Br.904 Nymphale • wp.archivoaereo.com

The creation of this high-performance glider, Breguet’s third, stemmed from the French team’s failure in the two-seater glider category at the 1954 World Championships. This new glider was directly derived from the single-seater Breguet 901, retaining its design principles and utilizing many common components.

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Innovative Design and Development

The wing featured a similar aerodynamic profile from the NACA 63 family, with a main spar forming its structural core. The leading edge created a robust box structure, while the trailing edge was reinforced with ribs. Much like the Breguet 901, the fabric skin of the wing was strengthened with plywood panels in high-stress areas, such as around the airbrakes.

The new glider’s fuselage employed a semi-monocoque wooden construction, analogous to the single-seater Breguet 901, with a spruce frame and plywood skin. Reportedly, multi-layered glass was used for the cockpit canopies. The front cockpit maintained the same shape and dimensions as that of the Breguet 901, resulting in a similar overall layout with minor experience-based modifications.

The tail unit was directly sourced from the Breguet 901 S but was scaled up in size. The control system elements remained identical, utilizing cables for rudder and elevator trim control, and rods for the elevator, ailerons, flaps, and airbrakes.

The new glider’s single-wheel landing gear was also similar to the Breguet 901 S, but featured a larger wheel (355 × 150 mm versus 330 × 130 mm). A novel addition to the undercarriage design was an auxiliary rubber roller equipped with a fabric fairing.

First Flight and Nomenclature

The Breguet 904-01 prototype made its maiden flight on May 26, 1956, piloted by Paul Lepanse. This aircraft, soon followed by a second prototype, was initially named Grand Sylvain in honor of Sylvain Floirat, who controlled the Breguet company. The type’s official designation, however, became Br.904 Nymphale, meaning ‘butterfly’.

Production Challenges and Legacy

Fifteen Br 904 gliders were manufactured in Aire-sur-l’Adour, with promises of subsequent orders from SALS, but these orders never materialized. The reasons were likely similar to those that limited the production of the Br 901, including excessively high costs and insufficient sales volumes.

A third prototype (No. 18) was utilized between 1959 and 1960 for testing a ‘butterfly’ type empennage fitted to the Br 905, contrasting with the classic cruciform tail of the Br 901-904 gliders.

Technical Specifications

Modification	Br.90 4
Wingspan, m	20.00
Length, m	9.00
Aspect ratio	20.00
Wing area, m2	20.00
Wing loading, kg/m2	26.20
Empty weight	358
Maximum takeoff weight	524
Maximum speed, km/h	220
Max. aerodynamic quality	33
Speed for max. aerodynamic quality, km/h	82
Minimum rate of descent, m/s	0.70
Speed for min. rate of descent, km/h	72
Crew, crew members	2