 Sub captain chooses silence
Court of inquiry's admirals bring broad range of expertise
Case presents unusual challenge for interpreters
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By Dave Moniz
USA Today
WASHINGTON — In trying to unravel the mystery of how the USS Greeneville rammed a large Japanese fishing vessel, the Navy likely will focus on whether the submarine raised its periscope high enough or spent too much time submerged before the deadly collision Feb. 9, submarine experts say.
Interviews with former submariners offer revealing clues as to how the high-tech submarine could have missed seeing or hearing the 174-foot, 499-ton Ehime Maru. On Thursday a Navy court of inquiry will begin trying to answer that question.
The Japanese ship sank in 2,000 feet of water within 10 minutes of the collision, which occurred about 10 miles south of O‘ahu. Nine of the ship’s 35 passengers and crew are missing and presumed dead.
The maneuver that led to the accident, an "emergency blow," is not risk-free. By filling their ballast tanks with compressed air, subs are able to practice a rapid rise to the surface in case of a real crisis. But the ascent is irreversible once initiated. That’s why it is crucial that the sub conducts thorough periscope and sonar sweeps before surfacing. Submarines are required to practice the maneuver at least once a year, but typically do it three to four times a year, Navy officials say.
Visibility, which the Coast Guard estimated at 5 miles, should not have been a problem for the Greeneville. That range was acceptable for performing an emergency blow, experienced Navy officers say.
Still, the crew apparently failed to spot the Ehime Maru on any of several 360-degree periscope sweeps made before the submarine began to descend 400 feet to prepare for its ascent, according to both Navy sources and civilians aboard the sub at the time.
If the Ehime Maru was traveling at 11 knots, as its captain reported, and the Greeneville conducted the emergency blow within the typical 10- to 15-minute window, experienced submariners say, the fishing ship had to have been within the Greeneville’s periscope range.
The big question: How could the sub fail to detect such a ship?
Naval experts offer several possibilities:
 The Greeneville’s 360-degree periscope sweep was flawed. The court of inquiry is certain to ask the sub’s officers whether they performed a "high look" periscope maneuver. At the time of the collision, the Coast Guard reported swells of about 8 feet, which suggests that normal periscope height might not have been sufficient.
A high look is achieved by raising the submarine several feet closer to the surface than normal periscope depth, about 60 feet down. The extra 4 to 8 feet in periscope height could make a significant difference in spotting nearby ships.
Submarines constantly record the depths at which they operate, so investigators should be able to determine whether the Greeneville performed a high look.
The white-painted Ehime Maru, filled with crew members, instructors and Japanese students learning fishing, might have been more difficult to spot on a cloudy day, veteran submarine officers say. It was cloudy at the time of the collision.
The emergency blow took considerably more than 15 minutes to complete. Commanders are required to conduct visual searches by periscope and sound detection with sonar before beginning the maneuver. If the emergency blow is not performed in a timely manner, the submarine could hit a ship that had cruised into the sub’s surfacing area.
This is one area where the Navy will try to determine whether 16 civilians aboard the Greeneville could have interfered with the crew’s focus or slowed its response time. In the past week, civilian passengers aboard the Greeneville, including two seated at the sub’s controls, have said the crew was not distracted by their presence.
The O‘ahu coastline could have obscured a clear view of the fishing vessel. "If you’re sweeping with the periscope and looking toward Diamond Head, that’s where the Honolulu hotels could come into play," said retired Navy Capt. Dana Roberts, a former submarine commander. "If there was any kind of haze and visibility problem, he might have mistaken the ship for something on the beach."
That might be especially true if the Ehime Maru, its white paint blending into coastal buildings, was moving directly toward the Greeneville. Its profile would have been dramatically smaller than a ship presenting a broadside view.
Sonar alone is not reliable for tracking ships. It can be difficult to distinguish between an approaching vessel and other noises, from crashing waves to movements in a busy harbor. Water temperature also can distort sonar signals.
That’s why a 360-degree periscope sweep, performed several times at low and high magnification, is crucial to ensure that no vessels are nearby, Roberts said.
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