The H.26 (the first Hanriot fighter that did not use the HD nomenclature, where the D was for their long-standing designer Emile Dupont) was designed to compete in the 1921 CI (single-seat fighter) programme, the H.26 was the only participant powered by the 260hp (194 kW) water cooled Salmson 9Z nine-cylinder radial engine. Most other contenders were intended for the water-cooled inline 300 hp (224 kW) V-8 Hispano-Suiza HS 8F. The H.26 design attempted to compensate for lower installed power by means of aerodynamic cleanliness. It was an all-metal single bay sesquiplane, fabric covered except for the fuselage ahead of the cockpit. The lower wing was mounted at the bottom of the fuselage and the upper planes, built in separate pieces, braced close to the upper fuselage on short, faired extensions. There were ailerons only on the upper plane, the plan, structure and bracing of which was greatly altered during 1923.
The H.26 before covering at the Paris Aero Show December 1922, with early wings
When the H.26 made its first public appearance, at the Paris Aero Show in December 1922, the still uncovered upper wing of the unflown fighter had long, curved tips outboard of a straight edged, constant chord central section and had a single main spar. Sixteen months later, after the aircraft had flown, the wings had become rectangular and were built around two spars. The short span lower wing retained its single spar structure throughout but it, too, had curved tips replaced with square. The wing bracing had also changed: originally a bracing wire ran from the rear undercarriage structure upwards and outwards, via the lower to the upper wing. This was replaced by a single, wide chord rigid strut with an aerofoil section and widened at its roots.
3-view of the H.26 published early 1923, showing early wing plan, wire bracing and a different vertical tail to those of 1924.
The closely cowled radial engine set the diameter of the H.26's nose and drove a two blade propeller behind a large diameter domed spinner. The Salmson was initially cooled with a semi-circular Botali radiator to the rear of the engine. The H.26 had a fixed conventional undercarriage with mainwheels on a centrally hinged split axle, enclosed within a lift-contributing wing-like fairing and supported by N-form struts attached to the lower fuselage longerons on each side. Originally, these were reinforced by long vertical struts from the shock absorber attachments to the upper wing central section. These were discarded when the interplane wires were replaced by the faired interplane struts, which extended downwards to the rear undercarriage structure; the tops of the shock absorber struts were relocated to mid-fuselage on the engine mounting.
The pilot's cockpit, with a faired headrest behind it, was at the trailing edge of the upper wing, placed within a small cut-out to improve view. The H.26 had a fuselage built around four metal tube, cross-braced longerons, enclosed within metal formers and stringers to shape it into an oval cross-section. Behind him the fuselage tapered to the broad chord fixed tail surfaces. The mid-fuselage tailplane, which had a strongly swept leading edge, carried round tipped elevators that narrowed inboard. The vertical tail was oval shaped, with a broad chord rudder that ended at the top of the fuselage.
First flown at Orly in 1923, the H.26 utilised a Botali radiator arranged in a semi-circle behind the engine. As this was found to provide insufficient cooling, two Chausson radiators were attached to the undercarriage strutting. The H.26 displayed poor handling qualities, which, coupled with continued engine overheating and an inadequate view offered the pilot, led to the abandonment of further development after several test flights.
Engine: 1 × Salmson 9Z, 190 kW (260 hp)
Wingspan: 9.05 m / 29 ft 8 in
Length: 7.35 m / 24 ft 1 in
Height: 2.50 m / 8 ft 2 in
Wing area: 18.00 sq.m / 193.75 sq ft
Max take-off weight: 1150 kg / 2535 lb
Empty weight: 820 kg / 1808 lb
Max. speed: 260 km/h / 162 mph
Ceiling: 8500 m / 27900 ft
Range: 750 km / 466 miles