defences to deliver ordnance on the target. It featured variable geometry wings, an internal weapons bay and a cockpit with side-by-side seating. The cockpit formed part of an escape crew capsule. The F-111 had a three-point undercarriage arrangement with a two-wheel nose gear and two single-wheel main undercarriage. Most F-111 variants included a terrain-following radar system connected to the autopilot. The aircraft were powered by two Pratt & Whitney TF30 afterburning turbofan engines. The F-111's internal weapons bay could also carry bombs, a removable 20 mm M61 cannon, or auxiliary fuel tanks. The F-111C was equipped to carry the AN/AVQ-26 Pave Tack targeting system on a rotating carriage that kept the pod protected within the weapons bay when not in use. Pave Tack is a FLIR and laser rangefinder/designator that allowed the F-111 to designate targets and drop laser-guided bombs on them. RF-111Cs carried a pallet of sensors and cameras for reconnaissance use. F-111Cs were also equipped to launch the AGM-84 Harpoon anti-ship missile and the AGM-142 Popeye stand-off missile. Operational history Entry into service The Australian government ordered 24 F-111C aircraft to replace the RAAF's Canberras in the bombing and tactical strike role. While the first aircraft was officially handed over on 4 September 1968, structural issues delayed the entry into service of the F-111C. Twenty-four USAF F-4 Phantom IIs were leased as an interim measure. The Phantoms were delivered in September and October 1970 to No. 82 Wing at RAAF Base Amberley, Queensland. During its next three years in RAAF service, one F-4 was lost. By June 1973, the remaining 23 Phantoms were returned to the U.S. Like the F-111, the F-4 was a two-seat, multi-role, supersonic aircraft. Much more sophisticated than the Canberra, capable of air-to-air and air-to-ground attack roles; it had inertial navigation, a gun and radar. Experience with the F-4 likely contributed to the RAAF's success with the F-111. The RAAF proposed keeping the F-4 and using it with the F-111, but the government decided that the cost was too great. The F-111C entered Australian service after the technical problems were resolved, and the first F-111C was accepted at Nellis Air Force Base on 15 March 1973. On 31 March, the RAAF Washington Flying Unit was formed at McClellan Air Force Base in California with the mission of ferrying the first 12 F-111Cs to Australia. This unit was commanded by Group Captain John Newham, who