By Christopher Munsey
Navy Times Staff Writer

The Japanese vessel sunk in a collision with the USS Greeneville was dangerously close just before the accident and should have been detected by periscope and sonar, an analysis by the National Transportation Safety Board indicates.

The Feb. 9 collision off Oahu, Hawaii, occurred as the submarine practiced an “emergency main ballast blow,” a maneuver to bring the sub rapidly to the surface. The NTSB reported Friday that less than 3 1/2 minutes elapsed between the time the USS Greeneville dived from the surface and the moment it hit the Ehime Maru, indicating that the Japanese ship could not have been far away when the submarine began its dive.

The NTSB analysis was developed through a sonar record kept by the submarine.

As it prepared to return to Pearl Harbor after a daylong exercise and VIP tour Feb. 9, the Greeneville ascended to an initial periscope depth at 1:38:30 p.m. local time.

One minute later, the submarine rose 3 feet higher at periscope depth, presumably as the officers in the control room visually swept the horizon for any sign of surface traffic.

All told, the submarine spent about 90 seconds at periscope depth.

At 1:40 p.m., the Greeneville dived. It reached a maximum depth of about 405 feet at 1:42 p.m.

Thirty seconds later, the submarine started its “emergency main ballast blow” rapidly emptying its ballast tanks and filling them with high-pressurized air.
Traveling 405 feet in fifty seconds, the Greeneville burst onto the surface and slammed into the Ehime Maru, which was carrying 35 students, teachers and crewmembers.

The fishing trawler, a hole ripped in its hull, sank within several minutes. Twenty-six people abandoned ship and were rescued; nine — including four students — have never been found.

The Navy’s Court of Inquiry examining the accident convenes March 5 in Pearl Harbor.