Abstract
This paper deals with the experimental assessment of the aerodynamic characteristics of an innovative large turboprop aircraft. The configuration is a three-lifting surfaces airplane with rear engine installation at tail tips, conceived to carry up to 130 passengers and targeting a minimum economic and environmental impact, which is competitive with regional jets on short and medium hauls. The three-lifting surfaces layout is the output of previous research made by the authors, and it has been selected to fully comply with the market and design constraints. An experimental test campaign was required to validate the aerodynamics, stability, and control of this innovative configuration. From the results of the first campaign, it appeared that the aircraft had insufficient longitudinal and directional stability. Thus, the authors worked to improve these characteristics, updating the design and executing a second wind tunnel test campaign. The evolution of the design is described in the first part of the paper. In the second part, the authors discuss the aerodynamic interference effects among aircraft components, detailing how the combined downwash coming from both the canard and wing, as well as their wakes, affects the empennage aerodynamics. Experimental tests have revealed a significant reduction of the longitudinal stability due to canard additional downwash, especially at low attitudes. Furthermore, it was found that the canard generates a non-linearity on the aircraft directional stability derivative at moderate sideslip angles because of its tip vortex impinging on the vertical tail. Despite the detrimental interference due to the canard, the updated aircraft proved to be statically stable with sufficient margin at the most rearward center of gravity. Lessons learned in this research may be useful to aerodynamicists and aircraft designers facing similar issues.
Highlights
This research work is framed within the European research project named IRON
This latter is defined as the position of the center of gravity about which the pitching moment coefficient is invariant with the angle of attack [12]
The slope CMCL, which is a measure of longitudinal stability, is numerically equal to the difference between the center of gravity (CG) position and the neutral point, both expressed as fraction of mean aerodynamic chord (MAC)
Summary
This research work is framed within the European research project named IRON. The research program is addressed to the performance improvement of regional aircraft within the 90–150 passenger segment. Even if the market forecasts made by the most important manufactures at the beginning of 2020 have been completely changed by the unexpected COVID-19 outbreak [1], when a full recovery from this pandemic disease will be reached most of the major airlines will still have to face a key factor influencing the regional market scenario, which is represented by the need to replace several hundred heritage aircrafts and the world demand for new aircrafts in the segment of 20–150 seats [2–6]. This segment is characterized by the predominance of regional jets. The introduction of a large turboprop should help in reducing the aviation environmental impact
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