Great reply.
I asked a group of pilots once if they ever looked at a ships manoeuvring information and they all laughed and said no, except one. An Australian pilot said he would go up to the manoeuvring details board ( if he could find it) and put a thumb print on it. Physical evidence he stood there, no investigator could then prove he did not look at it! Great idea I thought, I do it from time to time with a bit of a giggle….
Sure thing , compressing water may be difficult.
Hm…. I suspect, that at such a dictum . Barrass would be hugely
EM-BARRASSED, that all his hard work was wasted and Bernoulli would require urgent CPR or even medevac.
However all hope is not gone for them both as there seem to be a silver lining under this very , very dark cloud above :
I think both would give a sigh of relief seeing this key sentence above as :
Speed Squared: The squat effect is proportional to the square of the ship’s speed, meaning small increases in speed result in large increases in sinkage.
“Allow one foot of squat for every 5 knots of speed”- Who said that ???
Pilots of the 1970 or about had such a rule of thumb before :
Actually the science kicked in a lot earlier then that . The “ modern “ article (2009) has been noted but one may argue, that oudated understanding of the squat is increasing the safety margin rather then decreasing it.
I am not sure if both the pilot and bridge team in the case discussed , spent time deliberating the dilution of and liquidity, not to mention viscosity and stratification of the mud layers ,when it is evident, that more down to earth issues were not discussed or were ignored and the dredged & surveyed & maintained space has less unknowns then surveyed once a year or about, whatever pilot mental picture of that space may be.
The quoted article is here:
Squat in muddy navigation areas.pdf (1.1 MB)
and another brief is below :
Practical squat assessment for a ship manoeuvring in muddy environments - ScienceDirect
On the issue of the wheelhouse poster :
The wheelhouse poster ( THAT IS THE CORRECT NAME ) must be permanently displayed on the bridge(mandatory requirement) of new ships of 100 meters LOA and over, new chemical tankers, and gas carriers to provide essential maneuvering data, as mandated by IMO Resolution A.601(15).( PLS READ ) It includes general particulars, turning circles, and stopping characteristics, and must be updated after modifications.
Therefore such comment must be interpreted as a joke from the “great all out SOLAS exemption “ environment as USCG /PSC is not so forgiving to FOC ships visiting USA.
Last but not least the Gentlemen from down under can be proud of their achievements in persuing “ science of navigation” instead of anegdotal navigation and expectation biases .
One more thing .
Today, UKC/squat it is considered a fundamental component of passage planning, as a ship’s “sinkage” and “trim” can change by several meters depending on its speed and the depth of the water.
I thank very much for the excellent 118 comment, especially for the pilots perception of the channel and channel concept
what surely can be much better understood by his own brethren, then by much narrower vision if any of the ship master relying on the intimate pilot’s knowlege of the area having no idea what a “ zig zag test is “ and for what purpose.
I am not sure though if the honorable judge ( hypotetical) sitting on the case will have the same understanding as the pilots , while chopping the master to pieces.
In this case 1001 transit proved fatal as the picture shows :
and the mud had to be very solid here and water somehow got compressed too.
CAUTION! Read the post carefully. The research results pertain to squat in a mud, silt, clay channel.
Squat in deep water is a real thing. The QE2 was running at high speed in deep water and was definitely squatting. She ran over a projecting rock, not a mud bank. There was no high density boundary layer to offset the squat. Another caution… the ship must encounter the muddy boundary layer gradually. If the bottom goes quickly from deep to shallow the squat will still be in effect and an isolated mud bank surrounded by deeper water will bring you to a quick halt.
I read somewhere that squat was first discovered by submarines in wartime. They would fire torpedos designed to strike below the waterline so the ship would sink, but they discovered that the point of impact was above the waterline when the ship was stopped. That had everyone scratching their heads. Did the torpedoes jump out of the water just before reaching the target? Not likely. Some smart guy figured out that the ships must be experiencing a hydrodynamic effect that caused them to run lower in the water at speed.
Regards
All the above is correct but in the real world, not always so.
