The P-3 Orion maritime surveillance and ASW patrol
aircraft is based on the Electra turboprop airliner. Developed from
1958 to replace the P-2 Neptune the first P-3A entered service in
1962. The more powerful P-3B followed while the first P-3C entered
US Navy service in 1969. This model introduced a new APS-115 radar,
improved MAD and new data processing equipment. In 1975 an improved
navigation system, expanded computer memory, and tactical displays
were provided under the Update I program. In 1976 the Update II
program provided an infrared detection system and sonobuoy reference
system and the aircraft were fitted with the Harpoon missile. The
P-3C aircraft to the Upgrade III standard, delivered in 1984, were
equipped with advanced anti-submarine warfare avionics including
the IBM Proteus AN/UYS-1 acoustic processor. Australia took delivery
of Update II aircraft that were fitted with the British AQS-901
processing system and locally developed Barra sonobouys. Update
IV program improvements, mainly directed towards the provision of
advanced signal processing capabilities, were implemented during
the 1990s to meet the threat of new generation fast, quiet and deep
diving submarines. The aircraft are equipped with a Raytheon AN/APS-137(V)
multi-mission surveillance radar. Australia is currently upgrading
its aircraft to AP-3C standard a new Elta radar, MAD and processing
equipment.
Canada operates its own variant of the Orion family. The CP-140
Aurora utilises the P-3 airframe and the electronic systems of the
US Navy's S-3 Viking aircraft. The Vikings APS-116 search radar,
ASQ-501 MAD and AYK-10 processing computer are all used by this
aircraft. The Aurora also has an eleven person crew, one more than
standard Orion's. A total of 18 Auroras were delivered to Canadian
Forces as well as three C-140A Arcturus aircraft. The Arcturus is
a used for training and environmental and fisheries patrols. These
three aircraft carry only an APS-134 radar and no ASW gear.
P-3 aircraft have also been modified to fill the ELINT role. The
USN and Japan operate EP-3 with sensitive intelligence gathering
equipment. Two of Australia's Orion aircraft have reportedly been
modified to a standard similar to the USN EP-3 aircraft.