Wing Structure of the Next-Generation Civil Tiltrotor: From Concept to Preliminary Design

Marika Belardo,Pierpaolo Ariola,Jacopo Beretta,Mariacarmela Capasso,Gianluca Diodati,Francesco Di Caprio,Mario Graziano,Salvatore Orlando,Nicola Paletta,Aniello Daniele Marano,Luigi Di Palma

doi:10.3390/aerospace8040102

Abstract

The main objective of this paper is to describe a methodology to be applied in the preliminary design of a tiltrotor wing based on previously developed conceptual design methods. The reference vehicle is the Next-Generation Civil Tiltrotor Technology Demonstrator (NGCTR-TD) developed by Leonardo Helicopters within the Clean Sky research program framework. In a previous work by the authors, based on the specific requirements (i.e., dynamics, strength, buckling, functional), the first iteration of design was aimed at finding a wing structure with a minimized structural weight but at the same time strong and stiff enough to comply with sizing loads and aeroelastic stability in the flight envelope. Now, the outcome from the first design loop is used to build a global Finite Element Model (FEM), to be used for a multi-objective optimization performed by using a commercial software environment. In other words, the design strategy, aimed at finding a first optimal solution in terms of the thickness of composite components, is based on a two-level optimization. The first-level optimization is performed with engineering models (non-FEA-based), and the second-level optimization, discussed in this paper, within an FEA environment. The latter is shown to provide satisfactory results in terms of overall wing weight, and a zonal optimization of the composite parts, which is the starting point of an engineered model and a detailed FEM (beyond the scope of the present work), which will also take into account manufacturing, assembly, installation, accessibility and maintenance constraints.

Highlights

Tiltrotors are a class of vehicle that combines the advantages of aircraft and helicopters (Vertical Take-Off and Landing (VTOL) ability)
The first one makes use of 1D beam theory to achieve the best wing-box thickness distributions able to cope with different load conditions encountered in-flight by the aircraft and respecting flutter stability; the second one is a refinement based on the use of a more accurate models, based on finite elements
The second-level optimization makes use of a more efficient but local optimization algorithm, to identify the best wingbox candidate satisfying, from an FE model point of view, the requirements starting from the good starting solutions highlighted during the first phase

Summary

Introduction

Tiltrotors are a class of vehicle that combines the advantages of aircraft (high cruise speed) and helicopters (Vertical Take-Off and Landing (VTOL) ability). Their commercial appeal is becoming increasingly important, with applications among various users, such as business, search and rescue, and medical. Within this framework, Horizon 2020 (H2020) Clean Sky 2 FRC IADP NextGenCTR will be dedicated to the design, construction and flying of an innovative Next-Generation Civil Tiltrotor Technology Demonstrator (NGCTR-TD) [1], the configuration of which will go beyond current architectures for this type of aircraft. The wing will be properly instrumented during the flight, with a set of sensors (strain gages and accelerometers) with the aim of validating load evaluation methods, structural monitoring for flight safety and aeroelastic characteristics

Objectives

Methods

Results