579681-A is referenced by 1 patents.
579,681. Testing aircraft. GRAY, W. E. Nov. 12, 1943, No. 18810. [Class 4] In order to study the airflow over an aeroplane part, such as a wing, it is coated with a thin layer of starch mixed with potassium iodide with or without a small quantity of glycerine, and the part is then subjected in a wind tunnel or during free flight to the action of chlorine or ozone released into the airstream some distance ahead, the resulting differences in the degree of colouration indicating the areas of transition from laminar to turbulent flow. Smoke may be mixed with, or discharged in close proximity to the chemical gas to render it visible. A photographic record may be made of the colouration for comparison with others. Alternatively, a coating may be used which shows the action of the chemical gases only after further treatment.; In the wind tunnel shown, the chemical gases are introduced through a tube 5 at a point where the wind velocity is relatively low and at. a sufficient distance from the part 4 to be tested to enable the disturbance of the airflow caused by such introduction to die down before reaching the test specimen. For testing in free flight, the gases are discharged from an aeroplane flying some distance in front of the craft being tested or they may, be released from a shell-like contamer fired up to or dropped to the test level where it bursts. Sodium thiosulphate may be added to the starch coating to prevent gradual discolouration when flying before and after the test. According to the Provisional Specification, a thin coating of lead acetate may be applied to the wing and subjected to the action of sulphuretted hydrogen.