E PLURIBUS UNUM

NATIONAL TRA SPORTATION

B OAR D

SAFE T Y

N

National Transportation Safety Board 

Washington, D.C. 20594 

Marine Accident Brief

Accident No.: DCA-01-MM-022 

Accident Type: Collision 

Time and Date: 1343 Hawaiian standard time (24-hour clock), February 9, 

2001 

Location: Pacific Ocean 9 miles south of Oahu, Hawaii 

Vessel Particulars: 

Name Greeneville Ehime Maru

Type Fast-attack nuclear submarine Fishing and training vessel 

Length 362 feet (110.3 meters) 190.9 feet (58.18 meters) 

Depth 32.3 feet (9.9 meters) 12.8 feet (3.90 meters) 

Beam 33 feet (10.1 meters) 30.5 feet (9.30 meters) 

Tonnage 6,330 tons surfaced; 7,177 tons 

submerged (displacement) 

741 (gross) 

Propulsion Nuclear reactor, steam turbine, 

gear driven 

Single screw, medium speed diesel 

engine driving a 4-blade, high-skew, 

variable-pitch propeller 

Built 1996 by Newport News 

Shipbuilding, Inc., Newport 

News, Virginia 

1996 by Shin Kurushima Dockyard 

Company, Ltd., Tokyo, Japan 

Owner/Operator U.S. Navy Ehime Prefecture, Japan 

Persons on board Crew 106 

Civilians 16 

Chief of Staff, COMSUBPAC 

Crew 20 

Students 13 

Teachers 2 

Injuries None 9 fatal 

1 serious; 9 minor 

Vessel damage $1.44 million $8.8 million (total loss) 

Other costs Recovery of Ehime Maru ($60 million) and compensation ($2.67 

million) to Ehime Prefecture for lost equipment and cargo, crew salaries, 

Japanese response effort, mental health care for survivors, and memorial 

services for accident victims 

 NTSB/MAB-05/01 
Accident DescriptionÜ

Route of the Ehime Maru

About 1200 local time on February 9, 2001, the Japanese fishing and training 

vessel Ehime Maru (figure 1), with 20 crewmembers, 13 students, and 2 teachers on 

board, departed pier 9 in Honolulu, Hawaii, en route to fishing grounds about 300 

nautical miles south of Oahu. The area weather predictions for the day included a coastal 

waters forecast advising caution for the waters south of the islands from Kauai to Maui 

because isolated thunderstorms to the east were generating strong, gusty 15- to 20-knot 

winds, which, in turn, were producing waves of 8 to 12 feet.1

Figure 1. The Japanese fishing vessel Ehime Maru, built in 1996, provided fisheries and 

engineering training to high school vocational students. (Ehime Prefecture photo) 

The Ehime Maru was in the middle of a 74-day training voyage that had 

originated in Japan on January 10. During the vesselís 1-day stopover in Honolulu, its air 

conditioning system was repaired. 

 

Ü Statements of individuals in this report are based on testimony at the Navyís court of inquiry (see 

http://news.findlaw.com/hdocs/docs/greeneville/ussgrnvl041301rprt.pdf) and interviews with Safety Board 

investigators as listed in appendix A. Other information was obtained from a recorder on the submarine that 

captured various system data and from shoreside radar. 

1

 A senior Coast Guard official testified that the February 9 situation report for the area indicated that 

the winds were 10 knots, the seas were 3 to 4 feet, the visibility was 6 miles, the air temperature was 78° F, 

the water temperature was 77° F, and the day was slightly overcast. 

 2 NTSB/MAB-05/01
The Ehime Maruís master had been a mariner for 40 years, 19 years on 

commercial fishing vessels and 21 years on various generations of the Ehime Maru. He 

had been a master for 8 years and the commander of the Ehime Maru since it was 

commissioned in 1996. He said that when the Ehime Maru left Honolulu on February 9, 

the vessel and its equipment were operating properly. He further stated that, in 

preparation for the voyage, one of the vesselís two radar sets2

 was turned on about 30 

minutes before getting under way. The pilot who directed the Ehime Maru from the pier 

to the sea buoy confirmed that the vesselís radar was energized while he was on the 

bridge. After leaving the harbor, the radar was set to the 12-mile scale. 

The master said that the Ehime Maru traveled at 6 knots or less for about a half 

hour while the crew hoisted the anchor to its stowed position. After the anchor was 

secured for sea, about 1250, the master activated the autopilot and the fishing vessel 

proceeded on a southeasterly course (166°) at 11 knots. The route of the Ehime Maru

took it into an area designated by COMSUBPAC3

 officials for the conduct of a 

distinguished visitor cruise,4

 a Navy program that promotes the mission of the service by 

permitting civilians to observe operations on board its vessels. Various senior Navy 

officials described the operating location as ìnot a highly trafficked areaî that was ìabout 

as safe as can possibly be.î 

The submarine selected to host the visitor cruise was the USS Greeneville (figure 

2), which was one of five Los Angeles-class fast-attack submarines assigned to 

Submarine Squadron 1 of the U.S. Pacific Fleet,5 but which had not been in the Pacific 

Fleetís regular rotational deployment cycle since 1998.6 

 

2

 Both radar sets were model BR-3440MA-X59, which has 50 kilowatts of output power and operates 

on a 9375 megahertz (MHz) frequency (X-band). 

3

 The acronym COMSUBPAC stands for an individual (the Commander, U.S. Submarine Force, 

Pacific) as well as the Force command office. This report refers to the person as ìthe COMSUBPACî and 

the command office as COMSUBPAC, without the article ìthe.î A list of all acronyms used in this report 

appears in appendix B. 

4

 The operating area assigned by COMSUBPAC to the Greeneville for the distinguished visitor cruise 

was bounded by 21°10′ N, 19°40′ N, 158°00′ W, and 157°00′ W, which is about 58 miles wide by 75 miles 

long, or about 4,500 square miles. 

5

 The Greeneville had been scheduled to begin an extended test voyage on February 9. The 

submarineís commanding officer (CO) agreed to conduct the cruise; however, he requested that the start of 

the test voyage be delayed until Monday, February 12, and that the civilian group be taken on a short trip 

on Friday, February 9. COMSUBPAC officials agreed, thus permitting a cruise that was contrary to 

Secretary of the Navy Instructions (SECNAVINST) 5720.44A, which stipulated ìunderway operations will 

not be conducted solely to accommodate guests.î 

6

 The Greeneville was pulled from the regular rotation in 1998 to be fitted with the Advanced SEAL 

(sea, air, land) Delivery System, which gave the submarine the operational capability to carry Navy SEAL 

forces and their equipment to and from hostile areas. For the next 2 years, the submarine went through 

underway tests and exercises of the system. 

 3 NTSB/MAB-05/01
Sail

Rudder 

Figure 2. Photograph showing crewmembers at the top of the Greenevilleís sail and 

around a hatch on the main deck. The Greeneville was an ìarctic-capableî submarine, 

meaning its sail and rudder had been strengthened to enable it to break through ice. 

(U.S Navy photo) 

On Board the Greeneville

Voyage Activities. The Greeneville had departed Pearl Harbor earlier that 

morning, at 0757, carrying 106 crewmembers (11 officers and 95 enlisted persons), 16 

civilian visitors, and the COMSUBPAC chief of staff. At the onset of the voyage, the 

visitor group received a brief presentation, including a slide show, familiarizing them 

with the submarineís operations. The civilians were allowed to ride on the main deck and 

to visit the bridge inside the sail while the submarine transited the harbor, operating on 

the surface. They subsequently moved inside the submarine, where they were organized 

into two groups of eight for what the submarineís engineering officer described as the 

ìstandard ship tour.î The scheduled activities for the visitors also included dining with 

the shipís officers and observing maneuvers, or ìevolutions,î which the commanding 

officer (CO) characterized as designed to demonstrate the submarineís capabilities. 

At 0933, the ìdeckî and the ìconnî7 were transferred from the bridge to the 

control room (figure 3), where the vesselís navigator, a 14-year veteran of the Navy, was 

scheduled to assume the duties of officer of the deck (OOD) for the first underway watch. 

The OOD is a watch position that is second to the position of CO in the operational chain 

 

7

 To have the deck means to supervise all functions and maneuvers of the ship and all personnel on 

watch. To have the conn means to direct the shipís movement with rudder and engine orders. To ensure 

safety of operations, some types of evolutions cannot be executed without the review or approval of the CO 

or, in his stead, the shipís executive officer. 

 4 NTSB/MAB-05/01
of command, and is responsible for directing vessel movements unless the CO assumes 

the conn. 

Forward 

COís 

stateroom

Control Room 

Periscope platform

Sonar Room

Fire Control Station

Figure 3. Plan view of the Greenevilleís control room, where the underway conning 

officer directs the shipís movements with rudder and engine orders. On the starboard 

side of the control room is the fire control station, where the fire control technician of the 

watch (FTOW) determines ìsolutionsî for the range, course, and speed of ìcontacts,î or 

other vessels, detected by the sonar system, which is in a separate space forward of the 

control room. The conning officer, the FTOW, and the sonar supervisor compose the 

primary members of the submarineís contact management team. 

At 1017, the Greeneville submerged within its assigned operating area about 18 

miles southeast of Pearl Harbor. The OOD testified that as the Greeneville submerged 

and dived to a depth of 150 feet, several civilian visitors were seated at ìsignificant 

control stations.î The OOD said, ìWe didnít have any specific track to follow,î and that 

the submarine just drove north to south. He said that ì[we] didnít want to get too far 

away from Pearl [Harbor].î He further stated that the plan of the day (table 1), a schedule 

listing the events and the evolutions established for the cruise, was ìfairly tight,î without 

ìa lot of time to mess around.î 

The plan of the day called for lunch to begin at 1100 and end at 1200. The 

distinguished visitors were to eat in the officersí dining room (wardroom); however, 

because the wardroom was too small to seat the visitors as one group, they were divided 

into two groups, and two lunch periods were scheduled to allow them time to dine and be 

finished before the evolutions were scheduled to begin at 1230. The first group of civilian 

 5 NTSB/MAB-05/01
visitors, joined by the CO, went to lunch at 1045, while the second group of civilians 

visited the control room and the sonar room.

Table 1. Greenevilleís plan of the day for February 9, 2001

Time Scheduled Event

0230 Reactor startup brief

0300 Reactor startup

0400-0530 Breakfast

0430 Reveille

0500 All hands muster

0545-0645 All hands clean up ship FWD [forward]

0700 Maneuvering watch personnel man the bridge

0715 Station the maneuvering watch

0800 Underway for VIP [distinguished visitor] cruise

1000 Dive 

1030 Deep dive

1100-1200 Lunch 

1130 Relieve the watch [second underway watch relieves first underway 

watch] 

1230 Angles [depth-change maneuvers involving steep angles, frequently 

at high speeds; called ìangles and danglesî by crew] 

1300 EMBT [emergency main ballast tank] blow 

1330 Station the maneuvering watch

1400 P/H [ocean point south of the channel entrance to Pearl Harbor]

1500 Moor/return to port

NOTE: Table does not show comments section of the plan, which includes names of crewmen serving in 

a training capacity during cruise. ìWatchî refers to a time period in which a crewmember is assigned to a 

given duty. 

While the civilians were in the sonar room, the crewmembers put the sonar 

system recorder in the play mode so that the guests could listen to tapes of marine life 

sounds typically heard underwater.8

 Shortly thereafter, in the control room, the OOD 

ordered the crew to ìrig for deep submergence,î and, at 1054, the Greeneville submerged 

to a depth of 700 feet. 

After reporting to the CO that conditions were ìnormal,î the OOD ordered the 

submarine to a classified depth for about a half hour while some visitors were still in the 

control room. During this time, the crewmembers collected and bottled water samples 

from the ocean, which were labeled with the classified depth and given to the visitors as 

souvenirs. At 1134, the OOD brought the vessel up to a depth of 650 feet. 

 

8

 The sonar supervisor said that the crew forgot to reset the recorder before the evolutions began; 

therefore, the audio received by the sonar system was not captured on tape. 

 6 NTSB/MAB-05/01
Watch Change. The plan of the day indicated that the second underway watch 

relieved the first underway watch at 1130. Shortly after 1130, the main propulsion 

assistant entered the control room to prepare for his duty assignment as the OOD of the 

second underway watch. The main propulsion assistant had about 6 years of service in 

the Navy, and the Greeneville was his first sea tour. He had reported to the vessel in 

March 1999 and begun a qualification program for various onboard duty assignments. He 

had qualified as an underway OOD about 6 months before this distinguished visitor 

cruise; however, during this time, the Greeneville was in the shipyard for 4 months, from 

September through December 2000. (This officer is referred to as the OOD-2 in this 

report.) 

The OOD-2 said that he learned the Analog-Video Signal Display Unit (figure 4), 

or AVSDU, was not working when he reported to the control room for his watch. The 

AVSDU duplicated the contact data displayed on the monitors in the sonar room and 

permitted the conning officer to observe the vessels being tracked without leaving the 

control room. The navigator had noted that the AVSDU was inoperable and had reported 

its status to the CO before the Greeneville had sailed that morning; however, the 

malfunction of the sonar repeater did not meet the criteria for a significant equipment 

casualty that would have precluded the submarine from sailing.9 

Figure 4. The Analog-Video Signal Display Unit, or AVSDU, was a sonar repeater 

installed near the Greenevilleís periscope platform. On the day of the accident, the 

AVSDU was not working. (U.S. Navy photo)

AVSDU

The OOD-2 stated that, as part of his status briefing, the OOD of the first 

underway reminded him that to compensate for the loss of the AVSDU, he needed to 

ìperiodically go into sonar to assay the contact picture.î 

 

9

 See Operational Reports, Naval Warfare Publication 10-1-10 (Chief of Naval Operations, 

Washington, DC: 1987). 

 7 NTSB/MAB-05/01
The first underway OOD said that he observed his watch relief as he did ìa 

normal prewatch tour.î The OOD-2 went into sonar and talked to the sonar supervisor to 

get an idea of what the contacts were. The OOD-2 next reviewed the monitors at the fire 

control system station ìfor a little whileî and then went over to the chart table to verify 

the submarineís position and to check the plot to ensure ìwe were where we should be.î 

The OOD-2 recalled that when he took over the conn, at 1143, the Greeneville

was ìdriving southî at a speed of 10 knots and a depth of 650 feet. He contacted the CO 

to obtain permission to allow crewmembers in the torpedo room to fire slugs of water 

from the torpedo tubes while the visitors in the area watched. To give the civilians a 

sense of how the ship drove, he permitted some of them to sit at the controls under the 

oversight of qualified technicians while he ordered simple course and depth changes. 

About the same time, the first lunch sitting was ending. The CO testified that the 

lunch period was his first opportunity to talk with the guests. The CO had almost 20 years 

of service with the Navy and had been assigned the command of the Greeneville in 

March 1999. He said that the visitors were from his home state and as a result of his 

conversations with them, the first lunch sitting ìran a little long.î At 1145, the second 

group of visitors went to lunch, which was hosted by the submarineís second in 

command, the executive officer (XO), a 15-year Navy veteran who had served on the 

Greeneville as XO since 2000. 

About 1207, the OODñ2 ordered a course change to north to begin the return to 

the northern part of the Greenevilleís assigned operating area. Shortly before 1230, as the 

Greeneville was proceeding on a due-north course of 000°,10 the sonar system (figure 5) 

began tracking a contact, bearing 331.2°, which the crew designated S-12.11 Three 

crewmen were on duty in the sonar room: the sonar supervisor, a sonar technician at the 

broadband12 ìstack,î or workstation, and a workload share stack operator. 

The sonar supervisor had 7 years of Navy service, including 4 years as a qualified 

sonar supervisor (3 years on the Greeneville and 1 year on his previous submarine). He 

had been assigned to the Greeneville in 1997. The broadband stack operator, who had 

primary responsibility for detecting and tracking sonar contacts, had been in the Navy for 

1 1/2 years and had been qualified to stand sonar watch for over a year. The workload 

share operator, who was responsible for maintaining the sonar log and providing backup 

to the broadband operator, had been in the Navy about a year and on board the 

Greeneville for 6 months. He had not yet qualified to stand watch in sonar; therefore, he 

was considered an ìunder-instructionî operator. 

 

10 All bearings are based on true north. 

11 When sonar gains a vessel contact, it is assigned a letter and number designation, such as S-1. The 

letter ìSî stands for sonar and is pronounced using the military phonetic alphabet for S, which is Sierra. 

The number represents the order in which the vessel is detected. 

12 Broadband refers to a wide range of sound frequencies. The broadband monitor is a visual display of 

all sound waves around a submarine. 

