Section 1 – Introduction
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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 1 – Introduction

Section 1 – Introduction

  1.1 The free-fall lifeboat is quickly becoming a common lifesaving appliance on seagoing vessels and offshore facilities. It represents an apparent improvement in safety over conventional lifeboat systems. Because of the apparent increase in safety, most maritime regulatory authorities have accepted the free-fall concept and have prepared design and certification criteria for these lifeboats.

  1.2 Many life threatening accidents have occurred with conventional lifeboat systems. A majority of the accidents occurred during launch and after lowering into rough seas and high wind. During launch, the lifeboat may impact the sides of the distressed vessel, become severely damaged, and the occupants may fall into the sea suffering injury and even death. Launching the lifeboats may be impossible if the parent vessel is listing significantly or if the falls become tangled. After the lifeboat is in the water, it may be unable to move away from the distressed vessel because high seas and wind continually return the lifeboat to the vessel or because of a malfunction in the propulsion system. This situation is even more dangerous during a fire or when the potential for an explosion exists.

  1.3 The risks with conventional lifeboat systems have been substantially reduced by 'the free-fall concept which allows the lifeboat to fall freely into the sea. The free-fall provides kinetic energy used to propel the lifeboat away from the distressed vessel during and after water entry. The lifeboat moves away from danger even if the engine does not operate.

  1.4 Today, free-fall lifeboats are manufactured in several countries by many manufacturers. The materials used in the manufacture of the lifeboats include fiberglass, steel, and aluminum. These lifeboats are being actively marketed and are quickly gaining universal acceptance. Currently, free-fall lifeboats are in use on cargo ships, tankers, semi-submersible drilling platforms, and fixed production platforms. The heights of free fall range from approximately six meters on smaller ships to over 30 meters on drilling platform. Although a free-fall lifeboat has never been used in a maritime evacuation, over 15,000 people have been launched in free-fall lifeboats during training exercises. There has not been a reported injury during these training exercises. A free-fall lifeboat has been used in two separate maritime incidents. In one case, the free-fall lifeboat was used to rescue a crewman who had fallen overboard. In the other incident, a free-fall lifeboat was used to rescue the crew of a capsized fishing vessel. The free-fall lifeboats were successfully launched and recovered in a seaway in both of these incidents (Hatecke, 1991).

  1.5 The purpose of this report is to provide a conceptual understanding of the launch behavior of free-fall lifeboats and of the methods used to evaluate the launch behavior. Mathematical formulations have been included, where appropriate, to show the basis and limitations of the analysis procedures as well as to provide some insight into the fundamental behavior of the lifeboat. In general, mathematics is used in the discussion only to the extent necessary to explain a physical concept or the limitations of an analysis procedure. All pertinent results are summarized in tables or are reduced to easily used equations. As such, a complete understanding of the mathematics involved is not necessary for this circular to be understandable.

  1.6 It is intended that this document be a reference for maritime authorities and manufacturers when questions regarding launch behavior arise. Presented in Section 2 is a discussion of issues pertinent to the certification of free-fall lifeboats. A general discussion of the launch behavior of free-fall lifeboats is presented in Section 3. Because scale models are often used to evaluate lifeboat performance, criteria 'for developing properly scale models are presented in Section 4. Presented in Section 5 is a general discussion of considerations during the measurement of acceleration forces in lifeboats. Various methods that can be used to infer occupant safety during the launch of a free-fall lifeboat are discussed in Section 6. Included in appendices to this report are a suggested free-fall lifeboat prototype test program and a sample summary evaluation form that inspectors can use during free-fall lifeboat prototype tests.

Parent topic: Annex – Evaluation of Free-Fall Lifeboat Launch Performance
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