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HMS Unicorn (I72)
Encyclopedia
HMS Unicorn was a aircraft repair ship and light aircraft carrier
built for the Royal Navy
in the late 1930s. She was completed during World War II
and provided air cover over the amphibious landing at Salerno, Italy in September 1943. The ship was transferred to the Eastern Fleet in the Indian Ocean
at the end of the year. Unicorn supported the aircraft carriers of the fleet on their operations until the British Pacific Fleet
(BPF) was formed in November 1944. She was transferred to Australia in early 1945 to support the BPF's operations during Operation Iceberg, the Allied invasion of Okinawa in May. To shorten the time required to replenish the BPF's carriers, the ship was based in the Admiralty Islands
and in the Philippine Islands until the Japanese surrender in August. Unicorn was decommissioned and placed in reserve
when she returned to the UK in January 1946.
The ship was recommissioned in 1949 to support the light carrier of the Far East Fleet, as the Eastern Fleet had been redesignated after the end of World War II. She was unloading aircraft and equipment in Singapore
in June 1950 when the Korean War
began. She spent most of the war ferrying aircraft, troops, stores and equipment in support of Commonwealth
operations in Korea. Unicorn supported other carriers during operations in Korea, but she became the only aircraft carrier to conduct a shore bombardment with her guns during wartime when she attacked North Korean observers on the coast during the war. The ship returned to the UK after the end of the war and was again placed in reserve. She was listed for disposal in 1958 and sold for scrap
in 1959.
of 1934–35 demonstrated to the Admiralty
that it needed a depot ship
to support the aircraft carriers in active service, just like submarine
and destroyer tender
s supported those types. Such a ship would be able to perform a wider range of aircraft repair and maintenance tasks than aircraft carriers and on the full range of aircraft operated by the Royal Navy, including amphibian
s. Admiral Reginald Henderson
, Controller of the Navy was instrumental for gaining approval for the ship and ensuring that she had a complete flight deck that would allow her to land, service and launch aircraft on active operations. She was was the first ship built in any navy that could "carry out the full range of aircraft maintenance and repair work in addition to the ability to operate aircraft from the flight deck". In practice, Unicorn proved the value of the concept and two similar support ships, and were converted into aircraft maintenance ships by modifying light aircraft carriers still under construction.
Unicorn had an overall length of 640 feet (195.1 m), a beam of 90 in 3 in (27.51 m), and a draught of 23 feet (7 m) at deep load. She was somewhat overweight as completed and displaced 16510 LT at standard load rather than her designed 14750 LT. Each of the ship's two sets of Parsons
geared steam turbine
s drove one 15 feet (4.6 m) propeller. Steam was supplied by six Admiralty three-drum water-tube boiler
s operating at a pressure of 400 pound per square inch. The turbines were designed for a total of 40000 shp and gave Unicorn a speed of 24 knots (13.1 m/s). The ship carried 3000 LT of fuel oil
which gave her a range of 7000 nautical miles (12,964 km) at 13.5 knots (7.3 m/s).
In order to land aircraft aboard, Unicorn was therefore designed with a full-length, 600 feet (182.9 m)-long flight deck
with arresting gear
. She was also fitted with a catapult
capable of launching a 14000 pounds (6,350.3 kg) aircraft to a speed of 66 knots (35.9 m/s). The ship had two hangar
s, each 16 in 6 in (5.03 m) high. Aircraft were transported between the hangars and the flight deck by two aircraft lifts (elevators); the forward lift measured 33 by 45 ft (10.1 by 13.7 m) and the rear one 24 by 46 ft (7.3 by 14 m). Unicorn could carry about 33 operational aircraft. Bulk petrol storage consisted of 36500 imp gal (165,932.3 l; 43,834.7 US gal). During wartime, the ship's crew totaled 1200. The ship carried a self-propelled lighter
under the rear of the flight deck to allow unflyable aircraft to be transferred between ships or to shore facilities. This lighter was lowered flush with the upper hangar deck so that an aircraft could be rolled onto to it or an aircraft could be lifted onto it once the lighter was in the water.
Unicorn was armed with four twin mounts for the 45-calibre QF 4-inch Mk XVI
dual purpose gun
. This mounting could elevate from −10 to +80°. The Mk XVI gun fired about 12 35 pounds (15.9 kg) high-explosive shells per minute at a muzzle velocity of 2660 ft/s (810.8 m/s). Against surface targets it had a range of 19850 yards (18,150.8 m) and a maximum ceiling of 39000 ft (11,887.2 m), but an effective anti-aircraft range of much less. She was also equipped with four quadruple mounts for the 40 millimetres (1.6 in) QF 2-pounder Mk VIII gun
("pom-pom"). These gun mounts could depress to −10° and elevate to a maximum of +80°. The Mk VIII 2-pounder gun fired a 40 millimetres (1.6 in) 0.91 pound (0.4127690567 kg) shell at a muzzle velocity of 1920 ft/s (585.2 m/s) to a distance of 3800 yards (3,474.7 m). The gun's rate of fire was approximately 96–98 rounds per minute. Close-range air defence was provided by twelve 20 mm Oerlikon
autocannon
, in two twin mounts and eight single ones. The Oerlikon fired a 0.272 pound (0.12337712464 kg) shell at a muzzle velocity of 2750 ft/s (838.2 m/s). It had a rate of fire of 465–480 rounds per minute and a maximum range of 4800 yards (4,389.1 m).
The ship was equipped with two High Angle Control System (HACS) directors on her island and each "pom-pom" mount had its own director as well. Unicorn was the first ship to mount a Type 281B early warning radar
, and each HACS director was fitted with a Type 285 gunnery radar.
