Abstract: A skin friction measuring device for measuring the resistance of an aerodynamic surface to an airstream, adapted to be mounted on an aircraft, within an opening defined therein, and characterized by a friction plate adapted to be disposed in a flush relationship with the external surface of the aircraft and be displaced in response to skin-friction drag, as an airstream is caused to flow over the surface thereof, and a potentiometer connected to the plate for providing an electrical output indicative of the magnitude of the drag.

Abstract: A system supported by a wing in flight having a reference total pressure port in spaced relation with a wake as the wake is generated by the wing, a reference static pressure port supported in spaced relation with the wake, a probe adapted to be displaced along an arcuate path through the wake including a total pressure port and static pressure ports. A differential pressure transducer and a pressure switching device interposed between the ports and the transducer is provided for selectively connecting pairs of the ports to the transducer in opposed relation, whereby a single transducer is utilized in obtaining differential pressure measurement for the wake with enhanced accuracy.