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.
Heinkel entered two HD 24s (alongside two HD.5) in the German Seeflugwettbewerb seaplane competition in 1926. One of the HD.24 was the third placed - only three aircraft completed the course and completed all the tests in the 11-day competition- leading to orders by the DVS (for 23 aircraft) and the Swedish Navy. The latter aircraft were to be built in Sweden by Svenska Aero based on two pattern aircraft provided by Heinkel. Before the Swedish examples could be delivered, the Swedish Air Force had assumed responsibility for Swedish naval aviation, and so took delivery of the six domestically produced machines, designating them Sk 4.
One HD 24 was exported to China, and another was bought by German explorer Gunther Plüschow who named it Tsingtau and took it on an expedition in 1927–28 to Patagonia and Tierra del Fuego. The journey was recorded in his book and documentary film Silberkondor über Feuerland.
Type 2-seat trainer HD 24a 2-seat seaplane trainer  HD 24b
Engine 1 BMW IV 1 BMW Va
Dimensions Length 8,60 m, height 3,84 m, span 14,2 m, wing area 50,1 m2 Length 9,65  m, height 4,15 m, span 14,2 m, wing area 50,1 m2
Weights Empty 1300 kg flying weight 2150 kg Empty 1500 kg flying weight 2150 kg
Performance Max. speed 180 km/h, range 600 km, service ceiling 4500 m, climb 4,3 m/sec Max. speed 168 km/h, cruising speed 150 km/h, range 600 km, service ceiling 4500 m, climb 4,3 m/sec