Delivered in 4 batches between 1966 and 1981, 9 of the remaining 12 airframes were upgraded to SH-3D (SAR) standard, while 3 were brought up to SH-3G (AEW) with the addition of the Searchwater radar in a retractable dustbin on the starboard side. By Autumn 2005, most of the anti-submarine fleet had completed a conversion to the transport / assault role with the removal of the ASW sensor/attack equipment and the addition of troop litters and an externally mounted cargo hook.