Aircraft projects begin before reliable details of foreign rivals are available, so designers commonly work from their own previous type. For the A6M team, that baseline was the A5M and the accumulated experience of making it a practical naval fighter. One of the earliest and most consequential decisions was engine selection. An engine had to be powerful enough for the specification, dependable enough for operations, and available in sufficient quantities for the intended fleet. A poor choice could therefore limit performance, reliability, and procurement before the rest of the airframe was mature.
Chapter · 44:08-46:14
The A5M set the baseline for the Zero's design team
The Zero's designers improved from the A5M they knew, while early engine selection constrained performance, reliability, and production volume.