Dornier Do-23

The Do 13 was first flown on February 13, 1933, with the same powerplant as its predecessor. Substitution of Junkers-type 'double-wing' trailing-edge flaps, similar to those of the Ju 52/3m, gave it improved landing characteristics, and when the Sh 22 engines were replaced by a pair of 750-hp 12-cylinder liquid-cooled BMW VIUs, driving four-blade propellers, the bomber was redesignated Do 13C. After further attempts to overcome deficiencies in the wing structure, it was ordered into series production by the Luftwaffe as the Do 23.

Two hundred and twenty-two Do 11s were reordered as Do 13Cs, but after about a dozen of these had been delivered, they were found to be even less satisfactory than the Do 11 C and D, and production was halted while the airframe was restressed and modified. Production was resumed after the first flight, on September 1, 1934, of the Do 13e prototype for the produc-tion Do 23F, with BMW VId powerplant. This was quickly followed by the Do 23G, which became the principal service version and returned to the BMW VIU engine. All unfulfilled orders for the Do 11 and 13 were transferred to the Do 23 contract, deliveries of which began in spring 1935, and had totalled just over 200 when production ended in late 1935.

The Do 23 was not destined for a long service life. From mid-1936 it began to be replaced by the Do 17, Ju 88 and He 111. It was then relegated to second-line duties, including training. Although obsolete by the outbreak of the Second World War, a small number did continue in service with Minen-suchstaffeln during the early war years, equipped with a large degaussing ring for clearing British mines from around the German coast.