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Avro Shackleton

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Shackleton
Role Maritime patrol aircraft
Manufacturer Avro
Designer Roy Chadwick, W.M. Taylor[1]
First flight 9 March 1949
Introduction April 1951
Retired 1990
Primary users Royal Air Force
South African Air Force
Produced 1951–1958
Number built 185
Developed from Avro Lincoln

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

Contra-rotating propellers

The aircraft was designed by Roy Chadwick as the Avro Type 696.[2] It was based on the Lincoln bomber and Tudor airliner, both derivatives of the successful wartime Lancaster heavy bomber, one of Chadwick's earlier designs which was the then current ASW aircraft.[3] The design took the Lincoln's centre wing and tail, Tudor outer wings and landing gear and a new wider and deeper fuselage, powered by four Rolls Royce Merlin engines. It was initially referred to during development as the Lincoln ASR.3.

The design was accepted with Air Ministry specification R.5/46 written around it. The tail as adopted differed from the Lincoln. The Merlin engines were replaced with the larger more powerful and slower-revving 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 Griffons were necessary because of the greater weight and drag over the Lincoln[4] and they provided equivalent power to the Merlins but at lower engine speed, which made for greater fuel efficiency for the long periods in the denser air at low altitudes that the Shackleton was intended for when hunting submarines – known as 'loitering' in RAF parlance – possibly several hours at around 500 feet or lower. This also made for less stress and wear, and hence reliability problems, for the engines; if Merlins had been used they would have been needed to run at comparatively high power settings for hours at a time once a submarine contact had been detected. Using conventional propellers would have needed an increase in propeller diameter to absorb the increased power and torque of the Griffons, which was not possible due to limitations in undercarriage length and engine nacelle positioning of the Lincoln wing, the contra-rotating propellers gave greater blade area within the same overall propeller diameter.

When the Shackleton was being designed the "Battle of the Atlantic" was still being fought and all possible submarine targets (German U-boats) were diesel-electric powered types and had very limited underwater endurance, the time underwater being limited by both the air available for the crew to breathe, and the battery power remaining to drive the submarine's underwater electric motors. While submerged it was incapable of travelling any great distance away from where it was detected. Then any aircraft could call up friendly Convoy Escort surface ships who would then deal with a submerged target in the normal way, with depth charges aimed using their own ASDIC sets. Hence for the Shackleton endurance in terms of the length of time it could spend in the air – as opposed to all-out range – was of prime importance. Once a submarine had been detected it might be necessary for the aircraft to remain over the last sighted position of the submarine all day (or night), preventing it from surfacing and making away at its higher surface speed. All the time the submarine was prevented from surfacing the crew's breathable air was being exhausted, and the batteries were consuming power, eventually the submarine would be forced to come up for air. It could then be attacked by the aircraft itself, again, this time using its own air-dropped depth charges.

In the case of a submarine recharging its batteries and replenishing its air while submerged using a snorkel, this could be detected by the aircraft using ASV radar, and the submarine attacked as-normal, with the added benefit that in visual conditions, location of the German snorkel mast made the submarine's underwater position obvious, aiding depth charge aiming.

The Avro design was ordered to Air Ministry specification R.5/46 as a replacement for the long range Liberator.

The first test flight of the prototype Shackleton GR.1, serial VW135, was on 9 March 1949 at the hands of Avro's Chief Test Pilot J.H. "Jimmy" Orrell.[5] In the ASW role, the Shackleton carried both types of sonobuoy, Electronic warfare support measures, 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 two 20 mm cannon in a Bristol dorsal turret. The GR.1 was later re-designated "Maritime Reconnaisance Mark I" – MR.1.

RAF Coastal Command Shackleton MR.1 of 269 Squadron in 1953

The MR.2 was an improved design incorporating feedback from operations and is considered by aficionados[citation needed] to be the definitive type. The radome was moved from the nose to a ventral position, to improve all-round coverage and minimise the risk of bird-strikes. Both the nose and tail sections were lengthened, the tailplanes were redesigned and the undercarriage was strengthened.

