Deterministic, rule-following trajectory generation system for waypoint flight

Abstract Advanced Air Mobility operations require flight guidance systems that exhibit predictable, deterministic behavior and remain compatible with established navigation standards. Many existing online trajectory generation methods rely on numerical optimization, or time-parameterized references, which implicitly couple path geometry and speed control and complicate verification and certification. This paper presents a deterministic approach to online trajectory generation and guidance in which flight paths are defined as purely geometric objects, independent of time and speed. Track-To-Fix legs are treated such that they are consistent with ARINC-424, eliminating path-definition errors by construction. To support smooth fly-by transitions, an analytic curvature-aware local approximation of the orthogonal projection of the aircraft onto the reference trajectory is derived, enabling solver-free online footpoint propagation with explicit error bounds. The resulting separation between geometric trajectory definition and speed control yields deterministic and predictable behavior. Simulation and flight-test results demonstrate good tracking performance and compliance with navigation requirements relevant to eVTOL operations.