Heinkel He 51
Designed as a single-seat fighter, reconnaissance seaplane and ground attack aircraft, the Heinkel He 51 started service with the Luftwaffe in March 1935. Blooded in Spain, it was obsolute as a fighter at the start of World War II, but was still operating in the close support role during the invasion of Poland. Large numbers of He 51's were used as advanced trainers and in utility roles during the war years. Source: Fighting Aircraft of World War II Published by Salamander Books.