The Avro Type 716 Shackleton MR.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. Due to these upgrades the take-off 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 take-off (JATO).[6] This extra strain took a toll on the airframe, and flight life of the RAF MR.3s was sufficiently 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 Avro Type 719 Shackleton IV, later known as the MR.4, was a projected variant using the extremely fuel efficient Napier Nomad compound engine. The Shackleton IV was cancelled in 1955.

Operational history

A total of 185 Shackletons were built from 1951 to 1958: around 12 are still believed to be intact, with one still airworthy (SAAF 1722 based at AFB Ysterplaat)[7] but not flying due to a lack of qualified crew members.

Royal Air Force

8 Sqn RAF flew the Shackleton AEW.2 from 1973 to 1991

Front line MR.1 aircraft were delivered to Coastal Command in April 1951 with their operational debut during the Suez Crisis.

All marks suffered from using the Griffon engines — thirsty for fuel and oil, noisy and temperamental with high-maintenance needs. In 1961, MR.2's 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.

Shackletons were used in the Aden Protectorate during the Radfan Emergency against rebel tribesmen in Colonial Policing Operations. Leaflets would be dropped warning the tribes to vacate their properties which would then be bombed after they left.[8][9]

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 modified Shackleton MR.2s, redesignated AEW.2, as an interim measure from 1972. The development of the British Aerospace Nimrod AEW3 replacement dragged on and the eventual successor to the Shackleton did not arrive until the RAF finally abandoned the Nimrod AEW3 and purchased the Boeing E-3 Sentry in 1991.

South African Air Force

SAAF 1722, the last flying Shackleton.

After evaluating four RAF MR.2s in 1953, the South African Air Force ordered eight 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 MR.3.[10] These Shackletons remained in maritime patrol service with 35 Squadron SAAF up to November 1984.[7]

Although the joke has been applied to several aircraft, the Shackleton has been described as "a hundred thousand rivets flying in close formation."[11]

Variants

A Shackleton AEW.2 on display at the Museum of Science and Industry in Manchester
Shackleton GR.1
The first production model for the RAF, later redesignated Shackleton MR.1. Dorsal Bristol turret with two 20 mm cannon.
Shackleton MR.1A
Version powered by four Griffon 57A V12 piston engines, equipped with a chin mount radome; in service from April 1951.
Shackleton MR.2
Version with longer nose and radome moved to the ventral position. Look-out position in tail. Dorsal turret and two more 20 mm cannons in nose. Twin retractable tailwheels.
Shackleton MR.2C
Number of Shackleton MR.2s, fitted with the navigation and offensive equipment of the Shackleton MR.3.
Shackleton MR.3
Maritime reconnaissance, anti-shipping aircraft. The tail wheel was replaced by a tricycle undercarriage configuration. Fitted with wingtip tanks. Eight exported to South Africa. Cannon in nose only.
Shackleton MR.3 Phase 2
Similar to Shackleton MR.3 but fitted with two Viper turbojet engines for assisted takeoff.
Shackleton MR.4
Project of new maritime reconnaissance version using Napier Nomad engines, none built.
Shackleton AEW.2
Airborne early warning aircraft; MR.2s converted to take ex-Fairey Gannet airborne early warning radar.
Shackleton T.4
Navigation trainer conversion.

Operators

Retired Mk 3, SAAF 1721, on permanent display at Swartkop
 South Africa
 United Kingdom

