Glossary

The training airplane (Unit 1)

Term	Definition
Fuselage	The central body of the airplane. It houses the cabin, and the wings, empennage, landing gear, and powerplant all attach to it.
Wing	The surface that produces lift. High-wing airplanes like the Cessna 172 mount it above the cabin, braced by struts.
Wing strut	The brace running from the lower fuselage to the underside of each wing, carrying part of the wing's load.
Empennage	The entire tail group: vertical stabilizer, rudder, horizontal stabilizer, and elevator.
Vertical stabilizer	The fixed upright fin on the tail. It keeps the nose pointed into the relative wind. The rudder hinges to its trailing edge.
Rudder	The movable surface hinged to the vertical stabilizer. It yaws the nose left and right.
Horizontal stabilizer	The fixed horizontal surface on the tail. The elevator hinges to its trailing edge.
Elevator	The movable surface hinged to the horizontal stabilizer. It pitches the nose up and down.
Aileron	The movable surface on the outboard trailing edge of each wing. The pair deflects in opposite directions to roll the airplane.
Flap	The movable surface on the inboard trailing edge of each wing. Flaps extend downward together to add lift and drag for slower, steeper approaches.
Landing gear	The wheels and their supporting structure. Two main wheels plus a nose wheel form tricycle gear.
Powerplant	The engine and propeller as a unit.
Propeller	The rotating airfoil driven by the engine. It converts engine power into thrust.
Cowling	The removable cover around the engine. It streamlines the nose and directs cooling air over the engine.
Spinner	The cone-shaped fairing over the propeller hub.
Yoke	The control wheel. Turning it deflects the ailerons; pushing and pulling it deflects the elevator.
Rudder pedals	Foot controls that deflect the rudder in flight and steer the nose wheel on the ground.
Toe brakes	Brakes on the main wheels, applied by pressing the tops of the rudder pedals. Ground use only.
Throttle	The black engine-power knob. In for more power, out for less.
Mixture control	The red knob that sets the engine's fuel-to-air ratio. Full in is rich; pulled all the way out shuts the engine down.
Trim tab	A small hinged tab on the elevator's trailing edge, set by the trim wheel. It holds the elevator in position so the pilot can fly without constant control pressure.
Semi-monocoque	Fuselage construction using frames and stringers under a stressed skin, with the skin carrying much of the load. The standard for modern trainers.
Truss	Fuselage construction using a welded frame of steel tubes, covered by fabric or thin metal that carries little load.
Spar	The main beam inside a wing, running from fuselage toward the tip and carrying most of the wing's bending load.
Rib	A cross-sectional former inside the wing that gives it its curved airfoil shape.
Cantilever wing	A wing supported entirely by its internal structure, with no external strut.
Tricycle gear	Two main wheels plus a steerable nose wheel. The standard trainer arrangement.
Conventional gear	Two main wheels plus a tail wheel; a "taildragger." Requires specific training and an endorsement.
Firewall	The fire-resistant bulkhead separating the engine compartment from the cabin.
Master switch	The red split rocker (BAT/ALT) that powers the electrical system: lights, radios, gauges, and the flap motor on a 172.
Ignition switch	The key switch with positions OFF, R, L, BOTH, and START. It selects which magnetos fire and engages the starter.
Magneto	An engine-driven generator that produces ignition spark independently of the battery. Airplane engines carry two.
Fuel selector	The valve selecting which tank feeds the engine. On a 172: LEFT, RIGHT, or BOTH, with BOTH the normal position.
Carburetor heat	A control on carbureted engines that routes warm air to the carburetor to prevent or clear carburetor ice.

Aerodynamics (Unit 2)

