1 Discard any hammer with mushroomed or chipped face or with cracks in the claw or eye sections. 2  Wear safety glasses or goggles, or a face shield (with safety glasses or goggles).  Strike a hammer blow squarely with the striking face parallel to the surface being struck.
The first jet airplane was the Heinkel He 178 made in Germany in 1939, right before the outbreak of World War II .
Designed as a single-seat long-range fighter plane and fighter-bomber, the P-51 Mustang was produced by North American Aviation. The plane's first test flight was on October 26, 1940. The first production models were used in operations conducted by the British Royal Air Force.