Survivors

Flying

Static display

  • MR.2C WL795 on display at RAF St. Mawgan, England.
  • MR.2 WR963 In the care of the "Shackleton Preservation Trust", Live aircraft and capable of fast taxiing, Coventry Airport, England.
  • AEW.2 WR960 on display at the Museum of Science and Industry in Manchester, England.
  • MR.3 WR971 on display at the Fenland & West Norfolk Aviation Museum, Wisbech, England.
  • MR.3 WR974 on display at the Gatwick Aviation Museum, England; the engines on this aircraft can be run
  • MR.3 WR977 on display at the Newark Air Museum, England.
  • MR.3 WR982 on display at the Gatwick Aviation Museum, England.
  • MR.3 WR985 privately owned at Long Marston, England.
  • AEW.2 WL747 standing abandoned at the western end of runway 11/29 at Paphos Airport, Cyprus.
  • AEW.2 WL757 standing abandoned at the western end of runway 11/29 at Paphos Airport, Cyprus.
  • AEW.2 WL790 on display at the Pima Air & Space Museum, Tucson Arizona USA
  • SAAF 1716 ('Pelican 16') was restored to flight in 1994, but later that year, while on its way to the UK, it crash landed in the Sahara desert (22°37′50″N 13°14′15″W / 22.6305°N 13.2375°W / 22.6305; -13.2375 (SAAF Avro Shackleton 1716 Crash site)) after a double engine failure.[12] The crash did not result in any casualties, but the aircraft was abandoned in the desert.[13]
  • SAAF 1717 is on static display at the Transport museum in Stanger
  • SAAF 1720 is on static display at AFB Ysterplaat.
  • SAAF 1721 is on static display at the South African Air Force Museum in Swartkop.
  • SAAF 1723 is on static display at the Vic's Viking Garage, next to the N1 highway in Soweto, Johannesburg.
  • MR.3 XF700 abandoned and derelict, Nicosia, Cyprus
  • MR.3 XF708 on display at the Imperial War Museum, Duxford, England

Specifications

Orthographic projection of the Avro Shackleton MR Mk.1A, with profile views of all the other major variants.
Orthographic projection of the Avro Shackleton MR Mk.1A, with profile views of all the other major variants.
Armed with two 20 mm Hispano cannon in the nose

Data from [citation needed]

General characteristics

  • Crew: 10
  • Airfoil: modified NACA 23018 at root, NACA 23012 at wingtip [14]

Performance

  • Endurance: 14.6 hours

Armament

  • Guns: 2 × 20 mm Hispano Mark V cannon in the nose
  • Bombs: 10,000 lb (4,536 kg) of bombs, torpedoes, mines, or conventional or nuclear depth charges, such as the Mk 101 Lulu

See also

Related development

Aircraft of comparable role, configuration, and era

Related lists

References

Notes
  1. ^ Flight 1950 p612
  2. ^ Billings, Bill. "The Shackleton Story." The Shackleton Association. Retrieved: 10 July 2008.
  3. ^ Buttler, T British Secret Projects: Fighters and Bombers 1935–1950 2004. Midland Publishing p144,
  4. ^ Flight 18 May 1950 p162
  5. ^ Harlin and Jenks 1973, p. 164.
  6. ^ "Shackletons in the SAAF – Retirement." The Shackleton Project. Retrieved: 10 July 2008.
  7. ^ a b "Shackleton 1722 Video Launch." South African Air Force, 19 September 2007. Retrieved: 3 July 2008.
  8. ^ http://www.radfanhunters.co.uk/SandyM.htm
  9. ^ http://www.britains-smallwars.com/Radfan/raf.htm
  10. ^ "Shackletons in the SAAF – Birth of a Legend." The Shackleton project. Retrieved: 10 July 2008.
  11. ^ "Loose formation." century20war.co.uk. Retrieved: 18 August 2010.
  12. ^ "Pelican 16." South African Air Force Museum, 3 August 2008. Retrieved: 18 August 2010.
  13. ^ "Avro Shackleton 1716 forever missing-in-action." South African Air Force, 23 November 2006. Retrieved: 3 August 2008.
  14. ^ "Argosy Air| History| Development." argosyair.com. Retrieved: 18 August 2010.
Bibliography
  • Harlin, E.A. and G.A. Jenks. Avro: An Aircraft Album. Shepperton, Middlesex, UK: Ian Allen, 1973. ISBN 0-7710-0342-4.
  • Holmes, Harry. Avro: The History of an Aircraft Company. Wiltshire, UK: The Crowood Press, 2004. ISBN 1-86126-651-0.
  • Howard, Peter J. "Avro (Hawker Siddeley) Shackleton Mks. 1 to 4". Aircraft in Profile, Volume 13. Windsor, Berkshire, UK: Profile Publications Ltd., 1973, pp. 193–217. ISBN 0-85383-022-3.
  • Jackson, Aubrey J. Avro Aircraft since 1908. London: Putnam, 1965. ISBN 0-85177-797-X.
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