Introduction to Aircraft Aeroelasticity and Loads

15

Dynamic Manoeuvres

In Chapter 13, the balanced aircraft loads, trimmed condition and deformation in a steady symmetric equilibrium manoeuvre were considered for both a rigid and a simple flexible aircraft in heave and pitch. Such a manoeuvre is one in which the aircraft undergoes a steady acceleration normal to the flight path and a steady pitch rate (e.g. steady pull-out or banked turn) and where, by the application of D'Alembert's principle, the aircraft may be considered to be in static equilibrium under aerodynamic, thrust and inertia loads. Also, brief consideration was given to lateral equilibrium cases of a steady roll rate and steady sideslip, together with analysis of the abrupt application of the aileron or rudder, where the maximum angular acceleration was determined by balancing the applied aerodynamic moment by an inertia moment. These equilibrium manoeuvres are sometimes known as ‘bookcases’ (see Chapter 21); they are often somewhat artificial and unrealizable in practice, and may lead to overestimates of the internal loads, but are particularly useful early in the design cycle. However, a more ‘rational’ (or realistic/accurate; see Chapter 21) approach is often required by the certification specifications and may be used to obtain more realistic loads for some of the bookcases.

A dynamic manoeuvre (Lomax, 1996; Howe, 2004) involves applying some form of control input in such a way that a transient (time-varying) response of the aircraft is generated. To obtain ...