Because aerospace structures rely on incredibly thin sheet metal and composites, they often fail due to instability (buckling) long before the material reaches its ultimate tensile strength. Column Buckling

The manual calculations taught in Curtis's text form the exact logic used by commercial finite element solvers like MSC Nastran, ANSYS, or Abaqus. To maximize the value of your study:

Curtis mixes SI and US Customary units. The PDF Appendix on unit conversion is gold. Always set your PDF view to show that appendix tab while solving problems.