KIAS. Knots indicated airspeed. Knot. The knot is a unit of speed equal to one nautical mile (1.852 km) per hour, approximately 1.151 mph. Kollsman window. A barometric scale window of a sensitive altimeter used to adjust the altitude for the altimeter setting. L LAAS. See local area augmentation system. Lag. The delay that occurs before an instrument needle attains a stable indication. Land breeze. A coastal breeze flowing from land to sea caused by temperature differences when the sea surface is warmer than the adjacent land. The land breeze usually occurs at night and alternates with the sea breeze that blows in the opposite direction by day. Land as soon as possible. Land without delay at the nearest suitable area, such as an open field, at which a safe approach and landing is assured. Land as soon as practical. The landing site and duration of flight are at the discretion of the pilot. Extended flight beyond the nearest approved landing area is not recommended. Land immediately. The urgency of the landing is paramount. The primary consideration is to ensure the survival of the occupants. Landing in trees, water, or other unsafe areas should be considered only as a last resort. Lateral axis. An imaginary line passing through the center of gravity of an airplane and extending across the airplane from wingtip to wingtip. Lateral stability (rolling). The stability about the longitudinal axis of an aircraft. Rolling stability or the ability of an airplane to return to level flight due to a disturbance that causes one of the wings to drop. Latitude. Measurement north or south of the equator in degrees, minutes, and seconds. Lines of latitude are also referred to as parallels. LDA. See localizer-type directional aid. Lead radial. The radial at which the turn from the DME arc to the inbound course is started. Leading edge. The part of an airfoil that meets the airflow first. Leading edge devices. High lift devices which are found on the leading edge of the airfoil. The most common types are fixed slots, movable slats, and leading edge flaps. Leading-edge flap. A portion of the leading edge of an airplane wing that folds downward to increase the camber, lift, and drag of the wing. The leading-edge flaps are extended for takeoffs and landings to increase the amount of aerodynamic lift that is produced at any given airspeed. Leans, the. A physical sensation caused by an abrupt correction of a banked attitude entered too slowly to stimulate the motion sensing system in the inner ear. The abrupt correction can create the illusion of banking in the opposite direction. Licensed empty weight. The empty weight that consists of the airframe, engine(s), unusable fuel, and undrainable oil plus standard and optional equipment as specified in the equipment list. Some manufacturers used this term prior to GAMA standardization. Lift. A component of the total aerodynamic force on an airfoil and acts perpendicular to the relative wind. Limit load factor. Amount of stress, or load factor, that an aircraft can withstand before structural damage or failure occurs. Lines of flux. Invisible lines of magnetic force passing between the poles of a magnet. L/MF. See low or medium frequency. LMM. See locator middle marker. G-18 Load factor. The ratio of a specified load to the total weight of the aircraft. The specified load is expressed in terms of any of the following: aerodynamic forces, inertial forces, or ground or water reactions. Loadmeter. A type of ammeter installed between the generator output and the main bus in an aircraft electrical system. LOC. See localizer. Local area augmentation system (LAAS). A differential global positioning system (DGPS) that improves the accuracy of the system by determining position error from the GPS satellites, then transmitting the error, or corrective factors, to the airborne GPS receiver. Localizer (LOC). The portion of an ILS that gives left/right guidance information down the centerline of the instrument runway for final approach. Localizer-type directional aid (LDA). A NAVAID used for nonprecision instrument approaches with utility and accuracy comparable to a localizer but which is not a part of a complete ILS and is not aligned with the runway. Some LDAs are equipped with a glideslope. Locator middle marker (LMM). Nondirectional radio beacon (NDB) compass locator, collocated with a middle marker (MM). Locator outer marker (LOM). NDB compass locator, collocated with an outer marker (OM). LOM. See locator outer marker. Longitude. Measurement east or west of the Prime Meridian in degrees, minutes, and seconds. The Prime Meridian is 0° longitude and runs through Greenwich, England. Lines of longitude are also referred to as meridians. Longitudinal axis. An imaginary line