Survival suit volume reduction associated with immersion: implications for buoyancy estimation in offshore workers of different size

Abstract

Rationale: It is currently unknown how body size affects buoyancy in submerged helicopter escape. Method: Eight healthy males aged 39.6 ± 12.6 year (mean ± SD) with BMI 22.0–40.0 kg m^?2 wearing a standard survival (‘dry’) suit undertook a normal venting manoeuvre and underwent 3D scanning to assess body volume (wearing the suit) before and after immersion in a swimming pool. Results: Immersion-induced volume loss averaged 14.4 ± 5.4 l, decreased with increasing dry density (mass volume^?1) and theoretical buoyant force in 588 UK offshore workers was found to be 264 ± 46 and 232 ± 60 N using linear and power functions, respectively. Both approaches revealed heavier workers to have greater buoyant force. Discussion: While a larger sample may yield a more accurate buoyancy prediction, this study shows heavier workers are likely to have greater buoyancy. Without free-swimming capability to overcome such buoyancy, some individuals may possibly exceed the safe limit to enable escape from a submerged helicopter.

Practitioner Summary: Air expulsion reduced total body volume of survival-suited volunteers following immersion by an amount inversely proportional to body size. When applied to 588 offshore workers, the predicted air loss suggested buoyant force to be greatest in the heaviest individuals, which may impede their ability to exit a submerged helicopter.     

The effect of transportation suit induced heat stress on helicopter underwater escape preparation and task performance

Although essential in an emergency such as a helicopter ditching, mandatory survival suits worn by civilian personnel may lead to heat strain during a normal flight. To explore the possibility that wearing a helicopter transportation suit impairs emergency performance, 11 individuals completed underwater escape procedures immediately following a pre-recorded emergency announcement (randomly played between 50 and 90 min) in two ambient temperature conditions (Thermoneutral = 21 °C and Hot = 34 °C). Mean skin and rectal temperatures were recorded throughout the trials, while situation awareness and thermal sensation/comfort were recorded on completion of trials. Results indicate that although mean skin and rectal temperatures were significantly higher at the end of both trials, escape procedures were not impaired. It can therefore be concluded that although conditions inside an offshore transport helicopter are perceived as being hot and uncomfortable, no deficits in escape performance should be expected in the first 90 min of flight.     

Test of a quick-don wet immersion suit for off-shore use

Tests of “Spacetime” Survival Coverall suits and the associated gloves and boots of the ensemble were carried out on six men. Four men maintained their rectal temperature above 36°C for six hours in a bath of circulating water at 12°C. Two men had to be withdrawn from the bath because they reached a rectal temperature of 35.5°C, the ethical withdrawal criterion, before the six-hour period had elapsed. Linear regression of rectal temperature versus time during the terminal part of the exposure was carried out for all men. One of the subjects who was withdrawn would almost certainly have had a rectal temperature above 34°C at the end of six hours had he remained in the bath. The other subject would have had a rectal temperature classifiable as “incipient death” (30°C). The relatively rapid fall in rectal temperatures in two subjects did not appear to relate directly to body size, but leakage may have been a contributing factor. Comparison with data in the literature indicates that the immersion suit is advantageous, but separate experimentation would have to be carried out to determine quantitatively how valuable it is in extending the survival time of men immersed in cold water in comparison with other suits on the market.     

Helicopter pilot suits for offshore application. A survey of thermal comfort and ergonomic design

The objective of this study was to determine the existing problems associated with helicopter pilot survival suits currently in use. A survey was conducted of helicopter pilots from both Canadian commercial and military disciplines. Pilots commented on eight different types of survival suits. Reduced thermal comfort as well as lack of ventilation were the two most common criticisms of the pilot suits. The 'greenhouse' effect, common to helicopter cockpits, results in hot working ambients both in summer and winter. The air cooling mechanisms employed in summer may cause a 'chilling' effect following an on-ground stand-by where cockpit temperatures may reach 40 degrees C. Thermal stress may also be induced with high cockpit temperatures caused by the sun's radiation in winter and summer. Suit design was another area considered. 72% and 86% of military and commercial pilots respectively felt their freedom of movement was hindered by their survival suits. Certain designs were considered more hazardous than others with regard to clips and hooks catching switches on the control panel. Difficulty in donning suits appeared to be a universal problem irrespective of type of suit used. Lack of comfort and movement in addition to thermal stress may lead to reduced time to fatigue and, thus, occurrence of errors and accidents. The results of this survey reflect the inadequacies of the helicopter pilot survival suits presently in use. It is suggested that evaluation of these suits be made on the basis of their ventilation capabilities, ergonomic design and thermal properties in a variety of ambient environments.     

