PARASITE DRAG—That part of total drag created by the design or shape of airplane parts. Parasite drag increases with an increase in airspeed.

PAYLOAD (GAMA)—The weight of occupants, cargo, and baggage.

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.

PILOT’S OPERATING HANDBOOK (POH)—A document developed by the airplane manufacturer and contains the FAA-approved Airplane Flight Manual (AFM) information.

PISTON ENGINE—A reciprocating engine.

PITCH—The rotation of an airplane about its lateral axis, or on a propeller, the blade angle as measured from plane of rotation.

PIVOTAL ALTITUDE—A specific altitude at which, when an airplane turns at a given groundspeed, a projecting of the sighting reference line to a selected point on the ground will appear to pivot on that point.

PNEUMATIC SYSTEMS— The power system in an aircraft used for operating such items as landing gear, brakes, and wing flaps with compressed air as the operating fluid.

PORPOISING— Oscillating around the lateral axis of the aircraft during landing.

POSITION LIGHTS—Lights on an aircraft consisting of a red light on the left wing, a green light on the right wing, and a white light on the tail. CFRs require that these lights be displayed in flight from sunset to sunrise.

POSITIVE STATIC STABILITY— The initial tendency to return to a state of equilibrium when disturbed from that state.

POWER DISTRIBUTION BUS— See BUS BAR.

POWER LEVER—The cockpit lever connected to the fuel control unit for scheduling fuel flow to the combustion chambers of a turbine engine.

POWER—Implies work rate or units of work per unit of time, and as such, it is a function of the speed at which the force is developed. The term “power required” is generally associated with reciprocating engines.

POWERPLANT— A complete engine and propeller combination with accessories.

PRACTICAL SLIP LIMIT—The maximum slip an aircraft is capable of performing due to rudder travel limits.

PRECESSION—The tilting or turning of a gyro in response to deflective forces causing slow drifting and erroneous indications in gyroscopic instruments.

PREIGNITION—Ignition occurring in the cylinder before the time of normal ignition. Preignition is often caused by a local hot spot in the combustion chamber igniting the fuel/air mixture.

PRESSURE ALTITUDE— The altitude indicated when the altimeter setting window (barometric scale) is adjusted to 29.92. This is the altitude above the standard datum plane, which is a theoretical plane where air pressure (corrected to 15ºC) equals 29.92 in. Hg. Pressure altitude is used to compute density altitude, true altitude, true airspeed, and other performance data.

PROFILE DRAG—The total of the skin friction drag and form drag for a two-dimensional airfoil section.

PROPELLER BLADE ANGLE— The angle between the propeller chord and the propeller plane of rotation.

PROPELLER LEVER— The control on a free power turbine turboprop that controls propeller speed and the selection for propeller feathering.

PROPELLER SLIPSTREAM— The volume of air accelerated behind a propeller producing thrust.

PROPELLER SYNCHRONIZATION— A condition in which all of the propellers have their pitch automatically adjusted to maintain a constant r.p.m. among all of the engines of a multiengine aircraft.

PROPELLER—A device for propelling an aircraft that, when rotated, produces by its action on the air, a thrust approximately perpendicular to its plane of rotation. It includes the control components normally supplied by its manufacturer.