through an aircraft from nose to tail, passing through its center of gravity. The longitudinal axis is also called the roll axis of the aircraft. Movement of the ailerons rotates an airplane about its longitudinal axis. Longitudinal stability (pitching). Stability about the lateral axis. A desirable characteristic of an airplane whereby it tends to return to its trimmed angle of attack after displacement. Low or medium frequency. A frequency range between 190 and 535 kHz with the medium frequency above 300 kHz. Generally associated with nondirectional beacons transmitting a continuous carrier with either a 400 or 1,020 Hz modulation. Lubber line. The reference line used in a magnetic compass or heading indicator. M MAA. See maximum authorized altitude. MAC. See mean aerodynamic chord. Mach number. The ratio of the true airspeed of the aircraft to the speed of sound in the same atmospheric conditions, named in honor of Ernst Mach, late 19th century physicist. Mach meter. The instrument that displays the ratio of the speed of sound to the true airspeed an aircraft is flying. Magnetic bearing (MB). The direction to or from a radio transmitting station measured relative to magnetic north. Magnetic compass. A device for determining direction measured from magnetic north. Magnetic dip. A vertical attraction between a compass needle and the magnetic poles. The closer the aircraft is to a pole, the more severe the effect. Magnetic heading (MH). The direction an aircraft is pointed with respect to magnetic north. Magneto. A self-contained, engine-driven unit that supplies electrical current to the spark plugs; completely independent of the airplane’s electrical system. Normally there are two magnetos per engine. Magnus effect. Lifting force produced when a rotating cylinder produces a pressure differential. This is the same effect that makes a baseball curve or a golf ball slice. Mandatory altitude. An altitude depicted on an instrument approach chart with the altitude value both underscored and overscored. Aircraft are required to maintain altitude at the depicted value. Mandatory block altitude. An altitude depicted on an instrument approach chart with two underscored and overscored altitude values between which aircraft are required to maintain altitude. G-19 Maneuverability. Ability of an aircraft to change directions along a flight path and withstand the stresses imposed upon it. Maneuvering speed (VA). The design maneuvering speed. Operating at or below design maneuvering speed does not provide structural protection against multiple full control inputs in one axis or full control inputs in more than one axis at the same time. Manifold absolute pressure. The absolute pressure of the fuel/air mixture within the intake manifold, usually indicated in inches of mercury. MAP. See missed approach point. Margin identification. The top and bottom areas on an instrument approach chart that depict information about the procedure, including airport location and procedure identification. Marker beacon. A low-powered transmitter that directs its signal upward in a small, fan-shaped pattern. Used along the flight path when approaching an airport for landing, marker beacons indicate both aurally and visually when the aircraft is directly over the facility. Mass. The amount of matter in a body. Maximum altitude. An altitude depicted on an instrument approach chart with overscored altitude value at which or below aircraft are required to maintain altitude. Maximum authorized altitude (MAA). A published altitude representing the maximum usable altitude or flight level for an airspace structure or route segment. Maximum landing weight. The greatest weight that an airplane normally is allowed to have at landing. Maximum ramp weight. The total weight of a loaded aircraft, including all fuel. It is greater than the takeoff weight due to the fuel that will be burned during the taxi and runup operations. Ramp weight may also be referred to as taxi weight. Maximum takeoff weight. The maximum allowable weight for takeoff. Maximum weight. The maximum authorized weight of the aircraft and all of its equipment as specified in the Type Certificate Data Sheets (TCDS) for the aircraft. Maximum zero fuel weight (GAMA). The maximum weight, exclusive of usable fuel. MB. See magnetic bearing. MCA. See minimum crossing altitude. MDA. See minimum descent altitude. MEA. See minimum en route altitude. Mean aerodynamic chord (MAC). The average distance from the leading edge to the trailing edge of the wing. Mean sea level. The average height of the surface of the sea at a particular location for all stages of the tide over a 19-year period. MEL. See minimum equipment list. Meridians. Lines of longitude. Mesophere. A layer of the