AN/APQ-13 Radar – the all-seeing eye

By: shortfinals

Mar 27 2011

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Category: aircraft, Aviation, England, Great Britain, military, Museums, New England, RAF, Royal Air Force, Second World War, South Yorkshire, United States, warbird

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Focal Length:18mm
Shutter:1/0 sec
Camera:NIKON D40

It all began with the search for a ‘death ray’. In the 1920s, a heady mix of scientific advances and social change made it seem that almost anything was possible. Great Britain had just gone through the First World War as one of the major participants, and London had been bombarded from the air by German airships (Zeppelin and Schütte-Lanz types) and by fixed-wing aircraft (Gotha G.IV and Zeppelin-Staaken Riesenflugzeuge R.VI). Post-war, the political climate had changed and Stanley Baldwin, the former Prime Minister (and cousin of Rudyard Kipling), said in a 1932 speech, “…  there is no power on earth that can protect (the man in the street) from being bombed.” Fortunately, this semi-defeatist attitude did not prevail and by 1935, the Director of Scientific Research at the Air Ministry had asked the prominent radio researcher Robert Watson-Watt (later, Sir Robert Alexander Watson-Watt, KCB, FRS, FRAeS) to investigate the possibility of producing a ‘death ray’ to be used against aircraft. It was rumoured that Nazi Germany was already working on one!  Calculations soon showed that the power required would be incredible, but that there was a chance aircraft could be detected by radio waves, and their range and bearing from the detecting apparatus deduced.

Watt, who was later described as ‘The Father of Radar’, arranged for a biplane Handley Page Heyford bomber of the RAF to circle the high-powered transmitters of the BBC, which were located at Daventry, Northamptonshire, about 80 miles north-west of London. The test took place on 26th February, 1935, and the Heyford clearly reflected the signal from the BBC transmitters and was detected by a bipole antenna rigged by Watson-Watt and his assistant, Arnold Watkins. This directly led, five years later in 1940, to the Chain Home series of ‘Radio Direction Finding’ (the early, British name for radar) stations which, quite literally, allowed the RAF to win the Battle of Britain.

Early radar was strictly ground-based, and it wasn’t until 1939 that the first airborne set was fitted into a fighter aircraft, a Bristol Blenheim Mk 1F. The very first radar-equipped kill came on the night of 21/22nd July, 1940 when a Blenheim of the Fighter Interception Unit (a trials section) shot down a Dornier 17 over the Thames Estuary. Higher-powered radar was needed as aircraft performance advanced, and valve-based systems were neither robust nor powerful enough.

In the United States, early tests by the United States Army Signal Corps and the Naval Research Laboratory were followed by the establishment, in 1940, of the Radiation Laboratory at the Massachusetts Institute of Technology, tasked with developing radar for the war effort. Britain generously shared their developments in the 10cm waveband (using a resonant cavity magnetron) which had given rise to the H2S radar. This had the ability to ‘paint’ a picture of the ground below a high-flying aircraft, and was fitted in large numbers to the Avro Lancaster and Handley Page Halifax heavy bombers of RAF Bomber Command for their night bombing campaign against German targets, as well as to the Vickers Wellingtons of Coastal Command for attacks on surfaced Kreigsmarine U-Boats in bad weather and at night, and to small numbers of the superb de Havilland Mosquito aircraft as a precision marking aid for the Main Force of RAF Bomber Command.

With typical American ingenuity and industrial drive, the H2S became the H2X, fitted to selected USAAF Boeing B-17 Flying Fortress and Consolidated B-24 Liberator aircraft to improve bombing through cloudy European skies, and – in a version operating at at 3cm wavelength for improved definition – to the mighty Boeing B-29 Superfortress, for use in the crushing attacks which finally brought the Japanese to defeat in 1945. Here we can see a ‘dish’ antenna from an AN/ANQ-13 radar, (a development of H2S by MIT, Bell Laboratories and Western Electric) as fitted to a B-29 Superfortress; it is displayed at the New England Air Museum, Windsor Locks, Connecticut. It is safe to say that without this radar, winning the final battles of World War Two would have been much more difficult.

By some irony, a side-effect of the AN/APQ-13 radar, namely being sensitive to water droplets (and, therefore, clouds) in its final, 1.5cm wavelength form,  gave rise to a career in the United States as a local weather radar at various military bases until the late 1940s. Appropriately, the longest use of the H2S was by the RAF, who used the H2S Mk 9 in their Handley Page Victor and Avro Vulcan nuclear bombers (and air-to-air refueling variants of the same aircraft). The last Vulcan was retired from RAF service in March 1984, but XH558 was kept as a display aircraft until 1992, when it was sold to a civilian buyer. Note: I was at RAF Finningley, South Yorkshire, when XH558 gave a final display over the base as a service aircraft, on her delivery flight to her new owner. Shortly afterwards, the Vulcan To The Sky Trust was formed to keep the Vulcan in flying order. XH558 gave wonderful displays all over Britain, until she was flown into retirement at Doncaster-Sheffield Airport on the 28th October, 2015.

The H2S radar and its successors – one of the most significant developments in avionics

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