Unicorn was ordered on 14 April 1939, and laid down
at Harland and Wolff
in Belfast
, Northern Ireland
on 29 June. Her construction was delayed several times in favour of higher priority projects and she was was not launched
until 20 November 1941. The ship was completed on 12 March 1943. In order to accelerate the ship's completion, the Admiralty decided in 1942 that she would not be equipped with her full suite of maintenance and repair equipment. Excluding her armament, Unicorn cost £2,531,000. The name Unicorn already in use by the 1824-built wooden frigate , which was being used as a drill ship in Dundee
, Scotland. The frigate's name was changed to Unicorn II in February 1939, then to HMS Cressy on 20 November 1941. The frigate regained her original name on 14 July 1959 after the carrier was scrapped.
and 824 Squadrons
flew aboard in April 1943. 818 Squadron had nine Fairey Swordfish
torpedo bomber
s and 824 Squadron had six. 887 Squadron, with nine Supermarine Seafire
IIC fighters was also embarked during this time. In late May, Unicorn escorted Convoy MKF 15 to Gibraltar
while carrying a number of Royal Air Force
Bristol Beaufighter
s that she off-loaded there. She escorted the returning convoy back to the Clyde
in early June. Together with the aircraft carrier , the ship made a sweep towards the Norwegian coast as part of Operation Governor, a diversion for the Allied landings in Sicily in early July. For this operation, 887 Squadron was replaced by 800 Squadron with Hawker Sea Hurricanes.
Unicorn was assigned to Force V, a flotilla of British carriers, commanded by Admiral
Philip Vian
, intended to provide air cover to Operation Avalanche, the Allied landings at Salerno. In preparation for this mission, the ship disembarked all of her Swordfish, except for a small detachment of three from 818 Squadron for self-defence, and the Sea Hurricanes of 800 Squadron. They were replaced by Seafires of 809
and 897 Squadrons. Each of the Seafire squadrons had 10 aircraft. Unicorn joined the escort carriers of Force V in August at Gibraltar before they moved forward to the Central Mediterranean for intensive training prior to the commencement of the amphibious landing on 9 September.
The ship's Seafires flew 75 sortie
s on the first day of operations and 60 on 10 September, but the Seafire was not well suited to carrier landings in low wind conditions and many were damaged in landing accidents. 44 sorties were flown on 11 September and only 18 on 12 September, even though Unicorns mechanics had managed to repair ten Seafires over the previous night. The fighter shortage grew so acute during the operation that fighters from the carriers Illustrious and , intended to provide distant cover against an attempt by the Italian fleet to interfere with the invasion, staged forward to Unicorn in order to provide air cover over the landings. By 12 September, the situation had improved so that 887 Squadron was able to fly off six Seafires to a temporary airfield ashore.
The ship returned to the UK on 20 September with a full load of damaged Seafires, in addition to her own aircraft, that were off-loaded at Glasgow
to be repaired. Afterwards, she was refitted by her builders and reconfigured for her designed role as an aircraft repair ship.
and the battleships and , the other reinforcements for the Eastern Fleet. Only four Swordfish from 818 Squadron were carried aboard at this time. The ship delivered a consignment of aircraft to Royal Navy Air Station Cochin, India, on 27 January 1944 before arriving at Trincomalee
, Ceylon on 2 February. In addition to her repair duties, the ship was often used for deck-landing practice. She was given a brief refit in Bombay during May. On 23 August, 818 Squadron was transferred to and later disbanded. On 7 November, 817 Squadron
flew aboard to provide anti-submarine protection with its Fairey Barracuda
s as Unicorn was ordered to Durban
, South Africa
. There she was to be modified with separate workshops and additional equipment to accommodate American engines which used different screw thread
s and electrical fittings.
That same month, Unicorn was transferred to the newly formed BPF. She left Durban on 1 January 1945 and arrived at Colombo
, Ceylon where she conducted deck-landing practice for pilots new to the BPF. The ship loaded 82 aircraft and 120 engines later in the month for transport to Australia, emptying the available stocks of the Eastern Fleet, and departed for Sydney
on 29 January. Unicorn arrived on 12 February and disembarked her stored aircraft. She sailed for Manus Island
, in the Admiralty Islands, on 28 February to support the BPF's training before the opening stages of Operation Iceberg. The ship arrived at San Pedro Bay, Philippines on 27 March which was to serve as the BPF's intermediate replenishment base while it supported Operation Iceberg.
The BPF was tasked to attack Japanese airfields in the Sakishima Islands
and Formosa
before and during the early stages of the invasion of Okinawa. Unicorn was primarily engaged in preparing aircraft for issue to the operational squadrons aboard the fleet carriers during this time, rather than repair them, but she did repair, modify or service 105 aircraft in March–May 1945. The ship sailed for Australia on 22 May and arrived in Sydney on 1 June. She sailed for Brisbane on 6 June to have her bottom cleaned and to load more replacement aircraft. Unicorn arrived at Manus on 22 July to prepare for operations off Japan
. She was still there when Japan surrendered
on 15 August. The ship began to ferry aircraft, equipment and men back to Australia after the surrender, a task which ended on 6 November, when she arrived at Sydney. Unicorn departed for home in December 1945 and arrived in Plymouth
in January 1946. She was decommissioned and placed in reserve.
In 1949, Unicorn was reactivated for service in the Far East, in support of the carrier . She sailed from HMNB Devonport
on 22 September with a cargo of Seafires and Fireflies
. When the Korean War
broke out in June 1950, the ship was disembarking aircraft, equipment and her maintenance personnel at RAF Sembawang, Singapore in preparation to return home and then to reserve. The Admiralty ordered her to be used as a replenishment carrier to ferry replacement aircraft and supplies to the Royal Navy and Commonwealth aircraft carriers operating in Korean waters. Unicorn left Singapore on 11 July and arrived at Sasebo
, Japan on 20 July and transferred seven Seafires and five Fireflies to Triumph. In August, the ship ferried the 1st Battalion of the Middlesex Regiment
and the Headquarters of the 27th Brigade
from Hong Kong
to Pusan, arriving on 29 August. She delivered supplies to Sasebo before returning to Singapore to begin a refit.
