Avia BH-21

History of the Avia BH-21

In the 1920s, Czechoslovakian Avia shifted its focus to fighter jet production with the introduction of the "BH-21" Biplane Fighter. Preceded by a series of monoplanes and biplanes, the BH-21, first flown in 1925, played a vital role in Czechoslovak national security between World War I and World War II. Serving as both a competent fighter and a successful racer, it garnered praise for its robust design and won multiple air races in 1925.

The BH-21's development stemmed from the earlier BH-17, designed in response to a Czechoslovak Defense Department requirement. Despite initial deficiencies, a 1924 redesign led to the BH-21's final form, incorporating improvements like straightened interplane bracing for a better pilot field of view. In 1925, Avia produced 139 BH-21s for the Czechoslovak Air Force, and successful trials with the Belgian Air Force led to additional production under license by Belgian companies. While the BH-21 did not see combat, it paved the way for more advanced fighter types and served as a stepping stone in the evolution of aviation technology.

In Belgium, the BH-21 caught the attention of the Belgian Government, leading to an order of 45 units. Delivered in 1927, the Avia fighters served alongside the Nieuport NiD 29 C.1 until the early 1930s, when they were gradually replaced by the more modern Fairey Firefly. The Avia BH-21, powered by the Hispano-Suiza engine, proved favored due to its aerobatic capabilities and reliability. Its ultimate role was as an interim fighter, bridging the gap between the outdated Nieuport NiD 29 and the advanced Fairey Firefly, while maintaining Sabca's license production lines. The BH-21 was retired in 1934.

Specification

Basics

Years of Service: 1925

Origins: Czechoslovakia

Status: Retirement

Crew: 1

Production: 184

Carrier: Czechoslovakia; Belgium

Air-to-air combat, fighter: The general ability to actively attack other aircraft of similar form and function, usually using guns, missiles and/or airborne missiles.

Notable Features

Sync/Interrupt Gear: The automatic weapons are synchronized through a special mechanical gear assembly and fired by rotating propeller blades.

leafy: Added more main aircraft to improve inherent agility and provide tactical advantage in close combat.

Sturdy aircraft frame: The inherent ability of the airframe to take significant damage.

Rating Process: A manual process to allow the pilot and/or crew to exit in the event of an onboard emergency.

Dimensions and Weight

Length: 22.5 feet (6.87m)

Width/span: 29.2 feet (8.90m)

Height: 9.0ft (2.75m)

Cured weight: 1,687 lbs (765kg)

MTOW: 2,370 lbs (1,075 kg)

Wgt Difference: +683 lbs (+310 kg)

Main surface structure

Biplane: The design features a biplane wing arrangement with one main plane element on top of the other. Biplanes have improved agility at the expense of increased drag.

Up and down: Two main aircraft configurations where elements are stacked and positioned at different points on the fuselage.

Straight: Floor plans involve the use of simple, straight main plan elements.

Performance

Installed: 1 x Hispano-Suiza 8Fb V-8 300hp liquid-cooled in-line piston engine driving a twin-bladed propeller in the nose.

Maximum speed: 155 km/h (250 km/h | 135 kn)

Cruising speed: 118 km/h (190 km/h | 103 kn)

Maximum speed difference: +60 km/h (+ 32 kn)

Maximum: 26,001 feet (7,925 m | 5 km)

Area: 388 km (625 km | 1,157 nautical miles)

Rate of climb: 655 ft/min (200m/min)

Weapons

2 x 7.7mm Vickers machine guns (fixed, forward firing) mounted on the nose and fired synchronously via rotating propeller blades.