Designed to attack submarines and surface ships, defend naval bases, seacoast and communications, as well as carry out reconnaissance and landing missions.

The submarine of Project 636 incorporates the most advanced engineering solutions, which have made it possible to reduce its noise to the noise level of natural marine environment. Blending into natural marine noise, the submarine is capable of detecting a target at a distance three to four times that at which it can be detected by adversary’s sonar systems. Consequently, it forestalls the enemy in carrying out a torpedo attack.

The submarine is equipped with a versatile information and battle management system, which incorporates a high-speed computer.

The submarine’s sonar system is capable of:

– operating in a circular scan mode and listening to the noise produced by submarines and surface ships;

– measuring distance to a target by an «echo» method in a sector of ±30° relative to the boat course;

– providing long-range and shortrange telephone/telegraph communication;

– detecting acoustic signals and determining their bearings.

The submarine is equipped with a mine-hunting unit, which operates in the active mode to detect mines and other small-size objects. The boat’s navigation equipment includes course indicators, speed and distance meter, automatic position plotter, echo sounder, receiverindicators of radio navigation systems, and radio direction finder.

The radar equipment includes passive and active radars.

The submarine’s main propulsion unit includes:

– two diesel generators, one shaft driven by the main propulsion motor, and an economic speed electric motor;

– a backup propulsion unit consisting of two reserve shafts and electric motors.

The main propulsion unit provides for:

– propulsion in the submerged or surfaced position by the main electric propulsion motor, as well as by the economic speed electric propulsion motor;

– charging of strage batteries; – snorkeling mode;

The backup propulsion unit can be operated both underwater and on the surface.

The submarine is equipped with two diesel generators, each comprising a diesel engine and an AC generator. Other submarine systems include: diving system, drain system, trim system, low/medium/high air pressure systems, emergency blowing system, marine and steering hydraulic system, fuel system, firefighting system, ventilation system, air-conditioning system, deck-drain and sewage-disposal system, etc. All vital systems are duplicated. Most of these systems operate autonomously. They are manipulated either from the main control room or from battle stations.

The submarine’s machinery and sys- tems are adapted for operation in any climatic conditions. The submarine of Project 636 has two hulls and elegant shape. It features a considerable reserve of buoyancy and unsinkability. The boat remains afloat if one of its compartments and two adjacent main ballast tanks on one side are flooded. Moreover, it continues to perform its mission under these circumstances to the possible extent.

Basic Characteristics

Displacement, m3	about 2,350
Principal dimensions, m	73.8 x 9.9 x 6.3
Speed, knots:
submerged	20
surfaced	11
Range, miles
at economic speed of 3 knots	400
snorkeling at a speed of 7 knots	7,500
Diving depth, m:
maximum	300
operating	250
periscopic	17.5
Endurance, days	45
Armament:	six 533mm torpedo tubes;
	12 torpedoes or 24 mines