A helicopter is a wonderful but expensive machine. With it, we save lives. We do that by moving Bible translators into places they can’t get with fixed wing aircraft or wheeled vehicles to bring the Word of God to people so that they can be saved. Eternal life is the greatest gift we can get from God. God, in His great wisdom, has tasked us, His children, with sharing the Good News of Jesus Christ with people so that they can believe in Him and gain eternal life with Him.
Of course, we also save lives with this machine in the more common sense, too. SIL Aviation recently made national news by saving the life of a pregnant mother in distress. It is good to show Jesus’ compassion in practical ways. See http://www.thenational.com.pg/100207/nation12.htm for that article.
So, how do we pay for this expensive machine? With a combination of donations and commercial work done with that machine in between Bible translation and life-saving runs.