Complex sentence: One prototype unit was produced and almost completed in March 1954 (Showa 29), but was damaged in July 1954 during tie-down testing, futher development was cancelled before the aircraft was flown.
Split into simpler sentences: One prototype unit was produced and almost completed in March 1954 (Showa 29), but was damaged in July 1954 during tie-down testing. Futher development was cancelled before the aircraft was flown.