Avro Shackleton

https://en.wikipedia.org/wiki/Avro_Shackleton

The Avro Shackleton is a British long-range maritime patrol aircraft (MPA) used
by the Royal Air Force (RAF) and the South African Air Force (SAAF). 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 (ASW) 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.

In April 1951, it entered operational service with the RAF. The Shackleton was
used primarily in the anti-submarine warfare (ASW) and maritime patrol aircraft
(MPA) roles; it was also frequently deployed as an aerial search and rescue
(SAR) platform and for performing several other secondary roles such as mail
delivery and as a crude troop-transport aircraft. In addition to its service
with the RAF, South Africa also elected to procure the Shackleton to equip the
SAAF. In South African service, the type was operated in the maritime patrol
capacity between 1957 and 1984. During March 1971, a number of SAAF Shackletons
were used during the SS Wafra oil spill, intentionally sinking the stricken oil
tanker using depth charges to prevent further ecological contamination.

During the 1970s, the Shackleton was replaced in the maritime patrol role by the
jet-powered Hawker Siddeley Nimrod. During its later life, a small number of the
RAF's existing Shackletons received extensive modifications in order to adapt
them to perform the airborne early warning (AEW) role. The type continued to be
used in this support capacity until 1991, when it was replaced by the Boeing E-3
Sentry AEW aircraft. These were the last examples of the type remaining in
active service.

The Type 696 was a significant development upon the Lincoln. Elements of the
Avro Tudor airliner were also reused in the design; Lincoln and Tudor had been
derivatives of the successful wartime Avro Lancaster bomber. Crucially, the new
aircraft was to be capable of a 3,000 nautical mile range while carrying up to
6,000 lb of weapons and equipment. In addition to featuring a large amount of
electronic equipment, the Type 696 had a much improved crew environment over
other aircraft types to allow them to be more effective during the lengthy
mission times anticipated. During development the Type 696 was provisionally
referred to as the Lincoln ASR.3 before the officially allocated name
'Shackleton' was selected.

The first test flight of the prototype Shackleton GR.1, serial VW135, was made
on 9 March 1949 from the manufacturer's airfield at Woodford, Cheshire in the
hands of Avro's Chief Test Pilot J.H. "Jimmy" Orrell. The GR.1 was later
redesignated "Maritime Reconnaissance Mark I" (MR 1). The prototype differed
from subsequent production Shackletons in a number of areas; it featured a
number of turrets and was equipped for air-to-air refuelling using the
looped-line method. These did not feature on production aircraft due to
judgments of ineffectiveness or performance difficulties incurred. However, the
performance of the prototype had been such that, in addition to the go-ahead for
the MR1's production, a specification for improved variant was issued in
December 1949, before the first production Shackleton had even flown. By 1951,
the MR1 had become officially considered as an interim type due to several
shortcomings.

The Shackleton was a purpose-built aircraft for the maritime patrol role;
however, the legacy of Avro's preceding aircraft is present in many aspects of
the overall design. The centre section of the Shackleton's wing originates from
the Lincoln, while the outer wing and undercarriage were sourced from the Tudor
outer wings; at one stage during development, the tailplane had closely
resembled the Lincoln's, but was enlarged and changed soon after. An entirely
new fuselage was adopted, being wider and deeper to provide a large space in
which to accommodate the crew, their equipment, and a large bomb bay. Later
variants of the Shackleton were substantially redesigned, adopting a new
nosewheel undercarriage, redesigned wings and centre-section, and a larger fuel
capacity for more range.

Various armaments and equipment were carried by the Shackleton in order to
perform its missions. In ASW operations, the ASV Mk 13 radar was the primary
detection tool; it could detect a destroyer at a range of 40 nautical miles, a
surfaced submarine at 20 nautical miles, and a submarine's conning tower at
eight nautical miles, although rough seas considerably reduced the radar's
effectiveness. Other equipment included droppable sonobuoys, electronic warfare
support measures and an Autolycus diesel fume detection system. A special camera
bay housed several reconnaissance cameras capable of medium altitude and
nighttime vertical photography, and low-altitude oblique photography. The crew
would also perform visual searches using various lookout positions that were
provided for this purpose. Weapons carried included up to nine bombs, three
homing torpedoes or depth-charges; the aircraft also had two 20 mm cannon in a
Bristol dorsal turret. An in-flight refueling receptacle could be accommodated,
but was not fitted on production aircraft.


