In accordance with an exemplary embodiment, a method for manufacturing a bypass valve of a turbine engine control system is described. The bypass valve includes a proportional valve and an integrator valve and the integrator valve includes an integrator spring assembly. The method includes forming the integrator spring assembly using an additive manufacturing technique. The integrator spring assembly comprises first and second end portions with a spring portion disposed between the first and second end portions. The first and second end portions and the spring portion are formed as an integral unit without welding or brazing using the additive manufacturing technique. The method further includes assembling the integrator spring assembly, the integrator valve, and the proportional valve into a complete bypass valve assembly.