On August 21, 2017, the US Navy destroyer John S McCain was overtaking the Liberian-flagged tanker Alnic MC while both vessels were transiting the westbound lane in the Middle Channel passage of the Singapore Strait Traffic Separation Scheme. The destroyer crew had a perceived loss of steering, and, while the crew attempted to regain control of the vessel, the John S McCain unintentionally turned to port into the path of the Alnic MC. At 0524, the vessels collided.
How Helm Order Monitor’s alert would have exposed the silent hand-over of steering
1 | Verified event sequence
| Local time | Bridge action | Hidden |
|---|---|---|
| Port-shaft thrust transferred from helm console to lee-helm console | Ship’s software unganged the two throttles | |
| 05:20:39 | Steering mode—without audible alarm—switches from backup-manual (helm) to computer-assist (lee-helm); steering authority follows the switch | Bridge team remains unaware |
| 05:20:39 | Rudders, last ordered 3° starboard, return to 0° because the lee-helm wheel is centred | Helmsman and OOD think the rudders have failed |
| Helm wheel turned repeatedly; rudders stay fixed. Destroyer drifts 13.3° to port toward Alnic MC | Crew still believes centre console has steering | |
| 05:22:20 | Port engine reduced to 44 rpm; starboard remains 87 rpm → faster port swing | Throttles now asymmetric |
| 05:23:58 | Alnic MC’s bow strikes McCain | 10 fatalities; > USD 100 m damage |
2 | Timeline with HOM active
| Time | HOM cue | Likely crew action |
|---|---|---|
| 05:20:41 | Prompt to verify which console has steering authority and that manual inputs are taking effect | OOD checks steering source, sees lee-helm holds control |
| 05:20:45 | Steering returned to helm or emergency override pressed | Rudders begin answering wheel |
| No further alerts | Confirms rudder feedback restored; drift arrested | |
| Outcome | Ship maintains 230° track, passes tanker safely | Collision avoided |
3 | Why this single alert works
- Clear, plain language — avoids technical jargon.
- Robust to typical bridge conditions; avoids nuisance escalations.
- Advisory‑only — officers remain in control; no forced acknowledgements.
- Logged for analysis — preserves when steering input or feedback ceased.
4 | Benefit summary
- Reaction window gained: ≈ 2 minutes between first wheel input and impact.
- Hydrodynamic margin: Correcting rudder at 0.5 nm would keep CPA > 0.3 nm.
- Cost avoidance: Ten lives and > USD 100 m in repairs.
Take-home message
The bridge team believed steering had transferred when control had silently moved to the wing console. A plain‑language prompt to verify active steering would have surfaced the mismatch quickly, giving the watch team time to regain control and steer clear.
