The ability of the helicopter to hover and therefore to take-off and land in confined areas has proven to be of significant value in an increasing range of applications. Rotorcraft have now established a significant role for specialist aeronautical applications both in the civil and military field.
Figure 1(a) shows a graph of the increase of helicopter usage in the civil market. To the traditional roles of point to point transport and special purpose public service operations has been added a massive increase in energy related use, particularly for off-shore oil exploration. Present fleet growth rate in the civil area is about 15% p.a. There is no sign that this demand will abate. There has also been a substantial increase in helicopter use on military operations, as illustrated in Fig. 1(b). Helicopters now account for between 40–50% of all service aircraft (excluding training and liaison) in both the United States and Britain. The flexibility offered by the helicopter has been critical in its tactical value for land operations. The ability of the helicopter to operate from small ships at sea in all weathers, and at night, has provided it with a unique role in naval applications. In Britain over 80% of naval aircraft are now helicopters.