To make recommendations which would contribute to improving safety at sea.
The Study found that a root cause of many of the accidents was the over-complicated design of the lifeboat launch system and its component parts, which in turn required extensive training to operate. It also found that personnel incurred many risks. It identified that training, repair and maintenance procedures fell short of what was necessary, and that there were extensive problems with manufacture, construction, maintenance and operation.
It recommends that IMO undertakes a study of the present value, need, and desirability of lifeboats. Such a study should embrace all reported incidents and accidents from around the world. If it concludes that lifeboat launching systems are necessary, the study should be extended to formulate requirements that embrace common operating procedures. The systems should capable of being operated and readily understood by
people with minimum training and experience and, above all, can be used for training and deployment both reliably and safely without injuring anyone.
SECTION 1 - BACKGROUND
1.1 INTRODUCTION
Since the United Kingdom’s Marine Accident Investigation Branch (MAIB) was formed in 1989, it has received a number of accident reports involving lifeboats, davits, winches and associated equipment. Some of these accidents have resulted in loss of life or serious injuries and have, where possible, been fully investigated. Many others were less serious, and the brief reports received usually focused on the immediate causes. Few of these less serious accidents were investigated by the MAIB, but when taken with the others they showed that lifeboats featured as one of the most common sources of accidents in merchant vessels, accounting for an unacceptably large number of injuries and deaths.
The UK was not alone in making this discovery. In a note to the International Maritime Organization (IMO) Sub-Committee on Flag State Implementation, dated 14 October 1999, Australia submitted a summary of lifeboat accidents covering nine such incidents between 1991 and 1998. Many of the findings echoed those seen in the UK database, and also noted that most of the accidents occurred during training or exercises.
Neither the UK nor Australia had any record of a complete or partial emergency evacuation of a vessel using lifeboats but were aware that they had occurred in vessels of other flagged states. One of the most recent was the evacuation of the Bahamian flagged cruise ship Sun Vista in the Malacca Strait on 20 May 1999, when everyone on board managed to get away safely in calm conditions. The MAIB noted from the accident
investigation report that many lifeboat deficiencies were identified. The MAIB was sufficiently concerned by the seemingly endless reports of accidents involving lifeboats, and their launching systems, that it decided to carry out a safety study and report its findings. This decision was prompted partly by reports that a number of people no longer felt that carrying out drills in lifeboats was safe. If true, and crews were indeed reluctant to train with lifeboats, it would mean that the necessary skills may not be readily available in the event of a real emergency.
The MAIB Safety Study was initiated to examine lifeboats and their launching systems.
1.2 STUDY AIMS
Using information held on the MAIB’s database as its primary source, the Safety Study had five aims:
1. To draw the marine industry’s attention to the number of accidents that have occurred since 1989.
2. To ensure that lessons are not forgotten.
3. To identify common factors leading to these accidents.
4. To review the risks associated with lifeboat launching systems by examining common problems encountered.
5. To make recommendations which would contribute to improving safety at sea.
1.3 MAIB’s DATABASE
All accidents considered in this Study have been reported to the MAIB under the UK’s Merchant Shipping (Accident Reporting and Investigation (ARI)) Regulations, or have been investigated by the MAIB on behalf of another administration. Reports received since 1991 have been entered in to the MAIB database. Although the ARI have been amended twice since they were first introduced, and the classification of some types of incidents has changed, those associated with lifeboats and their launching equipment have remained constant.
The data for this Study has been derived from three basic sources: the MAIB’s own investigations of the more serious incidents, information held on its database, and from reports submitted to the Branch by ship’s safety officers, masters and/or shipping companies.
1.4 DATABASE SEARCH
The MAIB database was searched to identify accidents involving lifeboats, davits or their winches. The results are set out in Annex A.
The accidents were classified under the following headings:
Classification Number of Incident Injuries Lives Lost
Hooks 11 9 7
Tricing and Bowsing 10 5 2
Falls, Sheaves and Blocks 12 19 2
Engine and Starting 18 15 0
Gripes 12 10 0
Winches 32 8 0
Davits 7 7 0
Free-fall 2 1 0
Weather 2 0 0
Not Otherwise Classified 19 13 1
Successful Evacuation 0 0 0
Total 87 12
The 12 lives lost and 87 injuries relate only to professional seafarers.
