Soviet submarine M-256
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| Ordered: | |
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| Launched: | |
| Commissioned: | |
| Fate: | wrecked by fire and sunk |
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| Stricken: | |
| General Characteristics | |
| Displacement: | 460 tons surfaced, 540 tons submerged |
| Length: | 56.0 m (183 ft 9 in) |
| Beam: | 5.1 m (16 ft 5 in) |
| Draught: | 3.8 m (12 ft 6 in) |
| Propulsion: | Kreislauf system: two 700 hp (520 kW) conventional diesel engines, one 900 hp (670 kW) AIP (LOX) diesel engine, one electric creep motor; three shafts |
| Speed: | 18 knots (33 km/h) surfaced, 16 knots (30 km/h) submerged |
| Range: | 2750 nautical miles (5090 km) at cruising speed on surface |
| Complement: | 30 officers and men |
| Armament: | 4 x 533 mm (21 in) torpedo tubes in bow, 8 x anti-submarine/anti-ship torpedoes |
M-256 was a Project 615 (also known by the NATO reporting name of "Quebec"-class) short-range attack diesel submarine of the Soviet Navy. She was commissioned into the Baltic Fleet.
Quebec-class submarines were fitted with two regular diesel engines and a third, closed-cycle diesel engine, which used liquid oxygen (LOX) to provide air-independent propulsion while the submarine was submerged. This system produced remarkable submerged speed and range, and greatly increased the hazard of a fire. Quebecs were referred to by their crews as "cigarette lighters."
On 26 September 1957, while operating in gale conditions in the Tallinn Gulf of the Baltic Sea, one of M-256’s diesel engines exploded. Fire immediately engulfed the diesel compartment, and soon spread to the next compartment. The boat surfaced and because of the likelihood of further explosions her crew evacuated onto her weather deck. None of the four ships keeping station nearby were able to take her under tow or evacuate her crew because of the gale conditions. About four hours after the beginning of the fire the boat suddenly lost longitudinal stability, took on a steep down-bubble, and sank. Of the 35 men on the boat's deck, only seven were rescued.