Haijiu-class submarine chaser

Class overview
Operators:	People's Liberation Army Navy
Preceded by:	Type 037 (Hainan-class)
Succeeded by:	Type 037I (Haiqing-class)
Completed:	4
General characteristics
Type:	Submarine chaser
Displacement:	490 long tons (500 t)
Length:	64 m (210 ft 0 in)
Beam:	7.2 m (23 ft 7 in)
Draft:	2.2 m (7 ft 3 in)
Propulsion:	4 × diesel engines, 8,800 hp (6,562 kW) 4 × shafts
Speed:	28 knots (52 km/h; 32 mph)
Range:	750 nmi (1,390 km) at 18 knots (33 km/h; 21 mph)
Complement:	72
Sensors and processing systems:	I-band Pot Head surface search radar I-band Round Ball fire control radar Chinese copy of Thomson-Sintra medium frequency SS-12 VDS sonar
Armament:	4 × Chinese Type 66 57 mm (2.2 in) guns (2 × 2) 2 × AK-230 30 mm (1.2 in) AA guns 4 × RBU-1200 ASW mortars 2 × depth charge rails with 18 depth charges

The Haijiu class submarine chasers are two (possibly four) modified versions of the Hainan class submarine chasers (Type 037) of the People's Liberation Army Navy.

The main difference is that four ASW rocket launchers have replaced the original two ASW mortars. The biggest improvement, however, it's in the sonar system. Original SJD-3 sonar on earlier Type 037 class submarine chaser is replaced by a 13 kHz (2 frequency ranges) French Thomson Sintra SS-12/DIP 12 hull mounted (HM)/variable depth sonar (VDS). DIP 12, the VDS version weigh 4 tons and has a 200-meter cable with towing speed of 16 kts, and the range is selectable at 2, 4, 8 and 16 km respectively. However, during deployment, it was discovered that the endurance of this class is limited and the capabilities of SS/DIP 12 sonar system could not be fully exploited. There is some disagreement over the type designation of this class, some sources claim it is Type 037I, while others claim it is Type 037 Mod (for modified or modernized).