The FAA has issued a notice of proposed rulemaking (NPRM) aimed at reducing noise generated by new helicopters and supplemental type certificate (STC) modifications for new helicopters certified under Part 36 (noise standards) of the federal aviation regulations (FARs).
The proposed rule would impose standards already adopted by the International Civil Aviation Organization (ICAO, Annex 16, Vol. 1, Chapters 8 & 11, Amendment 7). The new “Stage 3” standards would apply to all new helicopters in all phases of flight and be measured in effective perceived noise level in decibels (EPNdB) for helicopters weighing more than 3,125 pounds. The new noise standards are based on a logarithmic formula based on maximum weights of 176,370 pounds down to 3,125 pounds. (The maximum weight figure is high in relation to current helicopter technology. The Russian Mi-26, for example, is large by modern standards and has an mtow of about 123,000 pounds, and the Sikorsky CH-53E has an mtow of 73,500 pounds.) Helicopters weighing less than 3,125 pounds would have a maximum noise limit of 82 decibels SEL (sound exposure level/noise meter). The formula sets a noise ceiling for helicopters that weigh 176,370 pounds or more during takeoff, flyover and approach. For the maximum weight value that equates to EPNdBs of 106, 104 and 109, respectively for these flight phases. The noise formula decreases permissible noise at a rate of 3.01 EPNdB per halving of helicopter maximum weight to a floor of EPNdBs of 86, 84 and 89, respectively for helicopters weighing more than 3,125 pounds.
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