The 1935 Do 18 was originally produced as a transatlantic mail-carrying flying-boat and used on the South Atlantic service of Deutsche Luft-Hansa. Evolved as a civil and military successor to the Dornier Wal, the first of five Do 18 prototypes (registered D-AHIS) flew on March 15, 1935, powered by two 540-hp Junkers Jumo 5 engines. These five pro-totypes were delivered to Deutsche Lufthansa. It was available in two forms as the Do 18E and Do 18F, with an AUW of 10,000kg and 11,000kg and with larger wings. A total of about 160 was eventually built during 1936-40, the major Luftwaffe versions being the Do 18D (about 75 built) and Do 18G and H (71 built).
The Do 18D-1, D-2 and D-3 differed in equipment only and were delivered from mid-1936. By the autumn of 1939 they equipped single Staffeln of five Kustenfliegergruppen (coastal aviation groups). Powered by 600-hp Jumo 205C engines, they were only lightly armed with single bow and dorsal 7.9-mm (0.311-in) MG 15 machine-guns, and could carry two 50-kg (110-lb) bombs beneath the starboard wing. Do 18Ds took part in many early wartime campaigns, among them Poland, Norway and the Battle of Britain.
The Do 18G-1, which entered service from mid-1939, had 880-hp Jumo 205D engines, a 13-mm (0.51-in) MG 131 in the bow, a 20-mm (0.79-in) MG 151 in a power-operated dorsal turret, and provision for rocket-assisted take-off. The Do 18H-1 was a six-seat unarmed trainer version.
Both the Do 18D and the Do 18G had been withdrawn from first-line service by autumn 1941, but some G-1s were converted to Do 18N-1s for air/sea rescue duties.
One Do 18 was redesignated Do 18L when its two 447kW Junkers Jumo 205 were replaced by 671kW BMW 132N. Do 18 were also operated as reconnaissance and search-and-rescue aircraft by the Luftwaffe, more than 70 being built for this purpose, plus a number of Do 18H trainers.
Engines: 2 x Jumo 205, 440kW
Max take-off weight: 10000 kg / 22046 lb
Empty weight: 6260 kg / 13801 lb
Wingspan: 23.7 m / 77 ft 9 in
Length: 19.3 m / 63 ft 4 in
Height: 5.4 m / 17 ft 9 in
Wing area: 98.0 sq.m / 1054.86 sq ft
Max. Speed: 260 km/h / 162 mph
Cruise speed: 240 km/h / 149 mph
Ceiling: 4200 m / 13800 ft
Range w/max.fuel: 5100 km / 3169 miles
Range w/max.payload: 2600 km / 1616 miles
Span: 23.70 m (77 ft 9 in)
Length 19.25 m (63 ft 2 in)
Gross weight: 10759 kg (23719 lb)
Maximum speed: 267 km/h (166mph)