Although we originally assumed that the rudder casualty was caused by an errant electrical signal sent to the bow rudder causing it to “unlock” and flop over, it seems that the actual cause was something entirely different.

Each rudder has two opposing hydraulic rams that are designed to work against each other. In this case one ram on each rudder was improperly plumbed during a recent visit to the maintenance yard. On each end of the ship, the rudders had only one ram controlling their movement. The force of the water offset from center during a turn is what caused the bow rudder to flop over damaging the system.

This plumbing problem once discovered is easily rectified. Unfortunately the damage to the system was extensive. In addition to the damage to the ram, the rudder quadrant (a massive triangular-ish steel casting) was shattered and needs to be replaced.

The quadrant is not something that is sitting around on a shelf anywhere. It needs to be made anew. It is my understanding that to do this, a large hole is cut into the deck and the old quadrant removed. A mold is created and new quadrant cast in molten steel. The quadrant is then annealed before the bearing holes and keyways are machined into it.

While the ship is out of the water for this work, the rest of the underwater portion of the steering system will be inspected and “magnafluxed” to see if there is any other damage.

Talk about “paying the butcher.” Ouch!!

Dan

Don Seltzer, a regular reader and contributer to the “Sea-Room” internet mailing list asked some clarifying questions regarding the engine and rudder controls on the Jumbo Mark II ferries run by the Washington State Ferry System. His questions asked basically what it takes to get the bow rudder back under control after it “flops over” and what effect a flopped over rudder has on the handling of the ship. He also asked if the bow propeller was “free wheeling” while the ship was traveling forward being pushed by the stern rudder.

The engines and rudders are controlled electronically from the pilothouse (s). Only one pilothouse is in control of the engines and rudders at any given time. Control is usually transferred to the “forward” pilothouse shortly before the ship leaves the dock. The system used to steer the ship is referred to as a “follow up system.” The backup system is called a “non-follow up system.” The difference between these systems is a little hard to explain without showing you the control handles and wheel. The rudder controls also get some input from the engine control computers and when the drive motors are in the “transit mode” (vice maneuvering mode), the computer sends a signal to the bow rudder which centers it removing any drag and reducing any pressure on that rudder. When the engine controls are in the Maneuvering mode, the bow rudder is freed up and then used to steer the thrust from the bow propeller with an effect very much like a tunnel type bow thruster. From a mariner’s point of view, it is a very slick system.

When the casualty occurred the other day, it was thought that an errant signal was sent to the bow rudder freeing it while we were traveling at speed in the transit mode (about 19kts). It was discovered later that a hydraulic line to the steering rams was plumbed incorrectly during the last yard period causing the casualty. The rudder flopped hard over placing tremendous pressure on the rudder and pintles, not to mention the hydraulic rams that work the system. It was the rams that were eventually damaged (on the other rudder) when we went out to re-create the casualty on a “sea trial” without any passengers aboard.

The ship’s steering normally operates in the “follow up” mode. Moments after the rudder flopped over, the conning officer reduced our speed to lessen the pressure on the rudder and the steering system was switched to the “non-follow up” or back up mode. Control of that rudder was immediately re-gained and the rudder was brought amidships. We continued our transit into the harbor using the follow up system for the stern rudder and the non-follow up for the bow rudder. The physical difference to an observer in the pilothouse is a couple of switches in different positions than usual and the landing made using a different set of rudder control levers. For the conning officer, you have to watch the dials pretty closely while you are doing it this way to make sure that you are getting what you are asking for.

When we went out the for the sea trial, the other rudder flopped over with such force that it destroyed one of the hydraulic rams that control the rudder. These rams are about 8 inches in diameter and about10 feet long. It is a pretty big deal to break one. This time we could no longer use that rudder at all so it was centered mechanically and locked into place and the ship was brought in on a slow bell using just the stern rudder. The ship was then out of commission and would not leave the dock again without a tugboat.

When landing the ship, the normal procedure is to have your stern prop turning slow ahead to give you water over the rudder and enable you to steer the stern of the ship. You then use the bow propeller to stop you and the bow rudder (and associated vectored thrust) to steer your bow into the slip. From sea speed of about 19.5 kts, we start slowing down about 6 cables (1200yds) from the pier. This is done just by reducing the thrust on the stern prop. At about 3 cables off, we take the ship out of transit mode and place it into the maneuvering mode. We test the bow rudder (by wiggling it a few degrees left and right) and also get the bow propeller turning slowly astern. By this time we have reduced speed to about 8 kts. The bow prop turing slowly astern produces a lot of drag and we now reduce our speed pretty quickly. If all is working well, we continue into the slip. If for some reason at 3 cables out we do not get the appropriate answer from the bow rudder or propeller, we still have time to put the stern propeller full astern and stop the ship with plenty of room not to break anything.

You can then regroup, set up the backup procedures and head on in. This type of casualty is a very rare thing and these emergency procedures are practiced all the time. In fact, in most cases, if there were an actual casualty on the way into the dock, the backups are put into place so quickly and seamlessly that the passengers would never know that it happened. It is a very safe system.

It is both interesting and exciting that my post regarding the steering failure on the Washington State ferry, M/V Tacoma was picked up by the news media and broadcast as “A first hand account” and a “tell- all account” of the harrowing events aboard the ship.

This is interesting because in no way did my account of the events of the casualty paint the situation as “harrowing” and in no way was I providing a “tell-all…”

On the other hand, it is exciting that in this world of instant news and cell phone execution videos, my words about a mechanical casualty have made their way to the main stream media as fast as I can type them.  Thank God for Al Gore and the internet!

All that aside, let me be perfectly clear.  The mechanical casualty on the Tacoma the other day was unusual and made for an exciting afternoon for the crew as opposed to the usual “back and forth” days that we spend at work.

What needs to be stressed is that when this happened to us, the Master, Mates and crew did exactly what they were trained to do.  They brought the situation back under control, assessed the damage and delivered our living cargo to port in a safe and expedient manner. 

Yes, there was a gale blowing out there. Yes, this thing made a very loud noise and caused severe shuddering throughout the ship.  And yes, the crew went immediately into their heightened sense of awareness and professionalism mode.  However, at no time was the ship, her passengers and crew in any danger whatsoever.

There were no raised voices in the pilothouse, no scratching of heads and wringing of hands.  There were no feats of heroic or extraordinary seamanship. There was nothing but consumate professionalism gleaned from years of experience and training. The backup steering system worked as designed and the ship came into port at slightly lower than normal speed that the prudent mariner chose under the circumstances.  Had it not been for the initial noise and shuddering, our passengers would never had known that anything had gone amiss.

The Masters, Mates and Crew of the Washington State Ferry system are highly trained professionals. We are members of the Masters, Mates and Pilots Union and the Inland Boatman’s Union of the Pacific. We operate the largest ferry system in the world carrying tens of millions of people each year. It is a finely oiled machine (well, oiled anyway…).

An update from the director of operations last night said the Tacoma was going to be out of service for a while due to a lack of available drydock space in the Puget Sound region.  The ferry system has shuffled some boats around and is back in normal operation with only a couple of hours down time and minimal inconvenience to our customers.

All in a day’s work.

Dan