Introduction to Aircraft Aeroelasticity and Loads

23

Static Aeroelasticity and Flutter

In this chapter, an outline of typical industrial practice for static aeroelasticity and flutter calculations will be given and related to the earlier chapters in Part II. The certification requirements covering the issues in this chapter are seen primarily in CS/AMC 25.629 under Subpart D, Design and Construction. However, the requirements as written are dominated by considerations of flutter.

23.1 STATIC AEROELASTICITY

There is little specific mention of static aeroelastic phenomena in the certification specifications. The aeroelastic stability requirement (CS 25.629) simply states that ‘divergence, control reversal and any undue loss of stability and control as a result of structural deformation’ should be evaluated. In CS/AMC 25.629, it is stated that nonoscillatory aeroelastic instabilities (divergence and control reversal) should be analysed to show compliance with CS 25.629 and that loss of control effectiveness should be investigated, but little detail is specified.

However, static aeroelasticity appears indirectly in a number of situations via the effect of structural deformation on the rigid aircraft aerodynamic model and therefore upon gust and manoeuvre loads, etc. It is an important issue that must be considered.

23.1.1 Aircraft Model for Static Aeroelasticity

The aircraft model is traditionally very much the same as that employed for flutter and gust considerations, namely a whole aircraft beam or condensed FE model, but because ...