With only a few more minutes to analyze data, crewmen aboard the USS Greeneville probably would have realized a fishing trawler was dangerously close and acted to avoid a deadly collision, a sonar supervisor testified Friday.
Petty Officer 1st Class Edward McGiboney told a Navy court of inquiry that a lack of time to perform a proper sonar analysis contributed to the Feb. 9 sinking of the Ehime Maru.
"Why didn't you hear this guy?" demanded Vice Adm. John Nathman, one of three admirals presiding over the inquiry.
"I don't think we had enough time," McGiboney replied.
The Greeneville was demonstrating a rapid-surfacing drill for 16 civilians when it surfaced beneath the Ehime Maru, tearing into its stern and sending it plunging to the ocean floor. Nine people, including four teenagers on an expedition to learn commercial fishing, were killed.
The inquiry has zeroed in on two key factors: whether Greene-ville Cmdr. Scott Waddle, with his ship running behind schedule, rushed preparations for surfacing and whether he failed to look long enough or high enough to detect the Ehime Maru during a periscope search.
About 20 minutes before the accident, Greeneville performed a series of high-speed maneuvers as a demonstration for the guests. Sonar data during that drill is unreliable, looking much like "spaghetti," McGiboney said. "You've got lines in all directions."
In preparation for rising to periscope depth, the submarine then conducted two turns intended to allow the sonar system to reset itself and begin obtaining good data once more.
That procedure, called "target motion analysis," typically requires 10 minutes with the submarine on a steady course, speed and depth to obtain an accurate picture of the location of surface vessels. The Greeneville performed the maneuver for six minutes, holding steady for even less time, according to testimony.
At the time, the Ehime Maru was moving toward the submarine at a bearing rate of 6 degrees per minute, which is considered a high rate.
Sonar did not know the boat was close, however, because the system didn't have enough time to reset and begin getting good data, McGiboney said.
"It should have just jumped off the screen," he said.
The inquiry will help decide the fate of Waddle; Lt. Cmdr. Gerald Pfeifer, the executive officer; and Lt.j.g. Michael Coen, the officer of the deck. They could face anything from a reprimand or discharge to courts-martial.
The court will forward recommendations to Adm. Thomas Fargo, commander of the U.S. Pacific Fleet, for final action.