NTSB Advisory
National Transportation Safety Board
Washington, DC 20594
March 2, 2001
USS Greeneville/Ehime Maru Collision Update
The National Transportation Safety Board is continuing its investigation of the
February 9, 2001 collision between the nuclear submarine, U.S.S. Greeneville,
and the Japanese fishing vessel Ehime Maru. Nine of the 35 persons aboard
the Japanese vessel, which sank after the collision, are missing.
The following is updated factual information documented by NTSB investigators
in Washington, D.C. since the departure of the Board's investigative team from
Hawaii on February 24.
The USS Greeneville was equipped with a sonar data logger that recorded
sonar data and "own ship" data once per second. Data for the accident were transferred
to a data tape (normally used for archiving data). This data tape is en route
to NTSB headquarters for analysis. However, the Navy has provided the NTSB with
a preliminary data file containing parameters extracted from this tape. Heading
and keel depth from this data file are plotted for a 10 minute period that includes
the collision in figure 1. The NTSB has not applied any instrument corrections
to these data.
- These data show the Greeneville ascending to an initial periscope
depth (uncorrected instrument readings ranged from 63 to 67 ft keel depth)
at about 23:38:30 UTC (1:38:30 Hawaii time).
- The Greeneville then ascends about 3 ft higher in the water (using
uncorrected instrument readings) about 1 minute later for a total time at
periscope depth of about 1 ½ minutes.
- This is consistent with witness statements.
- At 23:40 the Greeneville commences its descent from a heading of
120 deg. At about 23:41 the Greeneville begins a heading change to
port (left). She reaches a maximum depth of about 405 ft at 23:42 on a heading
of 028 deg.
- At 23:42:30 the Greeneville begins its rapid ascent to the surface
and collides with the Ehime Maru at about 23:43:20. At impact, the
Ehime Maru was on a heading of 166 deg while the Greeneville
was on a heading of approximately 018 deg.
Figure 1: Preliminary Greeneville Depth and Heading
Although the submarine's position was not recorded, it is possible to derive
the Greeneville's track from recorded heading, speed and pitch data.
Figure 2 shows this derived track with the radar track of the Ehime Maru.
- The plot shows the track of the Greeneville first heading South (light
blue) and then heading North (dark blue) toward the accident site.
- Prior to rising to periscope depth (shown in figure 1), the Greeneville
executes a series of turns.
- The plot shows only the last 18 minute segment of the radar track of the
Ehime Maru prior to the collision. Radar shows the Ehime Maru
was traveling 11 knots on a heading of 166 deg. This is consistent with the
statement of the ship's master.
- The plot then shows the Greeneville turn towards the Ehime Maru
shown in figure 1, the collision, and finally the Greeneville's return
to the accident site.
Figure 2: Preliminary Greeneville and Ehime Maru
Track
Figure 3 shows the radar track of the Ehime Maru and the last 15 minutes
of the derived Greenville track before the collision and the Greeneville's
return to the accident site on the surface in 3 dimensions. The surface dimension
is 2 ½ by 2 ½ nautical miles.
Figure 3: 3D view
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