SOLAS V carriage requirements

This page introduces the SOLAS V carriage requirements for navigation aids. It then discusses the principles of operation for some equipment and actions to be taken in the event of a failure.

solas v carriage requirements for nav aids

The requirements for shipborne navigational equipment are contained in SOLAS V/19.

In summary, these are:

All vessels are required to carry the following:

- adjusted magnetic compass, pelorus ring, and means of correcting the heading
- nautical charts and publications sufficient for the intended voyage
- ECDIS with suitable backup arrangements
- GNSS receiver
- means of communication to the emergency steering position
- sound reception devices for totally enclosed bridge wings

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All ships that are over 150gt, and all passenger ships will carry an extra:

spare magnetic compass
daylight signalling light
bridge navigational watch alarm system (BNWAS)

All ships that are over 300gt, and all passenger ships will carry an extra:

echo sounding device
9Ghz radar and electronic plotting aid
speed log capable of measuring speed through the water
adjusted heading transmitting device
automatic identification system

All ships over 500gt will carry an extra:

gyro-compass and heading repeater and bearing device
rudder, propeller, thrust, pitch and operational mode indicators
automatic radar plotting aid (ARPA)

All ships that are over 3,000gt will carry an extra:

3Gz radar and ARPA

All ships that are over 10,000gt will carry an extra:

heading or track control system

All ships that are over 50,000gt will carry an extra:

speed log capable of measuring speed over the ground in a fore, aft and athwartships direction
rate of turn indicator

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What are the principles of operation of the various speed-measuring devices?

There are many designs of speed-measuring devices used on ships, but by far, the main ones used are the doppler and electromagnetic logs.

The Doppler log exploits the fact that sound signals suffer a Doppler shift effect when transmitted through a moving medium. By acoustically measuring this shift, the well-calibrated Doppler log can deduce the vessels' speed through the water and over the ground at suitable depths.
The electromagnetic (EM) log exploits the Faraday-Maxwell induction law, whereby a change in the magnetic field surrounding a wire coil will induce an electromagnetic charge within the coil. The size of the voltage is proportional to the relative speeds between the magnetic field and the coil. EM logs can only provide speed through water capability.

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What are the navigational repercussions of a speed log failure?

When the speed log fails, either totally or by outputting spurious readings, any data supplied by equipment interfaced with the log also becomes suspect. This includes aid in navigation such as gyrocompass, ECDIS, autohelm / track-pilot, and other ancillary equipment such as VDR and AIS.

However, the most important piece of equipment affected is the Automatic Radar Plotting Aid. This is because the ARPA works in two steps:

First, the spinning scanner provides successive observations of detected targets. Three or more of these successive observations go towards building the OA relative vector of the closing target.
Next, the ARPA will complete the OWA triangle by applying the WO own-ship vector determined by the vessel's speed and course data to the OWA plot. From this, the ARPA will find the other vessel's true WA vector and complete the triangle. Any error in the ship’s own WO vector will lead to a subsequent error in the deduced WA vector and, therefore the derived values of the target’s aspect, course and speed.

The failure of the speed log, therefore, has serious consequences, which the prudent Master will recognise and promptly address to bring the vessel to the proper levels of watchkeeping.

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Actions to be taken by the ship's master in the event of a speed log failure

Upon first learning of the failure, the ship's master will relocate himself to the bridge to manage the situation. Once there, he will include the following in his actions and considerations:

Change over to the second log, if possible, bearing in mind the different setup requirements of various speed logs, calibration inaccuracies between types, as well as their input on the stabilisation mode of the radar display.
Inform the ETO (or Chief Engineer) of the failure, making a request to arrange a service agent at the soonest practicable moment. The prudent master would not trust the veracity of a crew-repaired speed log until an accredited service agent has had the chance to visit the ship in the next port.
The ship's master will make a full appraisal of the navigational situation. If the condition is such that no immediate collision avoidance action is necessary, he may decide to leave the con with OOW.
In heavy traffic conditions, the change in operational efficiency of the equipment determines safe speed. Therefore, it may be necessary to reduce speed, to allow the bridge team more time to assess the conditions and risk of collision.

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How can the ship's master give a reasonable speed estimate in the event of a log failure?

An accurate best guess as to the vessel’s current speed would be made by reviewing the manoeuvring data posted on the bridge. The current engine parameters, including shaft RPM and propeller pitch, can be entered into the manoeuvring data to give speed through the water. Recall that figures taken directly from the manoeuvring data will be reduced by a factor called "slip"; we can get an estimate of this from the Chief Engineer.

This figure can be cross-checked against the averages during the previous voyage, provided that no alteration of engine settings has been made.

Additionally, the speed through the water value derived from the speed curves can also be checked by comparison with the speed over the ground. This information can be fed into the affected equipment where manual speed inputting is possible.

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Why is accurate speed input so important?

The Rules of the Rule are based primarily on ships taking collision avoidance actions according to the aspect of the other vessel. ARPA considerably expedites this process by calculating the course, speed and aspect of multiple vessels so that the OOW is freed up to concentrate on making collision avoidance decisions. When fed with reliable speed and heading inputs, the ARPA will automatically complete the OWA triangle and will give the calculated data of the aspect and the other vessel's speed and course.

Any deterioration of the reliability of the data supplied by ARPA concerning the other vessel’s aspect means that the vessel’s means for collision avoidance is hampered, and the attention of the OOW must be extended to manual calculations of the OWA triangle. This extra burden will be accounted for by the ship's master updating his standing orders to reflect the change. Such amendments would include the following:

Increasing the minimum clearing distance of other vessels.
Overtaking, head-on and crossing situations will, in particular, be addressed as these rules rely on the ship's aspect.
In any event, the failure of the speed log requires heightened vigilance to the traffic situation.

Finally, as the carriage of an operational speed log is a mandatory requirement under SOLAS V/19, and a failure of the equipment presents a non-conformity with this regulation. Any defects must be recorded in the Official Log Book and also reported under the SMS requirements to the company via the Designated Person Ashore.

As SOLAS V carriage requirements are not met, the validity of the Safety Equipment Certificate is now in question, and the Flag State and Classification Society shall be informed. Verifiable and documented notifications from these parties can be recorded as partly establishing the proper functioning of the Safety Management System.

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