NRP.  See National Route Program.  NSA.  See National Security Area.  NTSB.  See National Transportation Safety Board.  NWS.  National Weather Service.  Obstacle departure procedures (ODP).  A preplanned  instrument flight rule (IFR) departure procedure printed for  pilot use in textual or graphic form to provide obstruction  clearance via the least onerous route from the terminal area  to the appropriate en route structure. ODPs are recommended  for obstruction clearance and may be flown without ATC  clearance unless an alternate departure procedure (SID or  radar vector) has been specifically assigned by ATC.  Obstruction lights.  Lights that can be found both on and off  an airport to identify obstructions.  Occluded front.  A frontal occlusion occurs when a fast- moving cold front catches up with a slow moving warm front.  The difference in temperature within each frontal system is  a major factor in determining whether a cold or warm front  occlusion occurs.  ODP.  See obstacle departure procedures.  OM.  Outer marker.  Omission error.  The failure to anticipate significant  instrument indications following attitude changes; for  example, concentrating on pitch control while forgetting  about heading or roll information, resulting in erratic control  of heading and bank.  Optical illusion.  A misleading visual image. For the  purpose of this handbook, the term refers to the brain’s  misinterpretation of features on the ground associated  with landing, which causes a pilot to misread the spatial  relationships between the aircraft and the runway.  Orientation.  Awareness of the position of the aircraft and of  oneself in relation to a specific reference point.  Otolith organ.  An inner ear organ that detects linear  acceleration and gravity orientation.  Outer marker.  A marker beacon at or near the glideslope  intercept altitude of an ILS approach. It is normally located  four to seven miles from the runway threshold on the  extended centerline of the runway.  G-22  Outside air temperature (OAT).  The measured or indicated  air temperature (IAT) corrected for compression and friction  heating. Also referred to as true air temperature.  Overcontrolling.  Using more movement in the control  column than is necessary to achieve the desired pitch-and­ bank condition.  Overboost.  A condition in which a reciprocating engine  has exceeded the maximum manifold pressure allowed by  the manufacturer. Can cause damage to engine components.  Overpower.  To use more power than required for the purpose  of achieving a faster rate of airspeed change.  P-static.  See precipitation static.  PAPI.  See precision approach path indicator.  PAR.  See precision approach radar.  Parallels.  Lines of latitude.  Parasite drag.  Drag caused by the friction of air moving  over the aircraft structure; its amount varies directly with  the airspeed.  Payload (GAMA).  The weight of occupants, cargo, and  baggage.  Personality.  The embodiment of personal traits and  characteristics of an individual that are set at a very early  age and extremely resistant to change.  P-factor.  A tendency for an aircraft to yaw to the left due to  the descending propeller blade on the right producing more  thrust than the ascending blade on the left. This occurs when  the aircraft’s longitudinal axis is in a climbing attitude in  relation to the relative wind. The P-factor would be to the  right if the aircraft had a counterclockwise rotating propeller.  PFD.  See primary flight display.  Phugoid oscillations.  Long-period oscillations of an  aircraft around its lateral axis. It is a slow change in pitch  accompanied by equally slow changes in airspeed. Angle  of attack remains constant, and the pilot often corrects for  phugoid oscillations without even being aware of them.  PIC.  See pilot in command.  Pilotage.  Navigation by visual reference to landmarks.  P  O 