Design Guidelines, Experimental Investigation and Numerical Analysis of a New Twin Engine Commuter Aircraft

At the end of the year 2011, statistical data reports that the average age of general aviation registered aircraft is 46 years for single-engine piston powered aircraft and 15 years for single-engine turboprop aircraft. The average age for twin-engine 8-12 seats aircraft is 42 years for piston powered models and about 29 years for twin-engine turboprop commuter aircraft. These data show the need of a new aircraft model, also characterized by the application of new technologies like composite, light structures, new engine(with lower weight and fuel consumption), new avionics and flight control systems and new and advanced aerodynamics (i.e. optimized airfoil and winglet). Therefore, since the beginning of the year 2012, Tecnam Aircraft Industries and the Department of Industrial Engineering 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 good opportunity of success. This research work provides some general guidelines on the conceptual design of a new twin-engine commuter aircraft with eleven seats highlighting some general features that are directly coming from market requirements. Aircraft configuration and cabin layout choices are shown and compared to similar solutions adopted by main competitors. The preliminary design has been accomplished through the classical semi-empirical approaches, under the guidance of Prof. Luigi Pascale, designer of all Tecnam aircraft. The preliminary design has been also supplied with aerodynamic analyses performed with a 3-D panel code solver with the aim to verify the aircraft longitudinal and lateral-directional stability. To improve aircraft flight performance, in particular for the climb phase, winglets have been specifically design for this aircraft in order to reduce the wing induced drag. The aerodynamic analyses have been also addressed to a preliminary estimation of the wing loading, highlighting the effect of fuselage, nacelles and winglets. Identified the final layout and sizing of the aircraft, a 1:8.75 scale model has been build by Tecnam Aicraft Industries, and a wide wind tunnel test campaign has been fulfilled in the main subsonic wind tunnel facility of the Department of Industrial Engineering. Wind tunnel test have been focused on the estimation of the general aerodynamic characteristics of the aircraft. Several aircraft configurations have been tested in order to estimate the contribution of each aircraft component to the whole aircraft longitudinal and lateral-directional stability and control characteristics. To take into account the wind tunnel scaling effects providing more reliable data dealing with the free flight conditions, a wide numerical investigation through a Navier-Stokes equations solver has been performed. The reliability of the numerical investigation has been preliminary validated performing simulations at the wind tunnel conditions and comparing results with the available experimental data. The numerical analyses have been also useful to supply data not available form the wind tunnel tests, such as the accurate estimation of the wing span loads and stall path at free flight conditions (both in flap up and full flap configuration), a complete drag breakdown estimation (useful for aircraft performance estimation) and in order to predict the aircraft maximum lift coefficients(both in clean and flapped configuration). A preliminary investigation about the benefits that could be provided by the wing-fuselage fairing in terms of drag reduction, has been assessed through Navier-Stokes solver. Finally, an estimation of the aircraft flight performance has been fulfilled and effects of drag reduction in terms of maximum achievable cruise speed and fuel consumption an a typical possible mission profile has been presented