I have seen Wheelhouse Posters with wildly different turning circles to port and starboard which in one case on deeper analysis found “Wind NW’ly 30 knots”. Meaningless results but engraved on the ship until the ship goes to scrap. I have also seen “ Data from sister vessel” so not actually the ship I am on. I do not think I have ever seen any change in data on older vessels, when the “new” full ahead is the old full ahead and if data with a bow thruster, you now only get 75% of the original.
It is not often ( if ever?) pilots do a 360degree constant turn, we build up rate of turn then reduce it on say a 120 degree turn.
I am not saying ignore the Wheelhouse Poster but definitely do not rely on it especially on a windy day and in shallow water.
According to the report depths outside the channel were 10.6 meters (35 feet). With tide 0.5 meters (1.7 feet) available depth is 11.1 meters. Ship’s draft was 11.7 meters.
Edit: fom the screenshot the ship grounded at 9.1 meters.
I think it would be insane and highly arrogant for a non-pilot to question the experience and expertise of the pilot , with decades behind him of coning the ship in an environment, which for the ocean going master is extreme . Hence i would rather use the words “ please advise “ then confront them with my ignorance of the issues that make them experts and not me.
Note however, that a little teasing and poking bear in the eye has resulted in fantastic comments including yours . But i am still in the dark on this weird “ expectation bias “ thing.
Stay assured that the old rules of thumb , created by generations of pilots, who operate in such extreme conditions plus some common sense has saved my ass more often then some complicated formulas created by some “academic mariners acting in overdrive “ mode, who when put on the bridge must be watched more carefully then others as their scientific frenzy blinds them even during doing simple tasks ( my own experience with such fellows) .
Examle : instead of fixing and plotting position on the paper chart in less then a minute , such bloke was doing the ellipse of pos. error what took him 20 minutes when i needed him dearly near conning position and i did not give a shit abt his ellipse.
Regardng the wheelhouse poster pls note that data there ( excluding loaded condition which if included is theoretical only ) is the closest thing to reality of the vsl in ballast/empty as it was created/calculated/experimented by shipyard and designers/architects and hence a better tool for reference then the best general formulas created by many and written in the books and many manuals.
The shallow watter effect on a turning circle and stopping distance is specifically included in this poster and it is for information to some that happen to be surprised regarding vessel behaviour in such conditions. It is surely not an instruction what to do and how to do for the pilot.
Guess what data is presented to the pilot during master → pilot exchange MPX FOR HIS SIGNATURE AND PERUSAL ? All what You see there is blind copied from wheelhouse poster. Therefore I am absolutely not surprised at the experienced pilots attitude towards it.
From reading the report expectation bias seems more plausible than a shiphanding error. From the report:
Pilot 2 told investigators that he chose to maneuver the vessel outside the
channel to starboard because, north of the Benjamin Franklin Bridge,
he channel made a bend to the starboard, and he expected the flood current would push the vessel to port.
I’ve seen it a couple times on the car ships on windy days in buoyed channels. Pilots with little or no experience in that situation will not expect how much a car ship sets in the wind.
The pilot will gain the center of the channel and then steady on a course that doesn’t sufficiently allow for wind set. The ship will set down on the leeward side of the channel, the pilot will change course, regain the center and then do the same thing again.
I’ve also see the other way, the pilot expects more set than reality. Port of Spain Trinidad and Tobago. I entered the buoyed channel on a windy day with the leeway dialed in for pilot boarding speed. As soon as the pilot got to the wheelhouse he immediately turned the ship more towards the wind. We zigzagged a couple times before the pilot ended back to what we were steering when he boarded.
That probably sound like a tall tale but human perception doesn’t work the way the way most people assume it does. Daniel Kahneman calls this error “What You See Is All There Is”, or “WYSIATI”
Article here at Safety4Sea: The illusion of certainty: The concept of WYSIATI
A little off topic but I did a little digging into the phenomena that would explain why an experienced ship pilot aboard an unfamiliar ship type would not quickly take into account the amount of leeway.
The FAA has termed it “Negative Transfer”
Negative transfer is defined in the context of this paper as the transfer from one cockpit to another–of different design or configuration–of habits or responses which were appropriate in the former but are inappropriate in the latter, thereby posing a threat to flying safety. This danger has been demonstrated not only experimentally but also in a number of aircraft accident investigation reports.
