Articles on S-VDR

Fixed or Float-Free?

This subject has been debated at many levels, for many years, by many people and no definitive answer has yet been reached!

How to choose?

The purpose of this paper is to examine the various merits of both systems and to attempt to record some of the key conclusions reached by others.

The basis of the debate is the interpretation made on the original IMO Performance Standards laid down for Voyage Data Recorders (VDR) A.861(20) dated November 1997.

Here, the following Purpose and Operational Requirements were stated:

Purpose

As defined in the I.M.O Performance Standards: "The purpose of a voyage data recorder (VDR) is to maintain a store, in a secure and retrievable form, of information..."

Operational requirements

The final recording medium should be installed in a protective capsule which should meet all of the following requirements:

• be capable of being accessed following an incident but secure against tampering
• maximise the probability of survival and recovery of the final recorded data after any incident

These clauses were then further clarified by the IEC. (International Electrotechnical Commission) in the preparation of their Technical Specification and Test Standards. IEC 61996 dated 1999.

During the preparation of this Standard, it became clear that there was no definitive interpretation of the term "maximise the probability of survival and recovery".

The Technical Committee was made up of a unique panel of experts with differing backgrounds.

In view of the comparative infancy of maritime "black boxes" , representatives from the aircraft industry were invited and encouraged to attend.

Their experience, spanning over twenty five years, proved invaluable in determining many of the standards necessary for adoption by the marine industry.

In general, their view of "maximising the probability of survival" was firmly in favour of a rugged fire-proof capsule which would remain with the vessel in the event of sinking.

When challenged on the recovery from a sunken wreck at depths the Committee were reminded of the successful recovery of the black box flight recorder fitted to the Air India Boeing 747 which crashed in the deep trench in the North Atlantic, off Ireland.

Clearly this demonstrated that such a recovery could be achieved but estimates of the cost varied from very high to extreme.

Nevertheless, the proponents of the fixed capsule pressed their case and concluded that the capsule should remain with the largest part of the casualty, meaning the vessel itself. Even if the acoustic beacon is no longer operating, then location of the wreck should be possible.

Others, who favoured the "float-free" approach , claimed that recovery would be at a fraction of the cost of the fixed version and would enable a far speedier availability of the data. They suggested that technology used in existing EPIRBs could be developed to provide such a solution.

EPIRBs (Electronic Position Indicating Radio Beacons) have been in existence for some twenty years and are designed to transmit a signal , when activated, via satellite. These signals can be interpreted to provide accurate position information to search and rescue services. More recent models include GPS information which is fed to the unit’s internal memory for subsequent transmission.

After much debate, specifications and test methods were drawn-up for both solutions, largely developed from the existing aircraft industry’s standard referred to as ED 56A.

Concerns continued to be expressed regarding the effect of heat on the radio transmission device contained within a standard EPIRB with the result that the final specification insisted that the float-free mechanism be inhibited if the fire exceeded the fire survivability of the transmitter.

Another stringent requirement, again adapted from the aircraft industry, was that of a penetration test. Whilst the severity of the aircraft specifications were reduced for the perceived marine environment conditions, the rest ruled out most, if not all, EPIRBs currently in production at that time. As a result, it is believed to be a truism that no VDR manufacturer offers a float-free option.

With a Performance and Technical standard in place, attention was then turned to the introduction of VDRs into the world’s maritime fleet. Whilst international agreement was reached for fitting in new vessels and existing passenger carrying vessels, legislation fell short of including existing cargo ships.

The Maritime Safety Committee (MSC) of the International Maritime Organisation (IMO) instructed its delegates to carry out a feasibility study on the carriage of Voyage Data Recorders (VDR) on existing cargo ships.

It was as a direct result of this study that the concept of a Simplified Voyage Data (S-VDR) was adopted.

The purpose of this simplified version was to provide the marine industry with an interim solution to the inclusion of some form of voyage data recording on older vessels, which may be equipped with diverse equipment, not readily suited to conversion to an external recorder.

One of the key decisions reached, of direct relevance to the fixed versus float-free discussions, was that the penetration test should be omitted for S-VDR and a relaxation of some of the environmental tests. This made the use of an EPIRB type device a far more practical proposition than was the case with VDR.

As a result, work is well advanced with experienced EPIRB manufacturers in the design and construction of a float-free device. However, it should be remembered that such a unit only represents part of a complete S-VDR system.

Most reputable S-VDR system manufacturers offer both a fixed or float-free option to maximise the probability of survival and recovery of the final recorded data captured.

The philosophy being to allow the customer to make their own choice. To assist in the decision making process and with the background to the subject now established, a number of points have been recorded and abstracted from papers presented or published over the past three years.

Type of casualty for Vessels 3,000 GT & above (1978 - 2000)

Tankers - Foundering Statistics

In the last 25 years less than 1% of the total number of tankers involved in accidents have actually sunk, moreover a downward trend in the number of tankers that are involved in serious incidents [has been experienced]
Source: Intertanko

Location - Post Incident

Fixed – The underwater beacon specified in the VDR and SVDR technical standards is designed to operate for 28 days following immersion. This gives time for an accurate position fix to be obtained during a one month period.

The decision or necessity to recover the capsule can be postponed for up to two years post incident.

Float-free – The beacon is designed to operate for 7 days following release from the vessel. The capsule must be located within this time frame, irrespective of priorities or sea conditions.

Recovery

• Fixed – Expensive and time-consuming.
• Float-free – Potentially much lower recovery costs with the benefit of minimal delay in gaining access to recorded data.

Cost Comparison

Float-free may be a lower capital cost option when compared with Fixed. However, consideration should be given to the additional through life costs associated with EPIRB based float-free storage devices , when preparing budgets.

Experience

Since the publication of the first IMO performance standard for Voyage Data Recorders, some 8 years ago, the Marine Industry has both studied and gained first hand experience in Voyage Data Recorders – Marine Black Boxes.

The SVDR standard, prepared specifically for the cost effective retrofit of VDRs in cargo vessels , allows manufacturers and shipowners/managers a choice in data storage configuration.

It should be remembered however, that the protected memory enclosed in a capsule is designed to assist investigation of the most extreme incidents.

VDRs and now SVDRs are providing the shipping industry with valuable information following far less serious incidents. Lessons learnt have already saved owners and operators time, money but perhaps even more importantly, avoided the repeat of many incidents.

This information has very often come, not from the final storage medium which is the subject of this paper, but from additional long-term data storage such as the removable ‘white box’ solution provided by Kelvin Hughes with their Manta Digital SVDR System. This option records several months of data in comparison to the 12 hours of the fixed or float-free storage medium in a convenient package which can be backed up ashore.

This allows minor incidents to be analysed swiftly and efficiently, without the need to access the protected memory.

Summary

Casualty/Foundering Statistics

The percentage of sunk against the number of casualties is 4.7% and of fire/explosion is 14.1%. The percentage of sunk against total casualties is a little greater that that against world fleet, but can still be considered few.

Post Incident Location & Recovery of Final Recorded Data