The flying accuracy of Helicopters may be adversely affected by changing natural conditions such as wind, air density, altitude/temperature, humidity, and time of day. Manmade conditions such as weight, weight distribution, center of gravity and/or the discharge of pyrotechnics in close proximity disturbing air ow around the tail rotor, can also affect the ability of the helicopter to fly. Special precautions should be taken to ensure safety when working in any extreme temperatures or terrain, e.g., mountains and deserts.