[4] Behind the central engine the fuselage had a largely circular section, built up from frames with a maximum diameter of 2.4 m (7 ft 10 in) linked by stringers and ply-covered into a semi-monocoque structure.

[2][4] The fin was integral with the body, rising slowly from it (a characteristic feature of Couzinet's designs) and carrying a pointed, curved, deep and narrow rudder.

The Arc-en-Ciel's triangular plan tailplane, mounted near mid-fuselage, had a tapered elevator with a curved cut-out for rudder movement.

[3] The Couzinet 10 had fixed, conventional landing gear, with mainwheels below the outer engines on V-struts from the wing spars and with rubber cord shock absorbers.

[6] The Type 11 crashed at Orly on 8 August 1928 following intense aileron flutter at speed, killing both Drouhin and engineer André Lanet.

[7] A second airframe, intended to have three Hispano 12Lb engines, was barely started when it was destroyed with the first Couzinet 20 in the hangar fire at the workshops of the Société d'Aviation Letord at Meudon, France, on 17 February 1930.