 Some early production aircraft had imported Bristol Jupiter VI engines with a metal cowling, but the bulk of the production aircraft used the M-22 license-built copy, both of , with a Townend ring.Early aircraft usually had a fixed-pitch wooden propeller with a diameter of , but these were replaced by a duralumin propeller without a spinner that could have its pitch adjusted on the ground.Two synchronized PV-1 machine guns were fitted in the fuselage with 600 rounds apiece with an OP-1 telescopic sight.