Mar 162015

One might be forgiven for believing that controllable pitch propeller systems are the illegitimate children of HAL, from the science fiction movie 2001: A Space Odyssey, with a dangerously psychotic mindset all their own. Take the grounding of  the Cyprus-flagged MV Merita at Steubenhöft in Cuxhaven.

Germany’s Bundesstelle für Seeunfalluntersuchung, Federal Bureau of Maritime Casualty Investigation, tells the tale of a disobedient vessel caused by the failure of a worn coupling in the wrong time and place:

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Dec 022014

Curiosity is a much underused tool for improving safety. From the commissioning of the 93m chemical tanker Key Bora in 2005 no-one wondered why the astern response of its controllable pitch propeller, CPP, was four times slower than its forward response, it was accepted with a shrug as just one of the quirks of this particular vessel. It had not gone unnoticed, it had just gone unquestioned until she rammed a jetty in Hull putting a 90cm hole in her bulbous bow just above the waterline.

It is a good example of how something Not Quite Right, NQR, can lead to a close call and when both go unremarked sooner or later there will be a hit. In the old days of naval warfare the first shot rarely hit the target, it would either overshoot or under shoot the target. A range adjustment would be made and a second shot fired. If that didn’t hit the target it still enabled the gun crew to get a more accurate range, to bracket it, and the next shot would hit the target. A wise commander on the target vessel would take avoiding action to prevent the aggressor bracketing his vessel. Continue reading »

Sep 242011

At 1524 (UTC) on 26 February 2011, the platform supply vessel (PSV) SBS Typhoon was undertaking functional trials of a newly installed dynamic positioning (DP) system while alongside in Aberdeen Harbour. Full ahead pitch was inadvertently applied to the port and
starboard controllable pitch propellers (CPP), causing the ship to move along the quay.

Contact was made with the standby safety vessel Vos Scout and the PSV Ocean Searcher, causing structural and deck equipment damage.

Ahead pitch was applied to the CPPs because an incorrect pitch command signal was generated by the DP system signal modules. The error was not identified during factory tests or during the pre-trial checks although the system documentation specified the correct
signal values. Actions taken on board to limit damage were hampered by a defective engine emergency stop and because a mode selector switch on the DP system was not moved to the correct position.

The following video appears to have been speeded up:

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Mar 202011

Controllable pitch poperllers: Too much of a twist in the tail?

Although little is yet known regarding the failure of the controllable pitch propeller of the general cargo ship Kholmogory, reported by Russia’s Maritime Bulletin, it is a reminder of the problems that can arise with this equipment, including a somewhat unnerving habit of suddenly running the ship astern.

According to Maritime Bulletin: “On March 17 at 2050 LT m/v Kholmogory suffered variable pitch propeller mechanism failure in 59 56N 025 44 E, in Finland MRCC safety zone. Vessel was enroute from S-Petersburg Russia to Norrköping Sweden. Icebreaker and tug from Finland were requested for assistance and towage to Swedish port. Russian icebreaker Kapitan Lus towed disabled vessel from ice to clear water, towage completed at 0235 March 19. Vessel drifting, awaiting tug from Finland”.

MAC has published a number of alerts and incidents on this kit and it’s important to be aware of what can happen:

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Nov 032010

CFL Patron

Controllable pitch propellers, CPPs, have a habit of belying their own name. Since CCPs often do not fail-to-safe and you could find yourself bucking around in a large vessel in close and crowded quarters so be ready for it when it happens.

That’s the message from the UK’s Marine Accident Investigation Branch, MAIB, in its preliminary report into a contact incident involving CFL Patron in Immingham Docks.

MAIB did not discover why the CPP failed but the Chief Inspector of Marine Accidents has written to the vessel’s manager, CFL Shipmanagement B.V., regarding emergency preparedness for propulsion failures on its vessels; pre-departure testing of propulsion systems; and preservation of evidence and data following an accident.

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Jul 042008

The US Coast Guard has issued to following safety alert:

A marine casualty in March of 2008 involving a fishing vessel in the Bering Sea resulted in multiple
fatalities and complete loss of the vessel. A Marine Board of Investigation is currently examining the
various circumstances surrounding the casualty. Although the investigation is not complete, safety
issues associated with casualty have been identified that merit immediate public dissemination.

Based on the survivors’ testimony, the crew experienced difficulty with launching and entering the
three liferafts because the vessel was making considerable sternway when the order to abandon ship
was issued. Evidence indicates the main engines were still running and the vessel was backing with
significant astern pitch. Consequently, two of the liferafts quickly traveled forward past the bow of the
vessel when they were launched. Attempts to retrieve the liferafts using the painter lines were
unsuccessful. As a result, the majority of the crew members were forced to jump into the 34°F water
and attempt to swim to the liferafts. Ultimately, only 22 members of the vessel’s crew made it into the
liferafts. All of these crew members survived. Of the other 25 crew members who never made it into
a liferaft, four died and one remains missing.

The Coast Guard strongly recommends that owners, operators, and masters of vessels with
controllable pitch propellers understand the design and operation of the system. This includes the
primary and emergency sources of power for both the control and main systems, the location and
procedures for using alternate control stations, and the locations of the emergency shutdowns. While
controllable pitch propeller systems are generally designed and constructed to fail in the “as is”
position, in hydraulic CPP systems, the actual blade pitch may change. In this case the vessel was
making considerable sternway. This was not a unique occurrence. The MS EXPLORER also
experienced this problem before it sank in November of 2007. Vessel operators, masters and crew
members must be prepared to respond accordingly.

In light of this incident, vessel owners, operators, masters and crew members should also be mindful
of the following safety issues:

1. Vessel masters and officers must maintain situational awareness at all times and understand the
effects of their actions and decisions on the safety of their crew, especially during emergency
situations involving flooding. This includes understanding what impact the vessel’s speed, heading,
heel, and trim will have on the crew as it abandons ship.

2. The master or individual in charge must evaluate the particular circumstances of each emergency
situation (weather, seas, experience of crew, condition of vessel, etc.) and adjust emergency
procedures accordingly to provide for the safety of his crew, vessel, and the environment.

3. All crew members should understand that immersion suits will affect their dexterity, limit mobility,
and may make it more difficult to launch survival craft, particularly when the survival craft are covered
with snow or ice. Crew members responsible for launching the survival craft should practice and be
able to do so with their immersion suits on. Lifesaving gear should be kept free of ice and snow
whenever possible.

4. When abandoning ship, crewmembers should make every effort to enter directly into a liferaft or
lifeboat before entering the water. If crewmembers must enter the water, they should stay together
and attempt to enter a liferaft, climb onto floating debris, or use any other means available to get
themselves out of the water as soon as possible.
5. Emergency Drills should not be limited to routine procedures such as donning immersion suits.
Emergency drills should ensure all crew members, including bridge and engine room personnel,
understand and practice what to do in various emergency situations under actual conditions.