Before revision: Kermode, A.C., Mechanics of Flight, (p.76, eighth edition) For symmetric aerofoils, the chord line and the zero lift line are the same
After revision: .Clancy, L.J., Aerodynamics, paragraph 5.7(aKermode, A.C., Mechanics of Flight, (p.76, eighth edition) For symmetric aerofoils, the chord line and the zero lift line are the same