NavSource Online: Submarine Photo Archive
Contributed by Don McGrogan, BMCS, USN (ret.)
Grunion (SS-216)
Hypotheses of the Sinking
To Additional Pages
Keel Laying - Loss
A Life & Beyond
Aftermath
Initial Discovery 2006
ROV Pictures of the Wreckage
Gato Class Submarine: Laid down, 1 March 1941, at the Electric Boat Co., Groton, CT.; Launched, 22 December 1941; Commissioned USS Grunion (SS-216), 11 April 1942; Final Disposition, last report 30 July 1942, reported overdue from patrol off Kiska Island, Alaska, 5 October 1942, all hands assumed lost; Struck from the Naval Register, 2 November 1942. Grunion received one battle star for World War II service.Specifications: Displacement, Surfaced: 1,526 t., Submerged: 2,424 t.; Length 311' 9"; Beam 27' 3"; Draft 15' 3"; Speed, Surfaced 20.25 kts, Submerged 8.75 kts; Complement 6 Officers 54 Enlisted; Operating Depth, 300 ft; Submerged Endurance, 48 hrs at 2 kts; Patrol Endurance 75 days; Cruising Range, 11,000 miles surfaced at 10 kts; Armament, ten 21" torpedo tubes, six forward, four aft, 24 torpedoes, one 3"/50 deck gun, two .50 cal. machine guns, two .30 cal. machine guns; Propulsion, diesel electric reduction gear with four General Motors main generator engines, HP 5400, Fuel Capacity, 97,140 gals., four General Electric main motors, HP 2740, two 126-cell main storage batteries, twin propellers.
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The related text here is the fruit of several letters written to this site and Bruce Abele. This is offered as a hypothesis to be tested and not presented as THE ANSWER. There are several features that fit into the picture of how the engagement occurred that I think are important to establishing a scenario that can account for all the eyewitness accounts of Aiura, Nakagawa, and Hamada (recognizing some chance for error or misinterpretation) and the current physical condition of the submarine. I put myself in LCDR Abele's shoes and I come up with the following: 1. Grunion was running on the surface early AM NE of the NE tip of Kiska...close enough to monitor the approaches but far enough out to avoid being surprised by what had been described as "significant ASW activity"...charging batteries and dumping garbage. From this position Grunion would have patrolled to intercept traffic into Kiska. This position would have been just north of the final engagement location above the Japanese symbols about 52N 10' and 177E 50' and she could intercept any traffic into Kiska harbor from any direction as the headland there and MacArthur Reef form a natural funnel. Crewmen dumping garbage had installed the rail along the hatch as it was foggy and dark and they didn't want to get disoriented and lose the hatch. Kano Maru is detected to SE fairly close due to no SJ radar (no antenna on Apr 42 photo) and poor visibility. Quick dive precludes removal of railing. Immediately they go to normal approach course...generally SW depending on relative bearing. Visibility couldn't have been that good looking into the fog and sun in SE (not sure of summer sunrise/sunset that time of year) so probably had little initial data to go on. The normal approach course was intended to place the submarine in a position to make an attack regardless of target heading and was used in such cases of limited initial target data. It is basically perpendicular to the bearing to the target. This drives them to a relatively low angle on bow (AOB) before true data can be determined. It also may have taken some time to locate Kano Maru in the periscope. Often lookout sightings from high in the shears on the surface were hard to obtain from the periscope 4 feet above the surface. This produced the less than optimum AOB at firing which allowed Kano Maru to turn into and avoid first torpedo (a ~45 degree torpedo track at impact would have been very low, maybe 15 degree starboard AOB or less at firing depending on range). Ten torpedos were all forward per last MSG. 2. Grunion is now very close as Kano Maru goes by. They are concerned about losing her in Kiska harbor/ASW defenses so they do a quick set up, so Grunion had to turn away and set up for another bow shot. This would take some time as she had to gain sufficient distance for torpedos to arm (> 500 yards) and complete a 180 degree turn to bring bow tubes to bear. Not sure why they fired only one torpedo here. Perhaps due to high AOB the spread would have been very small for multiple torpedos. 3. By now they have figured out the Kano Maru is losing way..."lets take our time... Give me a heading for a beam shot to port at 1000 yards.... we'll make a hole in the other side...help her sink". Heading given is based on current TGT course...but Kano Maru is still swinging (rudder is still hard over even though losing way). Intended to arrive near the Kano Maru's beam, it actually results in AOB 135 port...less than optimum but it will do as target is drifting. There may have been a reload of 3 torpedos during this run. Fire 3 bow torpedos at optimum ~700-1000 yds near zero gyro angle (Kano Maru is drifting, why not give the torpedos the best chance of hitting by lining it up). But with TGT speed of near zero, torpedos have minimal spread. It is possible Grunion reloaded 3 torpedos between second and