Term	Definition
Lift	The upward aerodynamic force produced as air flows around the wing. It acts perpendicular to the relative wind and opposes weight.
Weight	The combined load of the airplane, crew, fuel, and cargo. It acts downward toward the center of the earth, through the center of gravity, and opposes lift.
Thrust	The forward force produced by the engine and propeller. It acts parallel to the longitudinal axis and opposes drag.
Drag	The rearward force that resists the airplane's movement through the air. It acts parallel to the relative wind and opposes thrust.
Relative wind	The direction of airflow with respect to the wing. It is always parallel to, and opposite, the airplane's flight path.
Angle of attack (AOA)	The angle between the wing's chord line and the relative wind. The pilot's primary control over how much lift the wing makes at a given speed.
Chord line	An imaginary straight line from the leading edge to the trailing edge of the wing's cross section (the airfoil).
Airfoil	The cross-sectional shape of a wing: rounded leading edge, sharp trailing edge, usually more curved on top. Any surface with this shape produces lift when air flows around it.
Leading edge	The rounded front edge of the airfoil, the first part to meet the oncoming air.
Trailing edge	The sharp rear edge of the airfoil, where the upper and lower airflows leave the wing.
Camber	The curvature of an airfoil, measured by how far the mean camber line bows away from the chord line. More camber generally means more lift.
Downwash	The downward deflection of the airflow leaving a lifting wing. Newton's third law pairs it with the upward force on the wing.
Lift coefficient (CL)	The number in the lift equation that captures the airfoil's shape and angle of attack. It rises with AOA until the critical angle, then decreases sharply at the stall.
Venturi	A tube with a constriction in the middle. Air speeds up and its pressure drops in the constriction, the cleanest demonstration of Bernoulli's principle.
Upwash	The airflow diverted upward at the leading edge, flowing over the wing's upper surface.
Center of pressure	The single point through which the total lift force is treated as acting. It moves forward as angle of attack increases and aft as it decreases.
Critical angle of attack	The angle of attack where the coefficient of lift peaks (CLmax). Exceed it and the airflow separates from the upper surface: the stall. It is the same angle regardless of airspeed, attitude, or weight.
Aspect ratio	Wingspan divided by average chord. Higher aspect ratio means more lift for the same drag; gliders run 10 to 30, trainers 6 to 10.
Planform	The shape of the wing viewed from above: elliptical, rectangular, tapered, or a blend. Planform affects efficiency and where the stall begins.
Steady (unaccelerated) flight	Flight at constant airspeed and direction, in which the opposing forces sum to zero: lift equals weight and thrust equals drag.
Parasite drag	All drag not associated with producing lift: the cost of pushing the airplane through the air. It has three types (form, interference, skin friction) and grows with the square of airspeed.
Form drag	The parasite drag due to the airplane's shape and the airflow around it. Streamlining, such as fairings and wheel pants, reduces it.
Interference drag	The parasite drag created where two airstreams meet, as at the wing root. Worst at perpendicular junctions; fairings ease it.
Skin friction drag	The parasite drag of air rubbing along the airplane's surface. Flush rivets, smooth finishes, and a clean, waxed skin reduce it.
Induced drag	The drag that is a byproduct of producing lift. Wingtip vortices tilt the local relative wind downward, leaning the lift vector aft; the rearward component is induced drag. It varies inversely with the square of airspeed, so it dominates in slow flight.
Wingtip vortices	The rotating coils of air trailing each wingtip, formed as the pressure difference drives air from below the wing around the tip toward the low pressure above. They cause induced drag and, behind heavy aircraft, hazardous wake turbulence.
Lift-to-drag ratio (L/D)	The lift produced compared to the drag it costs, a measure of efficiency. Its peak, L/Dmax, occurs at one angle of attack, where total drag is minimum; best glide speed flies the wing there.
Ground effect	The reduction in induced drag within about one wingspan of the surface, where the ground restricts the downwash and wingtip vortices. It makes airplanes float on landing and can let them lift off before they can climb.
Stall	The rapid loss of lift when the wing exceeds its critical angle of attack and the airflow separates from the upper surface. It depends on angle, not on any particular airspeed.
Stall speed (VS)	The airspeed at which, in a given weight and configuration, the wing reaches its critical angle of attack in steady flight. It rises with weight and load factor and falls with flaps extended.
Accelerated stall	A stall that occurs at a higher-than-normal airspeed because increased load factor, as in a steep or abrupt turn, drives the wing to the critical angle sooner.
Load factor	The ratio of the lift the wings produce to the airplane's weight, expressed in Gs. It is 1G in steady level flight and rises with bank and abrupt maneuvering. Stall speed increases with the square root of the load factor.
Angle of incidence	The angle at which the wing is mounted to the fuselage, between the wing chord line and the airplane's longitudinal axis. It is built in by the designer, unlike angle of attack, which changes in flight.
Washout	A built-in twist that sets the wing root at a higher angle of incidence than the tip, so the root reaches the critical angle and stalls first, preserving aileron control.
Stall strip	A small metal strip on the inboard leading edge that trips the airflow at high angle of attack, making the wing root stall before the tip.
Spin	An aggravated stall with yaw that produces autorotation: the airplane descends rapidly in a corkscrew while rotating about a vertical axis. Both wings are stalled, one more deeply than the other.
Autorotation	The self-sustaining rotation of a spin, driven by one wing being more deeply stalled, and so producing less lift and more drag, than the other.
Incipient spin	The first phase of a spin, roughly the first turn or two, before the rotation stabilizes. Most inadvertent spins are stopped here.
Developed spin	The phase in which a spin's rotation rate, airspeed, and vertical descent have settled and hold roughly steady.
Cross-control stall	A stall entered with the controls crossed, aileron one way and rudder the other, as in a skidding turn. It readily drops a wing into a spin and is the classic base-to-final accident.
Center of gravity (CG)	The point through which the airplane's entire weight is treated as acting: its balance point. A body free to rotate always turns about its CG, and loading shifts the CG.
Stability	The airplane's built-in tendency to return to steady flight after a disturbance. It is mostly a design characteristic, described in static and dynamic parts.
Static stability	The airplane's initial tendency the instant it is disturbed: positive (returns toward the original condition), neutral (stays in the new one), or negative (continues away).
Dynamic stability	The airplane's response over time as it oscillates around its original state: positive (oscillations damp out), neutral (they hold steady), or negative (they grow).
Longitudinal axis	The imaginary line running nose to tail through the CG. Motion about it is roll.
Lateral axis	The imaginary line running wingtip to wingtip through the CG. Motion about it is pitch.
Vertical axis	The imaginary line running straight up and down through the CG. Motion about it is yaw.
Longitudinal stability	Stability in pitch, about the lateral axis. It depends on the CG position relative to the wing's center of lift.
Lateral stability	Stability in roll, about the longitudinal axis: the tendency to return to wings-level. Dihedral, keel effect, and sweepback provide it.
Directional stability	Stability in yaw, about the vertical axis: the tendency to weathervane the nose into the relative wind. The vertical fin and aft fuselage provide it.
Dihedral	The upward angle of the wings seen from the front. It provides lateral stability: after a roll, the resulting sideslip raises the angle of attack on the lower wing and rolls the airplane back to level.
Keel effect	The lateral stability a high-wing airplane gets from carrying its weight below the wing, so the fuselage swings back to level like a pendulum.
Dutch roll	A combined rolling and yawing oscillation that appears when lateral stability is stronger than directional stability. Unpleasant enough that designers avoid it, favoring mild spiral instability instead.
Spiral instability	The tendency, when directional stability is stronger than lateral, for an uncorrected bank to slowly tighten into a descending spiral. It develops gradually and, ignored, can wind into a spiral dive.
Limit load factor	The most G an airplane can carry without permanent structural deformation. Beyond it lies the ultimate load, where the structure fails; certification requires a 50 percent margin between the two.
Maneuvering speed (VA)	The speed below which a full, abrupt deflection of a single control stalls the wing before the load factor can exceed the limit load. It is lower at lighter weights and does not protect against repeated or combined control inputs.
Vg diagram	A chart of the airplane's flight envelope, load factor against airspeed. Curved lines mark the stall limit, horizontal lines the limit load factors, and the right edge the never-exceed speed; safe flight stays inside the enclosed area.
Never-exceed speed (VNE)	The redline airspeed beyond which flutter or structural failure can occur. It is the right edge of the Vg diagram.
Rate of turn	How fast the airplane's heading changes, in degrees per second. For a given airspeed it increases with bank angle.
Radius of turn	The size of the circle the airplane traces in a turn. For a given airspeed it shrinks as bank increases, and for a given bank it grows as airspeed increases.
Standard-rate turn	A turn at 3 degrees per second, which completes a 360-degree turn in two minutes. Holding it requires more bank at higher airspeed.
Slipstream	The column of air the propeller accelerates rearward, which washes over the fuselage and tail. Because the blades rotate as they push, it leaves the propeller with a rotational twist.
Torque reaction	The equal and opposite reaction to the engine turning the propeller. With a clockwise propeller it is a left roll about the longitudinal axis, one of the four left-turning tendencies.
Spiraling slipstream	The corkscrew rotation of the propeller slipstream, which wraps around the fuselage and strikes the left side of the vertical fin, yawing the nose left. Strongest at high power and low airspeed.
Gyroscopic precession	The property of a spinning disc by which a force applied to its rim takes effect 90 degrees around the rim, in the direction of rotation. Pitching the propeller disc produces a yaw.
P-factor	Asymmetric propeller loading at high angle of attack: the descending blade meets the air at a greater angle and speed than the ascending blade, making more thrust and yawing the nose left. Also called asymmetric loading.

