Royal Canadian Air Force (RCAF) CH-149 Search and Rescue helicopter aircrew operate in dynamic operational conditions including long-duration search and rescue as well as strenuous open-door hoisting activities. During emergencies, civilians and ground crew may be exposed to aircraft noise within the cabin as well as in the external proximity of the aircraft. Due to the demanding nature of search and rescue activities, civilians, aircrew and ground crew may or may not be equipped with properly fitted hearing protection throughout a noise exposure event. The objective of the recent National Research Council (NRC) – Department of National Defence joint investigation was to characterize the noise levels of the CH-149 helicopter cabin and cockpit throughout 48 representative flight and ground conditions.This paper will outline the NRC ground external noise measurement of the CH-149 Cormorant at Comox Canadian Forces Base, January 2017. The contextual performance of the current in-service RCAF hearing protectors whilst exposed to CH-149 aircraft noise is evaluated. Overall sound pressure levels of 109.8 dB(A) were reported in the proximity of the CH-149 Cormorant throughout standard start-up procedures. It was observed that the directivity of the aircraft engine exhaust and auxiliary power unit exhaust significantly affected external sound pressure levels heterogeneously about the aircraft. In accordance with the Canadian Aviation Occupational Health and Safety Regulations, individuals exposed to aircraft external noise, without properly fitted hearing protection, could exceed their recommended cumulative maximum noise exposure dose within 2 minutes 24 seconds for a single 24 hour period. When equipped with a properly fitted SPH5-CF hearing protector, all locations exhibited significantly reduced sound pressure levels with recommended maximum noise exposure limits in excess of 16 hours, for a single 24 hour period.
Canadian Acoustical Association
Canadian Acoustics = Acoustique Canadienne45, no. 3: 152–153.