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glossary

100-HOUR INSPECTION¡ª<BR>An inspection, identical in scope to an<BR>annual inspection. Must be conducted<BR>every 100 hours of flight on aircraft of<BR>under 12,500 pounds that are used<BR>for hire.<BR>ABSOLUTE ALTITUDE¡ª<BR>The vertical distance of an airplane<BR>above the terrain, or above ground<BR>level (AGL).<BR>ABSOLUTE CEILING¡ª<BR>The altitude at which a climb is no<BR>longer possible.<BR>ACCELERATE-GO DISTANCE¡ª<BR>The distance required to accelerate to<BR>V1 with all engines at takeoff power,<BR>experience an engine failure at V1 and<BR>continue the takeoff on the remaining<BR>engine(s). The runway required<BR>includes the distance required to<BR>climb to 35 feet by which time V2<BR>speed must be attained.<BR>ACCELERATE-STOP<BR>DISTANCE¡ªThe distance required<BR>to accelerate to V1 with all engines at<BR>takeoff power, experience an engine<BR>failure at V1, and abort the takeoff and<BR>bring the airplane to a stop using braking<BR>action only (use of thrust reversing<BR>is not considered).<BR>ACCELERATION¡ªForce involved<BR>in overcoming inertia, and which may<BR>be defined as a change in velocity per<BR>unit of time.<BR>ACCESSORIES¡ªComponents that<BR>are used with an engine, but are not a<BR>part of the engine itself. Units such as<BR>magnetos, carburetors, generators,<BR>and fuel pumps are commonly<BR>installed engine accessories.<BR>ADJUSTABLE STABILIZER¡ª<BR>A stabilizer that can be adjusted in<BR>flight to trim the airplane, thereby<BR>even a trim tab, which provides<BR>aerodynamic force when it interacts<BR>with a moving stream of air.<BR>AIRMANSHIP SKILLS¡ªThe skills<BR>of coordination, timing, control touch,<BR>and speed sense in addition to the<BR>motor skills required to fly an aircraft.<BR>AIRMANSHIP¡ª<BR>A sound acquaintance with the<BR>principles of flight, the ability to<BR>operate an airplane with competence<BR>and precision both on the ground and<BR>in the air, and the exercise of sound<BR>judgment that results in optimal<BR>operational safety and efficiency.<BR>AIRPLANE FLIGHT MANUAL<BR>(AFM)¡ªA document developed by<BR>the airplane manufacturer and<BR>approved by the Federal Aviation<BR>Administration (FAA). It is specific to<BR>a particular make and model airplane<BR>by serial number and it contains<BR>operating procedures and limitations.<BR>AIRPLANE OWNER/<BR>INFORMATION MANUAL¡ªA<BR>document developed by the airplane<BR>manufacturer containing general<BR>information about the make and<BR>model of an airplane. The airplane<BR>owner¡¯s manual is not FAA-approved<BR>and is not specific to a particular serial<BR>numbered airplane. This manual is not<BR>kept current, and therefore cannot be<BR>substituted for the AFM/POH.<BR>AIRPORT/FACILITY<BR>DIRECTORY¡ª<BR>A publication designed primarily as a<BR>pilot¡¯s operational manual containing<BR>all airports, seaplane bases, and<BR>heliports open to the public including<BR>communications data, navigational<BR>facilities, and certain special notices<BR>and procedures. This publication is<BR>issued in seven volumes according to<BR>geographical area.<BR>allowing the airplane to fly hands-off<BR>at any given airspeed.<BR>ADVERSE YAW¡ªA condition of<BR>flight in which the nose of an airplane<BR>tends to yaw toward the outside of the<BR>turn. This is caused by the higher<BR>induced drag on the outside wing,<BR>which is also producing more lift.<BR>Induced drag is a by-product of the lift<BR>associated with the outside wing.<BR>AERODYNAMIC CEILING¡ª<BR>The point (altitude) at which, as the<BR>indicated airspeed decreases with altitude,<BR>it progressively merges with the<BR>low speed buffet boundary where prestall<BR>buffet occurs for the airplane at a<BR>load factor of 1.0 G.<BR>AERODYNAMICS¡ªThe science of<BR>the action of air on an object, and with<BR>the motion of air on other gases.<BR>Aerodynamics deals with the<BR>production of lift by the aircraft, the<BR>relative wind, and the atmosphere.<BR>AILERONS¡ªPrimary flight control<BR>surfaces mounted on the trailing edge<BR>of an airplane wing, near the tip.<BR>Ailerons control roll about the longitudinal<BR>axis.<BR>AIR START¡ªThe act or instance of<BR>starting an aircraft¡¯s engine while in<BR>flight, especially a jet engine after<BR>flameout.<BR>AIRCRAFT LOGBOOKS¡ª<BR>Journals containing a record of total<BR>operating time, repairs, alterations or<BR>inspections performed, and all<BR>Airworthiness Directive (AD) notes<BR>complied with. A maintenance<BR>logbook should be kept for the<BR>airframe, each engine, and each<BR>propeller.