The Flyvefisken-class patrol vessels ("Flying fish" in Danish) are warships of the Royal Danish Navy. The class is also known as the Standard Flex 300 or SF300 class. The five vessels sold to the Portuguese Navy are locally referred as Tejo class.
The Flyvefisken ships were constructed using an innovative modular design known as StanFlex: they have a standard hull in which containerised weapons or systems can be placed. This allows them to rapidly change roles, typically in 48 hours. The containers measure . One container is situated on the foredeck; the other three go on the quarterdeck behind the superstructure and funnel. Possible configurations include:
The structure of the ships is built using a sandwich material, consisting of a layer of fiberglass either side of a core of PVC cell foam. This building method helps reduce maintenance costs, and is used to this day on the new Diana and -Holm class ships.
The Flyvefisken class replaced three different vessels in the Danish Navy: Six torpedo boats of the Søløven class (1965âÂÂ1990), six coastal minesweepers of the Sund class (1955âÂÂ1999) and eight seaward defence craft of the Daphne class (1961âÂÂ1991). It was possible because of the containerised systems and modern technology.
The Søløven boats were light plywood boats propelled by three turboshafts, which attacked the enemy ships with torpedoes in hit-and-run attacks. The Flyvefisken class is not as fast itself, but compensates for this by using longer-ranged and faster Harpoon missiles as its anti-ship weapon of choice.
The Sund-class minesweepers were built of wood, bronze and other non-magnetic materials. They swept mine fields by trawling through the area with paravanes on tow separating magnetic and acoustic generators for the bottom mines, and chain cutters for the horned mines. The Flyvefisken class instead locates the mines with side-scan sonar and neutralizes them one by one with a ROV, improving safety of the ship and crew.
The Daphne class attacked submarines by dropping depth charges while passing over the submarine. The Flyvefisken class uses MU90 homing torpedoes instead, allowing for standoff attacks.
Four vessels of the class (Glenten, Ravnen, Skaden and Viben) were acquired by the Portuguese Navy in 2010 and re-named Mondego, Douro, Guadiana and Tejo. A fifth vessel, Gribben, was also acquired by the service as a spare parts hull. After a period of upgrade and reconfiguration, Mondego and Tejo were specifically tasked to police Portugal's exclusive economic zone around Madeira.
In 2023, 13 sailors assigned to Mondego were relieved of their duties when they refused to board the ship claiming her to be unseaworthy. The navy rejected the claim, which was made after the vessel had been tasked to monitor a Russian ship sailing in the vicinity of Madeira.
A total of 14 ships were built in the class, in three series:
The difference between the series is mainly in the configuration of the propulsion system. Series 2 is not equipped with hydraulic propulsion, but instead has an additional auxiliary engine, and Series 3 has one further auxiliary engine.