Quote:
Originally Posted by JtD
In case some folks can't be bothered to read the NACA tests, I'll post a part to put the "unacceptable longitudinal dynamic stability" into proper perspective.
Eventually, the longitudinal stability was not unacceptable. The Spitfire was accepted into service with about 20+ military air forces, was built in 20000 examples, and is still being flown today. Unacceptable longitudinal stability would mean acceptance into 0 air forces, and a production of a handful of examples, and none would be cleared for flying today.
However, it is true that the Spitfire did not meet all the requirements set by NACA in "Requirements for Satisfactory Flying Qualities of Airplanes". Other planes that failed to meet all the requirements were for instance the P-39 or the XP-51.
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The DC-3 also had longitudinal stability and control issues. The fact both the Spitfire and DC-3 had long careers is not an excuse to dismiss flying quality requirements. It is perfectly reasonable to assume that both of these fine airplanes would have been even better had they been more longitudinally stable under all flight conditions. Nobody has ever run definitive, statistically valid experiments on the value of good flying qualities in terms of accident reduction or military success. Common sense prevails and the entire world has since adopted stability and control standards to reduce accidents and increase air to air combat effectiveness.