1.5 OTHER FATAL ACCIDENTS
To put these accidents in perspective, a search was also made for all other fatal accidents, not involving lifeboats and launching systems, over the same period. The results are set out in Annex B and show that 73 lives were lost.
They are summarised as follows:
Type of accident Lives lost
Entering confined spaces 12
Fall overboard 12
Fires and explosions 10
Access to ship 7
Mooring and towing lines 6
Crush (machinery) 6
Slips and falls 6
Crush (cargo) 5
Lifting gear 3
Tug girting 2
Capsize 2
Weather 2
All lives lost were those of professional seafarers.
The list shows that the same number of lives were lost in accidents involving lifeboats
and their launching systems as were lost in each of the two other activities that had the
most fatalities: entering confined spaces (12) and falls overboard (12).
SECTION 2 - COMMON PROBLEMS ENCOUNTERED WITH LIFEBOATS
AND LAUNCHING SYSTEMS
2.1 ON-LOAD RELEASE HOOKS
The most common cause of fatal accidents involving lifeboat launching systems is the failure of on-load release hooks. In the 11 accidents reported over the 10-year period, seven people were killed and nine injured. These figures suggest that although there are still relatively few such failures, the consequences can be serious.
A SOLAS requirement for lifeboats on ships built after 1 July 1986 stipulates that they should be fitted with a hook disengaging gear, capable of being operated both on and off-load. This requirement has resulted in a number of manufacturers worldwide developing various ingenious mechanisms for satisfying the regulation. As a result, many on and off-load release hooks have become over-complicated, and a number of
accidents have occurred. These accidents have generally resulted in a lifeboat being released involuntarily from one or both of its hooks. On those occasions when only one hook has been released, the attachment at the other end was often torn away, causing the lifeboat to drop into the
water; sometimes inverted.
As older vessels are withdrawn from service, the proportion of vessels susceptible to this predicament will increase.
2.1.1 Operational
It has been found that crews generally have a poor understanding of the operating principles involved with release hooks, often because of inadequate training. This is not the only reason. Poor labelling, complex mechanisms and hard to follow operating instructions in some manufacturers’ manuals have also featured as contributing factors (see Figure 1).
Once a lifeboat is afloat, crews can often find a method of releasing it from its hooks even if they cannot operate the release mechanism correctly. At the present level of development of on-load release systems, it is usually possible to remove the lifting rings locally. This is not an explicit requirement of SOLAS, but systems so far encountered by the MAIB have always been arranged like this. Analysis of a number of accidents reveals that premature hook release has often been caused by the failure to re-set it correctly when the lifeboat was being recovered from its previous launching. This shortcoming stems from a lack of understanding of the mechanism involved, inadequate training and poor maintenance. Once the hook has been incorrectly reset, spontaneous release is possible at any time before the lifeboat is next put in the water (see Figures 2 and 3).
IMO Resolution MSC.48(66) adopted the International Life Saving Appliance (LSA) Code on 4 June 1996. This amended Chapter III of SOLAS on lifesaving appliances and arrangements by requiring a special mechanical protection to be provided, rather than the earlier adequate protection to counter the possibility of accidental or premature release of hooks.
The new code requirement applies only to equipment fitted to new ships. It is not yet clear how future designs will evolve to satisfy this requirement. It is equally unclear how such changes will reduce the number of premature releases of lifeboat hooks.
2.1.2 Design
Most designs of on-load release hooks are fitted with an interlock designed to prevent release before the lifeboat enters the water. To satisfy the SOLAS requirement for an onload release capability it is, however, possible to override them. There is also a SOLAS requirement for the on-load release capability to be protected against accidental or premature use. Some designs include a hydrostatic or mechanical interlock to satisfy this requirement. Where fitted, the MAIB knows of no incident where failure of such a device has led to involuntary release.
