Lake Erie Collision: Motor Yacht Strikes Unseen NOAA Uncrewed Surface Vessel

Briefing on the NTSB report MIR-26-32 into the NOAA USV collision on Lake Erie, when a 45 ft (13.7 m) motor yacht struck a small uncrewed surface vessel (USV) that nobody on board had seen.

What Happened:

On 10 August 2024, at about 1912 LT, the Prestige 450 Flybridge recreational vessel struck a NOAA uncrewed surface vessel on Lake Erie. The collision happened about 6 miles (5.2 NM) east-southeast of Monroe, Michigan. The USV was a SeaTrac SP-48, less than 16 ft (4.9 m) long, run by NOAA’s Great Lakes Environmental Research Laboratory. It was sampling the lake for toxins from algal blooms.

The USV was in “adapted hold” mode. This kept it circling slowly within 150 ft (46 m) of a sampling site. Its automatic collision avoidance was switched off because it was still being tested. One pilot, an engineer, watched it from home through a dashboard and alerts. He checked it every 20 to 30 minutes. The hull was yellow, but dark solar panels covered most of the deck. It sat only about 1 ft (0.3 m) above the water. It had lights and Class B AIS, but no radar reflector and no sound signal.

The yacht was heading home at about 22 kts. The owner was hand steering, with one passenger on board. The sun was low on the starboard side. The wind was westerly at 18 kts, with waves of about 3 ft (0.9 m). The radar dome was folded down, so the radar was not available. The yacht had no AIS. The owner said there was nothing ahead. The yacht hit the USV, which fouled the starboard propeller pod. The yacht heeled hard. The owner, who was operating the vessel, was thrown to the deck and suffered a minor foot injury. The USV was a total loss, estimated at $186,000. Damage to the yacht was about $100,000. The NTSB found that the USV was too hard for other vessels to detect in that area. It also found that nobody was actively watching it, so it had no proper lookout.

Immediate Operational Checks:

Officers taking the watch today should check the following:

• Lookout into the sun: Give extra attention to the sector with sun glare. Use polarised glasses and reduce speed if you cannot see clearly ahead (COLREGs Rules 5 and 6).
• Radar ready: Keep the radar running and tuned for small targets whenever you are underway. A folded or switched-off set gives no warning at all (Rule 7). This is mandatory.
• Expect uncrewed craft: Check local notices and safety bulletins for USV operations in your area before sailing. Treat any small, low object as a possible vessel or hazard until you know otherwise.
• Use every source: Watch AIS and the chart plotter as well as looking out of the window. A USV may show on AIS when you cannot see it by eye or on radar. Use overlays! If your radar can show AIS targets as well, TURN IT ON. It helps you find small targets, or targets hidden in rain clutter, or radar blind spots. AIS is a great aid to situational awareness.
• If you operate USVs: Test that your craft can be seen by eye, radar, AIS and sound in the real conditions it will meet. Make sure a person is actively watching it whenever other traffic may be near.

Lessons Learned:

• Being lit is not the same as being seen: The USV carried lights and a yellow hull. But its small size, low freeboard and dark deck made it very hard to spot in waves and low sun. A vessel that cannot be seen cannot be avoided. Operators must test how visible their craft really is to the boats that use the area, and fix it before launch. Use radar reflectors.
• Passive monitoring is not a lookout: The pilot checked the USV every 20 to 30 minutes from home. In hold mode the USV could not make its own navigation decisions. So for long periods nobody was keeping a lookout, which Rule 5 requires at all times. Match the level of monitoring to the craft’s true autonomy, the traffic and the mode of operation.
• Electronic aids only work if both sides use them: The USV sent AIS, but the yacht had no AIS receiver. The USV had no radar reflector, so the report found it would likely not have shown on radar. It had no sound signal, which the Inland Rules require for a vessel of its size. USV operators should not assume AIS makes them visible to small craft. Fit every aid that helps others detect you.
• Standards lag behind the technology: At the time there was no national standard for how visible a USV must be in US waters. The NTSB has asked the Coast Guard to set one, and NOAA to test and monitor its USVs. Until rules catch up, watchkeepers should expect small, quiet and unusual craft in open water.

See also our briefing on the collision between a passenger ship and a pleasure craft on the St. Lawrence River.

Tags: Collision, Autonomous Shipping, Lookout, Pleasure Craft, COLREGs

Official Report

Read the full safety report here: Collision Between National Oceanic and Atmospheric Administration Uncrewed Surface Vessel and Prestige 450 Flybridge Recreational Vessel (MIR-26-32)