Unicorn resumed her duties in December, carrying about 400 troops in addition to the usual aircraft, stores and equipment. She was used by pilots for deck-landing practice en route. In March, she ferried the Gloster Meteor
jet fighters of No. 77 Squadron RAAF
to Iwakuni
, Japan. The ship remained there for the next three months so she could be used as an accommodation ship. Afterwards, Unicorn resumed her role as a ferry carrier. Whilst transiting the Shimonoseki Strait on 2 October, she destroyed the overhead power cables stretching between Honshu
and Kyushu
as they were sagging lower than normal due to a heavy snowfall. On 21 November, Unicorn and the carrier exchanged crews at Singapore and the ship began a refit shortly afterwards. After her refit was completed on 20 January 1952, she returned to her ferry duties. In April, she was "adopted" by the Middlesex Regiment (possibly one of only three ships to be honoured by an Army regiment). During operations by in July, the ship acted as a spare flight deck to allow for damaged aircraft to land without disrupting the strike operations. She arrived back at Singapore on 27 July to load more replacement aircraft, including Meteors, and sailed on 9 August for Japan. During September, Unicorn borrowed four of Oceans Hawker Sea Fury
fighters to fly combat air patrols over the fleet whilst the latter ship conducted strike operations. She was docked for maintenance in October, and embarked the First Sea Lord
, Admiral Rhoderick McGrigor
and the Commander-in-Chief, Far East Station for a tour of Commonwealth forces in Japan. At one point, Unicorn became the only aircraft carrier to conduct a shore bombardment during wartime when she engaged North Korean coastwatchers
at Chopekki Point.
The ship returned to Singapore for another refit on 15 December and did not leave Singapore until 17 July 1953. On 26 July, en route for Japan, Unicorn received a distress call from , saying that she was under attack by pirates. The carrier closed on the freighter's position at high speed and the pirates abandoned their prize when Unicorn circled the freighter with all guns bearing at less than 3000 yards (2,743.2 m). The Korean Armistice Agreement came into effect the following day, but the ship accompanied Ocean on two patrols on 30 July and 25–29 August to monitor North Korean compliance with the terms of the armistice. She sailed for home on 15 October and arrived at Devonport on 17 November, where she returned to reserve.
would also have been necessary to handle the heavier aircraft as well. The Director of Naval Construction
proposed to combine both of her hangars into a single one to eliminate problems with hangar height, but this was rejected because of the excessive cost. This reconstruction would have begun in July 1954, but the entire scheme was cancelled in November 1952 because providing existing carriers with angled flight decks was much more important.
The ship was reduced to extended reserve in March 1957 and placed on the disposal list in 1958. Unicorn was sold for scrap in June 1959 and arrived at Dalmuir
on 15 June to begin the process. Her hull was broken up at Troon
in 1960.
Light aircraft carrier
A light aircraft carrier is an aircraft carrier that is smaller than the standard carriers of a navy. The precise definition of the type varies by country; light carriers typically have a complement of aircraft only ½ to ⅔ the size of a full-sized or "fleet" carrier.-History:In World War II, the...
built for the Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...
in the late 1930s. She was completed during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
and provided air cover over the amphibious landing at Salerno, Italy in September 1943. The ship was transferred to the Eastern Fleet in the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
at the end of the year. Unicorn supported the aircraft carriers of the fleet on their operations until the British Pacific Fleet
British Pacific Fleet
The British Pacific Fleet was a British Commonwealth naval force which saw action against Japan during World War II. The fleet was composed of British Commonwealth naval vessels. The BPF formally came into being on 22 November 1944...
(BPF) was formed in November 1944. She was transferred to Australia in early 1945 to support the BPF's operations during Operation Iceberg, the Allied invasion of Okinawa in May. To shorten the time required to replenish the BPF's carriers, the ship was based in the Admiralty Islands
Admiralty Islands
The Admiralty Islands are a group of eighteen islands in the Bismarck Archipelago, to the north of New Guinea in the south Pacific Ocean. These are also sometimes called the Manus Islands, after the largest island. These rainforest-covered islands form part of Manus Province, the smallest and...
and in the Philippine Islands until the Japanese surrender in August. Unicorn was decommissioned and placed in reserve
Reserve fleet
A reserve fleet is a collection of naval vessels of all types that are fully equipped for service but are not currently needed, and thus partially or fully decommissioned. A reserve fleet is informally said to be "in mothballs" or "mothballed"; an equivalent expression in unofficial modern U.S....
when she returned to the UK in January 1946.
The ship was recommissioned in 1949 to support the light carrier of the Far East Fleet, as the Eastern Fleet had been redesignated after the end of World War II. She was unloading aircraft and equipment in Singapore
Singapore
Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...
in June 1950 when the Korean War
Korean War
The Korean War was a conventional war between South Korea, supported by the United Nations, and North Korea, supported by the People's Republic of China , with military material aid from the Soviet Union...
began. She spent most of the war ferrying aircraft, troops, stores and equipment in support of Commonwealth
Commonwealth of Nations
The Commonwealth of Nations, normally referred to as the Commonwealth and formerly known as the British Commonwealth, is an intergovernmental organisation of fifty-four independent member states...
operations in Korea. Unicorn supported other carriers during operations in Korea, but she became the only aircraft carrier to conduct a shore bombardment with her guns during wartime when she attacked North Korean observers on the coast during the war. The ship returned to the UK after the end of the war and was again placed in reserve. She was listed for disposal in 1958 and sold for scrap
Ship breaking
Ship breaking or ship demolition is a type of ship disposal involving the breaking up of ships for scrap recycling. Most ships have a lifespan of a few decades before there is so much wear that refitting and repair becomes uneconomical. Ship breaking allows materials from the ship, especially...
in 1959.
