The maximum evaporative potential of constant wear immersion suits influences the risk of excessive heat strain for helicopter aircrew

Abstract

The heat exchange properties of aircrew clothing including a Constant Wear Immersion Suit (CWIS), and the environmental conditions in which heat strain would impair operational performance, were investigated. The maximum evaporative potential (im/clo) of six clothing ensembles (three with a flight suit (FLY) and three with a CWIS) of varying undergarment layers were measured with a heated sweating manikin. Biophysical modelling estimated the environmental conditions in which body core temperature would elevate above 38.0°C during routine flight. The im/clo was reduced with additional undergarment layers, and was more restricted in CWIS compared to FLY ensembles. A significant linear relationship (r2 = 0.98, P<0.001) was observed between im/clo and the highest wet-bulb globe temperature in which the flight scenario could be completed without body core temperature exceeding 38.0°C. These findings provide a valuable tool for clothing manufacturers and mission planners for the development and selection of CWIS’s for aircrew.

Occupational Health Challenges for Aviation Workers Amid the Changing Climate: A Narrative Review

“…As a result, pilots may suffer declines in cognitive performances, including vigilance, reaction time, and decision-making, which are critical for flight safety [ 10 , 11 ]. Among aviation personnel, military [ 10 ] and helicopter [ 11 , 12 , 15 ] pilots appear especially vulnerable to heat strain due to frequent exposure to extreme conditions. For example, fighter pilots routinely experience intense heat and humidity during pre-flight duties, low-altitude missions, and combat readiness tasks [ 10 ].…”

“…This is attributed to the inflatable counter-pressure vest designed to facilitate positive pressure breathing, which, while crucial for maintaining G-tolerance, exacerbates the heat stress experienced during flight [ 16 ]. Helicopter pilots represent another occupational group that is distinctly vulnerable to heat stress due to the unique conditions within their work environment [ 11 , 12 , 15 ]. In particular, the cockpit’s glass canopy design can exacerbate heat load, most notably in regions with high ambient temperatures, potentially compromising pilot performance [ 11 ].…”

“…In particular, the cockpit’s glass canopy design can exacerbate heat load, most notably in regions with high ambient temperatures, potentially compromising pilot performance [ 11 ]. This issue becomes especially pronounced during ground standby operations, where the lack of airflow that would normally occur during flight allows cockpit temperatures to rise approximately 20°C above the surrounding environment [ 11 , 12 , 15 ]. Mirroring findings among military pilots [ 10 ], research indicates that helicopter pilots suffering from heat stress may experience diminished performance and compromised decision-making abilities [ 11 ].…”