The Avro 696 Shackleton, a long-range maritime patrol aircraft, was first flown (VW126) at Woodford on 9th March 1949, in the hands of Chief Test Pilot JH ‘Jimmy’ Orrell. It was designed in response to Air Ministry Specification R 5/46 by a team led initially by Lancaster designer Roy Chadwick. Tragically, Chadwick was killed in a crash in 1947, although the project continued. The type was developed as Britain's response to the growing threat of the Soviet Navy and its submarine fleet.
The prototype Avro 696 Shackleton G.R.1 (VW126) was later re-designated as a Marine Reconnaissance MR.1. It differed from the later production variants in so far as it featured gun turrets, and the capability for air-to-air refuelling. Initially produced as the Avro Type 696 Shackleton ASR3 for RAF Coastal Command, it was predominantly an evolution from the Avro 694 Lincoln, although it also drew on a number of Avro 688 Tudor assemblies.
The Avro 696 Shackleton MR.1 featured a chin-mounted search radar, as well as two 20mm cannon in the nose. Two more cannons were sited in a mid-upper dorsal turret, as well as two 0.5in machine guns in the tail. Engine power was provided by a pair of Rolls-Royce Griffon 57A engines (inboard) and a pair of Rolls-Royce Griffon 57 engines (outboard).
Upon entering RAF Service in 1951, its name, which up till that point had simply been the Type 696 or Lincoln ASR.3, was changed to Avro Shackleton, named after the polar explorer Sir Ernest Shackleton.
Production comprised three prototypes, followed by 29 Avro Shackleton MR.1 and 48 Avro 696 Shackleton MR.1A, the latter fitted with four Griffon 57A engines (and wider outboard nacelles). The aircraft showed significant improvements on previous Avro designs, most crucially with its increased patrol range of up to 3,000 nautical miles, as well as featuring the capacity to instal large amounts of newly-developed electronic surveillance equipment within its fuselage.
The Avro Shackleton MR.2 (WB833) first flew on 17th June 1952, and carried a number of improvements. These included a more streamlined nose, an improved radar installation and changing to a retractable ‘dustbin’ radome mounted under the fuselage aft of the bomb bay.
The nose and tail gun armaments were removed, although the mid-upper turret was initially retained (but subsequently deleted from all aircraft once in service). Twin retractable tail-wheels replaced the original single wheel fixed unit. 59 Avro Shackleton MR.2s were ordered, supplemented by 10 aircraft from the Avro 696 Shackleton MR.1 production line that were completed as Avro Shackleton MR.2s.
The final variant was the Avro 716 Shackleton MR.3, the first of which (WR970) flew on 2nd September 1955. The variant was another redesign in response to crew feedback, introducing a tricycle undercarriage with twin main wheels and a revised wing planform and wing-tip fuel tanks. The overall dimensions of the fuselage was increased, with new wings featuring improved ailerons and the capability for the use of tip tanks. The cockpit and crew sections were also fitted with better sound insulation, while those aircraft destined for 15-hour patrols were also equipped with a galley and sleeping accommodation. The twin nose-mounted 20mm cannon were also re-introduced on the variant, while the mid-upper turret was removed. Provision was also made for the under-wing carriage of rockets or sonobuoys. Normal power was provided by four Rolls-Royce Griffon 27A engines, driving contra-rotating propellers. However, in the case of the Avro 716 Shackleton MR.3 - Phase 3, a pair of 2,500 lbst Rolls-Royce Viper 203 turbojets were added, to improve take-off performance with one Viper installed at the rear of each outboard engine nacelle.
Production of the Avro 716 Shackleton MR.3 comprised 34 aircraft for the RAF and 8 for the South African Air Force – these latter being used to monitor Soviet vessels in the sea lanes around the Cape of Good Hope.
The long endurance of the Avro 696 Shackleton was demonstrated at the 1960 SBAC Show at Farnborough, where on each day of the show, an aircraft took off at the start of the flying display, to return a full twenty-four hours later.
When a gap in the UK Airborne Early Warning (AEW) capability emerged (due to problems with the proposed BAe Nimrod AEW and a delay before the Boeing E-3 Sentry could be introduced), the decision was taken to modify the Avro 696 Shackleton MR.2 to undertake the AEW role as an interim measure. Twelve Avro 696 Shackleton AEW.2 conversions were carried out at what by then were the Hawker Siddley Group sites of Woodford and Bitteswell, the first (WL745) flying on 30th September 1971. These aircraft retained the tailwheel configuration and carried an AN/APS-20 search radar (taken from redundant Fairey Gannet AEW3 aircraft), mounted in a distinctive radome, below the forward fuselage.
Like the Avro 652 Anson and the Avro 698 Vulcan, the Avro 696 Shackleton was destined to have an extremely long service life, with the last aircraft only retiring in 1991, forty-two years after the first flight of the prototype. A total of 181 Avro Shackleton aircraft were constructed over the lifetime of its production.