Delanne 11

The Delanne 11 was designed by Maurice Delanne, better known for his later tandem-wing aircraft, together with Girault of Établissements Letord who built it.[1] Design features included a lightly loaded wing for low speed landings, a robust and well sprung undercarriage which could absorb the impacts of an inexperienced pilot's landings, an enclosed cockpit, with excellent all round views and space for parachutes and with a canopy that could be rapidly jettisoned in an emergency using a Letord-developed pressurised gas system.[2][3]

It was a low wing cantilever monoplane with plywood covered, two spar wooden wings of trapezoidal plan apart from slightly rounded tips. They were mounted with about 2° of dihedral on a very short centre section from which they could be easily demounted. There were long, narrow chord ailerons.[1]

The Delannne 11 was initially powered by a five-cylinder, air-cooled 48 kW (65 hp) Salmson 5A radial engine in the nose, fed from tanks in the wing centre section. Its steel tube mounting was the only major non-wooden structural part of the flat sided, ply skinned fuselage. A high long canopy dominated the upper fuselage, occupying about 40% of its length and enclosing two side-by-side seats, with baggage space behind them. The glazing was unusually free of frames, with just three rectangular glass panels on each side and a smaller, triangular window immediately behind the windscreen. At the rear, the glazing angled in towards the fuselage centreline, the two sides meeting at a vertical edge.[1] A combination of the simple glazing, the canopy height and the surrounding fuselage profile produced notably good all-round vision.[3]

The empennage was conventional, with the tailplane mounted on top of the fuselage. In plan the tailplane was semi-elliptical and the elevators almost semi-circular. The fin and unbalanced rudder also had curved edges and together were rather pointed; the rudder extended to the keel and operated in an elevator cut-out. The undercarriage was of the tailskid type, with a 2.07 m (6 ft 9 in) track.[2] The wheels were on bent split axles mounted on the centreline of the fuselage underside, their ends rubber sprung from vertical V-struts from the wing centre section.[1]

The Delanne 11 was marketed with a 52 kW (70 hp) Anzani 6-cylinder radial as an alternative to the Salmson.[1][4] Advertisements also offered a three-seat version, powered by an unspecified 72 kW (96 hp) engine;[5] there is no evidence that this variant was flown. No sales were made and only the prototype was built.

The first flight was made by Descamps on 8 March 1929 from Orly,[1] powered by the Salmson engine.[1] By April 1929 the prototype was Anzani powered.[6] It was registered as F-AJGB on 26 June 1929[7] and named L'Ibis Bleu (The Blue Ibis).[8]

At the end of June 1929 the Delanne 11 was displayed at the II^e Concours International d'Avions légers (Second light aircraft competition) in Rotterdam. It was flown by Descamps, the only French pilot there.[9] In May 1931 it was being offered for sale[8] and was re-registered with a new owner in January 1931.[7] It remained active into 1933 and was scheduled to appear at Le Grand Rally de Vins de Bordeaux in late June.[10]

Delanne 11 3-view drawing from L'Aéronautique July,1929

Data from Les Ailes 11 April 1929[1]

General characteristics

• Crew: One
• Capacity: One passenger.
• Length: 7.70 m (25 ft 3 in)
• Wingspan: 13.50 m (44 ft 3 in)
• Height: 2.25 m (7 ft 5 in)
• Wing area: 23 m² (250 sq ft)
• Empty weight: 600 kg (1,323 lb) production aircraft would have been 500 kg (1,100 lb)
• Max takeoff weight: 850 kg (1,874 lb)
• Powerplant: 1 × Anzani air-cooled, six cylinder radial, 52 kW (70 hp) or a 48 kW (65 hp) Salmson 5A air-cooled five cylinder radial engine. Les Ailes[1] does not state which engine fitting provided the given weights and length.
• Propellers: 2-bladed

Performance

• Maximum speed: 145 km/h (90 mph, 78 kn) at ground level. All performance figures are calculated
• Endurance: 5 hr at 850 kg (1,870 lb)[2]
• Service ceiling: 4,000 m (13,000 ft)