Design, description and construction
The Abyssinia CrisisAbyssinia Crisis
The Abyssinia Crisis was a diplomatic crisis during the interwar period originating in the "Walwal incident." This incident resulted from the ongoing conflict between the Kingdom of Italy and the Empire of Ethiopia...
of 1934–35 demonstrated to the Admiralty
Admiralty
The Admiralty was formerly the authority in the Kingdom of England, and later in the United Kingdom, responsible for the command of the Royal Navy...
that it needed a depot ship
Depot ship
A depot ship is a ship which acts as a mobile or fixed base for other ships and submarines or supports a naval base. Depot ships may be specifically designed for their purpose or be converted from another purpose...
to support the aircraft carriers in active service, just like submarine
Submarine tender
A submarine tender is a type of ship that supplies and supports submarines.Submarines are small compared to most oceangoing vessels, and generally do not have the ability to carry large amounts of food, fuel, torpedoes, and other supplies, nor to carry a full array of maintenance equipment and...
and destroyer tender
Destroyer tender
A destroyer tender is a ship designed to provide maintenance support to a flotilla of destroyers or other small warships. The use of this class has faded from its peak in the first half of the 20th century as the roles of small combatants have evolved .Due to the increased size and automation of...
s supported those types. Such a ship would be able to perform a wider range of aircraft repair and maintenance tasks than aircraft carriers and on the full range of aircraft operated by the Royal Navy, including amphibian
Amphibious aircraft
An amphibious aircraft or amphibian is an aircraft that can take off and land on either land or water. Fixed-wing amphibious aircraft are seaplanes that are equipped with retractable wheels, at the expense of extra weight and complexity, plus diminished range and fuel economy compared to planes...
s. Admiral Reginald Henderson
Reginald Henderson
Admiral Sir Reginald Guy Hannam Henderson KCB was a Royal Navy officer who went on to be Third Sea Lord and Controller of the Navy.-Naval career:...
, Controller of the Navy was instrumental for gaining approval for the ship and ensuring that she had a complete flight deck that would allow her to land, service and launch aircraft on active operations. She was was the first ship built in any navy that could "carry out the full range of aircraft maintenance and repair work in addition to the ability to operate aircraft from the flight deck". In practice, Unicorn proved the value of the concept and two similar support ships, and were converted into aircraft maintenance ships by modifying light aircraft carriers still under construction.
Unicorn had an overall length of 640 feet (195.1 m), a beam of 90 in 3 in (27.51 m), and a draught of 23 feet (7 m) at deep load. She was somewhat overweight as completed and displaced 16510 LT at standard load rather than her designed 14750 LT. Each of the ship's two sets of Parsons
Parsons Marine Steam Turbine Company
Parsons Marine Steam Turbine Company was a British engineering company based in Wallsend, North England, on the River Tyne.-History:The company was founded by Charles Algernon Parsons in 1897 with £500,000 of capital, and specialised in building the steam turbine engines that he had invented for...
geared steam turbine
Steam turbine
A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884....
s drove one 15 feet (4.6 m) propeller. Steam was supplied by six Admiralty three-drum water-tube boiler
Water-tube boiler
A water tube boiler is a type of boiler in which water circulates in tubes heated externally by the fire. Fuel is burned inside the furnace, creating hot gas which heats water in the steam-generating tubes...
s operating at a pressure of 400 pound per square inch. The turbines were designed for a total of 40000 shp and gave Unicorn a speed of 24 knots (13.1 m/s). The ship carried 3000 LT of fuel oil
Fuel oil
Fuel oil is a fraction obtained from petroleum distillation, either as a distillate or a residue. Broadly speaking, fuel oil is any liquid petroleum product that is burned in a furnace or boiler for the generation of heat or used in an engine for the generation of power, except oils having a flash...
which gave her a range of 7000 nautical miles (12,964 km) at 13.5 knots (7.3 m/s).
In order to land aircraft aboard, Unicorn was therefore designed with a full-length, 600 feet (182.9 m)-long flight deck
Flight deck
The flight deck of an aircraft carrier is the surface from which its aircraft take off and land, essentially a miniature airfield at sea. On smaller naval ships which do not have aviation as a primary mission, the landing area for helicopters and other VTOL aircraft is also referred to as the...
with arresting gear
Arresting gear
Arresting gear, or arrestor gear, is the name used for mechanical systems designed to rapidly decelerate an aircraft as it lands. Arresting gear on aircraft carriers is an essential component of naval aviation, and it is most commonly used on CATOBAR and STOBAR aircraft carriers. Similar systems...
. She was also fitted with a catapult
Aircraft catapult
An aircraft catapult is a device used to launch aircraft from ships—in particular aircraft carriers—as a form of assisted take off. It consists of a track built into the flight deck, below which is a large piston or shuttle that is attached through the track to the nose gear of the aircraft, or in...
capable of launching a 14000 pounds (6,350.3 kg) aircraft to a speed of 66 knots (35.9 m/s). The ship had two hangar
Hangar
A hangar is a closed structure to hold aircraft or spacecraft in protective storage. Most hangars are built of metal, but other materials such as wood and concrete are also sometimes used...
s, each 16 in 6 in (5.03 m) high. Aircraft were transported between the hangars and the flight deck by two aircraft lifts (elevators); the forward lift measured 33 by 45 ft (10.1 by 13.7 m) and the rear one 24 by 46 ft (7.3 by 14 m). Unicorn could carry about 33 operational aircraft. Bulk petrol storage consisted of 36500 imp gal (165,932.3 l; 43,834.7 US gal). During wartime, the ship's crew totaled 1200. The ship carried a self-propelled lighter
Lighter (barge)
A lighter is a type of flat-bottomed barge used to transfer goods and passengers to and from moored ships. Lighters were traditionally unpowered and were moved and steered using long oars called "sweeps," with their motive power provided by water currents...
under the rear of the flight deck to allow unflyable aircraft to be transferred between ships or to shore facilities. This lighter was lowered flush with the upper hangar deck so that an aircraft could be rolled onto to it or an aircraft could be lifted onto it once the lighter was in the water.
Unicorn was armed with four twin mounts for the 45-calibre QF 4-inch Mk XVI
QF 4 inch Mk XVI naval gun
The QF 4 inch Mk XVI gun was the standard British Commonwealth naval anti-aircraft and dual-purpose gun of World War II.-Service:The Mk XVI superseded the earlier QF 4 inch Mk V naval gun on many Royal Naval ships during the late 1930s and early 1940s...
dual purpose gun
Dual purpose gun
A dual purpose gun is a naval artillery mounting designed to engage both surface and air targets.-Description:Second World War-era capital ships had four classes of artillery: the heavy main battery, intended to engage opposing battleships and cruisers ; a secondary battery for use against enemy...
