In July 1831, aged just 12 years old, he joined HMS Samarang at Portsmouth, as a Gentleman Volunteer. The Captain was Capt. Charles Paget (who would later marry one of his sisters, Emily Caroline) and the Lieutenant was a relation, William McClintock-Bunbury, whose son Thomas later became 2nd Lord Rathdonnell . In 1843 he passed his examination for lieutenancy and joined the steamship "Gorgon", which was driven ashore at
Montevideo and salvaged, a feat of seamanship on the part of her captain and officers that attracted much attention. Hitherto, until 1847, McClintock's service was almost wholly on the American coasts. 's 1850–1851 search for Franklin's expedition McClintock joined a series of searches for Sir
John Franklin between 1848 and 1859. He mastered travel through the
manhauling of sledges, which remained the standard practice when it came to overland travel in icy territory in the Royal Navy, until the death of
Robert Falcon Scott in his bid to reach the
South Pole in 1912. 's 1852–1854 search for Franklin's expedition In 1848, McClintock accompanied
James Clark Ross on his survey of
Somerset Island. As part of Captain
Henry Kellett's expedition from 1852 to 1854, McClintock travelled by sled and discovered of previously unknown coastline.
Fate of Franklin's expedition File:Francis Leopold McClintock's sledge flag (1857–1859).svg|thumb|Flag flown by McClintock on his sledge
Lady Franklin during his own 1857–1859 search for Franklin's expedition ==Later life==