Some flag administrations interpret this SOLAS requirement differently. They do not insist on an interlock to prevent premature release, and this has meant that a number of companies worldwide, have made systems that do not have a common level of protection against premature release. The failure to provide an interlock has been responsible for a number of accidents. Responsibility for this situation lies with the Flag States and not the manufacturers who merely comply with the requirements.
Amendments to Chapter III of SOLAS, contained in The International Life Saving Appliance (LSA) Code, contain additional wording covering requirements for on-load release hooks. It remains to be seen whether these changes will lead to a reduction in the number of accidents, or any uniformity of requirement between administrations.
Despite these developments, a problem still exists with some vessels built after 1986. These have equipment unprotected by mechanical interlocks, or
have operating procedures that do not differentiate between releasing on and off-load.
2.1.3 Maintenance and repair
To comply with the requirement that both hooks are released simultaneously from a single control position, it is common for release mechanisms to include flexible cables to connect the control lever to the hook mechanisms (see Figure 4).
Operating cables
The cables are usually of a type where an inner multi-strand wire slides within an outer sheath; sometimes referred to as bowden or morse cables. They offer a lightweight, cost effective and simply installed method of transmitting the usually moderate forces and motions required to operate most hook designs. The MAIB has found, however, that these cables can seize if the stranded wire becomes corroded. This can result in the on-load release hook failing to close properly when being reset. This in turn has resulted in inadvertent release later. Once corroded these cables cannot be repaired effectively, and have to be replaced. The evidence shows that management and crews are often unaware that such replacement is necessary. In response to one MAIB recommendation, a manufacturer amended its on-load release hook operation and maintenance manual to emphasise the importance of replacing damaged or corroded cables. It is not always the case. It is known that some other manufacturers do not draw attention to the inherent dangers of not replacing corroded cable.
Complexity of design
Investigations of several incidents have found that on-load release hook systems are complex and difficult to understand without having an in-depth knowledge of their mechanism and the operating instructions. One hook design associated with a particularly serious accident relied on very fine engineering tolerances being maintained. Wear, combined with fretting and corrosion, affected the forces on its
components and its ability to resist spontaneous opening. Its designers and type approval organisations paid insufficient attention to the hostile environment in which it had to function, such as salt air, weather and vibration. There was also a failure to recognise how seriously these conditions would degrade the hook’s performance. The MAIB is uncertain whether the existing testing requirements for this particular system are sufficient to address these very real concerns. It believes that a unified testing document would help. Automatic approval should not always follow when a system performs the tests presently required by SOLAS. Consideration must also be given to the likely ability of the system to perform in the marine environment between surveys and inspections.
Crews rarely possess the necessary engineering knowledge to fully understand the system operating principles. In several accidents the complexity of the design has been clearly linked to maintenance and operating problems. This complexity has not always been appreciated, nor the need for maintenance by staff with specialist knowledge recognised.
Without specific training for the equipment in use or easily understood and high quality instruction and operation material, seafarers are unlikely to acquire an adequate understanding of these designs. This has been shown to have an adverse influence on the quality of on-board maintenance, and has also led to sloppy and dangerous operating procedures.
The need for reliable and comprehensive maintenance is paramount; there is sufficient evidence to show this is not being achieved in a number of vessels. The MAIB believes that the need for such quality maintenance based on an in-depth understanding of the design and mechanisms is so important that only the manufacturers and their agents should service such systems, or personnel who have undertaken a manufacturer’s
approved course. This is supported in the text of the 1996 Amendments revision to SOLAS, which requires thorough examination and test during surveys by properly trained personnel familiar with the system.
The MAIB notes that the amendment has not yet been included in the legislation of the United Kingdom and some other Flag States.
2.2 BOWSING AND TRICING
Of the ten accidents reported involving bowsing and tricing, one resulted in two fatalities, and five in injury.