. This mounting could elevate from −10 to +80°. The Mk XVI gun fired about 12 35 pounds (15.9 kg) high-explosive shells per minute at a muzzle velocity of 2660 ft/s (810.8 m/s). Against surface targets it had a range of 19850 yards (18,150.8 m) and a maximum ceiling of 39000 ft (11,887.2 m), but an effective anti-aircraft range of much less. She was also equipped with four quadruple mounts for the 40 millimetres (1.6 in) QF 2-pounder Mk VIII gun
QF 2 pounder naval gun
The 2-pounder gun, officially designated the QF 2-pounder and universally known as the pom-pom, was a 1.575 inch British autocannon, used famously as an anti-aircraft gun by the Royal Navy. The name came from the sound that the original models make when firing...
("pom-pom"). These gun mounts could depress to −10° and elevate to a maximum of +80°. The Mk VIII 2-pounder gun fired a 40 millimetres (1.6 in) 0.91 pound (0.4127690567 kg) shell at a muzzle velocity of 1920 ft/s (585.2 m/s) to a distance of 3800 yards (3,474.7 m). The gun's rate of fire was approximately 96–98 rounds per minute. Close-range air defence was provided by twelve 20 mm Oerlikon
Oerlikon 20 mm cannon
The Oerlikon 20 mm cannon is a series of autocannons, based on an original design by Reinhold Becker of Germany, very early in World War I, and widely produced by Oerlikon Contraves and others...
autocannon
Autocannon
An autocannon or automatic cannon is a rapid-fire projectile weapon firing a shell as opposed to the bullet fired by a machine gun. Autocannons often have a larger caliber than a machine gun . Usually, autocannons are smaller than a field gun or other artillery, and are mechanically loaded for a...
, in two twin mounts and eight single ones. The Oerlikon fired a 0.272 pound (0.12337712464 kg) shell at a muzzle velocity of 2750 ft/s (838.2 m/s). It had a rate of fire of 465–480 rounds per minute and a maximum range of 4800 yards (4,389.1 m).
The ship was equipped with two High Angle Control System (HACS) directors on her island and each "pom-pom" mount had its own director as well. Unicorn was the first ship to mount a Type 281B early warning radar
Early warning radar
An early warning radar is any radar system used primarily for the long-range detection of its targets, i.e., allowing defences to be alerted as early as possible before the intruder reaches its target, giving the defences the maximum time in which to operate...
, and each HACS director was fitted with a Type 285 gunnery radar.
Unicorn was ordered on 14 April 1939, and laid down
Keel
In boats and ships, keel can refer to either of two parts: a structural element, or a hydrodynamic element. These parts overlap. As the laying down of the keel is the initial step in construction of a ship, in British and American shipbuilding traditions the construction is dated from this event...
at Harland and Wolff
Harland and Wolff
Harland and Wolff Heavy Industries is a Northern Irish heavy industrial company, specialising in shipbuilding and offshore construction, located in Belfast, Northern Ireland....
in Belfast
Belfast
Belfast is the capital of and largest city in Northern Ireland. By population, it is the 14th biggest city in the United Kingdom and second biggest on the island of Ireland . It is the seat of the devolved government and legislative Northern Ireland Assembly...
, Northern Ireland
Northern Ireland
Northern Ireland is one of the four countries of the United Kingdom. Situated in the north-east of the island of Ireland, it shares a border with the Republic of Ireland to the south and west...
on 29 June. Her construction was delayed several times in favour of higher priority projects and she was was not launched
Ship naming and launching
The ceremonies involved in naming and launching naval ships are based in traditions thousands of years old.-Methods of launch:There are three principal methods of conveying a new ship from building site to water, only two of which are called "launching." The oldest, most familiar, and most widely...
until 20 November 1941. The ship was completed on 12 March 1943. In order to accelerate the ship's completion, the Admiralty decided in 1942 that she would not be equipped with her full suite of maintenance and repair equipment. Excluding her armament, Unicorn cost £2,531,000. The name Unicorn already in use by the 1824-built wooden frigate , which was being used as a drill ship in Dundee
Dundee
Dundee is the fourth-largest city in Scotland and the 39th most populous settlement in the United Kingdom. It lies within the eastern central Lowlands on the north bank of the Firth of Tay, which feeds into the North Sea...
, Scotland. The frigate's name was changed to Unicorn II in February 1939, then to HMS Cressy on 20 November 1941. The frigate regained her original name on 14 July 1959 after the carrier was scrapped.
World War II
Whilst working up, 818818 Naval Air Squadron
818 Naval Air Squadron was a Royal Navy Fleet Air Arm carrier based squadron formed in August 1939. It served on a number of the Navy's aircraft carriers during the Second World War, serving in most of the theatres of the war, before decommissioning at the end of the war.-Norway and the...
and 824 Squadrons
818 Naval Air Squadron
818 Naval Air Squadron was a Royal Navy Fleet Air Arm carrier based squadron formed in August 1939. It served on a number of the Navy's aircraft carriers during the Second World War, serving in most of the theatres of the war, before decommissioning at the end of the war.-Norway and the...
flew aboard in April 1943. 818 Squadron had nine Fairey Swordfish
Fairey Swordfish
The Fairey Swordfish was a torpedo bomber built by the Fairey Aviation Company and used by the Fleet Air Arm of the Royal Navy during the Second World War...
torpedo bomber
Torpedo bomber
A torpedo bomber is a bomber aircraft designed primarily to attack ships with aerial torpedoes which could also carry out conventional bombings. Torpedo bombers existed almost exclusively prior to and during World War II when they were an important element in many famous battles, notably the...
s and 824 Squadron had six. 887 Squadron, with nine Supermarine Seafire
Supermarine Seafire
The Supermarine Seafire was a naval version of the Supermarine Spitfire specially adapted for operation from aircraft carriers. The name Seafire was arrived at by collapsing the longer name Sea Spitfire.-Origins of the Seafire:...
