AFTER BATTERY ROOM HATCH

USS GRUNIONAfter Battery Room Hatch

Locking Wheel

Hatch Dog #1

Locking Rod

Yoke #2

Yoke #3

Yoke #1

Hatch Dog #2

Hatch Dog #3

Locking Rod

Locking Rod

USS COD

USS GRUNIONAfter Battery Room Hatch

Locking Wheel

Hatch Dog #1

Locking Rod

Yoke #2Yoke #3

Yoke #1

Hatch Dog #2

Hatch Dog #3

Locking Rod

Locking Rod

Hatch Rubber Gasket/Seal

USS GRUNIONAfter Battery Room Hatch

Yoke #2Snapped Locking

Rod

Yoke #1Threaded Hole for Locking Rod

Yoke #2Snapped Locking

Rod

Stress Fracture

USS GRUNIONAfter 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

(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 GRUNIONAfter Battery Room Hatch

12

3

Unused hatch dog mounting

bracket; attachment

lugs drilled to accept hatch dog mounting

pin

4

USS GRUNIONAfter 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