Medieval stained glass is the coloured and painted glass of medieval Europe from the 10th century to the 16th century. For much of this period stained glass windows were the major pictorial art form, particularly in northern France, Germany and England, where windows tended to be larger than in southern Europe (in Italy, for example, frescos were more common).

Stained glass windows were used predominantly in churches, but were also found in wealthy domestic settings and public buildings such as town halls, though surviving examples of secular glass are very rare indeed.  The purpose of stained glass windows in a church was both to enhance the beauty of their setting and to inform the viewer through narrative or symbolism. The subject matter was generally religious in churches, though "portraits" and heraldry are often included, and many narrative scenes give valuable insights into the medieval world.
History

Early stained glass
Window glass was in use from at least the 1st century AD and colored and painted window glass for use in religious buildings was also manufactured at an early date. The earliest extant example of ecclesiastical stained glass is possibly that from San Vitale in Ravenna, Italy. A clear glass roundel with a depiction of Christ in Majesty, thought to be the 6th century, was discovered here.[1][2]
Some of the earliest known examples of colored window glass, datable to c. 800–820, were recovered in excavations at the Abbey of San Vicenzo in Volturno, Italy.[3] Glass of the same colour ranges and similar date is also found in England, at the monastic sites of Jarrow and Monkwearmouth, and at other sites in the north of England.[4][5] These examples are not painted. However, it was not until the advent of the monumental cathedral and church building campaigns in the 11th and 12th centuries that the demand for colored glass began to increase significantly, reaching its highest level in the 14th and 15th centuries. The oldest surviving stained glass windows still in situ are thought to be the Prophet Windows in Augsburg Cathedral, of c. 1065.
A useful 12th-century source on medieval glass manufacture is the De Divers Artibus of Theophilus Presbyter. Theophilus was a Benedictine Monk, believed by some scholars to be Roger of Helmarshausen, a metal glass and pigment worker who practiced in the late 11th and early 12th centuries.[6][7] De Divers Artibus describes a number of craft processes including glassmaking and glassworking.
In the 9th century, CE or earlier (books 1 and 2 of a 3-vol Mss. completed by another in the 12th, Eraclius, in De coloribus et artibus Romanorum, also gives an account of methods for producing colored glass, although he may have copied much of his text from the Naturalis Historia of Pliny the Elder of c. 77AD.[8] Now considered 'Inaccurate' date on works of Eraclius[9] Later in the medieval period  the son of Anthony of Pisa, artist and instructor Cennino Cennini, and, in 1556, Georgius Agricola[10] also contributed texts with aspects of glassmaking and glassworking.
Composition, manufacture and distribution
Prior to c. 1000, most coloured glass was of a soda-lime-silica composition. In Northern Europe soda glass was eventually almost totally superseded by potash-lime-silica glass (Forest glass). Forest glass continued to be used in stained glass for the duration of the medieval period[11] until soda glass again began to be used in the 16th century.
The potash (K2O) found in Forest Glass was derived from wood ash. In De Divers Artibus, Theophilus describes the use of beech wood as the preferred source of ash.[12] Other plant matter, such as bracken, was also used.[13] As well as containing potash, beech ash comprises an assortment of compounds including iron and manganese oxides, which are particularly important for generating colour in glass.
Medieval stained glass panels could be created either by the cylinder blown sheet or crown glass (window) method.
Forest glass was manufactured in Burgundy and Lorraine near the Rhein; in Flanders; and in Normandy, in the Seine and Loire Valleys. It was distributed throughout mainland north-west Europe and Britain in the form of ready-made sheets.[14] The application of painted decoration to and final shaping of the sheets was carried out at glass working centres close by the final destination of the glass.[15]
Colour

The colour of glass could be affected by many factors. Sources of silica were often impure, with iron oxide being one of the most common impurities. The greenish hue of uncoloured glass is usually owing to the presence of a mixture of ferrous (Fe2+) and ferric (Fe3+) ions in the glass matrix. It is also possible that ‘impurities’ could be introduced at the fritting stage within the glass furnace, leading to the addition of further alumina, silica and iron oxides.[16]
Inherent colour
Inherent colour refers to the colours that may be formed in the molten glass by manipulating the furnace environment. Theophilus describes molten glass changing to a ‘saffron yellow colour’ which will eventually transform to a reddish yellow on further heating, he also refers to a ‘tawny colour, like flesh’ which, upon further heating will become ‘a light purple’ and later ‘a reddish purple, and exquisite’.[17]
These colour changes are the result of the behaviour, under redox conditions, of the iron and manganese oxides which are naturally present in beech wood ash.
In the glass melt the iron and manganese behave as follows:
In an oxidising environment metal (and some non-metal) ions will lose electrons. In iron oxides, Fe2+ (ferrous) ions will become Fe3+ (ferric) ions. In molten glass this will result in a change in glass colour from pale blue to yellow/brown. In a reducing environment the iron will gain electrons and colour will change from yellow/brown to pale blue. Similarly manganese will change in colour depending on its oxidation state. The lower oxidation state of manganese (Mn2+) is yellow in common glass while the higher oxidation states (Mn3+ or higher) is purple. A combination of the two states will give a pink glass.
As the manganese and iron may each be in different states of oxidation, the combination of the two can result in a broad range of attractive colours. Manganese in its fully oxidised state, if not present in too great a mass, will also act as a decolourant of glass if the iron is in its yellow, ferric form. The two colours in effect cancel each other out to produce a clear glass.
Experimental manufacture of potash glass emulating Theophilus’ recipes has resulted in colours ranging from colourless to yellow, amber, brown, green, blue, pink and purple.[18][19][20] Variation in colour hue and depth would also probably be affected by the source of the beech wood ash, depending on the soil chemistry where the beech tree grew, the age of the tree and the climate conditions.[21][22]
Some of the stronger reds, blues and greens that are a feature of medieval stained glass rely on the addition of copper oxides.
Deliberately added colourants

Eraclius’ De Coloribus et Artibus includes instructions for creating green and red glass by adding copper (probably in the form of ore or copper filings) to the batch, a method practiced since ancient times.  (The chapters on how to make red, green and blue glass are missing from De Divers Artibus.)
As with the iron/manganese colours, the colours formed by the addition of copper oxide to the glass are dependent on the different oxidation states of the added copper. In an oxidising environment blue cupric (Cu2+) ions are formed, in a strongly reducing environment red colloidal cuprous (Cu1+) oxide is formed and if reoxidised then green cuprous (Cu1+) oxide results.
The production of bright reds and blues in particular was straightforward, as the addition of copper to the mix resulted in the reliable creation of red, blue and green. The dominance of red and blue in Romanesque and Gothic glass is obvious. However, at York Minster, for example, it was demonstrated that 90% of the medieval glass was coloured by means of iron/manganese content.[23]
Medieval blue soda glass
Early medieval glass was soda-based, and although the use of soda glass in Northern Europe was almost wholly superseded by forest glass after c. 1000, there are some examples of a richly coloured blue glass (identified through XRF analysis) that was produced in the medieval period using soda as the alkali.[24] In the UK, a considerable quantity of blue soda glass has been identified in stained glass from York Minster, and in excavations at Old Sarum and Winchester. In France, in Chartres Cathedral and St Denis in Paris, soda glass has also been found,[25] and no doubt there must be many other examples.
Evidence of recycling Roman tesserae to produce window glass in the 9th century has been identified at the Benedictine Monastery of San Vincenzo, Molise, Italy.[26] Theophilus, in the 12th century, was also aware of such practice. He states that mosaic tesserae: ‘little square stones’ from ‘ancient pagan buildings’ along with ‘various small vessels in the same colours’ could be used to produce glass: ‘they even melt the blue in their furnaces, adding a little of the clear white to it, and they make from it blue glass sheets which are costly and very useful in windows.’[27] According to Theophilus, the French were particularly skilled at this process.
Cox suggests that the examples analysed at York could indeed be ‘Roman, or slightly later, glass re-melted in France and imported into England’.[28]
Flashing
Glass comprising multiple layers of clear and (usually) red glass was known to exist in the 12th and 13th centuries. The manufacturing process is not known.[29] Flashing was developed in the 15th century, and refers to the superimposition of a thin layer of coloured glass onto another coloured or uncoloured glass sheet. The procedure may have involved dipping a small sphere of molten glass into a molten uncoloured glass and blowing this into a cylinder form (the cylinder blown sheet process) which was then cut into sections and flattened in an annealing oven.[30] Red, or ruby, copper-based glass, is usually flashed as the colour is too dense to be used alone. Other glass colours may also be flashed. These techniques could be remarkably sophisticated as demonstrated by 15thc. glass from the Carthusian Monastery of Pavia, where layered glasses of blue and violet; green and uncoloured; and red and uncoloured have been identified.[31]
Applied paint and silver stain