IIC fighters was also embarked during this time. In late May, Unicorn escorted Convoy MKF 15 to Gibraltar
Gibraltar
Gibraltar is a British overseas territory located on the southern end of the Iberian Peninsula at the entrance of the Mediterranean. A peninsula with an area of , it has a northern border with Andalusia, Spain. The Rock of Gibraltar is the major landmark of the region...
while carrying a number of Royal Air Force
Royal Air Force
The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...
Bristol Beaufighter
Bristol Beaufighter
The Bristol Type 156 Beaufighter, often referred to as simply the Beau, was a British long-range heavy fighter modification of the Bristol Aeroplane Company's earlier Beaufort torpedo bomber design...
s that she off-loaded there. She escorted the returning convoy back to the Clyde
Firth of Clyde
The Firth of Clyde forms a large area of coastal water, sheltered from the Atlantic Ocean by the Kintyre peninsula which encloses the outer firth in Argyll and Ayrshire, Scotland. The Kilbrannan Sound is a large arm of the Firth of Clyde, separating the Kintyre Peninsula from the Isle of Arran.At...
in early June. Together with the aircraft carrier , the ship made a sweep towards the Norwegian coast as part of Operation Governor, a diversion for the Allied landings in Sicily in early July. For this operation, 887 Squadron was replaced by 800 Squadron with Hawker Sea Hurricanes.
Unicorn was assigned to Force V, a flotilla of British carriers, commanded by Admiral
Admiral (United Kingdom)
Admiral is a senior rank of the Royal Navy of the United Kingdom, which equates to the NATO rank code OF-9, outranked only by the rank Admiral of the Fleet...
Philip Vian
Philip Vian
Admiral of the Fleet Sir Philip Louis Vian, GCB, KBE, DSO & Two Bars was a British naval officer who served in both World Wars....
, intended to provide air cover to Operation Avalanche, the Allied landings at Salerno. In preparation for this mission, the ship disembarked all of her Swordfish, except for a small detachment of three from 818 Squadron for self-defence, and the Sea Hurricanes of 800 Squadron. They were replaced by Seafires of 809
809 Naval Air Squadron
-WWII:Formed in January 1941 at St Merryn with 12 Fairey Fulmars, the squadron embarked in HMS Victorious in July 1941. At first involved in operations against Petsamo and Bodø, and then the convoys to North Russia, Victorious and her air group fought in the Mediterranean from July 1942, including...
and 897 Squadrons. Each of the Seafire squadrons had 10 aircraft. Unicorn joined the escort carriers of Force V in August at Gibraltar before they moved forward to the Central Mediterranean for intensive training prior to the commencement of the amphibious landing on 9 September.
The ship's Seafires flew 75 sortie
Sortie
Sortie is a term for deployment or dispatch of one military unit, be it an aircraft, ship, or troops from a strongpoint. The sortie, whether by one or more aircraft or vessels, usually has a specific mission....
s on the first day of operations and 60 on 10 September, but the Seafire was not well suited to carrier landings in low wind conditions and many were damaged in landing accidents. 44 sorties were flown on 11 September and only 18 on 12 September, even though Unicorns mechanics had managed to repair ten Seafires over the previous night. The fighter shortage grew so acute during the operation that fighters from the carriers Illustrious and , intended to provide distant cover against an attempt by the Italian fleet to interfere with the invasion, staged forward to Unicorn in order to provide air cover over the landings. By 12 September, the situation had improved so that 887 Squadron was able to fly off six Seafires to a temporary airfield ashore.
The ship returned to the UK on 20 September with a full load of damaged Seafires, in addition to her own aircraft, that were off-loaded at Glasgow
Glasgow
Glasgow is the largest city in Scotland and third most populous in the United Kingdom. The city is situated on the River Clyde in the country's west central lowlands...
to be repaired. Afterwards, she was refitted by her builders and reconfigured for her designed role as an aircraft repair ship.
Far East
At the end of December 1943, Unicorn joined Illustrious, the battlecruiserBattlecruiser
Battlecruisers were large capital ships built in the first half of the 20th century. They were developed in the first decade of the century as the successor to the armoured cruiser, but their evolution was more closely linked to that of the dreadnought battleship...
and the battleships and , the other reinforcements for the Eastern Fleet. Only four Swordfish from 818 Squadron were carried aboard at this time. The ship delivered a consignment of aircraft to Royal Navy Air Station Cochin, India, on 27 January 1944 before arriving at Trincomalee
Trincomalee
Trincomalee is a port city in Eastern Province, Sri Lanka and lies on the east coast of the island, about 113 miles south of Jaffna. It has a population of approximately 100,000 . The city is built on a peninsula, which divides the inner and outer harbours. Overlooking the Kottiyar Bay,...
, Ceylon on 2 February. In addition to her repair duties, the ship was often used for deck-landing practice. She was given a brief refit in Bombay during May. On 23 August, 818 Squadron was transferred to and later disbanded. On 7 November, 817 Squadron
817 Naval Air Squadron
817 Naval Air Squadron was a unit of the Royal Navy Fleet Air Arm during the Second World War.In 1941, the squadron operated Fairey Albacore aircraft in the Anti-Submarine Warfare role in Icelandic and Mediterranean waters...
flew aboard to provide anti-submarine protection with its Fairey Barracuda
Fairey Barracuda
The Fairey Barracuda was a British carrier-borne torpedo- and dive bomber used during the Second World War, the first of its type used by the Royal Navy's Fleet Air Arm to be fabricated entirely from metal. It was introduced as a replacement for the Fairey Swordfish and Fairey Albacore biplanes...
s as Unicorn was ordered to Durban
Durban
Durban is the largest city in the South African province of KwaZulu-Natal and the third largest city in South Africa. It forms part of the eThekwini metropolitan municipality. Durban is famous for being the busiest port in South Africa. It is also seen as one of the major centres of tourism...
