Stampe et Vertongen RSV . 26 The Stampe et Vertongen RSV . 26 / 140 , RSV . 26 / 180 , and RSV . 26 Lynx were a family of training biplanes designed by Alfred Renard and built by Stampe et Vertongen in Belgium in the 1920s . They were produced as a response to a requirement by the Belgian Air Force , which became their biggest user , although private owners also bought a small number . The air force requirement was for a two - seat aircraft with aerobatic capabilities that could provide a next stage for students who had completed basic training on the RSV . 32 . Stampe et Vertongen contracted Alfred Renard to provide a design , and for the sake of expediency , suggested that he submit a revision of his RSV . 32 rather than create an entirely new aircraft . The resulting RSV . 26 was , like its predecessor , a conventional single - bay biplane with unstaggered wings of equal span . However , the fuselage was reinforced to accommodate engines of up to 150 kW ( 200 hp ) , the undercarriage legs were fitted with thicker bungee cord s , and the pilot ' s and instructor ' s seats were now placed in two separate cockpits in tandem . The RSV . 26 had wings of smaller span and area than the RSV . 32 , that were , despite appearances , a complete redesign of the older wing . The shorter span allowed for the use of a more powerful engine and provided greater speed and maneuverability while not adversely affecting rate of climb . Power was provided by a 100 - kW ( 140 - hp ) Minerva engine in the nose , driving a two - bladed propeller . The prototype made its public début on 26 June 1926 at a rally at Ostende . The air force evaluated the type and judged it suitable . However , the new Minerva engines cost 50 , 000 BEF while the government could purchase war - surplus Hispano - Suiza engines from France for only 6 , 500 BEF . Consequently , Stampe et Vertongen was asked to adapt the design to the alternative powerplant . The firm was reluctant to accommodate the change , as the Hispano - Suiza engines and cooling systems were heavier than their Minerva counterparts , and were not only obsolete technology but were already used and worn - out . Nevertheless , the contract was too valuable to turn down , and Renard altered the design accordingly . The biggest change was to move the upper wing forward , staggering it with the lower wing to preserve the aircraft ' s centre of gravity . The change also provided improved access to and visibility from the forward cockpit . The air force purchased the RSV . 26 in this form , now designated RSV . 26 / 180 to reflect its more powerful engine . In service , it was known as the RSV " décalé " or 26 " décalé " ( " staggered " in French ) . The start of the RSV . 26 / 180 ' s career was troubled by a handling problem that made three - point landings almost impossible . The cause was traced back to the factory : an error in making the templates for the wing ribs resulted in all the wings having the wrong profile . Stampe et Vertongen rectified this at the firm ' s own expense . Other problems with the type were due to the second - hand engines , which suffered continual mechanical breakdowns and by the early 1930s had contributed to a long list of accidents . To investigate a solution to the ongoing situation , the air force returned the RSV . 26 / 140 prototype to the factory to be fitted with an Armstrong Siddeley Lynx engine . When the resulting modification proved successful , the air force had ten of its RSV . 26 / 180s re - engined the same way . With the new engines fitted , they were redesignated RSV . 26 / 215 or RSV . 26 Lynx . Following their military careers , ten RSV . 26 / 180s were sold to private owners in 1936 . Histories of Stampe et Vertongen differ on the number of RSV . 26 / 140s and RSV . 26 / 180s produced , with figures as disparate as 17 and 98 published .