Feasibility study of innovative regional turboprop: an overview of the European project IRON

This paper deals with the research activities performed by the Design of Aircraft and Flight technologies group from the University of Naples Federico II within the European funded project IRON (Innovative turbopROp configuratioN). The research project is addressed to the feasibility study of an innovative high-capacity turboprop which is supposed to be competitive with respect to regional jets on short/medium range. This paper wants to provide some design considerations that must be addressed to design a high capacity turboprop, and to illustrate the configuration assessment through a Multi-Disciplinary Analysis and Optimization process performed to design such an innovative platform. A three-lifting surface configuration has been identified as the most promising layout for such a regional aircraft. Moreover, this paper wants to focus on some criticalities and design challenges that have been faced into designing a three-lifting platform.

POTENTIALS OF SMALL AIRLINES IN SOUTH-EASTERN EUROPEAN COUNTRIES UNDER THE NEW ECONOMIC CIRCUMSTANCES

South-Eastern Europe holds a key geopolitical position and has a promising economy and aviation market. Small airlines operating in the region can succeed by taking advantage of the region’s characteristics and selecting appropriate strategies. This study’s objective is to examine the potentials of the region’s small airlines, focusing on their key strategic choices regarding destinations to serve, aircraft types to use, airports to operate from, and whether to operate independently or partner with larger carriers. In-depth interviews were conducted with key aviation experts from across the region, and secondary data were used to provide further insight. The study’s main findings show that small airlines may benefit from initially partnering with larger carriers, feeding their networks from secondary airports via regional jets and turboprops. This study adds to the relevant literature and may help managers from the region’s smaller and bigger airlines and airports identify new opportunities and develop sustainable strategies.

An Intercooled Recuperative Aero Engine for Regional Jets

Flying requires a high power density in the propulsion system. Currently only turbofan engines can provide the required power at a low system mass. To counter a potential negative impact of aircraft emissions on global climate, the agreement Flightpath 50, created by European research establishments and industries, has set the target to reduce overall CO2 emissions from the year 2000 to 2050 by 75 %. In contrast, the air traffic volume has been growing constantly since the 1980s and will be growing further. Hence the fuel burn of aero engines has to be reduced to reach the Flightpath 50 target. High-end component technology has nearly exhausted full potential in the improvement of conventional turbofan engines. Further significant progress can only be achieved by new engine concepts. The geared turbofan has proven the feasibility of this approach. The introduction of a gear allows the IPC and LPT to run at more suitable speeds with the consequence of a lower stage count compared to conventional turbofans. According to Pratt&Whitney this will reduce the fuel burn by ”15–16% versus today’s best engines” [1]. As a next step towards Flightpath 50 MTU Aero Engines AG envisioned the Intercooled Recuperative Aero Engine (IRA) for long-haul application. This concept increases the thermodynamic efficiency of the core engine by utilizing two heat exchangers: an intercooler reduces the work which is necessary for the compression. A recuperator transfers heat of the exhaust gas to the compressed gas entering the burner. In long-haul aircraft the increased engine mass due to the heat exchangers has a lower influence on the fuel burn. To broaden the research, this paper investigates the application of the IRA for regional jets. An extensive predesign parameter study was performed to find the optimal IRA configuration for regional jets. Not only has fuel consumption been taken into consideration, additionally the influence of the increased weight of the IRA has been included. In optimum, the fuel burn on a regional mission according to this study could be reduced in the order of 1–2%. However, the overall pressure ratio is much lower compared to modern turbofan engines, which leads to relatively low NOx emissions. It allows the introduction of Lean Premixed Prevaporized (LPP) burner technology, promising an additional significant reduction in NOx emissions compared to modern turbofan engines. Compared to a longhaul application the heat exchangers are not a scaled version but the result of a cycle optimization considering the available space. The paper also gives an outlook for an innovative three dimensional heat exchanger. The novel heat exchanger arrangement promises a better integration into the annulus at turbine exit and less aerodynamical pressure losses due to 3D-effects.