Paint
The paint applied to glass was a type of enamel, usually dark brown or black, formed from a mixture of: ground copper or iron oxide; powdered glass; wine, urine or vinegar; and gum arabic.[32] other recipes could include sugar, treacle or vegetable oil.[33] This ‘paint’ was applied in a series of washes, with fine details added last. Both the external and internal faces of the glass could be painted, adding depth to the overall composition. The enamel was fixed by ‘firing’ the glass in an annealing oven.
Silver stain
Producing a strong clear yellow could be difficult in early stained glass as it relied upon the careful control of furnace conditions in order to create the appropriate reducing or oxidising environment.[34] The introduction of silver stain in the early 14th century not only provided a solution to this difficulty, but also allowed greater flexibility in the way in which colour could be used. The first datable example of the use of silver stain is in the parish church of Le Mesnil-Villeman, Manche, France (1313).[35] Silver stain was a combination of silver nitrate or silver sulphide blended with pipe clay and applied to (usually) clear glass.[36]  This technique enabled a more flexible approach to glass painting, allowing, for example, the hair of a figure to be painted on the same piece of glass as the head. It was also used to highlight details of canopywork or grisaille, and later it was added to the surface of coloured glass, to create a wider variety of glass hues.[37]
See also
Stained glass
Stained glass conservation

Bibliography
Azzoni, C. B., Di Martino, D., Marchesi, V., Messiga. B., Riccardi, M. P., (2005). Colour Attributes of Medieval Window Panes: Electron Paramagnetic Resonance and Probe Microanalyses on Stained Glass Windows from Pavia Carthusian Monastery. Archaeometry 47/2, 381–388.
Cox, G. A., Gillies, K. J. S., 1986. The X-Ray Fluorescence Analysis of Medieval Durable Blue Soda Glass from York Minster. Archaeometry, 28/1, 57–68.
Cramp, R. J., 1975. Window Glass From the Monastic Site of Jarrow: Problems of Interpretation. Journal of Glass Studies, 17, 88–96.
Davison, S., 2003. Conservation and Restoration of Glass. Oxford: Butterworth-Heinemann.
Freestone, I. 1992. Theophilus and the Composition of Medieval Glass, Materials Issues in Art and Archaeology III, Pittsburgh, Pennsylvania: Materials Research Society, 739–745.
Hawthorne, J. G, Stanley Smith, C. (eds), 1979.Theophilus: On Divers Arts. New York: Dover.
Henderson, J. 1992. Early medieval glass technology: the calm before the storm. In S. Jennings and A. Vince (eds) Medieval Europe 1992: Volume 3 Technology and Innovation, 175–179.
Heyworth, M., 1992. Evidence for Early Medieval Glass Working. In S. Jennings and A. Vince (eds) Medieval Europe 1992: Volume 3 Technology and Innovation, 169–174.
Marks, R., 1993. Stained Glass in England During the Middle Ages. London: Routledge.
Newton, R., and Davison, S., 1997, Conservation of Glass, Butterworth–Heinemann, Oxford.
Royce-Roll, D., 1994. The Colors of Romanesque Stained Glass. Journal of Glass Studies,36, 71–80.
Smedley, J., W., Jackson, C. M., Booth, C.A., 1998. Back to the Roots: The Raw Materials, Glass Recipes and Glassmaking Practices of Theophilus. In: McCray, P. (ed). The Prehistory and History of Ancient Glassmaking, 145–165.
Stern, W. B., and Gerber, Y., 2004, Potassium-Calcium Glass: New Data and Experiments. Archaeometry 46/1, 137–156.
Further reading

What is the oldest surviving stained glass window?


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,[4] it is the oldest independent air force in the world.[5] Following victory over the Central Powers in 1918 the RAF emerged as, at the time, the largest air force in the world.[6] 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.[7]
The RAF's mission is to support the objectives of the British Ministry of Defence (MoD), which are to "provide the capabilities needed: to ensure the security and defence of the United Kingdom and overseas territories, including against terrorism; to support the Government’s foreign policy objectives particularly in promoting international peace and security".[3] The RAF describes its mission statement as "... [to provide] An agile, adaptable and capable Air Force that, person for person, is second to none, and that makes a decisive air power contribution in support of the UK Defence Mission".[8] The mission statement is supported by the RAF's definition of air power, which guides its strategy. Air power is defined as "the ability to project power from the air and space to influence the behaviour of people or the course of events".[9]
Today the Royal Air Force maintains an operational fleet of various types of aircraft,[10] described by the RAF as being "leading-edge" in terms of technology.[11] This largely consists of fixed-wing aircraft, including: fighter and strike aircraft, airborne early warning and control aircraft, ISTAR and SIGINT aircraft, aerial refueling aircraft and strategic and tactical transport aircraft. The majority of the RAF's rotary-wing aircraft form part of the tri-service Joint Helicopter Command in support of ground forces. Most of the RAF's aircraft and personnel are based in the UK, with many others serving on operations (principally over Iraq and Syria) or at long-established overseas bases (Ascension Island, Cyprus, Gibraltar, and the Falkland Islands). Although the RAF is the principal British air power arm, the Royal Navy's Fleet Air Arm and the British Army's Army Air Corps also deliver air power which is integrated into the maritime, littoral and land environments.
History

Origins
While the British were not the first to make use of heavier-than-air military aircraft, the RAF is the world's oldest independent air force: that is, the first air force to become independent of army or navy control.[5] Following publication of the "Smuts report" prepared by Jan Smuts[12] the RAF was founded on 1 April 1918, with headquarters located in the former Hotel Cecil, during the First World War, by the amalgamation of the Royal Flying Corps (RFC) and the Royal Naval Air Service (RNAS). At that time it was the largest air force in the world. After the war, the service was drastically cut and its inter-war years were relatively quiet, with the RAF taking responsibility for the control of Iraq and executing a number of minor actions in other parts of the British Empire. The RAF's naval aviation branch, the Fleet Air Arm, was founded in 1924 but handed over to Admiralty control on 24 May 1939.[13]
The RAF developed the doctrine of strategic bombing which led to the construction of long-range bombers and became its main bombing strategy in the Second World War.[14]
Second World War

The RAF underwent rapid expansion prior to and during the Second World War. Under the British Commonwealth Air Training Plan of December 1939, the air forces of British Commonwealth countries trained and formed "Article XV squadrons" for service with RAF formations. Many individual personnel from these countries, and exiles from occupied Europe, also served with RAF squadrons. By the end of the war the Royal Canadian Air Force had contributed more than 30 squadrons to serve in RAF formations, similarly, approximately a quarter of Bomber Command's personnel were Canadian.[15] Additionally, the Royal Australian Air Force represented around nine percent of all RAF personnel who served in the European and Mediterranean theatres.[16]

In the Battle of Britain in 1940, the RAF (supplemented by 2 Fleet Air Arm Squadrons, Polish, Czecho-Slovak and other multinational pilots and ground personnel) defended the skies over Britain against the numerically superior German Luftwaffe. In what is perhaps the most prolonged and complicated air campaign in history, the Battle of Britain contributed significantly to the delay and subsequent indefinite postponement of Hitler's plans for an invasion of the United Kingdom (Operation Sea Lion). In the House of Commons on 20 August, prompted by the ongoing efforts of the RAF, Prime Minister Winston Churchill eloquently made a speech to the nation, where he said "Never in the field of human conflict was so much owed by so many to so few".[17]
The largest RAF effort during the war was the strategic bombing campaign against Germany by Bomber Command. While RAF bombing of Germany began almost immediately upon the outbreak of war, under the leadership of Air Chief Marshal Harris, these attacks became increasingly devastating from 1942 onward as new technology and greater numbers of superior aircraft became available. The RAF adopted night-time area bombing on German cities such as Hamburg and Dresden, and developed precision bombing techniques for specific operations, such as the "Dambusters" raid by No. 617 Squadron,[18] or the Amiens prison raid known as Operation Jericho.[19]
Cold War era

Following victory in the Second World War, the RAF underwent significant re-organisation, as technological advances in air warfare saw the arrival of jet fighters and bombers. During the early stages of the Cold War, one of the first major operations undertaken by the Royal Air Force was in 1948 and the Berlin Airlift, codenamed Operation Plainfire. Between 26 June and the lifting of the Russian blockade of the city on 2 May, the RAF provided 17% of the total supplies delivered during the event, using Avro Yorks, Douglas Dakotas flying to Gatow Airport and Short Sunderlands flying to Lake Havel.[20]

