Flight Operations To Minimize Helicopter Noise

Certain helicopter operating conditions are known to produce higher noise levels than others. Flight test evaluations of various size helicopters are being made to determine which flight conditions cause the higher noise levels. The initial results of these tests have been used to define flight techniques which permit the pilot to avoid generating excessive noise while operating in and out of heliports. With these techniques an operator would be able to use heliports in many areas without violating city noise codes. Test results show that when the helicopter operates without blade slap, the altitude necessary to avoid exceeding noise code limits is one half the altitude necessary with blade slap. If the helicopter flies at the same altitude, the use of quieter operating techniques can reduce the ground area exposed to the same noise level by as much as 75 percent, and can reduce the required distance between a heliport and a noise-sensitive area boundary line by 50 percent. These reductions in noise exposure result in greater use of the helicopter's unique capabilities without exposing noise sensitive areas to high noise levels.