Dornier Komet

The Dornier Komet (Comet), Merkur (Mercury), Do C, Do D, and Do T were a family of aircraft designed and manufactured by the German aircraft manufacturer Dornier Flugzeugwerke.

Developed during the 1920s, the aircraft was originally operated as a small airliner. Military variants were subsequently developed, including a heavily modified floatplane torpedo bomber model. The earliest aircraft in the series were basically landplane versions of the Delphin flying boat, and although the Delphin and Komet/Merkur series diverged from each other, design changes and refinements from one family were often incorporated into the other. All variants were braced high-winged single-engine monoplanes with conventional landing gear.

The first Komets (Do C III Komet I) utilised the same rectangular plan, 17 m (55 ft 9 in) span wing, tail, and even upper fuselage, as well as the 138 kW (185 hp) BMW IIIa engine of the Delphin I, but replaced the lower fuselage and sponsons with a simple sheet-metal bottom that incorporated fixed tailskid undercarriage. The engine installation was also relocated from above the Delphin's nose to a conventional location in the Komet's fuselage nose. Accommodation was provided for a single pilot and four passengers. An improved version, the Do Komet II, was first flown on 9 October 1922 and was widely exported to countries including Colombia, Spain, Switzerland, and the Soviet Union.

The Do Komet III of 1924 was a practically all-new design that shared many elements with the Delphin III. The cabin was expanded to seat another two passengers and the larger wing, with a span of 19.6 m (64 ft 4 in), was raised above the fuselage on short struts. Power was greatly increased from the Komet I, with a 340 kW (450 hp) Napier Lion engine. This version was exported to Denmark and Sweden, but was also produced under licence in Japan by Kawasaki.

In 1925, the Komet III was replaced in production by the Do B Merkur I, which featured a revised fin and longer-span wings. When fitted with the BMW VI engine, it became known as the Do B Bal Merkur II, as did indeed any Komets thus re-engined. The type was widely used by Deutsche Luft Hansa, which had some 30 Merkurs operating at one time, and was also exported to Brazil, China, Colombia, Japan, and Switzerland.

The Do C and Do D were follow-on military designs, the former was a trainer exported to Chile and Colombia while the latter was a floatplane torpedo bomber built for the Yugoslav Royal Navy. The designation Do T was used for a landplane ambulance version.

The Dornier Komet family of aircraft were high-wing monoplane all-metal aircraft. The aircraft had a atypically low centre of gravity, which was partially attributable to the design of its undercarriage and made it unlikely for the aircraft to overturn even during challenging landings. Power was provided by a single nose-mounted engine. The aircraft was promoted for its ability to be used as an airliner, utility transport, air ambulance, aerial surveyor, in either a landplane or floatplane configuration.

The majority of the airframe was composed of duralumin except for highly-stressed components, which were made of steel instead. As an anti-corrosion measure, all steel parts were alloyed while the duralumin components, although a particularly corrosion-resistant light alloy, had a layer of protective paint applied. Almost all sections of the airframe were manufactured from strips of plate that were drawn in dies. This production technique resulted in particularly durable struts while plate sections were well-braced via their securing to flanged channel sections that were aligned to the direction of the external streamlines and at right angles to the interior, subdividing the shall into small rectangular sections. There was no use of either tubes or corrugated plate; flat plate was opted for as it readily absorbed stress in all directions. Parts were joined together using riveting in a manner that permitted repairs and even total replacement to be readily performed by non-specialist workers. Accessibility to all parts was also facilitated in the aircraft's design.