Before Britain developed its own nuclear weapons the RAF was provided with American nuclear weapons under Project E. However following the development of its own arsenal, the British Government elected on 16 February 1960 to share the country's nuclear deterrent between the RAF and submarines of the Royal Navy, first deciding on 13 April to concentrate solely on the air force's V bomber fleet. These were initially armed with nuclear gravity bombs, later being equipped with the Blue Steel missile. Following the development of the Royal Navy's Polaris submarines, the strategic nuclear deterrent passed to the navy's submarines on 30 June 1969.[21] With the introduction of Polaris, the RAF's strategic nuclear role was reduced to a tactical one, using WE.177 gravity bombs. This tactical role was continued by the V bombers into the 1980s and until 1998 by Tornado GR1s.[22][23]

For much of the Cold War the primary role of the RAF was the defence of Western Europe against potential attack by the Soviet Union, with many squadrons based in West Germany. With the decline of the British Empire, global operations were scaled back, and RAF Far East Air Force was disbanded on 31 October 1971.[24] Despite this, the RAF fought in many battles in the Cold War period. In June 1948 the RAF commenced Operation Firedog against Malayan terrorists during the Malayan Emergency.[25] Operations continued for the next 12 years until 1960 with aircraft flying out of RAF Tengah and RAF Butterworth. The RAF played a minor role in the Korean War, with flying boats taking part.[26] From 1953 to 1956 the RAF Avro Lincoln squadrons carried out anti-Mau Mau operations in Kenya using its base at RAF Eastleigh.[27] The Suez Crisis in 1956 saw a large RAF role, with aircraft operating from RAF Akrotiri and RAF Nicosia on Cyprus and RAF Luqa and RAF Hal Far on Malta as part of Operation Musketeer.[28] The Konfrontasi against Indonesia in the early 1960s did see use of RAF aircraft, but due to a combination of deft diplomacy and selective ignoring of certain events by both sides, it never developed into a full-scale war.[29]
One of the largest actions undertaken by the RAF during the cold war was the air campaign during the 1982 Falklands War, in which the RAF operated alongside the Fleet Air Arm. During the war, RAF aircraft were deployed in the mid-Atlantic at RAF Ascension Island and a detachment from No. 1 Squadron was deployed with the Royal Navy, operating from the aircraft carrier HMS Hermes.[30][31] RAF pilots also flew missions using the Royal Navy's Sea Harriers in the air-to-air combat role.[32] Following a British victory, the RAF remained in the South Atlantic to provide air defence to the Falkland Islands, based at RAF Mount Pleasant (built 1984).[33]
Recent history
With the end of the Cold War and the collapse of the Soviet Union, the RAF's focus has returned to delivering expeditionary air power.[34] Since 1990 the RAF has been involved in several large-scale operations, including: the 1991 Gulf War,[35] the 1999 Kosovo War,[36] the 2001 War in Afghanistan,[37] the 2003 invasion and war in Iraq[38] and the 2011 intervention in Libya.[39]

The RAF's 90th anniversary was commemorated on 1 April 2008 by a flypast of 9 Red Arrows and four Typhoons along the Thames, in a straight line from just south of London City Airport Tower Bridge, the London Eye, the RAF Memorial and (at 13.00) the Ministry of Defence building.[40][41][42]
Four major defence reviews have been conducted since the end of the Cold War: the 1990 Options for Change, the 1998 Strategic Defence Review, the 2003 Delivering Security in a Changing World and the 2010 Strategic Defence and Security Review. All four defence reviews have resulted in steady reductions in manpower and numbers of aircraft, especially combat aircraft such as fast-jets. As part of the latest 2010 Strategic Defence and Security Review, the BAE Systems Nimrod MRA4 maritime patrol aircraft was cancelled due to over spending and missing deadlines.[43] Other reductions saw total RAF manpower reduced by 5,000 personnel to a trained strength of 33,000 and the early retirement of the Joint Force Harrier aircraft, the Harrier GR7/GR9.[44]

In recent years fighter aircraft on Quick Reaction Alert (QRA) have been increasingly required to scramble in response to efforts made by the Russian Air Force to approach British airspace.[46] On 24 January 2014 in the Houses of Parliament, Conservative MP and Minister of State for the Armed Forces, Andrew Robathan, announced that the RAF's QRA force had been scrambled almost thirty times in the last three years: eleven times during 2010, ten times during 2011 and eight times during 2012.[47]
RAF Coningsby in Lincolnshire and RAF Lossiemouth in Moray both provide Quick Reaction Alert, or QRA, and scramble their fighter jets within minutes to meet or intercept aircraft which give cause for concern. Lossiemouth generally covers the northern sector, while Coningsby provides QRA in the south. Typhoon pilot Flight Lieutenant Noel Rees describes how QRA duty works. "At the start of the scaled QRA response, civilian air traffic controllers might see on their screens an aircraft behaving erratically, not responding to their radio calls, or note that it’s transmitting a distress signal through its transponder.
Rather than scramble Typhoons at the first hint of something abnormal, a controller has the option to put them on a higher level of alert, ‘a call to cockpit’. In this scenario the pilot races to the hardened aircraft shelter and does everything short of starting his engines".[48]
On 4 October 2015, a final stand-down saw the end of more than 70 years of RAF Search and Rescue provision in the UK. The RAF and Royal Navy's Westland Sea King fleets, after over 30 years of service, were retired. A civilian contractor, Bristow Helicopters, took over responsibility for UK Search and Rescue, under a Private Finance Initiative with newly purchased Sikorsky S-92 and AgustaWestland AW189 aircraft. The new contract means that all UK SAR coverage is now provided by Bristow aircraft.[49]
In 2018 the RAF's vision of a future constellation of imagery satellites was initiated through the launch of the Carbonite-2 technology demonstrator. The 100kg Carbonite-2 uses commercial off-the-shelf (COTS) components to deliver high-quality imagery and 3D video footage from space.[50][51]
Structure

Royal Air Force
air component of the
British Armed Forces
Components
Royal Air Force
RAF Regiment
RAF Volunteer Reserve
RAF Medical Services
Nursing Service (PMRAFNS)
Royal Auxiliary Air Force
RAF Police
History
HistoryTimeline
Aircraft
List of RAF aircraft
Structure
Air Command
No. 1 Group
No. 2 Group
Joint Force Air Component
Headquarters (JFACHQ)
No. 11 Group
No. 22 Group
No. 38 Group
Stations
Personnel
Officer ranks
Other ranksvt
The professional head of the RAF is the Chief of the Air Staff (CAS).[52] The CAS heads the Air Force Board, which is a committee of the Defence Council. The Air Force Board is the management board of the RAF and consists of several high-ranking officers.[53]
Authority is delegated from the Air Force Board to the RAF's commands. While there were once individual commands responsible for bombers, fighters, training, etc., now only the Air Command exists, headquartered at RAF High Wycombe.[54] As this command is headed by the Chief of the Air Staff himself, it does not operate in way previous commands did with their own separate Air Officers Commanding and staff remote from Whitehall.[55]
Groups

Groups are the subdivisions of operational commands; these are responsible for certain types of operation or for operations in limited geographical areas:
No. 1 Group (Air Combat): controls the fast-jet force and the RAF's intelligence, surveillance, target acquisition, and reconnaissance (ISTAR) capabilities, as well as the following stations: RAF Coningsby, RAF Lossiemouth, RAF Marham, and RAF Waddington.[56]
No. 2 Group (Air Combat Support): controls the Air Mobility aircraft and the RAF's Force Protection assets as well as the following stations: RAF Benson, RAF Brize Norton, RAF Odiham and RAF Northolt.[57]
No. 11 Group (Multi-domain operations group): will lead air and space operations and command of the following air stations: RAF Boulmer, RAF Fylingdales, RAF Scampton, RAF Spadeadam.[58]
No. 22 Group (Training): responsible for the supply of qualified and skilled personnel, as well as the following stations: RAF College Cranwell, RAF Cosford, RAF Halton, RAF Linton-on-Ouse, RAF Shawbury, MOD St Athan, RAF St Mawgan and RAF Valley.[59]
No. 38 Group (Air Combat Service Support): responsible for engineering and logistics, communications and medical operations, as well as the following stations: RAF High Wycombe and RAF Wittering.[60]
No. 83 Group (Expeditionary Air): the RAF's operational headquarters in the Middle East, responsible for UK air operations in the Operations KIPION and SHADER Joint Operating Areas (JOAs) of some eight million square miles.[61]
Stations

An RAF station is ordinarily subordinate to a group; it is commanded by a group captain and it is sub-divided into administrative wings, each under a wing commander, as follows:[62]
Operations wing
Forward support wing
Depth support wing
Tactical imagery support wing
Base support wing
Wings

