In January 2021 satellite photos revealed that all three of Iran's Russian built Kilo class submarines were still out of the water, apparently undergoing repairs or refurbishment. Previous photos indicated the three subs had been out of the water since late 2020. It is not normal practice to have all of a warship class out of action at the same time. These three subs are not only out of action in a shipyard, but they are out of the water in a drydock situation. That means some serious work is being done, work that cannot wait. This usually means a common flaw with all the ships. Since no other Kilo users report or indicate a similar problem, this situation is unique. The major difference between Iranian Kilos and those of other export customers is that Iran refuses to send their Kilos back to Russia for major maintenance and insisted on doing it themselves. This is risky if you have no experience building similar subs or maintaining them with local parts rather than original parts from Russia. Iran is not commenting on their Kilo crisis.
These three diesel-electric subs are the most modern and effective warships Iran has, at least in deep water. The 2,300-ton Kilo needs a minimum water depth 35 meters (110 feet) to submerge and only a third of the waters in the Gulf are deep enough for that. Max operating depth for Kilos is 240 meters (790 feet). Once outside the outside the Persian Gulf, the Kilos can stay underwater and menace surface ships. The Kilos are very quiet while running on batteries, although the later models are quieter. The problem with the Iranian Kilos is that they are older models, dating from the early 1990s and a technically few years away from retirement age. After about three decades of active service most subs are either scrapped or undergo increasingly expensive refurbishments to keep them operational. Even then such elderly boats are either used just for training, usually while dockside plus a few trips to local waters for a practice dive or two.
Another problem is that Iran has been refurbishing its Kilos in Iran, and this is required every decade or so. This angered Russia, which insists refurbishment of its subs take place in Russia. Iran thought the cost was too high and that Russia might bow to Western pressure and not return the sub. Russia did not provide any technical assistance or components to the Iranians for those local refurbishments but may have changed the policy since 2014 when Russia declared the West a military threat to them.
Meanwhile Iran has been trying to build a replacement for the Kilos. This is apparently being done in stages. In early 2019 Iran announced it had built the first of a new type of submarine, the 527-ton Fateh. Iran claims this sub could remain submerged up to 200 meters (650 feet) for up to five weeks, apparently using a periscope length snorkel, a pipe type device to bring in air and expel diesel engine fumes. Fateh has four torpedo tubes, compared to six in the Kilo, and can launch locally built Hoveizeh cruise missiles from the torpedo tubes. These missiles have a range of 1,300 kilometers and are able to reach Israel. Hoveizeh was designed to be fired from a truck but Iran implies it has developed a version that can be expelled from a torpedo tube, reach the surface and get into the air. There is no evidence of that being tested yet and this may be another Iranian effort that is more aspirational than actual. Normally Fateh carries four torpedoes in the tubes plus two additional ones. Fateh can also carry eight naval mines in the torpedo tubes. A second Fateh is undergoing sea trials and a third is being built in a Caspian Sea ship yard for use only in the landlocked Caspian.
Iran has announced plans to build Kilo type subs but no such activity has been detected. For the last five years Iran has been working on the 1,200-ton Besat. Construction began in 2008 and is still underway. It is unclear when this sub will be completed. The Fateh may be an intermediate step in attempting a larger boat like Besat that is similar to the Kilo.
Iran has been talking about building mini-subs, mainly for use in the Persian Gulf, but is not currently doing so. Iran currently has about twenty locally built 115-ton Ghadir class subs with a crew of 18, two torpedo tubes and no reloads. The first of these entered service in 2005 and the latest in 2018. Ghadir’s get a lot of praise and publicity inside Iran but are rarely seen or detected at sea.
Iran had earlier purchased, between the late 1980s and early 1990s, nine 98-ton Nahang midget subs from North Korea. Nahang can carry two torpedoes in external tubes, or four naval mines. Only a few of the Nahangs are still in service and Iranian efforts to build a similar sub locally were not successful. Iran has found it easier to lay mines from small freighters, which are a common sight in the Gulf and along the Yemen coast and into the Red Sea.