<BR>AIRFOIL¡ªAn airfoil is any surface,<BR>such as a wing, propeller, rudder, or<BR>G-1<BR>Glossary.qxd 5/7/04 10:46 AM Page G-1<BR>G-2<BR>AIRWORTHINESS¡ªA condition<BR>in which the aircraft conforms to its<BR>type certificated design including<BR>supplemental type certificates, and<BR>field approved alterations. The<BR>aircraft must also be in a condition for<BR>safe flight as determined by annual,<BR>100 hour, preflight and any other<BR>required inspections.<BR>AIRWORTHINESS<BR>CERTIFICATE¡ª<BR>A certificate issued by the FAA to all<BR>aircraft that have been proven to meet<BR>the minimum standards set down by<BR>the Code of Federal Regulations.<BR>AIRWORTHINESS<BR>DIRECTIVE¡ªA regulatory notice<BR>sent out by the FAA to the registered<BR>owner of an aircraft informing the<BR>owner of a condition that prevents the<BR>aircraft from continuing to meet<BR>its conditions for airworthiness.<BR>Airworthiness Directives (AD notes)<BR>must be complied with within the<BR>required time limit, and the fact of<BR>compliance, the date of compliance,<BR>and the method of compliance must be<BR>recorded in the aircraft¡¯s maintenance<BR>records.<BR>ALPHA MODE OF<BR>OPERATION¡ªThe operation of a<BR>turboprop engine that includes all of<BR>the flight operations, from takeoff to<BR>landing. Alpha operation is typically<BR>between 95 percent to 100 percent of<BR>the engine operating speed.<BR>ALTERNATE AIR¡ªA device<BR>which opens, either automatically<BR>or manually, to allow induction airflow<BR>to continue should the primary<BR>induction air opening become<BR>blocked.<BR>ALTERNATE STATIC SOURCE¡ª<BR>A manual port that when opened<BR>allows the pitot static instruments to<BR>sense static pressure from an alternate<BR>location should the primary static port<BR>become blocked.<BR>ALTERNATOR/GENERATOR¡ªA<BR>device that uses engine power to generate<BR>electrical power.<BR>ALTIMETER¡ªA flight instrument<BR>that indicates altitude by sensing<BR>pressure changes.<BR>pitch, which is the up and down<BR>movement of the airplane¡¯s nose.<BR>ATTITUDE¡ª The position of an<BR>aircraft as determined by the<BR>relationship of its axes and a reference,<BR>usually the earth¡¯s horizon.<BR>AUTOKINESIS¡ªThis is caused by<BR>staring at a single point of light<BR>against a dark background for more<BR>than a few seconds. After a few<BR>moments, the light appears to move<BR>on its own.<BR>AUTOPILOT¡ªAn automatic flight<BR>control system which keeps an aircraft<BR>in level flight or on a set course.<BR>Automatic pilots can be directed by<BR>the pilot, or they may be coupled to a<BR>radio navigation signal.<BR>AXES OF AN AIRCRAFT¡ªThree<BR>imaginary lines that pass through an<BR>aircraft¡¯s center of gravity. The axes<BR>can be considered as imaginary axles<BR>around which the aircraft turns. The<BR>three axes pass through the center of<BR>gravity at 90¡ã angles to each other.<BR>The axis from nose to tail is the<BR>longitudinal axis, the axis that passes<BR>from wingtip to wingtip is the lateral<BR>axis, and the axis that passes vertically<BR>through the center of gravity is the<BR>vertical axis.<BR>AXIAL FLOW COMPRESSOR¡ª<BR>Atype of compressor used in a turbine<BR>engine in which the airflow through<BR>the compressor is essentially linear.<BR>An axial-flow compressor is made up<BR>of several stages of alternate rotors<BR>and stators. The compressor ratio is<BR>determined by the decrease in area of<BR>the succeeding stages.<BR>BACK SIDE OF THE POWER<BR>CURVE¡ª Flight regime in which<BR>flight at a higher airspeed requires a<BR>lower power setting and a lower<BR>airspeed requires a higher power<BR>setting in order to maintain altitude.<BR>BALKED LANDING¡ª<BR>A go-around.<BR>BALLAST¡ªRemovable or permanently<BR>installed weight in an aircraft<BR>ALTITUDE (AGL)¡ªThe actual<BR>height above ground level (AGL) at<BR>which the aircraft is flying.<BR>ALTITUDE (MSL)¡ªThe actual<BR>height above mean sea level (MSL) at<BR>which the aircraft is flying.<BR>ALTITUDE CHAMBER¡ªA device<BR>that simulates high altitude conditions<BR>by reducing the interior pressure. The<BR>occupants will suffer from the same<BR>physiological conditions as flight at<BR>high altitude in an unpressurized<BR>aircraft.<BR>ALTITUDE ENGINE¡ª<BR>A reciprocating aircraft engine having<BR>a rated takeoff power that is<BR>producible from sea level to an<BR>established higher altitude.<BR>ANGLE OF ATTACK¡ªThe acute<BR>angle between the chord line of the<BR>airfoil and the direction of the relative<BR>wind.<BR>ANGLE OF INCIDENCE¡ª<BR>The angle formed by the chord line of<BR>the wing and a line parallel to the<BR>longitudinal axis of the airplane.