A binocular aircraft periscope has been constructed and flight tested. The periscope provided a 70-degree true field of view at a magnification of 1× and mechanically operated azimuth and declination prisms scanned 180 degrees. Flight instruments were included in the field of view. The periscope was installed in the nose of a B-17 aircraft together with a duplicate set of controls. Twenty impartial U. S. Air Force pilots carried out most routine flight operations competently. It is concluded that flight by this type periscope is feasible even by subjects with minimal training.
CHARLES J. CAMPBELL, LAWRENCE J. MCEACHERN, and ELWIN MARG, "Aircraft Flight by an Optical Periscope," J. Opt. Soc. Am. 46, 944-948 (1956)