Avro Shackleton

As the Second World War entered its final months Royal Air Force's Coastal Command arm was looking to the future and the need to replace its myriad of aircraft. This was for a number of different reasons. Boeing's B-17 Flying Fortress and Consolidated's B-24 Liberator were being used under lend-lease which meant that the aircraft had to be either returned or scrapped and its flying boats were being rendered obsolete, not to mention the cost of maintaining a number of different types. As a stop gap a number of Avro Lancasters were converted to GR. Mk IIIs.

At the same time as Coastal Command was reviewing its fleet the Avro Lincoln entered service and the Avro design team had been working on a anti-submarine version known as the ASR 3. This would never leave the drawing board stage though. The Air Ministry were interested in this aircraft however and issued Specification R5/46 for a similar aircraft from Avro. Originally designated the Type 696 it was able to accommodate a crew of ten which consisted of two pilots, two navigators, four air electronics operators, air electronics officer and a flight engineer. Power for the six bladed contra-rotating propellers would be supplied by four Rolls-Royce Griffon engines. The design of the aircraft was still influenced by the Lincoln with the wings, fuselage and tail plane unit all carried over with the Avro Tudor's outer wing sections and undercarriage being used as well. Happy with the design on the 28th May 1947 three prototypes were ordered.

Development of the design continued with crew comfort considered a must, a wider and deeper fuselage was designed and along with other changes led to the aircraft being re-named the Shackleton. The first of the three prototypes, designated GR.1 (General Reconnaissance) flew from Woodford on the 9th March 1949 with Jimmy Orrell, the chief test pilot at Avro, at the controls. This was followed six months later by the second prototype on the 2nd September with the third prototype flying on the 29th March 1950. In between this the aircraft was re-designated MR.1 (Marine Reconnaissance) with December 1949 seeing the Air Ministry issuing a specification for an improved Shackleton.

The first of the new aircraft would be known as the MR. Mk 1, powered by two 2,450-hp Rolls-Royce Griffon 57s outer engines and two Griffon 57As inner engines enabling a top speed of 300 mph, a range of 3,800 miles and a service ceiling of 25,700 ft. Armament for the aircraft consisted of four 20mm cannons, two either side of the nose and two in a mid-upper turret with the tail turret housing a pair of Browning 0.5-in machine-guns. Also onboard ASV (Air-to-Surface Vessel) radar and a 'looped line', for in-flight refuelling, was installed. The first production version flew on the 24th October 1950. Five months later in March 1951 the Shackleton would enter service when No. 120 Squadron, RAF Kinloss received the first examples.

The MR. Mk 2 was to follow and had a number of improvements and changes to it. First, all four engines would be powered by the 2,450-hp Griffon 57A. The ASV radar was improved and moved to under the fuselage, providing 360 degree coverage. With the removal of the radar from the nose this underwent a re-design and was lengthened to enable a bomb-aimer to be stationed there and the two cannons either side of the nose were moved to the front as a pair. The rear of the Shackleton would also undergo changes as the tail guns were removed and the rear extended for an observer. A pair of retractable tail wheels were also added. These re-designs would add an extra 10 feet to the length of the aircraft.

Testing of the aircraft took place during 1951 at Boscombe Down with a modified MR. Mk 1. This was followed the following year on the 17th June when the first true MR. Mk 2 flew. These would begin to enter service during January 1953. Development of the MR. Mk 2 continued with improvements to the aircraft meaning they would be known as either the Shackleton MR. Mk 2 Phase 1, Phase 2 or Phase 3.

Improvements to the Shackleton continued and the MR. Mk 3 would benefit from crews experience of using the type during operational missions. There were a couple of major changes implemented, first the wings would be replaced and the new wings saw tip tanks added to further increase the range of the aircraft. Secondly, revisions were also made to the undercarriage so it became a tricycle arrangement. With the aircraft now heaver than before, top speed was 253mph some 47mph down on its predecessor, a pair of 2,500lb Bristol Siddeley Viper 203 auxiliary turbojets were added to the out board engines to aid take-offs. As with the MR. Mk 2 further improvements saw the aircraft known as either Phase 1, 2 or 3.

As the 1960s drew to a close it looked like the Shackleton's career was coming to an end with the introduction of the jet powered Hawker Siddeley Nimrod which began to replace the type. However the retirement of another aircraft, the Fairey Gannet AEW 3, saw a need arise for an aircraft to perform the AEW (Airborne Early Warning) role. This would lead to the Shackleton AEW Mk 2 which was fitted with the Gannets AN.APS 20(f) radar and ventral radome and this made its maiden flight from Woodford on the 30th September 1971. Instead of building new aircraft twelve MR. Mk 2s would be converted for the AEW role with all the aircraft serving with No. 8 Squadron, Kinloss.

During its 40 years in service the Avro Shackleton's main role was undertaking maritime reconnaissance. This required identifying and tracking naval and merchant shipping. Some of the other duties included search and rescue, troop transport and some were converted to T.2 and T.4 trainer versions. The bomb load carried by the aircraft varied and could consist of a mixture of 10,000lb bombs, torpedoes, mines, depth charges and from 1966 onwards nuclear depth charges.

In total 181 aircraft were built and the only other airforce to use the type was the South African.