Design and Optimization of a Large Turboprop Aircraft

Abstract

This paper proposes a feasibility study concerning a large turboprop aircraft to be used as a lower environmental impact solution to current regional jets operated on short/medium hauls. An overview of this market scenario highlights that this segment is evenly shared between regional turboprop and jet aircraft. Although regional jets ensure a large operative flexibility, they are usually not optimized for short missions with a negative effect on block fuel and environmental impact. Conversely, turboprops represent a greener solution but with reduced passenger capacity and speed. Those aspects highlight a slot for a new turboprop platform coupling higher seat capacity, cruise speed and design range with a reduced fuel consumption. This platform should operate on those ranges where neither jet aircraft nor existing turboprops are optimized. This work compares three different solutions: a high-wing layout with under-wing engines installation and both two- and three-lifting-surface configurations with low-wing and tail tips-mounted engines. For each concept, a multi-disciplinary optimization was performed targeting the minimum block fuel on a 1600 NM mission. Optimum solutions were compared with both a regional jet such as the Airbus A220-300 operated on 1600 NM and with a jet aircraft specifically designed for this range.

Hybridization and Mission Analysis of a regional turboprop

“…The design process proposed in literature for hybrid-electric aircraft is composed by different steps starting from point performance [6]. However, when the geometry and the structural masses are frozen, a different approach can be considered stepping in the design process from the simulation-based mission analysis, changing some design parameters of interest while remaining compliant with performance requirements [7,8]. At this point, since the only mass changing depends on the propulsive system, the first step is the definition of the frozen masses related to structural weights.…”

“…The last hypothesis is about the maximum power delivered to the tip-mounted propellers. Since the wing structure has been fixed, the tipmounted mass should be limited to avoid a lowering of the flutter speed [6,7]. The value of shaft power ratio fixed for this reason is 0.3.…”

Design Evolution and Wind Tunnel Tests of a Three-Lifting Surface Regional Transport Aircraft

“…Apparently, the complicated interactions among the wakes of the lifting surfaces was not well predicted by the MDAO process of Refs. [8,11]. Thus, from the results of the first test campaign, the canard and the tailplane group were re-designed and a second test campaign on the updated scaled model, shown in Figure 2, was performed.…”

“…So far as it concerns this research, a fundamental role concerns the feasibility study conducted by the authors in [11]. In this work, the authors investigated three possible high-capacity turboprop configurations conceived to be competitive with regional jets on short/medium haul and providing, at the same time, a lower environmental impact.…”

“…All of the proposed concepts went through an MDAO process to achieve the minimum block fuel on a design range of 1600 NM. By comparing the proposed concepts with both an existing regional jet as the Airbus A220-300 operating on such a range and with a jet platform specifically designed for the same range, the three-lifting surfaces aircraft has been identified as the solutions having the maximum potential fuel saving, about 17% with respect to the reference regional jet [11]. This work also highlights that a reliable prediction of the downwash gradient at the horizontal tail is of a primary importance to perform a correct sizing of the horizontal tailplane in order to provide sufficient longitudinal static stability.…”