NRP.  See National Route Program. 

NSA.  See National Security Area. 

NTSB. See National Transportation Safety Board. 

NWS.  National Weather Service. 

## O 

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. 

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 

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. 

