On each side a parallel pair of airfoil section struts braced the wing from the forward and rear spars to the lower fuselage longeron.

[3] The nose region forward of the pilot was smooth and slightly rounded but merged into a corrugated, flat sided and rectangular cross-section fuselage.

The central Salmson 9Ab 172 kW (230 hp) nine cylinder radial engine was mounted on the extreme nose, completely uncowled and driving a two bladed propeller.

In early drawings the fin was triangular and the rudder unbalanced[1] though this was modified by the time the Potez 40 was displayed, unflown, at the 1930 Paris Salon into a taller vertical tail with a clearly extended tip.

[1][4] The Potez 40 had a tailwheel undercarriage with its main legs with rubber shock absorbers mounted vertically below the outer engine extensions; the mainwheels were hinged on widely spaced V-Struts from the lower fuselage[1] and were sometimes enclosed under spats.