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The Dowding System

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Saved by Alan Hartley-Smith
on October 22, 2020 at 12:41:26 pm
 

Military Early Days

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Introduction

This bears its name as being the brainchild of Air Chief Marshal Sir Hugh Caswall Tremenheere Dowding that enabled the Royal Air Force with more limited resources in 1939 at the start of WW2 to defeat the intention of the much larger Luftwaffe to clear and command the skies over the English Channel and United Kingdom, a prerequisite to Operation Sealion, Hitler's invasion plan. 

 

The solution was to bring science into the arena, and comprised two areas of technological developments - the new ability to detect the incoming enemy bombers and their fighter escorts sufficiently early together with the ability to then get the defending fighters into position in time to destroy them in sufficient numbers. Among others Marconi was extensively involved in both areas based on its work on radio telephony during the First World War and its capabilities in research and engineering in wireless and television and management of large-scale systems. In the modern era through mergers in the now electronics industry virtually all of the other companies involved became part of the Marconi group and therefore are included in this wiki. In point of fact there was also a third arm, a nation-wide installation of addition telephone lines by the General Post Office, itself alone a massive undertaking.

 

The Dowding System  1.  2.

The genesis of this is a complex story and and covers a long period of time - there are several books (see reading list below) which cover it in great detail, but for the present purpose it is useful to have just a summary of the main points.

 

The first aerial bombing of England was in 1914 and continued through until 1918. This resulted in the creation of the world's first strategic air defence system, the design of which influenced the work throughout the 1920s and 30s, and featured the use of aerial radio telephony, and the development of a central command structure to gather and disseminate information to regional control rooms with plot spotting on a map. A very interesting description is available here. However, the general feeling at the time was summed up in a statement by Stanley Baldwin "..... the bomber will always get through"  Notwithstanding, work continued including the formation of an organisation "Air Defence of Great Britain" or ADGB to coordinate air defensive and offensive forces. In 1924 the then new Royal Air Force created a Directorate of Scientific Research whose first Director was Henry Wimperis, who came to learn of the work of Robert Watson Watt on ionospheric radio research at the National Physical Laboratory. Wimperis formed the Committee for the Scientific Survey of Air Defence (CSSAD) (also known as the Tizard Committee as he was the Chairman) and his immediate superior was Air Chief Marshal Dowding. Dowding had served in World War 1 and had direct experience of aerial combat so was well aware of the difficulties encountered. During the 1920s and 1930s he served in a variety of service and government posts and became Officer Commanding the RAF Fighter Command, so through CSSAD he was able to initiate the funding for the work which culminated in the development of the Chain Home radar system. In parallel there was continuing work on the technology of wireless direction finding, including the Biggin Hill Experiment and other trials, which greatly increased the accuracy and speed of position determination of the fighters using the Pip-squeak navigation system, together with the development of a method of identifying friendly aircraft, IFF, and incidentally stimulated the development of airborne radar for final interception. Dowding was therefore able to combine these activities together with the enlarged telephone system, the existing Observer Corps, and the new discipline of operational research which enhanced the multiple control room method to create the "Command and Control" system that enabled him to direct fighters onto German attacks; taking advantage of fighting above Britain's home territory allowed the RAF to deny Germany air superiority, saving the UK from possible German invasion and dealing the Axis a major defeat early in the Second World War by winning the Battle of Britain.

 

See the modern manifestation of the system Headquarters here

 

The memorial in Westminster Abbey

 

A comprehensive description of the extensive studies and actions carried out during the 1930s that enabled this result can be found in the Radio chapter of "The Narrow Margin". 

 

A broad description of the whole Radio Warfare scenario is given in this postwar Technical Staff Monograph also here

 

This is an extract from Dowding's official despatch which goes into great detail of all aspects of the Battle.

 

Battle of Britain Historical Society

 

BOBHSOC

 

Entry on IWM site

 

The Technologies

 

Radar

This was the new detection development, in particular the creation of the Chain Home series of radars which, as part of the central topic of this wiki, is already covered in detail here. From this initial military inception postwar radar continued to develop in both defence and offence applications and also moved into the civilian arena through air traffic control, which is also covered in the wiki.

 

In the original Dowding system of fighter control, information from the Chain Home coastal radar stations was relayed by phone to a number of operators on the ground floor of the "filter room" at Fighter Command's headquarters at RAF Bentley Priory. Here the information from the radar was combined with reports from the Royal Observer Corps and radio direction finding systems and merged to produce a single set of "tracks", identified by number. These tracks were then telephoned to the Group headquarters that would be responsible for dealing with that target. Group would assign fighter squadrons to the tracks, and phone the information to Section headquarters, who were in direct contact with the fighters.

Because the Chain Home radar stations faced out to sea, once airborne intruders had crossed the British coast they could no longer be tracked by radar; and accordingly the interception direction centres relied on visual and aural sightings of the Observer Corps for continually updated information on the location and heading of enemy aircraft formations. While this arrangement worked acceptably during the daylight raids of the Battle of Britain, subsequent bombing attacks of The Blitz demonstrated that such techniques were wholly inadequate for identifying and tracking aircraft at night.

 

Experiments in addressing this problem started with manually directed radars being used as a sort of radio-searchlight, but this proved too difficult to use in practice. Another attempt was made by using a height-finding radar turned on its side in order to scan an arc in front of the station. This proved very workable, and was soon extended to covering a full 360 degrees by making minor changes to the support and bearing systems. Making a display system, the "Plan Position Indicator" (PPI), that displayed a 360 degree pattern proved surprisingly easy, and test systems were available by late 1940.

