I was away on a scout tramp with approx 53 kids and 23 adult leaders. We were walking down a narrow river bed 250 meters from camp a fellow leader was on a slippery hill and lost his footing he slipped and smashed his knee on a rock and landed chest first on a tree root. when we managed to get him on the flat he was struggling to breath and was delirious. After patching his leg up we managed to carry him to camp. Using a Mountain Radio, we called St. Johns after telling them all the info including our coordinates and they sent the Westpac rescue helicopter. They had trouble finding us so the pilot asked us to activate a Beacon. Within 30 minutes the chopper was there. The crewman thanked me and said the beacon made their job so much easier. He was taken to the hospital and is now at home on the mend.