The manufacturing of the first NA 40 Bongo helicopter which served as a technology demonstrator started in 1994. Functional, land and fatigue tests followed from 1997 under CAA CZ supervision. The tethered hovering flight program started in 1998 and proved stabile hovering ability and full controlability of the helicopter. During the programm the helicopter has flown more that 70 flight hours; the longest flights lasted 45 minutes. The experiences received during test flights were reflected in design improvements and development of folloving types.