While the advantages of helicopters have encouraged their use, they also have contributed to hazards. The ability to operate low to the ground and in confined areas increases the probability of loss of control caused by dynamic rollover; collision with wires, trees and other objects; and loss of situational awareness resulting from brownout (blowing dust) or whiteout (blowing snow). Frequent takeoffs and landings at unprepared landing sites present an additional, substantial hazard.
Historically, helicopter accident rates in the United States have been as high as 38.4 accidents per 100,000 flight hours — for the period from 1963 through 1970. In the most recent decade (2001–2010), accident rates stabilized and declined to 5.7 per 100,000 flight hours — down from 7.8 per 100,000 flight hours recorded in 1991–2000 — due in large part to improvements in pilot training, maintenance and overall helicopter design.1
At the start …
