Every vehicle crosses the ramp's load cells on the way aboard and is logged to a lane, and the trim computer reads the ship's tanks and its heel and says whether the load is balanced. On the last sailing each night the ramp logs a fourteen tonne vehicle into lane 4 after the deck is closed, and the ship heels to port by the amount fourteen tonnes in lane 4 would heel it.
I am the chief officer, and the loading is mine.
How the deck is loaded.
Vehicles come up the ramp one at a time over a weighbridge in the ramp itself, and each one is logged to the lane the loading officer sends it to. The trim computer takes the lane weights, the tank soundings and the heel sensor, and shows the ship's condition, and I sign it before we sail.
When the deck is closed the ramp is raised and nothing else can come aboard, because the ramp is the only way.
On the last sailing each night, after the deck is closed and the ramp is up, the ramp's weighbridge logs a vehicle.
Fourteen tonnes, which is a loaded lorry, assigned by the system to lane 4, the outboard port lane, which at that point in the loading is usually the lane with space at the after end.
And the heel sensor shows the ship take a list to port of the size fourteen tonnes in lane 4 would give her, and the trim computer, which I have already signed, shows a condition I did not sign.
Lane 4 is empty at the after end. I walk the deck before the ramp goes up and I have walked it after the log entry, on the same night, and the space is space.
The ship is heeled. The pumps correct it, as they are set to, by moving ballast, and the ballast log shows the transfer.
What has been checked.
The weighbridge. Calibrated with a test vehicle, and its log verified against the port's own weighbridge for a week: every real vehicle agrees to within a hundred kilos. The night entry has no matching vehicle at the port.
The ramp. Up and locked, with the indicator on the bridge and a camera on it. The camera shows the ramp up while the log shows fourteen tonnes crossing it.
The heel sensor. Two of them, one the ship's and one a portable from the surveyor, both showing the list arriving at the moment of the log entry, over about a minute, the way a list arrives when a heavy vehicle drives to its place and stops.
And the ballast. The ballast pumps move water to correct the list, and they move it, and the tanks show it, and the ship sails level, carrying fourteen tonnes on the port side that is not on the deck.
The discharge.
At the far port the ramp goes down and the deck unloads over the same weighbridge, and every vehicle that came aboard goes ashore and is weighed off.
The fourteen tonnes does not go ashore. It is not weighed off. The trim computer shows the ship, after discharge, still carrying it in lane 4, and the ballast still compensating, until the ship berths for the night, at which point, between midnight and one, the heel sensor shows the list come off, over a minute, the way a list comes off when a heavy vehicle drives away, and the ballast pumps run to correct the other way.
Something drives off my ship, over a raised ramp, in the middle of the night, at the far port, and my ship feels it go.
What is done about it.
The trim condition on the last sailing is signed with the fourteen tonnes in it, as a known discrepancy, and the ship is stable with it in, because fourteen tonnes on a ship this size is inside the margins, and the surveyor has seen the logs and has written that the vessel's stability is not compromised by the recurring anomalous load entry.
What I do.
I load the ship.
The one thing I have changed is that lane 4 is loaded last and lightly, and the after end of it is left clear.
That started after the night I loaded it full, deliberately, to the last metre, with a lorry in the after space, and the ramp still logged fourteen tonnes aboard into lane 4 after closing, and the heel came on, and in the morning at the far port the lorry driver in the after space told the loading officer, without prompting, that something had been parked against his tailgate all night, close enough that he could not open it, and that he had heard its engine idling, and that when he went down at five there was nothing there.