2.2.1 Operational
If a lifeboat is not to be boarded in the stowed position, it must be capable of being held in to the side of the vessel for safe embarkation. This is achieved conventionally by the sequential use of tricing pennants and bowsing tackles. Launching procedures call for the lifeboat to be lowered to embarkation level while the tricing pennants pull it into the side of the vessel (see Figure 5). Once at the correct level, bowsing tackles are secured between the forward and aft lower blocks and the ship (see Figure 6). When tightened they take over the function of the tricing pennants,
which are then disconnected. This process can be time-consuming while the bowsing tackles can be heavy and awkward to handle, particularly on high capacity lifeboats. Investigations have shown that the full bowsing-in procedure is often ignored during crew exercises. When the lifeboat carries only its launching crew, holding the lifeboat to the side of the vessel with just the tricing pennants can be achieved with relative ease, and causes no serious problem. Attempting the same procedure with a fully or, indeed, partially laden boat is potentially dangerous. A number of accidents have occurred as a result. In most exercises the lifeboats are rarely fully loaded, and the need for rigging bowsing tackles is often ignored, particularly if the boat is to be returned to its stowed position immediately afterwards. Such a procedure then becomes the normal practice, and the correct techniques are either ignored or forgotten, with launch crews viewing the bowsing tackles as cumbersome and an unnecessary nuisance.
Bowsing tackles have an important role to play to bring the lifeboat plumb on its falls. With the lifeboat triced into the embarkation position it becomes necessary to transfer the load to them. Many accident investigations, however, reveal a variety of shortcuts and unsafe procedures that result in injuries.
There is evidence to show that some crews do not rig the bowsing tackle, but choose instead to let go the tricing pennants by releasing the senhouse slips. This, at best, results in a lifeboat swinging out from the ship’s side in an uncontrolled fashion and injuring those embarked, sometimes seriously. Unless the lifeboat’s crew are safely secured, they may be injured by the sudden movement, or lose their balance and fall
over the side. The risk of this happening is high, particularly if any of the crew is on the lifeboat’s canopy to gain access to the tricing pennants’ senhouse slips. Properly rigged and tensioned bowsing tackles remove the loads from the tricing pennants before they are slipped. By gradually paying them out, the lifeboat can be controlled to reach the plumb condition so that undesirable and potentially dangerous swinging is avoided. This is the procedure that properly trained and disciplined seafarers or lifeboatmen are expected to follow, and one of increasing importance if the vessel is developing a lowside list.
Because so many exercises do not involve lowering the lifeboat into the water, the decision is often taken to dispense with the bowsing tackles altogether, and continue with the tricing gear alone. What starts as a convenient measure develops into accepted practice which may well lead to injuries in training or drills or, worse still, the
procedure to be used in an emergency. A second potential danger of not bowsing in a lifeboat is that a loaded lifeboat might overload the tricing pennants. If they fail (see Figure7), the consequences can be serious. This is likely to occur if the lifeboat is brought hard against the ship’s side. It can even lead to the falls going slack if the winch wire is paid out too far. Tricing pennant
failure would again cause the boat to swing uncontrollably, endangering anyone who happened to be embarking at that particular moment.
Failure of a single tricing pennant with slack falls has been known to have serious implications. When continuous falls are fitted, they will run out at the end where the failure has occurred. The lower block at the other end will simultaneously rise, sometimes sufficiently far and hard to hit the head of the davit arm. This imposes a dynamic overload on it and may lead to failure with the consequential repercussions for anyone in the lifeboat. This seemingly unlikely train of events has occurred in one boat where the crew was testing experimental tricing/bowsing gear (see Figure 8). It was a serious accident and people were killed. The MAIB has received reports of tricing pennants failing in some vessels, and the
crews being persuaded to increase the pennant strength to prevent a repetition. In the MAIB’s opinion this further encourages the crew to retain tricing pennants in exercises, rather than use the bowsing tackles.
2.2.2 Design
A further consequence of not properly bowsing in a lifeboat can occur if the load
bearing capacity of the davit arms is dependent on support offered by the back falls which lead inboard from the davit heads (see Figure 9). With the lifeboat at embarkation level, and supported by falls and tricing pennants, its weight is shared between them. The greater the proportion of weight taken by the tricing pennants, the less will be taken by the falls. This gives a corresponding reduction in the load on the back falls, which means that their contribution to supporting the davit arm is reduced. This results in an increased portion of the load being taken on the supporting structure of the davit arm and can, on some designs, overload it if the boat is fully laden (see Figure 10).
