of up-gauging resulting from a frequency limit

Analysis of landing gear noise during approach

Airframe noise is becoming increasingly important during approach, even reaching higher noise levels than the engines in some cases. More people are affected due to low flight altitudes and fixed traffic routing associated with typical approaches. Formost air- craft types, the landing gear system is a dominant airframe noise source. However, this element can only be modeled in an approximate manner in wind tunnel experiments. In this research, flyovers of landing aircraft were recorded using a 32 microphone array. Fun ctional beamforming was applied to analyze the noise emissions from the landing gear system. lt was confirmed that for some aircraft types, such as the Airbus A320 and the Fokker 70, the nose landing gear is a dominant noise source du ring approach. The correlation between the noise levels generated by the landing gear and the aircraft velocity was found to be significant, explai ning about 70% of the varia bility found in the noise levels, which is in good agreement with all known theory. Moreover, the experimental resu lts for the Airbus A320 measurements were compared with those obtained using the DLR system noise prediction tool PANAM. Whereas the total aircraft noise levels were in good agreement. the measurements indicate a higher contribution from the nose landing gear noise compared to the predictions