What is a striking example of a dimension that makes no obvious sense in either measurement system?
Short answerA recalled 1920s French aircraft used propeller bolts about 9.27 mm wide and 92.7 mm long, dimensions that were not neat in inches either.
NotesA recalled 1920s aircraft had unusual propeller fasteners. The bolts holding the blades and hub together were about 9.27 mm in diameter and 92.7 mm in length. The panel converts the longer figure to roughly 3.649606 inches and finds no clean imperial explanation. The aircraft type is not named and the figures are offered from memory, so the example should retain that caveat. Design-specific calculations can produce manufacturing dimensions that are not round numbers in either metric or imperial units.