The engine and propeller (Unit 3)

Term	Definition
Reciprocating engine	An engine that converts the back-and-forth motion of pistons in cylinders into rotation of a crankshaft; the standard light-airplane powerplant.
Four-stroke cycle	The intake, compression, power, exhaust sequence each cylinder repeats, yielding one power stroke per two crankshaft revolutions.
Fixed-pitch propeller	A propeller whose blade angle is set at manufacture; a single compromise between climb and cruise performance. Its power instrument is the tachometer.
Constant-speed propeller	A propeller whose governor adjusts blade angle in flight to hold a selected RPM, keeping the engine at an efficient speed.
Blade angle	The angle between a propeller blade's chord line and its plane of rotation, decreasing from hub to tip so each station meets the air at a useful angle of attack.
Tachometer	The gauge showing crankshaft speed in RPM; on a fixed-pitch installation, the power instrument.
Manifold pressure gauge	The gauge showing the pressure of the fuel-air mixture in the intake manifold; the power-setting instrument on constant-speed installations.
Carburetor	The induction device that meters fuel into the intake air using the pressure drop in a venturi.
Carburetor ice	Ice formed inside the carburetor by fuel vaporization and venturi cooling; most likely below about 70 degrees F in humid air, but possible at outside temperatures as high as 100 degrees F.
Fuel injection	An induction system that meters fuel directly to each cylinder's intake port, eliminating carburetor ice and evening the mixture across cylinders.
Detonation	Uncontrolled, explosive combustion of the fuel-air charge caused by excessive heat, pressure, or fuel of too low a grade.
Preignition	Ignition of the fuel-air charge before the spark, by a hot spot such as a carbon deposit in the cylinder.
Gravity-feed system	A fuel system in which the tanks sit above the engine and fuel flows down to it under its own weight, with no fuel pump required. Standard on high-wing trainers.
Boost pump	An electric fuel pump that supplies fuel pressure for starting and backs up the engine-driven pump; used on low-wing airplanes whose tanks sit below the engine.
Fuel primer	A hand pump that draws fuel from the line and sprays it into the intake to help start a cold engine; locked when not in use to keep it from over-enriching the mixture.
Fuel strainer	A filter at a low point of the fuel system that traps water and sediment before the fuel reaches the engine, and that has a sump drain for sampling.
Sump	A drain at the lowest point of a fuel tank or strainer, sampled before flight so any water, which settles below the fuel, and sediment can be caught and drained off.
Aviation gasoline (avgas)	Piston-engine aviation fuel, dyed by grade so it can be identified by color: 100LL is blue, 80 is red, 100 is green. Jet fuel is colorless to straw and is not used in piston engines.
Leaning	Reducing the fuel in the mixture with the mixture control to match thinner air, restoring the correct fuel-to-air ratio and reducing fuel consumption.
Exhaust gas temperature (EGT) gauge	An instrument reading the temperature of the exhaust gas at the manifold. Because that temperature varies with the fuel-air ratio, it is the reference for leaning the mixture.
Alternator	An engine-driven generator that supplies the airplane's electrical power in flight and recharges the battery.
Voltage regulator	The device that holds the alternator's output a little above battery voltage, so charging current flows into the battery, and keeps system voltage steady as load and engine speed change.
Bus bar	A common conductor where power from the battery and alternator meets and is distributed to every circuit in the airplane.
Circuit breaker	A resettable protective device that opens a circuit when its current exceeds a safe value, isolating a fault before it overheats the wiring. A breaker that reopens after one reset indicates a persistent fault and should be left open.
Ammeter	A center-zero gauge showing whether the battery is charging (plus) or discharging (minus); a full-scale minus indicates alternator failure and a full-scale plus a regulator malfunction.
Loadmeter	A gauge reading from zero upward that shows the total current the alternator is supplying; a drop to zero means the alternator has stopped producing.
Cabin heat	Outside air warmed in a shroud around the exhaust muffler and let into the cabin through a valve. A crack in the exhaust can leak carbon monoxide into this air path.

The pitot-static instruments (Unit 3)

Term	Definition
Pitot tube	A forward-facing probe that senses ram (impact) air pressure plus static pressure for the airspeed indicator; heated electrically to prevent icing.
Static port	A flush opening on the fuselage that senses undisturbed ambient air pressure for the altimeter, VSI, and airspeed indicator.
Alternate static source	A backup static-pressure pickup, usually inside the cabin, selected when the external static ports are blocked. Cabin pressure is slightly lower, so it reads a little high on altitude and airspeed.
Altimeter	The instrument that measures static pressure with a stack of sealed aneroid wafers and displays it as altitude above a set pressure reference.
Altimeter setting	The local pressure, corrected to sea level, dialed into the Kollsman window so the altimeter reads altitude above mean sea level. It is reset from station to station along a route.
Standard atmosphere	The reference atmosphere of 29.92 inches of mercury and 15 degrees Celsius at sea level, with fixed rates of pressure and temperature decrease with altitude.
Indicated altitude	The altitude read directly off the altimeter with the current altimeter setting in the window.
True altitude	The actual height above mean sea level. Airport, terrain, and obstacle elevations on charts are true altitudes.
Absolute altitude	The height above the terrain directly below the airplane, that is, above ground level (AGL).
Pressure altitude	The altitude displayed when 29.92 inches of mercury is set in the window; the height above the standard-pressure level. Used to compute density altitude and true airspeed.
Density altitude	Pressure altitude corrected for nonstandard temperature; the altitude at which the air has the density the airplane is feeling, and the one that governs performance.
Vertical speed indicator (VSI)	The instrument that reads rate of climb or descent by comparing static pressure inside a diaphragm against a case pressure delayed by a calibrated leak. It lags several seconds before the rate is trustworthy.
Airspeed indicator (ASI)	The differential-pressure instrument that reads the difference between the pitot tube's total pressure and static pressure, which is the dynamic pressure, as airspeed.
Indicated airspeed (IAS)	The airspeed read directly off the instrument, uncorrected for installation, instrument, or density error.
Calibrated airspeed (CAS)	Indicated airspeed corrected for installation and instrument error; the correction is largest at low airspeed and high angle of attack.
True airspeed (TAS)	The airplane's actual speed through the air mass. For a given indicated airspeed it exceeds calibrated airspeed by more and more as air density falls with altitude.
Groundspeed (GS)	True airspeed corrected for wind; the airplane's speed over the ground. It decreases with a headwind and increases with a tailwind.
VS0	Stalling speed in the landing configuration, gear and flaps down. It is the lower limit of the white arc on the airspeed indicator.
VS1	Stalling speed in a specified, usually clean, configuration. It is the lower limit of the green arc on the airspeed indicator.
VFE	Maximum flap-extended speed. It is the upper limit of the white arc on the airspeed indicator.
VNO	Maximum structural cruising speed, not to be exceeded except in smooth air. It is the upper limit of the green arc, the top of the yellow caution range.

