Sector clock

Last updated

The red, yellow and blue triangles each span five minutes. The base is mahogany. World War II RAF sector clock.jpg
The red, yellow and blue triangles each span five minutes. The base is mahogany.

A Sector clock or colour change clock was a round colour-coded clock used at military airfields and observation posts in the United Kingdom to help track the movements of enemy aircraft and control friendly aircraft.

Clock instrument that measures the passage of time

A clock is an instrument used to measure, keep, and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units: the day, the lunar month, and the year. Devices operating on several physical processes have been used over the millennia.

Contents

History

Originally known as "colour change clocks", they were introduced during the First World War by the Royal Flying Corps in 1917 to monitor the movements of German aircraft. Later, during the Second World War they played a significant role in the Battle of Britain and continued to be used by the Royal Air Force and Royal Observer Corps (ROC) as simple clocks and keepsakes, until the end of the Cold War period. These clocks are now sought after by collectors of aeronautica.

Royal Flying Corps former air warfare service of the British Army

The Royal Flying Corps (RFC) was the air arm of the British Army before and during the First World War, until it merged with the Royal Naval Air Service on 1 April 1918 to form the Royal Air Force. During the early part of the war, the RFC supported the British Army by artillery co-operation and photographic reconnaissance. This work gradually led RFC pilots into aerial battles with German pilots and later in the war included the strafing of enemy infantry and emplacements, the bombing of German military airfields and later the strategic bombing of German industrial and transport facilities.

Battle of Britain Air campaign between Germany and the United Kingdom during the Second World War

The Battle of Britain was a military campaign of the Second World War, in which the Royal Air Force (RAF) defended the United Kingdom (UK) against large-scale attacks by Nazi Germany's air force, the Luftwaffe. It has been described as the first major military campaign fought entirely by air forces. The British officially recognise the battle's duration as being from 10 July until 31 October 1940, which overlaps the period of large-scale night attacks known as The Blitz, that lasted from 7 September 1940 to 11 May 1941. German historians do not accept this subdivision and regard the battle as a single campaign lasting from July 1940 to June 1941, including the Blitz.

Royal Air Force Aerial warfare service branch of the British Armed Forces

The Royal Air Force (RAF) is the United Kingdom's aerial warfare force. Formed towards the end of the First World War on 1 April 1918, it is the oldest independent air force in the world. Following victory over the Central Powers in 1918 the RAF emerged as, at the time, the largest air force in the world. Since its formation, the RAF has taken a significant role in British military history. In particular, it played a large part in the Second World War where it fought its most famous campaign, the Battle of Britain.

There were two versions of the clock issued, either for RAF Sector use or for the ROC. The RAF Sector Clock has an old style "King's Crown" RAF Warrant Officer's insignia under the "24" at top centre. [1] The ROC clock has a plain face with no insignia.

Clocks were either electrical or mechanical. Electric clocks usually have the coloured segments pointing inwards, mechanical clocks have the segments pointing outwards. [2]

The United States Army Air Force (USAAF) also adopted the RAF sector clock with a coloured block pattern rather than triangles. [3]

Function

RAF Digby Sector Operations Room, sector clock with inward-pointing segments on wall RAF Digby Ops Room.jpg
RAF Digby Sector Operations Room, sector clock with inward-pointing segments on wall

The Sector Clock was a fundamental part of Ground-controlled interception (GCI) before modern computerized systems were put in place for airspace control. The clock face is marked with five-minute red, yellow and blue triangular segments. [4] It has an outer 12-hour ring and an inner 24-hour dial.

Ground-controlled interception

Ground-controlled interception (GCI) is an air defence tactic whereby one or more radar stations or other observational stations are linked to a command communications centre which guides interceptor aircraft to an airborne target. This tactic was pioneered during World War I by the London Air Defence Area organization, which became the Royal Air Force's Dowding system in World War II, the first national-scale system. The Luftwaffe introduced similar systems during the war, but most other combatants did not suffer the same threat of air attack and did not develop complex systems like these until the Cold War era.

