Barker and his copilot, Capt. Jason Turner, went through their preflight checks. All high-altitude missions present a challenge, Barker explained. Thin mountain air reduces the efficiency of gas turbine engines, and updrafts and downdrafts around mountains make for turbulent flying. Your margin of error up there is greatly reduced because you're flying at about 57 percent of available power.
Landing can be dangerous, too.
During a training mission about two years ago, one of the HART helicopters landed on what turned out to be a snow-covered crevasse and was forced to make an emergency takeoff as it started falling in. Pilots work together to maintain control of the aircraft, and crew members monitor oxygen consumption as closely as fuel levels. Team members keep an eye on each other, watching for signs of oxygen deprivation that could lead to fatal mistakes. All the while, a second Chinook crew keeps watch over the rescue chopper, ready to swoop in if an emergency arises. We pick the crews carefully and train meticulously.