The aviation industry represents an ever-expanding economy and the aircraft market forecast reveals an optimistic growth for the coming decades. New requirements and guidelines call for a more efficient, reliable, and environment friendly aircraft operations during both airborne and ground phases. Considering on-ground operations, the electric taxiing is one of the suggested solutions for reducing the emissions and the acoustic noise in the airport, and for lowering the fuel consumption and the flight costs. This paper provides an overview of the most important existing electric taxiing systems and also presents the basic concepts related to it. Finally, detailed comparison of the different systems is given with recommendations for the future research.

This paper summarizes the technical development of the low-emission GE-7FDL series locomotive diesel engine. The development focused on reducing the engine exhaust NOx emission significantly while reducing and curbing other visible and nonvisible emissions with minimal adverse impact on the engine fuel efficiency and minimal changes to the engine system and components. Concepts were analyzed, and were investigated using a single-cylinder 7FDL research engine. A low-emission 16-cylinder 7FDL engine and a GE locomotive prototype were built and tested for performance demonstration, function evaluation, and design optimization. The GE low-emission 7FDL engines and locomotives have been in production. The newly developed low-emission locomotive engine meets the EPA Tier-0 levels without fuel efficiency penalty. This was accomplished with minimal changes to the engine system and components. The desired engine reliability performance is retained. The engines are interchangeable with the preceding 7FDL baseline models, and the upgrade of the existing baseline engines to the low-emission version is facilitated.