<BR>ANNUAL INSPECTION¡ª<BR>A complete inspection of an aircraft<BR>and engine, required by the Code<BR>of Federal Regulations, to be<BR>accomplished every 12 calendar<BR>months on all certificated aircraft.<BR>Only an A&amp;P technician holding an<BR>Inspection Authorization can conduct<BR>an annual inspection.<BR>ANTI-ICING¡ªThe prevention of<BR>the formation of ice on a surface. Ice<BR>may be prevented by using heat or by<BR>covering the surface with a chemical<BR>that prevents water from reaching the<BR>surface. Anti-icing should not be confused<BR>with deicing, which is the<BR>removal of ice after it has formed on<BR>the surface.<BR>ATTITUDE INDICATOR¡ª<BR>An instrument which uses an artificial<BR>horizon and miniature airplane to<BR>depict the position of the airplane in<BR>relation to the true horizon. The<BR>attitude indicator senses roll as well as<BR>Glossary.qxd 5/7/04 10:46 AM Page G-2<BR>G-3<BR>used to bring the center of gravity into<BR>the allowable range.<BR>BALLOON¡ªThe result of a too<BR>aggressive flare during landing<BR>causing the aircraft to climb.<BR>BASIC EMPTY WEIGHT<BR>(GAMA)¡ªBasic empty weight<BR>includes the standard empty weight<BR>plus optional and special equipment<BR>that has been installed.<BR>BEST ANGLE OF CLIMB (VX)¡ª<BR>The speed at which the aircraft will<BR>produce the most gain in altitude in a<BR>given distance.<BR>BEST GLIDE¡ªThe airspeed in<BR>which the aircraft glides the furthest<BR>for the least altitude lost when in<BR>non-powered flight.<BR>BEST RATE OF CLIMB (VY)¡ª<BR>The speed at which the aircraft will<BR>produce the most gain in altitude in<BR>the least amount of time.<BR>BLADE FACE¡ªThe flat portion of a<BR>propeller blade, resembling the<BR>bottom portion of an airfoil.<BR>BLEED AIR¡ªCompressed air<BR>tapped from the compressor stages of<BR>a turbine engine by use of ducts and<BR>tubing. Bleed air can be used for<BR>deice, anti-ice, cabin pressurization,<BR>heating, and cooling systems.<BR>BLEED VALVE¡ªIn a turbine<BR>engine, a flapper valve, a popoff<BR>valve, or a bleed band designed to<BR>bleed off a portion of the compressor<BR>air to the atmosphere. Used to<BR>maintain blade angle of attack and<BR>provide stall-free engine acceleration<BR>and deceleration.<BR>BOOST PUMP¡ªAn electrically<BR>driven fuel pump, usually of the<BR>centrifugal type, located in one of the<BR>fuel tanks. It is used to provide fuel to<BR>the engine for starting and providing<BR>fuel pressure in the event of failure of<BR>the engine driven pump. It also<BR>pressurizes the fuel lines to prevent<BR>vapor lock.<BR>CAMBERED¡ªThe camber of an<BR>airfoil is the characteristic curve of its<BR>upper and lower surfaces. The upper<BR>camber is more pronounced, while the<BR>lower camber is comparatively flat.<BR>This causes the velocity of the airflow<BR>immediately above the wing to be<BR>much higher than that below the wing.<BR>CARBURETOR ICE¡ª Ice that<BR>forms inside the carburetor due to the<BR>temperature drop caused by the<BR>vaporization of the fuel. Induction<BR>system icing is an operational hazard<BR>because it can cut off the flow of the<BR>fuel/air charge or vary the fuel/air<BR>ratio.<BR>CARBURETOR¡ª1. Pressure: A<BR>hydromechanical device employing a<BR>closed feed system from the fuel<BR>pump to the discharge nozzle. It<BR>meters fuel through fixed jets<BR>according to the mass airflow through<BR>the throttle body and discharges it<BR>under a positive pressure. Pressure<BR>carburetors are distinctly different<BR>from float-type carburetors, as they do<BR>not incorporate a vented float<BR>chamber or suction pickup from a<BR>discharge nozzle located in the venturi<BR>tube. 2. Float-type: Consists<BR>essentially of a main air passage<BR>through which the engine draws its<BR>supply of air, a mechanism to control<BR>the quantity of fuel discharged in<BR>relation to the flow of air, and a means<BR>of regulating the quantity of fuel/air<BR>mixture delivered to the engine<BR>cylinders.<BR>CASCADE REVERSER¡ªA thrust<BR>reverser normally found on turbofan<BR>engines in which a blocker door and a<BR>series of cascade vanes are used to<BR>redirect exhaust gases in a forward<BR>direction.<BR>CENTER OF GRAVITY (CG)¡ª<BR>The point at which an airplane would<BR>balance if it were possible to suspend<BR>it at that point. It is the mass center of<BR>the airplane, or the theoretical point at<BR>which the entire weight of the airplane<BR>is assumed to be concentrated. It may<BR>be expressed in inches from the reference<BR>datum, or in percent of mean<BR>aerodynamic chord (MAC). The location<BR>depends on the distribution of<BR>weight in the airplane.