In this context it should be noted that bowsing tackles, in contrast to tricing pennants, are normally arranged so that when fully rigged, they are close to the horizontal. Tricing pennants are usually much nearer to the vertical, and therefore take a greater proportion of the boat’s weight. This geometry ensures that properly rigged bowsing tackles are unable to support any significant component of the boat’s weight, so make no significant reduction to the load on the falls.
This critical feature has led to one total failure of a davit arm during an overload test. The surveyor failed to recognise the contribution made to the davit arm’s support by the back fall load. He agreed to the test load being supported directly from the davit head, rather than being applied to the hook and lower block. On application of the test load, the davit arm was torn from its trackway. Fortunately since it was a test, nobody was in a
position to be injured, but it demonstrates how important the support of the back falls load can be in some designs. Ship’s crew can rarely identify whether back fall loads
are critical features of a davit design. Such information is normally the preserve of the designer or those who have
carefully analysed the design. Those who actually operate the systems do not, in practice, need such detailed knowledge providing they routinely follow the correct
tricing and bowsing which will eliminate any possible danger. The examples of failures stemming from the incorrect use of tricing pennants, and the difficulties found in using bowsing tackles, raises the question as to whether they are still necessary.
They were first introduced in days when lifeboats tended to be relatively small, light and open. Over the years lifeboats have become increasingly larger and heavier, and many are now enclosed. Both tricing pennants and bowsing tackles have, however, been retained with their strength being simply increased in proportion to the increased weight. The increased size and weight of many modern lifeboats has further implications: an
increase in manual effort for the crew.
Some owners and equipment manufacturers have recognised these shortcomings in exercises. Many of the problems are operational, but by the time the system has been selected, installed and commissioned, it is too late to do anything other than make comparatively minor, non-structural, changes to improve matters. Solutions to the known problems of trying to hold in a large heavy boat have usually been solved by designing a
combined tricing and bowsing gear operated by a winch. Some equipment manufacturers have rethought the entire concept, and have designed
new types of launching systems which have totally dispensed with tricing and bowsing systems. Although the costs are higher than many more traditionally based systems, the design philosophy appears to be worth close scrutiny by the industry. As part of its study, the MAIB attempted to gauge the industry’s reaction to such a development, and soon detected a difference of opinion. On the one hand there are designers attempting to market systems which they consider to be better and safer than those currently in use. On the other, there are shipowners who are not only concerned by the additional costs involved, but have reservations about the risks of introducing an untried system. They are also concerned about the possibility of having to modify or change it after installation to ensure that it works properly. Some shipowners are also influenced by the international regulatory system, and the need to satisfy the requirements of SOLAS. While a laudable attitude at face value, it ignores the reality that these standards are minimum requirements and can be exceeded.
2.2.3 Maintenance and repair
MAIB’s database has insufficient information to allow an analysis to be made of the effectiveness of maintenance and repair regimes for tricing and bowsing gear.
2.3 FALLS, SHEAVES AND BLOCKS
Two people have lost their lives and nineteen have been injured in twelve incidents involving the failure of suspension links or chains. A factor identified in most of these accidents was that the components were manufactured from high tensile steel. Analysis of the incidents has shown that incomplete post-welding heat treatment generated inappropriate properties. It was also found that incomplete test records contributed to the final outcome.
The UK administration accepted these findings, and introduced additional survey and documentation requirements for these high tensile items.
Several failures of fall wires have occurred due to incorrect installation, abuse or failure of components, such as sheaves or motor limit switches. None resulted in death or injury and there has been only one case where failure was attributed to corrosion and/or fatigue. An overall analysis suggests that the present requirements for fall surveys and replacements are satisfactory.
2.4 ENGINE STARTING
Some crew members have been injured while attempting to start lifeboats’ engines. In general these have been caused by poor starting techniques, and there is no evidence to indicate the problem was unique to lifeboat engines. Many of the incidents were attributed to a lapse of attention and are common in any activity, including the starting of engines. They can be avoided.