Clock face Part of a clock that displays the time

A clock face, or dial, is the part of an analog clock that displays the time through the use of a fixed-numbered dial or dials and moving hands. In its most basic form, recognized throughout the world, the periphery of the dial is numbered 1 through 12 indicating the hours in a 12-hour cycle, and a short hour hand makes two revolutions in a day. A long minute hand makes one revolution every hour. The face may also include a second hand, which makes one revolution per minute. The term is less commonly used for the time display on digital clocks and watches.

Aircraft position was recorded along with the colour of the triangle beneath the minute hand at the time of sighting. This was reported to sector headquarters, where counters of the relayed colour were used to represent each air raid on a large table with a map of the UK overlaid with a British Modified Grid. As the plots of the raiding aircraft moved, the counters were pushed across the map by magnetic "rakes". This system enabled "Fighter Controllers" to see very quickly where each formation was heading and allowed an estimate to be made of possible targets. The age of the information was readily apparent from the colour of the counter. Because of the simplicity of the system, decisions could be made quickly and easily.

See also

Related Research Articles

Wing commander is a senior commissioned rank in the British Royal Air Force and air forces of many countries which have historical British influence, including many Commonwealth countries but not including Canada and South Africa. It is sometimes used as the English translation of an equivalent rank in countries which have a non-English air force-specific rank structure. It ranks immediately above squadron leader and immediately below group captain. It has a NATO ranking code of OF-4, and is equivalent to commander in the Royal Navy and to lieutenant colonel in the British Army, the Royal Marines, and the US Army, Air Force, and Marine Corps.

Group captain is a senior commissioned rank in many air forces. Group captain has a NATO rank code of OF-5, meaning that it ranks above wing commander, immediately below air commodore and is the equivalent of the naval rank of captain and the rank of colonel in other services.

Flight Lieutenant is a junior commissioned rank in air forces that use the Royal Air Force (RAF) system of ranks, especially in Commonwealth countries. It has a NATO rank code of OF-2. Flight lieutenant is abbreviated as Flt Lt in the Indian Air Force (IAF) and RAF, and as FLTLT in the Pakistan Air Force (PAF), Royal Australian Air Force (RAAF) and Royal New Zealand Air Force (RNZAF) and has sometimes also been abbreviated as F/L in many services; however, it has never been correctly abbreviated as "lieutenant". A flight lieutenant ranks above flying officer and below a squadron leader and is sometimes used as an English language translation of a similar rank in non-English-speaking countries.

RAF Northolt Royal Air Force station in West London

RAF Northolt is a Royal Air Force station in South Ruislip, 2 nautical miles from Uxbridge in the London Borough of Hillingdon, west London, England, approximately 6 mi (10 km) north of London Heathrow Airport. The station handles many private civil flights in addition to Air Force flights. Northolt has one runway in operation, spanning 1,687 m × 46 m, with a grooved asphalt surface.

RAF Bentley Priory

RAF Bentley Priory was a non-flying Royal Air Force station near Stanmore in the London Borough of Harrow. It was the headquarters of Fighter Command during the Battle of Britain and the Second World War. During the war, two bombs destroyed a wooden hut near the married quarters, a blast from a V1 flying bomb broke a few windows, and the windows in the Officers' Mess were shattered by a V2 rocket. The Royal Air Force station closed 30 May 2008 with all units relocating to new accommodation at RAF Northolt.

British Army other ranks rank insignia

The term used to refer to all ranks below officers is "other ranks". It includes warrant officers, non-commissioned officers ("NCOs") and ordinary soldiers with the rank of private or regimental equivalent. Officers may, in speaking, distinguish themselves from those "in the ranks".

The Pathfinders were target-marking squadrons in RAF Bomber Command during World War II. They located and marked targets with flares, which a main bomber force could aim at, increasing the accuracy of their bombing. The Pathfinders were normally the first to receive new blind bombing aids like Gee, Oboe and the H2S radar.

RAF Wyton UK military intelligence analysis facility in Cambridgeshire, England

Royal Air Force Wyton or more simply RAF Wyton is a Royal Air Force station near St. Ives, Cambridgeshire, England.