<BR>BUFFETING¡ªThe beating of an<BR>aerodynamic structure or surface by<BR>unsteady flow, gusts, etc.; the irregular<BR>shaking or oscillation of a vehicle<BR>component owing to turbulent air or<BR>separated flow.<BR>BUS BAR¡ªAn electrical power<BR>distribution point to which several<BR>circuits may be connected. It is often a<BR>solid metal strip having a number of<BR>terminals installed on it.<BR>BUS TIE¡ªA switch that connects<BR>two or more bus bars. It is usually<BR>used when one generator fails and<BR>power is lost to its bus. By closing the<BR>switch, the operating generator<BR>powers both busses.<BR>BYPASS AIR¡ªThe part of a<BR>turbofan¡¯s induction air that bypasses<BR>the engine core.<BR>BYPASS RATIO¡ªThe ratio of the<BR>mass airflow in pounds per second<BR>through the fan section of a turbofan<BR>engine to the mass airflow that passes<BR>through the gas generator portion of<BR>the engine. Or, the ratio between fan<BR>mass airflow (lb/sec.) and core engine<BR>mass airflow (lb/sec.).<BR>CABIN PRESSURIZATION¡ªA<BR>condition where pressurized air is<BR>forced into the cabin simulating<BR>pressure conditions at a much lower<BR>altitude and increasing the aircraft<BR>occupants comfort.<BR>CALIBRATED AIRSPEED<BR>(CAS)¡ªIndicated airspeed corrected<BR>for installation error and instrument<BR>error. Although manufacturers attempt<BR>to keep airspeed errors to a minimum,<BR>it is not possible to eliminate all errors<BR>throughout the airspeed operating<BR>range. At certain airspeeds and with<BR>certain flap settings, the installation<BR>and instrument errors may total<BR>several knots. This error is generally<BR>greatest at low airspeeds. In the<BR>cruising and higher airspeed ranges,<BR>indicated airspeed and calibrated<BR>airspeed are approximately the same.<BR>Refer to the airspeed calibration chart<BR>to correct for possible airspeed errors.<BR>Glossary.qxd 5/7/04 10:46 AM Page G-3<BR>G-4<BR>CENTER-OF-GRAVITY<BR>LIMITS¡ªThe specified forward and<BR>aft points within which the CG must<BR>be located during flight. These limits<BR>are indicated on pertinent airplane<BR>specifications.<BR>CENTER-OF-GRAVITY<BR>RANGE¡ªThe distance between the<BR>forward and aft CG limits indicated on<BR>pertinent airplane specifications.<BR>CENTRIFUGAL<BR>FLOW COMPRESSOR¡ª<BR>An impeller-shaped device that receives<BR>air at its center and slings air outward at<BR>high velocity into a diffuser for increased<BR>pressure. Also referred to as a radial outflow<BR>compressor.<BR>CHORD LINE¡ªAn imaginary<BR>straight line drawn through an airfoil<BR>from the leading edge to the trailing<BR>edge.<BR>CIRCUIT BREAKER¡ª<BR>A circuit-protecting device that opens<BR>the circuit in case of excess current<BR>flow. A circuit breakers differs from a<BR>fuse in that it can be reset without<BR>having to be replaced.<BR>CLEAR AIR TURBULENCE¡ª<BR>Turbulence not associated with any<BR>visible moisture.<BR>CLIMB GRADIENT¡ªThe ratio<BR>between distance traveled and altitude<BR>gained.<BR>COCKPIT RESOURCE<BR>MANAGEMENT¡ªTechniques<BR>designed to reduce pilot errors and<BR>manage errors that do occur utilizing<BR>cockpit human resources. The<BR>assumption is that errors are going to<BR>happen in a complex system with<BR>error-prone humans.<BR>COEFFICIENT OF LIFT¡ªSee<BR>LIFT COEFFICIENT.<BR>COFFIN CORNER¡ªThe flight<BR>regime where any increase in airspeed<BR>will induce high speed mach buffet<BR>and any decrease in airspeed will<BR>induce low speed mach buffet.<BR>CONDITION LEVER¡ªIn a turbine<BR>engine, a powerplant control that controls<BR>the flow of fuel to the engine.<BR>The condition lever sets the desired<BR>engine r.p.m. within a narrow range<BR>between that appropriate for ground<BR>and flight operations.<BR>CONFIGURATION¡ªThis is a<BR>general term, which normally refers to<BR>the position of the landing gear<BR>and flaps.<BR>CONSTANT SPEED<BR>PROPELLER¡ª A controllablepitch<BR>propeller whose pitch is<BR>automatically varied in flight by a<BR>governor to maintain a constant r.p.m.<BR>in spite of varying air loads.<BR>CONTROL TOUCH¡ªThe ability to<BR>sense the action of the airplane and its<BR>probable actions in the immediate<BR>future, with regard to attitude and<BR>speed variations, by sensing and<BR>evaluation of varying pressures and<BR>resistance of the control surfaces<BR>transmitted through the cockpit flight<BR>controls.<BR>CONTROLLABILITY¡ªA measure<BR>of the response of an aircraft relative<BR>to the pilot¡¯s flight control inputs.<BR>CONTROLLABLE PITCH<BR>PROPELLER¡ªApropeller in which<BR>the blade angle can be changed during<BR>flight by a control in the cockpit.