Assertion: glider's flight | /r/HasProperty | tested on model aircraft
Facets:
value: in the 1970s
type: TEMPORAL
Source sentences:
text: Electric-flight was tested on model aircraft in the 1970s, but its high cost prevented widespread adoption until the early 1990s, when falling costs of motors, control systems and, crucially, more practical battery and electric power technologies, with the increasing adoption of brushless motors powered with better battery chemistries and controlled with an electronic speed control in place of a throttle servo came on the market.