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 coordinate and control air defences.
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 coordinate and control air defences.
Developed in the United Kingdom during the First World War and originally known as "colour change clocks", the Royal Flying Corps (RFC) introduced sector clocks in 1917 to aid in the chronological monitoring and position plotting of German aircraft.
During the Second World War sector clocks played a significant role in the Battle of Britain as part of the Dowding system of air defence and continued to be used by the Royal Air Force (RAF) and Royal Observer Corps (ROC) as simple clocks and keepsakes until the end of the Cold War. Two versions of the sector clock were supplied for issue by the Air Ministry; the RAF sector clock having a "King's Crown" RAF Warrant Officer's insignia under the "24", [1] the ROC issue clock having no associated insignia. Clocks were either electrical or mechanical; electric clocks usually having the coloured segments pointing inwards, mechanical clocks having the segments pointing outwards. [2]
The United States Army Air Force (USAAF) adapted the RAF sector clock using a coloured block pattern in place of triangles. [3]
Sector clocks are sought after by collectors of militaria/aeronautica. (The clock face design also appears on wrist watches commemorating the wartime role of the sector clock).
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.
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.
The Battle of Britain was a military campaign of the Second World War, in which the Royal Air Force (RAF) and the Fleet Air Arm (FAA) of the Royal Navy defended the United Kingdom (UK) against large-scale attacks by Nazi Germany's air force, the Luftwaffe. It was 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 follow this subdivision and regard the battle as a single campaign lasting from July 1940 to May 1941, including the Blitz.
A watch is a portable timepiece intended to be carried or worn by a person. It is designed to keep a consistent movement despite the motions caused by the person's activities. A wristwatch is designed to be worn around the wrist, attached by a watch strap or other type of bracelet, including metal bands, leather straps, or any other kind of bracelet. A pocket watch is designed for a person to carry in a pocket, often attached to a chain.
Air Chief Marshal Sir Keith Rodney Park, was a New Zealand-born officer of the Royal Air Force (RAF). During the Second World War, his leadership of the RAF's No. 11 Group was pivotal to the defeat of the Luftwaffe in the Battle of Britain.
The Big Wing, also known as a Balbo, was an air fighting tactic proposed during the Battle of Britain by 12 Group commander Air Vice-Marshal Trafford Leigh-Mallory and Acting Squadron Leader Douglas Bader. In essence, the tactic involved meeting incoming Luftwaffe bombing raids in strength with a wing-shaped formation of three to five squadrons. In the Battle, this tactic was employed by the Duxford Wing, under Bader's command.
Chain Home, or CH for short, was the codename for the ring of coastal early warning radar stations built by the Royal Air Force (RAF) before and during the Second World War to detect and track aircraft. Initially known as RDF, and given the official name Air Ministry Experimental Station Type 1 in 1940, the radar units were also known as Chain Home for most of their life. Chain Home was the first early warning radar network in the world and the first military radar system to reach operational status. Its effect on the war made it one of the most powerful systems of what became known as the "Wizard War".
A timer or countdown timer is a type of clock that starts from a specified time duration and stops upon reaching 00:00. A simple timer is an hourglass. Commonly, a timer triggers an alarm when it ends. A timer can be implemented through hardware or software. Stopwatches operate in the opposite direction, upwards from 00:00, measuring elapsed time since a given time instant. Time switches are timers that control an electric switch.
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 in the Battle of Britain and throughout the Second World War. The Royal Air Force station closed its operations on 30 May 2008, with all units relocating to new accommodation at RAF Northolt, a few miles away.
The Pathfinders were target-marking squadrons in RAF Bomber Command during World War II. They located and marked targets with flares, at which a main bomber force could aim, increasing the accuracy of their bombing. The Pathfinders were normally the first to receive new blind-bombing aids such as Gee, Oboe and the H2S radar.
RAF Carlisle was a Royal Air Force establishment, now closed after being used for a variety of roles over a period of fifty eight years and formerly located 2 mi (3.2 km) north of Carlisle city centre in Cumbria, England.
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.
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.
The United Kingdom Warning and Monitoring Organisation (UKWMO) was a British civilian organisation operating to provide UK military and civilian authorities with data on nuclear explosions and forecasts of fallout across the country in the event of nuclear war.
Adlertag was the first day of Unternehmen Adlerangriff, an air operation by Nazi Germany's Luftwaffe intended to destroy the British Royal Air Force (RAF). The operation came during the Battle of Britain after Britain rejected all overtures for a negotiated peace with Germany. However, Adlertag and subsequent operations failed to destroy the RAF or gain local air superiority.
The Royal Air Force uniform is the standardised military dress worn by members of the Royal Air Force. The predominant colours of Royal Air Force uniforms are blue-grey and Wedgwood blue. Many Commonwealth air forces' uniforms are also based on the RAF pattern, but with nationality shoulder flashes. The Royal Air Force Air Cadets wear similar uniforms.
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.
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. The museum was opened in 1985, with an above ground visitor centre opened in March 2018.
A Filter Room was part of RAF Fighter Command's radar defence system in Britain during the Second World War. The filter room at Fighter Command Headquarters lay at the top of the Dowding system - the integrated ground-controlled interception network that covered the United Kingdom. The operations were considered secret and, as such, were covered by the Official Secrets Act.
Plotters were employed on an early form of air traffic monitoring that played a vital role in World War II, including 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.
The AMES Type 7, also known as the Final GCI, was a ground-based radar system introduced during World War II by the Royal Air Force (RAF). The Type 7 was the first truly modern radar used by the Allies, providing a 360 degree view of the airspace around the station out to a distance of about 90 miles (140 km). It allowed fighter interceptions to be plotted directly from the radar display, a concept known as ground controlled intercept, or GCI.