<BR>CONVENTIONAL LANDING<BR>GEAR¡ªLanding gear employing a<BR>third rear-mounted wheel. These<BR>airplanes are also sometimes referred<BR>to as tailwheel airplanes.<BR>COORDINATED FLIGHT¡ª<BR>Application of all appropriate flight<BR>and power controls to prevent slipping<BR>or skidding in any flight condition.<BR>COORDINATION¡ªThe ability to<BR>use the hands and feet together<BR>subconsciously and in the proper<BR>relationship to produce desired results<BR>in the airplane.<BR>CORE AIRFLOW¡ªAir drawn into<BR>the engine for the gas generator.<BR>COMBUSTION CHAMBER¡ªThe<BR>section of the engine into which fuel<BR>is injected and burned.<BR>COMMON TRAFFIC<BR>ADVISORY FREQUENCY¡ªThe<BR>common frequency used by airport<BR>traffic to announce position reports in<BR>the vicinity of the airport.<BR>COMPLEX AIRCRAFT¡ª<BR>An aircraft with retractable landing<BR>gear, flaps, and a controllable-pitch<BR>propeller, or is turbine powered.<BR>COMPRESSION RATIO¡ª1. In a<BR>reciprocating engine, the ratio of the<BR>volume of an engine cylinder with the<BR>piston at the bottom center to the<BR>volume with the piston at top center.<BR>2. In a turbine engine, the ratio of the<BR>pressure of the air at the discharge to<BR>the pressure of air at the inlet.<BR>COMPRESSOR BLEED AIR¡ª<BR>See BLEED AIR.<BR>COMPRESSOR BLEED<BR>VALVES¡ªSee BLEED VALVE.<BR>COMPRESSOR SECTION¡ª The<BR>section of a turbine engine that<BR>increases the pressure and density of<BR>the air flowing through the engine.<BR>COMPRESSOR STALL¡ªIn gas<BR>turbine engines, a condition in an<BR>axial-flow compressor in which one<BR>or more stages of rotor blades fail to<BR>pass air smoothly to the succeeding<BR>stages. Astall condition is caused by a<BR>pressure ratio that is incompatible<BR>with the engine r.p.m. Compressor<BR>stall will be indicated by a rise in<BR>exhaust temperature or r.p.m.<BR>fluctuation, and if allowed to<BR>continue, may result in flameout and<BR>physical damage to the engine.<BR>COMPRESSOR SURGE¡ªAsevere<BR>compressor stall across the entire<BR>compressor that can result in severe<BR>damage if not quickly corrected. This<BR>condition occurs with a complete<BR>stoppage of airflow or a reversal of<BR>airflow.<BR>Glossary.qxd 5/7/04 10:46 AM Page G-4<BR>G-5<BR>COWL FLAPS¡ªDevices arranged<BR>around certain air-cooled engine<BR>cowlings which may be opened or<BR>closed to regulate the flow of air<BR>around the engine.<BR>CRAB¡ªA flight condition in which<BR>the nose of the airplane is pointed into<BR>the wind a sufficient amount to counteract<BR>a crosswind and maintain a<BR>desired track over the ground.<BR>CRAZING¡ªSmall fractures in<BR>aircraft windshields and windows<BR>caused from being exposed to the<BR>ultraviolet rays of the sun and<BR>temperature extremes.<BR>CRITICAL ALTITUDE¡ª<BR>The maximum altitude under standard<BR>atmospheric conditions at which a<BR>turbocharged engine can produce its<BR>rated horsepower.<BR>CRITICAL ANGLE<BR>OF ATTACK¡ªThe angle of attack at<BR>which a wing stalls regardless of<BR>airspeed, flight attitude, or weight.<BR>CRITICAL ENGINE¡ªThe engine<BR>whose failure has the most adverse<BR>effect on directional control.<BR>CROSS CONTROLLED¡ª<BR>A condition where aileron deflection<BR>is in the opposite direction of rudder<BR>deflection.<BR>CROSSFEED¡ªAsystem that allows<BR>either engine on a twin-engine<BR>airplane to draw fuel from any fuel<BR>tank.<BR>CROSSWIND COMPONENT¡ª<BR>The wind component, measured in<BR>knots, at 90¡ã to the longitudinal axis<BR>of the runway.<BR>CURRENT LIMITER¡ªA device<BR>that limits the generator output to a<BR>level within that rated by the<BR>generator manufacturer.<BR>DATUM (REFERENCE<BR>DATUM)¡ªAn imaginary vertical<BR>plane or line from which all<BR>measurements of moment arm are<BR>taken. The datum is established by the<BR>manufacturer. Once the datum has<BR>been selected, all moment arms and<BR>parasite drag to compensate for the<BR>additional induced drag caused by the<BR>down aileron. This balancing of the<BR>drag forces helps minimize adverse<BR>yaw.<BR>DIFFUSION¡ªReducing the velocity<BR>of air causing the pressure to increase.<BR>DIRECTIONAL STABILITY¡ª<BR>Stability about the vertical axis of an<BR>aircraft, whereby an aircraft tends to<BR>return, on its own, to flight aligned<BR>with the relative wind when disturbed<BR>from that equilibrium state. The<BR>vertical tail is the primary contributor<BR>to directional stability, causing an<BR>airplane in flight to align with the<BR>relative wind.<BR>DITCHING¡ªEmergency landing in<BR>water.<BR>DOWNWASH¡ª<BR>Air deflected perpendicular to the<BR>motion of the airfoil.