Sub ended sonar plots

WASHINGTON — WASHINGTON - Less than an hour before the submarine USS Greeneville slammed into a Japanese fishing trawler, a sailor aboard the Navy sub stopped plotting sonar contacts because he was distracted by civilians in the cramped control area, investigators with the National Transportation Safety Board said yesterday.

It was the first indication that the 16 civilians on board might have been a hindrance to the sub's crew as they prepared for a rapid-ascent drill. Still, both NTSB and Navy officials said they were not certain how significant the sailor's lapse was because the sub's crew had other means to track the Japanese boat.


NTSB investigators also said yesterday that sonar technicians on the Greeneville detected a surface vessel 71 minutes before the accident that sank the fishing boat, the Ehime Maru. The NTSB said the Navy later reconstructed the path of the Ehime Maru and determined that it was indeed the vessel that the sub had detected.

But for some reason - or a series of reasons - the Greeneville slammed into the trawler nine miles off Oahu after quickly rising to the surface from a depth of about 400 feet. The incident Feb. 9 left nine of the fishing boat's 35 passengers and crew missing and presumed dead.


A fire control technician on the Greeneville told NTSB investigators that with the aid of sonar readings, he had been penciling in the sonar contacts on a scroll-like piece of paper called the CEP, for Contact Evaluation Plot. The paper, which is marked on the bulkhead - or wall - of the submarine, serves as a quick reference point for officers trying to plot the location of the sub in relation to surface contacts.

But the sailor halted his task less than an hour before the accident because he was distracted by the civilian guests, investigators said.

"What he told us was, he stopped doing it because of all the civilians aboard, sometime within an hour before the collision," said Ted Lopatkiewicz, a spokesman for the NTSB.

'We're gathering data'

Investigators, who have not released the names of the crew members interviewed, have "no idea how significant" the lack of an CEP sonar report was, Lopatkiewicz said.

"We're still in the fact-finding phase of the investigation," he said. "We're gathering data; we're not analyzing it."

Navy officials who asked not to be identified said that even without a CEP, the sub's officers could determine the location of other vessels through the passive sonar screens or on the displays of the fire control computer.

The CEP sonar report "is just another reference of several in the control room," said one active-duty submariner. "It's only one - it's not the only - means of information."


It "is inconclusive at best," the submariner said. "The CEP can be good or not good. It depends on who's doing it and how many contacts you have."

Major lapse?

Each vessel is given a corresponding number, and the technician would keep track of its location and subsequent course, periodically updating it.

But Norman Polmar, a naval analyst and author, said he thought the lack of a CEP was a major lapse.

"You've got to have a good track when you're operating near anybody else, in case you change course or you or anyone else speeds up," Polmar said. "A sailor [shouldn't] stop doing anything on a nuclear submarine. He doesn't do anything without telling the officer of the deck or the captain. That's important."

At the same time, the NTSB said that one of the submarine's sonar repeaters - which track and record sonar contacts - was not operating at the time of the collision, though officers could have used another such display screen only a few steps away.


So far, the NTSB has interviewed 19 of the 130-sailor crew. None of the others interviewed said the civilians on board were a distraction, Lopatkiewicz said.

Cmdr. Scott Waddle, the skipper of the Greeneville; Lt. Cmdr. Gerald K. Pfeifer, the executive officer; and Lt. j.g. Michael J. Coen, who was the officer of the deck at the time, have declined to talk with the NTSB until the Navy completes its investigation.

Lopatkiewicz said the NTSB's investigation is expected to take about a year. And a rare naval court of inquiry into the collision is scheduled to begin next week in Hawaii, Navy officials said.

In the meantime, as the investigations proceed, Navy submarine commanders have been ordered not to conduct emergency rapid ascents with civilians on board.

Since the accident, the possible effect of the 16 civilians on the Greeneville, some of whom have donated money to the USS Missouri Memorial in Hawaii, has been one of the central questions. Navy officials have said that civilians were at two of the three watch stations before the sub's rapid ascent.

Closely monitored


One of the civilians pushed two levers to begin the process, and another was at the steering wheel in the helmsman's position, but both were closely monitored by the crew, Navy officials said.

Questions also have been raised about why periscope sweeps completed by the captain and a junior officer failed to detect the 180-foot Japanese vessel. Navy officials say that several visual problems could have contributed to their failure to detect the Ehime Maru.

The white fishing trawler, for example, might have been camouflaged or obscured by the backdrop of Oahu. The cloudy weather and 3- to 6-foot waves might have further hindered the periscope's scan. Moreover, Navy officials say they believe that the two vessels were heading either straight toward each other or in the same direction. In either case, the periscope might have picked up only the bow of the fishing boat, its most narrow profile.

Two other factors

Further, there is speculation that two other factors could have resulted in sonar problems. Some Navy officials say that if the sub was heading straight toward the Ehime Maru, its sonar might have been impeded by a phenomenon known as "bow null." That means that the sound of the fishing boat's engine in the rear would have been obscured by the boat's structure.

But one submariner said he doubted that this was a problem because the trawler had neither the cargo nor the steel mass that might have softened engine noise. Polmar, the naval analyst, agreed that such an effect was unlikely and noted that the fishing boat's propeller would certainly have made noise that the sonar could have detected.


Other Navy officials point to the possibility of a "thermal layer" - warmer water that could have trapped or slowed the sound of the trawler, making it harder to detect as the sub came perilously close.