THERMAL STRESS

2 PLAN Introduction Factors Causing Heat Stress Effects of Heat Stress in Aviators Factors Affecting Heat Tolerance Heat Strain Parameters & Indices Alleviation of Thermal Stress in Aviators Conclusion MI ROOM - ICGAS DAMAN

ENVIRONMENTAL FACTORS AFFECTING AIRCREW HEALTH VIBRATION NOISE CIRCADIAN DYSRHYTHMIA RADIATION THERMAL STRESS HYPOXIA DECOMPRESSION ACCELERATION 3 MI ROOM - ICGAS DAMAN

INTRODUCTION Optimum physical comfort of aircrew is important to ensure ideal man-machine combination in flying Thermal stress in aviators can be of two types: –Heat stress –Cold stress 4 MI ROOM - ICGAS DAMAN

Heat stress arises from an imbalance between a pilot’s metabolic heat production and his heat exchange with the environment HEAT STRESS 5 MI ROOM - ICGAS DAMAN

FACTORS CAUSING HEAT STRESS Climatic Factors  Air Temperature - affects convection  Humidity - affects evaporation  Air Movement - affects convection & evaporation  Radiant Heat - affects radiation exchange with body 6MI ROOM - ICGAS DAMAN

FACTORS CAUSING HEAT STRESS Aircraft Factors  Aerodynamic Heating - due to friction between a/c & air  Electrical Heating - due to a/c instrument & equipment  Green House Effect - due to solar radiation 7 MI ROOM - ICGAS DAMAN

FACTORS CAUSING HEAT STRESS Aircrew Factors  Metabolic Heat - increases during flying ops  Flying Clothing - in multiple layers causing interference with evaporative & non-evaporative heat exchange  Acclimatisation 8MI ROOM - ICGAS DAMAN

AIRCREW Psychomotor parameters –Memory registration and recall –Effect on attention and vigilance –Increase in reaction time; reasoning & decision making –Manual dexterity Physiological parameters –Profuse sweating causing dehydration –Reduced G tolerance –Aggravate hypoxia FAILURES EFFECT OF HEAT ON AVIATORS 9 MI ROOM - ICGAS DAMAN

FACTORS AFFECTING HEAT TOLERANCE Obesity Lack of physical fitness Fatigue Lack of sleep Dehydration Fever & Illness Lack of acclimatisation 10MI ROOM - ICGAS DAMAN

ALLEVIATION OF THERMAL STRESS 11MI ROOM - ICGAS DAMAN

ALLEVIATION OF THERMAL STRESS Station Policies Pre-Flight Solution In-Flight Solution Personal Cooling Systems 12MI ROOM - ICGAS DAMAN

STATION POLICIES Ergonomics in design of flying station Provision of air-conditioned building & transport Aircraft to be parked in shade or use canopy cover Use of mobile cold air units Providing small fan inside cockpit with rubber blades 13MI ROOM - ICGAS DAMAN

Better planning of sorties Rotation of aircrew for sorties Adequate interval in b/w sorties Use of Heat Stress Indices to assess flying conditions: –Wet Bulb Globe Temperature (WBGT): Universally accepted index to assess heat stress in warm climate –Fighter Index Of Thermal Stress (FITS): Useful index in certain fighter aircraft during low level flying STATION POLICIES 14MI ROOM - ICGAS DAMAN

Physical fitness Good work-rest schedule with adequate rest periods Adequate hydration but NO alcohol Balance diet before sorties Appropriate clothing Heat acclimatisation PRE-FLIGHT SOLUTIONS – AIRCREW 15MI ROOM - ICGAS DAMAN

INFLIGHT SOLUTION Standby time on tarmac should be minimized Avoid low-level high performance flying during day-time Use of efficient Cabin Conditioning System 16MI ROOM - ICGAS DAMAN

CABIN CONDITIONING SYSTEM Effective way to combat heat stress Limitations: –Increases aircraft weight & reduces engine performance –Cabin noise –Localized cold/ hot spots –Ineffective at low altitudes 17MI ROOM - ICGAS DAMAN

PERSONAL COOLING SYSTEMS Cooling garments worn next to skin which permit flow of fluids to remove heat –Air-cooled Garments –Liquid-cooled Garments –Gel-cooled Vests 18MI ROOM - ICGAS DAMAN

Air Ventilated Suit –Dry cool air is passed at pressure –Consists of piped lining inside clothing material which allows evaporative heat loss –Susceptible to contamination PERSONAL CLOTHING 19MI ROOM - ICGAS DAMAN

Liquid Conditioned Suits –Water through piped lining in contact with skin –More effective –Difficult to maintain PERSONAL CLOTHING 20MI ROOM - ICGAS DAMAN

Gel Cooled Vests –New concept involving Flexum material –Pre-refrigerated before use PERSONAL CLOTHING 21MI ROOM - ICGAS DAMAN

TAKE HOME MESSAGE Know your body’s limitations Follow station policy Plan your sortie in cool hours of the day Adequate fluid intake Do not exert prior to sortie Adequate interval and rest between sorties 22MI ROOM - ICGAS DAMAN

CONCLUSION Heat stress cannot be eliminated completely and is still a problem in military flying Simple precautionary measures can considerably reduce heat strain to acceptable levels Proper thermal control helps a long way in success of missions & enhances flight safety 23MI ROOM - ICGAS DAMAN

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