atmosphere directly above the stratosphere. METAR. See Aviation Routine Weather Report. MFD. See multi-function display. MH. See magnetic heading. MHz. Megahertz. Microburts. A strong downdraft which normally occurs over horizontal distances of 1 NM or less and vertical distances of less than 1,000 feet. In spite of its small horizontal scale, an intense microburst could induce windspeeds greater than 100 knots and downdrafts as strong as 6,000 feet per minute. Microwave landing system (MLS). A precision instrument approach system operating in the microwave spectrum which normally consists of an azimuth station, elevation station, and precision distance measuring equipment. Mileage breakdown. A fix indicating a course change that appears on the chart as an “x” at a break between two segments of a federal airway. Military operations area (MOA). Airspace established for the purpose of separating certain military training activities from IFR traffic. G-20 Military training route (MTR). Airspace of defined vertical and lateral dimensions established for the conduct of military training at airspeeds in excess of 250 knots indicated airspeed (KIAS). Minimum altitude. An altitude depicted on an instrument approach chart with the altitude value underscored. Aircraft are required to maintain altitude at or above the depicted value. Minimum crossing altitude (MCA). The lowest allowed altitude at certain fixes an aircraft must cross when proceeding in the direction of a higher minimum en route altitude (MEA). Minimum descent altitude (MDA). The lowest altitude (in feet MSL) to which descent is authorized on final approach, or during circle-to-land maneuvering in execution of a nonprecision approach. Minimum drag. The point on the total drag curve where the lift-to-drag ratio is the greatest. At this speed, total drag is minimized. Minimum en route altitude (MEA). The lowest published altitude between radio fixes that ensures acceptable navigational signal coverage and meets obstacle clearance requirements between those fixes. Minimum equipment list (MEL). A list developed for larger aircraft that outlines equipment that can be inoperative for various types of flight including IFR and icing conditions. This list is based on the master minimum equipment list (MMEL) developed by the FAA and must be approved by the FAA for use. It is specific to an individual aircraft make and model. Minimum obstruction clearance altitude (MOCA). The lowest published altitude in effect between radio fixes on VOR airways, off-airway routes, or route segments, which meets obstacle clearance requirements for the entire route segment and which ensures acceptable navigational signal coverage only within 25 statute (22 nautical) miles of a VOR. Minimum reception altitude (MRA). The lowest altitude at which an airway intersection can be determined. Minimum safe altitude (MSA). The minimum altitude depicted on approach charts which provides at least 1,000 feet of obstacle clearance for emergency use within a specified distance from the listed navigation facility. Minimum vectoring altitude (MVA). An IFR altitude lower than the minimum en route altitude (MEA) that provides terrain and obstacle clearance. Minimums section. The area on an IAP chart that displays the lowest altitude and visibility requirements for the approach. Missed approach. A maneuver conducted by a pilot when an instrument approach cannot be completed to a landing. Missed approach point (MAP). A point prescribed in each instrument approach at which a missed approach procedure shall be executed if the required visual reference has not been established. Mixed ice. A mixture of clear ice and rime ice. MLS. See microwave landing system. MM. Middle marker. MOA. See military operations area. MOCA. See minimum obstruction clearance altitude. Mode C. Altitude reporting transponder mode. Moment. The product of the weight of an item multiplied by its arm. Moments are expressed in pound-inches (lb-in). Total moment is the weight of the airplane multiplied by the distance between the datum and the CG. Moment arm. The distance from a datum to the applied force. Moment index (or index). A moment divided by a constant such as 100, 1,000, or 10,000. The purpose of using a moment index is to simplify weight and balance computations of airplanes where heavy items and long arms result in large, unmanageable numbers. Monocoque. A shell-like fuselage design in which the stressed outer skin is used to support the majority of imposed stresses. Monocoque fuselage design may include bulkheads but not stringers. Monoplanes. Airplanes with a single set of wings. Movable slat. A movable auxiliary airfoil on the leading edge of a wing. It is closed in normal flight but extends at high