Design and development
In mid-1926 the Polish magazine Mlody Lotnik published details of a basic glider, designed by Antoni Uszacki, financed by LOPP and with technical help and operational guidance from W.C.B.L and Władyslaw Zalewski, offering low cost, detailed plans and constructional advice. Several were built by Mlody Lotnik's young readership, some incorporating their own modifications. To introduce new pilots to flying, the Mlody Lotnik could be operated as a manned kite, then later in their training launched conventionally. [1]
Both the wing and the fuselage of the Mlody Lotnik were unusual. By 1926 biplane gliders, never common, had almost disappeared but the Mlody Lotnik was an all-wood single bay biplane. Its wings were braced on each side with a pair of parallel, vertical interplane struts which projected above the upper surface, assisted by wires both above and between the wings. Its upper and lower wings had unequal spans but no stagger. Fabric covering was applied only to the wing undersides. [1] [2]
In aviation, stagger is the relative horizontal fore-aft positioning of stacked wings in a biplane, triplane, or multiplane.
Aircraft fabric covering is a term used for both the material used and the process of covering aircraft open structures. It is also used for reinforcing closed plywood structures, the de Havilland Mosquito being an example of this technique, and on the pioneering all-wood monocoque fuselages of certain World War I German aircraft like the LFG Roland C.II, in its wrapped Wickelrumpf plywood strip and fabric covering.
Wooden, open frame fuselage gliders were common before World War II. Most, like the influential German Zögling and the Polish Wallis S.1, had a single frame but some had two frames in parallel like the Karpiński SL.1 Akar. The Mlody Lotnik mixed these forms with a fuselage with a narrow Y-shape plan, forked forwards but single aft. Built principally from a mixture of 50 and 25 mm (1.97 and 0.98 in) diameter pine rods, the upper and lower chords were almost parallel, cross braced with vertical and diagonal members. The pilot's completely open seat and controls were mounted across the fork under the wing leading edge. Each branch of the Y carried a landing skid, U-shaped in profile; alternatively, take-offs and landings could be made on the pilot's feet. [1] [2]
World War II, also known as the Second World War, was a global war that lasted from 1939 to 1945. The vast majority of the world's countries—including all the great powers—eventually formed two opposing military alliances: the Allies and the Axis. A state of total war emerged, directly involving more than 100 million people from over 30 countries. The major participants threw their entire economic, industrial, and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. World War II was the deadliest conflict in human history, marked by 70 to 85 million fatalities, most of whom were civilians in the Soviet Union and China. It included massacres, the genocide of the Holocaust, strategic bombing, premeditated death from starvation and disease, and the only use of nuclear weapons in war.
The Wallis S.1, sometimes known as Walis S-1 or Wallisa S-I, was a Polish glider designed to compete in the Second Polish Glider Contest, held in 1925 where it won two prizes.
The SL.1 Akar (Gnat) was a Polish glider built to compete in the First Polish Glider Contest, held in 1923. It dominated the contest with its pilots achieving first and second places.
The frames merged at the penultimate vertical cross member, where the empennage began. A delta-plan tailplane was mounted on the top of the frame and extended rearwards to the final cross-member, which reached above the frame and formed the rudder post. The Mlody Lotnik's fin started at the same point as the tailplane and was also triangular, though low; the rudder, a cropped rectangle in profile, extended to the bottom of the frame. All tail surfaces were fabric-covered. [1] [2]
The empennage, also known as the tail or tail assembly, is a structure at the rear of an aircraft that provides stability during flight, in a way similar to the feathers on an arrow. The term derives from the French language word empenner which means "to feather an arrow". Most aircraft feature an empennage incorporating vertical and horizontal stabilising surfaces which stabilise the flight dynamics of yaw and pitch, as well as housing control surfaces.
A tailplane, also known as a horizontal stabiliser is a small 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 gyroplanes. Not all fixed-wing aircraft have tailplanes. Canards, tailless and flying wing aircraft have no separate tailplane, while in V-tail aircraft the vertical stabiliser, rudder, and the tail-plane and elevator are combined to form two diagonal surfaces in a V layout.
A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other conveyance that moves through a fluid medium. On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane. A rudder operates by redirecting the fluid past the hull (watercraft) or fuselage, thus imparting a turning or yawing motion to the craft. In basic form, a rudder is a flat plane or sheet of material attached with hinges to the craft's stern, tail, or after end. Often rudders are shaped so as to minimize hydrodynamic or aerodynamic drag. On simple watercraft, a tiller—essentially, a stick or pole acting as a lever arm—may be attached to the top of the rudder to allow it to be turned by a helmsman. In larger vessels, cables, pushrods, or hydraulics may be used to link rudders to steering wheels. In typical aircraft, the rudder is operated by pedals via mechanical linkages or hydraulics.
The first group to complete an example of the Mlody Lotnik was the Warsaw 'Start' Aviation Circle, who incorporated some improvements and named their aircraft the K.S.L.1. This was also on show at the 1927 LOPP exhibition in Warsaw. It is not known how many other examples were completed and flown; another modified Mlody Lotnik was built by pupils at the National Industrial School in Krakov, directed by Arcinowski. [1] [2]