, South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
. There she was to be modified with separate workshops and additional equipment to accommodate American engines which used different screw thread
Screw thread
A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread...
s and electrical fittings.
That same month, Unicorn was transferred to the newly formed BPF. She left Durban on 1 January 1945 and arrived at Colombo
Colombo
Colombo is the largest city of Sri Lanka. It is located on the west coast of the island and adjacent to Sri Jayawardenapura Kotte, the capital of Sri Lanka. Colombo is often referred to as the capital of the country, since Sri Jayawardenapura Kotte is a satellite city of Colombo...
, Ceylon where she conducted deck-landing practice for pilots new to the BPF. The ship loaded 82 aircraft and 120 engines later in the month for transport to Australia, emptying the available stocks of the Eastern Fleet, and departed for Sydney
Sydney
Sydney is the most populous city in Australia and the state capital of New South Wales. Sydney is located on Australia's south-east coast of the Tasman Sea. As of June 2010, the greater metropolitan area had an approximate population of 4.6 million people...
on 29 January. Unicorn arrived on 12 February and disembarked her stored aircraft. She sailed for Manus Island
Manus Island
Manus Island is part of Manus Province in northern Papua New Guinea and is the largest island of the Admiralty Islands. It is the fifth largest island in Papua New Guinea with an area of 2,100 km², measuring around 100 km × 30 km. According to the 2000 census, Manus Island had a...
, in the Admiralty Islands, on 28 February to support the BPF's training before the opening stages of Operation Iceberg. The ship arrived at San Pedro Bay, Philippines on 27 March which was to serve as the BPF's intermediate replenishment base while it supported Operation Iceberg.
The BPF was tasked to attack Japanese airfields in the Sakishima Islands
Sakishima Islands
The are an island chain located at the southernmost end of the Japanese Archipelago. They are part of the Nansei Islands and include the Miyako Islands and the Yaeyama Islands...
and Formosa
Formosa
Formosa or Ilha Formosa is a Portuguese historical name for Taiwan , literally meaning, "Beautiful Island". The term may also refer to:-Places:* Formosa Strait, another name for the Taiwan Strait...
before and during the early stages of the invasion of Okinawa. Unicorn was primarily engaged in preparing aircraft for issue to the operational squadrons aboard the fleet carriers during this time, rather than repair them, but she did repair, modify or service 105 aircraft in March–May 1945. The ship sailed for Australia on 22 May and arrived in Sydney on 1 June. She sailed for Brisbane on 6 June to have her bottom cleaned and to load more replacement aircraft. Unicorn arrived at Manus on 22 July to prepare for operations off Japan
Japan campaign
The Japan Campaign was a series of battles and engagements in and around the Japanese Home Islands, between Allied forces and the forces of Imperial Japan during the last stages of the Pacific Campaign of World War II. The Japan Campaign lasted from around June 1944 to August 1945.-Air war:Periodic...
. She was still there when Japan surrendered
Surrender of Japan
The surrender of Japan in 1945 brought hostilities of World War II to a close. By the end of July 1945, the Imperial Japanese Navy was incapable of conducting operations and an Allied invasion of Japan was imminent...
on 15 August. The ship began to ferry aircraft, equipment and men back to Australia after the surrender, a task which ended on 6 November, when she arrived at Sydney. Unicorn departed for home in December 1945 and arrived in Plymouth
Plymouth
Plymouth is a city and unitary authority area on the coast of Devon, England, about south-west of London. It is built between the mouths of the rivers Plym to the east and Tamar to the west, where they join Plymouth Sound...
in January 1946. She was decommissioned and placed in reserve.
Post-war
HMNB Devonport
Her Majesty's Naval Base Devonport , is one of three operating bases in the United Kingdom for the Royal Navy . HMNB Devonport is located in Devonport, in the west of the city of Plymouth in Devon, England...
on 22 September with a cargo of Seafires and Fireflies
Fairey Firefly
The Fairey Firefly was a British Second World War-era carrier-borne fighter aircraft and anti-submarine aircraft of the Fleet Air Arm ....
. When the Korean War
Korean War
The Korean War was a conventional war between South Korea, supported by the United Nations, and North Korea, supported by the People's Republic of China , with military material aid from the Soviet Union...
broke out in June 1950, the ship was disembarking aircraft, equipment and her maintenance personnel at RAF Sembawang, Singapore in preparation to return home and then to reserve. The Admiralty ordered her to be used as a replenishment carrier to ferry replacement aircraft and supplies to the Royal Navy and Commonwealth aircraft carriers operating in Korean waters. Unicorn left Singapore on 11 July and arrived at Sasebo
Sasebo, Nagasaki
is a city located in Nagasaki Prefecture, Japan. As of 2011, the city has an estimated population of 259,800 and the density of 609 persons per km². The total area is 426.47 km². The locality is famed for its scenic beauty. The city includes a part of Saikai National Park...
, Japan on 20 July and transferred seven Seafires and five Fireflies to Triumph. In August, the ship ferried the 1st Battalion of the Middlesex Regiment
Middlesex Regiment
The Middlesex Regiment was a regiment of the British Army. It was formed in 1881 as part of the Childers Reforms when the 57th and 77th Regiments of Foot were amalgamated with the county's militia and rifle volunteer units.On 31 December 1966 The Middlesex Regiment was amalgamated with three...
and the Headquarters of the 27th Brigade
27th Infantry Brigade (United Kingdom)
The 27th Infantry Brigade was a British Army brigade during the Second World War and Korean War. In Korea, the brigade was known as 27th British Commonwealth Brigade due to the addition of Canadian, Australian, New Zealand and Indian units....
from Hong Kong
Hong Kong
Hong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...
to Pusan, arriving on 29 August. She delivered supplies to Sasebo before returning to Singapore to begin a refit.
