ESDU 99033 presents the formal equations of a normal mode analysis of the symmetric static aeroelasticity of a flexible aeroplane in steady trimmed flight or in a quasi-steady symmetric manoeuvre. The deformation of the aeroplane is represented by a finite number of structural normal modes, each mode involving wing bending and torsion, nacelle pylon pitch, bending and torsion, fuselage bending and tailplane bending and torsion. The equilibrium equations are expressed as functions of incidence, elevator angle and structural deformation over the entire aeroplane and these are determined in terms of dynamic pressure, Mach number and normal acceleration. The aeroplane is assumed classically configured and of the transport type with wings of medium to high aspect ratios and up to moderate sweep angles. The analysis is similar to that presented in ESDU 97032 in which wing and tailplane flexibility were represented by a finite number of assumed orthogonal modes in bending and torsion and tailplane flexibility was represented by a finite number of assumed orthogonal modes in bending and torsion. The fuselage was assumed rigid throughout its length.