Kinematic compatibility between the body and a mock spacesuit during basic upper body motions

In this study, a novel conceptual method was tested to study the kinematic mismatch between the body motion of an occupant with respect to a rigid suit. It was hypothesized that differences between body and suit motion would require extra body movement to achieve the desired suit motion. To quantify the mismatch in kinematics, mock upper body suits with an open structure were used in conjunction with a marker-based motion capture system. A 3D motion modeling software was used to determine the range of motion of the suit and body segments of nine participants performing seven basic arm and trunk motions. In general, range of motion of the body segment was found to be higher than the corresponding suit segment range of motion. Differences in range of motion of up to 21.3% were found between corresponding body and suit segments, and significance was found in five of the seven motions.     

Exercise and the cold

The generation of heat by the human body has been likened to that of a furnace. In response to winter conditions or prolonged immersion in cold water, heat may be lost from the body more quickly than it is produced leading to hypothermia. Various factors, environmental and individual, predispose a person to hypothermia when walking on dry land or during cold water immersion. Retention of the insulating properties of the clothing worn is of crucial importance in protecting against cold injury both on land and in water. Anthropometric characteristics and behavioural and physiological responses also influence the probability of survival under these conditions. Practical recommendations for behaviour that will enhance survival during prolonged exposure to cold on land or to immersion in cold water are considered.     

Exercise and the cold

The generation of heat by the human body has been likened to that of a furnace. In response to winter conditions or prolonged immersion in cold water, heat may be lost from the body more quickly than it is produced leading to hypothermia. Various factors, environmental and individual, predispose a person to hypothermia when walking on dry land or during cold water immersion. Retention of the insulating properties of the clothing worn is of crucial importance in protecting against cold injury both on land and in water. Anthropometric characteristics and behavioural and physiological responses also influence the probability of survival under these conditions. Practical recommendations for behaviour that will enhance survival during prolonged exposure to cold on land or to immersion in cold water are considered.     

民机飞行机组应急逃生设计混合现实仿真系统

开展民机飞行机组应急逃生仿真旨在飞机研制早期发现飞行机组逃生口设计的潜在问题,确保飞行机组成员的人身安全.提出了一种民机飞行机组应急逃生混合现实仿真系统设计方案,进行了系统搭建与实验验证.针对系统中人体虚实匹配的关键问题,提出一种光-惯混合追踪的全身人体运动捕捉方法,结合基于Kinect2图像识别的人体关键尺寸快速匹配...     

Aircraft warning systems: application of model-based reasoning techniques

The warning systems fitted to the current generation of civil air transport aircraft represent a significant advance on earlier technologies. One important outcome of this development has been the centralized alerting and monitoring systems that present information directly to pilots via multifunction displays. Despite these advances, there are still areas where substantial improvements might be made on current systems. In this paper a brief review is provided of the design issues associated with current aircraft warning systems, and the potential benefits of an 'intelligent' warning system are identified. This system would be capable of monitoring and interpreting data from aircraft systems and flight operational conditions, and in the event of failures and abnormal conditions, would provide the crew with a high-level interpretation of the malfunction. In addition, it would generate appropriate crew actions and prediction of future trends. The use of a model-based reasoning approach to this task is outlined and discussed in relation to some specific aspects of interface design.     

Developing guidance on the safe use of air-fed suits in the nuclear industry

Air-fed suits are used for protection from radioactive particulate contamination. Managing air-fed suit operations safely and efficiently involves complex interactions between people, personal protective equipment and work systems. The nuclear industry and the Office for Nuclear Regulation identified the need for clear guidance on the non-radiological aspects of their use, especially the management of ergonomic and physiological issues, including thermal stress. We describe the key principles that need to be considered when managing the ergonomic and physiological risks from air-fed suits, and how we can tailor these to different applications. The information gathered in our research confirmed that the safety of operations employing air-fed suits will depend on a unified strategic approach to design and usage. Detailed implementation of this strategy can be adjusted according to specific tasks and hazards. We explain that the balance between engineering and behavioural safety issues for air-fed suits is different for operational and decommissioning activities.