Cockpit control knobs must conform to the general shapes (but not necessarily the exact sizes or specific proportions) in the following figure: [GRAPHIC] [TIFF OMITTED] TC28SE91.048 [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-72, 55 FR 29779, July 20, 1990]