Classification
| Field | Value |
|---|
| Incident Type | Grounded |
| Severity | Low |
| Investigation Body | United States Navy |
Vessel Details
| Field | Value |
|---|
| Vessel Name | USS Antietam |
| Vessel Names | USS Antietam |
| Vessel Type | Naval / Military |
| Flag State | United States [US] |
| IMO Number | |
| Gross Tonnage | 9800 |
| LOA (m) | 173 |
| Breadth (m) | 16.8 |
Incident Details
| Field | Value |
|---|
| Date | 2017-01-31 |
| Region | Japan |
| Location | Tokyo Bay, Japan, Anchorage A-10 |
| Coordinates | 35.4700, 139.8477 |
| Fatalities | 0 |
| Injuries | 0 |
| Missing | |
| Direct Damage | |
| Economic Damage | USD 4.2 million |
Key facts
- USS Antietam was conducting a sea-and-anchor evolution in Tokyo Bay with Anchorage A-10 as the intended position.
- The ship passed the intended anchorage by about 60 yards and continued toward shoal water.
- The commanding officer delayed decisive engine use while attempting to recover the anchoring evolution.
- Bridge and combat information centre watchstanders did not provide effective forceful backup, and communications were degraded after the Net 15 speaker was turned down.
- The Navy investigation found the grounding preventable and reported about USD 4.2 million in material repair costs.
Narrative
On 31 January 2017, USS Antietam was preparing to anchor at Anchorage A-10 in Tokyo Bay, Japan. The anchoring plan did not adequately account for prevailing wind and current, and the bridge team did not maintain a reliable assessment of the ship's movement as it approached the assigned position. Antietam passed the intended anchorage by about 60 yards and continued toward shoal water. The commanding officer delayed decisive use of the engines while attempting to recover the evolution, and the ship grounded at 09:53 local time. The investigation found that the bridge and combat information centre teams did not provide effective forceful backup. Watchstanders observed the developing danger, but no one clearly and urgently stated that the ship was standing into unsafe water. Communication between CIC and the bridge was degraded after the commanding officer turned down the Net 15 speaker in the pilot house. The command investigation identified human error as the primary cause, including failure to account for wind and current during planning and execution. It also documented that the navigator was not qualified as Officer of the Deck, the navigation planning checklist was incomplete, the ship did not have a qualified navigator on board as required and the anchoring evolution was not included in the superior command's navigation assessment. No injuries were reported. Material repair costs were estimated at about USD 4.2 million. Recommendations included revising navigation and anchoring instructions and adding anchoring evolutions to future navigation assessments.
Sequence of events
| Date/time | Event |
|---|
| 2017-01-31 before 09:53 | USS Antietam approached Anchorage A-10 while conducting the sea-and-anchor evolution. |
| 2017-01-31 before 09:53 | The ship passed the intended anchorage by about 60 yards and continued toward shoal water. |
| 2017-01-31 09:53 local | USS Antietam grounded in Tokyo Bay. |
| After the grounding | The command investigation estimated material repair costs at about USD 4.2 million. |
Contributing factors
| Factor | Evidence status | Description |
|---|
| Failure to account for wind and current | Confirmed finding | The anchoring plan and execution did not adequately account for environmental forces. |
| Delayed engine use | Confirmed finding | The commanding officer delayed decisive engine action after the ship passed the intended anchorage. |
| Weak bridge and CIC forceful backup | Confirmed finding | Watchstanders did not clearly and urgently state that the ship was standing into danger. |
| Degraded bridge-CIC communication | Confirmed finding | Turning down the Net 15 speaker reduced the bridge team's access to CIC information and warnings. |
| Incomplete navigation planning and qualifications | Confirmed finding | The checklist was incomplete, the navigator was not qualified as Officer of the Deck and the anchoring evolution was omitted from the higher command assessment. |
Investigation
The United States Navy command investigation concluded that the grounding was preventable and ultimately the responsibility of the commanding officer. It identified human error as the primary cause and documented planning, qualification, communication and forceful-backup failures that compounded the casualty. The report recorded no fatalities or injuries and estimated about USD 4.2 million in material repair costs. Recommendations included updates to the Navigation Bill and Anchoring Bill and inclusion of anchoring evolutions in future navigation assessments.
References
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