(Supplementary Materials for Specific Textbooks--Impact 3)
Exercise 29 (for sharing online): docs, pub
1. Otto Lilienthal ______________________________ (use) gliders for around five years before he crashed on in 1896
2. Before Samuel Langley’s large Aerodrome A crashed while taking off, he ______________________________ (build) smaller machines that flew successfully.
3. Before Alberto Santos-Dumont made the first successful powered flight in Europe, he ______________________________ (win) awards for his flights in balloons..
4. Engineer Frank Whittle ______________________________ (work) on his theories for nine years before he tested his first jet engine in 1937.
5. Before Charles Yeager became the first pilot to travel faster than the speed of sound in 1947, he ______________________________ (fly) for about five years.
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