As well as administrative wings, the RAF has formed Expeditionary Air Wings (EAWs), each under a wing commander, to support operations; wings currently active are as follows:
No. 34 Expeditionary Air Wing, based at RAF Waddington: delivers ISTAR operations[63]
No. 38 Expeditionary Air Wing, based at RAF Brize Norton: delivers air transport operations[64]
No. 121 Expeditionary Air Wing based at RAF Coningsby: delivers multi role operations[65]
No. 135 Expeditionary Air Wing based at RAF Leeming: delivers fighter operations[65]
No. 138 Expeditionary Air Wing based at RAF Marham: delivers fighter operations[65]
No. 140 Expeditionary Air Wing based at RAF Lossiemouth: delivers fighter operations[65]
No. 901 Expeditionary Air Wing based in the middle east: delivers voice and data systems[66]
No. 902 Expeditionary Air Wing based in the middle east: delivers helicopter services[67]
No. 903 Expeditionary Air Wing based at RAF Akrotiri: delivers operations against ISIL[68]
No. 906 Expeditionary Air Wing based in the Middle East: delivers transport services[69]
Squadrons

A flying squadron is an aircraft unit which carries out the primary tasks of the RAF. RAF squadrons are somewhat analogous to the regiments of the British Army in that they have histories and traditions going back to their formation, regardless of where they are based, which aircraft they are operating, etc. They can be awarded standards and battle honours for meritorious service. Whilst every squadron is different, most flying squadrons are commanded by a wing commander and, for a fast-jet squadron, have an establishment of around 12 aircraft.[62]
Training Schools

The RAF Schools consist of the squadrons and support apparatus that train new aircrew to join front-line squadrons. The schools separate individual streams, but group together units with similar responsibility or that operate the same aircraft type.  Some schools operate with only one Squadron, and have an overall training throughput which is relatively small; some, like 3 FTS, have responsibility for all Elementary Flying Training (EFT) in the RAF, and all RAF aircrew will pass through its squadrons when they start their flying careers. 2 FTS and 6 FTS do not have a front-line training responsibility – their job is to group the University Air Squadrons and the Volunteer Gliding Squadrons together. 2 FTS's commanding officer holds the only full-time flying appointment for a Group Captain in the RAF, although he is a reservist.
Central Flying School – CFS standardises flying training across the air force and ensures standards and safety are maintained.[70]
No. 1 Flying Training School – Basic Fast Jet Training (BFJT), based at RAF Linton-on-Ouse[71]
No. 2 Flying Training School – Gliding training, based at RAF Syerston[72]
No. 3 Flying Training School – Elementary Flying Training, based at RAFC Cranwell with a squadron at RAF Wittering.[73]
No. 4 Flying Training School – Advanced Fast Jet Training (AFJT), based at RAF Valley[74]
No. 6 Flying Training School – Flight training for the University Air Squadrons, based at RAF stations throughout the UK[75]
The British military operate a number of joint training organisations based at RAF Stations:
Defence Elementary Flying Training School – Elementary Flying Training for Royal Navy and Army Air Corps students, based at RAF Barkston Heath[76]
Defence Helicopter Flying School – Basic helicopter training, based at RAF Shawbury.[77]
Defence College of Technical Training[78] – Several different specialist areas: aeronautical engineering, electro and mechanical engineering, and communication and information systems.[79]
Defence College of Aeronautical Engineering.[80] Comprising:
Royal Naval Air Engineering and Survival Equipment School.
DCAE (Lyneham)
No 1 School of Technical Training, Royal Air Force
Defence College of Electro-Mechanical Engineering.[81] Comprising:
Royal Naval School of Marine Engineering
8 Battalion Royal Electrical and Mechanical Engineers
No 4 School of Technical Training, Royal Air Force
Defence School of Communications and Information Systems.[82] Comprising:
11th (Royal School of Signals) Signal Regiment
No 1 Radio School, Royal Air Force
Defence School of Marine Engineering.
Flights

A flight is a sub-division of a squadron. Flying squadrons are often divided into two flights, e.g., "A" and "B", each under the command of a squadron leader. Administrative squadrons on a station are also divided into flights and these flights are commanded by a junior officer, often a flight lieutenant. Because of their small size, there are several flying units formed as flights rather than squadrons. For example, No. 1435 Flight is based at RAF Mount Pleasant in the Falkland Islands, maintaining air defence cover with four Eurofighter Typhoon aircraft.[83]
Personnel

At its height in 1944 during the Second World War, more than 1,100,000 personnel were serving in the RAF. The longest-lived founding member of the RAF was Henry Allingham, who died on 18 July 2009 aged 113.[84]
As of 1 January 2015, the Royal Air Force numbered some 34,200 Regular[85] and 1,940 Royal Auxiliary Air Force[86] personnel, giving a combined component strength of 36,140 personnel. In addition to the active elements of the Royal Air Force, (Regular and Royal Auxiliary Air Force), all ex-Regular personnel remain liable to be recalled for duty in a time of need, this is known as the Regular Reserve. In 2007 there were 33,980 Regular Reserves of the Royal Air Force, of which 7,950 served under a fixed-term reserve contract.[87] Publications since April 2013 no-longer report the entire strength of the Regular Reserve, instead they only give a figure for Regular Reserves who serve under a fixed-term reserve contract.[88] They had a strength of 7,120 personnel in 2014.[89]
Figures provided by the International Institute for Strategic Studies from 2012 showed that Royal Air Force pilots achieve a relatively high number of flying hours per year when compared with other major NATO allies such as France and Germany. RAF pilots achieve 210 to 290 flying hours per year.[90] French and German Air Force pilots achieved only 180 and 150 flying hours across their fleets respectively.[91]
Officers

Officers hold a commission from the Sovereign, which provides the legal authority for them to issue orders to subordinates. The commission of a regular officer is granted after successfully completing the 24-week-long Initial Officer Training course at the RAF College, Cranwell, Lincolnshire.[92]
To emphasize the merger of both military and naval aviation when the RAF was formed, many of the titles of officers were deliberately chosen to be of a naval character, such as flight lieutenant, wing commander, group captain, and air commodore.[93]
Other ranks

Other ranks attend the Recruit Training Squadron at RAF Halton for basic training.[94] The titles and insignia of other ranks in the RAF were based on that of the Army, with some alterations in terminology. Over the years, this structure has seen significant changes: for example, there was once a separate system for those in technical trades, and the ranks of chief technician and junior technician continue to be held only by personnel in technical trades. RAF other ranks fall into four categories: Warrant Officers, Senior Non-Commissioned Officers, Junior Non-Commissioned Officers and Airmen. All Warrant Officers in the RAF are equal in terms of rank, but the most senior Non-Commissioned appointment is known as the  Chief of the Air Staff's Warrant Officer.[95]
Specialist training and education
The Royal Air Force operates several units and centres for the provision of non-generic training and education. These include the Royal Air Force Leadership Centre and the Royal Air Force Centre for Air Power Studies, both based at RAF Cranwell,[96] and the Air Warfare Centre, based at RAF Waddington and RAF Cranwell.[97] NCO training and developmental courses occur at RAF Halton and officer courses occur at the Joint Services Command and Staff College at Shrivenham.[98]
Aircraft

Combat Air
Typhoon:
The Typhoon FGR4 is the RAF's primary multi role air defence and ground attack fighter aircraft, with a total of six squadrons based across RAF Coningsby and RAF Lossiemouth,[99][100] following the retirement of the Panavia Tornado F3 in late March 2011.[101] Their task is to defend UK airspace. In October 2007 it was announced that MoD Boscombe Down, RNAS Culdrose and RAF Marham would also be used as Quick Reaction Alert bases from early 2008, offering around-the-clock fighter coverage for the South and South West of UK airspace when a direct threat has been identified.[102]
The RAF has six front-line and one reserve Typhoon units;  3 (Fighter) Squadron, XI Squadron, 12(B) Squadron and 29 (Reserve) Squadron (Operational Conversion Unit) based at RAF Coningsby, with 1 (Fighter) Squadron, II (Army Cooperation) Squadron and 6 Squadron based at RAF Lossiemouth. On 23 November 2015 it was announced that two additional front-line Typhoon squadrons will be formed consisting of Tranche 1 versions.[99][103]

Typhoon FGR4

Tornado:
The mainstay of the strike fleet are the squadrons of Tornado GR4s.[104] These supersonic aircraft can carry a wide range of weaponry, including Storm Shadow cruise missiles, Brimstone missiles, Paveway IV laser-guided bombs and the ASRAAM missile.[105] Since June 2008, the Eurofighter Typhoon FGR4 has also been capable of being deployed operationally in the air-to-ground role.[106]
The RAF has only two operational Tornado units, with [107] IX (Bomber) Squadron and 31 Squadron based at RAF Marham. With the aircraft type nearing its retirement and replacement by the F-35, the RAF Lossiemouth-based 15 (Reserve) Squadron (the Tornado Operational Conversion Unit)[108] was disbanded in March 2017.[109]

