Within days of the outbreak of the Second World War it was clear that German bombers were going to present enormous problems to the defence planners. With Stukas and Heinkels rampaging across Polish skies, it was clearly time to take a hard look at what defences Britain offered against air attack. It was the protection of the RAF stations which became the Air Ministry’s first priority. The decoy principle, drawing German bombers away from a genuine airfield onto a dummy site some five or six miles away, had been tried out during the First World War. This ruse had enjoyed some success and the decoys had in fact been attacked on a number of occasions.
Twenty-one years later, in September 1939, the subject was revived and a new department was set up under one of the war’s most imaginative and dynamic figures, Colonel J F Turner, to investigate and co-ordinate the concept of defence by deception. Such was the need for security that this branch of the Air Ministry was given the anonymous name of ‘Colonel Turner’s Department’, or CTD.
Under Colonel Turner’s leadership, the work of "CTD" quickly flourished, with the development of a whole range of decoy types. With an initial brief to protect the airfields, the first was the daytime ‘K’ site. This attempted to duplicate the appearance of a normal operational aerodrome as seen from the air. But mown "runways", dummy trenches and scattered cars were by themselves unrealistic. What was needed was "genuine" aircraft. The question of a dummy air fleet, built of wood and canvas, to give the decoy sites that essential touch of credibility, had been mooted at an early stage. However, cost had been a problem. Tenders from commercial manufacturers for the construction of Hurricanes, Battles and Whitleys had been impossibly high. The answer came from an unexpected quarter - the film companies. Equipped to reproduce realistic scenery quickly and cheaply they were ideal for the job. Not only were they well-qualified but they were enthusiastic, particularly Sound City Films, at Shepperton, Middlesex, who eventually became the major producer of Britain’s dummy air fleet. With ten mock aircraft per site, thirty-six ‘K’ sites, each shadowing a particular RAF station, were completed by the summer of 1940.
To ascertain the success, or failure, rate of each installation, records were kept of the number of attacks which fell on both the decoy and its parent station. These showed that despite all efforts to make them look realistic, ‘K’ sites never quite succeeded. This was confirmed when a German reconnaissance plane was shot down in October 1941. Among the items recovered from the wreckage was a map with as many as half of the ‘K’s clearly marked as decoys. Although ‘K’ sites did draw a small number of attacks, it was decided to run them down and by June 1942 they had all been closed.
Night-Time Lighting Decoys
In tandem with the ‘K’ sites, came their night-time equivalents, the ‘Q’ sites. Intended to represent the working lights of an airfield after dark, this type of decoy was centred around electric "runway" lighting laid out to genuine operational patterns and controlled from a bunker which housed the necessary generator and switchgear. Further authenticity was provided by the inclusion of obstruction and recognition lights. The headlamp of a taxiing aircraft added more refinement, in reality a light turned by hand. As no pilot was likely to be fooled by a blaze of airfield lighting during blacked-out wartime, operation of these facilities took a certain finesse. Once the decoy had been informed of the approach of enemy aircraft by its parent station, the trick was to anticipate the point at which the pilot had just seen the display, before switching it off. A subtle touch of realism called for the leaving on of a couple of "careless" lights. ‘Q’ sites became the backbone of the airfield decoy defence and no fewer than 171 sites were eventually constructed throughout Britain.
In contrast to the ‘K’ sites, ‘Q’s were a raging success. By the time the last ‘K’s were being closed down in 1942, ‘Q’ sites had attracted half of all attacks directed against their parent stations. Out of 717 bomber attacks by the Luftwaffe, 359 had fallen on the open fields of the decoys, a success rate in which even the ever-confident Colonel Turner must have delighted.
The "QL" type built on the work of the night-time airfield decoys. Designed to protect marshalling yards, naval installations, armament factories, and a whole host of important targets, each was individually designed to imitate its parent complex. Enormous efforts were made to try and duplicate the exact night-time appearance of the site, or at least part of it. Strange devices emitted sparks to look like tram flashes, orange lights shining down onto sand were made to simulate furnace glows, doors opened and closed, spilling light onto the ground, red and green railway signals blinked on and off, riveting fires glowed and then died down. With secrecy paramount, all these effects laid out across otherwise black, empty fields, would go largely unseen - except, it was hoped, by the German bomber pilots.