GB572308A - Improvements in or relating to airspeed indicators - Google Patents

Abstract

572,308. Air-speed indicators. BENDIX AVIATION CORPORATION. July 14, 1943, No. 11488. Convention date, June 13, 1942. [Class 106 (ii)] An air-speed indicator having a pressureresponsive element 18 adapted to operate indicating-mechanism and subjected to a pressure differential through a static pressure connection to one side of said element and a dynamic pressure connection to the other side thereof, is characterized by compensating means 35 provided in one of said pressure connections for varying the pressure differential on said element to compensate for change of pressure due to altitude. As shown, the outside of a pair of capsules 18 is subjected to the pressure inside a casing 10 derived from a static pressure source 30. The inside of the capsules is connected to a pitch tube 32, through a diffuser 35 constructed of carbon, porcelain, compressed powder or metal wool, paper or very thin metal such as gold, of the type described in Specification 507,990. The action of the diffuser is to increase the volume of air flow as the pressure drops and so maintain the pressure differential constant for a given speed at any height. The usual capillary leak 38 is provided. A further diffuser 40 (Fig. 3, not shown) may be provided in the static pressure connection. The capsules operate an indicator 24 through lever-and-chain mechanism against the action of a spring 29. Specifications 507,992 and 507,993 also are referred to.