Complex sentence: MDMF evolved from the Aircraft Maintenance Group, where the Royal Navy's Sea Kings undertook a 2 yearly Scheduled Unit Maintenance (SUM) was phased out and Depth Maintenace of Merlin phased in between 2002 and 2003.
Split into simpler sentences: MDMF evolved from the Aircraft Maintenance Group, where the Royal Navy's Sea Kings undertook a 2 yearly Scheduled Unit Maintenance (SUM). This activity was phased out and Depth Maintenace of Merlin phased in between 2002 and 2003.