 8 NTSB/MAB-05/01
Figure 5. Each sonar workstation, or stack, had two monitors. The two stacks at right 

displayed system input from hull-mounted arrays. (U.S. Navy photo)

About 1232, sonar gained a new contact (the Ehime Maru), bearing 358°, or 

almost due north. The crew designated the contact S-13. The sonar supervisor assessed it 

to be a ìdistantî contact.13 Reconstructed data show that, at this time, the Ehime Maru

was about 20 nautical miles away. 

According to the sonar supervisor, the acoustic environment was good, and 

contacts could be heard from a distance of 15 to 20 nautical miles. He said that, as sonar

supervisor, he looked for ìsomething with a very high bearing rate, something that may 

be on our left side drawing right, or right side drawing left,î which could represent a 

ìclosingî situation (meaning the target is heading toward the submarine). He said that 

when sonar first gained S-12 and S-13 (the Ehime Maru), ìthey did not have much of a 

bearing rate.î 

The sonar system was integrated into the fire control system and relayed bearing 

data on the contacts held, which was then displayed in four different formats on the fire 

control monitors. (See figure 6.) The FTOW, the technician manning the watch station, 

was a 14-year Navy veteran who had been involved in operating fire control equipment 

12 of his 14 years in submarines. His work involved performing ìtarget motion 

analysisî14 (TMA) of the contacts being tracked by sonar, meaning he was responsible 

for determining the course, speed, and range of surface and submerged vessels (or 

 

13 At the Navy court of inquiry, senior officials testified that for a contact to be considered distant, it is 

20,000 yards or more away. 

14 The Navy also refers to target motion analysis as contact motion analysis in some documents. 

 9 NTSB/MAB-05/01
targets) potentially posing a threat to the submarine. He accomplished TMA by adjusting 

the knobs at his station monitors to enter estimates for course, speed, and range variables 

into the fire control system computer and iteratively resolve the motion of the sonar 

contact relative to the position of the ìown shipî (the submarine). 

(1) Line-of-sight: shows bearing as a 

vertical line, contact as a vector at the top 

of the screen, and own ship as a vector at 

the bottom of the screen. 

(2) Time-bearing: plots contact bearing 

against time. 

(3) TMA: compares incoming sonar 

bearings, shown as dots, with the bearing 

generated by the fire control computer for 

the parameters of course, speed, and 

range in the computer. Incoming dots 

appear above the previous dots to form a 

line of dots. To achieve a tracking 

solution, the FTOW varies course, speed, 

and range settings to eliminate the 

difference between the generated 

bearings and the actual bearings coming 

from sonar. 

(4) Op-summary: shows position of all 

contacts and land with respect to position 

of own ship.

Figure 6. The four display screens at the fire control station, looking left to right, are (1) 

line-of-sight, (2) time-bearing, (3) TMA, and (4) op-summary. (U.S. Navy photo) 

The FTOW said that he followed his usual procedure to determine a solution for 

S-13 and other contacts, based on the information relayed to him when the sonar system 

initially gained a contact. He indicated that sonar did not designate any of the contacts as 

merchant ships. He stated that ìjust being in Hawaiian waters,î he assumed that the 

contacts were typical of the ìtraffic around here . . . probably trawlers, fishing vessels 

[and] pleasure crafts.î 

The FTOW told Safety Board investigators, ìI always put in a closing solution, 

which means the contact . . . is pointing at us, coming at us . . . and anywhere between 5 

and 15 knotsî depending on whether the contact is a trawler or a merchant ship. He added 

that he always initially entered a conservative range, ìusually anywhere between 8,000 

and 10,000 yards.î 

He said that if the contact had a low or steady bearing rate, ìyou assume that heís 

closing.î He also stated that the fire control system needed several bearing rate changes 

to refine a solution, which he obtained when the submarine changed course, as it did 

 10 NTSB/MAB-05/01
about 1240, when the OOD-2 ordered a baffle clear.15 The Greeneville then resumed a 

northerly course, which it maintained until about 1310. 

Fire control data, as reconstructed by the Navy, show that after the bearing data 

for S-13 were relayed from the sonar system to the fire control system (at 1232:59), the 

FTOW entered three closing solutions between 1233:14 and 1240.00. While the FTOW 

was calculating these early solutions for S-13, the Ehime Maru was moving at 6 knots 

while stowing anchor. The FTOW next entered a closing solution about 16 minutes later, 

at 1256:00. Then, about 1258, he changed the course for S-13 from closing to ìopening,î 

that is, heading away from the submarine. 

The FTOW stated that, on the day of the accident, he never tracked more than two 

or three contacts, which was a light workload. He indicated that, in the past, he had 

tracked as many as 20 to 30 contacts in high-traffic areas and that on more than one 

occasion, he had worked with another fire control technician at his station to track more 

than 40 contacts at a time. 

After the second visitor lunch ended, about 1245, the XO went to the COís 

stateroom to report that the mess (kitchen and dining areas) would be secured within 5 

minutes and to suggest that the ship then begin the angles evolutions, which had been 

scheduled on the plan of the day for 1230. The CO asked who had the helm and, upon 

learning that a less experienced helmsman was on duty, directed the XO to replace him 

with a more experienced helmsman for the high-speed evolutions. The CO then stayed in 

his stateroom, signing photographs to give as mementos to the civilian guests, while the 

XO left to join the other crewmembers in the control room. 

The OOD-2 told investigators that, shortly before 1300, he realized that, given the 

position of the submarine, about 17 miles from the unmarked seaward entrance to Pearl 

Harbor (designated P/H16), and the activities listed on the plan of the day, the submarine 

would be late returning to P/H. The OOD-2 expressed his concerns about returning on 

time to the vessel navigator, who had returned to the control room after lunch because he 

wanted to oversee the navigation watchstanders while the submarine performed some of 

the high-speed evolutions. The navigator later told investigators that he determined the 

submarine was about 10 or 12 miles from P/H. The navigator said if the submarine had 

surfaced at that time and driven toward P/H, the Greeneville would have arrived there on 

time. He knew, however, that the CO wanted to do evolutions so he approached the XO 

and reminded him of the time and the need to get back to P/H by 1400. 

The XO then returned to the COís stateroom to advise him that they had less than 

an hour before the vessel was due back at P/H. The XO testified that the CO said he 

 

15 As is typical of all submarines, interference from noises generated by the Greeneville itself 

prevented the sonar system from reliably detecting sonar signals between approximately 120° and 240° 

relative to the vesselís bow. This arc astern of the vessel is known as the ìbafflesî area, and a submarine 

has to periodically alter course to uncover this null area, or ìclear the baffles,î for the sonar system. 

16 P/H is located at 21°16′17′′ N, 157°56′33′′ W, about 6 miles from the northern edge of the 

Greenevilleís assigned operating area on the day of the accident. 

 11 NTSB/MAB-05/01
would finish signing the photographs for the visitors and remarked, ìWell, I guess we are 

going to be late.î Soon after, the navigator went to the COís stateroom to remind him that 

the submarine was due back at 1400. 

The navigator said that as the CO left his stateroom, he said that he was going ìto 

push the OOD[-2].î The quartermaster17 indicated that he was present when the navigator 

questioned whether the Greeneville would be able to complete all the planned evolutions 

and make it back to P/H on time. He stated, ìWe talked it over with the XO and CO and 

they thought we could.î 

The OOD-2 told Safety Board investigators that no senior officer, including the 

navigator, the XO, or the CO, discussed with him whether or how the plan of events 

might be changed or evolutions curtailed to avoid being late. He testified that he assumed 

that some evolutions would be canceled. The OOD-2 stated that the submarine was about 

5 miles from the edge of its assigned submerged operating area, and that he was 

concerned about doing high-speed maneuvers near the edge of the operating area. He 

further stated that he could not remember whether he voiced his concerns to the officers. 

All Visitors Called to Control Room. The XO made an announcement on the 

public address system inviting all guests to the control room to observe the conduct of the 

evolutions. The OOD-2 said that before the visitor group gathered in the control room, 

sonar had been tracking three surface vessels: S-10 to the south and S-12 and S-13 (the 

Ehime Maru) to the north. The OOD-2 said, ìWe did not have a great contact picture of 

where they [the contacts] were.î At 1245:45, S-10 had ìfaded,î meaning it no longer was 

being tracked by sonar. The OOD-2 did not order course changes for TMA to improve 

contact awareness for S-12 and S-13 before the XO invited the guests to the control 

room. 

The COMSUBPAC chief of staff and 15 of the 16 civilian visitors18 entered the 

control room about 1310, or about 10 minutes after the scheduled time for the last 

evolution on the plan of the day. Several visitors then went into the sonar room (figure 7). 

Meanwhile, the CO testified that, after exiting his stateroom, he went into sonar to 

assay the contact picture. He said that he reviewed the sonar display of the contacts with 

the sonar supervisor, who advised him of two contacts, a merchant vessel to the 

northwest (S-12) and a surface craft to the north (S-13, the Ehime Maru). According to 

the CO, the sonar supervisor told him that the contacts ìwere distant, [and] up by land.î 

The sonar supervisor told investigators that he assumed the contacts were more than 

10,000 yards away. He said that he based his assumption on three factorsóthe bearing 

rate of the contacts was still small, the signal-to-noise ratio (SNR) was relatively low 

(SNR is a measure of signal strength relative to background noise), and the other sound 

characteristics indicated that the contacts were probably more distant than close. 

 

17 The quartermaster on watch plots the vesselís position on a navigation chart and makes course 

recommendations to the conning officer. He also maintains the deck log. 

18 One of the civilians became seasick and was resting in a stateroom. 

 12 NTSB/MAB-05/01
Figure 7. When the Greeneville crew began high-speed maneuvers to demonstrate the 

capability of the submarine to the visitors, 33 people, including crew and civilians, were 

in the control room and the sonar room. This illustration shows the approximate location 

of the civilians when the submarine executed the last evolution, an emergency surfacing 

maneuver. 

About 1314, the CO entered the control room and advised the OOD-2 to prepare 

the submarine to perform the angles and dangles maneuvers. He did not discuss the 

contacts with the OOD-2 when he returned to the control room. He said that, based on his 

prior experience overseeing the main propulsion assistant while he operated as an OOD, 

he was confident that the officer had maintained situational awareness, that is, knew 

where the submarine was in respect to the contacts. At the Navyís court of inquiry, senior 

officers and enlisted personnel stated that, as an OOD, the main propulsion assistant had 

a reputation for being methodical, meticulous, and ìnot easily pushed.î They also 

indicated that he typically took longer than more experienced OODs to accomplish tasks. 

The CO said that the OOD-2 acknowledged his instructions. He further stated, 

 13 NTSB/MAB-05/01
I didnít focus on [the OOD-2ís] actions. I canít tell you if he did not exit the conn 

and enter the sonar room, which would have been customary for him to do prior 

to the conduct of those evolutions. I . . . was looking elsewhere, I was walking 

around the control room to enhance my situational awareness, my understanding 

of the contact pictures, looking over . . . to see what we had on time/bearing 

displays, to see what the Fire Control Technician of the Watch . . . was doing, 

and looking and engaging the Quartermaster as to our current shipís position to 

help me understand what our situational awareness was because I had lost it 

while [I was] in the dining room and . . . stateroom. 

The CO testified that he looked at the ops-summary display at the fire control 

station, which shows the position of all contacts with respect to the position of the 

submarine. However, he said he did not notice which time history the FTOW had 

selected for the display, and if a short time history had been selected, the display would 

not have shown that the OOD-2 had ordered only two course changes (the baffle clear at 

1240 and the course change to north at 1245). The CO also stated that he did not look at 

the plot maintained by the navigation watchstanders. He said if he had done so, he would 

have realized that the OOD-2 had driven the boat only in a northerly direction and had 

not driven in easterly or westerly directions that might have provided an accurate contact 

picture. 

Witnesses stated that the CO chatted with the civilians, advising them of the best 

locations in the control room to observe the maneuvers. Three of the civilians stood on 

the periscope platform. The FTOW stated that about six or eight visitors stood around the 

fire control station, blocking his access to the contact evaluation plot (CEP), a large paper 

graph that was mounted on the bulkhead forward of the periscope stand. The FTOW was 

required to annotate the CEP with the submarineís heading, the sonar contactsí bearings, 

and other pertinent observations to provide the OOD with a display of the submarineís 

position in relation to the known vessel contacts.19 

Some of the civilians stood in front of the forwardmost two fire control system 

displays, which the OOD-2 said he typically used to monitor the contact situation. The 

OOD-2 later told Safety Board investigators, ìI didnít have free access all the way over 

there. I got close enough where I could look at the contact picture and . . . the fire control 

screens.î (See figure 6.) The CO said that when he went to the control room and 

reviewed the fire control system consoles, the visitors blocked his view of the CEP. 

Several crewmembers stated that equipment preparations needed to support 

higher speed maneuvers delayed the start of the evolutions. According to the OOD-2, the 

CO ìseemed frustrated that he couldnít start the maneuvers right away.î 

 

19 The Greeneville was among the last Navy submarines to be equipped with an automated CEP and 

did not have one at the time of the accident. All Navy submarines now have automated CEPs that display 

data for both the submarine and its contacts. Navy officials who examined the Greeneville CEP after the 

accident described the entries made by the FTOW as ìvery sparse,î stating, ìThere were essentially no 

contact entries for the hour leading into the collision.î 

 14 NTSB/MAB-05/01
ìAngles and Danglesî Begin. At 1315, the CO ordered the Greenevilleís speed 

increased to 14 knots. The OOD-2 stated that for the angles maneuversósteep angled 

depth changes, frequently at high speedsóa CO typically gives an OOD the boundaries 

of where to operate, such as ìstay between these two depthsî and ìchange course using 

this high an angle,î and then allows the OOD to choose the course of action. Both the 

OOD-2 and the CO stated that, in this instance, the CO stood immediately behind the 

OOD-2 and ordered the specific course, speeds, and depths that he desired, and the OOD2 merely repeated the orders to the diving officer and the helmsman. 

The OOD-2 said that the CO directed him to order angles up to 30° and depth 

changes from 650 feet to 150 feet at speeds varying between 10 and 15 knots. The FTOW 

testified that the ìcaptain was driving the whole evolution,î and the ìOOD[-2] was a 

mouthpiece.î While the ship was going through the evolutions, the CO gave the civilian 

visitors a running commentary on the maneuvers. 

According to the FTOWís testimony, during the angles and dangles, he was able 

to track contacts S-12 and S-13 (the Ehime Maru) but not ì100 percent . . . the whole 

time.î According to system data, the solution variables for S-13 were not changed for 23 

minutes, between 1314 and 1337, while the submarine executed first the angle evolutions 

and then the high-speed turns. 

The FTOW said that because the civilian visitors blocked his access to the CEP 

and because ìyou really couldnít do anythingî during the high-speed maneuvers, he 

stopped maintaining the CEP. He told Safety Board investigators that he did not advise 

anyone that he had stopped annotating the CEP and, because no one mentioned the plot, 

he thought that no one noticed that he was not maintaining it.20 He later told Safety Board 

investigators that he had been the FTOW on numerous visitor cruises on the Greeneville

and other submarines in the past and had never maintained the CEP while civilians were 

in the control room. 

About the time of the angles and dangles, a sonar technician who had served on 

the first watch returned to the sonar room to get his jacket. He testified that several 

civilian guests were in the sonar room, in addition to the sonar supervisor, the broadband 

stack operator, and the workload share stack operator. The off-duty sonar technician was 

a 12-year Navy veteran who had joined the Greeneville crew in 2001. He said that he 

noticed that the sonar supervisor and the sonar technicians were trying to talk to each 

other and the guests at the same time. 

The sonar supervisor asked that the off-watch sonar technician stand by the underinstruction operator on the workload share stack because having ìanother set of eyes . . . 

canít hurt.î The sonar supervisor later testified that he asked the off-watch sonar 

technician to stay because the under-instruction operator had not completed the sonar 

qualification requirements, not because the sonar operator at the broadband monitor was 

 

20 A submarine force operations order (OPORD) stipulates that the FTOW cannot cease maintaining 

the CEP without permission from the conn. 

 15 NTSB/MAB-05/01
overloaded. He did not brief the off-watch sonar technician about the contacts that sonar 

held at that time. 

The off-watch sonar technician said that the sonar operator at the broadband stack 

appeared not to be distracted by questions from the guests. The unqualified workload 

share stack operator, however, was trying to answer the visitorsí questions. At one point, 

the workload share stack operator started to turn away from the display to talk with the 

guests, but the off-watch technician told him not to do so. The technician said that he then 

asked the visitors to leave the sonar room. 

