821 Naval Air Squadron 821 Naval Air Squadron was a Royal Navy Fleet Air Arm carrier based squadron formed on 3 April 1933 with the transferral and amalgamation of the Fairey III aircraft from 446 and half of 455 Flight ( Fleet Spotter Reconnaissance ) Flights Royal Air Force to the newly formed Fleet Air Arm of the Royal Air Force . The squadron operated during the Second World War . History . Pre - war . The squadron was upgraded to use the Fairey Seal aircraft , and then embarked aboard with the Home Fleet in May 1933 . The Abyssinian crisis in August 1935 caused the squadron to be briefly transferred to the Mediterranean , but it returned to the UK in February 1936 . It then transferred its Seals to 822 Naval Air Squadron and received as replacements Blackburn Shark IIs , which it used to take up the role of Torpedo Spotter Reconnaissance . By September 1937 the Sharks had been replaced by Fairey Swordfish and the Squadron transferred to the new aircraft carrier in November 1938 . They sailed to the Mediterranean in spring 1939 , and as war loomed they were transferred to Admiralty control on 24 May 1939 . Second World War . Operating off " Ark Royal " the squadron was responsible for the first allied U - boat kill of the war , when they sank , after she had unsuccessfully tried to torpedo " Ark Royal " . The squadron sailed with the carrier to the South Atlantic and Indian Ocean , searching for German shipping and commerce raiders . After briefly operating in the Mediterranean , the German invasion of Norway in April 1940 caused " Ark Royal " to be recalled to support allied operations in Norway . The squadron was used to attack enemy positions , but on 21 June an attempt was made to sink the . The squadron sustained heavy losses in this unsuccessful operation and was forced to disband in December . A single flight , X Flight , continued in service though , with six aircraft . They sailed to Gibraltar aboard and then to Malta aboard HMS " Ark Royal " . They covered the Malta Convoys , before being absorbed in 815 Naval Air Squadron . 821 Squadron was re - formed at Detling in July 1941 , initially tasked with carrying out anti - submarine duties in Orkney . In November they were transferred to Egypt , and in March 1942 they were re - equipped with six Fairey Albacore s . They carried out bombing raids on Rhodes , and in Egypt were active in supporting ground forces at Maaten Bagush , Gambut and Daba . 821 Squadron was transferred again in November 1942 to operate out of RAF Hal Far , on Malta , attacking enemy supply convoys headed to North Africa . Four of the squadron ' s aircraft were transferred to Castel Benito , Tripoli in March 1943 to support night bombing raids by the Royal Air Force in Libya . In July 1943 at the time of Operation Husky , 821 squadron was based at Hal Far on Malta with Albacores for torpedo / spotter / reconnaissance . The entire squadron then transferred to Tunis in June to attack enemy shipping . 821 Squadron returned to the UK by October and was disbanded again . It reformed again in May 1944 , this time equipped with 12 Fairey Barracuda IIs and operating as a torpedo bomber reconnaissance squadron . The squadron was embarked aboard in November and sailed to the Far East . They carried out mine - laying operations in February 1945 , with Barracuda IIIs , and from April with six F4F Wildcat s until June 1945 . The squadron was active until February 1946 .