From here:
Negative transfer: a threat to flying safety
A narrative here of an pilot with F-16 experience crashing a glider.
Never Again: Negative transfer
This is the key phrase: “the transfer…of habits or responses”
A quite regular occurrence at the head of the passes in the Miss River.
What pilots of ships experience might be more extreme.
First of all, the same ship varies substantially between loaded and ballast conditions. This is true of aircraft too, from what I’ve read. A bomber full of fuel and payload is a different animal from the one returning empty from a long run.
But the pilot often experiences two ships of the same dimensions and the same draft that are worlds different in handling characteristics. Throw in a pitch propeller and everything goes out the window. We have been inoculated against Negative Transfer by Negative Experience.
Most pilots will tell you they reserve judgement on how to handle the ship until they’ve watched her carefully for a couple turns.
I once boarded a ship inbound and after the first couple turns I asked the captain if any pilot had ever told him his ship was a bitch. He pointed at the Voice Data Recorder and signaled me to follow him outside. Safely away from prying ears he told me he had been the captain during sea trials. The only official requirement for a rudder is that it be able to go from hard port to hard starboard in xx number of seconds. The rudder system couldn’t do it. The steering room was too small to accomodate a more powerful hydraulic system so the decision was made to cut a meter off the trailing edge of the rudder. No fairing. Square cut. The rudder passed that way. The ship launched.
the T2 US flag conversions from some years back were awful. Just did not turn, until they did, then didn’t stop turning
In a simulator I was given a ship with a “slow rudder”. Took me a solid minute to get the ship under control in a fairly narrow curving channel. I don’t need to tell any seaman/pilot that a minute is a loong time!
You ever work on the Chilbar?
No - but know the boat - along with the Concho - just awful
Pilots themselves are not in the best position to recognize which “habits or responses” they’ve carried over from other types of ships because shiphandling skills are largely unconscious, tacit knowledge. Pilots “know more than they can tell” (Polanyi’s Paradox).
Carried over habits would be more obvious to the crews of the different types of ships.
Some examples:
When I first started sailing chief mate on the car ship (wheelhouse forward) I was on the stern for mooring ops (to spot the stern ramp). On a 90 day trip around the world I wondered why it was so common during mooring ops for me to have to call the bridge to warn the captain that the stern was closing the pier too fast.
Later, when a captain shifted me to the wheelhouse for mooring ops I found out why. Both pilot and captain were on the bridgewing, watching forward , even though most of the ship was now aft. A habit carried over from conventional ships with the wheelhouse aft.
Here’s a post about it from 2009.
Another example, less common but also related to the house forward occurs in tanker ports that rarely handle car ships (with military cargo). That is the pilot underestimates how maneuverable car ship are compared to tankers. On the first turn too much rudder is used and first the ship will turn for the inside bank and then over corrected, rudder shifted, and turning for the outside bank. Big zigzag in the first turn. Saw this going into Corpus Christi.
I suspect that the house forward can cause a few pilots to underestimate the rate of turn. Tanker pilots also tend to be a bit more jumpy about getting slowed down.
The error of zigzagging from repeatably underestimating leeway in narrow, buoyed channels is uncommon. Seen it in three ports, Doha Qatar (channel 160 meters wide) Port of Spain (channel 122 meters wide) and one river port, don’t recall which one.
These observations are from experience in ports from A (Aqaba Jordan) to Z (Zarate Argentina), also I hold federal pilotage endorsement for about 500 miles of the Inside Passage in SE Alaska.
We get very few forward house ships where I pilot - like 1 a year, and it is a very different experience. You have zero feel for how fast the ship is turning, and then when you look back at the stern it looks like it’s flying.
I was not familiar with Poliany’s Paradox and had to look it up. Thanks.
It seems to refer to the inability of a person to articulate knowledge rather than form the basis for committing an error due to internal misunderstanding. A pilot example would be an apprentice pilot wanting to know exactly when to begin a turn. If they ask the pilot being observed they receive a blank stare and a reply along the lines of “start turning when you get to the turn”. Apprentice pilots begin using informal aids like starting a particular turn when the ferry office lines up with a distant water tower or something similar.
