Pressure sensor for determining airspeed altitude and angle of attack

An air data sensor for determining the angle of attack of the sensor relative to the direction of fluid moving relative to the sensor comprising a probe having an elongated probe barrel with a longitudinal axis, said barrel having first and second barrel sections of substantially similar cross sectional shape, but of different cross sectional dimensions, said second barrel section being of larger dimension than the first barrel section and trailing the first section with respect to the direction of relative fluid motion, and a barrel transition section defining an exterior surface joining said first and second barrel sections and increasing in size from the first barrel section to the second barrel section, first and second port means open through the barrel and symmetrically formed about a common central axis and facing in opposite directions, said common axis intersecting the longitudinal axis to thereby define a plane, means to individually sense the pressures at each of said first and second port means and provide signals representative of the sensed pressures as p.sub..alpha.1 -p.sub..alpha.2 at the first and second ports, respectively, means to provide a signal representative of the pitot pressure at the leading end of the barrel as p.sub.t, means for providing the difference between the signals representing the pressures at the first and second port means and for dividing said difference by a signal representing a pressure function including the signal representing the pitot pressure and pressure at the probe related to measured static pressure for thereby providing a ratio signal which varies as a function of the angle of attack and which ratio signal increases in output per degree of change of angle of attack as the angle of attack increases above a known amount.

The method of determining the angle of flow of a probe having a longitudinal axis with respect to the direction of relative fluid movement past the probe, said probe having a first leading end section of generally cylindrical configuration, and an expanding size conical section downstream from and joining the leading end section, and a second generally cylindrical section of larger size than the first generally cylindrical section joining the conical section at its downstream end, comprising the steps of providing a pitot pressure signal representing the pressure at the leading end of the probe and a signal representing the static fluid pressure adjacent to the probe;

• providing on the conical section first and second oppositely facing port means each being centered on the same plane passing through the longitudinal axis of the probe;
• individually sensing the pressures at each of said first and second port means;
• and
• correlating the pressures at the first and second port means and selected other sensed pressures for providing a signal representing a ratio selected in accordance with one of the ratios formed in the following group of (a) and (b):
• (p.sub..alpha.1 -p.sub..alpha.2)/(p.sub.tm -p.sub.m) (a) ##EQU4## when p.sub..alpha.1 and p.sub..alpha.2 represent the pressure at the first and second port means, respectively, p.sub.tm represents pitot pressure at the leading end of the probe, and p.sub.m represents static pressure adjacent to the probe, to provide a ratio which increases in sensitivity to angles of flow when the angles of flow being measured range upward from about twenty degrees.