The Blériot XII was a high wing tractor configuration monoplane with a deep uncovered fuselage, with the wings mounted on the upper longerons and the pilot and passenger seated between upper and lower longerons below the trailing edge of the wing. Lateral control was effected by a pair of ailerons mounted independently of the wings on the lower longerons behind the pilot. The prototype was initially powered by an E.N.V. Type D water-cooled engine mounted on the lower longerons, driving a two-bladed propeller mounted at the same level as the wing via a chain with a reduction ratio of about 2:1. When first flown the empennage consisted of an elevator at the extreme rear of the fuselage, with a separate fixed horizontal surface mounted above and in front of it, and three small rectangular rudders above the elevator.Opdycke 1999 p.55 After initial flight trials during May 1909 the rudders were removed. Various configurations were experimented with, the final arrangement being an elongated triangular fin with a rectangular unbalanced rudder hinged to the trailing edge.
