Two oil-fired boilers fed steam at 550 pounds per square inch (3,800 kPa) and 850 °F (454 °C) to a pair of double reduction geared steam turbines that in turn drove two propeller shafts, with the machinery rated at 30,000 shaft horsepower (22,000 kW), giving a speed of 28 knots (52 km/h; 32 mph).

[5] After commissioning and workup, Penelope joined the 20th Frigate Squadron which was based at Londonderry Port in Northern Ireland,[3] and from September–December 1964, formed part of a special squadron led by the cruiser Tiger that visited South American ports in an effort to improve relations and increase trade between Britain and South America.

[9] She took part in a variety of trials, including tests of different designs of propellers and was refitted in 1970 in preparation for trials of hull noise which involved having her propellers removed and being towed by sister ship Scylla at the end of a 1 mile (1.6 km) long cable.

[11][verification needed] All conspiracy theories have been refuted by the Ministry of Defence, while a 2002 report on the accident by an international study team noted that Penelope was 130 nautical miles (240 km; 150 mi) from the site of the accident, and was not fitted with surface to air missiles.

[citation needed] In 1971, she underwent another refit to allow her to carry out trials on the Sea Wolf missile.

All existing armament was removed, and an experimental tracking system and then a Sea Wolf launcher were mounted on the ship's flight deck.

4.5 inch shells fired from a ship several miles away would pass overhead and be targeted by Sea Wolf.

These trials continued until December 1977, when she started another refit at Devonport Dockyard to return her to an operational frigate and convert her to Batch 2 Exocet configuration.

On 13 June, Penelope's Lynx helicopter struck the already stranded Argentinian patrol boat Rio Iguazu with a Sea Skua missile.

Soon after, Penelope undertook a Falklands patrol in the tense aftermath of the war, and did not return home until June 1983.