Simultaneously with the flight tests of Avro 707, wind tunnel investigations were being conducted to supplement the flight tests.& The low speed wind tunnel tests were conducted using the 9' by 7' wind tunnel and a complete 1/8th scale model of the aircraft that had been supplied by A.V.Roe & Co. This model was fitted with adjustable elevators and trim flaps. Surface pressures were measured at low speed on both the Avro 707 in flight, and on the scale model in the 9' by 7' wind tunnel. The first phase of the research programme utilising WD280 consisted of conducting a detailed evaluation of the development of flow separation and then comparing this with the model. A flow visualisation technique utilising a marine flare was developed. The flare was wrapped in asbestos, loaded into a fairing underneath the port wing and then ducted, via a pipe to the leading edge. The flow pattern of the red smoke over the wing was then photographed from a formating aircraft. Flow separation was associated with large increases of drag and deterioration of both lateral and longitudinal control due to poor aileron and elevator control.

In late 1958, Wing Commander Cousins, who was now the Chief Test Pilot at ARDU, handed over the flying of WD280 to Flight Lieutenant Randall Green. A series of flight tests was undertaken to evaluate low speed handling. Carborundum dust was applied to the undersurface of the leading edge using an acetate adhesive to produce a rough surface. Varying sizes of grit and varying spanwise extent of the application gave rise to four different test conditions. Detailed measurements were only made when the pilot considered that a particular test condition had produced a significant alteration in the aircraft's handling characteristics or its performance. It was found that leading edge roughness gave improved and easier control of the aircraft at low speeds as there was more aileron and elevator effectiveness. The improvement in aircraft handling with the application of carborundum dust prompted a series of tests employing turbulators. These tests were performed by the placement of small vane type protuberances (turbulators), of varying the height and spanwise extent, on the wing. With the first turbulator test condition a greatly improved aileron and elevator effectiveness was apparent. In fact, 10-degree banked turns executed at 107 knots were made comfortably - a manoeuvre not recommended with the clean aircraft. The first wing drops became apparent at 92 knots IAS. but were unassociated with any yaw and thus no wallowing. This latter effect was one of the most undesirable characteristics of the clean aircraft.