The scorching heat plaguing Americans in remote national parks is also causing emergency helicopter flights to be grounded, as helicopters are unable to operate in temperatures surpassing 120 degrees, USA TODAY reports. In Death Valley National Park, a motorcycle rider died of heat exposure and another was hospitalized for severe heat illness, after a group of bikers rode through the park July 6. But if visitors are incapacitated by heat-related illness and need hospitalization, rescue helicopters may not be available. As the USA Today graphic illustrates, high temperatures affect air density and helicopter blades struggle in thinner, hotter air.
Certainly, helicopters are fast, versatile aircraft. Rescuers use them because they quickly reach injured people in difficult situations and carry them to hospitals. But helicopters and airplanes operate in an environmental flight envelope – limits that include temperature, altitude, airspeed and load weight – that determine whether the aircraft can safely fly. High temperatures affect air density. When air molecules heat up, they move faster and apart, which puts more space between them. As helicopter blades spin, the airflow beneath the blades produces lift to counteract gravity, according to Cadence Design Systems. In thin air, blades produce less lift, which means more difficulty in taking off and maneuvering. Heat also affects helicopter engines, which produce less power while taking in less dense air. Park rangers are warning visitors against taking risks in high temperatures.