1. AFTER BATTERY ROOM HATCH

2. USS GRUNION After Battery Room Hatch Locking Wheel Hatch Dog #1 Locking Rod Yoke #2 Yoke #3 Yoke #1 Hatch Dog #2 Hatch Dog #3 Locking Rod USS COD

3. USS GRUNION After Battery Room Hatch Locking Wheel Hatch Dog #1 Locking Rod Yoke #2 Yoke #3 Yoke #1 Hatch Dog #2 Hatch Dog #3 Locking Rod Hatch Rubber Gasket/Seal

4. USS GRUNION After Battery Room Hatch Yoke #2 Snapped Locking Rod Yoke #1 Threaded Hole for Locking Rod Yoke #2 Snapped Locking Rod

5. Stress Fracture USS GRUNION After Battery Room Hatch USS GRUNNION Hatch Rim Stress Fracture Stress Fractures in threaded bronze yoke allowed the Locking Rod to pull out of threads Stainless steel liner around hatch accessway: Liner has been stripped and mangled from inward (wrapped around ladder) CRS LINER

6. (4) The hatch dogs are mounted to the inner hatch and pivot back and forth. When the locking rod moves in/out, the yokes cam the hatch dogs...out they lock hatch shut, in they unlock the hatch. (1) Turning the center crank, moves the locking rods in or out. (2) The locking rods are threaded into the backs of the yokes (3) The yokes are attached to the hatch dogs via an eccentrically off-set hole. USS GRUNION After Battery Room Hatch 1 2 3 Unused hatch dog mounting bracket; attachment lugs drilled to accept hatch dog mounting pin 4

7. USS GRUNION After Battery Room Hatch KEY FINDING: The Aft Battery Room Hatch locking system failed catastrophically from internal overpressure, cause as yet undetermined. Likely chain of events (not in order); Over-pressure/hydrostatic event Bronze casting of Yoke #1 cracks, letting locking rod pull out Locking rod of Yoke #2 snaps; Dog #3 deforms (mounting flange breaks/twists?) Hatch gasket is blown from mounting channel Hatch blows open Physical Evidence; Locking Rod on Dog #1 has pulled from the threaded portion of Yoke #1 Locking Rod on Yoke #2 has broken off at the base of the Yoke Locking Rods (#1 &2) are lying against the inner face of the hatch, unattached to the yokes Yoke #1 has rotated outward 180 degrees Yoke #2 has rotated outward 90 degrees Hatch dog assembly #3 appears deformed Hatch gasket/seal is looped around the hatch and outer decking cover Hatch access trunk CRS trunk liner destroyed