Stability, Flying Qualities and Parameter Estimation of a Twin-Engine CS23/FAR23 Certified Light Aircraft

This paper presents some results of the flight test campaign conducted on the Tecnam P2006T aircraft, on the occasion of its certification process. This twin-engine propeller airplane is certified in the category CS23/FAR23. Many preliminary flight tests on a prototype of this light aircraft were aimed at optimizing performances and flight qualities. These experiences led to the application of two winglets to the original wing. The final configuration was extensively tested for the purpose of CS23 certification achievement. At the same time the airplane model, through a dedicated set of flight maneuvers, has been characterized by means of parameter estimation studies. The longitudinal and lateral-directional response mode were assessed and quantified. All the aircraft stability derivatives have been estimated from the acquired flight data using the well-known Maximum Likelihood Method (MLM). Some estimated stability derivatives have been also compared with the corresponding values extracted from leveled flight tests and from wind-tunnel tests performed on a scaled model of the aircraft

Design, Analysis, and Testing of a Scaled Propeller for an Innovative Regional Turboprop Aircraft

This paper describes the design, numerical analyses, and wind tunnel tests of the scaled model of a propeller serving as a propulsive element for the experimental tests of an advanced regional turboprop aircraft with engines installed on the horizontal tailplane tips. The design has been performed by complying with the thrust similarity from the full-scale aircraft propulsive requirements. Numerical analyses with a high-fidelity aerodynamic solver confirmed that the initial design made with XROTOR would achieve the expected performance. Finally, a strengthened version of the propeller has been manufactured via 3D printing and tested in the wind tunnel. Test data include measurements of thrust as well as propeller normal force at different angles of attack. Good agreement between numerical and experimental results has been observed, enabling the propeller to be used confidently in the aircraft wind tunnel powered test campaign

Flow curvature effects on dynamic behaviour of a novel vertical axis tidal current turbine: numerical and experimental analysis

The paper deals with performances analysis of vertical axis turbine to exploit tidal marine currents. Flow curvature effects on performences of a novel vertical axis turbine have been investuigated. It has been shown that the flow curvature effect allows to design properly an accurate airfoil shape to increase turbine performances

Benchmark of different aerodynamic solvers on wing aero-propulsive interactions

Distributed electric propulsion is a fertile research topic aiming to increase the wing aerodynamic efficiency by distributing the thrust over the wing span. The blowing due to distributed propulsors shall increase the wing lift coefficient for a given planform area and flight speed. This should bring several advantages as wing area, drag, and structural weight reduction, which in turn reduce fuel consumption, allowing airplanes to fly more efficiently. However, there are no consolidated preliminary design methods to size a distributed propulsion system. Numerical analysis is then performed at early stage, where many design variables have not been fixed yet. Therefore, the design space is vast and exploring all the possible combinations is unfeasible. For instance, low-fidelity methods (VLM, panel codes) have a low computational time, but usually they do not account for flow separation and hence they are unable to predict the wing maximum lift. Conversely, high-fidelity codes (CFD) provide more realistic results, but a single drag polar sweep can last days. This work provides a benchmark of different aerodynamic solvers for a typical regional turboprop wing with flaps and distributed propulsion, to better understand the limits of each software in the prediction of aero-propulsive effects

Aerodynamic analysis and design of a twin engine commuter aircraft

The present paper deals with the preliminary design of a general aviation Commuter 11 seat aircraft. The Commuter aircraft market is today characterized by very few new models and the majority of aircraft in operation belonging to this category are older than 35 years. Tecnam Aircraft Industries and the Department of Aerospace Engineering (DIAS) of the University of Naples "Federico II" are deeply involved in the design of a new commuter aircraft that should be introduced in this market with very good opportunities of success. This paper aims to provide some guidelines on the conception of a new twin-engine commuter aircraft with eleven passengers. Aircraft configuration and cabin layouts choices are shown, also compared to the main competitors. The research activity also deals with the aerodynamic design that has been performed at DIAS during 2011 and it was focused on a general aerodynamic analysis and a deep investigation on some particular effects (such as the wing-fuselage interference or the nacelle lift contribution and their effect on wing span loading). The aerodynamic analysis was also essential to have an accurate estimation of aircraft stability and control derivatives (both longitudinal and lateral-directional) and to lead to a right sizing of tail surfaces. The aerodynamic analysis have been carried out through the use of a 3-D panel code internally developed and the aerodynamic analysis performed through 3-D panel code calculations have been also supported by semi-empirical estimation methodologies. Design of winglets to improve climb performance will be presented