The off-watch sonar technician said that during the angles and dangles, he became 

concerned about an ìinterference patternî on the sonar monitor that appeared to suggest 

that one of the contacts was closing. He expressed his concern to the sonar supervisor, 

who told him to check to see what data the FTOW had on the contact. Shortly thereafter, 

the off-watch sonar technician went into the control room and asked the FTOW about 

ìS-10,î stating that it appeared to be a close contact. The FTOW said that he made some 

adjustments on the fire control system to try to put the contact on a closing course, but ìit 

wouldnít fit,î and he advised the off-watch sonar technician that the contact was on an 

opening course.21

Begin High-Speed Turns. About 1325, the CO directed the OOD-2 to order a 

course change to 140°, and the Greeneville began executing high-speed turns. According 

to the sonar supervisor, moving back and forth numerous times ìjust makes your display 

[look like] spaghetti. Youíve got lines in all directions from how the shipís driving. 

Contacts are kind of fading in and outî as they enter and leave the baffle area. Both S-12 

and S-13 faded as they entered the port baffles. 

To obtain accurate TMA results, the conning officer is responsible for ordering 

the submarine on a constant course, speed, and depth for a period of observation known 

as a ìleg,î during which the relative motion of the contacts can be observed. According 

to Navy officials, a minimum of two legs is necessary to determine the solution for a 

contact, and maneuvers that afford looking at the target from different aspects ìvery 

quicklyî reduce the possible solutions to ìa very limited number.î 

Shortly before 1331, after the high-speed maneuvers were completed, the CO 

ordered a speed reduction, a decrease in depth, and a course change to 340°. The COís 

Standing Order 6 stipulated that the submarine would be held on course a minimum of 3 

minutes to allow sonar and fire control to obtain an accurate contact picture.22 According 

to recorded data, the submarine remained on the 340° course for 91 seconds. Of this time, 

 

21 System data show that the Greeneville lost the track on S-10 more than 30 minutes earlier, about 

1245. The Navy court of inquiry concluded that the off-watch sonar technician confused his contact 

numbers and that based on his observation that the close contact later faded in the baffles during the course 

turn to 120°, was referring to S-12. 

22 Submarine COs develop standing orders for vessel operating requirements that are based on 

instructions issued by the Navyís submarine forces commanders. The fleet instructions state that 

commanding officers ìretain the flexibility to adapt/edit their standing orders as long as they meet the core 

requirements.î The 3-minute course standard for TMA is set out in Naval Warfare Publication 3-21.51.1. 

 16 NTSB/MAB-05/01
the total period that the Greeneville maintained a steady depth and speed was about 20 

seconds. 

Order to Periscope Depth. At 1331, the CO ordered the ship to slow to 10 knots 

and directed the OOD-2 to make preparations to proceed to periscope depth and to be at 

that depth within 5 minutes.23 Figure 8 shows key events, beginning at 1331, on the 

Greeneville relative to the tracks of the submarine and the Ehime Maru. 

Figure 8. Plot showing the tracks of the Greeneville and the Ehime Maru. The 

Greeneville track is annotated with key events on the submarine beginning at 1331. 

The Ehime Maru track is annotated with the position of the fishing vessel at some 

corresponding times. 

The COís Standing Order 6 lists 16 actions and instrument checks, some 

involving as many as six steps, that the OOD is required to perform when preparing to go 

to periscope depth. One required action is for the OOD to conduct a periscope-depth 

briefing with key personnel to verify the contact picture. The CO later told Safety Board 

investigators, 

 

23 The COís own standing orders stipulated that no less than 8 minutes would be allotted for the 

preparations necessary to go to periscope depth. 

 17 NTSB/MAB-05/01
He [the OOD-2] was so . . . slow, I knew that he couldnít get to PD [periscope depth] in 

5 minutes. It was my objective to give him a goal to work towards . . . I doubt that any 

of my experienced officers of the deck could have gotten to periscope depth in 5 

minutes. 

The OOD-2 stated that when he heard the CO order him to prepare to go to 

periscope depth in 5 minutes, he considered the directive ìunusualî and was concerned 

about the time limit. He said that when preparing to go to periscope depth, the OOD 

drives the ship ìa certain way . . . so he can get a clear contact picture.î To ensure the 

accuracy of the information, he asks sonar to report all contacts. If the reliability of the 

data is questionable, the sonar supervisor can advise a good course for TMA, whereupon 

the OOD orders more maneuvers. 

The OOD-2 said that he then reports to the CO explaining the contact picture, 

including the types of contacts and their bearings, speed, and drift. The CO evaluates the 

OODís report and, if convinced that the information is accurate, grants the OOD 

permission to proceed to periscope depth. 

The OOD-2 said that he did not have a periscope-depth briefing because of ìthe 

time constraints and the challenge to go to periscope depth rapidly.î He further stated, 

I would never think of not doing a periscope brief but, at the time, I had the 

commanding officer present, the executive officer present, other department 

heads present, as well as the chief of staff, SUBPAC. 

Regarding the actions of the CO, the OOD-2 stated, 

Hereís a man with much more experience than I have, much more schooling than 

I have, [who] can much more rapidly assess and evaluate information . . . I did 

not believe that he was putting the ship in an unsafe position, and [thought that] 

. . . the contact picture allowed for safe periscope depth. 

Regarding his orders to quickly complete the steps necessary to bring the vessel to 

periscope depth in less time than indicated in his standing orders, the CO later testified, ìI 

chose to not follow specific things out of my standing orders because I deemed at that 

time them not to be necessary.î 

Signal-to-Noise Ratio Increase. Meanwhile, in the sonar room, the broadband 

stack operator noted that while the submarine was in the middle of the high-speed 

maneuvers, the SNR for S-13 was ìrelatively high.î Figure 9 shows the SNR data for 

S-13 (the Ehime Maru) that were captured by the Greenevilleís sonar system computers 

on the day of the collision, as plotted by Safety Board engineers. 

At this time, the off-watch sonar technician who had been assisting the 

technicians at the stacks was in the control room, talking with the FTOW. The broadband 

operator said that he reported the SNR increase on S-13 to the sonar supervisor, 

 18 NTSB/MAB-05/01
whereupon the sonar supervisor ìwent to the curtain in control.î24 The sonar technician 

said that he did not know whether the sonar supervisor spoke to anyone about the SNR 

increase. When asked about the broadband operatorís report, the sonar supervisor said 

that he did not recall being told about the SNR increase. 

Figure 9. An increase in the SNR for a contact can be an indication that the target is 

getting closer. In this plot, each circle represents an S-13 signal captured by the 

Greenevilleís sonar system. As indicated in the plot, the SNR for the Ehime Maru

increased over time except for when the fishing vessel was briefly in the baffle area. 

Note: The plot developed by Safety Board engineers is not representative of the display 

on the sonar monitors. 

After giving the OOD-2 the order to go to periscope depth, the CO briefly went 

into his stateroom. From there, he went to the sonar room to assay the sonar picture and 

ìobtain contact awareness.î The CO said that as the ship was coming to a keel depth of 

150 feet, he overheard the broadband operator tell the sonar supervisor that they had 

regained ìpreviously held contacts.î Recorder data indicate that while the CO was in 

sonar, the operators regained two contacts, S-12 at 1332:03 and S-13 (the Ehime Maru) at 

1332:48. According to the sonar supervisor, he did not recall discussing any contacts with 

the CO while he was in the sonar room. 

In the meantime, the XO told the OOD-2 that he would help him determine a 

course for proceeding to periscope depth by going into the sonar room to get the contacts. 

 

24 The aft door of the sonar room had a curtain to block the light from the control room. 

 19 NTSB/MAB-05/01
The XO later stated that he did so because the AVSDU was not operating. The XO went 

forward in the corridor and entered the sonar room through its forward door. 

As the XO entered the sonar area, the CO was exiting the aft sonar door to go into 

the control room. About that time, the off-duty sonar technician reentered the sonar room 

after his conversation with the FTOW. He discussed his concerns with the XO, stating 

that he did not think he was wrong about the closing contact. The XO checked the fire 

control screens in the control room, returned to sonar, and asked the off-duty sonar 

technician how fast the Greeneville was operating. The off-duty sonar technician said that 

he then realized the submarine itself had caused the interference pattern because of the 

speed it was traveling. He further stated that his suspicions were confirmed when the 

submarine slowed and the interference pattern went away. 

When the CO reentered the control room, he looked at the first monitor, the lineof-sight display, at the fire control station. The CO later told the Safety Board that, at this 

time (1333), he did not think the contact picture had changed, meaning sonar was holding 

two contacts. He stated, ìI was confident that those contacts remained close along the 

Oahu coast, operating in that vicinity.î He said, ìI didnít pick up on the fact . . . that we 

had driven on north-south legs,î meaning the Greeneville had not executed turns that 

would have provided changes in bearing rates. 

Upon returning to the conn, the CO ordered a course change to 120° for the 

Greeneville to clear baffles. Concurrently, he announced to the visitors that the purpose 

of a baffle clear was to allow sonar to check for hidden contacts and prevent a collision at 

periscope depth. The OOD-2 stated, 

I was a little surprised when . . . the captain directed me to change course. I felt 

that he . . . was kind of driving the ship at that point . . . He had been kind of 

driving the ship before then, during the angles and dangles, when he gave me the 

courses and depths and speeds he wanted to drive. 

During the course change, sonar gained a new contact, S-14. The fire control 

system displayed the automatic first solution for S-14 at 1334:03. The FTOW 

subsequently determined only one tracking solution for S-14, which he entered into the 

fire control system at 1334:48. 

When the XO entered the sonar room, he positioned himself behind the sonar 

technicians, looking at the sonar display monitors. The sonar supervisor said that he 

assumed that the XO had come into sonar because the AVSDU was not working. He 

further stated that he did not discuss the contact picture with the XO. The XO later told 

Safety Board investigators that, while in sonar, he observed three contacts. He then stood 

in the sonar roomís aft doorway while the submarine went to periscope depth. He did not 

give the OOD-2 or the CO any information about the sonar contacts or recommend any 

course for surfacing. 

Shortly after sonar gained contact S-14, the signal for contact S-12 faded in the 

port baffles. About 1335, the baffle clear was completed, and the submarine was steady 

 20 NTSB/MAB-05/01
on course 120°. Reconstructed system data show that, about this time, the Ehime Maru

(contact S-13), operating at a constant heading of 166° and a speed of 11 knots, was 

3,282 yards from the submarine. When the submarine steadied course, the FTOW was 

able to resume determining solutions for the contacts. The FTOW said that he had ìvery 

lowî confidence in his track for S-14 because it was based on ìa single legî that had 

lasted about a minute. 

At 1335:39, the OOD-2 announced on the public address system for the crew to 

report all contacts. The CO testified that he recalled the sonar supervisor reporting two 

contacts, S-13 and S-14. The FTOW stated that he recalled sonar reporting three contacts: 

S-12, S-13, and S-14. About that time, the CO announced that he had ìa good feel for the 

[sonar] contacts.î According to the FTOW, the fact that the sonar announcement included 

S-14 and the COís statement reassured him that the CO was aware of S-14. 

About 1337, about 1 1/2 minutes after the Greeneville was on a steady 120° leg, 

the CO ordered the OOD-2 to proceed to a depth of 60 feet (periscope depth). 

Reconstructed system data show that, at 1337:00, the Ehime Maru was at a range of 

2,724 yards, or 1.34 nautical miles. (See figure 8.) The FTOW stated that he quickly 

updated the solutions for the contacts that he was tracking, including S-12, S-13, and 

S-14. He described his updating as ìrushedî and said that he was still updating his 

contacts as the submarine ascended to periscope depth. He said that he continued to give 

priority to analyzing S-14 because of the lack of data on the contact. 

The sonar supervisor stated that when the submarine ascended to periscope depth, 

the monitor displays were changed to a different scale to enable the crew to watch for 

transient noise that was ìdifferentî or ìunexpected,î such as a quick change in a contactís 

bearing rate. The FTOW stated that while the submarine proceeded to periscope depth, he 

monitored the three contacts on the fire control systemís time-bearing presentation 

because a fast bearing rate would indicate a close contact. System data indicate that, at 

1337:48, less than a minute before the submarine arrived at periscope depth, the FTOW 

updated the solution for S-13 (the Ehime Maru), changing it from an opening to a closing 

solution and adjusting the range from 16,000 to 4,000 yards. The dots on the display 

immediately began to align, an indication that the solution was comparatively accurate. 

Reconstructed system data show that, at 1337:48, the Ehime Maru was at a range of 

2,510 yards, or 1.24 nautical miles. (See figure 8.) The FTOW said that he failed to 

notice the range of S-13 ìbecause he was trying to get everything doneî before the 

submarine reached periscope depth. Standing Order 6 stipulated that the FTOW would 

notify the conn of all contacts 4,000 yards or less from the Greeneville; however, in this 

case, the FTOW did not report the status of S-13 to either the OOD-2 or the CO. 

As the Greeneville ascended to periscope depth, the CO asked that some of the 

civilian visitors move because they were blocking the view of a video monitor that 

displayed the image seen through the periscope.25 At 1338:30, the ship arrived at a depth 

 

25 The periscope video system, or PERIVIS, displayed the periscope image on several monitors 

throughout the vessel, including a screen near the fire control station. The PERIVIS also had a record 

feature that could be activated by the person using the periscope. 

 21 NTSB/MAB-05/01
of 60 feet. Reconstructed system data show that, at this time, the Ehime Maru was at a 

range of 2,315 yards, or 1.14 nautical miles. (See figure 8.) 

Periscope Search. The OOD-2 said that when the submarine reached periscope 

depth, he started to conduct a normal search using the No. 2 periscope.26 When the 

periscope broke the waterís surface, he executed the rapid low-power searches. He said 

that he completed his three rapid revolutions and announced, ìNo close contacts.î He 

said that he was about to begin his next search when the CO took the periscope and began 

his own search routine. The FTOW said that, in accordance with the usual procedures, no 

one said anything in the control room or made any reports until they heard the OOD-2 

say, ìNo close contacts,î after the initial phase of his periscope search. 

The CO later testified that he searched primarily in the sector where he believed 

the known contacts were located. He stated that he 

swept the scope in low power, went to high power, looked, then panned to the 

right, saw the island [Oahu] . . . I can only see the mountain peak, I canít see the 

mountains . . . because of this white haze . . . Then I could see an airplane taking 

off. . . . I panned to the right where I thought I would see [S-13] the Ehime Maru. 

I looked over at the remote repeater [own-shipís data] and I saw the numbers and 

[thought] that looks right. Thatís where the guy is. Didnít see him. Then went to 

low power and then turned to the right. I think . . . the Ehime Maru was perhaps 

further to the right, and as I swept in low power . . . missed her. And thatís the 

only explanation that I can think of as to why I missed the vessel. It was perhaps 

too far to the right out of my field of view when I was doing my high power 

search thinking that the degree of optics that I was covering would encompass 

and overlap that area of uncertainty. 

The FTOW said that when the periscope projected above the water, he shifted his 

attention to the PERIVIS monitor. He said that the CO did a ìquick 360-degree lookî in 

the general direction of the contacts, 40° and 340°, and then stopped on 18°. The CO next 

ordered the ship ìto come up for a high look,î a depth of 58 feet, to increase the 

periscope height of eye. The FTOW described the COís search as ìuncuedî because he 

did not ask fire control to verify the bearings to the contacts, ìwhich is my job.î The 

FTOW stated, however, that he ìwas confident that the captain knew what he was doing 

during the periscope search.î 

The FTOW said that he thought that he had a good range for S-13, and that it was 

between 5,000 to 6,000 yards while the submarine was at periscope depth. He was under 

the impression that, of the three contacts, S-14 was the closest. He said, however, that he 

 

26 Naval Warfare Publication 3-13.10 requires making at least three 360° low-power sweeps, about 8 

seconds per sweep, to search for close contacts as soon as the periscope breaks the surface. If safe operation 

is indicated, ìNo close contactsî is announced. The Greenevilleís former CO, in describing a standard 

periscope search, testified that after the initial three sweeps, the OOD would do an air search in which he 

panned from the maximum elevation view down to the horizon, then would announce, ìNo airborne 

contacts.î He would then do a 360° low-power search, which took about 45 seconds, followed by a 90° 

high-power sector search on the point where he terminated the 360° low-power search. 

 22 NTSB/MAB-05/01
was not surprised when he didnít see a vessel on the PERIVIS because ìfire control [is] 

only as good as the maneuvers you make,î and he had ìrange errors . . . more than 50 

percent of the time.î He said that he estimated that he might be off by about 2,000 yards 

for S-13. He said that his confidence in the solutions for the contacts ìimmediately rose 

upî when they did not see any vessel through the periscope. 