<BR>DRAG¡ªAn aerodynamic force on a<BR>body acting parallel and opposite to<BR>the relative wind. The resistance of<BR>the atmosphere to the relative motion<BR>of an aircraft. Drag opposes thrust and<BR>limits the speed of the airplane.<BR>DRAG CURVE¡ª<BR>A visual representation of the amount<BR>of drag of an aircraft at various<BR>airspeeds.<BR>DRIFT ANGLE¡ªAngle between<BR>heading and track.<BR>DUCTED-FAN ENGINE¡ª<BR>An engine-propeller combination that<BR>has the propeller enclosed in a radial<BR>shroud. Enclosing the propeller<BR>improves the efficiency of the<BR>propeller.<BR>DUTCH ROLL¡ªA combination of<BR>rolling and yawing oscillations that<BR>normally occurs when the dihedral<BR>effects of an aircraft are more<BR>powerful than the directional stability.<BR>Usually dynamically stable but<BR>objectionable in an airplane because<BR>of the oscillatory nature.<BR>the location of CG range are measured<BR>from this point.<BR>DECOMPRESSION SICKNESS¡ª<BR>A condition where the low pressure at<BR>high altitudes allows bubbles of<BR>nitrogen to form in the blood and<BR>joints causing severe pain. Also<BR>known as the bends.<BR>DEICER BOOTS¡ªInflatable rubber<BR>boots attached to the leading edge of<BR>an airfoil. They can be sequentially<BR>inflated and deflated to break away ice<BR>that has formed over their surface.<BR>DEICING¡ªRemoving ice after it<BR>has formed.<BR>DELAMINATION¡ªThe separation<BR>of layers.<BR>DENSITY ALTITUDE¡ª<BR>This altitude is pressure altitude corrected<BR>for variations from standard<BR>temperature. When conditions are<BR>standard, pressure altitude and density<BR>altitude are the same. If the temperature<BR>is above standard, the density altitude<BR>is higher than pressure altitude. If<BR>the temperature is below standard, the<BR>density altitude is lower than pressure<BR>altitude. This is an important altitude<BR>because it is directly related to the<BR>airplane¡¯s performance.<BR>DESIGNATED PILOT<BR>EXAMINER (DPE)¡ªAn individual<BR>designated by the FAA to administer<BR>practical tests to pilot applicants.<BR>DETONATION¡ª<BR>The sudden release of heat energy<BR>from fuel in an aircraft engine caused<BR>by the fuel-air mixture reaching its<BR>critical pressure and temperature.<BR>Detonation occurs as a violent<BR>explosion rather than a smooth<BR>burning process.<BR>DEWPOINT¡ªThe temperature at<BR>which air can hold no more water.<BR>DIFFERENTIAL AILERONS¡ª<BR>Control surface rigged such that the<BR>aileron moving up moves a greater<BR>distance than the aileron moving<BR>down. The up aileron produces extra<BR>Glossary.qxd 5/7/04 10:46 AM Page G-5<BR>G-6<BR>DYNAMIC HYDROPLANING¡ªA<BR>condition that exists when landing on<BR>a surface with standing water deeper<BR>than the tread depth of the tires. When<BR>the brakes are applied, there is a<BR>possibility that the brake will lock up<BR>and the tire will ride on the surface of<BR>the water, much like a water ski.<BR>When the tires are hydroplaning,<BR>directional control and braking action<BR>are virtually impossible. An effective<BR>anti-skid system can minimize the<BR>effects of hydroplaning.<BR>DYNAMIC STABILITY¡ª<BR>The property of an aircraft that causes<BR>it, when disturbed from straight-andlevel<BR>flight, to develop forces or<BR>moments that restore the original<BR>condition of straight and level.<BR>ELECTRICAL BUS¡ª<BR>See BUS BAR.<BR>ELECTROHYDRAULIC¡ª<BR>Hydraulic control which is electrically<BR>actuated.<BR>ELEVATOR¡ª<BR>The horizontal, movable primary<BR>control surface in the tail section, or<BR>empennage, of an airplane. The<BR>elevator is hinged to the trailing edge<BR>of the fixed horizontal stabilizer.<BR>EMERGENCY LOCATOR<BR>TRANSMITTER¡ªA small, selfcontained<BR>radio transmitter that will<BR>automatically, upon the impact of a<BR>crash, transmit an emergency signal<BR>on 121.5, 243.0, or 406.0 MHz.<BR>EMPENNAGE¡ªThe section of the<BR>airplane that consists of the vertical<BR>stabilizer, the horizontal stabilizer,<BR>and the associated control surfaces.<BR>ENGINE PRESSURE RATIO<BR>(EPR)¡ªThe ratio of turbine<BR>discharge pressure divided by<BR>compressor inlet pressure that is used<BR>as an indication of the amount of<BR>thrust being developed by a turbine<BR>engine.<BR>ENVIRONMENTAL SYSTEMS¡ª<BR>In an aircraft, the systems, including<BR>the supplemental oxygen systems, air<BR>conditioning systems, heaters, and<BR>FIXED SHAFT TURBOPROP<BR>ENGINE¡ªA turboprop engine<BR>where the gas producer spool is<BR>directly connected to the output shaft.<BR>FIXED-PITCH PROPELLERS¡ª<BR>Propellers with fixed blade angles.