The gyroscopic instruments and compass (Unit 3)

Term	Definition
Rigidity in space	The property of a spinning gyroscope by which it holds its plane of rotation fixed in space regardless of how its mounting tilts around it. The attitude and heading indicators use it as a steady reference.
Vacuum system	The engine-driven pump, filter, relief valve, and plumbing that draw air through the attitude and heading indicator cases to spin their gyros; the suction gauge shows whether the pump is holding normal suction.
Attitude indicator	The gyroscopic instrument that shows pitch and bank against an artificial horizon; the only instrument that displays the airplane's attitude directly. It works by rigidity in space and is vacuum-driven.
Heading indicator	The gyroscopic instrument that displays heading on a 360-degree card. It has no magnetic sense, so it is set from the compass and reset about every 15 minutes as precession drifts it.
Turn coordinator	The electrically driven gyroscopic instrument whose miniature airplane shows rate of roll and rate of turn, with index marks at the standard rate. It works by controlled precession and shows rate, not angle of bank.
Inclinometer	The ball in a curved fluid-filled tube below the turn coordinator that shows whether the turn is coordinated. The ball to the inside of the turn is a slip, to the outside a skid; step on the ball to center it.
Slip	A turn with too little rudder for the bank: the rate of turn is too slow for the angle of bank, the airplane slides toward the inside of the turn, and the ball falls to the inside.
Skid	A turn with too much rudder for the bank: the rate of turn is too great for the angle of bank, the airplane slides toward the outside of the turn, and the ball rolls to the outside.
Magnetic compass	The self-contained direction instrument: two magnets on a card floating in fluid, read against the lubber line. It requires no electrical, vacuum, or pitot-static power, so it survives their failure.
Lubber line	The fixed vertical reference mark on the compass glass against which the floating card is read to give the heading.
Magnetic variation	The angle between true north and magnetic north at a given location, shown on charts as isogonic lines. It depends on position, not heading; the agonic line joins places where it is zero.
Compass deviation	Compass error caused by magnetic fields within the airplane itself. It depends on heading, not location, and is minimized by a mechanic and recorded on the compass correction card.
Magnetic dip	The downward tilt of the earth's magnetic field toward the surface at higher latitudes. Acting on the compass card when it tilts, it is the cause of the compass's turning and acceleration errors.

Certificates, privileges, and medicals (Unit 4)

Term	Definition
Pilot in command (PIC)	The pilot with final authority and responsibility for the operation and safety of a flight. The PIC decides whether and how the flight is conducted (14 CFR 1.1, 91.3).
Category (airman certificate)	The broad grouping of aircraft named on a pilot certificate, such as airplane, rotorcraft, glider, or lighter-than-air. This is the airman meaning, distinct from an aircraft's own airworthiness category.
Class (airman certificate)	The subdivision within a category on a pilot certificate, such as single-engine land, single-engine sea, multiengine land, or multiengine sea.
Rating	An entry on a certificate that sets the conditions, privileges, or limitations under which it may be exercised, such as an instrument rating or a type rating for a large aircraft.
Endorsement	A flight instructor's signed and dated logbook entry attesting to training received or authorizing an activity, such as solo flight or flying a high-performance airplane. It is recorded in the logbook, not on the certificate.
Medical certificate	The FAA document attesting to a pilot's medical fitness, issued by an aviation medical examiner in first, second, and third class. The class required depends on the privileges being exercised.
Aviation medical examiner (AME)	A physician the FAA designates to examine airmen and issue medical certificates under the standards of 14 CFR Part 67.
BasicMed	An alternative to a third-class medical under 14 CFR Part 68: a valid U.S. driver's license, a physician's comprehensive exam every 48 months, and an online medical course every 24 months, valid for defined private operations.
Solo flight	Flight time during which a student pilot is the sole occupant of the aircraft. It requires a current instructor endorsement, and a student pilot may carry no passengers.
Practical test	The flight test for a certificate or rating, the checkride, given to the Airman Certification Standards by an FAA inspector or a designated pilot examiner.
Flight review	The recurring review required by 14 CFR 61.56: at least one hour of ground training and one hour of flight training with an authorized instructor, completed within the preceding 24 calendar months to act as pilot in command.
Recent flight experience	The takeoffs and landings 14 CFR 61.57 requires within the preceding 90 days before acting as pilot in command with other persons aboard.
Calendar month	A regulatory counting unit that runs to the last day of the month in which it expires, so a requirement met mid-month stays valid through the month's end in the target year.
Logbook	The pilot's record of flight time, training, and endorsements required by 14 CFR 61.51. It must be presented on reasonable request, but a private pilot need not carry it.
Night	By 14 CFR 1.1, the time between the end of evening civil twilight and the beginning of morning civil twilight. Other rules use different night windows for position lights and for currency.
WINGS	The FAA's pilot proficiency program. Completing a phase of it substitutes for a flight review under 14 CFR 61.56.

