resonant frequency (mechanical vibration). The frequency at which a mechanical object vibrates, or oscillates, with the maximum amplitude for the amount of energy used to produce the vibration. The resonant frequency of an object is sometimes called its natural frequency.
respirator. A device worn over the mouth and nose of a person working in an atmosphere of dangerous gases or contaminated air. Some respirators supply oxygen or clean air for the wearer, while others simply filter the contaminants from the air.
restricted area. 14 CFR Part 1: “Airspace designated under Part 73 of this chapter within which the flight of aircraft, while not wholly prohibited, is subject to restriction.”
restrictor (fluid-flow system component). An orifice installed in a fluid flow system to decrease the amount of fluid allowed to flow under a specific amount of pressure.
resultant flux (aircraft magneto flux). The total magnetic flux that cuts across the secondary winding of the magneto coil. Resultant flux is the combination of the permanent magnet flux and the flux produced by current flowing in the primary winding of the coil.
resultant vector. A single vector which is the sum of two or more vectors.
“Resume normal speed” (air traffic control). A phrase used by ATC to advise that previously issued speed control (controller assigned or as part of a published procedure) restrictions are deleted. This statement does not relieve the pilot of those speed restrictions which are applicable to 14 CFR, Part 91.117.
“Resume own navigation” (air traffic control). A phrase used by ATC to advise a pilot to resume his own navigation responsibility. This is issued after completion of a radar vector or when radar contact is lost when the aircraft is being radar vectored.