ESM Search. In addition to the periscope search, the movement to periscope 

depth enabled the technicians at the electronic support measures (ESM) system, located 

in a separate room behind the control room, to conduct a defensive search to identify and 

classify sources of detected electromagnetic radiation. Two crewmembers, a qualified 

and an under-instruction ESM operator, were present in the ESM room when the 

submarine went to periscope depth. The ESM station had one set of headphones. When 

the ESM antenna broke the waterís surface, at 1338, the under-instruction ESM operator 

listened on the headset for aural indications of nearby vessels, and the qualified operator 

listened to the open microphone for the OOD-2ís report.27

The qualified ESM operator said that he asked the under-instruction ESM 

operator what he thought, and that he responded there were multiple contacts but none 

was close. He said that before the OOD-2 announced, ìNo close contacts,î he took the 

headset and listened to the aural indications. The categories of signal strength range from 

1 to 5, with 5 being the strongest. The qualified ESM said that he heard none with a 

signal strength of 4 or 5, which would indicate a close-in contact. Upon hearing the 

OOD-2ís announcement, the qualified ESM operator told the unqualified operator to 

announce, ìNo close contacts.î 

Emergency Evolutions. The CO testified that because there were ìno visual 

contactsî and because both sonar and ESM had reported no threat contacts, ìI called [an] 

emergency deep as a training evolution. . . . It was obvious that it took the control room 

party by surprise, which, for a training evolution of this type, I intended to do.î 

By the time that the CO ordered the emergency deep dive, about 1340, the FTOW 

had entered three solutions for S-13 using a range value of 3,000 yards. The fire control 

system display continued to indicate that his solution was accurate. Reconstructed system 

data show that, at 1339:50, the Ehime Maru was at a range of 2,236 yards, or 1.10 

nautical miles. (See figure 8.) The FTOW later stated that, just before the emergency 

main ballast tank (EMBT) blow, he adjusted the range in his solution to 9,000 yards 

based on the fact that the CO had just completed a visual search and not reported seeing 

any close contacts.28 

As the submarine descended, the CO asked the quartermaster the course to P/H, 

and the quartermaster responded that it was 340°. The CO then ordered a course change 

to 340° to head the submarine toward its return point. 

 

27 Naval Warfare Publication 3-55.42 stipulates that the ESMís defensive aural search should be 

conducted in the same time as the OODís initial search for close contacts, that is, within 24 seconds.

28 Data indicate that the FTOW changed the range to 9,000 yards after the collision. 

 23 NTSB/MAB-05/01
The guests stated that the CO then asked them whether they would like to 

participate in the vesselís upcoming evolution, which was the EMBT blow. During this 

maneuver, high-pressure air is used to force water out of ballast tanks as rapidly as 

possible to bring the submarine back to the surface in the shortest possible time. For the 

maneuver, the CO personally assigned one guest to sit in the helmsmanís chair and 

operate the helm controls and stationed another guest to operate the valve levers that 

released the high-pressure air into the main ballast tanks. A third guest was stationed at 

the diving alarm. Experienced crewmembers supervised the visitors at the controls 

throughout the evolution, and the CO narrated what was happening for the visitorsí 

information during the submarineís ascent. The FTOW said that during the EMBT blow, 

the civilians who were standing were ìholding on to stuffówhatever they could grab 

onto to help stay up.î 

The sounding of the alarm was the signal to begin the emergency blow maneuver. 

At this time, witnesses reported, the guest at the high-pressure air controls operated the 

levers under close supervision of Navy personnel, and the submarine started to rise at a 

sharp angle. The guests recalled that, shortly afterward, there was a loud noise, and the 

submarine shuddered. The guests quoted the CO as saying, ìWhat the hell was that?î 

After the submarine slowed and the periscope could be raised, the CO looked into the 

periscope and announced that the submarine had struck another ship. (See figure 10.) 

Figure 10. The collision between the Greeneville and the Ehime Maru occurred about 9 

miles south of Oahu, Hawaii, at position 21°05.5′ N, 157°49.1′ W. Dotted line indicates 

the edge of the submarineís assigned submerged operating area.

 24 NTSB/MAB-05/01
The FTOW said that immediately after the collision, he went into sonar and talked 

with the sonar crew to determine whether they still had the contacts they had been 

tracking. He said that he was surprised to learn later that the vessel struck by the 

Greeneville was indeed one of the contacts they had been tracking. He said that he 

assumed that the ship they hit had been ìdead in the water,î meaning its machinery was 

turned off. 

Sinking of the Ehime Maru

Personnel on board the Ehime Maru reportedly heard two loud noises and felt the 

fishing vessel shudder. The bridge crew all stated that they did not see anything before 

the collision. According to the Ehime Maruís master, ìThere was no ship at all nearby.î 

He stated that ìthe range of vision was goodî and that ìthere was no outline of a ship 

nearby on the radar,î a Tokimec model BR-3440MA-X59. He said that he then felt two 

impacts and the stern of the ship lifted up. 

After the impact on the fishing vesselís port aft quarter, the Ehime Maru bridge 

personnel looked aft and saw the submarine as it broached the surface of the water. The 

Ehime Maruís lookout said that after observing the submarine, he turned forward and saw 

diesel fuel squirting from the fuel tank vent on the forward port side of the fishing deck. 

The Ehime Maruís master said that he realized immediately that his vessel was in trouble. 

Within 5 seconds of the collision, the Ehime Maru lost all power, including the backup 

systems on the emergency generator circuit. He said that he tried to call for assistance 

using the VHF-FM marine band radios, but they would not work. The master directed the 

chief radio operator to activate the emergency position indicating radio beacon (EPIRB), 

a portable 406-MHz model with a hydrostatic release, that was installed immediately 

outside the pilothouse, on the port bridge wing. (See figure 11.) According to witnesses, 

the chief radio officer was wearing an automatically inflating lifejacket and was near the 

bridge when the vessel began to sink. No one recalled seeing him reentering the 

pilothouse, leaving the ship, or swimming in the water. 

Meanwhile, on the third deck (the lowest deck of the fishing vessel), the chief 

engineer, the first engineer, and the first oiler were in the engine control room when the 

oiler said he heard a loud scrape and then felt an impact. He said that the space 

immediately went black, and water and fuel flooded the area with such force that he was 

ìviolentlyî knocked about. He said that he could not recall how he was able to escape the 

engineroom but thought that water gushing in had carried him through the engineroom 

and up through a deck opening to the second deck. From there, he climbed up the ladder 

and out of the vessel. He said that he never saw the chief engineer and the first engineer 

after the impact. 

At the same time, on the second deck, the nine students who survived the accident 

had just finished lunch and were either in the crew mess or in cabins that were 

immediately forward of the mess. The four students in the crew mess went directly aft. 

The students in their cabins said that when they looked out into the passageway, they saw 

 25 NTSB/MAB-05/01
Figure 11. Side view of the Ehime Maru and plan views of the decks. 

 26 NTSB/MAB-05/01
water and oil gushing up the stairwell from the deck below. The Ehime Maru was 

equipped in the berthing areas and at the watch stations with automatically inflating 

lifejackets that met the standards of the International Convention for the Safety of Life at 

Sea, 1974 (SOLAS), as amended. Most of the surviving students were able to retrieve the 

lifejackets from their cabins; other students said that they did not think to do so. They 

said that as they went aft in the passageway, they had to wade through an ankle-deep 

mixture of oil and water. Most of the students first went to the fantail area, or stern 

overhang, of the main deck. From there, they went to the mustering station aft of the 

pilothouse. 

All survivors reported gathering in the muster area behind the pilothouse. Several 

witnesses stated that after it settled in the water, the Ehime Maru then sank by the stern at 

a 30° to 45° angle within 5 minutes of the collision. As the ship began to submerge, some 

people went into the water or were washed off by the waves coming over the stern. The 

remaining personnel attempted to climb a ladder to get onto the top of the pilothouse. 

Two students were washed off the ladder into the sea. Other students and crewmembers 

reached the top of the pilothouse only to be washed off by waves as the vessel sank. The 

oiler stated that he injured his shoulder when a wave washed him against a searchlight 

mounted on top of the pilothouse. Survivors carried underwater with the sinking ship 

either swam up to the surface or their lifejackets automatically inflated and carried them 

up. Witnesses from the submarine and the Ehime Maru reported that, after the fishing 

vessel sank, the water was covered with a heavy sheen of oil. 

The Ehime Maru also carried 10 SOLAS-approved liferafts in containers mounted 

with hydrostatic releases that were designed to activate when the vessel sank to water 

depths ranging from 5 to 25 feet. The raft containers would then float to the surface and 

be automatically inflated by ìtag linesî attached to the vessel with breakaway links. 

According to personnel who escaped the vessel and made it to the waterís surface, 

the liferafts functioned as designed, and survivors were able to climb into them. The 

second engineer wound up in a raft by himself. He said that the submarine approached 

him and its crewmen called out to him. He yelled back, but the English/Japanese 

language barrier prevented him from understanding them. 

Emergency Response 

After determining that the Greeneville had struck a surface vessel, the submarine 

CO reported the collision to the Navyís COMSUBPAC operations center at 1348. 

COMSUBPAC center personnel, in turn, notified Navy command personnel and Coast 

Guard GroupñHonolulu by both landline telephone and VHF-FM marine radio. The 

Coast Guard and then the Navy began sending search-and-rescue assets to the scene. For 

a chronology of response events between the collision and the recovery of the Ehime 

Maruís survivors, see appendix C. An in-depth discussion of response activities follows. 

Response Efforts by the Greeneville. After the submarine struck the Ehime 

Maru, the Greenevilleís engineering officer took over as OOD during the response effort 

and initiated rescue and assistance measures as required by Operations Procedure (OP) 

 27 NTSB/MAB-05/01
61-19.29 In addition, a medical treatment station, manned by a hospital corps technician, 

was established in the officerís wardroom. 

The OOD stated that he and a petty officer manned the bridge, which was located 

inside the submarineís sail, within 6 minutes of surfacing. The fishing vessel had already 

sunk, so the OOD conned the submarine toward the Ehime Maruís rafts and debris while 

the petty officer looked for survivors in the water. Control room personnel searched the 

area using both periscopes. Because of rough seas, the main deck hatches could not be 

opened; the only outside access was through the sail access trunk.30

The OOD and the lookout were joined on the bridge by the CO and two divers. In 

preparation for retrieving the fishing boatís occupants, the divers, who were trained in 

basic first aid, rigged a Jacobís ladder, which is a rope ladder with wooden or plastic 

steps, down the side of the sail. 

As the submarine neared two rafts of survivors, the OOD called out to and tried to 

communicate with the people; he said that he was not successful, however, because of the 

English/Japanese language barrier. He saw one person who appeared to be injured lying 

in a raft. He said that because he had been advised that Coast Guard resources were soon 

due on scene, he elected not to put a diver in the water. He further stated, however, that if 

the submarine crew had seen any people from the Ehime Maru in the water before the 

Coast Guard boats arrived, he would have had a diver go to their aid. 

Actions by COMSUBPAC. When COMSUBPAC received initial notification at 

1348, its command personnel assumed search-and-rescue mission coordination for the 

Navy response and identified immediately available Navy resources to dispatch to the 

accident site. At 1355, COMSUBPAC watchstanders notified Coast Guard Groupñ

Honolulu of the accident. Navy officials said that, during the initial phase of the response, 

they dispatched Navy vessels and aircraft independent of the Coast Guard response. 

However, COMSUBPAC maintained an open telephone line to Coast Guard Groupñ

Honolulu to keep apprised of developments. 

According to Navy officials, at 1504, based on information received about the 

scope of the accident, COMSUBPAC transferred search-and-rescue mission control of 

the dispatched Navy assets to the Coast Guard. (See next section.) The COMSUBPAC 

operations center continued to independently identify and launch Navy air and sea 

resources, notifying the Coast Guard when the response assets were en route. 

 

29 The Naval Sea Systems Command has published the rescue and assistance procedures contained in 

the Los Angeles Class ship systems operations manual as a separate classified reference document, OP 61-

19. The OP includes the actions to take and which crewmember is responsible for taking them should 

certain types of emergencies occur. The reference document also lists the precautions and the safety 

limitations that the rescue and the assistance details must follow when responding to an emergency. 

30 Videotape taken by the Coast Guard response helicopter shows large waves washing across the 

Greenevilleís main deck. 

 28 NTSB/MAB-05/01
Coast Guard Response. According to the duty officer at Coast Guard Groupñ

Honolulu communications center, when he received notification at 1355 of a collision in 

the area south of Diamond Head, he assumed responsibility as search-and-rescue mission 

coordinator for the case, in accordance with the agencyís standard operating procedures. 

He first ordered a Coast Guard HH-65A helicopter (No. 6570) on routine air patrol to 

divert to the accident site and then ordered Coast Guard StationñHonolulu to send rescue 

boats to the scene. 

Coast Guard StationñHonolulu initially dispatched two vessels: a 21-foot rigid 

hull inflatable boat (RHIB) with 3 crewmembers and a 41-foot patrol boat with 7 

crewmembers, including an emergency medical technician. The Group duty officer said 

that when he realized that the Coast Guardís standby cutter, the Kittiwake, was several 

hours away from the accident site, he ordered the recall of the Coast Guard cutter 

Assateague, which was at home base in a maintenance status. The Assateague, staffed 

with off-duty personnel from several cutters, got under way within 1 hour of notification. 

Helicopter No. 6570, with two pilots, a hoist operator, and a rescue swimmer on 

board, arrived at the site at 1427, about 45 minutes after the collision, and assumed 

command of the on-scene response. The helicopter pilot centered on the rafts and debris 

and, at 1446, began a sector search for people in the water. 

In the meantime, the RHIB and the patrol boat arrived at the scene at 1431 and 

1444, respectively. The RHIB went from raft to raft, counting people, identifying who 

had sustained injuries, and searching for someone from the Ehime Maru who spoke 

English. According to the coxswain on the RHIB, the master of the Ehime Maru was 

located in a raft and taken on board. The fishing boat master and the RHIB crew 

continued to count survivors in the rafts and determined that 9 people were missing. The 

Coast Guard responders radioed a report about the missing personnel to Group Honolulu. 

When the Coast Guard patrol boat arrived on scene at 1444, the helicopter 

lowered its rescue swimmer by hoist to the boat, which then maneuvered next to three 

liferafts that were tied together. The rescue swimmer moved from raft to raft, assessing 

the condition of the survivors and treating those who were injured. He immobilized the 

arm and shoulder of the injured oiler and, using bottled water from the raft survival kits, 

flushed the eyes of those who had eye irritations from the diesel fuel. 

The RHIB retrieved and ferried survivors from the other rafts to the patrol boat, 

where the EMT-trained crewmember medically assessed their conditions. The on-scene 

responders then distributed the 26 survivors between the two Coast Guard boats and 

returned to Coast Guard StationñHonolulu, arriving there about 1615. 

Joint Rescue Coordination Center Response. At 1505, the Joint Rescue 

Coordination Center31 assumed the responsibility of search-and-rescue mission 

 

31 The national search-and-rescue plan designates the Coast Guard as the U.S. aeronautical and 

maritime search-and-rescue coordinator with overall responsibility for the Honolulu region. The agencyís 

 29 NTSB/MAB-05/01
coordinator from Coast Guard GroupñHonolulu because of the building magnitude of the 

case. During the early response, the Joint Rescue Coordination Center did not control or 

coordinate the influx of Navy resources into the search; however, once the Joint Rescue 

Coordination Center was advised of the responding Navy resources, center personnel 

directed the Navy assets to specific search areas and assigned the search patterns. 

About the time that the patrol boat and the RHIB were retrieving the Ehime Maru

survivors, the Coast Guard diverted a C-130 aircraft to the site to relieve helicopter 

No. 6570 of the on-scene command for the surface and air assets. The Coast Guard cutter 

Assateague subsequently assumed on-scene command of the search and rescue. 

Honolulu Emergency Medical Services. The Honolulu emergency medical 

services dispatcher, working through the communications networks of local hospitals, 

determined the space availability at the medical facilities and routed ambulances from the 

Coast Guard Station. The four most seriously injured individuals were taken to Straub 

Hospital, which treated three of the injured for nausea and eye and throat irritations 

stemming from diesel fuel ingestion or hypothermia. The oiler was diagnosed with a 

fractured right clavicle and hospitalized for 5 days. 

Because of a lack of available space at Straub Hospital, the remaining five Ehime 

Maru occupants requiring medical attention were taken to Kaiser Permanente Medical 

Center, where they were treated for eye irritations caused by the diesel fuel and released. 

None of the missing personnel was seen after the Ehime Maru sank, either by the 

survivors, Greeneville crewmen, or other rescue personnel. 