2.5 GRIPES
Relatively minor injuries have been caused by various parts of lifeboats’ gripes. Ten people have been injured in 12 incidents. The most frequently observed cause is when the gripe is under tension, and a hand or finger is trapped by the senhouse slip leg, springing back when the retaining ring is knocked clear.
The need to free gripes manually is gradually diminishing with the introduction of automatic gripe systems; favoured where lifeboats are boarded in the stowed position. These appear generally successful in the sense that they require no manual operation of slips etc. They effectively remove operators from potential danger.
The MAIB received one report where the hard eye on the freed end of a gripe fouled the gripe’s bobbin and the domed head of a mounting bolt (see Figure 11). This happened during the early stages of lowering. Fortunately it happened during an exercise where there was someone available on the vessel to free the gripe. Had this occurred in different circumstances, the lifeboat could have been loaded, lowered clear of its davits, and yet been prevented both from being lowered to the water and raised under control of the people in the lifeboat. Changing the size of the hard eye allowed the gripe to slide freely over the bobbing and cured the problem.
2.6 WINCHES
The most frequently recorded source of accident involves winches: there have been 32 incidents leading to 8 injuries. Although there have been no fatalities, some of the failures have had the potential to cause very serious accidents.
2.6.1 Design
Some designs of lifeboat davit winches employ a form of one-way clutch to allow their gear train to rotate while hoisting and without the need for the brakes to be released simultaneously. Alternatively, they are used to prevent rotation of the hoist motor shaft when power is shut off (see Figure 12). For a number of years these units consisted of spring-loaded pawls running over toothed sprockets. During the 1960s several new designs of winches were submitted to the UK Administration for approval. Some employed one-way sprag-type clutches. These used smooth inner and outer tracks, and relied entirely on friction forces to lock the unit.
Carefully shaped spring-loaded sprags within the annular space between the tracks, generated the locking forces. These units ran free when one half of the unit turned, and locked when opposite rotation was applied. Confidence in these apparently untried units was initially low, and did not improve until several designs had been subjected to rigorous on-load testing. Most one-way clutches were fitted to winches having a Safe Working Load (SWL) of 6 tonnes or less, and many were designed for hoisting using hand power alone. If hoist motors were supplied they
were often portable.
Winch designs have changed in the decades since then, and lifeboat winches now often have one-way clutches. There are also more types used, including one that uses springloaded rollers. Another uses non-symmetrical sprags and disengages with the help of dynamically-generated forces.
Some of these one-way clutches have failed in service. In such circumstances a lifeboat can lower uncontrollably and in some conditions, such as having bowsing or tricing gear connected, it can tilt. The consequences for any occupants are likely to be serious. Clutch failure can also lead to the lifeboat descending with neither the centrifugal nor manual brakes having any effect. Such failures have been found to occur immediately
the hoisting motor has been stopped, when stowing the lifeboat, or when adjusting its position at embarkation level using the motor. The clutch is unable to re-lock after having run in the freewheel direction.
The MAIB is concerned about these failures, and is carrying out an investigation to identify the principle reasons why one-way clutches in lifeboat winches have failed. This investigation is not yet complete.
2.6.2 Maintenance and repair
Although there is no recorded incident of a winch’s gear train failing, there are many reports of other components not functioning as intended, such as one-way clutches, brakes and switches. These have usually been due to shortcomings in their maintenance, repair or adjustment but have not, fortunately, resulted in any fatalities.
Reports by owners and ships’ officers point to many instances of neglected or incorrect maintenance, causing brake failure. Examples include excessive wear, oil or grease contamination, incorrect adjustment and assembly. Efficient winch brakes are essential to the safe lowering of lifeboats, and to ensure they function correctly they must be correctly maintained. The winches are often regarded as being straightforward items of machinery, and very suitable for maintenance by ship’s staff or general engineering contractors. Regular preventative maintenance is, of course, essential and well within the competence of a qualified ship’s engineer, but many owners arrange for ship’s staff or non-specialist
contractors to undertake major overhauls and rebuilds. This is not satisfactory and many reported incidents owe their origins to such work being carried out incorrectly.
