page_title: Avro Shackleton
section_title: Further development
hierarchical_section_title: Avro Shackleton / Development / Further development
caption_attribution_description: Avro 696 Shackleton MR.2 WG557 of 220 Squadron RAF at Blackbushe Airport in 1955
context_page_description: The Avro Shackleton is a British long-range maritime patrol aircraft which was used by the Royal Air Force and the South African Air Force. It was developed by Avro from the Avro Lincoln bomber, which itself had been a development of the famous wartime Avro Lancaster bomber.
  The Shackleton was developed during the late 1940s as part of Britain's military response to the rapid expansion of the Soviet Navy, in particular its submarine force. Produced as the primary type equipping RAF Coastal Command, the Type 696, as it was initially designated, incorporated major elements of the Lincoln, as well as the Avro Tudor passenger aircraft, and was furnished with extensive electronics suites in order to perform the anti-submarine warfare mission along with a much-improved crew environment to accommodate the long mission times involved in patrol work. Being known for a short time as the Lincoln ASR.3, it was decided that the Type 696 would be named Shackleton in service, after the polar explorer Sir Ernest Shackleton.
  It entered operational service with the RAF in April 1951.
context_section_description: The MR 2 was an improved version of the Shackleton, featuring numerous refinements that had been proposed for the MR1. The radar was upgraded to ASV Mk 13, and the radome relocated from the aircraft's nose to a ventral position aft of the bomb bay, the radome was retractable and could be fully extended only with the bomb bay doors open. It had improved allround radar coverage and minimised the risk of bird strikes. Both the nose and tail section were lengthened, the tailplane was redesigned, the undercarriage was strengthened and twin-retractable tailwheels were fitted. The Bristol dorsal turret was initially retained, but was later removed from all aircraft after delivery. The prototype, VW 126, was modified as an aerodynamic prototype at the end of 1950 and first flew with the MR 2 modification on 19 July 1951.
  VW 126 was tested at Boscombe Down in August 1951, particular attention being paid to changes made to improve its ground handling, such as the addition of toebrakes and a lockable rudder system. One production Mk 1 aircraft was modified on the line at Woodford with the Mk 2 changes and first flew on 17 June 1952. After trials were successful, it was decided to complete the last ten aircraft being built under the Mk 1 contract to MR 2 standard and further orders were placed for new aircraft. In order to keep pace with changing submarine threats, the Mk 2 force was progressively upgraded, with Phase I, II and III modifications introducing improved radar, weapons and other systems, as well as structural work to increase fatigue life. Production of the MR 2 ended in May 1954.
  The Type 716 Shackleton MR 3 was another redesign in response to crew feedback and observations. A new tricycle undercarriage was introduced, the fuselage was increased in all main dimensions and had new wings with better ailerons and tip tanks. The weapons capability was also upgraded to include homing torpedoes and Mk 101 Lulu nuclear depth bombs. To reduce crew fatigue on 15-hour flights, the sound deadening was improved and a proper galley and sleeping space were included. Due to these upgrades, the takeoff weight of the RAF's MR 3s had risen by over 30,000 lb (13,600 kg) (Ph. III) and assistance from Armstrong Siddeley Viper Mk 203 turbojets was needed on takeoff with a 5-minute limit. The Griffons had to be run at high power for very long periods after a heavyweight take-off so the Vipers were later cleared to run for four hours continuously so lower Griffon power settings could be used which reduced the risk of failures. The extra strain took a toll on the airframe, and flight life of the RAF MR 3s was so reduced that they were outlived by the MR 2s. Due to the arms embargo against South Africa, the SAAF's MR 3s never received these upgrades but were maintained independently by the SAAF.
  The Type 719 Shackleton IV, later known as the MR 4, was a projected variant intended to meet a Canadian requirement for a long-range patrol aircraft. The MR 4 would have been practically a new aircraft, sharing only the nose, cockpit, and outer wings with earlier variants; it would have also been powered by the Napier Nomad compound engine. The Shackleton IV was cancelled in 1955 and the Canadian requirement subsequently met by the Britannia Maritime Reconnaissance later to emerge as the Canadair Argus.
  In 1967, ten MR 2s were modified as training aircraft to replace the T 4 in-service with the Maritime Operational Training Unit; known as T 2s, the crew rest areas were replaced by additional radar equipment and the original radar fittings removed.
caption: Shackleton MR.2 of No. 220 Squadron RAF in September 1955
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