Extended Search Activities 

Coast Guard or Navy units were on scene continuously for 22 days, searching for 

missing personnel. Two civilian vessels of Japanese registry also participated in the 

search. Initial attempts to locate the fishing vessel were unsuccessful because of bad 

weather and because of an erroneous report of the accident site. The Safety Board 

assisted the Navy in determining the location of the Ehime Maru by acquiring radar data 

from the U.S. Air Force 84th Radar Evaluation Squadron and the Federal Aviation 

Administration (FAA) and filtering the data to plot a track of the Ehime Maru that 

correlated with the time, heading, and speed reported by the master of the fishing vessel. 

(See discussion in ìSafety Board Performance Studyî section.) The Navy then moved the 

search area to the end of the radar track. 

On February 16, Navy sonar detected a vessel and, at 1129, Navy personnel were 

able to identify the fishing vessel by maneuvering a remotely operated vehicle, the 

Scorpio II, so that its video cameras displayed the Ehime Maruís stern plate. The vessel 

was sitting almost upright in 2,003 feet of water about 1,000 yards from the reported 

 

Joint Rescue Coordination Center, based in Honolulu, is operated by the Fourteenth Coast Guard District 

and is jointly staffed by Coast Guard and Air Force personnel. 

 30 NTSB/MAB-05/01
collision site but almost directly under the end of the radar track. For the next week, two 

underwater remotely operated vehicles, the Scorpio II and the Deep Drone, searched the 

Ehime Maruís exterior and the sea bottom surrounding it for the nine missing persons, 

with no success. The search effort was suspended on March 2. 

Salvage Operations 

To retrieve the bodies of the Ehime Maruís missing occupants, the Navy 

contracted to build a specially designed lifting and spreader assembly, which could be 

operated from a diving support vessel with heavy lift capability. On October 12, 2001, 

the Rockwater 2 lifted the Ehime Maru about 100 feet above the ocean floor and 

transported the suspended fishing vessel to a shallow-water recovery site about 115 feet 

deep near the Honolulu International Airportís reef runway. A team of Navy and 

Japanese divers then recovered the victimsí bodies, personal effects, and mementos, and 

videotaped the vessel damage. After the search was complete, the Ehime Maru was 

transferred 16.5 miles out to sea, where it was lowered into its final resting place. 

At the request of the families of the victims, their bodies were not autopsied and 

were returned to Japan. The body of the ninth accident victim could not be located, and 

he is presumed dead. 

Damage Surveys 

Ehime Maru. An underwater survey of the vesselís bottom revealed a cut in the 

hull that began on the starboard side inboard of the bottom near the deckhouse front. (See 

figure 12.) The cut, between 2 to 3 feet wide, ended on the port side shell in the vesselís 

engineroom, where it extended vertically from the vesselís bottom to 11.5 feet (3.5 

meters) above it (the design waterline mark). 

Figure 12. According to diver reports, the line of cut in the Ehime Maru extended from 

frame 21 to frame 54 through both the bottom and the innerbottom of the doublebottom 

vessel. The cut, therefore, resulted in breaches in the student lounge, the access 

stairwell to the student lounge, the engine control room, and the engineroom. 

 31 NTSB/MAB-05/01
The cut proceeded from forward to aft of the vessel and breached the vesselís 

innerbottom32 in the student mess, the stairwell, and the engine control room. The cut 

then proceeded through the bulkhead between the control room and the engineroom, 

leaving a vertical cutout in the bulkhead that was the approximate shape and size of the 

Greenvilleís upper rudder. The vertical outline of the rudder was also visible on the port 

side shell of the Ehime Maruís engineroom, through which the submarineís upper rudder 

had exited the fishing vesselís hull. The line of cut had breached several doublebottom 

(DB) tanks; going forward to aft these tanks included No. 2 fuel oil DB tank (starboard), 

No. 3 fuel oil DB tanks (starboard and center), and No. 4 fuel oil DB tank (port) in the 

engineroom. Both the outer and innerbottoms had been cut through. Damage to the 

control room and to the interior of the student mess and vertical stairtower on the port 

side of the computer room was visible during the survey. The open vertical stairtower 

allowed water to immediately flood upward to the upper deck levels of the vessel. 

Greeneville. Safety Board investigators conducted a damage survey of the 

Greenville in drydock at Pearl Harbor Naval Shipyard. Investigators found that the sail of 

the submarine showed no damage. Immediately below the sail, the acoustic hull surface 

treatment (tiles) on the portside hull had been sheared off in an elliptical pattern about 24 

feet long. 

The upper rudder, located at the submarineís stern, showed the greatest impact 

damage. The damage began at the 31-foot draft mark and extended all the way to the top 

of the upper rudder on both its port and starboard sides. Surface tiles had been sheared off 

exposing bare metal over most of the rudder surface, and there were several indentations 

on the rudderís leading edge. One of the larger indentations had punctured the metal skin 

on the port side. The anchor light had been sheared off the top of the rudder. Other 

scrapes and missing paint seen on the hull were correlated by the Navy to previously 

existing wear and tear on the ship. The propeller area had not been damaged. 

Safety Board Performance Study 

As noted earlier, the Safety Board assisted the Navy in locating the sunken fishing 

vessel by obtaining Air Force and FAA radar data and extracting the Ehime Maruís 

trackline. Safety Board engineers also used the radar data as well as own-ship, sonar, and 

fire control data retrieved from the Greenevilleís sonar data logger (SLOGGER) to 

conduct a performance study of the Greeneville, the Ehime Maru, and other surface 

vessels around the time of the accident. Excerpts from that study are summarized below. 

Note that the study and all the plots exclude the classified speeds and depths exceeded by 

the submarine during the visitor cruise. 

The complete performance study is part of the public docket maintained on this 

accident by the Safety Board at its headquarters in Washington, D.C. For additional 

 

32 The Ehime Maru had a doublebottom design, meaning the bottom of the ship had a compartment 

used for fuel, ballast, and so forth that was topped by a shell plating. This plating is referred to as the 

innerbottom. 

 32 NTSB/MAB-05/01
details on the development of the tracks of the Ehime Maru and the Greeneville and the 

plots comparing all nonclassified recorded data and fire control solutions, see the public 

docket. 

Ehime Maru Track 

To determine the position of the Ehime Maru, Safety Board engineers sorted the 

radar data obtained from the Air Force and the FAA and removed any radar return that 

was not south of the radar site or that originated from aircraft with transponders. The 

remaining radar returns were plotted as a function of time to identify radar tracks, that is, 

consecutive radar returns. The radar data having the characteristics of surface ships (slow 

speed, no aircraft transponder return) were obtained from Honolulu airport, which uses 

Airport Surveillance Radar Model 9 (ASR-9). The airport radar antenna has an elevation 

of 68.1 feet and a magnetic variation of 10.5° E. The Safety Board converted azimuth and 

range data to east and north position from this antenna using the Tracks software 

program. One track visible in one of the plots ended at 2343 Universal Coordinated Time 

(UTC), or 1343 local time. This was later established as the time of the collision, initially 

from witness interviews and then from system data. 

The radar tracks in the plots were separated and compared with sonar data. One 

track ended at the wreckage site and at the 2343 UTC collision time (as seen in own-ship 

data). This radar track was considered to be the Ehime Maru. The track showed the 

Ehime Maru moving at 11 knots on a heading of 166°. 

Greeneville Track 

The digital audio tape (DAT) information captured from the sonar interface unit 

consisted of TARed (a UNIX compression standard) ASCII data, which Safety Board 

engineers uncompressed on a UNIX workstation, transferred to a computer, and recorded 

onto a CD-ROM. The files consisted of data for the Greenevilleís motion (own-ship 

data), towed-array parameters,33 and sonar and fire control data parameters. The recorded 

own-ship parameters consisted of time, heading, pitch, roll, depth, and speed. Angular 

data were obtained from the inertial navigation system. All own-ship data were recorded 

once a second; however, some data points were missing and the recording time sequence 

was occasionally offset briefly. Because the speed and direction of a submarine cannot 

change much in 1 second, Safety Board engineers manually repaired the bad data points. 

From the own-ship data, the Safety Board developed the plots shown below. Figure 13 

shows the Greenevilleís keel depth and heading for the period between the ascent to 

periscope depth and the collision.34 

 

33 Because the towed array was not deployed, the towed-array parameters were columns of zeros. 

34 The keel depth data held 90.84 feet for 7 seconds immediately before the collision. The Safety 

Board worked with the Navy to determine the cause of this false reading, but nothing conclusive was 

determined. 

 33 NTSB/MAB-05/01
Figure 13. Keel depth and heading of the Greeneville between the ascent to periscope 

depth and the collision.

Integrated Tracks 

The integrated plot of the Greeneville track and the Ehime Maru track developed 

by Safety Board engineers appears in figure 8. The Safety Board also developed a threedimensional representation of the Greeneville and Ehime Maru tracks, beginning with the 

submarineís ascent to periscope depth and ending at the wreckage site. (See figure 14.) 

4.0

4.5

5.0

5.5

6.0

6.5

-500

-400

-300

-200

-100

0

-15.0

-14.5

-14.0

-13.5

 North (N. Mi)

 East (N. Mi)

Greeneville Dives and turns left

Ehime Maru Track

Depth (ft)

Figure 14. Three-dimensional representation of the Greeneville and Ehime Maru tracks, 

showing the submarineís ascent to periscope depth, the diving left turn, the collision with 

the Ehime Maru, and the return to the wreckage site. Note that depth is not to scale with 

east and north position.

 34 NTSB/MAB-05/01
Postaccident Actions by the Navy 

Navy Court of Inquiry 

General Findings. On February 9, 2001, the COMSUBPAC ordered an official 

inquiry into the collision between the Greeneville and the Ehime Maru. In its final report, 

the court of inquiry issued 26 recommendations, which, among other actions, included 

disciplinary measures against shore-based officials and six Greeneville crewmembers and 

reviews of various programs and procedures for adequacy and compliance. 

Disciplinary Actions. Based on the findings and recommendations of the court 

of inquiry, the Greenevilleís CO was taken to Admiralís Mast,35 where he was found 

guilty of committing two violations of the Uniform Code of Military Justice: dereliction 

of duty and negligent hazarding of a vessel. He was ìdetached for causeî from his 

position as CO, which was documented in his Navy officer record. He submitted a 

request to retire, which was approved, and he retired effective October 1, 2001. 

The OOD-2 was taken to Admiralís Mast, where he was counseled for failing to 

execute his duties to ensure the safe navigation of the ship and to properly supervise 

watch personnel in the control room. The FTOW was taken to Captainís Mast for failing 

to report a closing sonar contact (the Ehime Maru) in accordance with standing orders. 

The XO and the chief of the boat were both admonished for lack of oversight and 

execution of the enlisted watchbill.36 The sonar supervisor was admonished for his poor 

watchstanding and backup of the contact management team and his failure to ensure that 

only qualified personnel stood watch in sonar. 

The FTOW and the sonar supervisor were required to requalify before standing 

another underway watch in their supervisory positions. 

Program Reviews. The court of inquiry report stated that various programs and 

operating procedures should be reviewed for adequacy and compliance. Table 2

summarizes the tasks the court recommended that COMSUBPAC or the Navy should 

accomplish. 

 

35 Mast is an administrative proceeding where a senior officer can impose nonjudicial punishment for 

disciplinary offenses that do not merit courts-martial. 

36 Some individuals listed on the watchbill were not on the vessel and, no one was initially assigned to 

the fathometer watch, which is a station that must be manned when operating within 10 miles of land. The 

sonar supervisors switched personnel to accommodate for the oversight. The Navy found that, on the day of 

the accident, 9 of the 13 watch stations during the second underway were not stood by the individuals 

assigned to them. Several crewmen switched watches with a fellow crewmember without advising their 

supervisors or obtaining their permission to change duty assignments. 

 35 NTSB/MAB-05/01
Table 2. Court of inquiry recommendations and actions taken 

Task Actions Taken 

Ensure compliance with operating 

standards that permit only fully qualified 

sonar technicians to stand sonar watch. 

In June 2001, COMSUBPAC issued guidance by classified 

message to subordinate echelons and all Pacific Fleet 

submarines reemphasizing sonar watchstanding requirements. 

The message directed that under-instruction sonar watchstanders 

be supervised by a qualified watchstander assigned on the 

watchbill to that station, not by the sonar supervisor. Compliance 

with sonar watchstanding qualifications and sonar watchstanding 

proficiency is now routinely inspected during the interdeployment 

training cycle. 

Review the adequacy of the 

COMSUBPAC Operational Risk 

Management (ORM) program. 

COMSUBPAC conducted an internal audit of COMSUBPAC to 

ensure compliance with Navy ORM instructions in OPNAVINST 

(Chief of Naval Operations instruction) 3500.59. In June 2003, 

Commander of Naval Forces instruction 5040.12 was revised to 

require that ORM be used in interdeployment training cycle 

inspections and assessments. 

Review the ability and means of 

submarine squadron commanders and 

their staffs to provide meaningful 

oversight and objective feedback to 

their submarine commanding officers 

and crews during the interdeployment 

training cycle. 

On August 28, 2002, a classified COMSUBPAC instruction was 

revised to include comprehensive interdeployment training cycle 

management. A squadron commander now conducts a 2-week 

assessment early in each submarineís interdeployment training 

cycle to identify, among other things, the strengths and 

weaknesses in basic submarine operations. The assessment 

results are used to focus training during the interdeployment 

training cycle to prepare the submarine crew for its next 

overseas deployment. 

Coordinate a review of submarine 

open-ocean search-and-rescue capabilities and requirements with the lead 

type commander and make appropriate 

recommendations to the Chief of Naval 

Operations. 

Naval Warfare Publication 3-50.1 (rev. A) promulgates Navy 

doctrine for search-and-rescue operations. The publication is 

subject to periodic review and update. It has been updated by 

change on three occasions since February 9, 2001. No changes 

were suggested by the Navyís court of inquiry report and none of 

the intervening changes relate specifically to submarine open 

ocean search-and-rescue operations. 

Review the maritime traffic density of 

the Hawaiian operating area with the 

Coast Guard and other appropriate 

government agencies every 3 years. 

A COMSUBPAC memorandum, dated April 23, 2001, now 

requires a maritime traffic density review for submarine force 

training agendas. 

Provide information and training to the 

force concerning the Greeneville

collision. 

On April 23, 2001, COMSUBPAC sent a ìlessons learnedî 

message to all COMSUBPAC COs. The message was followed 

by a classified joint message from the commanders of the U.S. 

Atlantic and Pacific submarine forces, summarizing the main 

findings and opinions of the investigation as approved by the 

Commander of the Pacific Fleet. All submarine wardrooms and 

senior enlisted quarters have conducted training on the factors 

that contributed to the collision. A case study of the collision 

between the Greeneville and the Ehime Maru has become part 

of the curriculum at each level of tactical training for submarine 

officers. In addition, each wardroom is required to train on this 

case study annually. 

The court of inquiry report concluded that the Navyís distinguished visitor 

program should be fully supported. However, the court recommended that the 

COMSUBPAC coordinate with the Chief of Naval Operations and the Naval Chief of 

Information to conduct a complete review of Navy public affairs policy and guidance on 

 36 NTSB/MAB-05/01
the embarkation of civilian visitors, and to issue new guidance that was internally 

consistent, clear, and more specific. The report also recommended that the approval 

authority for distinguished visitor embarkations be delegated to commanders at the type 

level, which is the second echelon to the fleet command. In the case of the Pacific 

submarine fleet, the type commander was the COMSUBPAC. 

Regarding the conduct of distinguished visitor cruises, the court of inquiry 

recommended that COMSUBPAC identify which evolutions were appropriate for 

demonstration and reemphasize to the force that classified operational depths and speed 

limits are inappropriate for civilian cruises. The court of inquiry further recommended 

that COMSUBPAC establish a formal means for disseminating feedback or sharing 

information regarding distinguished visitor experiences across the command. 

Revision of Instructions Addressing Visitor Cruises 

At the Navyís court of inquiry, the COMSUBPAC testified that the Navy had 

both Secretary of the Navy instructions (SECNAVINST) and OPNAVINST addressing 

distinguished visitor cruises, a ìtinyî but ìextremely importantî part of the Navyís 

civilian outreach program.37 COMSUBPAC had issued operations orders and instructions 

pertaining to visitors on ships; however, the COMSUBPAC guidance documents 

basically iterated the policies put forth in the instructions issued by the Chief of Naval 

Operations and the Secretary of the Navy. 

