Helicopter flight dynamics – an introductory tour

In aviation history the nineteenth century is characterized by man’s re­lentless search for a practical flying machine. The 1860s saw a peculiar burst of enthusiasm for helicopters in Europe and the above picture, show­ing an 1863 ‘design’ by Gabrielle de la Landelle, reflects the fascination with aerial tour-boats at that time. The present chapter takes the form of a ‘tour of flight dynamics’ on which the innovative, and more practical, European designs from the 1960s – the Lynx, Puma and Bo105 – will be introduced as the principal reference aircraft of this book. These splendid designs are significant in the evolution of the modern helicopter and an understanding of their behaviour provides important learning material on this tour and throughout the book.

2.1 Introduction

This chapter is intended to guide the reader on a Tour of the subject of this book with the aim of instilling increased motivation by sampling and linking the wide range of subtopics that make the whole. The chapter is likely to raise more questions than it will answer and it will point to later chapters of the book where these are picked up and addressed in more detail. The Tour topics will range from relatively simple concepts such as how the helicopter’s controls work, through to more complex effects such as the influence of rotor design on dynamic stability, the conflict between stability and controllability and the specialized handling qualities required for military and civil mission task elements. All these topics lie within the domain of the flight dynamics engineer and within the scope of this book. This chapter is required reading for the reader who wishes to benefit most from the book as a whole. Many concepts are

introduced and developed in fundamental form here in this chapter, and the material in later chapters will draw on the resulting understanding gained by the reader.

One feature is re-emphasized here. This book is concerned with modelling flight dynamics and developing criteria for flying qualities, rather than how to design and build helicopters to achieve defined levels of quality. We cannot, nor do we wish to, ignore design issues; requirements can be credible only if they are achievable with the available hardware. However, largely because of the author’s own background and experience, design will not be a central topic in this book and there will be no chapter dedicated to it. Design issues will be discussed in context throughout the later chapters and some of the principal considerations will be summarized on this Tour, in Section 2.5.