angles of attack. This allows air to continue flowing over the top of the wing and delays airflow separation. MRA. See minimum reception altitude. MSA. See minimum safe altitude. MSL. See mean sea level. G-21 MTR. See military training route. Multi-function display (MFD). Small screen (CRT or LCD) in an aircraft that can be used to display information to the pilot in numerous configurable ways. Often an MFD will be used in concert with a primary flight display. MVA. See minimum vectoring altitude. N N1. Rotational speed of the low pressure compressor in a turbine engine. N2. Rotational speed of the high pressure compressor in a turbine engine. Nacelle. A streamlined enclosure on an aircraft in which an engine is mounted. On multiengine propeller-driven airplanes, the nacelle is normally mounted on the leading edge of the wing. NACG. See National Aeronautical Charting Group. NAS. See National Airspace System. National Airspace System (NAS). The common network of United States airspace—air navigation facilities, equipment and services, airports or landing areas; aeronautical charts, information and services; rules, regulations and procedures, technical information; and manpower and material. National Aeronautical Charting Group (NACG). A Federal agency operating under the FAA, responsible for publishing charts such as the terminal procedures and en route charts. National Route Program (NRP). A set of rules and procedures designed to increase the flexibility of user flight planning within published guidelines. National Security Area (NSA). Areas consisting of airspace of defined vertical and lateral dimensions established at locations where there is a requirement for increased security and safety of ground facilities. Pilots are requested to voluntarily avoid flying through the depicted NSA. When it is necessary to provide a greater level of security and safety, flight in NSAs may be temporarily prohibited. Regulatory prohibitions are disseminated via NOTAMs. National Transportation Safety Board (NTSB). A United States Government independent organization responsible for investigations of accidents involving aviation, highways, waterways, pipelines, and railroads in the United States. NTSB is charged by congress to investigate every civil aviation accident in the United States. NAVAID. Navigational aid. NAV/COM. Navigation and communication radio. NDB. See nondirectional radio beacon. Negative static stability. The initial tendency of an aircraft to continue away from the original state of equilibrium after being disturbed. Neutral static stability. The initial tendency of an aircraft to remain in a new condition after its equilibrium has been disturbed. NM. Nautical mile. NOAA. National Oceanic and Atmospheric Administration. No-gyro approach. A radar approach that may be used in case of a malfunctioning gyro-compass or directional gyro. Instead of providing the pilot with headings to be flown, the controller observes the radar track and issues control instructions “turn right/left” or “stop turn,” as appropriate. Nondirectional radio beacon (NDB). A ground-based radio transmitter that transmits radio energy in all directions. Nonprecision approach. A standard instrument approach procedure in which only horizontal guidance is provided. No procedure turn (NoPT). Term used with the appropriate course and altitude to denote that the procedure turn is not required. NoPT. See no procedure turn. NOTAM. See Notice to Airmen. Notice to Airmen (NOTAM). A notice filed with an aviation authority to alert aircraft pilots of any hazards en route or at a specific location. The authority in turn provides means of disseminating relevant NOTAMs to pilots. G-22 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 fastmoving 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-andbank 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. G-23 Pilot in command (PIC). The pilot responsible for the operation and safety of an aircraft. Pilot report (PIREP). Report of meteorological phenomena encountered by aircraft. Pilot’s Operating Handbook/Airplane Flight Manual (POH/AFM). FAA-approved documents published by the airframe manufacturer that list the operating conditions for a particular model of aircraft. PIREP. See pilot report. Pitot pressure. Ram air pressure used to measure airspeed. Pitot-static head. A combination pickup used to sample pitot pressure and static air pressure. Plan view. The overhead view of an approach procedure on an instrument approach chart. The plan view depicts the routes that guide the pilot from the en route segments to the IAF. Planform. The shape or form of a wing as viewed from above. It may be long and tapered, short and rectangular, or various other shapes. Pneumatic. Operation