Abstract: A passively controlled hydrofoil supported planning watercraft having a conventional hull with an integrally formed step. The watercraft includes a centrally located, fully submerged main lifting foil. The main lifting foil is fixed and non-movable, and is attached to the hull along the centerline keel such that its line of action acts substantially through the longitudinal center of gravity of the watercraft. The watercraft further includes a rearwardly located stabilizing foil fixed to a stabilizer strut which is pivotally attached to the stern of the watercraft. A stabilizer strut so attached pivots fore and aft to control watercraft trim angle. Additionally, the stabilizer strut is rotatable about a substantially vertical axis for steering and roll control, and includes a trailing edge upper rudder for yaw control.

Abstract: An angle of attack indicator for use as a cockpit instrument including movable variable-area diaphragms which respond to the differences in pressure at selected points on the aircraft. The pressure points may include the total pressure sensed by the aircraft pitot tube and two other pressures at least one of which varies strongly with the angle of attack. The mechanism divides the difference between total pressure and one of the other two pressures by the difference between the total pressure and the other of the other two pressures obtaining a pressure coefficient which depends only on the shape and angle of attack of the aircraft. The use of the variable diaphragm as the sensitive element of a low level pressure sensor as in an aircraft airspeed indicator is described.