This paper provides a critical analysis of the planning and execution of the flight test program for the Bachem Ba 349 Natter, a vertically-launched, rocket-powered interceptor developed by Germany in the final phase of the Second World War. The study examines the program’s compressed, three-phase methodology, from initial unpowered aerodynamic validation to the fatal manned vertical launch. It argues that the program’s ultimate failure was a direct consequence of abandoning the foundational principles of incremental testing and procedural discipline. While the Natter’s core airframe demonstrated stability in gliding flight, the decision to advance to subsequent, more complex phases without resolving critical failures in powered systems integration represented a catastrophic breakdown in test planning. The single manned flight on March 1, 1945, which resulted in the death of test pilot Lothar Sieber, is presented as the inevitable outcome of a process that disregarded the necessity of building a chain of success from one test phase to the next. The paper concludes by identifying key lessons from the Natter program concerning the inviolability of structured test protocols, a theme that remains profoundly relevant in modern aerospace engineering.

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