Heard joined the Royal Marines on 17 October 1933 at Deal. His Regimental Number was: Portsmouth/X1047. After recruit training and gunnery courses he was drafted to HMS Galatea, an Arethusa class light cruiser during its first commission, from 3 September 1935 to 4 June 1937. He was promoted to Corporal on the 9 September 1936. From 6 November 1937 to 5 September 1938 he served in HMS Cornwall, a County class heavy cruiser, and volunteered for flying training. On

10 October 1938 he was the first RM Non-Commissioned Officer to be transferred to the RN on probation as an Acting Leading Seaman and to commence pilot training on No: 1 Naval Pilots Course. The other Royal Marines on his course were; Lieutenants Harris and Marsh. His Elementary Flying Training took place at Rochester before graduating to No 1 FTS at Netheravon on 10 September 1938. He was awarded his wings on 22 April 1939 and promoted to Acting Petty Officer Airman; his FAA number being FX 97172.

Immediately Heard attended a fighter course flying Gladiators at RNAS Donibristle together with deck landing training on HMS Argus before joining 804 Squadron at RNAS Hatston on 4 December 1939. He served at Hatston for five months before also qualifying as a Swordfish seaplane pilot in May 1940. However, he was swiftly drafted to 800 Squadron in HMS Ark Royal from 29 May 1940 to 1 June 1941 flying Skuas. In July 1940 his squadron provided fighter patrols and escorts during an attack on the French Fleet at Oran; the same operation during which Peacock was shot down (see Peacock's section below). On 2 August Ark Royal took part in Operation HURRY providing cover when Arguslaunched twelve Hurricanes and two Skuas to reinforce the beleaguered Malta. As the Fleet turned back towards Gibraltar, fighters from Ark Royal, including Heard's, were in action against 'shadowers' from Sardinia and attacked Italian ships. Heard's squadron transferred to HMS Furious at Gibraltar in April 1941 and re-equipped with Fulmars. Nine of these aircraft formed 880X Flight for a six month spell in Malta, three embarked in Argus as 800Y Flight, and the remainder, 800Z Flight, transferred to Victorious to help search for the Bismarck. The squadron eventually regrouped at St Merryn in June 1941 having had quite a dispersed existence during Heard's time.

Heard then joined 881 Squadron in Illustrious until 19 March 1943. 881 Squadron formed at Lee-on-Solent on 1 June 1941 as a Fleet Fighter Squadron with Martlets. It embarked in Illustrious for the Indian Ocean in March 1942 and took part in operations over Madagascar and Diego Suarez (see Crozer's section above) returning in February 1943.

Heard followed his concentrated carrier experience with two instructional tours; the first at RNAS Yeovilton with 759 Squadron and the second at RNAS Henstridge with 764 Squadron from 26 January 1944 to 9 July 1945 during which he was promoted to Acting Warrant Flying Officer. He then attended an Air Combat Course at RNAS St Merryn before qualifying as a Flying Instructor at RAF Upavon. This was followed by a succession of appointments as a flying instructor with 799B and 727 Squadrons at RNAS Gosport, during which was confirmed in the rank of Warrant Flying Officer, and 766 Squadron at RNAS Lossiemouth. On completion of the latter tour Heard was promoted to Acting Lieutenant on 4 September 1948 and appointed to HMS Oakham Castle, a Castle class corvette, to gain his watchkeeping certificate. He was confirmed in the rank of Lieutenant on 9 February 1949.

In March 1949 Heard joined 800 Squadron, equipped with Seafires in HMS Triumph for service in the Mediterranean and the Far East. During an impressive operational squadron and instructional career he had flown Swordfish, Seafires, Skuas, Fulmars, Hurricanes, Martlets, Rocs, Gladiators, Harts, Fireflys and Harvards. Significantly, his final report from Triumphstated “[Heard is] ….the most experienced pilot in the Air Group with almost 2000 hours to his credit, he is a safe and entirely reliable pilot.” Therefore, it is tragic that on 24 January 1950 during a period when his squadron had disembarked to RNAS Sembawang, Singapore, that Heard's aircraft suffered an engine failure while he was returning from a rocket firing sortie in Malaya. He was killed attempting a 'wheels-up' landing at RAF Changi. The aircraft was observed to hit a palm tree just short of the runway, cartwheel and burst into flames.