High Quality Content by WIKIPEDIA articles! The Heinkel HD 24 was a training seaplane developed in Germany in the late 1920s. It was a conventional single-bay biplane with equal-span, unstaggered wings. The fuselage was braced to both the upper and lower wings with a number of struts on its sides, in addition to the normal cabane struts. The pilot and instructor sat in tandem, open cockpits, and the undercarriage consisted of twin pontoons, although this could be readily exchanged for wheels or skis.