Role
Maritime patrol aircraft

Manufacturer
Avro

First flight
9 March 1949

Introduction
April 1951

Retired
1991

Primary users
Royal Air Force
South African Air Force

Produced
1951–1958

Number built
185

Developed from
Avro Lincoln

On 30 March 1951, the first Shackleton was delivered to No. 120 Squadron RAF; by
the end of 1952 seven squadrons were operating the type. The first operational
deployment of the Shackleton occurred in 1955 as a troop-transport for British
Army movements to Cyprus; less than a year later, the type's first combat
deployment took place during the Suez Crisis, codenamed Operation Musketeer.

In 1957, British RAF Shackletons participated heavily during Jebel Akhdar War in
Oman to expand the territory of the Sultanate, which was a de facto British
colony, in order to gain access to oil wells in the interior parts of Oman. The
RAF made 1,635 raids, dropping 1,094 tons and firing 900 rockets at the interior
of Oman between July and December 1958 targeting insurgents, mountain top
villages, water channels and crops in a war that remained under low profile.

During the 1960s, the typical Shackleton crew comprised two pilots, two
navigators, a flight engineer, an air electronics officer, and four air
electronics operators. During this period, equipment upgrades had become routine
in order to keep pace with ever more capable submarines; problems with airframe
fatigue were identified, leading to several programmes being carried out to
strengthen the aircraft and thus extend its viable service life. In 1966,
nuclear depth charges were introduced to the Shackleton's arsenal with the aim
of countering the Soviets' development of deep-diving submarines.

Maritime reconnaissance was a large element of the Shackleton's service. This
mission was often performed to identify and monitor naval and merchant shipping
and to demonstrate sovereignty. During the Indonesia–Malaysia confrontation in
the 1960s, Shackletons monitored the seas for vessels involved in arms
smuggling. Similar operations were conducted in Cyprus, and Shackletons
operating from bases in Madagascar cooperated with Royal Navy vessels to enforce
a United Nation-mandated oil blockade of Rhodesia.

The Shackleton would often be used to perform search and rescue missions, at all
times one crew being kept on standby somewhere across the UK for this role. The
Shackleton had also replaced the Avro Lincoln in the colonial policing mission,
aircraft often being stationed in the Aden Protectorate and Oman to carry out
various support missions, including convoy escorting, supply dropping, photo
reconnaissance, communication relaying, and ground-attack missions; the
Shackleton was also employed in several short-term bombing operations. Other
roles included weather reconnaissance and transport duties, in the latter role
each Shackleton could carry freight panniers in the bomb bay or up to 16 fully
equipped soldiers.

In 1969, a jet-powered replacement patrol aircraft, the Hawker Siddeley Nimrod,
began to enter RAF service, which was to spell the end for the Shackleton in
most roles. While radically differing in external appearance, the Shackleton and
the initial version of the Nimrod shared many sensor systems and onboard
equipment.

The intention to retire the Shackleton was thwarted by the need to provide AEW
coverage in the North Sea and northern Atlantic following the withdrawal of the
Fleet Air Arm's Fairey Gannet aircraft used in the AEW role in the 1970s. As an
interim replacement, the existing AN/APS-20 radar was installed in modified
Shackleton MR 2s, redesignated the AEW 2, as an interim measure from 1972. These
were operated by No. 8 Sqn, based at RAF Lossiemouth. All 12 AEW aircraft were
given names from The Magic Roundabout and The Herbs TV series. The intended
replacement, the British Aerospace Nimrod AEW3, suffered considerable
development difficulties which culminated in the Nimrod AEW 3 being cancelled in
favour of an off-the-shelf purchase of the Boeing E-3 Sentry, which allowed the
last Shackletons to be retired in 1991.

Specifications

General characteristics
Crew: ten
Length: 87 ft 4 in (26.61 m)
Wingspan: 120 ft (36.58 m)
Height: 17 ft 6 in (5.33 m)
Wing area: 1,421 ft² (132 m²)
Airfoil: modified NACA 23018 at root, NACA 23012 at wingtip
Empty weight: 51,400 lb (23,300 kg)
Max. takeoff weight: 86,000 lb (39,000 kg
Fuel capacity: 4,258 imperial gallons (19,360 L)
Powerplant: four × Rolls-Royce Griffon 57 liquid-cooled V12 engine, 1,960 hp
(1,460 kW) each
Propellers: contra-rotating propeller, two per engine Propeller diameter: 13 ft
(4 m)


Performance
Maximum speed: 260 kn (300 mph, 480 km/h)
Range: 1,950 nmi (2,250 mi, 3,620 km)
Endurance: 14.6 hours
Service ceiling: 20,200 ft (6,200 m)
Max. wing loading: 61 lb/ft² (300 kg/m²)
Minimum power/mass: 91 hp/lb (150 W/kg))

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




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