 The AI group and their experimental aircraft of D Flight , A & AEE , moved to an airport some distance away at Perth , Scotland . The airport was completely unsuitable for the fitting work , with only a single small hangar available for aircraft work while a second was used for offices and labs . This required most of the aircraft to remain outside while others were worked on inside . Nevertheless , the initial group of aircraft was completed by October 1939 . With this success , more and more aircraft arrived at the airport to have the AI team fit radars , most of these being the ASV units for patrol aircraft like the Lockheed Hudson and Short Sunderland , followed by experimental fittings to Fleet Air Arm Fairey Swordfish and Supermarine Walrus . 
