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 .
Between 1899 and 1905, the Wright brothers conducted a program of aeronautical research and experimentation that led to the first successful powered airplane in 1903 and a refined, practical flying machine two years later.