Strut mounted multiple static tube

A static pressure measurement probe for providing pressure compensation to offset effects of adjacent structures, such as an aircraft fuselage, on local static pressure at the probe comprising:

• a probe barrel having an elongated central longitudinal axis, and an outer surface that changes smoothly in cross section with both a reducing size portion and an increasing size portion to form a corrugation on a portion of the outer surface;
• and
• static pressure port means opening through said probe barrel adjacent said changes in cross section in at least two axially spaced locations on the outer surface which have a desired ratio of static pressure.

A fluid pressure sensing probe including an elongated barrel having first and second ends, means to mount said barrel at said second end to position the barrel with respect to a fluid stream, said barrel having a longitudinal axis and an outer surface comprising a surface of revolution around said axis, said barrel being subjected to a relatively moving fluid stream generally along the longitudinal axis, and the outer surface of said barrel comprising at least one annular corrugation having a bisecting plane between annular lines of different diameter, and at least two pressure sensing port means on said outer surface adjacent the bisecting plane of said annular corrugation and each pressure sensing port means being located at surface positions spaced along the longitudinal axis of the probe where the static pressure sensed is at a desired ratio between the respective pressure sensing port means.

In a probe for sensing static fluid pressures, said probe having a laterally extending mounting strut at a rear portion thereof for mounting said probe in spaced relationship to an external surface in a fluid flow stream and having a probe barrel having a generally cylindrical surface portion and a longitudinal axis, the improvement comprising:

• at least two annular constrictions forming spaced corrugations on the outer surface of said barrel in position between the leading end of said probe and the strut to form a pressure disturbance along said barrel;
• and
• at least two sets of port means adjacent the corrugations and located axially on the probe where substantially equal static pressure occurs on opposite sides of at least one annular constriction.

A method of determining locations to place static pressure sensing ports on a probe having corrugations therein which provide an annular corrugated surface on the probe and provide substantial changes in static pressure from local static pressure of the fluid in which the probe is used, comprising providing a probe having sufficient corrugations to provide a pressure profile plotting the pressure profile on X-Y coordinates as a normalized pressure function along the Y axis with the axial distance of the probe being represented along the X axis and to have at least two negative pressure peaks and two positive pressure peaks, and drawing a horizontal line at a location where the horizontal line intersects at least four points on the profile on either the positive or negative side of the profile, and locating static pressure sensing port sets in at least two locations of substantially equal pressure on the probe selected by the intersections of the horizontal line with the profile.