Phase three is broken into two separate parts, phase 3.1 of the HUG project will see the fleet undergo a structural refurbishment program with a number of aircraft undergoing the replacement of centre barrels and adjacent structural components. In addition, phase 3.2 started with an Aging Aircraft Audit (AAA), ongoing R3 Deeper Maintenance (DM) and minor projects such as Night Vision Capability (NVC) will also be undertaken to ensure that the fleet can continue to perform its air defence tasks through to the Planned Withdrawal Date.