The fatal collision between the USS John S. McCain and the tanker Alnic MC in August 2017 was caused by insufficient training, inadequate bridge operating procedures and a lack of operational oversight, according to findings released by the National Transportation Safety Board (NTSB).

Ten sailors aboard the John S. McCain died in the accident and 48 were injured when the ships collided in the Middle Channel passage of the Singapore Strait traffic separation scheme (TSS). There were no injuries to the crew of the Alnic MC.

The NTSB report said that the collision happened when the McCain, an Arleigh Burke-class destroyer with a crew of 280, and the Alnic MC, a Liberian-flagged chemical tanker carrying a partial load of cargo with a crew of 24, were transiting towards Singapore in the westbound lane of the Singapore Strait TSS. The Singapore Strait is one of the busiest waterways in the world, with more than 83,700 vessels of more than 300 gross tons transiting the strait in 2016.

The NTSB determined the probable cause of the collision was a lack of effective operational oversight of the destroyer by the U.S. Navy, which resulted in insufficient training and inadequate bridge operating procedures. Contributing to the accident were the John S. McCain bridge team’s loss of situation awareness and failure to follow loss-of-steering-emergency procedures, including the requirement to inform nearby vessel traffic of their perceived loss of steering. Also contributing to the accident was the operation of the steering system in backup manual mode, which allowed for an unintentional, unilateral transfer of steering control.

Accident timeline

The twin-propeller destroyer was on the outside (northern side) of the TSS lane, making a speed of about 18 knots and overtaking several slower commercial vessels that were also transiting westbound in the TSS. A single crew member was at the helm of the ship, controlling both steering and propeller thrust from the helm operator position at the ship control console (SCC), as ordered by an officer assigned to control maneuvering of the ship.

Damage to the USS John S McCain following the August 2017 accident. Source: U.S. Navy photo by Mass Communication Specialist 2nd Class Joshua FultonDamage to the USS John S McCain following the August 2017 accident. Source: U.S. Navy photo by Mass Communication Specialist 2nd Class Joshua FultonAt 5:20 a.m., the McCain's commanding officer, who was on the bridge, thought that the helmsman might become overwhelmed responding to steering and thrust commands as the ship maneuvered in the busy shipping lane. He ordered a second watchstander — a lee helmsman — to take over responsibility for controlling the ship’s propeller thrust.

Once the lee helmsman was in place, the controls for thrust had to be transferred from the helm station to the lee helm station on the SCC. The controls for each propeller had to be shifted one at a time, so the watchstanders began by transferring control of the port propeller at 5:21 a.m.

The NTSB said that soon after control of the port thrust had been transferred to the lee helm station, the helmsman reported that he had lost control of steering. Without steering control, he could not maintain the McCain’s heading and the vessel began to slowly turn to port. The loss of steering was announced over the destroyer’s public address system, and crew members moved to the vessel’s aft steering compartment while the bridge watch team attempted to regain control on the bridge.

About a minute later, according to the accident report, control of the starboard propeller thrust was transferred to the lee helm station. Soon after, the commanding officer directed the watch team to slow the ship. The officer of the deck ordered the speed reduced to 10 knots and then to 5 knots.

McCain crew members manned the aft steering compartment located near the stern of the ship, and after efforts to regain control of steering on the bridge failed, the aft steering watchstanders were ordered to take control. They took control, but control then shifted back to the bridge without explanation.

MV Treasure carries the USS John S. McCain in the Singapore Strait. Credit:Capt. Keith Lehnhardt, director of Supervisor of Salvage and Diving  MV Treasure carries the USS John S. McCain in the Singapore Strait. Credit:Capt. Keith Lehnhardt, director of Supervisor of Salvage and Diving After some confusion, the aft steering watchstanders retook control of steering. While the McCain’s crew worked to regain steering, the destroyer’s speed progressively decreased while its rate of turn to port increased, bringing the ship across the TSS lane in an increasingly tighter turn.

Meanwhile, the tanker Alnic MC was transiting in the westbound lane of the TSS, about a third of a mile off the destroyer’s port side. The single-propeller tanker was making a speed of about 9.5 knots. The master of the Alnic MC, who had control of maneuvering of the ship, noted the John S. McCain as it began its turn to port and initially assumed that the Navy ship would pass between his vessel and another vessel ahead of the Alnic MC.

As the destroyer continued to turn into the path of his ship, he became increasingly concerned. At 05:23 a.m., he moved the Alnic MC’s engine order telegraph from full ahead to half ahead to slow his vessel.

Once positive control of the McCain’s steering was reestablished in aft steering, watchstanders moved the rudders to 15° to starboard, as ordered from the bridge. However, this action and the action of the Alnic MC master to slow his vessel were not enough to prevent a collision, and at 05:23:58 a.m., the bulbous bow of the tanker struck the port side of the John S. McCain.

The impact breached the hull of the John S. McCain in a berthing compartment where crewmembers were sleeping, killing 10 sailors. About three minutes had elapsed between the reported loss of steering on the John S. McCain and the collision.

Probable cause

The NTSB concluded that during the process of shifting thrust control, a watchstander unintentionally transferred control of steering from the helm to the lee helm station, which resulted in a perceived loss of steering by the McCain’s helmsman. However, steering control was available at all times in the accident sequence. The NTSB further concluded the unintentional transfer was possible because the system was being operated in backup manual mode, which removed a safeguard against inadvertent transfer of steering control.

The USS John S. McCain in the South China Sea. Source: Navy photo by Navy Petty Officer 3rd Class James VazquezThe USS John S. McCain in the South China Sea. Source: Navy photo by Navy Petty Officer 3rd Class James VazquezThe NTSB also concluded in its report that the inability to maintain course due to a perceived loss of steering, the mismatch of port and starboard throttles producing an unbalanced thrust, and a brief but significant port rudder input from aft steering combined to bring the John S. McCain into the path of the Alnic MC. The decision to change the configuration of the McCain’s critical controls while the destroyer was in close proximity to other vessels increased the risk of an accident, according to the NTSB’s report.

Based upon its investigation, the NTSB issued seven safety recommendations to the U.S., Navy including ensuring design principles in ASTM International Standard F1166 are incorporated when modernizing complex systems such as steering and control systems within the integrated bridge and navigation system.