Patent GB-660092-A (GB)
Title: Improvements in or relating to hot air supply systems for aircraft
IPC: B64D15/02
Filed: 1944-10-20
Abstract: 660,092. Preventing the formation of snow and ice on aircraft surfaces; screw propellers. CURTISS-WRIGHT CORPORATION. Oct. 20, 1944 [Sept. 20, 1943], No. 20361/44. Classes 4 and 114. [Also in Groups XIII and XXIX] In a system for supplying a controlled volume of air at a controlled temperature for de-icing surfaces of an aircraft, the air passes directly from an air scoop through a first pipe to a heat exchanger or heater and thence to the surfaces, means being provided for controlling the amount and temperature of the air passing through the heater to the surfaces, and a second pipe, terminating in a section facing in the opposite direction from the air scoop and delivering air to the atmosphere, branches from the first downstream of the heater to form a bleed controlled by a valve to prevent undue heating of the heater. The temperature of the air is controlled automatically by valves (see Group XXIX) which cause either a proportion of the air or a proportion of the exhaust gases to bypass the heat interchanger while the rate of flow of the air is controlled by similar valves (see Group XXIX) which either return some of the indrawn air to the atmosphere or restrict the passages through which the air is conducted. The heated air may pass through the hollow blades of an airscrew having vents near the blade-tips. In Fig. 1 the temperature of air collected by a scoop 1, and passing through a conduit 2 including a heat interchanger 4 to a chamber 2b, is controlled by a temperature responsive valve unit 9, 11, 8 which controls the passage of air through a conduit 3 bypassing the heat interchanger 4 while the rate of flow of the air is governed by a valve unit 10b, 11 controlling a throttle 25. If the heat interchanger 4 becomes overheated more air may be drawn through it by operation of a valve controlling a conduit 5 which delivers air to the atmosphere. The chamber 2b forms a gland comprising a fixed annular housing 46 sealed by rings 45 to a housing 44 which rotates with the airscrew unit. From the chamber 2b pipes 47, 49, 48 lead heated air to the nose of the spinner 42, to the cuffs 43 of the blades and to the interior of the airscrew hub 40 respectively, the heated air escaping either through the cuffs, so heating the outsides of the blades, or through vents at the tips of the hollow blades 41. Other systems are described in which the rate of flow may be controlled by returning air to the atmosphere before passage through the heat interchanger, in which the valve units sensitive to temperature and rate of flow may be interconnected to provide a control dependent on both factors, and in which one control unit responds to atmospheric pressure. Several independently controlled paths leading to different surfaces may be provided for the air after passage through the heat interchanger. A booster in the pipe 2 may assist the flow of air through the system. The Specification as open to inspection under Sect. 91 also describes systems in which the bleed 5 downstream from the heater is replaced by a bleed upstream from the heater and controlled by valves to maintain a constant flow of air. In one such system temperature and flow control means as described above are provided for each of several independent outlets from the heater, together with similar means common to all the outlets. This subject-matter does not appear in the Specification as accepted.