Neither of the publications cited by service officials contained requirements for 

ensuring the safety of civilians embarked on Navy vessels.38 The instructions also did not 

address the procedural issues of whether and when civilians should be permitted in the 

control room or the sonar room and, if so, how many visitors should be allowed. The 

guidance did not indicate whether or when interaction between visitors and watchstanders 

should be allowed or define the role of the CO during a visitor cruise. In addition, the 

instructions did not specify which maneuvers should be conducted for the benefit of the 

distinguished visitors or, more importantly, prohibit any deviation from standing orders 

that might jeopardize the submarine, its crew and passengers, or vessels in the vicinity of 

the submarineís operating area. 

Following the Greeneville collision with the Ehime Maru, chapter 4 of 

SECNAVINST 5720.44A was revised in May 2002, transferring the oversight for 

 

37 In calendar year 2000, the entire Pacific fleet sponsored 176 guest embarkations, providing cruises 

for about 8,000 civilians. Of the 176 cruises, COMSUBPAC had 51 embarkations for 1,354 guests. Of the 

COMSUBPAC guest embarkations, 12 cruises carrying a total of 215 civilian visitors originated from Pearl 

Harbor. The COMSUBPAC stated that this total was less than the total embarkations in 1999, when 

SUBPAC hosted 227 civilians on 18 visitor cruises that originated from Pearl Harbor. 

38 In addition, none of the 26 Department of Defense, Navy, and Marine Corps documents cited as 

references for SECNAVINST 5720.44A addressed safety measures for civilian visitors on Navy ships, nor 

did they include procedural differences in submarine operations that were unique to visitor cruises. 

 37 NTSB/MAB-05/01
distinguished visitor embarkations to commanders at fleet level, which for Naval forces 

in the accident area was the Commander, U.S. Pacific Fleet. 

In August 2003, COMSUBPAC issued COMSUBPACINST 5720.1, which 

contained procedures for handling public visits on Pacific Fleet submarines that 

supplemented SECNAVINST 5720.44A, Commander of Naval Submarine Forces 

(COMNAVSUBFOR) OPORD 2000 (appendix 4), and SECNAVINST 5510.34. 

COMSUBPACINST 5720.1 procedures stipulate rules and requirements for each 

distinguished visitor embarkation on a Pacific Fleet submarine. The section pertaining to 

civilian distinguished visitor cruises states, ìCivilian embarkations pose a degree of risk 

that must be properly managed.î 

The revised COMSUBPAC instructions address omissions in previous guidance 

documents, for example, interaction between watchstanders and visitors, the conduct or 

prohibition of certain maneuvers, and whether and how many civilian visitors should be 

permitted in the control room during certain evolutions. The instructions specify, in part, 

the following: 

• Visitors should receive an introductory safety brief that advises them of what 

to expect in an emergency and how to don protective gear. 

• Embarkations are to remain unclassified. The ship will not exceed unclassified 

depth or speed. 

• The CO ìwill ensure guests do not inhibit the safe operation of the ship.î 

• One crewman will be assigned as a dedicated tour escort for every four to 

eight guests, and the watchbill will include those crewmembers serving as tour 

escorts. The escorts will have no other assigned responsibilities during the 

underway. 

• The crewmembers assigned as tour escorts should be selected ìto ensure first 

the safety of the visitors, then satisfy their information needs.î 

The procedural changes now require that requests for cruises be submitted in 

writing through the submarineís chain of command either to the COMSUBPAC or, if the 

hosting submarine is deployed, to the fleet commander. The requests must include a 

schedule of key events, and the force commander must review the planned maneuvers in 

terms of appropriateness for the assigned operating area, taking into consideration the 

shipping and fishing vessel density, water depth, and any other hazards to safe conduct. 

The August 2003 instructions prohibit allowing civilian visitors to operate any 

equipment; however, as part of the event schedule submission, the CO may propose 

allowing civilians to operate certain equipment during specific events while under the 

direct supervision of a qualified watchstander. Such a proposal must be approved by the 

force commander. 

COMSUBPACINST 5720.1 permits up to 24 visitors, including noncrew escorts, 

on a civilian embarkation. The criterion for selecting an escort who accompanies the 

 38 NTSB/MAB-05/01
guest groups is ìto ensure first the safety of visitors, then satisfy their information needs.î 

The CO or his agent must review the itinerary developed for the visitors for areas of 

ìconflict,î that is, where overcrowding might occur. 

In addition to the required procedures, COMSUBPACINST 5720.1 contains 

recommended actions for ensuring the safety of ship operations. For example, the initial 

briefing to visitors should be conducted in the mess facility during the outbound transit so 

that the piloting party can function without distraction. To ensure that the control room is 

not overcrowded during evolutions, the plan of the day should include two surface and 

dive evolutions, the implication being that a guest group of 24 should be divided and 

fewer visitors allowed in the control room at one time. To ensure that the crew is not 

distracted while making preparations to go to periscope depth, the visitors should be 

taken to the mess facilities, where they can watch a movie or a monitor linked to the 

PERIVIS. 

Oversight Changes 

During his interview with Safety Board investigators, the COMSUBPAC Deputy 

Chief of Staff for tactics and training described several ìsubtleî changes affecting 

squadron oversight of the Greeneville that were not recognized as having a combined 

detrimental impact until the Navy investigated the collision. 

The COMSUBPAC deputy pointed out that a ship typically comes back from one 

deployment and deploys again within about 15 months. Because the Greeneville was a 

test platform for the Advanced SEAL Delivery System, it was not in the squadronís 

regular deployment rotation. As a result, Squadron 1 conducted fewer observations of the 

Greeneville and made fewer formal reports on its operations than in the past. 

Beginning in 1999, the Navy changed the required oversight practices for the 

squadrons. Instead of stipulating that, at a minimum, the squadron conduct a tactical 

examination on a ship every 12 to 15 months, the Navy keyed the tactical examination to 

the vesselís interdeployment training cycle. As a result of the Greenevilleís extended 

interdeployment training cycle, the squadron had not conducted a formal tactical 

examination since 1998, when the submarine was fitted with the Advanced SEAL 

Delivery System. 

About the same time that the Navy changed the squadron oversight standards, it 

also reorganized the squadron commands, which resulted in staff reductions. According 

to the COMSUBPAC deputy, during the transition period from the old to the new 

squadron command organization, the oversight infrastructure of the commands was 

ìprobably not well focused.î 

The COMSUBPAC deputy said that while the squadrons were being reorganized 

and oversight practices were being changed, the newly appointed commander to 

Squadron 1 ìwas struggling with another boat that had a . . . series of problemsî but that 

was on a deployment cycle and had to be ready to go to sea by the end of December 

2000. He said that when the Squadron 1 commander and other senior personnel visited 

 39 NTSB/MAB-05/01
the Greeneville, the ìsuperficialî indicators of readiness all looked good. The boat was 

clean. The crewmembers were ìpositive . . . happy with their leadership . . . and proud of 

their organization.î Moreover, crew retention was good. 

The COMSUBPAC deputy said, ìIf we had taken the time . . . and studied in 

detail . . . the fundamental practices on the ship, I think that we would have seen the 

harbingers of problems.î He stated that since the Greeneville collision, the Navy has 

changed the method for evaluating submarines. All boats are evaluated regularly, 

regardless of their deployment cycles. The focus is on forcewide performance in a 

particular area. The evaluation is a multistep process: 

• Basic submarine assessment. Evaluate the submarine crewmembers to 

determine their fundamental understanding of their jobs and responsibilities. 

• Corrective actions. Identify and monitor actions to correct problem areas; 

evaluate the weak areas the next time the vessel goes to sea. 

• Second formal review. Two inspections are conducted 6 to 8 or 9 months after 

the basic assessment to check the shipís readiness to deploy. The first 

inspection is conducted by the squadron commander, the second by the 

COMSUBPAC staff and training office. The inspection team ìbaselines them 

against everyone else.î The squadron commander then directs the CO to 

correct identified problems. 

At a minimum, a ship must receive a passing grade on three major tactical events 

in a 15-month period. In addition, the submarine must pass two engineering inspections. 

Squadron personnel are on board and watching and tracking the shipís procedures during 

all events. Every ship is graded to an absolute common standard by the use of grade 

sheets. The squadron deputy told Safety Board investigators, ìI think thereís a great deal 

of sensitivity . . . to readiness, almost to the point that weíve overcorrected in a way.î He 

said that, in late 2001 and early 2002, two or three ships had not left on time because of 

unreadiness detected in the inspection process. 

Operational Risk Management Program Changes 

The Navyís court of inquiry found that, ìHad Greenevilleís CO and crew been 

practicing the basic tenants of ORM, the collision may have been avoided.î The court of 

inquiry recommended that COMSUBPAC review the adequacy of its current ORM 

program.39 The stated purpose of the Navyís ORM program is to minimize risks to 

acceptable levels, proportional to mission accomplishment. The Navyís ORM is a closed-

 

39 Finding 66 and recommendation 8 of the court of inquiry report (Record of Proceedings, Court of 

Inquiry into the Circumstances Surrounding the Collision Between USS Greeneville [SSN 772] and 

Japanese M/V Ehime Maru That Occurred Off the Coast of Oahu, Hawaii, on 9 February 2001, U.S. Navy, 

April 13, 2001). 

 40 NTSB/MAB-05/01
loop process that supervisory personnel use to identify and control hazards. The process 

involves the following five steps: 

• Identify hazards; 

• Assess hazards; 

• Make risk decisions; 

• Implement controls; and 

• Supervise. 

The level of an ORM analysis is time-critical, deliberate, or in-depth, depending 

on the situation. The depth and formality with which a supervisor conducts an ORM is 

guided by the following four principles: 

• Accept risk when the benefit is greater than risk; 

• Accept no unnecessary risk; 

• Anticipate and manage risks by planning; and 

• Make risk decisions based on the right level of analysis.40

As noted in table 2, following the adjournment of the court of inquiry, 

COMSUBPAC conducted an internal audit of its operations to ensure compliance with 

Navy ORM instructions. In addition, Navy instructions were subsequently revised in 

2003 to include assessments of the use of ORM in training inspections. 

Course and Training Changes 

After the Greenevilleís collision with the Ehime Maru, the Navy revised its basic 

submarine course and all officer training, including the content of courses, entrance tests, 

and final examinations, the conduct of training, and the appropriateness of assignments 

for skill development. The courses now integrate the lessons learned from the Greeneville

accident. 

 

40 OPNAVINST 3500.39A. 

 41 NTSB/MAB-05/01
Analysis 

In its review of the events in this accident, the Safety Board determined that 

qualified and experienced members of the combat management team (the conning officer, 

the FTOW, and the sonar supervisor) as well as senior officers who happened to be in the 

control room failed to follow procedures designed to ensure safety in operations. The 

teamwork problems demonstrated on the day of the collision were due in part to the COís 

overly directive style, particularly with the OOD-2. However, the failure of key 

watchstanders to effectively perform their duties and communicate vital information to 

the conning officer contributed to the COís committing the following critical errors: 

• Failed to perform adequate contact analysis; 

• Rushed the procedures for moving to periscope depth; and 

• Ordered an emergency surfacing maneuver in the direction of a contact. 

Contributing to the operating errors of the combat systems team was their failure 

to adequately manage the civilian visitors so that they did not distract the watchstanders 

from the efficient execution of their duties. A detailed discussion of the operating errors 

follows. The analysis also considers the design of the Ehime Maru and the survivability 

of the fishing vessel in the accident. 

Failure to Perform Adequate Contact Analysis 

To accurately determine the range, course, and speed of a vessel contact, the 

combat systems team needed to interact to ensure that a sufficient change in the contactís 

bearing rate was generated. For the visitor cruise, the Greeneville had no established 

track. The submarine sailed almost straight south and then, with the exception of one 

baffle clear, almost straight north while operating at a keel depth of 600 to 650 feet 

during much of the submerged underway. According to Navy officials in charge of 

tactical training, a crew can do ìsolution development without maneuvering the ship by 

using a variety of ranging techniques,î and ìoperating at 600 feet reduces or minimizes 

the need for a precise solutionî until the submarine is preparing to go to periscope depth. 

Navy officials who testified at the court of inquiry or who were interviewed by Safety 

Board investigators indicated that TMA could have been performed either immediately 

before or immediately after the Greeneville conducted the evolutions, so long as it was 

conducted before the submarine proceeded to periscope depth. Thus, it was not 

inappropriate for the combat systems team to wait until later in the underway, shortly 

before preparing to surface, to concentrate on contact (or target) motion analysis. 

Problems arose, however, when both the sonar supervisor and the FTOW made 

assumptions about the contacts, including S-13 (the Ehime Maru), which later resulted in 

their providing incomplete and erroneous information to the CO. When sonar acquired 

S-13, the sonar supervisor correctly assessed that the vessel was distant and that it was 

 42 NTSB/MAB-05/01
not showing much of a bearing rate. However, when the bearing rate remained small for 

more than 40 minutes, he incorrectly assumed that the vessel was island traffic, on a 

distant course, and probably moving away from the submarine. He thus failed to properly 

assess the potential risk, anticipate a dangerous scenario, and advise the CO that the 

Greeneville, steering 000°, and the S-13 (the Ehime Maru), bearing 358°, were on closing 

courses. 

The FTOW indicated that sonar did not designate any of the contacts as merchant 

ships. He stated that ìjust being in Hawaiian waters,î he assumed that the contacts were 

typical of the ìtraffic around here . . . probably trawlers, fishing vessels [and] pleasure 

crafts.î He too thought that S-13 was distant and did not enter a tracking solution for the 

contact for 16 minutes (between 1240 and 1256). As further evidence that he did not 

consider S-13 a threat contact, at 1257:45, he changed his tracking solution for S-13 to 

place it on an opening course despite having no analysis showing that the contact was 

actually opening. 

Problems were exacerbated when the CO did not use all his resources to correctly 

assess the current operating situation when preparing for the conduct of the evolutions in 

the control room. He elected to confer with his trusted senior petty officers, first visiting 

sonar, where he was briefed by the supervisor, and then stopping at the fire control 

station, where he talked with the FTOW. The CO later stated that he had assumed that the 

OOD-2 had conducted TMA and had been confident that the young conning officer knew 

where the submarine was in relation to the contacts; yet, he never discussed the contact 

picture with him. The OOD-2 was aware that the combat systems team ìdid not have a 

great contact picture of where [S-12 and S-13] wereî before the evolutions began. For his 

part, the OOD-2 assumed that some evolutions would be cancelled because the 

submarine was due back at P/H at 1400 and that a senior officer would brief him about 

the changes. The CO and the OOD-2, as the first- and second-level officers in the 

operational chain of command, should have conferred, not only about the contacts, but 

also about the safe completion of the voyage. 

The CO testified that he went into sonar to assay the contact picture for himself. 

He recalled that in his discussion with the sonar supervisor, he was told that sonar held 

two contacts, a merchant vessel to the northwest [S-12] and a surface craft to the 

northeast [S-13, the Ehime Maru]. The sonar supervisor told the CO that the contacts 

ìwere distant, [and] up by land,î and more than 10,000 yards away. Thus, the CO 

assumed that the contacts posed no danger. The sonar supervisor did not advise the CO 

that S-13 had not shown any bearing drift for 40 minutes, that the course of the 

Greeneville had been on a straight south/north track throughout most of the cruise, or that 

the submarine and S-13 were on closing courses. Had the sonar supervisor communicated 

this information, the CO might have recognized the potential risk and not taken the 

operational shortcuts that he later did. 

The CO then entered the control room, where he said he reviewed the fire control 

monitors and discussed the contact status with the FTOW. The fire control technician 

made almost the same comments about the contacts being typical Hawaiian marine traffic 

as the sonar supervisor had done, which reinforced the COís opinion about the position 

 43 NTSB/MAB-05/01
and course of the contacts. When he approached the conn, the CO then observed and 

recalled that the AVSDU was not working. If he had reviewed the CEP, which the 

FTOW maintained until an hour before the evolutions, the CO might have realized that 

the movements of the contacts and the submarine had been inadequate for good contact 

analysis. Instead, he chatted with the visitors, advising them where to stand for the best 

view of the evolutions, which prompted several civilians to position themselves in front 

of the CEP, blocking the COís view of it and the FTOWís access to it. 

Rushed Procedures for Movement to Periscope Depth 

At the onset of the angles and dangles, rather than properly oversee the OOD-2 by 

having him direct vessel movements that the CO could verify as being correct, the CO 

essentially took over the conn without acknowledging that he was doing so. He ordered 

specific depths and turns, which the OOD-2 repeated to the diving officer and the 

helmsman. As the captain of the submarine, the CO had the authority to assume the 

conn.41 However, by removing himself as backup to and overseer of the OOD-2, the CO 

eliminated a measure of safety redundancy that the Navy had developed for operations. 