As for experienced seamen ignoring the stern because they are used to looking forward that seems difficult to believe. It would be like a car driver not looking behind while backing up because their usual viewpoint was in the other direction. We’re not talking about a distracted mother here, but a professional chauffeur.
There is a phenomena that might explain the tendency to close the dock too quickly when maneuvering alongside. Let’s equip an imaginary ship with bow and stern thrusters of equal power. When the ship is moving forward the turning point is close to the bow and when going astern the turning point is close to the stern. It doesn’t matter how fast the ship is moving - the direction of movement determines the position of the turning point. (I didn’t believe this at first, but it gets decisively proven at Grenoble). On a ship of 200 meters length this slight change of direction changes the lever arm of the thrusters significantly. One thruster is grinding away at the turning point, pretty much moving the whole ship and the other is working with a 160 meter lever. While docking a slight change in direction is common as the vessel is positioned at the instruction of the person spotting the ship. You can see how quickly the movement toward the dock will change if the tugs are not adjusted right away.
As to the poor initial turning performance of pilots on a car ship I sympathize completely. Most of the ships we handle have the conning station on the stern. This allows the pilot to easily judge the ship’s position in the channel and observe the rate of turn. The rate of turn is calibrated by following the foremast as is swings through the horizon. With a car carrier these tools are taken away. The pilot is in an unusual position with no view of the ship as it moves in the channel or a means to gage the rate of swing***. It takes a couple of turns, usually, to get a “feel” for the ship. I confess, I hated bridge forward ships. The only ships worse were those with a multitude of cranes - the last of which was stupidly placed directly in front of the bridge.
***This would be a good example of Poliany’s Paradox. What is the proper rate of swing for each turn? Doesn’t the ship have a swing meter for that? One of my good friends had a Navy ship inbound one time and the captain asked if one of the junior officers could conn the ship for a bit of the channel. They chose the turn around the Lynchburg Ferry area for the exercise. After an interval they asked the pilot to look over the navigation plan. They had plotted a series of small course corrections based on the bearing to a large tower. They explained that as the tower’s bearing changed the course would be adjusted accordingly. What did he think? He confessed that he had never seen it done that way. They asked how he did it and he said “I give her 10 degrees port rudder and if that’s not enough I put on more rudder. If we get to turning too fast I take off some rudder.” Poliany’s Paradox in a nutshell. He knew how to do it, but couldn’t explain in a way a layman would understand. The results were predictable. Much shouting of bearings and repeating. Officers huddled over the chart table. No one looking out the window. After a bit the pilot said “Captain.. you need to turn a little faster.” More bearings, more shouting and repeating. Another recommendation to turn a little faster. More of the same. Finally, unable to stand it any longer the pilot shouted “CAPTAIN, HARD PORT!” They finally looked up from the chart table and saw the cement dock a couple ship lengths away - dead ahead. Hard port did the trick but I know Leonard could never explain how he knew exactly how far he could let the experiment go before intervening.
Training for specialist navigation officers and hydrographic officers in the Royal Navy used to be of a years duration as a Lieutenant. The last 3 weeks was practical ship handling in an old destroyer (HMS Zest) and a fail resulted in failing the entire course. Various exercises consisting of simulating fast minelaying, transiting Scottish Locks at high speeds and manoeuvring under all conditions. The commanding officer was a captain, who had passed as a lieutenant with nerves of steel capable of recovering the situation.
If after two years the ship was not firmly part of some geographical feature he was given command of the Royal Yacht with Flag Rank guaranteed.
Almost always for mooring two tugs are used, when the aft mooring station reports the stern is closing too fast the pilot updates the command to the aft tug to correct the situation.
It’s just a matter of the bridge team focusing too much on the bow. When the officer on the stern is paying attention to the right thing, closing too fast is hard to miss. On the bridge it’s mostly a matter of what experience the pilot has. In ports that handle a lot of car ships it’s not an issue.
Exactly, the pilot is using direct perception (out-the-window) and the navy officers are using representational methods (chart or screen based). Direct perception is how I just got the kitchen and back without banging into anything.
