Avia S-199 - Design and Development

Design and Development

Avia continued building Messerschmitt Bf 109G-6s after the war under the Avia S-99 name, but soon ran out of the 109's Daimler-Benz DB 605 engine after many were destroyed during an explosion at a warehouse in Krásné Březno. The S-199 continued to use the Bf 109G airframe but, with none of the original engines available, an alternative engine had to be used. It was decided that as a replacement for the original engine, the aircraft would use the same engine (Junkers Jumo 211 F) and propeller as the Heinkel He 111 bomber. The resulting combination of parts was an aircraft with extremely poor handling qualities. The substitute engine with the propeller lacked the responsiveness of the Daimler-Benz unit and the torque created by the massive paddle-bladed propeller made control very difficult. This, in combination with the 109's narrow-track undercarriage, made landings and take-offs extremely hazardous.

The Daimler-Benz DB 605 engine allowed for a central cannon mount (Motorkanone in German) that fired through the propeller spinner. This was not possible with the Junkers Jumo 211, and so the S-199 used a version of the Luftwaffe's Rüstsatz VI modification kit, which consisted of a pair of MG 151 cannon, one each in a gun pod, one beneath each wing. This further impinged on the aircraft's performance. A final hidden danger lay in the gun synchronizer for the cowl-mounted MG 131 machine guns, which did not work as it was meant to, leading a few Israeli aircraft to shoot off their own propellers.

Around 550 S-199s were built, including a number of conversion trainers designated CS-199 (armed) and C-210 (unarmed). The first flight took place in March 1947, and production ended in 1949. The last examples were withdrawn from Czechoslovak service (with their National Security Guard) in 1957.