Tornado GR4

Lightning:
On 23 November 2015 it was announced that a total of 138 F-35Bs will be ordered.[110][111][112]
617 (The Dambusters) Squadron officially reformed on 18 April 2018 as an RAF Lightning Squadron.[113] The first four aircraft arrived at RAF Marham in June 2018,[114] with a further five arriving in August 2018.[115] The planes were declared combat ready in January 2019.[116]

F-35B Lightning II

Intelligence, Surveillance, Target Acquisition, and Reconnaissance (ISTAR)
The Sentry AEW1, based at RAF Waddington, provides airborne early warning to detect incoming enemy aircraft and to co-ordinate the aerial battlefield.[117]
The Sentinel R1 (formally known as ASTOR – Airborne STand-Off Radar) provides a ground radar-surveillance platform based on the Bombardier Global Express long range business jet. These were supplemented in 2009 by four (a fifth was added later) Beechcraft Shadow R1 aircraft equipped for the ISTAR role over Afghanistan.[118] Three more Shadow aircraft will be procured as per the 2015 Defence Review. The Tornado GR4A is fitted with cameras and sensors in the visual, infra-red and radar ranges of the spectrum.[119]
Ten MQ-9A Reaper Unmanned aerial vehicles have been purchased to support operations in Iraq and Afghanistan. They are operated by No. 39 Squadron RAF based at Creech Air Force Base and 13 Squadron at RAF Waddington.[120]
Three RC-135W Rivet Joint replaced the Nimrod R1 fleet in the signals intelligence role under the AIRSEEKER Programme. The Nimrod fleet was retired in 2011, the RAF co-manned aircraft of the US Air Force until the three RC-135s entered service between 2014 and 2017.[121] The aircraft will be Boeing KC-135 Stratotanker tankers converted to RC-135W standard in the most complex combined Foreign Military Sales case and co-operative support arrangement that the UK has undertaken with the United States Air Force since the Second World War.[122] Airseeker received its first operational deployment in August 2014, when it was deployed to the Middle East to fly missions over Iraq and Syria as part of Operation Shader.[123]

Sentry AEW1
Sentinel R1
Airseeker R1
Shadow R1
MQ-9A Reaper

Helicopters
An important part of the work of the RAF is to support the British Army by ferrying troops and equipment at the battlefield. However, RAF helicopters are also used in a variety of other roles, including support of RAF ground units and heavy-lift support for the Royal Marines. The support helicopters are organised into the tri-service Joint Helicopter Command (JHC), along with helicopters of the British Army and Royal Navy.[124]
The large twin-rotor Chinook, based at RAF Odiham provides heavy-lift support[125] and is supported by the Puma HC2 medium-lift helicopter based at RAF Benson.[126] The Griffin HAR.2s based at RAF Akrotiri in the Cyprus Sovereign Base Areas, the only remaining dedicated helicopter Search and Rescue force in the RAF.[127] However, all UK military helicopter aircrew routinely train and practice the skills necessary for Search and Rescue, and the support helicopters based in the UK are available to the Government under Military Aid to the Civil Authorities in case they are needed. The AW109 Grand New aircraft of 32 (the Royal) Squadron also provide VIP transport and military helicopter capabilities.[128]

Chinook HC2
Puma HC2
Bell Griffin HAR2

Air Mobility

The RAF operate the Boeing C-17 Globemaster III in the heavy strategic airlift role, originally leasing four from Boeing. These were purchased, followed by a fifth delivered on 7 April 2008 and a sixth delivered on 8 June 2008. The new aircraft entered frontline use within days rather than weeks. The MoD said there was "a stated departmental requirement for eight" C-17s and a seventh was subsequently ordered, to be delivered in December 2010.[129] In February 2012 the purchase of an eighth C-17 was confirmed;[130] the aircraft arrived at RAF Brize Norton in May 2012.[131]
More routine strategic airlift transport tasks are carried out by the  Airbus A330 MRTT, known as the Voyager in RAF service. The first Voyager arrived in the UK for testing at MoD Boscombe Down in April 2011,[132] and entered service in April 2012.[133] The Voyager received approval from the MoD on 16 May 2013 to begin air-to-air refuelling flights and made its first operational tanker flight on 20 May 2013 as part of a training sortie with Tornado GR4s. By 21 May 2013, the Voyager fleet had carried over 50,000 passengers and carried over 3,000 tons of cargo.[134] A total of 14 Voyagers are due to form the fleet, with 9 allocated to sole RAF use. As the Voyagers lack a refueling boom, the RAF has requested a memorandum of understanding (MoU) with the USAF allowing the UK access to tankers equipped with refueling booms for its Boeing RC-135W Airseeker SIGINT aircraft.[135]
Shorter range, tactical-airlift transport is provided by the Lockheed Martin C-130J Hercules, known as Hercules C4 and C5 in RAF service and based at RAF Brize Norton in Oxfordshire. The draw-down of the Hercules C5 fleet has begun with the final aircraft planned to retire in 2019.The fourteen C4 extended variants are scheduled to retire on 31 March 2035. The Airbus A400M Atlas replaced the RAF's fleet of Hercules C1/C3 (C-130K) transport aircraft which were withdrawn from service on 31 December 2012 and will also replace the C4/C5 variants. Originally, 25 aircraft were ordered, although the total is now 22.[136][137]
No. 32 (The Royal) Squadron replaced the Queen's Flight in 1995 and operate the Agusta A109 and BAe 146 CC2 in the general air transport and VIP transport roles. The squadron is based at RAF Northolt in west London. Aircraft operate with a priority for military needs over VIP transport. Two additional BAe 146s were purchased in March 2012 from TNT Airways and were refitted by Hawker Beechcraft on behalf of BAE Systems for tactical freight and personnel transport use.[138][139] The aircraft, designated as the BAe 146 C Mk 3, arrived in Afghanistan in April 2013.[140]

C-17A Globemaster III
Atlas C1 (A400M)
Hercules C5 (C-130J)
Voyager KC3 (A330 MRTT)
BAe 146 CC2
BAe 146 C3

Training aircraft
Elementary Flying Training, as well as Multi-Engine Lead-In training, is conducted on the Tutor T1. Basic fast jet training is provided on the Tucano T1 and initial helicopter training on the Squirrel HT1, at which stage aircrew gain their 'wings'. Multi-Engine aircrew, weapon systems officer (WSO) and weapon systems operator (WSOp) students are trained on the King Air to gain their wings before a posting to an Operational Conversion Unit. Advanced jet flying training is now provided on Hawk T2 for fast jet aircrew and helicopter pilots complete a course on the Griffin HT1, before they are sent to their OCU, which trains them on a specific aircraft type in preparation for service with a front-line squadron. The OCUs use modified operational aircraft, such as the Typhoon T3, as well as sophisticated simulators and ground training.[141]
The Tutor equips the fourteen University Air Squadrons, which provide University students an opportunity to undertake an RAF training syllabus based loosely on EFT to get them to and beyond solo standard. These units are co-located with Air Experience Flights, which share the same aircraft and facilities and provide air experience flying to the Air Training Corps and CCF. The Volunteer Gliding Squadrons also provide air experience flying to cadets using the Viking TX1 conventional glider. Due to an airworthiness issue in April 2014, the Viking fleet and the Vigilant T1 aircraft were grounded for a two-year period, although Viking operations have subsequently resumed.[142] The Vigilant was unexpectedly withdrawn from service in May 2018, a year earlier than planned. A contract tender was initiated in February 2018 to replace this capability starting in 2022.[143]
Two of the ten T-6 Texan II trainers due as part of the UK Military Flight Training System were delivered in February 2018, forming the nucleus of the unit to be operated at RAF Valley.  The aircraft are jointly operated by the Royal Air Force and Ascent Flight Training to provide lead-in training for RAF and Royal Navy fighter pilots prior to advanced training on the Hawk.[144]
100 Squadron operates the Hawk T1 to support other fast jets and in support of ground unit training, as an aggressor aircraft. The Squadron fulfils the role of enemy aircraft in air combat training or to provide more assets in joint exercises.[145]

