Viewing page 22 of 83

This transcription has been completed. Contact us with corrections.

-17-

the noise produced at various distances during takeoff, landing, flyover, and hover operations. This study also compares the helicopter noise with that produced by other vehicle movements and with the so-called ambiant [[ambient]] noise level in typical urban and suburban areas. The results permit assessment of the compatibility of helicopter noise with typical land uses near the heliports. Among the helicopter types tested were units similar in weight and power plant characteristics to the S-61 which each of the applicants herein proposes to use. The pertinent conclusions expressed are: 

a. For most helicopters the spread in perceived noise levels for takeoff, landing, flyover, and the hover operations is on the order of 5PNDB or less, a spread in noise levels much less than encountered for fixed-wing aircraft.

b. Piston-powered helicopters are noisier than turbine-powered helicopters of comparable size. No consistent difference in noise levels between single and dual rotor helicopters was noted.

c. Perceived noise levels for turbine powered helicopters show greater changes with size of aircraft than do noise levels for piston-powered helicopters. 

d. For planning purposes, noise radiation from helicopters can be assumed to be non-directional in both vertical and  horizontal planes. 

The Federal Aviation Administration is actively supporting research and development programs designed to: (a) suppress or reduce noise at the source; (b) develop optimized operational procedures to safely minimize noise exposure; (c) develop acceptable yardsticks for evaluating or rating various levels of noise; and (d) to develop guidelines to plan for and control the residual noise inherent in aircraft and helicopter operations.