Airworthiness and maintenance (Unit 4)

Term	Definition
Airworthy	Meeting both conditions for legal flight: conformity to the aircraft's type certificate as modified by approved alterations, and being in condition for safe operation (14 CFR 3.5).
Type certificate	The FAA's approval of an aircraft design. The aircraft must still conform to it, as amended by any approved alteration, in order to be airworthy.
Airworthiness certificate	FAA Form 8100-2, displayed in the aircraft. A standard certificate is valid indefinitely as long as the required maintenance is performed and the aircraft stays registered.
Pilot's Operating Handbook (POH)	The manufacturer's handbook for a specific aircraft, containing the FAA-approved Airplane Flight Manual information. Its Limitations section states the operating limits binding on the pilot.
Placard	A required cockpit marking that states an operating limitation or names an inoperative item, placed at the control or indicator it governs.
Annual inspection	The complete inspection every aircraft needs within the preceding 12 calendar months, signed off by a mechanic holding an inspection authorization (14 CFR 91.409).
100-hour inspection	The inspection required within each 100 hours of time in service when an aircraft is operated for hire or used for flight instruction for hire when the person giving the instruction provides the aircraft. An annual may substitute for it, but not the reverse.
Emergency locator transmitter (ELT)	The crash-activated radio beacon required in most U.S. aircraft by 14 CFR 91.207, inspected every 12 calendar months. Its battery is replaced after one cumulative hour of use or 50 percent of useful life.
Preventive maintenance	The simple tasks listed in Part 43 Appendix A that a certificated pilot who owns or operates the aircraft may perform and must record, such as replacing tires or spark plugs and the strainer and filter work under which the routine oil change is done.
Airworthiness directive (AD)	A legally enforceable FAA rule under Part 39 correcting an unsafe condition in a specific design of aircraft, engine, propeller, or appliance. Compliance is the owner or operator's responsibility.
Minimum equipment list (MEL)	An FAA-approved list, specific to one aircraft, authorizing flight with certain equipment inoperative under stated conditions. Once issued, its use is mandatory for that aircraft.
Special flight permit	A special airworthiness certificate from the FSDO authorizing a specific flight of an aircraft that does not currently meet airworthiness requirements but is safe for the flight, typically to reach a repair facility (14 CFR 21.197).

Operating rules for every flight (Unit 4)

Term	Definition
Right-of-way	The priority the rules give one aircraft to hold its course while every other aircraft involved must give way (14 CFR 91.113).
See and avoid	Every pilot's duty in visual conditions to maintain vigilance and maneuver clear of other aircraft, regardless of the rules the flight operates under (14 CFR 91.113(b)).
Congested area	A built-up area of a city, town, or settlement. The regulations do not fix a boundary, and the FAA reads the term broadly, case by case, when applying the minimum-altitude rules.
Visual flight rules (VFR)	The basic operating rules for flight conducted by outside visual reference. The weather minimums that permit it come with airspace in Unit 5.
Flight level (FL)	An altitude flown with the altimeter set to 29.92 inches of mercury, labeled in hundreds of feet, so FL180 is 18,000 feet. Flight levels are used at and above 18,000 feet MSL (14 CFR 91.121).
Magnetic course	The direction of the aircraft's path over the ground measured from magnetic north. How to compute it comes with navigation in Unit 10.
Hemispheric rule	The 14 CFR 91.159 assignment of VFR cruising altitudes above 3,000 feet AGL: on a magnetic course of 0 through 179 degrees, odd thousands plus 500 feet; on 180 through 359 degrees, even thousands plus 500 feet.
Position lights	The steady red (left wingtip), green (right wingtip), and white (tail) lights, required on from sunset to sunrise (14 CFR 91.209).
Anti-collision lights	The flashing beacon or strobes. On aircraft equipped with them, required for all operations unless the pilot in command judges that safety requires them off (14 CFR 91.209).
Aerobatic flight	An intentional maneuver involving an abrupt change in an aircraft's attitude, an abnormal attitude, or abnormal acceleration not necessary for normal flight (14 CFR 91.303).

Accidents and incidents: NTSB 830 (Unit 4)

Term	Definition
National Transportation Safety Board (NTSB)	The independent federal board that investigates transportation accidents, including civil aviation. Its aircraft accident notification and reporting rules are in 49 CFR Part 830, in Title 49 rather than the FAA's Title 14.
Aircraft accident	An occurrence between the time any person boards an aircraft with the intention of flight and the time all such persons have disembarked, in which any person suffers death or serious injury or the aircraft receives substantial damage (49 CFR 830.2).
Incident	An occurrence other than an accident, associated with the operation of an aircraft, that affects or could affect the safety of operations (49 CFR 830.2). Most incidents require no notification; a listed set of serious incidents does.
Serious injury	An injury that requires more than 48 hours of hospitalization begun within 7 days, fractures any bone except a simple fracture of a finger, toe, or nose, causes severe hemorrhage or nerve, muscle, or tendon damage, involves an internal organ, or involves second- or third-degree burns or burns over more than 5 percent of the body (49 CFR 830.2).
Fatal injury	An injury that results in death within 30 days of the accident (49 CFR 830.2).
Substantial damage	Damage or failure that adversely affects the structural strength, performance, or flight characteristics of an aircraft and normally requires major repair or replacement, with listed exclusions such as dented skin, bent fairings, ground-damaged propeller blades, and landing gear damage (49 CFR 830.2).
Operator	Any person who causes or authorizes the operation of an aircraft, such as the owner, lessee, or bailee. The notification and reporting duties of 49 CFR Part 830 fall on the operator (49 CFR 830.2).
Aviation Safety Reporting System (ASRS)	NASA's voluntary, confidential safety reporting program. The FAA will not use a filed ASRS report for enforcement except for an accident or a criminal offense (14 CFR 91.25).

The airspace system (Unit 5)

