Before dawn on 21 August 2017, the destroyer John S McCain was heading west through the Singapore Strait, one of the busiest waterways in the world, on its way to a port call. It was making about 18 knots and overtaking slower ships. A single sailor at the helm was handling both steering and the speed of the two propellers.
About 5:20, according to the National Transportation Safety Board, the commanding officer thought the helmsman “might become overwhelmed” by steering and speed orders in the crowded lane. He ordered a second sailor, the lee helmsman, to take over the propellers.
On this ship, that meant transferring control on a touch screen, one propeller at a time. Soon after the port propeller moved to the lee helm station, the helmsman reported that he had lost steering. Nothing had failed. At nearly the same moment, steering control had also shifted to the lee helm station, most likely from that station, the NTSB concluded. In the mode the crew was using, any station could take steering on its own, with no action at the helm. The screens showed the change; none of the three sailors handling the controls recognized it. The ship began turning left. When the ship was ordered to slow, the lee helmsman believed the two throttles were linked. The transfer had unlinked them, the touch screen gave no feel for it, and only the port propeller slowed. The uneven thrust tightened the turn. Control passed to the steering room at the stern, then back to the bridge “without explanation,” then back to the stern.
At 5:24, about three minutes after the first report of lost steering, the tanker Alnic MC struck the destroyer’s port side, breaching a compartment where sailors were asleep. Ten were killed and 48 injured.
The NTSB found “a broad lack of knowledge and understanding” of the steering system. Five of the bridge watchstanders believed an emergency override button sent steering to the stern; it actually took control at the helm. The lee helmsman said he hadn’t known steering could be shifted to his station at all. Only the officer of the deck described the system accurately to investigators. The lee helmsman and the boatswain’s mate of the watch had come over on temporary assignment from a cruiser without the system; the boatswain’s mate was qualified on the day of arrival, without instruction under way. The written procedures didn’t cover transfers between bridge stations. The design, the board added, “increased the likelihood of the operator errors,” with throttle transfers that were “unnecessarily complex.”
The watchstanders were also acutely fatigued, the NTSB found. The 14 people on the bridge averaged just over 4.9 hours of rest in the previous 24 hours; the lee helmsman hadn’t slept the night before. Two weeks after the collision, the Government Accountability Office told Congress that 37 percent of the warfare certifications for cruiser and destroyer crews based in Japan, where the McCain was homeported, had expired, and that across the Navy some sailors were working over 100 hours a week.
The NTSB put the probable cause on the Navy’s oversight, which led to insufficient training and inadequate procedures. Among its recommendations: build complex systems like this one to the marine industry’s human-engineering standard, which calls for simplicity and controls that can be identified by touch.