Tutor T1
Tucano T1
Hawk T1
King Air T1
Viking T1

Future aircraft

The F-35B Lightning II is intended to enter service around 2020 under the Joint Combat Aircraft programme.[146] On 19 July 2012 the Defence Secretary, Philip Hammond, in a speech in the US, indicated that the UK would initially receive 48 F-35B to equip the Navy's carrier fleet and would announce at a later date what the final numbers would be. Jon Thompson, MOD Permanent Secretary, told the House of Commons Defence Select Committee, in late 2012: "Our commitment over the first 10 years is for 48 F-35B". An order for the first 14 aircraft on top of the four already procured for operational test and evaluation is expected later in 2013. The first four of 14 production aircraft were ordered in November 2014.[147]  Six further aircraft were ordered on 3 November 2015,[147] with expected delivery in 2016. In November 2015, the government commitment to order 48 F-35B aircraft by 2023,[148] 24 of which will be available for carrier duties.[149] The 2015 Strategic Defence and Security Review stated the intent for the UK to purchase 138 F-35 aircraft over the life of the programme.[149] The first F-35 aircraft arrived at RAF Fairford in Gloucestershire on 29 June 2016 after a Transatlantic crossing involving air to air refuelling.[150]
On 5 October 2015, it was announced that the Scavenger programme had been replaced by "Protector", a new requirement for at least 20 systems.[151] On 7 October 2015, it was revealed that Protector will be a Certifiable derivative of the MQ-9B SkyGuardian with enhanced range and endurance.[152] In July 2018, a General Atomics US Civil registered MQ-9B SkyGuardian was flown from North Dakota to RAF Fairford for the Royal International Air Tattoo where it was given RAF markings. It was formally announced by the Chief of Air Staff that No. 31 Squadron RAF would become the 1st Sqn to operate the Protector RG1.[153][154][155]
In July 2014 the House of Common Defence Select Committee released a report on the RAF future force structure that envisaged a mixture of unmanned and manned platforms, including further F-35, Protector RG1, a service life extension for the Typhoon (which would otherwise end its service in 2030) or a possible new manned aircraft.[156]
In November 2015, the Government confirmed in its Strategic Defence and Security Review that nine Boeing P-8 Poseidon aircraft will be purchased for surveillance, anti-submarine and anti-surface ship warfare, filling a capability gap in maritime patrol that had been left since the cancellation of the Nimrod MRA4 programme in the 2010 SDSR.[157]
In July 2018 at the Farnborough Airshow, the Defence Secretary announced a £2bn investment for BAe Systems, MBDA and Leonardo to develop a new British 6th Generation Fighter to replace Typhoon in 2035 under Project TEMPEST.[158]

Boeing P-8 Poseidon
F-35 Lightning II

UK Military Flying Training System

The UK's military flying training has been civilianised through a public-private partnership, which puts training output in the hands of a civilian contractor, known as Ascent Flight Training, a consortium of Lockheed Martin and Babcock International. The main elements of the system are fixed- and rotary-wing training from ab-initio all the way to Operational Conversion Units, which prepare aircrew for a specific frontline platform.[159]
Fixed wing
The new process uses three new fixed wing aircraft, the Grob 'Prefect' elementary trainer, the Beechcraft T-6 Texan II basic fast jet trainer, and the Embraer Phenom 100 multi-engine trainer. The aircraft have been procured to reduce the training gap between the older generation Tutor T1, Tucano T1 and King Air T1 aircraft, and the RAF's modern frontline aircraft, including advanced systems and glass cockpits. MFTS also relies far more on synthetic training to deliver aircrew to the front line, where advanced synthetic training is commonplace. Basic Fast Jet training is undertaken on the Texan, and advanced training is done on the BAE Systems Hawk T2, the contract for which had been separated from the rest of the UK MFTS contract, under the auspices of the Advanced Fast Jet Trainer programme.[160]

Prefect T1
Texan T1
BAE Hawk T2
Phenom T1

Rotary
In May 2016, it was announced that the RAF would see delivery of 29 Airbus H135 and 3 Airbus H145 helicopters for use as training aircraft. It was announced by Air Marshal Sean Reynolds, the Senior Responsible Owner for UKMFTS, that "Aircrew across the three Services will continue to conduct their basic and advanced rotary training at RAF Shawbury and Army Air Corps Middle Wallop. Aircrew selected for training in mountain and maritime helicopter operations will receive instruction at RAF Valley".[161]
Symbols, flags, emblems and uniform

Following the tradition of the other British fighting services, the RAF has adopted symbols to represent it, use as rallying devices for members and promote esprit de corps. British aircraft in the early stages of the First World War carried the Union Flag as an identifying feature; however, this was easily confused with Germany's Iron Cross motif. In October 1914, therefore, the French system of three concentric rings was adopted, with the colours reversed to a red disc surrounded by a white ring and an outer blue ring.[162] The relative sizes of the rings have changed over the years and during World War II an outer yellow ring was added to the fuselage roundel. Aircraft serving in the Far East during World War II had the  to prevent  with Japanese aircraft.[163] Since the 1970s, camouflaged aircraft carry low-visibility roundels, either red and blue on dark camouflage, or washed-out pink and light blue on light colours. Most uncamouflaged training and transport aircraft retain the traditional red-white-blue roundel.[163]
The Latin motto of the RAF, "Per Ardua ad Astra", is usually translated as "Through Adversity to the Stars",[164] but the RAF's official translation is "Through Struggle to the Stars".[3] The choice of motto is attributed to a junior officer named J S Yule, in response to a request from a commander of the RFC, Colonel Sykes, for suggestions.[165]
The Badge of the Royal Air Force was first used in August 1918. In heraldic terms it is: "In front of a circle inscribed with the motto Per Ardua Ad Astra and ensigned by the Imperial Crown an eagle volant and affronte Head lowered and to the sinister".[164] Although there have been debates among airmen over the years whether the bird was originally meant to be an albatross or an eagle, the consensus is that it was always an eagle.[166]
Ceremonial functions and display
Red Arrows

The Red Arrows, officially known as the Royal Air Force Aerobatic Team, is the aerobatics display team of the Royal Air Force based at RAF Scampton, with under-review plans to move to RAF Waddington. The team was formed in late 1964 as an all-RAF team, replacing a number of unofficial teams that had been sponsored by RAF commands.[167] The Red Arrows badge shows the aircraft in their trademark Diamond Nine formation, with the motto Éclat, a French word meaning "brilliance" or "excellence".[167]
Initially, they were equipped with seven Folland Gnat trainers inherited from the RAF Yellowjacks display team. This aircraft was chosen because it was less expensive to operate than front-line fighters. In their first season, they flew at 65 shows across Europe. In 1966, the team was increased to nine members, enabling them to develop their Diamond Nine formation. In late 1979, they switched to the BAE Hawk trainer. The Red Arrows have performed over 4,700 displays in 56 countries worldwide.[168]
Royal Air Force Music

Headquarters Royal Air Force Music Services, located at RAF Northolt, supports professional musicians who attend events around the globe in support of the RAF. The Central Band of the Royal Air Force was established in 1920.[169] Other bands include the Band of the Royal Air Force College, the Band of the Royal Air Force Regiment and the Band of the Royal Auxiliary Air Force.[170]
Current deployments

See also

Royal Air Force Museum
Royal Auxiliary Air Force
Royal Air Force Air Cadets
List of military aircraft operational during World War II
List of Royal Air Force stations
RAF News
Footnotes

Bibliography
Biddle,  Tami Davis. Rhetoric and Reality in Air Warfare: The Evolution of British and American Ideas about Strategic Bombing, 1914–1945 (2002)
Bowyer, Chaz. History of the RAF (London: Hamlyn, 1977).
Dean, Maurice. The Royal Air Force and Two World Wars (Cassell, 1979).
Connolly, Corvin J. Marshal of the Royal Air Force Sir John Cotesworth Slessor and the Anglo-American Air Power Alliance, 1940-1945 (Texas A&M Press, 2001).
Cox, Jafna L. "A splendid training ground: the importance to the Royal Air Force of its role in Iraq, 1919–32." Journal of Imperial and Commonwealth History 13.2 (1985): 157-184.
Davis, Richard B. Bombing the European Axis Powers. A Historical Digest of the Combined Bomber Offensive 1939-1945 (Air University Press,  2006)
Gooderson, Ian. Air Power at the Battlefront: Allied Close Air Support in Europe 1943-45  (Routledge, 2013).
Heaton, Colin D., and Anne-Marie Lewis. Night Fighters: Luftwaffe and RAF Air Combat Over Europe, 1939-1945 (Naval Institute Press, 2008).
Hoffman, Bruce. British Air Power in Peripheral Conflict, 1919-1976 (RAND, 1989)  , with bibliography
CS1 maint: extra text: authors list (link)
CS1 maint: extra text: authors list (link)
Lee, David. Eastward: a history of the Royal Air Force in the Far East, 1945-1972 (Seven Hills Books, 1984).
Lee, David. Flight from the Middle East: A History of the Royal Air Force in the Arabian Peninsula and Adjacent Territories, 1945-1972 (HM Stationery Office, 1980).
Maiolo, Joseph. Cry Havoc: How the arms race drove the world to war, 1931-1941 (2010)
Philpott, Ian, ed. Royal Air Force History: Royal Air Force - an Encyclopaedia of the Inter-War Years (2 vol 2008)
Rawlings, John D.R. The History of the Royal Air Force (1984) well illustrated.
Richards, Denis, and David Pilgrim. Royal Air Force, 1939-1945: The fight at odds (1954), the official history.