Term	Definition
National Airspace System (NAS)	The network of airspace, navigation facilities, airports, air traffic control services, rules, and equipment through which flight in the United States is conducted.
Air traffic control (ATC)	The service operated by the FAA to prevent collisions between aircraft and to organize and expedite the flow of air traffic.
Controlled airspace	Airspace of defined dimensions within which air traffic control service is provided according to the airspace classification. It consists of Classes A, B, C, D, and E (PHAK Ch 15).
Uncontrolled airspace	Airspace in which air traffic control has no authority or responsibility to control air traffic. In the United States this is Class G (AIM 3-3-1).
Special use airspace	Airspace in which certain activities must be confined, or in which limitations are imposed on aircraft operations that are not part of those activities (PHAK Ch 15).
Instrument flight rules (IFR)	The rules governing flight conducted by reference to instruments under an ATC clearance, rather than by outside visual reference. IFR flight in controlled airspace requires a filed flight plan and a clearance (AIM 3-2-1).
ATC clearance	An authorization by air traffic control for an aircraft to proceed under stated conditions within controlled airspace. Class A and Class B require one before entry (14 CFR 91.131, 91.135).
Mean sea level (MSL)	The altitude reference an altimeter indicates when the current reported setting is dialed in. Class A limits, Class B floors and ceilings, and the 14,500-foot Class E layer are all given in feet MSL.
Above ground level (AGL)	A height measured from the surface directly beneath the aircraft. The low Class E floors, at 700 feet and 1,200 feet, are given in feet AGL.
Class A airspace	The airspace from 18,000 feet MSL up to and including FL600, in which all operations are conducted under instrument flight rules and under an ATC clearance (14 CFR 71.33, 91.135). It is not depicted on visual charts.
Class B airspace	Individually tailored, tiered controlled airspace around the nation's busiest airports, generally from the surface to 10,000 feet MSL. Every aircraft needs an ATC clearance to enter (14 CFR 91.131).
Class C airspace	Controlled airspace around an airport with an operational control tower and a radar approach control, usually a 5 NM surface area with a shelf out to 10 NM, entered after establishing two-way radio communications (14 CFR 91.130).
Class D airspace	Controlled airspace around an airport with an operational control tower, generally from the surface to 2,500 feet above the airport elevation, entered after establishing two-way radio communications (14 CFR 91.129).
Class E airspace	All controlled airspace that is not Class A, B, C, or D. Its base may be the surface, 700 feet AGL, 1,200 feet AGL, a charted MSL altitude, or 14,500 feet MSL, and it reaches up to but not including 18,000 feet MSL (14 CFR 71.71).
En route domestic area	A Class E area that provides controlled airspace where en route IFR service is required and the Federal airway system does not reach. Each runs from 1,200 feet above the surface up to the overlying or adjacent controlled airspace, and together they cover most of the land area of the contiguous states (14 CFR 71.71(e)).
Class G airspace	Uncontrolled airspace, meaning airspace not designated as Class A, B, C, D, or E. It extends from the surface to the base of the overlying Class E airspace (AIM 3-3-1).
Vignette	A band of color on a sectional chart, graded from faint on one side to dense on the other, that marks a lateral limit of Class E airspace. The faint side faces the ground whose Class E floor the color states: 700 feet AGL for a magenta band, 1,200 feet AGL for a blue one (FAA Aeronautical Chart Users' Guide).
Two-way radio communications established	The condition reached when a controller answers a pilot's radio call using the aircraft's call sign. It is the entry requirement for Class C and Class D airspace; a reply that omits the call sign does not meet it (AIM 3-2-4).
VOR Federal airway (Victor airway)	A Federal airway based on VOR and VORTAC facilities, identified by the letter V and a number, 8 nautical miles wide. It is Class E airspace from 1,200 feet AGL up to but not including 18,000 feet MSL (14 CFR 71.71(d); AIM 3-2-6, 5-3-4; FAA Order JO 7400.2R, paragraph 20-3-3).
Transponder	An airborne radio that replies to an ATC radar interrogation with a coded reply, so the aircraft appears on the controller's display with an identity attached (14 CFR 91.215).
Mode C	Transponder capability that automatically reports pressure altitude in 100-foot increments along with the assigned code, putting an altitude readout beside the radar target (14 CFR 91.215(b)).
Mode C veil	The airspace within 30 nautical miles of an airport listed in appendix D section 1 to Part 91, from the surface up to 10,000 feet MSL, in which a transponder with altitude reporting and ADS-B Out are required (14 CFR 91.215(b)(2), 91.225(d)(2)).
ADS-B Out	Automatic Dependent Surveillance-Broadcast Out: equipment that broadcasts the aircraft's position, altitude, and velocity, derived from satellite navigation, to ground stations and to other aircraft (14 CFR 91.225).
Flight visibility	The average forward horizontal distance, from the cockpit of an aircraft in flight, at which prominent unlighted objects may be seen and identified by day and prominent lighted objects may be seen and identified by night (14 CFR 1.1). It is the pilot's own determination.
Ground visibility	Prevailing horizontal visibility near the earth's surface as reported by the United States National Weather Service or an accredited observer (14 CFR 1.1). Where an airport reports it, that figure governs basic VFR takeoff, landing, and traffic-pattern entry inside a surface area (14 CFR 91.155(d)).
Ceiling	The height above the earth's surface of the lowest layer of clouds or obscuring phenomena reported as broken, overcast, or obscuration, and not classified as thin or partial (14 CFR 1.1). A scattered layer is not a ceiling.
Statute mile	A distance of 5,280 feet, the unit in which the weather minimums of 14 CFR 91.155 state visibility. A nautical mile is 6,076 feet, so 1 statute mile is 0.87 nautical mile and 3 statute miles is 2.6 nautical miles.
Basic VFR weather minimums	The minimum flight visibility and distance from clouds required for VFR flight, set for each class of airspace and each altitude band by 14 CFR 91.155. A special VFR clearance substitutes lower figures (14 CFR 91.157).
Special VFR	An ATC clearance permitting VFR flight with less than basic VFR minimums, with as little as 1 statute mile of flight visibility and clear of clouds, below 10,000 feet MSL within the upward extension of the lateral boundaries of a surface area (14 CFR 91.157).
Visual meteorological conditions (VMC)	Meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling equal to or better than specified minima (AIM Pilot/Controller Glossary). Because the minima vary with the class of airspace and with altitude, the same weather can be VMC at one altitude and not at another.
Prohibited area	Airspace of defined dimensions within which the flight of aircraft is prohibited, established for security or other reasons associated with the national welfare. No person may operate an aircraft inside one unless the using agency has granted authorization (14 CFR 73.83, 91.133(a)). Charted as P and a number.