Starting in 1941 the RAF began deploying production models of the GCI radar, first with expedient solutions, and then permanent stations. Unlike the earlier system where radar data was forwarded by telephone and plotted on a map, GCI radars combined all of these functions into a single station. The PPI was in the form of a 2D top-down display showing both the targets and the intercepting night fighters. Interceptions could be arranged directly from the display, without any need to forward the information over telephone links or similar. This not only greatly eased the task of arranging the interception, but greatly reduced the required manpower as well.

As the system became operational the success of the RAF night fighter force began to shoot up. This was further aided by the introduction of the Bristol Beaufighter and its AI Mk. IV radar which became available in numbers at the same time. These two systems proved to be a potent combination, and interception rates doubled every month from January 1941 until the Luftwaffe campaign ended in May.

 

High Frequency Direction Finding

Direction finding has a distinguished civil and military history dating from Marconi's earliest experiments in tracking wireless transmissions, in particular with regard to shipping, and played a very important role in air, ground and particularly naval operations in the First World War using a system devised by a Marconi engineer H.J. Round, who was seconded to Military Intelligence. Using his experience, he first set up a chain of DF stations along the Western Front and these proved so successful that another set was installed in England followed by several more. In May 1916, the stations were monitoring transmissions from the German Navy at anchor at Wilhelmshaven, and at the end of the month they were able to report a 1.5-degree change in the direction of the signals implying that the ships were on the move, so the Admiralty ordered the British fleet to set sail to engage the German fleet and as a result the Battle of Jutland occurred the next day, which effectively removed the German fleet from the war. A very comprehensive description of a typical Naval Station is here

 

Continuing development on the use of DF for both sea and air operations during the period between the wars led to the adoption of High Frequency Direction Finding known for short as HFDF and colloquially as Huff Duff. It is appropriate to include it as a section in this wiki as much of the later work was also carried out at the Marconi Research Laboratories at Baddow as detailed below in parallel with the work on the associated radar systems.Its practical application in the Battle is decribed here

 

Input by Roy Simons

Most of the later wartime DF work was done at in Section E and Section K in which T.L.Eckersley was the prime mover - he invented the spaced frame system that did not need to be installed on a conducting earth or mat. His staff included  G.Millington, K.Tremellen and S.B.Smith. G.Isted ran the laboratory work of Section E and experimental work in a large hut in the field with WREN assistance. R.J.Kemp ran Section C with R.F.O’Neill, ? Waring, ? Fewings and me.  Others involved at some time included F.P.Best, J.H.Moon, J.Vickers, S.A.W.Jolliffe, J.S.Forbes. We had a detachment of RAF wireless operator mechanics attached to us to build some equipment etc.  We had a number of flight trials over the site which required a lot of night time working.

 

Earlier DF equipment was designed in New Street over many years and an Adcock system with a Type DFG12 receiver, the latest pre-war version, in which J.F.Hatch was involved, was that used during the war. A later version was the Type DFG24 using a CRT. I developed a VHF automatic version for later detection of V2 missiles in case they had radio guidance but they did not. I do not know if any of the Eckersley spaced frame HF equipments were used in the UK - I know several were used in the desert and in the Far East.

 

There were many more other developments in progress in these early days at Baddow following on from the research carried out at Broomfield, Hall Street and New Street.

 

Just to illustrate how important DF continued to be is shown by this extract from Practical Wireless June 1951:

 

Jet Aircraft Radio at the Festival

A replica of the cockpit of the Comet, the world's first jet airliner, showing its complete Marconi wireless communication and navigational aid equipment will be exhibited in the Transport Pavilion, at the South Bank Exhibition of the Festival of Britain. This Pavilion houses not only exhibits of great historical value, showing the development of transport and communications, but also some of the most up-to-date equipment. . The Comet equipment consists of two high-power high-frequency transmitters, two high- and medium-frequency high-discrimination receivers and two automatic direction finders. Voltage regulators for this installation are also of Marconi design and manufacture.

The Comet is also fitted with Marconi suppressed aerials which do not protrude above the skin of the aircraft but which are built into the structure as an integral part of aerodynamic design. One of the greatest aeronautical advances of today is embodied in this new technique which also embraces the loop aerials associated with the automatic direction finder. All that is necessary to navigate with the automatic direction finder is for one member of a crew to tune the receiver to any transmitting station. Bearings of that station can then be read off, continuously and instantaneously, by members of the  crew. Repeater bearing indicators and receiver control boxes can be installed and repeated at any crew position.

Visitors to the Festival will thus be able to see a vital part of one of the world's greatest aircraft.

 

Reading list

Dowding of Fighter Command - Vincent Orange - Grub Street

Tizard - Ronald Clark - Methuen

RDF1 - Michael Bragg - Hawkhead

BUILDING RADAR - Colin Dobinson - Methuen

Britain's Shield Radar and the Defeat of the Luftwaffe - David Zimmerman - Amberley

The Narrow Margin - Derek Wood and Derek Dempster - Tri-Service Press

Direction and Position Finding by Wireless (4th ED 1947)- Ronald Keen - Iliffe (Major Keen spent a lot of his time at Marconi)

 

Other online references 1.

 

 

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