During the high-speed turns, which lasted between 5 and 6 minutes, the sonar 

display was scrambled, making it difficult if not impossible for the sonar crew and the 

FTOW to determine the accuracy of the contact picture. About 1331, as the submarine 

was beginning to slow on course 340°, the CO abandoned the checks and balances 

stipulated in his standing orders and started taking procedural shortcuts that adversely 

affected the ability of his crew to improve their contact awareness, thereby jeopardizing 

the safety of the cruise. He ordered the OOD-2 to complete preparations to go to 

periscope depth within 5 minutes, which the CO said even a veteran OOD would 

probably have difficulty accomplishing. 

The OOD-2 attempted to complete the preparations for going to periscope depth, 

an involved process requiring him to conduct several tests, instrument checks, and, 

perhaps most important, a briefing with key watchstanders to share information about the 

sonar contacts. Through this vital communications step with the sonar supervisor, the 

FTOW, the radioman, the ESM, and the navigation supervisor, the OOD-2 could have 

ascertained whether the conn needed to order additional movements to improve the 

TMA. 

Meanwhile, the CO had left the conn to go into sonar, where he watched the 

monitors as two contacts, S-12 (bearing 316.6°) and S-13 (bearing 016.3°), reappeared, 

respectively, at 1332:03 and 1332:48. He later stated that the displays led him to believe 

that the contact picture had not changed, whereupon he returned to the control room. 

 

41 Navy operating procedures stipulate that the CO announce when he is assuming the conn and that 

the conning officer (in this case, the OOD-2) announce, ìThe captain has the connî to the watchstanders, 

and ìSir, I have relinquished the connî to the CO. 

 44 NTSB/MAB-05/01
The Greeneville was arriving at 150 feet, the depth at which the OOD-2 

reasonably would order TMA maneuvers, when the CO returned to the conn about 1333 

and immediately ordered a course change to 120° to clear the baffles. The COís actions 

of interrupting the OOD-2 and reassuming the conn resulted in the OOD-2 not holding 

the required briefing to discuss the contact environment. Again, the CO did not discuss 

the contact situation with the OOD-2. For his part, the OOD-2 did not speak up and 

advise the CO that he had not been able to determine whether additional TMA was 

warranted. Thus, the two officers again failed to communicate necessary information to 

one another that would have pointed out the need for improved contact awareness. 

The COís order to change course meant that he allowed the Greeneville to remain 

on the 340° leg less than 2 minutes (1331:36 to 1333:03), rather than the 3 minutes 

stipulated for TMA in Navy operating procedures. More important, the submarine was on 

a steady speed and course (to 340°) less than 25 seconds before the course change to 120° 

began. The baffle clear turn was complete about 1335; however, the CO then ordered the 

submarine to proceed to periscope depth at 1336:45. Consequently, he did not hold 

course long enough on either the 340° leg or the 120° leg to permit good TMA, a serious 

error. 

The Safety Board constructed a hypothetical Greeneville track, extending the 

340° and the 120° legs to 3 minutes each to allow for proper TMA. Figure 15 

superimposes the hypothetical track over the actual Greeneville track. As shown in the 

chart, the too-rapid course changes on the actual track resulted in no bearing rate change, 

which is necessary for accurate identification of the contactís course. 

Figure 15. Comparison of Ehime Maru bearings with Greenevilleís actual track and with 

hypothetical track calculated for 3-minute legs.

 45 NTSB/MAB-05/01
The hypothetical track using 3-minute legs produced bearing rate changes that 

would have readily revealed the course of S-13 to both the sonar crew and the FTOW. 

The Greenevilleís bearing to the Ehime Maru on the hypothetical 3-minute legs would 

have been as follows: 

Beginning of 340° legÖÖ012.1°

End of 340° legÖÖÖÖ..033.0°

Beginning of 120° legÖÖ050.1°

End of 120° legÖÖÖ.Ö.061.8°

The Safety Board determined that the rate of bearing change would have been 

about 7° per minute on the 340° leg and 4° per minute on the 120° leg if the legs had 

lasted the required 3 minutes. Thus, the total S-13 bearing change that the Greeneville

crew could have obtained if the submarine had stayed on each of the TMA legs for 3 

minutes is about 50°, as opposed to a bearing change of about 10° for the actual leg. Such 

a large bearing change and accompanying rate of bearing change would have alerted the 

sonar crew and the FTOW to the close proximity of S-13 (the Ehime Maru). Moreover, 

the large bearing changes would have provided sufficient input for the FTOW to develop 

a high-confidence solution for S-13 that would have placed it nearby and closing. 

The COís conning of the vessel compromised the ability of the combat systems 

crew to verify the contact picture in other ways. The turn that he ordered for the baffle 

clear put one of the known sonar contacts, S-12, bearing 316.5°, into the baffle area, the 

result being that sonar lost the track on the vessel. During the turn, sonar gained S-14, 

bearing 358°, a potential threat contact to the submarine. The FTOW, having no solution 

on S-14 and believing that S-13, now 4,200 yards away, was not operating near the 

Greeneville, began to concentrate on S-14 to the exclusion of S-13. However, he could 

not resume determining solutions for the contacts until the submarine steadied on course 

120°, about 1334. 

Meanwhile, the CO did not respond appropriately to the sonar supervisorís 

announcements about the loss of S-12 and the gain of S-14 by determining either their 

status or whether he needed to conduct additional TMA. Possibly he did not hear the 

sonar announcements, or perhaps he did not recognize the implication of sonar 

announcing the loss of one contact and the gain of a new contact. The CO later told 

Safety Board investigators that he probably would not have made the errors that he did if 

the AVSDU had been working and he had been able to refer to the sonar repeater. 

The COís comments reflect an operating failure that existed on board the 

Greeneville during this underway. Neither the CO nor the senior members of the combat 

systems team (OOD-2, sonar supervisor, and FTOW) demonstrated effective ORM when 

compensating for the inoperable sonar repeater in the control room and for the presence 

of the civilian visitors near key watchstations. ORM is a decision-making tool used by 

the Navy and other organizations to increase operational effectiveness by identifying 

potentially hazardous conditions and adopting procedures aimed at reducing or mitigating 

the potential for loss. On the Greeneville, the standard procedure for compensating for 

 46 NTSB/MAB-05/01
the loss of the AVSDU was for the conning officer to periodically visit the sonar room to 

assay the contact picture. However, the OOD-2 never visited the sonar room after 

conducting his prewatch checks. 

The CO chose to compensate for the loss of the AVSDU by twice visiting the 

sonar room and reviewing the monitors there. Upon returning to the conn after his second 

visit to sonar, he ordered a course change to 120° to clear baffles about 1333. About the 

same time that the CO was explaining the purpose of a baffle clear to the civilian visitors, 

sonar gained S-14 at 1333:03. Thus, the CO may not have recognized that the sonar 

supervisor was announcing a new contact. The COís possible error as well as the failures 

discussed later in this analysis, under ìManagement of Civilian Visitors,î demonstrates 

that the combat systems team should have assessed the combined impact on operations of 

the inoperable AVSDU and the presence of civilians near the fire control station and the 

conn and devised better methods for communicating contact information to the conning 

officer.

Before the Greeneville rose to periscope depth, the CO announced to everyone in 

the control room that he had a ìgood feelî for the contacts, which had the effect of 

discouraging backup from his crew. The inexperienced OOD-2 acquiesced to the more 

experienced commanding officer, and the seasoned FTOW discounted a solution at his 

fire control station indicating that S-13 (the Ehime Maru) was 4,000 yards away or less. 

The XO, who had told the OOD-2 that he would go to sonar and relay contact 

information to him, said nothing to either the OOD-2 or the CO to ensure that the conn 

had accurate information about the contacts. 

The CO continued to rush, pushing his crew and truncating recommended steps 

for safe operation. While at periscope depth, he interrupted the OOD-2ís periscope sweep 

and took over operating the periscope, executing only a few brief sweeps in the general 

area where he believed the sonar contacts to be. The CO then ordered the submarine to a 

shallower depth (from 60 feet to 58 feet), raising the periscope 2 feet for a greater height 

of eye. On this day, the seas were choppy, 3 to 4 feet; the sky was not clear. The CO 

either failed to recognize the need to compensate more for the choppy seas and the haze 

or simply did not do so. He did not order the submarine to a shallower depth for a 

significantly better height of eye and he did not execute a slower, more deliberate sweep 

to ensure that no vessels were obscured by the haze. Once again, he did not use his crew 

resources and solicit the feedback or assistance necessary for safety. Normally during the 

COís periscope sweep, the FTOW would assist him in putting the periscope on the 

precise bearings of the sonar contacts, a standard procedure that improves the probability 

of detection. On this day, the CO did not ask for assistance, and the periscope was not 

centered on the contactsí bearings. 

The crewís behavior immediately preceding the collision suggests that their errors 

were strongly influenced by the COís announcement about the contact picture. In effect, 

the COís flawed situational awareness regarding the proximity of vessels at the surface 

reinforced and influenced the watchstandersí own limited situational awareness. The CO 

was well regarded by his crewmembers, as evidenced by, among other things, the 

Greenevilleís high retention rate, but his popularity may have worked against optimal 

 47 NTSB/MAB-05/01
crew performance. That is, because of his rank and the respect among the crew that he 

commanded, his crew appeared to have acted as though they believed that if the CO 

thought the surface was clear, it was. 

The two-way communication necessary for effective bridge resource 

management42 was not evident on the Greeneville. The COMSUBPAC Deputy Chief of 

Staff for tactics and training told Safety Board investigators, 

The watchstanders had sort of an inherent trust in their commanding officer; they didnít 

speak up when they should have. [They believed that] . . . if the captain thinks itís okay to 

go up, who am I to stand in front of him and tell him itís not right, and they kind of just 

rolled on the captainís decision to go up. 

If crewmembers disagreed with the COís assessment, none spoke up to provide 

him essential feedback, particularly in the presence of the visitors. Every Greeneville

crewmember interviewed later by the Navy or by the Safety Board stated that he never 

doubted the assessment of the CO. After the collision, neither the sonar supervisor nor the 

FTOW believed that the submarine had struck a contact that they were tracking. 

Emergency Surfacing Maneuver Toward Contacts 

After his brief periscope sweep, the CO ordered an emergency deep dive. During 

the submarineís descent, he ordered a course change to 340°. Recorded data indicate a 

left turn during the dive, consistent with this command. He then announced an EMBT 

blow, an evolution that he had told the navigator he was going to cancel but later said that 

he decided to order on the spot for training purposes. Again, the COís actions 

demonstrate that he continued to fail to employ ORM during the conduct of this cruise. 

Navy trainers told Safety Board investigators that the operating instructions pertaining to 

EMBT blows are classified. They stressed, however, that before executing such an 

emergency surfacing maneuver, COs should do ìadditional risk managementî to ensure 

that the watchstanders have good information and existing conditions have been 

identified. 

In the case of the Greeneville CO, he took a series of procedural shortcuts rather 

than perform ORM before executing the EMBT blow. He did not establish effective 

measures for monitoring the sonar contacts. He did not ensure that effective TMA had 

been accomplished. He abandoned or truncated measures designed to promote safety 

redundancy in operations, including his proper oversight role of the conning officer and 

his conduct of the second periscope sweep. He did not use his crew resources effectively 

to ensure that he obtained good feedback about the operating environment. 

 

42 Bridge resource management, or BRM, is an operational mechanism for ensuring the safe 

completion of a vesselís voyage. The Coast Guard requires that operators of certain vessels, such as 

tankers, employ BRM, and the International Maritime Organization recommends that training for seafarer 

certification include BRM. (See International Convention of Standards of Training, Certification and 

Watchkeeping for Seafarers, 1978, as amended in 1995.) 

 48 NTSB/MAB-05/01
The COís actions after ordering the EMBT blow indicate that he added the 

emergency evolution for the benefit of the civilian visitors. For the evolution, he paid 

particular attention to ensuring that the civilian visitors were involved in it. He personally 

assigned one civilian to sit at the helm controls and allowed another to operate the levers 

at the high-pressure air controls, albeit under the supervision of experienced 

crewmembers. He then narrated what was happening during the submarineís ascent for 

the information of the passengers. 

The EMBT blow maneuver requires that a vesselís rudder be centered. Recorded 

data show that as the EMBT blow maneuver began, the vesselís turn rate slowed, 

consistent with a rudder centering. At the beginning of the EMBT blow, the submarineís 

heading was 025°. Thus, the COís conning order was a serious error that resulted in the 

submarine pointing in the direction not only of S-13, bearing 018°, but also S-14, bearing 

about 358°. 

As the Greeneville rose at a high speed, its heading continued to change slowly 

and was at 018° when the Greeneville struck the Ehime Maru, slicing open the bottom of 

the fishing vesselís hull. 

Management of Civilian Visitors 

In this case, the civilian visitors did not directly cause the accident; however, their 

presence on the submarine and the manner in which they were accommodated by the 

crew, especially the CO, had an adverse impact on the safety of operations. 

The Greeneville cruise on February 9 was conducted contrary to COMSUBPAC 

instructions, which stipulated that distinguished visitor embarkations ìmust be scheduled 

and conducted within the framework of otherwise planned underway operations, and 

should not be conducted solely to accommodate civilian guests.î The Greeneville had 

been scheduled to begin an underway for testing on February 9, and the civilian guests 

had been scheduled to ride the submarine during the first day of that underway. However, 

at the suggestion of the Greeneville CO, COMSUBPAC had delayed the start date for the 

test voyage until February 12 and had granted the Greeneville CO permission to take the 

civilian visitors on a 1-day voyage on February 9. 

The unintended effect of permitting such a cruise was that the crew did not 

demonstrate the attention to detail that they reportedly had exhibited during previous 

underways and training exercises. They either adopted a somewhat informal attitude 

toward their duties or concentrated on accommodating the visitors to the detriment of 

their work. 

In the findings from the Navyís court of inquiry, officials found fault with the 

senior crewís preparation of the watchbill for the visitor cruise. The Safety Board 

considered whether the poorly prepared watchbill and the crewís subsequent switching of 

watch assignments were factors in the accident and found that in all but one case, key 

watch stations were manned by qualified crewmembers. Only sonar lacked a required 

watchstander: an over-instructor to monitor the qualifying technician. Considering that 

 49 NTSB/MAB-05/01
the Greeneville rarely held more than three contacts, the sonar supervisor could have 

easily monitored the qualifying technician. However, he could not properly oversee the 

qualifying technician and efficiently perform his own duties while accommodating the 

civilian visitors. As evidence of this, he forgot to reset the sonar recorder after playing 

sound tapes for the enjoyment of the visitors. He also either did not observe the visitors 

distracting his crew or did nothing to prevent it once the demanding evolutions began. 

According to an off-duty sonar technician, when he returned to the sonar room 

about the time of the angles and dangles, several civilian guests were in the sonar room, 

in addition to the sonar supervisor, the broadband stack operator, and the workload share 

stack operator. He said that he noticed that the sonar supervisor and the sonar technicians 

were trying to talk to each other and the guests at the same time. The off-watch sonar 

technician said that the sonar operator at the broadband stack appeared not to be 

distracted by questions from the guests. The unqualified workload share stack operator, 

however, was trying to answer the visitorsí questions. At one point, the workload share 

stack operator started to turn away from the display to talk with the guests, but the offwatch technician indicated to him that he should watch the display. The off-watch sonar 

technician said that he then asked the visitors to leave the sonar room. While it is 

commendable that the off-watch sonar technician took action to improve the operating 

environment for the sonar crew, the sonar supervisor should have recognized the 

distraction that the visitors might pose to the watchstanders and asked the civilians to 

leave the sonar room before the evolutions began. 

Interaction with the guests created scheduling problems and changed the 

operational dynamic in the control room. The Greenevilleís activities for the visitor 

cruise, as listed on the plan of the day, remained reasonably on schedule until first the CO 

and then the XO each hosted a civilian group at lunch for an hour instead of the time 

allotted. The CO testified at the court of inquiry and later told Safety Board investigators 

that he realized that the submarine would be late returning to P/H because of the delay 

caused by the long lunches; however, he said that he did not rush the conduct of the 

evolutions to try and return the visitors on time. He indicated that if he had felt rushed, he 

would not have continued to sign souvenir photographs in his stateroom, but would have 

gone into the control room sooner to begin the evolutions. In his 2003 autobiography,43

however, he indicated that his rushed actions during the evolutions were driven by his 

knowledge that the civilian visitors needed to be back at Pearl Harbor by a given time for 

a later appointment. 

