In January, the country's northernmost settlement, Mohe, is experiencing many extremely cold days. Both land and sky are fiercely frigid.

Tears freeze before they can fall. People's eyelashes gather frost after just a couple of minutes outside. Not even thick cotton shoes can seal out the numbing bite of these extreme temperatures.

This weather makes the area ideal for test flying helicopters to see how they perform in such complex conditions — especially at very high latitudes, in extremely low temperatures.

An Auspicious Bird AC313A helicopter and a high-latitude test-flight team recently traveled thousands of kilometers from Jingdezhen, Jiangxi province, in eastern China to Mohe in the far north. It was the first time an AC313A attempted to navigate such conditions, and marked advances toward its research and certification. Objectives included airspeed, rotor speed, environmental-control system testing, hovering, level and upward flights, and engine ignition tests.

The meteorological requirements for high-latitude test flights are incredibly demanding. To seize the lowest-temperature conditions, technicians, and maintenance and test-flight personnel set out around 5 or 6 every morning.