ECDIS errors

Poor bridge management and an extraordinary chart omission contributed to a ship hitting an out of service, yet highly conspicuous, oil and gas platform in the Gulf of Mexico. 

In January 2021, the 623ft (190m) bulk carrier Ocean Princess struck a disused oil and gas production platform in the waters of the Gulf of Mexico, 24 miles off the Louisiana coast. 

No pollution or injuries were reported, but the total damage to the two assets was $1.5m.

The 162ft (49m)-long three-deck platform — SP-83A — was painted bright orange, sported eight flashing warning lights with two-mile visibility, and rose 73ft (22m) above the surface. 

Overnight drifting 

The day before, Ocean Princess had left a New Orleans wharf after discharging its load of steel and magnesium, then headed out into the Gulf of Mexico to drift overnight as its crew cleaned the holds in readiness for a return to the wharf next morning for a load of grain. 

Once the master had directed the vessel to the area in which it would drift, the engine was stopped and he left the bridge to rest, turning the conn over to the chief officer with instructions to have the engine ready for manoeuvring within 15 minutes, if required. 

When the master returned five hours later, he and the second officer used the S-band/10-cm radar and ECDIS (electronic chart display and information system) for contact detection. 

For half an hour, up to just moments before the incident, the ship’s simplified voyage data recorder (S-VDR) captured the master engaged in, what accident investigators from the USA’s National Transportation Safety Board (NTSB) would later describe as, a “mostly one-sided conversation about non-navigational, non-pertinent matters” with the second officer. 

During that time, the master noticed a dim yellow light ahead. He looked at the radar and ECDIS but decided that the light must be coming from an oil platform five miles away. The second officer used binoculars to investigate the light but could not tell how far off it was. 

As the ship’s engine was increased to half ahead, the master noticed multiple flashing lights and realised something was now close to his ship’s bow. Running out onto the starboard bridgewing he ordered the rudder hard to starboard and the engine full ahead.

Moments later Ocean Princess’ starboard bow struck SP-83A at four knots. The master ordered the rudder midships, stopped the engine, and sounded the emergency alarms.  

Credit: Shipspotting.com

Anchor snagged

For the next hour, the crew tried in vain, to steer away from SP-83A using various combinations of rudder and speed. They would eventually realise that during the collision Ocean Princess’ starboard anchor had become deeply entangled to the platform. 

As soon as daylight arrived, the master ordered the crew to cut the starboard anchor chain and cast off the anchor with 10.75 shots (967ft) of the chain. The vessel then transited to a nearby anchorage to assess the damage and wait on further instructions from the company.  

Extensive damage

The Ocean Princess sustained extensive damage to its starboard bow, starboard-side handrails and starboard anchor windlass and bulwark. The forward mast was also knocked down and there was significant damage to the portside handrails. Estimated cost: $500,000. 

The SP-83A platform, meanwhile, sustained extensive damage to its ladders, walkways and piping installations on three of its four sides. Estimated cost: $1 million. 

The SP-83A platform sustained an estimated $1 million damage. Credit: NTSB.com

Report findings 

The recently published accident investigation report by the NTSB has determined that the probable cause of the collision between the ship and the platform was poor bridge resource management, which resulted in the bridge team not identifying the platform or recognising the risk that it posed — even though they saw its lights ten minutes before the incident. 

However, the investigators also discovered that, at the time of the incident, SP-83A was not actually marked on the official US paper or electronic navigation charts which provided the data to Ocean Princess’ ECDIS. The SP-83A platform did, though, appear on the UK Admiralty paper chart that was being used by the crew on the ship’s bridge at the time of the collision. 

An audit revealed that SP-83A was originally added to the US paper charts when it was installed in 1990, but for “unknown reasons” was omitted in 2010, remaining off the paper and electronic navigation charts (ENCs) for the next eleven years — until after the collision. 

The NTSB investigation report goes on to point out that the effective use of all available resources by a bridge team — including paper charts, electronic charts, and radars — will increase their collective situational awareness and contribute to a safe navigation watch. 

When identifying hazards, it says, bridge teams should avoid an over-reliance on any single data source by cross-checking information with other bridge resources and communicating any identified risks with fellow watch-standers to ensure that a shared mental model exists.  

Read the full NTSB accident investigation report. 

Dennis O’Neill is a freelance journalist specialising in maritime.