Glossary

SDF. See simplified directional facility. Simplified directional facility (SDF). A NAVAID used for nonprecision instrument approaches. The final approach Selective availability (SA). A satellite technology permitting course is similar to that of an ILS localizer; however, the the Department of Defense (DOD) to create, in the interest SDF course may be offset from the runway, generally not of national security, a significant clock and ephemeris error more than 3°, and the course may be wider than the localizer, in the satellites, resulting in a navigation error. resulting in a lower degree of accuracy. Semicircular canal. An inner ear organ that detects angular Single-pilot resource management (SRM). The ability acceleration of the body. for a pilot to manage all resources effectively to ensure the outcome of the flight is successful. Semimonocoque. A fuselage design that includes a substructure of bulkheads and/or formers, along with stringers, Situational awareness. Pilot knowledge of where the aircraft to support flight loads and stresses imposed on the fuselage. is in regard to location, air traffic control, weather, regulations, aircraft status, and other factors that may affect flight. Sensitive altimeter. A form of multipointer pneumatic altimeter with an adjustable barometric scale that allows the Skidding turn. An uncoordinated turn in which the rate of reference pressure to be set to any desired level. turn is too great for the angle of bank, pulling the aircraft to the outside of the turn. Service ceiling. The maximum density altitude where the best rate-of-climb airspeed will produce a 100-feet-per-minute Skills and procedures. The procedural, psychomotor, and climb at maximum weight while in a clean configuration perceptual skills used to control a specific aircraft or its with maximum continuous power. systems. They are the airmanship abilities that are gained through conventional training, are perfected, and become Servo. A motor or other form of actuator which receives a almost automatic through experience. small signal from the control device and exerts a large force to accomplish the desired work. Skin friction drag. Drag generated between air molecules and the solid surface of the aircraft. Servo tab. An auxiliary control mounted on a primary control surface, which automatically moves in the direction opposite Slant range. The horizontal distance from the aircraft antenna the primary control to provide an aerodynamic assist in the to the ground station, due to line-of-sight transmission of the movement of the control. DME signal. SIDS. See standard instrument departure procedures. Slaved compass. A system whereby the heading gyro is “slaved to,” or continuously corrected to bring its direction SIGMET. The acronym for Significant Meteorological readings into agreement with a remotely located magnetic information. A weather advisory in abbreviated plain direction sensing device (usually a flux valve or flux gate language concerning the occurrence or expected occurrence compass). of potentially hazardous en route weather phenomena that may affect the safety of aircraft operations. SIGMET is warning Slipping turn. An uncoordinated turn in which the aircraft information, hence it is of highest priority among other types is banked too much for the rate of turn, so the horizontal lift of meteorological information provided to the aviation users. component is greater than the centrifugal force, pulling the aircraft toward the inside of the turn. Signal-to-noise ratio. An indication of signal strength received compared to background noise, which is a measure Small airplane. An airplane of 12,500 pounds or less of the adequacy of the received signal. maximum certificated takeoff weight. Significant weather prognostic. Presents four panels Somatogravic illusion. The misperception of being showing forecast significant weather. in a nose-up or nose-down attitude, caused by a rapid acceleration or deceleration while in flight situations that Simplex. Transmission and reception on the same frequency. lack visual reference. G-27