by the use of compressed air. POH/AFM. See Pilot’s Operating Handbook/Airplane Flight Manual. Point-in-space approach. A type of helicopter instrument approach procedure to a missed approach point more than 2,600 feet from an associated helicopter landing area. Poor judgment chain. A series of mistakes that may lead to an accident or incident. Two basic principles generally associated with the creation of a poor judgment chain are: (1) one bad decision often leads to another; and (2) as a string of bad decisions grows, it reduces the number of subsequent alternatives for continued safe flight. ADM is intended to break the poor judgment chain before it can cause an accident or incident. Position error. Error in the indication of the altimeter, ASI, and VSI caused by the air at the static system entrance not being absolutely still. Position report. A report over a known location as transmitted by an aircraft to ATC. Positive static stability. The initial tendency to return to a state of equilibrium when disturbed from that state. 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. Precession. The characteristic of a gyroscope that causes an applied force to be felt, not at the point of application, but 90° from that point in the direction of rotation. Precipitation. Any or all forms of water particles (rain, sleet, hail, or snow) that fall from the atmosphere and reach the surface. Precipitation static (P-static). A form of radio interference caused by rain, snow, or dust particles hitting the antenna and inducing a small radio-frequency voltage into it. Precision approach. A standard instrument approach procedure in which both vertical and horizontal guidance is provided. Precision approach path indicator (PAPI). A system of lights similar to the VASI, but consisting of one row of lights in two- or four-light systems. A pilot on the correct glideslope will see two white lights and two red lights. See VASI. Precision approach radar (PAR). A type of radar used at an airport to guide an aircraft through the final stages of landing, providing horizontal and vertical guidance. The radar operator directs the pilot to change heading or adjust the descent rate to keep the aircraft on a path that allows it to touch down at the correct spot on the runway. Precision runway monitor (PRM). System allows simultaneous, independent instrument flight rules (IFR) approaches at airports with closely spaced parallel runways. Preferred IFR routes. Routes established in the major terminal and en route environments to increase system efficiency and capacity. IFR clearances are issued based on these routes, listed in the Chart Supplement U.S. except when severe weather avoidance procedures or other factors dictate otherwise. 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. Altitude above the standard 29.92 "Hg plane. G-24 Pressure demand oxygen system. A demand oxygen system that supplies 100 percent oxygen at sufficient pressure above the altitude where normal breathing is adequate. Also referred to as a pressure breathing system. Prevailing visibility. The greatest horizontal visibility equaled or exceeded throughout at least half the horizon circle (which is not necessarily continuous). Preventive maintenance. Simple or minor preservative operations and the replacement of small standard parts not involving complex assembly operation as listed in 14 CFR part 43, appendix A. Certificated pilots may perform preventive maintenance on any aircraft that is owned or operated by them provided that the aircraft is not used in air carrier service. Primary and supporting. A method of attitude instrument flying using the instrument that provides the most direct indication of attitude and performance. Primary flight display (PFD). A display that provides increased situational awareness to the pilot by replacing the traditional six instruments used for instrument flight with an easy-to-scan display that provides the horizon, airspeed, altitude, vertical speed, trend, trim, and rate of turn among other key relevant indications. PRM. See precision runway monitor. Procedure turn. A maneuver prescribed when it is necessary to reverse direction to establish an aircraft on the intermediate approach segment or final approach course. Profile view. Side view of an IAP chart illustrating the vertical approach path altitudes, headings, distances, and fixes. Prohibited area. Designated airspace within which flight of aircraft is prohibited. 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. Propeller/rotor modulation error. Certain propeller rpm settings or helicopter rotor speeds can cause the VOR course deviation indicator (CDI) to fluctuate as much as ±6°. Slight changes to the rpm setting will normally smooth