Restricted area	Airspace within which the flight of aircraft is not wholly prohibited but is subject to restrictions, because of hazards such as artillery firing, aerial gunnery, or guided missiles. No person may operate inside one between the designated altitudes and during the time of designation without the advance permission of the using or controlling agency (14 CFR 73.13, 91.133(a)). Charted as R and a number.
Warning area	Airspace of defined dimensions extending from three nautical miles outward from the coast of the United States that contains activity hazardous to nonparticipating aircraft. Its purpose is to warn rather than to restrict, and no regulation conditions entry (AIM 3-4-4). Charted as W and a number.
Military operations area (MOA)	Airspace of defined vertical and lateral limits established to separate certain military training activities from IFR traffic. No regulation prohibits a VFR flight from entering an active MOA (AIM 3-4-5). Charted by name rather than by number.
Alert area	Airspace charted to inform nonparticipating pilots that it may contain a high volume of pilot training or an unusual type of aerial activity. All activity inside is conducted in accordance with the regulations without waiver, and participating and transiting pilots are equally responsible for collision avoidance (AIM 3-4-6). Charted as A and a number.
Controlled firing area (CFA)	Special use airspace containing activity that would be hazardous to nonparticipating aircraft if it were not controlled. Its activity is suspended immediately when a spotter aircraft, radar, or ground lookout indicates an aircraft might be approaching, so it is not charted at all (AIM 3-4-7).
Using agency	The agency, organization, or military command whose activity within a restricted area required that area to be designated (14 CFR 73.15(a)), or, for a prohibited area, the agency that established the requirements for it (14 CFR 73.85). It schedules the activity and authorizes transit as feasible (14 CFR 73.15(c)), and it is one of the two authorities whose advance permission lets an aircraft into a restricted area (14 CFR 73.13).
Controlling agency	The FAA facility that may authorize transit through or flight within a restricted area under a joint-use letter (14 CFR 73.17). Its name and frequency appear in the special use airspace tabulation printed in the margin of a sectional chart.
Other airspace areas	A general term referring to the majority of the airspace remaining once controlled, uncontrolled, and special use airspace are accounted for. PHAK Chapter 15 lists fourteen items under it, among them military training routes, temporary flight restrictions, terminal radar service areas, national security areas, published VFR routes, and air defense identification zones.
NOTAM (Notice to Airmen)	A notice carrying time critical aeronautical information that is temporary, that is to be published on aeronautical charts at a later date, or that comes from another operational publication. It is cancelled when its information reaches the chart or the temporary condition returns to normal (AIM 5-1-3).
FDC NOTAM	A NOTAM issued by the Flight Data Center when it is necessary to disseminate regulatory information. Amendments to published instrument approach procedures and to current aeronautical charts arrive this way, and so does every temporary flight restriction (AIM 5-1-3).
Temporary flight restriction (TFR)	A volume of airspace, designated by an FDC NOTAM, in which flight is restricted for a stated reason and a stated period (14 CFR 91.137, 91.138, 91.141, 91.143, 91.145). Only TFRs relating to national security are charted, with a broken blue line; every other one exists solely as the text of its NOTAM.
Military training route (MTR)	A route developed jointly by the FAA and the Department of Defense for low-altitude, high-speed military training, generally established below 10,000 ft MSL for operations above 250 knots. Operations on an IR route are conducted under IFR regardless of weather; operations on a VR route are conducted under VFR. Four number characters mean no segment lies above 1,500 ft AGL (AIM 3-5-2).
Terminal radar service area (TRSA)	An area where participating VFR pilots receive radar service that separates them from IFR traffic. Establishing one was never subject to rulemaking, so a TRSA appears in neither 14 CFR part 71 nor the operating rules of part 91, fits into no airspace class, and participation is voluntary. Its primary airport becomes Class D airspace (AIM 3-5-6; PHAK Ch 15).
National security area (NSA)	Airspace of defined vertical and lateral dimensions established at a location where there is a requirement for increased security and safety of ground facilities. Pilots are requested to avoid flying through one voluntarily, and flight in it may be temporarily prohibited by regulation under 14 CFR 99.7, disseminated by NOTAM (AIM 3-4-8).
Special flight rules area (SFRA)	Airspace of defined dimensions, above land areas or territorial waters, within which the flight of aircraft is subject to the rules set forth in 14 CFR part 93, unless otherwise authorized by air traffic control (AIM 3-5-7).
Air defense identification zone (ADIZ)	An area of airspace over land or water in which the ready identification, location, and control of all aircraft is required in the interest of national security, excepting Department of Defense and law enforcement aircraft (14 CFR 99.3). Zones are designated in subpart B of 14 CFR part 99.
Defense VFR (DVFR)	A flight within an ADIZ conducted in accordance with the visual flight rules of 14 CFR part 91 (14 CFR 99.3). It is flown on a DVFR flight plan, which is filed, activated, and closed with an appropriate aeronautical facility and contains the time and point of ADIZ penetration (14 CFR 99.9(b), 99.11).
VFR flyway	A general flight path, not defined as a specific course, for use in planning flights into, out of, through, or near complex terminal airspace so as to avoid Class B airspace. No ATC clearance is required to fly one, and flyways are depicted on the reverse side of some VFR Terminal Area Charts (AIM 3-5-5).
VFR corridor	Airspace through Class B airspace, with defined vertical and lateral boundaries, in which aircraft may operate without an ATC clearance or communication with air traffic control. A corridor is surrounded on all sides by Class B airspace and does not extend down to the surface (AIM 3-5-5).
Class B VFR transition route	A specific flight course depicted and described on a Terminal Area Chart or a VFR Flyway Planning Chart. Communication with ATC is required where the route transitions Class B, Class C, or Class D airspace, and a clearance is required in addition to operate in Class B airspace (AIM 3-5-5).
Flight service station (FSS)	An air traffic facility which provides pilot briefings, flight plan processing, en route flight advisories, search and rescue services, and assistance to lost aircraft and aircraft in emergency situations. Flight service stations also relay ATC clearances, process NOTAMs, and broadcast aviation weather and aeronautical information (AIM Pilot/Controller Glossary).

