PZL-104 Wilga (golden oriole) is a Polish short-takeoff-and-landing (STOL) civil aviation utility aircraft designed and originally manufactured by PZL Warszawa-Okęcie, and later by European Aeronautic Defence and Space Company (EADS), who had acquired the original manufacturer during 2001. First flown on 24 April 1962 and entering service during the following year, the Wilga has evolved through many ever-improving versions during its continuous production from 1962 to 2006. The type was largely used by civil operators; those military air services that did fly the type typically used it as a trainer and liaison aircraft. In excess of 1,000 aircraft were produced prior to European Aeronautic Defence and Space Company (EADS) announcing on their website that production of the Wilga would cease in 2006. The PZL-104 was designed for robust use in sports and civil aviation, with a strong emphasis on glider-towing and parachute training. On 24 April 1962, the prototype of the initial Wilga Mark 1 variant made the type's first flight, powered by an existing Polish 220 hp (160 kW) horizontally-opposed engine, the PZL WN-6RB. The subsequent flight test programme with the prototype exposed a number of design faults, the most serious of which was the airframe's excessive weight and a rear view restriction that prevented the crew from easily seeing a towed glider. Accordingly, an airframe review was performed by the design team that resulted in the thorough redevelopment of the aircraft, led by Polish aeronautical engineers Bronisław Żurakowski and Andrzej Frydrychewicz. While the major structural elements and sub-assemblies which had been deemed to have been successful, such as the structure of the wings, were retained from the initial design, the redeveloped aircraft featured a completely new fuselage that was both slimmer and considerably strengthened beyond its prior counterpart; this new airframe also offered an excellent rear view aspect for the crew during glider towing operations, while the side doors were also re-engineered to open upwards for better aero observation or parachute jump sorties. If required, the aircraft could be flown with the doors open. It also featured an air ambulance cabin conversion capability. On 1 August 1963, the revised aircraft, which was designated as the PZL-104 Wilga Mark 2, conducted its first flight. While testing validated the qualities of the Wilga 2's airframe and had proved the aircraft to be a successful design, the WN-6RB engine that powered the model was not fully developed and thus, the aircraft did not enter serial production. In response, the decision was taken to convert the assembly line to instead manufacture the improved Wilga C and Wilga Mark 3 configurations instead. On 30 December 1963, the Wilga C (or Wilga Mark 2 Subvariant C) made its first flight; this variant which was a dedicated export model of the type for Indonesia powered by the imported North American -certified 225 hp (168 kW) horizontally opposed Continental O-470 engine. To address the immaturity of the original WN-6RB engine, the design team decided to adopt an in-production radial engine, the 260 hp (190 kW) Ivchenko AI-14R; furnished with this engine, the aircraft became the PZL-104 Wilga Mark 3 variant, which first flew on 31 December 1965. The new engine was more powerful but it spoilt the previously clean and aerodynamic fuselage lines, originally designed for a flat engine; nonetheless, the new variant was successful. Due in combination to the power of the AI-14R engine and the STOL capability of the airframe, an extraordinary high rate of climb of 11 m/s (2,165 fpm) (maximum) under minimal load was possible. One of a few remaining flaws was that the engine was relatively uneconomical to operate. For further development, design, operational history and variants, click here.
