Avia B 634
The B 634 represented the ultimate in the aerodynamic development of the basic B 34 single-seat fighter biplane design, and was to be numbered among the cleanest aircraft in its category ever flown. Tested in 1936, the B 634 was powered by an Avia-built HS 12Ycrs engine mounting a 20mm Oerlikon FFS cannon, two 7.7mm Model 30 machine guns being installed in the upper fuselage decking. There was virtually no commonality of components between the B 634 and the B 534.1 from which it was derived. By comparison with the earlier fighter, the upper wing of the B 634 featured increased chord while the lower wing had reduced chord, the wingtips were redesigned, the ailerons were broader, the gap was reduced (increasing the splay of the interplane struts), the stagger was greatly increased, and cut-outs were introduced on the lower wing roots. The curvature of the engine cowling and cockpit sill was refined, cantilever undercarriage legs were adopted and the radiator bath was faired cleanly between the leg roots. Despite a substantial reduction in drag, performance offered an insufficient improvement over that of the B 534 to warrant series production, the disappointing results provided by the B 634 being due primarily to a substantial increase in structural weight.
Two prototypes were built. The second had an enclosed canopy and different undercarriage. Both B-634 were pressed to service in 1938.
Engine: 1 x 850hp Avia-Hispano Suiza 12Ycrs
Wingspan: 9.40 m / 31 ft 10 in
Length: 8.35 m / 27 ft 5 in
Height: 3.06 m / 10 ft 0 in
Max take-off weight: 2340 kg / 5159 lb
Empty weight: 1710 kg / 3770 lb
Max. speed: 415 km/h / 258 mph
Cruise speed: 362 km/h / 225 mph
Ceiling: 11000 m / 36100 ft
Rate of climb: 960 m/min / 3150 ft/min
Range: 500 km / 311 miles
Armament: 1 x 20mm, 2 x 7.7mm