In the control room, the COís management of and interaction with the visitors 

created both physical and communication barriers for his subordinates. After he advised 

the civilians where to stand for the best vantage point of the upcoming evolutions, six to 

eight visitors stood on the starboard side of the periscope platform, blocking the FTOWís 

ready access to the CEP, which the FTOW was required by standing order to annotate to 

provide the conning officer with a display of the submarineís position relative to the 

position of known vessel contacts. The FTOW said that he stopped maintaining the CEP 

 

43 S. Waddle and K. Abraham, The Right Thing (Nashville: Integrity Press, 2003). 

 50 NTSB/MAB-05/01
because of the presence of the visitors. Given that the visitors also blocked the conning 

officerís view of the CEP, the FTOWís failure to perform this watch task did not affect 

the outcome of this accident because neither the OOD-2 nor the CO attempted to review 

the chart. 

Some of the civilians stood in front of two fire control system displays that the 

OOD-2 used to monitor the contact situation. The OOD-2 later told Safety Board 

investigators, ìI didnít have free access all the way over there.î 

Although the civilians impeded their work, neither the OOD-2 nor the FTOW 

asked them to move or told the CO that the visitors were adversely affecting operations. 

The CO was focused on directing the activities for the civilians rather than managing the 

civilians to ensure that they did not interfere with the watchstandersí execution of their 

duties. As a result, the FTOW was reluctant to speak up and interrupt him. Thus, the 

activities for the civilian visitors stymied communication and prevented the conn from 

receiving necessary feedback from the crew. 

As a result of the Navyís court of inquiry, in August 2003, COMSUBPAC issued 

new procedural requirements (COMSUBPACINST 5720.1) for handling in-port public 

visits and embarkations on Pacific Fleet submarines. The COMSUBPAC instructions 

include provisions designed to ensure not only that visitors remain safe but also that crew 

operations are not compromised during a civilian embarkation. The crewmembers 

assigned to oversee the civilian visitors while they are on the submarine must be listed as 

escorts on the watchbill and they cannot be assigned to a workstation. The CO or his 

agents are to review the itinerary developed for the visitors for areas of ìconflict,î for 

example, areas where overcrowding might occur when all or several civilians are present. 

Recommended procedures include conducting the initial visitor briefing in the 

mess facility during the outbound transit so that the piloting party can function without 

distraction. To ensure that the control room is not overcrowded during evolutions, the 

instructions recommend that the plan of the day include two surface and dive evolutions, 

so that a visitor group can be divided and fewer civilians permitted in the control room at 

one time. To ensure that the crew is not distracted while making preparations to go to 

periscope depth, the instructions recommend that the visitors be taken to the mess 

facilities, where they can watch a movie or a monitor linked to the PERIVIS. 

In addition to revising procedures directly related to visitor cruises, the Navy 

made changes in squadron oversight designed to address safety deficiencies that the 

Safety Board also noted in its investigation. For several reasons, the Greeneville was not 

subject to the type of oversight that should have revealed shortcomings in the crewís 

adherence to Navy operating procedures. Factors affecting squadron oversight included 

removal of the Greeneville from the regular deployment rotation when it was equipped 

with an Advanced SEAL Delivery System, realignment of the squadron and the resulting 

reduction in oversight personnel, and demands on the newly appointed squadron 

commander who was given the priority to prepare another submarine for deployment. 

 51 NTSB/MAB-05/01
The development and implementation of effective operating procedures for all 

phases of operations is a prerequisite for the safe operation of any vessel, military or 

civilian. Operating procedures in and of themselves, however, are insufficient to ensure 

safety unless they are accompanied by systematic oversight of their use by crewmembers 

or workers in regular operations. Effective oversight provides information not only about 

how individuals use or comply with operating procedures but also about whether the 

procedures, as written or established, are effective in an actual operating environment. 

As a result of the Greeneville accident, the Navy changed its method of evaluating 

submarines, regardless of their deployment cycles. The squadrons now employ a 

multistep evaluation process that includes, among other reviews and tests, a basic 

evaluation of the submarine crewmembers to determine their fundamental understanding 

of their jobs and responsibilities; identification of procedural problem areas or 

weaknesses and follow-up monitoring by squadron officials; and a second formal review 

to check a shipís readiness to deploy. 

The changes in squadron oversight procedures as well as the new requirements for 

distinguished visitor cruises demonstrate that the Navy has recognized the detrimental 

operating conditions that existed on board the Greeneville and has taken additional 

measures to address the safety of operations on board its submarines. Accordingly, no 

further action is warranted. 

Survivability of the Ehime Maru

The design of the Ehime Maru was typical for a ship of that size and service. In 

addition to meeting industry standards for strength, the ship was fitted with transverse 

bulkheads and a double bottom in the engineroom to provide a measure of flotation and 

stability in the event of moderate damage from collision or grounding. This is typical of 

modern ship design, and the standards reflect historical experience with damages and 

international consensus on a reasonable degree of protection that should be provided. The 

damage sustained by the Ehime Maru far exceeded the criteria used for design, and the 

simultaneous flooding of several watertight compartments immediately doomed the ship. 

The damage scenario is so unusual and extensive that it is considered impractical to 

modify the basis of watertight design for ships of this size. Accordingly, this accident 

does not constitute a reason for review or revision of international standards of 

subdivision and damage stability. 

Probable Cause 

The National Transportation Safety Board determines that the probable cause of 

the collision of the USS Greeneville with the Japanese fisheries training vessel Ehime 

Maru was the inadequate interaction and communication among senior members of the 

combat systems team (the commanding officer, the officer of the deck, the fire control 

technician, and the sonar supervisor), which resulted in the failure to perform adequate 

contact analysis and adhere to proper procedures for moving to periscope depth; and the 

commanding officerís decision to order an emergency surfacing maneuver. Contributing 

 52 NTSB/MAB-05/01
to the cause of the accident was the failure of the crew, in particular the commanding 

officer, to adequately manage the civilian visitors so that they did not impede operations. 

Contributing to the loss of life was the rapid flooding and sinking of the Ehime Maru, 

which occurred when the submarineís rudder tore through the fishing vesselís lower deck 

spaces. 

Adopted: September 29, 2005 

 53 NTSB/MAB-05/01
Appendix A 

Investigation 

The National Transportation Safety Board learned of the Greeneville/Ehime Maru

accident at 2118 on February 9, 2001, from news media reports. The Safety Board 

initially launched a five-person investigative team from the Office of Marine Safety, 

including the chief of the technical services division, an investigator-in-charge, an 

engineering specialist, a human performance specialist, and a survival factors specialist. 

A Board Member and representatives from the Safety Boardís Office of Government, 

Public, and Family Affairs joined the team, and the group arrived in Honolulu about 1545 

on Saturday, February 10, 2001. A naval architect and an aircraft structures specialist 

who was proficient in underwater recovery efforts subsequently joined the team. The 

naval architect documented the damage to the vessels, and the recovery specialist served 

as liaison to the Navy salvers. 

The Safety Board investigated the accident under the authority of the Independent 

Safety Board Act of 1974, as amended, according to the Safety Boardís rules. Team 

members interviewed the survivors of the Ehime Maru between February 11 and 13, 

2001. The team also interviewed Coast Guard personnel involved in the search and 

rescue, emergency medical services officials, the American Red Cross supervisor, and the 

harbor pilot who took the Ehime Maru out of Honolulu. The Safety Board began 

interviewing crewmembers of the Greeneville on February 13, 2001. However, at the 

time, the CO, the XO, and the OOD-2 declined to assist in the Safety Boardís accident 

investigation. These three officers were eventually interviewed by Safety Board 

investigators, as indicated below: 

• September 2001óthe OOD-2 

• November 2001óthe XO 

• March 2002óthe CO 

The Safety Board also interviewed the commanders of Squadrons 1, 3, and 7, the 

instructor of the prospective commanding officers course, and the COMSUBPAC Deputy 

Chief of Staff for tactics and training in March 2002, and the former COMSUBPAC in 

May 2002. 

The designated parties to the Safety Boardís investigation were the U.S. Navy, the 

U.S. Coast Guard, and Ehime Prefecture, Japan, owner of the Ehime Maru. 

 54 NTSB/MAB-05/01
Appendix B 

Abbreviations and Acronyms 

AVSDU Analog-Video Signal Display Unit 

CEP contact evaluation plot 

CO commanding officer 

COMSUBPAC Commander, U.S. Submarine Force, Pacific (also command 

office for U.S. Submarine Force, Pacific) 

EMBT emergency main ballast tank 

EPIRB emergency position indicating radio beacon 

ESM electronic support measures 

FAA Federal Aviation Administration 

FTOW fire control technician of the watch 

MHz megahertz 

OOD officer of the deck (Note: in this report, the OOD of the second 

underway watch is referred to as the OOD-2) 

OP operations procedure 

OPNAVINST Chief of Naval Operations instruction 

OPORD operations order 

ORM operational risk management 

PERIVIS periscope video system 

P/H ìPoppa/Hotel,î the unmarked seaward entrance to Pearl Harbor 

RHIB rigid hull inflatable boat 

SECNAVINST Secretary of the Navy instruction 

SLOGGER sonar data logger 

SNR signal-to-noise ratio 

SOLAS International Convention for the Safety of Life at Sea 

TMA target motion analysis 

UTC Universal Coordinated Time 

XO executive officer 

 55 NTSB/MAB-05/01
Appendix C 

Chronology of Events, February 9, 2001 

Accident Events 

Time Activity

Pre-0500 Fire control officer of the watch (FTOW) checks fire control equipment in control room and 

finds that everything operates correctly. 

Pre-0700 Navigator reports to commanding officer (CO) that the control roomís Analog-Video Signal 

Display Unit (AVSDU), which provides a backup display of sonar data, is inoperative. 

0730 CO greets 16 distinguished visitors at dockside as they board the Greeneville at Pearl 

Harbor. The distinguished visitors are assembled in the crewsí mess, where they are given 

a brief presentation, including a slide show, about the submarine. They are broken into two 

groups for tours of the vessel. 

0757 Greeneville departs berth. 

0933 Navigator assumes watch as officer of the deck (OOD). 

1017 Greeneville submerges. 

1045 CO joins first group of distinguished visitors for lunch at first seating, which is from 1045 to 

1145. 

1054 Deep dive. 

1103-1131 Dive to classified depth. 

1130 Underway watch change scheduled. 

FTOW assumes watch at fire control console. 

Sonar supervisor assumes watch in sonar room. 

1143 Main propulsion assistant assumes watch as officer of the deck (OOD-2) in the control 

room. 

1145 Executive officer (XO) joins second group of distinguished visitors for lunch at second 

seating, which is from 1145 to 1245. 

1200 Sonar supervisor, in preparation for planned maneuvers, checks sonar stack for loose 

gear. 

Ehime Maru departs Honolulu. 

1207 OOD orders course change to north (000°). 

1228:59 Sonar begins tracking contact Sierra 12 (S-12). 

1231:59 Sonar begins tracking contact S-13, bearing 358° (the Ehime Maru). 

1232:59 Fire control system automatically generates first solution for S-13. 

1240 OOD-2 orders baffle clear. 

1242:15 Greeneville changes course to 240°, and sonar drops tracks on both S-12 and S-13 when 

they enter the baffle area. 

 56 NTSB/MAB-05/01
Time Activity

1245 Greeneville resumes northerly course.

1257 Ehime Maru completes stowing anchor and increases speed to 11 knots. 

1306+/- XO advises CO that ship needs to start maneuver demonstrations if submarine is to meet 

the distinguished visitorsí scheduled return time to Pearl Harbor. 

1310+/- Visitors enter control room; CO goes into sonar room to assay contact picture. Observes 

two contacts (S-12 and S-13) to the north and northwest. 

1314 CO enters control room and talks with visitors, advising them of the best locations to 

observe the submarineís maneuvers. 

1315 Greeneville increases speed to 14 knots and begins angle maneuvers ranging in depth 

from 150 to 650 feet. 

1315-1324 Sonar supervisor and sonar operators, while attempting to track targets, interact with five 

visitors who enter the sonar room. 

1324+/- Sonar technician who returns to get his jacket asks visitors to leave the sonar room before 

Greeneville begins rudder maneuvers, or high-speed turns. 

1325 CO directs OOD-2 to order the following turns during the high-speed maneuvers: 

Greeneville to turn right from a course of 000° right to 140°. 

1326:27 Greeneville is steady on 140°. Time steady on course until next turn: 

16 sec. 

1326:43 Greeneville to turn left to 340°. --

1328:04 Greeneville is steady on 340°. Time steady on course: 23 sec.

1328:27 Greeneville to turn right to 120°. --

1329:47 Greeneville is steady on 120°. Time steady on course: 23 sec.

1330:42 Greeneville completes high-speed maneuvers and comes left to 340°. 

1331+/- CO directs OOD-2 to prepare to go to periscope depth and to be there within 5 minutes. 

1332 CO goes into sonar a second time to determine contact picture; watches as sonar regains 

S-12 at 1332:03 and S-13 at 1332:48. 

1332:54 Greeneville arrives at 150 feet from a depth of 

400 feet.

Total time above layer deptha is 91 

seconds.

1333 CO returns to control room; directs OOD-2 to order a baffle clear to course 120°. 

1333:03 Sonar begins tracking S-14. 

1334:48 Tracking solution entered for S-14; S-12 fades. 

1335 Baffle clear complete. 

OOD-2 orders sonar to report all contacts; sonar reports S-13 and S-14. 

1336 CO announces that he has ìgood feelî for contact picture (later stated that he thought the 

contacts were S-12 and S-13). 

 57 NTSB/MAB-05/01
Time Activity

1336:45 CO orders ship to periscope depth (60 feet). 

1337:48 As submarine ascends, fire control solution is updated, indicating S-13 (the Ehime Maru) 

is within 4,000 yards. 

1338 Submarine periscope breaks surface of water. 

1339 OOD-2 conducts three rapid 360° periscope sweeps and reports ìNo close contacts.î 

Under-instruction operator in ESM room reports ìNo close contactsî to the conn. 

1339:04 CO takes periscope from OOD-2 and orders the ship to 58 feet. 

1339:30 CO conducts periscope search in the direction where he believes S-12 and S-13 to be. 

1340+/- CO orders emergency deep. Total time at periscope depth: 66 sec. 

1340 S-14 fades. 

1340+ As submarine begins to descend, CO asks quartermaster the course to P/H. 

Quartermaster responds 340°, and CO orders turn to 340°. 

1340:34 Submarine starts to come left from 121° to 340°. 

1342:25 Greeneville initiates EMBT. 

1343:15 Greeneville collides with Ehime Maru. (Approximate heading of submarine is 018°.)

 aLayer depth is the depth from the surface of the sea to the point above the first major negative thermocline (area of 

rapid decrease in water temperature) at which sound velocity is maximum.

 58 NTSB/MAB-05/01
Search-and-Rescue Events 

Time Event 

1343 Collision occurs. 

1348 Ehime Maru sinks. 

1348 Greeneville bridge manned. 

1348 Greeneville radios report of collision to COMSUBPAC. 

1355 COMSUBPAC reports collision to Coast Guard GroupñHonolulu. 

1356 Coast Guard GroupñHonolulu diverts helicopter No. 6570 from patrol to scene. 

1358 GroupñHonolulu directs Coast Guard StationñHonolulu to launch rescue assets. 

1400 StationñHonolulu dispatches rigid hull inflatable boat (RHIB) and a patrol boat to scene. 

1400 Joint Rescue Coordination Center receives signal from Ehime Maruís EPIRB. 

1404 Joint Rescue Coordination Center identifies vessel as Ehime Maru. 

1406 Joint Rescue Coordination Center contacts Coast Guard GroupñHonolulu to investigate. 

1420 COMSUBPAC calls Joint Rescue Coordination Center. 

1427 Coast Guard helicopter No. 6570 arrives on scene. 

1431 Coast Guard RHIB arrives on scene. 

1444 Coast Guard patrol boat arrives on scene. 

1445 Coast Guard helicopter No. 6570 transfers its rescue swimmer to patrol boat. 

1445 COMSUBPAC sorties two torpedo retriever boats, Hawthorne 5 and Hawthorne 8. 

1446 Coast Guard helicopter No. 6570 begins area search. 

1451 Coast Guard diverts C-130 aircraft from training to scene. 

1505 Joint Rescue Coordination Center assumes control of search-and-rescue mission. 

1524 Coast Guard C-130 plane arrives and assumes on-scene command. 

1538 Coast Guard RHIB and patrol boat depart scene with 26 survivors. 

1615 Rescue vessels arrive at Coast Guard StationñHonolulu. 

 NOTE: Search for missing crewmembers continued between February 9 and March 2. Ehime Maru was located on the seafloor in 

2,000 feet of water on February 16. 

 59 NTSB/MAB-05/01