Fleet Maintenance Vessels were a type of repair ship used by navies in the Post Diaspora era.
The Royal Manticoran Navy operated these vessels to provide on the spot maintenance, repair, and upgrade to warships in need of those services beyond their shipboard capabilities but not requiring the services of a full shipyard.
In 1900 PD, HMS Fearless required the services of these vessels after the First Battle of Basilisk to repair battle damage before she could return to the Manticore System through the Manticore Wormhole Junction. (HH1)