<BR>Fixed-pitch propellers are designed as<BR>climb propellers, cruise propellers, or<BR>standard propellers.<BR>FLAPS¡ªHinged portion of the<BR>trailing edge between the ailerons and<BR>fuselage. In some aircraft, ailerons<BR>and flaps are interconnected to<BR>produce full-span ¡°flaperons.¡± In<BR>either case, flaps change the lift and<BR>drag on the wing.<BR>FLAT PITCH¡ª<BR>A propeller configuration when the<BR>blade chord is aligned with the direction<BR>of rotation.<BR>FLICKER VERTIGO¡ª<BR>A disorientating condition caused<BR>from flickering light off the blades of<BR>the propeller.<BR>FLIGHT DIRECTOR¡ªAn automatic<BR>flight control system in which<BR>the commands needed to fly the airplane<BR>are electronically computed and<BR>displayed on a flight instrument. The<BR>commands are followed by the human<BR>pilot with manual control inputs or, in<BR>the case of an autopilot system, sent to<BR>servos that move the flight controls.<BR>FLIGHT IDLE¡ªEngine speed,<BR>usually in the 70-80 percent range, for<BR>minimum flight thrust.<BR>FLOATING¡ªA condition when<BR>landing where the airplane does not<BR>settle to the runway due to excessive<BR>airspeed.<BR>FORCE (F)¡ªThe energy applied to<BR>an object that attempts to cause the<BR>object to change its direction, speed,<BR>or motion. In aerodynamics, it is<BR>expressed as F, T (thrust), L (lift), W<BR>(weight), or D (drag), usually in<BR>pounds.<BR>FORM DRAG¡ªThe part of parasite<BR>drag on a body resulting from the<BR>pressurization systems, which make it<BR>possible for an occupant to function at<BR>high altitude.<BR>EQUILIBRIUM¡ªA condition that<BR>exists within a body when the sum of<BR>the moments of all of the forces acting<BR>on the body is equal to zero. In<BR>aerodynamics, equilibrium is when all<BR>opposing forces acting on an aircraft<BR>are balanced (steady, unaccelerated<BR>flight conditions).<BR>EQUIVALENT SHAFT<BR>HORSEPOWER (ESHP)¡ª<BR>A measurement of the total horsepower<BR>of a turboprop engine, including<BR>that provided by jet thrust.<BR>EXHAUST GAS TEMPERATURE<BR>(EGT)¡ªThe temperature of the<BR>exhaust gases as they leave the<BR>cylinders of a reciprocating engine or<BR>the turbine section of a turbine engine.<BR>EXHAUST MANIFOLD¡ªThe part<BR>of the engine that collects exhaust<BR>gases leaving the cylinders.<BR>EXHAUST¡ªThe rear opening of a<BR>turbine engine exhaust duct. The<BR>nozzle acts as an orifice, the size of<BR>which determines the density and<BR>velocity of the gases as they emerge<BR>from the engine.<BR>FALSE HORIZON¡ªAn optical<BR>illusion where the pilot confuses a row<BR>of lights along a road or other straight<BR>line as the horizon.<BR>FALSE START¡ª<BR>See HUNG START.<BR>FEATHERING PROPELLER<BR>(FEATHERED)¡ªA controllable<BR>pitch propeller with a pitch range<BR>sufficient to allow the blades to be<BR>turned parallel to the line of flight to<BR>reduce drag and prevent further<BR>damage to an engine that has been<BR>shut down after a malfunction.<BR>FIXATION¡ª<BR>A psychological condition where the<BR>pilot fixes attention on a single source<BR>of information and ignores all<BR>other sources.<BR>Glossary.qxd 5/7/04 10:46 AM Page G-6<BR>G-7<BR>integrated effect of the static pressure<BR>acting normal to its surface resolved<BR>in the drag direction.<BR>FORWARD SLIP¡ªA slip in which<BR>the airplane¡¯s direction of motion continues<BR>the same as before the slip was<BR>begun. In a forward slip, the airplane¡¯s<BR>longitudinal axis is at an angle to its<BR>flightpath.<BR>FREE POWER TURBINE<BR>ENGINE¡ªA turboprop engine<BR>where the gas producer spool is on a<BR>separate shaft from the output shaft.<BR>The free power turbine spins<BR>independently of the gas producer and<BR>drives the output shaft.<BR>FRICTION DRAG¡ªThe part of<BR>parasitic drag on a body resulting<BR>from viscous shearing stresses over its<BR>wetted surface.<BR>FRISE-TYPE AILERON¡ªAileron<BR>having the nose portion projecting<BR>ahead of the hinge line. When the<BR>trailing edge of the aileron moves up,<BR>the nose projects below the wing¡¯s<BR>lower surface and produces some<BR>parasite drag, decreasing the amount<BR>of adverse yaw.<BR>FUEL CONTROL UNIT¡ª<BR>The fuel-metering device used on a<BR>turbine engine that meters the proper<BR>quantity of fuel to be fed into the<BR>burners of the engine. It integrates the<BR>parameters of inlet air temperature,<BR>compressor speed, compressor<BR>discharge pressure, and exhaust gas<BR>temperature with the position of the<BR>cockpit power control lever.<BR>FUEL EFFICIENCY¡ªDefined as<BR>the amount of fuel used to produce a<BR>specific thrust or horsepower divided<BR>by the total potential power contained<BR>in the same amount of fuel.