third salvo. Or the torpedo Aiura thought was missing Kano Maru actually circled after he looked away. Two duds occur due to high impact angle breaking torpedo firing pin as discovered later in analysis of faulty torpedos...not because of min range! In any case, the last torpedo fired circles left. (I have been wondering about circling torpedos in relation to spread...maybe close spread due to TGT speed near zero causes interference from wake of preceding torpedo and causes torpedo to tumble some; causing a hard-over rudder...I think it was Ed Walson who told us something I didn't know...torpedos are "bang-bang" guidance. Rudder has 3 positions---hard left/right and center...so failure to hard over or erroneous gyro command from tumbled gyro could have the same result...just a thought). Again this is not critical. There are lots of documented circular runs. This circling torpedo's bubble trail matches exactly with Nakagawa's description and drawing. (see the Grunion website "attack Analysis") Many discount his description in favor of Capt Aiura's because he was an Army Medical officer whereas Aiura was a professional sailor. I, on the other hand, give great credence to his account versus Aiura's because: a. He had nothing better to do than watch and describe what he saw and he is a witness unbiased by preconceived misperceptions about how ships vs submarines operate. His position was closer to the torpedo tracks than Aiura on the Bridge. b. Aiura's account is biased by a surface sailor's view of submarine warfare. Aiura describes a final torpedo attack and turn that are not within submarine doctrine or capability. If Grunion started to surface 400 meters away from Kano Maru as described by Aiura after having turned 180 degrees to the left (and assuming at least a 100 meter turn radius...sub's length) that would mean that LCDR Abele fired his torpedoes at about 2-300 yards with a 90 right gyro angle. This is something he surely would not have done. He had more than adequate time to set up the shot as Kano Maru was drifting so there is no reason for him to have executed a shot with high gyro angles well inside min range. c. Aiura was Capt of a ship that had just been torpedoed. He had to have been very busy dealing with conning his ship, dealing with damage control, and trying to summon help from Kiska. I doubt he was standing on the port bridge wing casually observing the engagement for 20 minutes. I believe he received reports from lookouts of periscope sightings and torpedo tracks, rushed to the side to see for himself, and then went back to what he was doing when the event was over. Later he connected the dots between these different events to build his diagram of the entire engagement, probably with reference to the ship's log since his times are so distinct. 4. Sound reports circling torpedo tracking to left. "Right full rudder...all ahead full...up periscope"...looking for torpedo in periscope to try to avoid torpedo (described by Aiura as the long periscope exposure: "the sub kept periscope up and moved calmly ignoring Kano Maru ... then the sub seemed to begin to surface"). This turn would place Grunion on reciprocal course to Kano Maru ~ 400 meters away as Aiura continues to describe: "The conning tower made ripple on the surface and the wave began washing the conning tower". Sounds like a broach caused by diving officer losing trim due to 3-4 torpedos fired and rapid turn and acceleration, which would have been quickly corrected resulting in a return to proper depth (might have been interpreted as sinking if gun hit occurred right then). Aiura says "8 cm shot hit the washing wave, made water column and dull water explosion sound." Does not sound like a surfaced sub to me and apparently the sub sank from view immediately as he next describes "the swell of heavy oil." None of this sounds like a sub surfaced for gun action. I think torpedo hit shortly after the shell hit the water washing the conning tower upper works. As the torpedo hit the port side of the bow just FWD of FWD escape trunk (Port side of bow seems to be ripped and bent inwards; starboard side is a clean break mashed inwards by what appears to be impact with the bottom) the explosion occuring so soon after the shell hit and the submergence of the sub convinces Aiura and other Japanese they sunk the sub. It is also possible the magnetic exploder actually worked without having to impact in this case...wouldn't that be ironic after two duds. In any case, if it did hit, it would have been a high impact angle which did not tend to break the exploder firing pin so this one did not dud. 5. The explosion blows the ("bow") to starboard; ripping the metal on the port side and swinging like a gate along the seam on the starboard side, breaking it off & leaving the clean break we see on starboard side. This also accounts for the holes in the hull on the port side aft of the break while starboard is not holed. This also blows much of the decking off far enough back to release the marker buoy and at least 2 of remaining torpedos forward have their warheads blown off as they are liberated from FTP room and float to surface to be found 500 meters aft of Kano Maru, (all torpedo skids are damaged and bent and no torpedos remain in