Saunders, Hilary. Per Ardua: The Rise of British Air Power, 1911-1939 (Oxford UP, 1945).
Sinnott, Colin S. The RAF and Aircraft Design: Air Staff Operational Requirements 1923-1939 (Routledge, 2014).
Smith, Malcolm. British Air Strategy Between the Wars (Oxford, The Clarendon Press, 1984).
Werrell, Kenneth P. "The strategic bombing of Germany in World War II: Costs and accomplishments." Journal of American History 73.3 (1986): 702-713.

What is the purpose of the Royal Air Force?


Leucine rich repeat and Immunoglobin-like domain-containing protein 1[1] also known as LINGO-1 is a protein which is encoded by the LINGO1 gene in humans.[2][3] It belongs to the family of leucine-rich repeat proteins which are known for playing key roles[4] in the biology of the central nervous system. LINGO-1 is a functional component of the Nogo (neurite outgrowth inhibitor) receptor also known as the reticulon 4 receptor.
It has been found that LINGO-1 antagonists such as BIIB033[5] could significantly improve and regulate survival after neural injury caused by the protein.[6]
Structure

The human LINGO-1 is a single-pass type 1 transmembrane protein of 614 amino acids. It contains a signal sequence of 34 residues, followed by a LRR (leucine-rich repeat) domain, an Ig (immunoglobulin-like) domain, a stalk domain, a transmembrane region and a short cytoplasmic tail. As a transmembrane protein, it can mostly be found on the cell membrane.[7]
The LINGO-1 structure has been shown to be highly stable both in its crystal form and in solution, thanks to its leucine-rich repeat Ig-composite fold. Since the tetramer has a very large surface area into the cell membrane, it is thought that this may serve as an efficient and stable binding platform, facilitating the interaction with NgR, p75, TROY complex.

Extracellular domain
The extracellular domain consists of the signal sequence, 11 LRR motifs comprised between an N-terminal and  C-terminal capping domains, and the Immunoglobulin-like (IgC2) domain.[3][8] The C-terminal LRR domain is essential for the protein's function with its screening for proteins that interact with this domain. The structure, together with biophysical analysis of LINGO-1 properties have revealed that the protein's LRR-Ig composite fold of the protein can drive it to associate with itself in a circular ring-like form, creating a closed and stable tetramer in solution and in crystal.
Intracellular domain
The intracellular part of the protein is formed by the transmembrane region and a cytoplasmic tail of 38 residues. It contains a canonical Epidermal Growth Factor Receptor (EGFR)-like tyrosine phosphorylation site on the 591 residue that is critical for intracellular signals.[9]
Co-receptor
LINGO-1 is a co-receptor that interacts with the ligand-binding Nogo-66 receptor (NogoR) in the Nogo receptor signaling complex.[8] The Nogo receptor complex is formed when Nogo-66 binds to its receptor.[10]
LINGO-1 is an homotetramer which forms a ternary complex with RTN4R/NGFR and RTN4R/TNFRSF19.
Post-translational modifications
LINGO-1 contains several N-glycosylation sites that could have a negative effect on its capacity to self-interact with cis or trans, with other partners, or gangliosides.[11] It also contains high-mannose glycans.
Tissue distribution

LINGO-1 is expressed almost exclusively in the central nervous system (CNS). It can be found in the brain and in neurons and oligodendrocytes. LINGO-1 mRNA is expressed in an almost exclusive manner in the central nervous system during both embryonic and postnatal stages. It is targeted to the plasma membrane of neurons, but it is possible that a smaller quantities of the protein may be found in other intracellular compartments.[12] Its highest expression is in specific adult human brain regions such as the cerebral cortex, a region involved in sensory-motor function, cognition and working memory; the hippocampus, responsible for long term memory and the encoding and retrieval of multi-sensory information; the amygdala, implicated in the stress response; as well as the thalamus, with a more constant and basal level of expression across the remainder of the brain.[13]
Function and mode of action
Since LINGO-1 is a leucine-rich repeat protein, which are known for their important role in protein-protein interactions in a wide variety of cellular processes and their implication in important functions like neuronal differentiation and growth or the regulation of axon guidance and regeneration processes, it is logical to deduce that its functions are linked with the nervous system.
LINGO-1 is an essential negative regulator of myelination. It has been implicated in the inhibition of axon regeneration through a ternary complex formed with NgR1/Nogo-66 (ligand-binding subunit) and p75 (signal transducing subunit). NgR1 relies on its co-receptors for transmembrane signalling.The three major myelin-associated inhibitory factors are Nogo, oligodendrocyte myelin glycoprotein, and myelin-associated glycoprotein which all share this trimolecular receptor complex. The inhibitory action is achieved through RhoA-GTP upregulation in response to the presence of MOG, MAG or Nogo-66 in the central nervous system.[8]  LINGO-1 also inhibits oligodendrocyte precursor differentiation and myelination, by a mechanism that also involves activation of RhoA, but which apparently does not require p75 or NgR1.
LINGO-1 is involved in the regulation of neural apoptosis by inhibiting WNK3 kinase activity. It has been shown that blocking the extracellular domain of LINGO-1 disrupts the interaction between receptor kinases and LINGO-1 which directly attenuates inhibition of neuronal survival. However among the four WNK family members, only WNK3 has been shown to regulate and increase cell survival in a caspase-3-dependant pathway.[11][14]
To be able to understand how these components regulate signalling processes an experiment has been set up "model of serum deprivation" (SD) to prompt neuronal apoptosis. Research shows that treatments either with a construct containing the IgC2 or EGFR domains in the LINGO1 protein or with Nogo66 which act like a NgR1 agonist, therefore initiating a physiological response when combined with the receptor, resulting in an increased rate of apoptosis in primary cultured cortical neurons under SD.
In addition, reducing the expression levels of the serine/threonine Kinase WNK3 (using gene silencing via RNA interference (ShRNA)) or inhibiting its kinase activity had similar effects on the survival of such neurons. The adverse effects of Nogo66[15] have proved to enhance the co-association of LINGO1 and WNK3, causing the binding of WNK3 to the intracellular domain of LINGO1 leading to reduced WNK3 kinase activity. LINGO1 promotes neural apoptosis by inhibiting WNK3 kinase activity.[16]
Signaling pathways
LINGO-1 is able to interact with different co-factors and co-receptors, which can lead to the activation o signaling pathways that can have an effect on the regulation of neuronal survival, axon regeneration, oligodendrocyte differentiation, or myelination processes in the brain.[17]
Known interactions are with proteins such as Oligodendrocyte-myelinn glycoprotein, Nogo-A (neurotic outgrowth inhibitor), and myelin associated glycoproteins. LINGO-1 also interacts with transmembrane proteins: EFGR, along with its ligand epidermal growth factor (EFG); brain derived neurotrophic factor (BNDF) and its receptor, amyloid precursor protein (APP), and tropomyosin receptor kinase A (TrkA). There are other interactions with proteins that are implicated in neurological and psychiatric disorders: WNK lysine deficient protein in kinase 1 (WNK1), mitogen activated protein kinase 2/3 (MEK 2/3), extracellular signal reduced kinase 5 (ERK5), RhoA, and others.[18]
Neurological and psychiatric disorders