Unicorn resumed her duties in December, carrying about 400 troops in addition to the usual aircraft, stores and equipment. She was used by pilots for deck-landing practice en route. In March, she ferried the Gloster Meteor
Gloster Meteor
The Gloster Meteor was the first British jet fighter and the Allies' first operational jet. It first flew in 1943 and commenced operations on 27 July 1944 with 616 Squadron of the Royal Air Force...
jet fighters of No. 77 Squadron RAAF
No. 77 Squadron RAAF
No. 77 Squadron is a Royal Australian Air Force fighter squadron. The Squadron was formed in 1942 and currently operates F/A-18 Hornet aircraft from RAAF Base Williamtown.-History:...
to Iwakuni
Marine Corps Air Station Iwakuni
Marine Corps Air Station Iwakuni or MCAS Iwakuni is a United States Marine Corps air station located in the Nishiki river delta, southeast of the Iwakuni Station in the city of Iwakuni, Yamaguchi in Japan.-Tenant commands:...
, Japan. The ship remained there for the next three months so she could be used as an accommodation ship. Afterwards, Unicorn resumed her role as a ferry carrier. Whilst transiting the Shimonoseki Strait on 2 October, she destroyed the overhead power cables stretching between Honshu
Honshu
is the largest island of Japan. The nation's main island, it is south of Hokkaido across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyushu across the Kanmon Strait...
and Kyushu
Kyushu
is the third largest island of Japan and most southwesterly of its four main islands. Its alternate ancient names include , , and . The historical regional name is referred to Kyushu and its surrounding islands....
as they were sagging lower than normal due to a heavy snowfall. On 21 November, Unicorn and the carrier exchanged crews at Singapore and the ship began a refit shortly afterwards. After her refit was completed on 20 January 1952, she returned to her ferry duties. In April, she was "adopted" by the Middlesex Regiment (possibly one of only three ships to be honoured by an Army regiment). During operations by in July, the ship acted as a spare flight deck to allow for damaged aircraft to land without disrupting the strike operations. She arrived back at Singapore on 27 July to load more replacement aircraft, including Meteors, and sailed on 9 August for Japan. During September, Unicorn borrowed four of Oceans Hawker Sea Fury
Hawker Sea Fury
The Hawker Sea Fury was a British fighter aircraft developed for the Royal Navy by Hawker during the Second World War. The last propeller-driven fighter to serve with the Royal Navy, it was also one of the fastest production single piston-engined aircraft ever built.-Origins:The Hawker Fury was an...
fighters to fly combat air patrols over the fleet whilst the latter ship conducted strike operations. She was docked for maintenance in October, and embarked the First Sea Lord
First Sea Lord
The First Sea Lord is the professional head of the Royal Navy and the whole Naval Service; it was formerly known as First Naval Lord. He also holds the title of Chief of Naval Staff, and is known by the abbreviations 1SL/CNS...
, Admiral Rhoderick McGrigor
Rhoderick McGrigor
Admiral of the Fleet Sir Rhoderick Robert McGrigor GCB was a Royal Navy officer and the British First Sea Lord from 1951 to 1955. During his years as professional head of the Royal Navy, he is most remembered as a leading proponent of carrier-based air power.-Early life:Rhoderick Robert McGrigor...
and the Commander-in-Chief, Far East Station for a tour of Commonwealth forces in Japan. At one point, Unicorn became the only aircraft carrier to conduct a shore bombardment during wartime when she engaged North Korean coastwatchers
Coastwatchers
The Coastwatchers, also known as the Coast Watch Organisation, Combined Field Intelligence Service or Section C, Allied Intelligence Bureau, were Allied military intelligence operatives stationed on remote Pacific islands during World War II to observe enemy movements and rescue stranded Allied...
at Chopekki Point.
The ship returned to Singapore for another refit on 15 December and did not leave Singapore until 17 July 1953. On 26 July, en route for Japan, Unicorn received a distress call from , saying that she was under attack by pirates. The carrier closed on the freighter's position at high speed and the pirates abandoned their prize when Unicorn circled the freighter with all guns bearing at less than 3000 yards (2,743.2 m). The Korean Armistice Agreement came into effect the following day, but the ship accompanied Ocean on two patrols on 30 July and 25–29 August to monitor North Korean compliance with the terms of the armistice. She sailed for home on 15 October and arrived at Devonport on 17 November, where she returned to reserve.
Disposal
In 1951, Unicorn was considered for modernization to make her capable of operating modern, heavier jet aircraft. This would have required fitting of a steam catapult, reinforcing her flight deck to handle heavier aircraft and moving and enlarging her forward lift to make room for the new catapult and larger aircraft. A new craneCrane (machine)
A crane is a type of machine, generally equipped with a hoist, wire ropes or chains, and sheaves, that can be used both to lift and lower materials and to move them horizontally. It uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of...
would also have been necessary to handle the heavier aircraft as well. The Director of Naval Construction
Director of Naval Construction
The Director of Naval Construction was a senior British civil servant post in the Admiralty, that part of the British Civil Service that oversaw the Royal Navy. The post existed from 1860 to 1966....
proposed to combine both of her hangars into a single one to eliminate problems with hangar height, but this was rejected because of the excessive cost. This reconstruction would have begun in July 1954, but the entire scheme was cancelled in November 1952 because providing existing carriers with angled flight decks was much more important.
The ship was reduced to extended reserve in March 1957 and placed on the disposal list in 1958. Unicorn was sold for scrap in June 1959 and arrived at Dalmuir
Dalmuir
Dalmuir is an area on the western side of Clydebank, in West Dunbartonshire, Scotland.-Location:It is neighboured by the village of Old Kilpatrick, the Mountblow and Parkhall areas of Clydebank, as well as the town centre...
on 15 June to begin the process. Her hull was broken up at Troon
Troon
Troon is a town in South Ayrshire. It is situated on the west coast of Scotland, about eight miles north of Ayr and three miles northwest of Glasgow Prestwick International Airport. Lying across the Firth of Clyde, the Isle of Arran can be seen. Troon is also a port with freight and ferry services...
in 1960.