when did the missionaries first tried to contact the people?
September 1955.
Operation Auca
The first stage of Operation Auca began in September 1955. 
what is operation auca? An attempt by five Evangelical Christian missionaries to bring Christianity to the Huaorani people. where were these people from? US can you name the five missionaries? Jim Elliot, Nate Saint, Ed McCully, Peter Fleming, and Roger Youderian. can you tell me something more about the first person? born in Portland, Oregon, to Fred and Clara Elliot. Fred was of Scottish heritage; his grandparents were the first of his family to settle in North America. what about the second person? Born in 1923, when he was seven he took his first plane ride with his brother Sam, who would eventually become a commercial pilot for American Airlines.
wiki:15820608
Operation Auca [SEP] Initial contact
The first stage of Operation Auca began in September 1955. Saint, McCully, Elliot, and fellow missionary Johnny Keenan decided to initiate contact with the Huaorani and began periodically searching for them by air. By the end of the month, they had identified several clearings in the jungle. Meanwhile, Elliot learned several phrases in the language of the Huaorani from Dayuma, a young Huaorani woman who had left her society and become friends with Rachel Saint, a missionary and the sister of Nate Saint. The missionaries hoped that by regularly giving gifts to the Huaorani and attempting to communicate with them in their language, they would be able to win them over as friends.