6.1 Introduction
Clasification Society 2024 - Version 9.40
Statutory Documents - IMO Publications and Documents - Circulars - Maritime Safety Committee - MSC/Circular.616 – Evaluation of Free-Fall Lifeboat Launch Performance – (22 June 1993) - Annex – Evaluation of Free-Fall Lifeboat Launch Performance - Section 6 – Human Tolerance To Acceleration Forces - 6.1 Introduction

6.1 Introduction

  6.1.1 During the launch of a free-fall lifeboat, there is a potential for the occupants to be injured. The potential exists because of acceleration forces exerted upon the occupants when the lifeboat impacts the water. Regulations imposed by the International Maritime Organization, and by most national maritime authorities, require that the potential for injury be considered in the design of free-fall lifeboats and that it be evaluated during prototype certification tests.

  6.1.2 The purpose of this section is to discuss three currently used methods to evaluate the potential for an acceleration field to cause injury. These methods are the square-root-sum-of-the-squares criteria, the dynamic response model, and the Hybrid III human surrogate. The first two methods have been adopted by the International Maritime Organization in resolution A.689(17), "Testing of Lifesaving Appliances". Of these two methods, the dynamic response model is the preferred method because it includes consideration of the magnitude as well as the duration of the acceleration force impulse. It is based upon research conducted at the United States Air Force Aerospace Medical Research Laboratory.

  6.1.3 Human surrogates (dummies) are commonly used in Europe and the United States to study the effects of impact and acceleration on humans, particularly when the impact and acceleration may cause injury. During the past 40 years the complexity and lifelikeness of these dummies has been improving. The Hybrid III is the most recent dummy in this evolutionary process. It is used extensively to evaluate the potential for injury during vehicle collisions and aircraft emergencies.

  6.1.4 When discussing injury, and criteria for acceptable injury, it must be remembered that injury is a spectrum extending from the trivial to the fatal. There is no clear definition of what is an acceptable injury or threshold for injury. A primary consideration, however, when evaluating injury caused by impact and acceleration is the preservation of consciousness. Escape from a stricken ship or offshore platform, or any similar emergency, depends on the maintenance of consciousness. The escape system must therefore, be designed and tested to minimize the risk of head injury. If the head is critically injured, escape may be precluded in situations from which escape would otherwise have been a relatively trivial matter.

  6.1.5 The need to preserve consciousness was dramatically demonstrated in an accident involving a Nimrod aircraft. The airplane departed from an airfield in Scotland with a full crew and a number of passengers. It was flying with sufficient fuel for a normal reconnaissance flight. Shortly after departure the aircraft flew through a flock of birds. All four engines were badly affected by bird ingestion and the aircraft came down in a forest. The pilots made a well executed forced landing into trees. The inertial forces were modest and the rear crew and passengers were able to escape essentially unhurt. Unfortunately the pilots had sustained head injuries in the cockpit and were rendered unconscious. They failed to survive in the ensuing fire. Had they maintained consciousness, they would most likely have survived the accident.

  6.1.6 During a maritime emergency, evacuating the ship or platform is only a part of the survival process. After moving away from imminent danger, many actions are required of the crew to enable them to be safely rescued. These tasks include care for the injured, collection and distribution of water and rations, preservation of a reasonable environment, and sending position notification reports to search and rescue parties. These tasks can be conducted only if the occupants do not sustain injury as a result of the free-fall launch.

  6.1.7 The bases of methods currently' used to evaluate the potential of an acceleration field to cause injury to the occupants in a free-fall lifeboat are discussed in the following parts of this section. The discussion is not intended to be a thorough discourse on human injury resulting from acceleration forces. Rather the discussion is intended to provide the reader with insight into the bases of the methods used as well as their strengths and weaknesses as an indicator of injury potential. Prior to beginning the discussion of injury potential criteria, the co-ordinate systems used when evaluating human tolerance are presented.

Parent topic: Section 6 – Human Tolerance To Acceleration Forces
Copyright 2022 Clasifications Register Group Limited, International Maritime Organization, International Labour Organization or Maritime and Coastguard Agency. All rights reserved. Clasifications Register Group Limited, its affiliates and subsidiaries and their respective officers, employees or agents are, individually and collectively, referred to in this clause as 'Clasifications Register'. Clasifications Register assumes no responsibility and shall not be liable to any person for any loss, damage or expense caused by reliance on the information or advice in this document or howsoever provided, unless that person has signed a contract with the relevant Clasifications Register entity for the provision of this information or advice and in that case any responsibility or liability is exclusively on the terms and conditions set out in that contract.