Such was its value that the Bu 131 remained in global service well into the 1960s and private ownership has kept the design alive at many air shows around the world. Total production reached into the thousands before the end of its run.
Initial models were designated Bu 131A and these were followed by the improved Bu 131 (Hirth HM 504A-2 engines). The Bu 131C was a one-off test plane carrying the Blackburn "Cirrus Minor" engine of 90 horsepower. The two aforementioned production models were the primary marks to carry the Bucker name.
The Bu 131B featured an overall length of 21.7 feet with a wingspan of 24.2 feet and a height of 7.5 feet. Empty weight was 840lb against an MTOW of 1,500lb. Power was from a single Hirth HM 504 4-cylinder inverted inline piston engine developing 100 horsepower and driving a two-bladed propeller unit at the nose. Performance included a maximum speed of 115 miles per hour, a cruise speed of 110 miles per hour, a range out to 390 miles and a service ceiling of 13,300 feet. Rate-of-climb was listed at 6,600 feet.
Beyond Aero's pretime production of the Tatra T-131 was the wartime C-4 production standard for Germany, also by Aero to the Bucker Bu 131B standard. The post-war form became the Aero C-104 carrying the Walter Minor 4-III engine. About 260 were built to this standard.
As mentioned, the Japanese Empire though enough of the German biplane to order local versions to be built for its Army and Navy services. This involved the Nippon Kokusai Ki-86A Type 4 and Ki-86B Type 4 for use as primary trainers. The Ki-86A model carried the Hitachi Ha-47 engine and the Ki-86B was developed with a wooden airframe owing largely to a shortage of metal during World War 2. The Kyushu K9W1 "Momiji" Navy Type 2 Trainer Model 11 was the main production version for the Imperial Japanese Navy (IJN). These were given the Hitachi GK4A "Hatsukaze 11" series engine.
Modern versions of the Bucker Bu 131 are found under the BP 131 designation. Poland developed the SSH T-131P and built four with Walter Minor 4-III engines beginning in 1994. This then evolved to become the production-minded SSH T-131PA of 1995 with its LOM M332AK engine.
Beyond the mentioned countries, the Bu 131, in one form or another, made its way into the inventories of a myriad of nations ranging from Croatia and Greece to The Netherlands and South Africa.
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