Diaphragm type angle of attack indicator

A diaphragm type angle of attack indicator for use as an aircraft instrument comprising, means for sensing three pressures on the aircraft, at least one of said three pressures varying strongly with angle of attack, another of said three pressures being greater than the other two pressures, tubing means for transmitting the pressures to a central area, and means at the central area for dividing the difference between the greatest pressure and one of the two lesser pressures by the difference between the greatest pressure and the other of the two lesser pressures, said dividing means including an enclosure having three operatively connected sections, pressure from a different point on the aircraft being transferred to each of the sections in said enclosure, the first of the sections being operatively connected to one of the two lesser pressures, the second of the sections being operatively connected to the other of the two lesser pressures, the third of the sections being operatively connected to the greatest pressure, a pair of rigid, members shaped as surfaces of revolution, one each being positioned in each of the first and second sections and having their apexes fixedly attached to each other, a pair of flexible plastic diaphragms positioned in the third section one each being in contact with the back surface of each of said rigid members, said flexible diaphragms effectively separating the third section from the first and second sections, such that changes in pressure in the first and second sections produces a lateral movement in said pair of rigid members, said movement corresponding to the difference in pressures at pressure points on the aircraft and to the angle of attack thereof.