Design and aerodynamic analysis of a twin-engine commuter aircraft

The present paper deals with the preliminary design of a new general aviation Commuter 11 seat aircraft. The commuteraircraft market is today characterized by very few new models and the majority of aircraft in operation belonging to this category are older than 35 years. Tecnam Aircraft Industries and the Department of Industrial Engineering (DII) of the University of Naples "Federico II" have been deeply involved in the design of a new commuter aircraft that should be introduced in the market with very good opportunities of success. This paper aims to provide some guidelines on the conceptual design of this new twin-engine commuter aircraft. Aircraft configuration and cabin layoutchoices are shown and compared to similar solutions adopted by main competitors. The aerodynamic analyses are focused on some particular effects such as the wing-fuselage interference and the nacelle lift contribution and their effect on wing span loading. The aerodynamic analyses have been also essential to validate the preliminary estimation of aircraft stability and control derivatives (both longitudinal and lateral-directional) and to lead to a right sizing of tail surfaces. These analyses have been carried out through the use of a 3-D panel code. Finally some preliminary wind tunnel test results are presented

An Investigation on Vertical Tailplane Design

The paper presents a deep investigation on the methodologies to design a vertical tailplane. Nowadays the most used methodologies in preliminary design to estimate the contribution of vertical tailplane on aircraft directional stability and control are: the classical method proposed by USAF DATCOM (also presented in several aeronautics textbooks) and the method presented in ESDU reports. Both methodologies derive from NACA world war II reports of the first half of the ’900, based on obsolete geometries, and give quite different results for certain configurations, e. g. in the case of horizontal stabilizer mounted in fuselage. As shown in literature, the main effects on the side force coefficient of the vertical tail are due to the interactions among the aircraft components: the fuselage acts like a cylinder increasing the local sideslip angle, the wing position and aspect ratio have an influence on the airflow near the tail zone and the horizontal tail, depending on position and size, can act as an endplate increasing the side force. In order to better highlight these effects, a different approach using the RANS equations has been adopted. Several CFD calculations have been performed on some test cases (used as experimental database) described in NACA reports and used in the past to obtain the semi‐empirical methodology reported in USAF DATCOM, to verify the compliance of CFD results with available experimental data. The CFD calculations (performed through the use of a parallel supercomputing platform) have shown a good agreement between numerical and experimental data. Subsequently the abovementioned effects have been deeply investigated on a new set of propeller transport aircraft configurations. The different configurations that have been prepared differs for wing aspect ratio, wing‐fuselage relative position (high‐wing/low‐wing), vertical tailplane aspect ratio (vertical tail span versus fuselage radius) and horizontal tailplane position respect to the vertical tailplane (in particular investigation the effect of fin‐mounted T configuration, typical of regional turboprop transport aircraft). For all configurations the computational mesh has been carefully analyzed and prepared. All the CFD analyses will be useful to obtain new curves to predict the above-mentioned effects and to have a more accurate estimation of vertical tailplane contribution to aircraft directional stability and control

Development of new preliminary design methodologies for regional turboprop aircraft by CFD analyses

Since 2011 the aerodynamic research group of the Dept. of Industrial Engineering of the University of Naples "Federico II" makes use of the University's computing grid infrastructure SCoPE to perform parallel computing simulations with the commercial CAE package Star-CCM+. This infrastructure allows Navier-Stokes calculations on complete aircraft configurations in a relative short amount of time. Therefore, the software and the above mentioned infrastructure allow the parametric analysis of several configurations that are extremely useful to the correct estimation of aerodynamic interference among aircraft components and to highlight some useful trends that could indicate how a specific aerodynamic characteristic (i.e. the drag of a component, the wing downwash or the directional stability contribution of the vertical tail) is linked to aircraft geometrical parameters. Thus, with the choice of a specific set of test-cases it is possible to make a deep investigation on some aerodynamic features and, from the analyses of results, it is possible to extract and develop ad-hoc semi-empirical methodologies that could be used in preliminary design activities. In this paper, two investigations are presented: the aerodynamic interference among aircraft components in sideslip and the aerodynamic characteristics of a fuselage, focusing on typical large turbopropeller aircraft category

Directional Stability Issues of a Three Lifting Surface Aircraft

This paper deals with the evaluation of the interference effects among aircraft components in a three lifting surface configuration, an innovative layout for a high-capacity turboprop (130 pax), which is supposed to be competitive with respect to short/medium haul regional jets. The feasibility study of such a configuration is framed within the Innovative turbopROp configuratioN (IRON) project. An experimental wind tunnel test campaign has been performed on a 1:25 scaled model at the main subsonic wind tunnel facility of the Industrial Engineering Department of the University of Naples Federico II. Beside the well-known detrimental effects of the angle of attacK on the sidewash, the experimental tests have highlighted a strong directional stability reduction due to the canard interference with both the fuselage and the vertical tail. Results have shown that the canard increases the fuselage instability of about 14%. The canard wake displacement also affects the aircraft directional stability. Results collected in this work have been useful to perform a redesign of the aircraft empennage and to schedule numerical high-fidelity analyses as well as a second wind tunnel test campaign on the updated aircraft model to get further insights on the aerodynamic interference, including propulsive effects

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

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