ESDU Engineer
Issue 13
Aircraft Aeroelasticity
ESDU 03011 An introduction to lateral static aeroelasticity: controllability, loads and stability
This Data Item introduces lateral static aeroelasticity in which the effects of structural deformation on lateral stability, controllability and loading in steady lateral manoeuvres are considered. In the case of lateral motion, asymmetric loading comprises symmetric plus antisymmetric loadings in which the antisymmetric deformations are superimposed on the symmetric deformations. Antisymmetric loading on the aeroplane components results in antisymmetric wing bending and twist, rear fuselage bending and torsion, antisymmetric tailplane bending and twist, fin bending and twist and antisymmetric engine nacelle pylon bending and twist.
The effects of deformations are quantified using the concept of modified derivatives in which the stability derivatives associated with rigid aeroplane stability and controllability are changed to incorporate deformation effects, assuming all dynamic effects can be neglected, a reasonable assumption in lateral stability motions and lateral manoeuvres. The modified derivatives are derived in qualitative terms to illustrate their behaviour and the important roles of divergence speeds and reversal speeds are identified.
The analysis of this Item is in line with the approach of Item 96037, which provides a qualitative introduction to longitudinal aeroelasticity, where the effects of symmetric deformations on longitudinal controllability, quasi-static loads, static stability, trim characteristics and quasi-steady pull-out manoeuvres of both swept and unswept configurations are described. In this Item, like the previous Item, the various components, wing, tailplane, fin, fuselage and engine nacelles and pylons, all deform relative to a reference state, but now the deformations are antisymmetric, giving rise to changes in lateral stability and controllability and in the antisymmetric loading distributions.
The effects of structural flexibility on the lateral stability characteristics are assessed by noting the changes in the approximations for static stability, spiral mode, rolling subsidence and Dutch roll in terms of the lateral stability derivatives when modified derivatives are used.
Related Items that deal with loading in quasi-steady longitudinal manoeuvres are Items 94009, which concentrates on loading aspects, and 94045, which deals with shear force, bending moment and torque. Longitudinal static aeroelasticity, with assumed modes and normal modes, is dealt with in Items 97032 and 99033, respectively.
RELATED DATA ITEMS
ESDU 94009 Symmetric steady manoeuvre loads on rigid aircraft of classical configuration at subsonic speeds.
ESDU 94045 Shear force, bending moment and torque of rigid aircraft in symmetric steady manoeuvring flight.
ESDU 96037 A qualitative introduction to static aeroelasticity:controllability, loads and stability.
ESDU 97032 Static aeroelasticity: a formal analysis using assumed modes.
ESDU 99033 Static aeroelasticity: a formal analysis using normal modes.
ESDU 01010 Loading on a rigid aeroplane in steady lateral manoeuvres.
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