Danilo Ciliberti

Aerodynamic Interference Issues in Aircraft Directional Control

This work investigates the aerodynamic interference among airplane components caused by rudder deflection for a typical turboprop aircraft geometry through the computational fluid dynamics technique. At no sideslip, an airplane is in symmetric flight conditions. The rudder deflection creates a local sideslip angle close to the vertical tailplane, and this effect is increased by fuselage and horizontal tail. Typical semiempirical methods, such as United States Air Force Stability and Control Data Compendium (USAF DATCOM), do not take into account for these effects, proposing the same corrective parameters both for pure sideslip and rudder deflection conditions. Numerical analyses executed on several aircraft configurations with different wing and horizontal tailplane positions show that the interference factors are smaller than those predicted by the USAF DATCOM procedure, providing guidelines for a more accurate aircraft directional control analysis and hence rudder preliminary design.

A comprehensive review of vertical tail design

Purpose This work aims to deal with a comprehensive review of design methods for aircraft directional stability and vertical tail sizing. The focus on aircraft directional stability is due to the significant discrepancies that classical semi-empirical methods, as USAF DATCOM and ESDU, provide for some configurations because they are based on NACA wind tunnel (WT) tests about models not representative of an actual transport airplane. Design/methodology/approach The authors performed viscous numerical simulations to calculate the aerodynamic interference among aircraft parts on hundreds configurations of a generic regional turboprop aircraft, providing useful results that have been collected in a new vertical tail preliminary design method, named VeDSC. Findings The reviewed methods have been applied on a regional turboprop aircraft. The VeDSC method shows the closest agreement with numerical results. A WT test campaign involving more than 180 configurations has validated the numerical approach. Practical implications The investigation has covered both the linear and the non-linear range of the aerodynamic coefficients, including the mutual aerodynamic interference between the fuselage and the vertical stabilizer. Also, a preliminary investigation about rudder effectiveness, related to aircraft directional control, is presented. Originality/value In the final part of the paper, critical issues in vertical tail design are reviewed, highlighting the significance of a good estimation of aircraft directional stability and control derivatives.

Game theory and evolutionary algorithms applied to MDO in the AGILE European project

In this paper, an optimization technique in aircraft design field, based on game theory and evolutionary algorithms to define the key variables for Multi-Disciplinary aircraft Optimization (MDO) into AGILE (Aircraft 3 Generation MDO for Innovative Collaboration of Heterogeneous Teams of Experts) European project, is presented. This work represents one of the contributions given by UniNa (University of Naples “Federico II”) research group within the AGILE project, which is coordinated by the DLR and funded by EU through the project HORIZON 2020 that aims to create an evolution of MDO, promoting a novel approach based on collaborative remote design and knowledge dissemination among various teams of experts. Since the aircraft design field is very complex in terms of number of involved variables and the dimension of the space of variation, it is not feasible to perform an optimization process on all the design parameters; this leads to the need to reduce the number of the parameters to the most significant ones. A multi-objective optimization approach allows many different variables, which could be a constraint or an objective function for the specific investigation; thus, setting the constraints and objectives to reach, it is possible to perform an optimization process and control which parameters significantly affect the final result. Within AGILE project, UniNa research group aims to perform wing optimization processes in a preliminary design stage, coupling Nash game theory (N) with typical genetic evolutionary algorithm (GA), reducing computational time and allowing a more realistic association among objective functions and variables, to identify the main ones that significantly affect final result and that consequently must be considered by the partners of the AGILE consortium to perform MDO in the final part of project, applying the proposed optimization technique to novel aircraft configuration.

Aircraft directional stability prediction method by CFD

The aim of this paper is to present a new method to predict aircraft directional characteristics. The proposed approach is completely CFD based and it has been developed with more than 300 simulations of complete and partial aircraft configurations. The method accounts for mutual aerodynamic interference effects among components. First, the isolated vertical tailplane and fuselage yawing moment coefficients are calculated. Then, correction factors are applied to take into account for aircraft components (fuselage, wing, vertical and horizontal tailplanes). The corrected yawing moment coefficients represent the contributions of vertical tailplane and fuselage to aircraft directional stability, including the aerodynamic interference among all aircraft components. Finally, the method is tested and compared to typical semi-empirical approaches (USAF DATCOM, ESDU).

Wind tunnel testing of a generic regional turboprop aircraft modular model and development of improved design guidelines

This article presents results of a wide experimental aerodynamic test campaign, regarding the longitudinal and lateral-directional stability, performed in the low-speed wind-tunnel of the University of Naples “Federico II”, on a generic modular model of a modern regional turboprop aircraft. The modular model has been designed to arrange more than 200 possible different configurations with the modification of the aircraft main geometrical characteristics, such as wing-fuselage relative position, vertical tail size, and horizontal tail position. All tests, both longitudinal and lateral-directional, were addressed to the derivation of improved semiempirical formulations or surrogate models for the estimation of aerodynamic characteristics and derivatives for the regional turboprop aircraft category (similar to the ATR and Bombardier Q-Series) in preliminary design phase. Longitudinal tests were addressed to the measurement of aircraft lift, downwash, and horizontal tailplane contribution to longitudinal stability. Directional tests were instead focused on the correct estimation of vertical tail and fuselage contributions to directional stability for different vertical tail planforms, horizontal tail arrangements, and fuselage after-body shapes. The combined effects of wing and horizontal tail positions on aircraft lateral stability have also been investigated. All the obtained results are likely to be extremely useful for a future application in the preliminary design phase, since the derived charts may give indications for accurate sizing and position of both horizontal and vertical stabilizers.

Fuselage Aerodynamic Prediction Methods

A CFD-based method to predict longitudinal and lateral-directional aerodynamic coefficients of an aircraft fuselage has been developed. A reliable aerodynamic characteristic estimation is crucial in order to carry out a well-designed aircraft. About 30% of an aircraft zero lift drag source is attained to the fuselage. Fuselage longitudinal instability is impacting on wing and horizontal tail design, whereas aircraft directional stability characteristics are strictly related to the fuselage aerodynamics. This paper proposes methods to estimate fuselage aerodynamic drag, pitching, and yawing moment coefficients. Given the fuselage geometry, simple user friendly charts allow to evaluate its aerodynamic characteristics. The method is here explained and numerical test cases are shown on several fuselage geometries. Finally, a comparison with typical semi-empirical methods is presented.