Evaluation of Royal Canadian Air Force CH-149 Hearing Protection Through Example Flight Profiles

Royal Canadian Air Force (RCAF) CH-149 Search and Rescue aircrew are exposed to dynamic and variable flight mission profiles ranging from long range search and rescue to open door hoisting operational activities. Additionally, CH-149 aircrew routinely perform in-flight operations including exiting the aircraft and donning separate safety equipment to address specific situations. The objective of the recent National Research Council measurement campaign was to characterize the noise levels of the CH-149 helicopter cabin and cockpit throughout 48 representative flight conditions including open doors, closed doors, hover, steady level flight and manoeuvres. This paper focusses on the contextual performance of RCAF hearing protectors in the CH-149 cabin noise environment as well as the assessment of the theoretical cumulative maximum noise exposure dose for particular aircrew locations throughout theoretical flight profiles in accordance with the Canadian Aviation Occupational Health and Safety Regulations. Without properly fitted hearing protection, aircrew could exceed the recommended cumulative maximum noise exposure dose within 4 minutes and 48 seconds for a single 24 hour period at the starboard hoist door location. With properly fitted hearing protection, most RCAF hearing protection solutions provide sufficient protection for flight missions in excess of 16 hours for a single 24 hour period. Based on the noise survey and quantitative evaluation results, a number of solutions have been discussed to mitigate the risk of aircrew hearing loss in RCAF Search and Rescue flight missions. Specifically, double hearing protection solutions such as the Gentex HGU-56P-CF pilot helmet in conjunction with communication ear plugs (CEP) have been shown to provide enhanced hearing protection to RCAF CH-149 aircrew to meet Canadian noise regulations.