The Terrifying Accident That Decommissioned The USS Chopper

Sometimes, a navy vessel that's severely damaged cannot be repaired and the only solution is to send it to a watery gravy, so it's scuttled and sent to the briny deep. The USS Chopper (SS-342) was a Balao-class diesel-powered submarine operated by the U.S. Navy until it suffered a serious accident. 

Commissioned on May 25, 1945, the sub remained in service for over two decades. Like other subs in the U.S. Navy's sizable fleet, the Chopper performed admirably, taking part in various exercises, acting as a target vessel to assist in the training of gun crews aboard surface ships, and more.

There wasn't anything particularly special about the Chopper, but the incident that ended its service is certainly a memorable affair. The accident occurred in 1969, and it was such a chaotic and dangerous mess that nearly everyone serving aboard the vessel almost died. Fortunately, the Chopper survived this near-death incident, though the damage was so severe it led to its decommissioning. Chopper was put out of service later that year, and not long after she was stricken from the inventory, met its end off the coast of North Carolina.

On Feb. 11, 1969, the USS Chopper took part in an Anti-Submarine Warfare (ASW) exercise off the coast of Cuba. Things were going smoothly when suddenly, the sub inexplicably lost electrical power. At the time, Chopper was moving at about 10 mph at a depth of 150 feet, immediately angled down 86 degrees, and sank. Since the Chopper was a sub, dipping under the water wasn't necessarily bad in and of itself, but the vessel was out of control and careening towards crush-depth, as there's a limit to how deep a military submarine can go.

The sub dropped to 440 feet very quickly. With power problems, nobody aboard could communicate to try and course correct. Attempts were made to return to the surface, but within 60 seconds of losing power, Chopper was almost vertical. The sub continued to descend, reaching 1,011 feet in depth.  A Balao-class submarine's maximum depth was 600 feet. Fortunately, the hull held, and the submariners aboard survived.

The Chopper regained power after only a couple of minutes passed, and she shot to the surface at 87 degrees. She broke through the waves and plummeted back down 200 feet before rising and settling on the surface. The sub was able to return to port under her own power, but she was severely damaged. The crushing depth caused widespread damage, which was worsened via its rapid resurfacing, which undermined the boat's internal structure and hull, which took on water. Structural damage spread throughout the boat, and the Navy decommissioned her on August 27, 1969.

The investigation found that the sub lost its AC power, which should have been covered by the onboard DC-powered backup system. Instead, poor communication worsened the problem. Once the sub's down angle blew past 20 degrees, more mechanical failures followed, causing additional problems. Everything happened incredibly fast, but in the end, the sub made it to the surface — unfortunately, it did so too fast, exacerbating the structural damage.

The USS Chopper went through an incredible ordeal by rapidly sinking to nearly twice its intended operating depth, only to quickly shoot back to the surface. The incident was one of the worst non-combat accidents to befall a U.S. Navy vessel. The pressures placed upon the hull were tremendous, and the damage was widespread. Fortunately, only two submariners were injured, but not badly and nobody died, so only the submarine was damaged to excess.

While the sub could no longer serve in the Navy, it wasn't done being useful. She continued sailing in limited capacity for years. After she was decommissioned, Chopper received a new designation (AGSS-342) and sailed for the U.S. Naval Reserve in a training capacity. She was later redesignated IXSS-342 for training and salvage operations before meeting her end on July 21, 1976. The Chopper was acting as a target for the USS Spadefish (SSN-668) when she took on water, tore through her tethers, and sank to the bottom of the sea for the last time, settling on the seafloor 2.7 miles beneath the waves of the coast of North Carolina.