USN:
Balao-class submarine USS Chopper (SS/AGSS/IXSS-342) off Key West 1958
On 11 February 1969,
Chopper was participating in an ASW exercise off the coast of
Cuba with destroyer USS
Hawkins (DD-873) when her electrical power tripped off-line.
Chopper was making 7–9 kn (8.1–10.4 mph; 13–17 km/h) at a depth of 150 ft (46 m) with a slight down angle when she lost power.
Within seconds,
Chopper's angle increased to 45° down and her bow passed 440 ft (130 m) of depth. Because of the power loss, the officer of the deck was unable to communicate with the senior controllerman in the maneuvering room, but the senior chief petty officer in the maneuvering room, Ken Taylor, independently ordered both main motors back full. Despite the backing bell, blowing ballast, and other efforts to regain control of the submarine, the down angle continued to increase, and within one minute of the power failure,
Chopper was nearly vertical in the water, bow down.
Chopper's bow is estimated to have reached a depth of 1,011 ft (308 m), her stern reaching 720 ft (220 m).
The crew's efforts began to take effect.
Chopper lost the headway that was taking her deeper, and even began to make sternway. Her bow began to rise, reached level, and continued to climb.
Chopper began to ascend with a rapidly increasing up-angle until she was again nearly vertical in the water, now bow up.
About two minutes after losing electrical power,
Chopper shot through the surface of the ocean, nearly vertical. The entire forward section of the submarine, to the aft edge of the sail, cleared the surface before she fell back. Her momentum carried her down to a depth of about 200 ft (61 m) before she surfaced again, leveled out, and remained on the surface.
Chopper returned to port under her own power. Inspection discovered that her hull had suffered extensive structural damage during the deep dive and rapid ascent.
Chopper was decommissioned on 15 September 1969.
