Simplex. Transmission and reception on the same  frequency. Simplified directional facility (SDF). A NAVAID used  for nonprecision instrument approaches. The final approach  course is similar to that of an ILS localizer; however, the  SDF course may be offset from the runway, generally not  more than 3°, and the course may be wider than the localizer,  resulting in a lower degree of accuracy. Single-pilot resource management (SRM).  The ability for  crew or pilot to manage all resources effectively to ensure  the outcome of the flight is successful. Situational awareness. Pilot knowledge of where the  aircraft is in regard to location, air traffic control, weather,  regulations, aircraft status, and other factors that may affect  flight. Skidding turn.  An uncoordinated turn in which the rate of  turn is too great for the angle of bank, pulling the aircraft to  the outside of the turn. Skin friction drag.  Drag generated between air molecules  and the solid surface of the aircraft. Slant range.  The horizontal distance from the aircraft antenna  to the ground station, due to line-of-sight transmission of the  DME signal. Slaved compass.  A system whereby the heading gyro is  “slaved to,” or continuously corrected to bring its direction  readings into agreement with a remotely located magnetic  direction sensing device (usually this is a flux valve or flux  gate compass). Slipping turn.  An uncoordinated turn in which the aircraft  is banked too much for the rate of turn, so the horizontal lift  component is greater than the centrifugal force, pulling the  aircraft toward the inside of the turn. Small airplane. An airplane of 12,500 pounds or less  maximum certificated takeoff weight. Somatogravic illusion. The misperception of being  in a nose-up or nose-down attitude, caused by a rapid  acceleration or deceleration while in flight situations that  lack visual reference. Spatial disorientation. The state of confusion due to  misleading information being sent to the brain from various  sensory organs, resulting in a lack of awareness of the aircraft  position in relation to a specific reference point. Special use airspace.  Airspace in which flight activities are  subject to restrictions that can create limitations on the mixed  use of airspace. Consists of prohibited, restricted, warning,  military operations, and alert areas. SRM.  See single-pilot resource management. SSR.  See secondary surveillance radar. SSV.  See standard service volume. Standard holding pattern.  A holding pattern in which all  turns are made to the right. Standard instrument departure procedures (SIDS).  Published procedures to expedite clearance delivery and to  facilitate transition between takeoff and en route operations. Standard rate turn.  A turn in which an aircraft changes its  direction at a rate of 3° per second. The turn indicators are  typically 2 minute or 4 minute instruments. In a 2 minute  instrument, if the needle is one needle width either side of  the center alignment mark, the turn is 3° per second and the  turn takes 2 minutes to execute a 360° turn. In a 4 minute  instrument, the same turn takes two widths deflection of the  needle to achieve 3° per second. The 4 minute turn instrument  is usually found on high performance aircraft. Standard service volume (SSV).  Defines the limits of the  volume of airspace which the VOR serves. Standard terminal arrival route (STAR).  A preplanned  IFR ATC arrival procedure published for pilot use in graphic  and/or textual form. STAR.  See standard terminal arrival route. Static longitudinal stability. The aerodynamic pitching  moments required to return the aircraft to the equilibrium  angle of attack. Static pressure.  Pressure of air that is still, or not moving,  measured perpendicular to the surface of the aircraft. Steep turns.  In instrument flight, any turn greater than standard  rate; in visual flight, anything greater than a 45° bank. Stepdown fix.  The point after which additional descent is  permitted within a segment of an IAP. Strapdown system.  An INS in which the accelerometers  and gyros are permanently “strapped down” or aligned with  the three axes of the aircraft. G-17