Defence against terrorists from sea has assumed great importance and is rather the most challenging task of the maritime watch force. In such a hostile environment, the less costly OPVs may be the inescapable imperative for the future.
Sizes of OPVs : OPVs come in different sizes. These can be Large Patrol Craft (300-500 tonnes) as well as larger units comparable to Light Frigates (2000-3500 tonnes). The Corvette like dimensions (800-2000 tonnes) is the most typical case.
Characteristic Features of OPVS
From the foregoing it may be seen that there is no unique definition of an OPV. Generally speaking, they are, as their name suggests, vessels conceived for patrol duties in offshore waters. This implies, they are not combatant and they are mostly able to operate far from the coast and have long endurance. The OPVs are relatively inexpensive vessels, due to their features. Most of them are designed and built to merchant marine standards, which means a very significant saving both in procurement and operation,as they embody commercial standards for equipment, machinery and outfitting, in order to contain costs. When compared to similar size warships, the OPVs normally have longer endurance, good sea-keeping, lower top speed, small and simple payload and spacious accommodation.
The spacious accommodation is required for making long patrols more acceptable. It allows the carraige of a large variety of additional personnel according to the mission, i.e. environmental scientists; law enforcement officers; rescued mariners, pirates, terrorists; boarding parties; trainees, etc. The damage control and survivability characteristics are provided as per merchant marine standards as those for passenger ships, which is as good as naval ones in case of fire, flooding and lack of power etc, except, of course, that in case of direct hit or an underwater explosion by way of shock, blast, splinters the etc which are quite unlikely for this class of vessels. Some Navies include naval damage control standards in their OPV design. The main propulsion is generally by diesel engines and longer endurance at cruise speeds can be achieved and the top speeds of around 20 knots can be met.
The stealth features of OPVs are becoming part and parcel of their design. They will ensure better protection in the event of clashes as they provide lesser detection from enemys vessels or coastal radar stations are less susceptible to detection by enemy vessels and coastal radar station.
As an economy measure and in consonance with their peace time roles, OPVs are normally equipped with limited payload. This could be just one large caliber gun and a couple of small caliber guns, a surface search radar and a helicopter. The commercial type navigation radar provides low recognition probability as a naval vessel by the opponents ESM. CIWS by way of two gattling guns, optronic sensors and ESM could be other additions. The Optronic Sensor and ESM both provide passive surveillance. The Optronic Sensor can provide fire control capability at lower cost as compared to radar directors.
Passive surveillance, secure communications, discrete electronic emissions and stealth are equally important in this field of operation. In fact, besides the possible operations in selected scenarios against naval assets, in today’s world, criminal organizations can sometimes exploit ELINT to pose masquerade as a legitimate armed force.
The stealth features of OPVs are becoming part and parcel of their design. They will ensure better protection in the event of clashes as they provide lesser detection from enemy’s vessels or coastal radar stations are less susceptible to detection by enemy vessels and coastal radar station.
The combat data systems are now available based on commercial standards, thereby accruing significant savings . There will be force multiplier effect for area surveillance and therefore a valid support for reducing manpower. Both hardware and software can be selected from a variety of COTs products. The ships information system also facilitates navigation and mission planning for specific tasks, e.g interdiction patrol, fishery protection, pollution control , search & rescue .
The Irish OPVs , for example are issued with an information system featuring legal advice to the Captain, i.e. “Fishery legislation Expert System — FLES and a large data base of fishing vessels, i.e. “Fishing Protection Information System — FPIS. The latter is updated daily via HF or Sat-Com data-link with the shore command. FPIS contains all possible information on fishing vessels including permissions, criminal records, digital images, etc. To quote another case, the Italian Customs CI system features mission planning and two way secure link-voice, data, video — with the corps shore command, as well as a data base on suspected vessels, including digital images.
Helicopters have become an inescapable requirement for OPVs. Helicopters provide extended capabilities for surveillance and target classification, search & rescue and other tasks. The helicopter recovery and handling systems are now being provided on all major OPVs to ensure sustained helicopter operations in bad weather and high sea states.
UAVs are another possible add on to the OPVs. They require smaller decks and hangars. In future, UAVs may play an important role in maritime surveillance, carrying radar sensors and cameras.
RHIBs — Rigid Hull Inflatable Boats are also carried using stern ramps or hydraulic cranes for fast deployment and recovery. Their speed — 30 knots and above make them affordable and reliable solutions for delivering rescue, inspection and boarding parties.