09/30/2014. Remarks by Johan Visschedijk: "In 1928 the Manfred Weiss company started with the manufacture of aircraft. The first product was the license-built Fokker C.V biplane, manufactured for the LüH (Hungarian AF). Then came the Udet U 12 Flamingo trainer plus eighty copies of the Hungária, a development of the U 12 in five versions.
The Weiss WM-10 Ölyv (Buzzard) two-seat primary trainer biplane made use of Weiss' own 100 hp MW Sport I engine, and the prototype made its first flight in September 1931. In November, the prototype was modified for the installation of the 120 hp MW Sport II engine, and it received an improved landing gear. The type was officially accepted, and in 1933 eight WM-10A machines were delivered.
The last WM-10A airframe was re-engined with the 130 hp MW Sport III engine and became the WM-13. The limited flight range of the WM-10 was overcome by increasing the fuel capacity. Most WM-10s were later converted to WM-13 standard.
Five new airframes were fitted with Siemens Sh.12 engines, designated EM-10, these served in combat units as acrobatics trainers. In 1938, the remaining aircraft received also the Siemens engine, but were still designated WM-10. The type served as primary trainers until 1941, when the three remaining aircraft were handed over to the paramilitary Hungarian aviation organization, where they were used as glider tugs."