The Udet U 7 Kolibri (Hummingbird) was a single engine, single seat,

parasol wing A monoplane is a fixed-wing aircraft configuration with a single mainplane, in contrast to a biplane or other types of multiplanes, which have multiple wings. A monoplane has inherently the highest efficiency and lowest drag of any wing confi ...

light aircraft A light aircraft is an aircraft that has a Maximum Takeoff Weight, maximum gross takeoff weight of or less.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 308. Aviation Supplies & Academics, 1997. Light aircraft are use ...

, designed and built in

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

in the mid-1920s. Though they had some competition success and set an unofficial lightplane duration record, only two were produced.

Design and development

The wooden,

cantilever A cantilever is a rigid structural element that extends horizontally and is unsupported at one end. Typically it extends from a flat vertical surface such as a wall, to which it must be firmly attached. Like other structural elements, a cantilev ...

, two-spar wing of the U 7 was almost trapezoidal in plan, with sweep on the

leading edge The leading edge is the part of the wing that first contacts the air;Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 305. Aviation Supplies & Academics, 1997. alternatively it is the foremost edge of an airfoil sectio ...

, out to ellipsoidal tips. It also thinned outwards in section with most of the taper on the upper surface, giving some anhedral. Short

ailerons An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement around ...

extended to the tips. The wing was mounted over the

fuselage The fuselage (; from the French language, French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds Aircrew, crew, passengers, or cargo. In single-engine aircraft, it will usually contain an Aircraft engine, engine as wel ...

on six streamlined steel

strut A strut is a structural component commonly found in engineering, aeronautics, architecture and anatomy. Struts generally work by resisting longitudinal compression, but they may also serve in tension. A stay is sometimes used as a synonym for ...

s; two upright tripods ran from the forward spar to points on the upper and mid fuselage and two inverted V-struts joined the rear spar to the upper fuselage. When the U 7 first appeared in 1924 it was powered by a

Douglas Douglas may refer to: People * Douglas (given name) * Douglas (surname) Animals * Douglas (parrot), macaw that starred as the parrot ''Rosalinda'' in Pippi Longstocking * Douglas the camel, a camel in the Confederate Army in the American Civil ...

flat twin A flat-twin engine is a two-cylinder internal combustion engine with the cylinders on opposite sides of the crankshaft. The most common type of flat-twin engine is the boxer-twin engine, where both pistons move inwards and outwards at the same ti ...

, mounted in a squared-off

cowling A cowling (or cowl) is the removable covering of a vehicle's engine, most often found on automobiles, motorcycles, airplanes, and on outboard boat motors. On airplanes, cowlings are used to reduce drag and to cool the engine. On boats, cowlings ...

with its cylinders exposed for cooling. By June 1924 this had been replaced by a Douglas flat twin. In the summer of 1925, one of the two U 7s built had a

ABC Scorpion The ABC Scorpion is a 30 hp (22 kW) two-cylinder aero engine designed by British engineer Granville Bradshaw for use in light aircraft. The engine was built by ABC Motors Limited and first ran in 1921.Gunston 1989, p.9. Variants ;S ...

flat twin, similarly enclosed. Behind the engine the rectangular section fuselage was

plywood Plywood is a composite material manufactured from thin layers, or "plies", of wood veneer that have been stacked and glued together. It is an engineered wood from the family of manufactured boards, which include plywood, medium-density fibreboa ...

covered, with an open

cockpit A cockpit or flight deck is the area, on the front part of an aircraft, spacecraft, or submersible, from which a pilot controls the vehicle. The cockpit of an aircraft contains flight instruments on an instrument panel, and the controls th ...

under the wing. The Kolibri's tail was conventional, with a trapezoidal plan

tailplane A tailplane, also known as a horizontal stabilizer, is a small lift (force), lifting surface located on the tail (empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters ...

and

elevator An elevator (American English) or lift (Commonwealth English) is a machine that vertically transports people or freight between levels. They are typically powered by electric motors that drive traction cables and counterweight systems suc ...

s mounted on top of the fuselage and with a quadrantal

fin A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. F ...

and a rounded

rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, airship, or other vehicle that moves through a fluid medium (usually air or water). On an airplane, the rudder is used primarily to counter adverse yaw ...

that reached down to the keel. It had a very simple, fixed, tailskid

undercarriage Undercarriage is the part of a moving vehicle that is underneath the main body of the vehicle. The term originally applied to this part of a horse-drawn carriage, and usage has since broadened to include: *The landing gear of an aircraft. *The ch ...

with the mainwheels on a short single axle held just below the fuselage underside, making the track narrow. ETHBIB

Operational history

The U 7s took part in several contests. One of the earliest was the August 1924 Rhön meeting for gliders and lightplanes. There were thirty of the latter, though several were motorised gliders rather than sports tourers. The weather was not good, with high winds, and the Kolibri, flown by Udet, was the only one of three powered aircraft to complete the round trip from the

Wasserkuppe The Wasserkuppe (;) is the highest mountain in the Rhön Mountains, Rhön range and the tallest elevation in the Germany, German state of Hesse, standing at above sea level. It forms a prominent plateau within the Fulda district and is known as ...

Kissingen Bad Kissingen () is a German spa town in the Bavarian region of Lower Franconia and County town, seat of the Bad Kissingen (district), district Bad Kissingen. Situated to the south of the Rhön Mountains on the Franconian Saale, Franconia ...

and back, thus winning first prize. In October 1924 Udet, again starting from the Wasserkuppe, flew the U 7 for 4 hr 39 min, an unofficial record for very light aircraft. There was no official recognition of this class of aircraft at the time. The two Kolibris, fitted with the engines used at the Rhön, flew in the demanding "Round Germany Flight" which began on 9 June 1925. They were expected to do well but the ABC powered machine had to make two forced landings on the first day, resulting in some damage. Neither was amongst the small group from the lowest power class that completed enough circuits to be amongst the prizes; the winner was the Daimler L21.

Specifications

References

External links

* {{Udet aircraft Udet aircraft Parasol-wing aircraft 1920s German civil aircraft Single-engined tractor aircraft Aircraft first flown in 1924