Simplify the following text for a Grade 12 native English-speaking person.
Original: Before the development of powered helicopters in the mid 20th century , autogyro pioneer Juan de la Cierva researched and developed many of the fundamentals of the rotor .
Simplified: Before the development of powered helicopters in the mid 20th century , autogyro pioneer Juan de la Cierva researched and developed many of the basics of the rotor .