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AssigneeRosemount Aerospace Inc.
InventorRoger D. Foster
Estimating the term…
A method of and apparatus for obtaining angle of attack, local static pressure and local pitot pressure from measured pressure values at ports of a probe having angle measuring ports with angle measuring axes lying in a plane and a pitot port having an axis lying along an axis in the plane bisecting the angle between the measuring ports. A table of known values of angle of attack relative to measured pressure ratio at measured Mach numbers determined by P1/Pm is stored in memory and used when P1 is greater than the pressure sensed at the pitot port (Pt′m), P1 is the pressure measured at the one of the angle measuring ports that is higher than the pressure measured at the other angle measuring port, and Pm is an average of the pressures at the angle measuring ports. The correlation of the ratio of measured pressures on the probe relative to angle of attack is determined using the known values P1/Pm at different angles of attack either in wind tunnel tests or by computer simulation. The known values are stored in a look-up table in an onboard air data computer. The values that have been stored then can be retrieved to solve for the correct angle of attack, using the measured pressures P1, P2 and Pt′m. The angle of attack values are used with an algorithm to determine local pitot and static pressure.
The method of providing angle of attack of an object using a pressure ratio obtainable from air data sensing ports on the object providing pressures P1 and P2 which vary from each other at changing angles of attack and also providing a pitot pressure Pt′m, comprising providing predetermined values of angle of attack for values of the pressure ratio at Mach numbers related to measured P1/Pm, where P1 is the higher of the pressures P1 and P2, and Pm is the average of pressures P1 and P2, and using the predetermined values to obtain angle of attack from measured pressure values forming the pressure ratio, when P1 is greater than Pt′m.
A method of using measured pressure signals from an air data sensor to provide accurate corrected pressure parameters wherein the air data sensor has a pair of angle sensing ports with sensing axes positioned in a plane, and indicating an angle of a center reference line relative to a flow direction line past the sensor to provide angle of attack, and having a pitot port having an axis lying along the center reference line, and wherein pressures sensed at the respective angle sensing ports differ when the reference line is at an angle relative to the flow direction line with a higher of the pressures at the angle sensing ports being designated P1, a pressure at the other of the angle sensing ports being designated P2, and a pressure at the pitot port being designated Pt′m, comprising measuring P1, adding P1 to P2 and dividing by 2 to obtain a quantity Pm, and dividing P1 by Pm to obtain measured Mach number when P1 is greater than Pt′m.
A method of determining angle of attack of an air vehicle from measured pressure signals sensed by a pair of angle sensing ports on the vehicle with axes lying in a common plane, with a reference line in the common plane, and indicating an angle of the reference line relative to a flow direction line in the plane, and from measured pressures at a pitot pressure sensing port on the air vehicle having an axis lying along the reference line, and wherein the pressures sensed at the angle sensing ports differ when the reference line is at an angle relative to the flow direction line, with a higher pressure at the angle sensing ports being designated P1, a pressure at the other of the angle sensing ports being designated P2, and a pressure at the pitot port being designated Pt′m, the method comprising obtaining a ratio from signals representing P1, P2 and Pt′m, by adding P1 to P2 and dividing 2 to obtain a quantity Pm, and dividing P1 by Pm, only when P1 is greater than Pt′m to obtain the ratio, and using the ratio to determine measured Mach numbers.
An apparatus for determining angles of attack across a range comprising:
Dependencies are inferred from the claim text.