Avro 696 “Shackleton M.R.Mk.2”
British Four-engine Maritime Patrol Aircraft
Avro 696 Shackleton M.R.2 (WG531), Airplane card: 1953 “British Planes” Morning Foods Ltd., Mornflake Quick Cooking Oats, England, UK (The Skytamer Archive)
The Avro Shackleton was a British long-range maritime patrol aircraft for use by the Royal Air Force. It was developed by Avro from the Avro Lincoln bomber with a new fuselage. It was originally used primarily in the anti-submarine warfare (ASW) and maritime patrol aircraft (MPA) roles, and was later adapted for airborne early warning (AEW), search and rescue (SAR) and other roles from 1951 until 1990. It also served in the South African Air Force from 1957 to 1984. The type is named after the polar explorer Sir Ernest Shackleton.
Design and Development
The aircraft was designed by Roy Chadwick as the Avro Type 696. It was based on the Lincoln, itself a derivative of the successful wartime Lancaster heavy bomber, one of Chadwick's earlier designs which was the then current ASW aircraft. The design took the Lincoln's wings and landing gear and mated them with a new fuselage, and was initially referred to during development as the Lincoln ASR.3. The engines were Rolls-Royce Griffons with 13 ft (4 m) diameter contra-rotating propellers, creating a distinctive engine noise and adding high-tone deafness to the hazards of the pilots. The first test flight was in March 1949 and front-line aircraft were delivered to Coastal Command in April 1951 and had their operational debut during the Suez Crisis. In the ASW role, the Shackleton carried both types of sonobuoy, ESM, an Autolycus (diesel fume detection system) and for a short time an unreliable magnetic anomaly detector (MAD) system. Weapons were nine bombs, or three torpedoes or depth-charges, and 20 mm cannon.
The M.R.2 was improved with feedback from operations and is considered by aficionados to be the definitive type. The radome was moved from the nose to a ventral position, to improve all-round coverage and minimize the risk of bird-strikes. Both the nose and tail sections were lengthened, the tailplanes were redesigned and the undercarriage was strengthened.
The M.R.3 was another redesign in response to crew complaints. A new tricycle undercarriage was introduced, the fuselage was increased in all main dimensions and had new wings with better ailerons and tip tanks. As a sop to the crews, on fifteen hour flights the sound deadening was improved and a proper galley and sleeping space were included. Total take-off weight had risen by over 30,000 lb (13,600 kg) (Ph. III) and assistance from Armstrong Siddeley Viper Mk.203 turbojets was needed on take-off (JATO). This extra strain took a toll on the airframe, and flight life of the Mk.III's was sufficiently reduced that they were outlived by the Mk.IIs.
A total of 185 Shackletons were built from 1951 to 1958: around twelve are still believed to be intact, with one still flying (SAAF 1722 based at AFB Ysterplaat).
Royal Air Force
All marks suffered from using the Griffon engines - thirsty for fuel and oil, noisy and temperamental with high-maintenance needs. In 1961, M.R.2s engines needed top overhauls every 400 hours and went through a spate of ejecting spark plugs from their cylinder heads. It was not unusual to see an engine changed every day in a unit of six aircraft. They were constantly on the cusp of being replaced, but the potentially beneficial Napier Nomad re-engine did not happen.
The need to replace the Shackleton was first raised in the early 1960s. The arrival of the Hawker-Siddeley Nimrod in 1969 was the end for the Shackleton in most roles but it continued as the main SAR aircraft until 1972. The intention to retire the aircraft was then thwarted by the need for AEW coverage in the North Sea and northern Atlantic following the retirement of the Fairey Gannet. With a new design not due until the late 1970s the existing AN/APS-20 radar was installed in Mk.IIs as an interim measure, the A.E.W.2, from 1972. The Nimrod AEW replacement program dragged on and the eventual successor to the Shackleton did not arrive until the RAF finally abandoned the Nimrod AEW and purchased the Boeing E-3 Sentry in 1991.
South African Air Force
After evaluating four RAF M.R.2s in 1953, the South African Air Force ordered 8 aircraft to replace the Short Sunderland in maritime patrol duties. Some minor modifications were required for South African conditions and the resulting aircraft became the Mk.3 These Shackletons remained in maritime patrol service with 35 Squadron SAAF up to November 1984. The aircraft received SAAF designations 1716 to 1723. Although the joke has been applied to several aircraft, the Shackleton has been described as "a hundred thousand rivets flying in close formation."
Avro 696 Shackleton M.R.3 Specifications