Alvand-class frigate

The Alvand class or Saam class  was originally a class of four frigates built for the Imperial Iranian Navy. They were renamed after the Iranian Revolution, and served in the Islamic Republic of Iran Navy during Iran-Iraq War. Three still remain in service. A fourth was sunk by the U.S. Navy in 1988.

Development and construction
The ships were built in the United Kingdom by Vosper Ltd and based on their Mark 5 design with the following arms & equipment:


 * ASuW - 1 × quintuple Sea Killer Mk2 surface-to-surface missile
 * AAW - 1 × triple Sea Cat surface-to-air missile launcher
 * ASW - 1 × 3 barrelled Anti Submarine Mortar Mark 10 Limbo launcher
 * Guns - 1 × Mark 8 Mod 0 4.5 inch general purpose & 1 × twin 35mm Oerlikon AA
 * Electronics - Plessey AWS 1 air surveillance radar with on-mounted IFF; 2 × Contraves Seahunter systems (For use with Sea cat, Sea Killer & the 35mm mount); Decca RDL 1 passive direction finding equipment

They were refitted in the UK shortly before the 1979 Iranian Revolution.

History
The ships were originally named after characters from Ferdowsi's Shahnameh. After the Islamic Revolution they were renamed after mountains in Iran.

They saw action during the "Tanker War" phase of the Iran–Iraq War and proved effective against Iraqi forces. After one was sunk, and other significant losses taken, during Operation Praying Mantis they saw little further use as the Iranian Navy proved no match for the U.S. Navy.

Upgrades
The Sea Killer missiles were replaced by Chinese made C-802s in the 1990s. The Sea Cats were replaced by the addition of a 20 mm AA gun.

Two triple 12.75 in torpedo tubes, two 81 mm mortars and two 0.50 caliber machine guns were also fitted.

Successors
The Moudge-class frigate is a modified Iranian-built version of the Alvand class, with five either in service or under construction.