the wreck FWD). Sub immediately takes large angle down by bow due to lost buoyancy FWD and stern planes set to counteract the broach. Diving officer orders full rise on the planes but bow planes are gone...angle gets worse and, still at full speed ahead, speed builds up rapidly. Water flow between remaining deck forward and pressure hull forces decking upwards and away taking FWD portion of fairwater with it smoothly parting along forward edge of "covered wagon" supports going up and away over the top of periscopes. "All back full" might have come next but too late to stop plunge. Some ballast blow certainly would have been ordered also but ballast tanks forward were probably compromised by explosion and depth was probably building up too much pressure to overcome. Crush depth would have come quickly. At crush depth the compartments start to implode along the top centerline at the weak spot of the pressure hull. By the way...the gun is not trained upwards, it has fallen fwd down into the imploded hull giving the appearance of being pointed upwards. As After battery compartment implodes the pressure spike goes up the crews' mess hatch and blows it open unseating the hatch gasket which flows out but catches on the hatch wheel and loops around the hatch cover when sub hits bottom. Conning tower is crushed inwards until hatch seal breaks allowing water to rush in and equalize pressure. The conning tower is not fully imploded because, as it deformed, the hatch bent breaking the seal and equalizing the pressure. I have annotated the diagram here to show the part of the sub that is missing in red hatching. You can see the forward ends of main ballast tank #1 in the pictures of the broken off bow. 6. Now traveling very fast and steep, the sub hits the bottom mostly on starboard portion of bow that protrudes farther than port (and sub may have been rolled a little to starboard at impact) crushing in the right side of the bow break causing the necking we see. Sudden deceleration bends what remains of periscope shears and covered wagon structure forward. Also collapses aft part of upper fairwater sides and tips gun towards the bow and down into the implosion break making it appear to point skyward. Compression fracture occurs half way between bow and conning tower (this break appears to be compression in nature followed by separation as the stern came down). Stern bangs down bending rudder and the slide begins. Some of the other cracks could be implosion related, or impact as the stern came down. This picture illustrates the construction of the central portions of the Grunion where ballast and/or fuel tanks surround the sides and bottom providing for a weak spot along the spine where the hull would implode causing the caved-in appearance of the wreck. This picture illustrates the construction and location of the conning tower and covered wagon structure over it. The conning tower and the frame of the covered wagon is installed on the Pompon SS-(267). This picture shows the Gato's (SS-212) conning tower fairwater after it was cut down and illustrates the covered wagon structure which was enclosed on Grunion and is now exposed on the wreck: Here is Gato's fairwater before it was cut down. This is what Grunion looked like. All the structure forward of the red lines is gone on the wreck smoothly parted from the front of the covered wagon structure. This picture of the Gato shows the FWD escape trunk hatch and the marker buoy (still installed in this 1944 photo). The bow is missing from this hatch forward. All the decking is gone FWD. Grunion's gun was not in this position, it was aft. | Photo & text courtesy of John Hart. | |
 | 67k | Sketch by Jim Christley of the Grunion's (SS-216) wreck. 1. The general shape and size of the bow portion that is missing. 2. The forward bulkhead of the Forward Battery. I noticed that structural failure in this area took with it the structure in and around the torpedo loading hatch. 3. A major structural break which may have been caused by impact with the bottom. 4. The conning tower barrel with the reachrod type mechanisms for the helm. In later boats this was replaced by hydraulics, but the Grunion used electric planes and helm control. 5. A ‘debris’ or torn tankage area that deserves further study. I believe this is in way of a fuel tank and may point toward shell damage to the tank and possibly some internal piping. 6. Lines that indicate the the size of the pressure hull over the engine rooms. 7. A major hull break in way of the After Engine Room after bulkhead. |
Photo courtesy of ussgrunion.com. | |
 | 36k | Sketch by Jim Christley of the Grunion's (SS-216) wreck. The following PDF was produced by Christley, Galler & Thompson and represents a number of points to consider. | Photo courtesy of ussgrunion.com. Photo added 03/18/08. | |
DANFS history entry located on the Haze Gray & Underway Web Site.
Crew Contact And Reunion Information
U.S. Navy Memorial Foundation
Fleet Reserve Association
Additional Resources and Web Sites of Interest
On Eternal Patrol
ComSubPac Report of loss of USS Grunion (SS-216) July 30, 1942 - 70 Men Lost
Full Fathom Five, U.S. Submarine War Against Japan
ussgrunion.com
ussgrunionblog
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