16 Air Assault Brigade formation of the British Army

16 Air Assault Brigade is a formation of the British Army based in Colchester in the county of Essex. It is the Army's rapid response airborne formation and is the only brigade in the British Army capable of delivering Air Manoeuvre, Air Assault and Airborne operations.

Royal Observer Corps

The Royal Observer Corps (ROC) was a civil defence organisation intended for the visual detection, identification, tracking and reporting of aircraft over Great Britain. It operated in the United Kingdom between 29 October 1925 and 31 December 1995, when the Corps' civilian volunteers were stood down. Composed mainly of civilian spare-time volunteers, ROC personnel wore a Royal Air Force (RAF) style uniform and latterly came under the administrative control of RAF Strike Command and the operational control of the Home Office. Civilian volunteers were trained and administered by a small cadre of professional full-time officers under the command of the Commandant Royal Observer Corps; latterly a serving RAF Air Commodore.

Aircraft recognition

Aircraft recognition is a visual skill taught to military personnel and civilian auxiliaries since the introduction of military aircraft in World War I. It is important for air defense and military intelligence gathering.

RAF Barton Hall

Royal Air Force Barton Hall or more simply RAF Barton Hall is a former Royal Air Force station situated between the villages of Barton and Broughton, near Preston, Lancashire, England.

Air Commodore Finlay Crerar CBE RAF, was a senior Royal Air Force officer during the Second World War who served as the fourth Commandant of the Royal Observer Corps and led the ROC through the final two years of the war and the difficult period of the V-1 flying bomb raids on Southern England.

Dowding system

The Dowding system was the world's first wide-area ground-controlled interception network, controlling the airspace across the United Kingdom from northern Scotland to the southern coast of England. It used a widespread dedicated land-line telephone network to rapidly collect information from Chain Home (CH) radar stations and the Royal Observer Corps (ROC) in order to build a single image of the entire UK airspace and then direct defensive interceptor aircraft and anti-aircraft artillery against enemy targets. The system was built by the Royal Air Force just before the start of World War II, and proved decisive in the Battle of Britain.

RAF Harlaxton

RAF Harlaxton was a Royal Air Force station near the village of Harlaxton, 3 mi (4.8 km) south west of Grantham, Lincolnshire, England. The airfield was located in a triangle of flat fields midway between Harlaxton Manor and the nearby village of Stroxton.

Battle of Britain Bunker

The Battle of Britain Bunker is an underground operations room at RAF Uxbridge, formerly used by No. 11 Group Fighter Command during the Second World War. Fighter aircraft operations were controlled from there throughout the War but most notably during the Battle of Britain and on D-Day. Today it is run by Hillingdon Council as a heritage attraction with attached museum. A new visitor centre above ground opened in March 2018.

Plotter (RAF) occupation

Plotters were employed on an early form of air traffic monitoring that played a vital role in World War II, particularly during the Battle of Britain, The Blitz and the bombing of British cities that followed. They worked at individual RAF stations' Sector Control Rooms or in the central Group Control Rooms that directed the operations of RAF fighters. The majority of plotters were female, members of the Women's Auxiliary Air Force (WAAFs).

Pip-squeak was a radio navigation system used by the British Royal Air Force during the early part of World War II. Pip-squeak used an aircraft's voice radio set to periodically send out a 1 kHz tone which was picked up by ground-based high-frequency direction finding receivers. Using three HFDF measurements, observers could determine the location of friendly aircraft using triangulation.

References

  1. ↑ "Wynton sector clock". Bennett and the Pathfinders. WW2 Pathfinders.co.uk. Retrieved 19 January 2013.
  2. ↑ "RAF Sector Clocks". Aeroclocks.com. Archived from the original on 27 December 2012. Retrieved 19 January 2013.
  3. ↑ "Clock No. 2260". Aeroclocks.com. Archived from the original on 21 September 2013. Retrieved 19 January 2013.
  4. ↑ "The Clock That Saved Britain" . Retrieved 19 January 2013.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.