The Latham HB.5 was a French biplane flying boat with four engines in push-pull configuration pairs. Ten were used by the French Navy. Despite its military designation as an HB.5 or five-crew flying boat bomber, this four-engine aircraft was designed as a civil version of the Latham Trimoteur of 1919. The main design change was to move from three engines to four whilst retaining a total power of about 750 kW (1,000 hp). Its original Latham type number is not known. It was a large biplane, with unequal span wings of high aspect ratio for the day. In plan the wings, mounted with very slight stagger, were rectangular out to straight-angled tips. There were three parts, a central section attached to the upper hull which contained the engines and had no dihedral and outer sections with about 2° of dihedral. Each outer section was divided into two bays with three vertical pairs of interplane struts, the innermost at the junction with the central section. Outboard, the overhangs of the upper wing were supported by outward-leaning pairs of struts from the feet of the outer interplane pairs; below these points flat-bottomed floats which provided lateral stability on water were mounted on short struts. The upper centre section was supported over the fuselage with a pair of transverse pair of inverted V-struts. Balanced, short-span, broad-chord ailerons were mounted at the tips of the upper wing only. The HB.5's four water-cooled, nine-cylinder Salmson 9Z radial engines were mounted as push-pill pairs, with each pair sharing a single nacelle placed midway between the centre section wings on a frame of horizontal members and diagonal struts, tied to the inner interplane struts and the centre section V-struts. The 3.40 m (11.2 ft) interplane gap allowed the rear propellers to turn between the wings; the tractor pairs were just ahead of the wing leading edge. 1,000 l (220 imp gal; 260 US gal) of fuel was equally distributed between four fuselage tanks. For more details of the design and the operational history of the HB.5, click here.