LINGO-1 is coded by the LINGO-1 gene, which is located on the human chromosome 15, more precisely on the locus 15q24-26, which is a region that has a primordial implication in number of psychiatric, addictive and anxiety related disorders. Genomic alterations of this regions can be factors for disorders such as schizophrenia, depression, autism, panic disorder or anxiety.[19]
Brain regions identified as highly expressing Lingo-1 transcripts have also been heavily implicated in both neurological and psychiatric disorders such as spinal cord injury, traumatic brain injury, multiple sclerosis (MS), Parkinson’s disease, essential tremor (ET), Alzheimer’s disease, epilepsy and glaucoma (central nervous system diseases); as well as stress and panic disorders, schizophrenia, amnesia, etc.[13] The role of Lingo-1 in these neurological disorders consists on its inhibitory role in neurite outgrowth, oligodendrocyte differentiation and myelination, making it difficult for the nervous system to regenerate the injured areas, whether these injuries come from endogenous or exogenous processes.
Spinal cord injury
Spinal cord injury results in the damage of the axonal tracts whose function is to control motor and sensory activity. This protein has been found in this axonal tracts of adolescent rat spinal cords following injury. Furthermore, a five time increase in Lingo-1 mRNA levels was detected 14 days post injury. Lingo-1-Fc, a soluble form of Lingo-1, has also been shown to antagonize Lingo-1 signaling pathways by inhibiting the binding of Lingo-1 to NgR, in consequence, vast improvements in the functional recovery of rats following lateral hemisection of the spinal cord were observed.[13]
Essential tremor and Parkinson
Essential tremor, one of the most common neurological diseases, is characterized by postural and action tremor. Recent research shows that around the 20% of people who suffer this disease have an increase of the protein LINGO1 in their cerebellum, therefore linking LINGO1 to essential tremor would result in the development of more effective symptomatic therapies and treatment.[20][21][22]
It has been found that there is a marker in LINGO-1 genome, a variant (rs9652490) that is significantly associated with essential tremor, increasing the risk of having the pathology.
As for Parkinson's disease, which is also an age-related movement disorder, it was discovers that levels of LINGO-1 are more elevated in the substantia nigra of post-mortem Parkinson's disease brains compared to control groups. It is thought that dopamine neuron survival and behavioral abnormalities are due to the over expression of LINGO-1 in Parkinson's patients.[13]
Traumatic brain injury
Traumatic brain injury involves the necrotic and apoptotic death of brain cells in vulnerable and delicate areas such as the cerebral cortex and hippocampus, where it is known that there is an expression of Lingo-1 in both development and the adult stage of life. RhoA signaling is largely responsible for the neuronal response to neuronal inhibitory proteins and the regeneration (or lack of in case of its activation) of damaged axons. Receptor Lingo-1 stimulates RhoA, which activates ROCK (RhoA kinase) which, in turn, stimulates LIM kinase, which then stimulates cofilin, which effectively reorganizes the actin cytoskeleton of the cell. In the case of neurons, activation of this pathway results in growth cone collapse, therefore inhibits the growth and repair of neural pathways and axons. Inhibition of this pathway by its various components usually results in some level of improved re-myelination.[23] The use of Lingo-1-Fc as an antagonist for Lingo-1 shows the inhibition of RhoA activation. Since this soluble form of Lingo-1 is able to block the interactions between Lingo-1 and NgR, it is reasonable to think that the blockade of RhoA occurs at the level of Lingo-1/NgR/p75 or TROY complex, leading to the conclusion that Lingo-1plays a very important part in the lack of re-myelination, repair of neural and axon injuries, etc.[13]
Schizophrenia
Schizophrenia is a chronic, severe and disabling brain disorder.
As said before, leucine-rich repeat and immunoglobulin domain-containing protein (Lingo-1) is an essential negative regulator of myelination and neurite extension. Both myelination and neurite outgrowth occur during brain maturation, and it is during this late period of brain development (adolescence and early adulthood) when schizophrenia is first expressed. In fact, myelination peaks during late adolescence, coinciding with the onset of schizophrenia. Consequently, an excessive action of Lingo-1 through demyelination and blocking neurite extension may be one of the possible causes of this disorder.
The brain regions which are highly disrupted in the pathophysiology of this disease are hippocampus and dorsolateral prefrontal cortex. Therefore, clinical studies have been developed in order to study these brain regions in people who suffer schizophrenia. To investigate the hypothesis that myelin fraction is lower in schizophrenia patients than in healthy subjects, a technique called magnetic resonance spectroscopy (MRS), which allows analysis of myelin, is used. This studies reported that there was in fact, a dysfunctional profile of myelination in these two areas of the brain in schizophrenia sufferers.[24]
Post-mortem studies were then realized in order to compare the levels of the protein Lingo-1 in these two brain regions (hippocampus and dorsolateral prefrontal cortex) between schizophrenia and healthy subjects. Effectively, it was shown that the levels of Lingo-1 where significantly higher in schizophrenia than in control groups.[25]
Taking this into account, there is a clear relationship in between schizophrenia and demyelination, therefore, this disease is linked with Lingo-1 protein. Very possibly, an effective treatment of this disease would be the use of Lingo-1 antagonists, such as Anti-Lingo-1, which would offset the lack of myelin and hopefully avoid the disease. Thus, this treatment is still in ways of development and research.[26]
Multiple sclerosis
Multiple sclerosis is among the most common neurological disorders in young adults and it consists in the destructions and damage of the central nervous system (CNS) myelin due to persistent inflammation in the brain and spinal cord. This demyelination is shown to cause mitochondrial dysfunction in axons, leading to their degeneration. These damages disrupt the ability and capacity of the CNS to communicate, causing, therefore, a wide range of symptoms including physical, mental and even psychiatric ones. The best way of re-myelination is encouraging the differentiation of endogenous adult precursor cells into mature oligodendrocytes in the injured regions. These precursor cells are called oligodendrocyte precursor cells (OPCs). It is known that in early stages of MS re-myelination can be achieved successfully and efficiently whereas it cannot in late and progressive stages. Regarding Lingo-1, we know that its signaling pathway is a negative regulator of OPCs differentiation, as well as Notch's and Wnt's.
Lingo-1 antagonists are able to promote re-myelination in CNS by means of stimulating OPCs differentiation which was before blocked by this protein. This has been seen in several experiments that resulted in significant increases of oligodendrocytes differentiation by targeting Lingo-1 with its antagonists, such as the antibody Anti-LINGO-1 (BIIB033).[27]
Glaucoma
Glaucoma is a group neurodegenerative diseases characterized by features including morphological changes in the optic nerve head and therefore in the visual fields of the patients. There are two main types; open-angle and closed-angle glaucoma. The loss of RGCs (retinal ganglion cells) and their axons  results in visual field loss.Increasing evidence also supports the existence of compartmentalized degeneration in synapses. It has been shown that the first symptoms of this disease are usually ocular hypertension. Elevated IOP (intraocular pressure) has been identified as the etiology of glaucoma which causes neural RCG degeneration in the retina.[28]
LINGO1  was found to be expressed in the normal retina and was up regulated in RCGs after the induction of ocular hypertension in a rat chronic glaucoma model. Hence LINGO1 functions as a negative regulator of neuronal survival, axonal regeneration and oligodendrocyte differentiation. LINGO1 binds with TrkA and inhibits myelination by oligodendrocytes in vitro. Further more it binds to BDNF receptor and TrkB inhibiting the activation of TkrB by binding of BNDF after the induction of ocular hypertension.
Neuroprotection of RCGs
Even though BDNF is an important survival factor for RGCs both during development and adult life,  BDNF can only slightly increase the survival rate of RCGs,[28] and does not significantly “rescue” injured RCGs in hypertensive eyes after episcleral vein cauterization. The negative regulatory function of LINGO1 may be involved in the limited neuroprotective effect of BDNF and it could be reversed after blocking LINGO1 function.
LINGO 1 negatively regulates TrkB activation through the signalling pathway of BDNF/TrKB, and anti-LINGO-1 exerts neuroprotective effects via activation of BDNF/TrkB.[29][30]
Better than BDNF and BII003 (LINGO1 antagonist) alone, the combined treatment of both provides long term RCG neuroprotection after the induction of ocular hypertension. In conclusion BII033 may provide an attractive therapeutic strategy to promote neuroprotection in glaucoma.[28]
Antagonists
Blocking the activity of lingo-1 has several potential applications in the treatment of neurodegenerative diseases.[18][31]
(A myelin sheath is a lipid protective coating that covers and protects nerve cells (axons). These sheaths makes possible rapid and accurate transmission of nerve signals. Multiple sclerosis destroys these myelin sheaths, leading to a deterioration in nerve signal transmission. Once this protective myelin coating is stripped away, it leads to apoptosis of the neuron; axons gradually die, causing the muscle spasms and paralysis that are characteristic of the disease.[32])
Anti-lingo-1 (BIIB033)
Anti-lingo-1 (BIIB033) is a monoclonal antibody specific to the lingo-1 protein and is designed to promote remyelination (the formation of new myelin on axons) and neuroprotection.[16][33]  The protein lingo-1 inhibits the action of myelin-making cells, oligodendrocytes, which are surrounding the axons. Its antagonist, the antibody anti-lingo-1  would block this protein and even would be capable of myelin repair.
A number of clinical trials of the anti-lingo-1 antibody drug (BIIB033) have either been completed or are underway.[34] Acute optic neuritis (AON) is a disease which involves damage within the nerve fibers and loss of myelin within the optic nerve (it normally involves one eye and it's characterized by inflammation).[35] One clinical trial studying the effects on BIIB033 on acute optic neuritis.[36] Throughout the study, optic nerve conduction latency was measured (the time for a signal to travel from the retina to the brain's visual cortex).[37] As about half of patients with optic neuritis will later develop multiple sclerosis, BIIB033 antibody treatment is also being considered for the former disease. It is thought that Anti-Lingo-1 would produce the necessary myelin to avoid neurodegeneration.[38]

Further reading