Airport operations (Unit 6)

Term	Definition
Traffic pattern	The traffic flow that is prescribed for aircraft landing at, taxiing on, or taking off from an airport. The components of a typical traffic pattern are the departure leg, upwind leg, crosswind leg, downwind leg, base leg, and final approach (Pilot/Controller Glossary).
Common traffic advisory frequency (CTAF)	A frequency designated for the purpose of carrying out airport advisory practices while operating to or from an airport without an operating control tower. The CTAF may be a UNICOM, MULTICOM, flight service station, or tower frequency, and it is identified in appropriate aeronautical publications (Pilot/Controller Glossary).
Wind direction indicator	A wind cone, wind sock, or wind tee installed near the operational runway to indicate wind direction. The large end of the cone or sock, and the cross bar of the tee, points into the wind. The cone and the sock are the same fabric device under two names, and only that device also allows the pilot to estimate wind strength and gust factor (AIM 4-3-4; PHAK Ch 14).
Tetrahedron	The landing direction indicator at an airport, installed when conditions there warrant its use. Its small end points in the direction of landing, and pilots are cautioned against using one for any other purpose, including as an indicator of wind direction. Tower instructions supersede tetrahedron indications (AIM 4-3-4).
Segmented circle	A system of visual indicators designed to provide traffic pattern information at airports without operating control towers (Pilot/Controller Glossary). It gathers the wind direction indicator, the landing direction indicator, the landing strip indicators, and the traffic pattern indicators in one location visible from the air and the ground (AIM 4-3-4).
Traffic pattern indicator	A marker arranged in pairs with the landing strip indicators of a segmented circle, used to indicate the direction of turns where there is a variation from the normal left traffic pattern. Where no segmented circle is installed, traffic pattern indicators may be installed on or near the end of the runway (AIM 4-3-4).
Departure leg	The flight path that begins after takeoff and continues straight ahead along the extended runway centerline. The departure climb continues until reaching a point at least 1/2 mile beyond the departure end of the runway and within 300 feet of the traffic pattern altitude (AIM 4-3-2).
Crosswind leg	A flight path at right angles to the landing runway off its upwind end (Pilot/Controller Glossary).
Downwind leg	A flight path parallel to the landing runway in the direction opposite to landing, normally extending between the crosswind leg and the base leg (Pilot/Controller Glossary). It is flown about 1/2 to 1 mile out from the landing runway (AFH Ch 8).
Base leg	A flight path at right angles to the landing runway off its approach end, normally extending from the downwind leg to the intersection of the extended runway centerline (Pilot/Controller Glossary).
Final approach	A flight path in the direction of landing along the extended runway centerline, normally extending from the base leg to the runway. An aircraft making a straight-in approach under VFR is also considered to be on final approach (Pilot/Controller Glossary).
Upwind leg	A flight path parallel to the landing runway in the direction of landing, separate and distinct from the departure leg, flown at controlled airports and after go-arounds (AC 90-66C Appendix A; AFH Ch 8). The Pilot/Controller Glossary gives the term to a different path: an extension of the departure leg along the extended runway centerline, used when ATC issues control instructions for separation, spacing, or sequencing.
Go-around	A normal maneuver used when the approach and landing parameters deviate from expectations, or when it is hazardous to continue the landing (AFH Ch 9). Unless otherwise advised by ATC, a VFR aircraft should overfly the runway while climbing to traffic pattern altitude and enter the pattern via the crosswind leg (Pilot/Controller Glossary).
Traffic pattern altitude (TPA)	The altitude at which the traffic pattern is flown, published for an airport in the Chart Supplement. Unless a pattern altitude is published there, propeller-driven aircraft enter at 1,000 feet above the airport surface, and large and turbine-powered airplanes at not less than 1,500 feet above the airport elevation or 500 feet above the established pattern altitude (AIM 4-3-3; AC 90-66C Appendix A).
Chart Supplement U.S.	The FAA publication carrying the most comprehensive information on each public-use airport, heliport, and seaplane base, including the traffic pattern altitude and the runways flown with right traffic. It is published in seven volumes organized by region and revised every 56 days (PHAK Ch 14).
Movement area	The runways, taxiways, and other areas of an airport which are utilized for taxiing, takeoff, and landing of aircraft, exclusive of loading ramps and parking areas. At an airport with a tower, specific approval for entry onto the movement area must be obtained from ATC (Pilot/Controller Glossary).
Parallel runways	Two or three runways at one airport laid out in the same direction, distinguished by a letter added to the runway number: 36L for left, 36C for center, and 36R for right (PHAK Ch 14). Two parallel runways take L and R; three take L, C, and R. Runway numbers and letters are determined from the approach direction (AIM 2-3-3).
Runway threshold markings	The white longitudinal stripes that help identify the beginning of the runway that is available for landing. They consist either of eight stripes of uniform dimensions disposed symmetrically about the runway centerline, or of a number of stripes related to the runway width (AIM 2-3-3).
Aiming point marking	Two rectangular markings that serve as a visual aiming point for a landing aircraft. They consist of a broad white stripe located on each side of the runway centerline and approximately 1,000 feet from the landing threshold (AIM 2-3-3).
Touchdown zone markings	Groups of one, two, and three white rectangular bars arranged symmetrically in pairs about the runway centerline. They identify the touchdown zone for landing operations and are coded to provide distance information in 500-foot increments (AIM 2-3-3).
Displaced threshold	A threshold located at a point on the runway other than the designated beginning of the runway. Displacement of a threshold reduces the length of runway available for landings, and the portion of runway behind it is available for takeoffs in either direction and landings from the opposite direction (AIM 2-3-3).
Relocated threshold	A threshold moved toward the rollout end of the runway when construction, maintenance, or other activities require a portion of the runway to be closed. Relocation closes a set portion of the approach end of the runway and also shortens the length of the opposite direction runway (AIM 2-3-3). The closed portion is not available for takeoff or landing, though it is available for taxi (PHAK Ch 14).
Demarcation bar	A 3-foot-wide yellow bar that delineates a runway with a displaced threshold from a blast pad, stopway, or taxiway that precedes the runway. It is yellow because it is not located on the runway (AIM 2-3-3).
Chevrons	Yellow markings used to show pavement areas aligned with the runway that are unusable for landing, takeoff, and taxiing (AIM 2-3-3).
Enhanced taxiway centerline	A parallel line of yellow dashes on either side of the normal taxiway centerline, used for a maximum of 150 feet prior to a runway holding position marking. Its purpose is to warn the pilot that a runway holding position marking is being approached and that the aircraft should be prepared to stop, unless ATC has cleared it onto or across the runway (AIM 2-3-4).
Runway holding position markings	Four yellow lines, two solid and two dashed, spaced six or twelve inches apart and extending across the width of the taxiway or runway, indicating where aircraft must stop when approaching a runway. The solid lines are always on the side where the aircraft must hold (AIM 2-3-5).
Runway holding position sign	A sign with white characters outlined in black on a red background, located where taxiways intersect runways. It is always collocated with the surface painted holding position markings, and its runway numbers are arranged to correspond to the respective runway threshold (PHAK Ch 14; AIM 2-3-8).
Runway safety area (RSA)	A defined surface surrounding the runway prepared, or suitable, for reducing the risk of damage to airplanes in the event of an undershoot, overshoot, or excursion from the runway. Its lateral boundaries are usually identified by the presence of the runway holding position signs and markings on the adjoining taxiway stubs (PHAK Ch 14).
Land and hold short operations (LAHSO)	Operations that include simultaneous takeoffs and landings, or simultaneous landings, when a landing aircraft is able and is instructed by the controller to hold short of an intersecting runway or taxiway, a predetermined point, or an approach or departure flightpath (Pilot/Controller Glossary).
Runway incursion	Any occurrence in the airport runway environment involving an aircraft, vehicle, person, or object on the ground that creates a collision hazard or results in a loss of required separation with an aircraft taking off, intending to take off, landing, or intending to land (PHAK Ch 14).
Hot spot	A location on an airport movement area with a history of potential risk of collision or runway incursion, and where heightened attention by pilots and drivers is necessary (Pilot/Controller Glossary). Hot spots are indicated on the airport diagram with a brown open circle or ellipse leadered to a hot spot number (FAA Aeronautical Chart Users' Guide).