In February 1911, Louis Blériot developed the Bleriot XXI, an upgraded version of the Bleriot XI reconnaissance aircraft. This innovative monoplane was powered by a 52 kW (70 hp) Gnome Gamma 7 rotary engine, driving a two-bladed propeller. It featured a tandem configuration for pilot and passenger, with a central control column and dual rudder pedals allowing control from either position.
Design and Technical Features
The Bleriot XXI’s shallow, rectangular fuselage tapered towards a horizontal knife-edge at the tail, where an extended triangular horizontal stabilizer blended with the fuselage’s upper and lower surfaces. A semi-elliptical elevator was fitted on the trailing edge, and a triangular balanced rudder was positioned above the rear fuselage. Lateral control was achieved through wing warping, with wires leading to an inverted V-strut carriage above the fuselage and a similar V-strut below.
Fuel was stored in three tanks: a pair beneath the upper decking forward of the cockpit, and one pressurized tank beneath the main seat. The undercarriage was a variation of the well-proven design used on the Blériot XI, featuring wheels mounted on a trailing arm that could slide freely up and down, cushioned by bungee cords. The main vertical elements connected to a cross-bar below the fuselage and were reinforced with diagonal struts, a departure from the Blériot XI’s single upper spar attachment.
Early Service and Adaptations
The Bleriot XXI was one of two Blériot designs submitted for the 1912 British Military Aviation Competition. In 1912, the Bulgarian Air Force acquired several Bleriot XXI aircraft, marking their entry into early military service. The tail section of the aircraft was notably crafted from two U-shaped pieces of rattan cane, a unique construction detail.
Historical Significance and Upgrades
On August 13, 1913, during extensive summer maneuvers, Captain Petrov conducted the first operational mission in Bulgarian aviation history using a Bleriot XXI. Demonstrating its versatility, some aircraft were also equipped with floats for water operations. By 1913, most Bleriot XXI models received an upgrade to the more powerful Gnome Lambda engine, boosting its output to 80 hp.
Technical Specifications
| Modification | Bleriot XXI |
| Wingspan, m | 11.15 |
| Length, m | 8.31 |
| Wing area, m2 | 29.00 |
| Empty weight | 389 |
| Maximum takeoff weight | 599 |
| Engine type | 1 Piston engine Gnome Gamma 7 |
| Power, hp | 1 x 70 |
| Maximum speed, km/h | 95 |
| Cruising speed, km/h | 85 |
| Practical range, km | 406 |
| Crew | 1-2 crew |
| Armament | Not provided. In individual cases, several small bombs were carried on board, which were dropped manually or with the help of improvised devices. |
Image and diagram gallery of the Bleriot XXI
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