<BR>FUEL HEATERS¡ªA radiator-like<BR>device which has fuel passing through<BR>the core. A heat exchange occurs to<BR>keep the fuel temperature above the<BR>freezing point of water so that<BR>entrained water does not form ice<BR>crystals, which could block fuel flow.<BR>FUEL INJECTION¡ª<BR>A fuel metering system used on some<BR>aircraft reciprocating engines in<BR>GO-AROUND¡ª<BR>Terminating a landing approach.<BR>GOVERNING RANGE¡ªThe range<BR>of pitch a propeller governor can<BR>control during flight.<BR>GOVERNOR¡ªA control which<BR>limits the maximum rotational speed<BR>of a device.<BR>GROSS WEIGHT¡ª<BR>The total weight of a fully loaded<BR>aircraft including the fuel, oil, crew,<BR>passengers, and cargo.<BR>GROUND ADJUSTABLE TRIM<BR>TAB¡ªA metal trim tab on a control<BR>surface that is not adjustable in flight.<BR>Bent in one direction or another while<BR>on the ground to apply trim forces to<BR>the control surface.<BR>GROUND EFFECT¡ªA condition<BR>of improved performance encountered<BR>when an airplane is operating<BR>very close to the ground. When an<BR>airplane¡¯s wing is under the influence<BR>of ground effect, there is a reduction<BR>in upwash, downwash, and wingtip<BR>vortices. As a result of the reduced<BR>wingtip vortices, induced drag is<BR>reduced.<BR>GROUND IDLE¡ªGas turbine<BR>engine speed usually 60-70 percent of<BR>the maximum r.p.m. range, used as a<BR>minimum thrust setting for ground<BR>operations.<BR>GROUND LOOP¡ªA sharp, uncontrolled<BR>change of direction of an<BR>airplane on the ground.<BR>GROUND POWER UNIT (GPU)¡ª<BR>A type of small gas turbine whose<BR>purpose is to provide electrical power,<BR>and/or air pressure for starting aircraft<BR>engines. Aground unit is connected to<BR>the aircraft when needed. Similar to<BR>an aircraft-installed auxiliary power<BR>unit.<BR>GROUNDSPEED (GS)¡ªThe actual<BR>speed of the airplane over the ground.<BR>It is true airspeed adjusted for<BR>wind. Groundspeed decreases with a<BR>headwind, and increases with<BR>a tailwind.<BR>which a constant flow of fuel is fed to<BR>injection nozzles in the heads of all<BR>cylinders just outside of the intake<BR>valve. It differs from sequential fuel<BR>injection in which a timed charge of<BR>high-pressure fuel is sprayed directly<BR>into the combustion chamber of the<BR>cylinder.<BR>FUEL LOAD¡ªThe expendable part<BR>of the load of the airplane. It includes<BR>only usable fuel, not fuel required to<BR>fill the lines or that which remains<BR>trapped in the tank sumps.<BR>FUEL TANK SUMP¡ªA sampling<BR>port in the lowest part of the fuel tank<BR>that the pilot can utilize to check for<BR>contaminants in the fuel.<BR>FUSELAGE¡ªThe section of the<BR>airplane that consists of the cabin<BR>and/or cockpit, containing seats for<BR>the occupants and the controls for the<BR>airplane.<BR>GAS GENERATOR¡ªThe basic<BR>power producing portion of a gas<BR>turbine engine and excluding such<BR>sections as the inlet duct, the<BR>fan section, free power turbines,<BR>and tailpipe. Each manufacturer<BR>designates what is included as the gas<BR>generator, but generally consists of<BR>the compressor, diffuser, combustor,<BR>and turbine.<BR>GAS TURBINE ENGINE¡ªA form<BR>of heat engine in which burning fuel<BR>adds energy to compressed air and<BR>accelerates the air through the<BR>remainder of the engine. Some of the<BR>energy is extracted to turn the air<BR>compressor, and the remainder<BR>accelerates the air to produce thrust.<BR>Some of this energy can be converted<BR>into torque to drive a propeller or a<BR>system of rotors for a helicopter.<BR>GLIDE RATIO¡ªThe ratio between<BR>distance traveled and altitude lost<BR>during non-powered flight.<BR>GLIDEPATH¡ªThe path of an<BR>aircraft relative to the ground while<BR>approaching a landing.<BR>GLOBAL POSITION SYSTEM<BR>(GPS)¡ªA satellite-based radio positioning,<BR>navigation, and time-transfer<BR>system.<BR>Glossary.qxd 5/7/04 10:46 AM Page G-7<BR>G-8<BR>GROUND TRACK¡ªThe aircraft¡¯s<BR>path over the ground when in flight.<BR>GUST PENETRATION SPEED¡ª<BR>The speed that gives the greatest<BR>margin between the high and low<BR>mach speed buffets.<BR>GYROSCOPIC PRECESSION¡ª<BR>An inherent quality of rotating bodies,<BR>which causes an applied force to be<BR>manifested 90&ordm; in the direction of<BR>rotation from the point where the<BR>force is applied.<BR>HAND PROPPING¡ªStarting an<BR>engine by rotating the propeller by<BR>hand.<BR>HEADING¡ªThe direction in which<BR>the nose of the aircraft is pointing<BR>during flight.<BR>HEADING BUG¡ªA marker on the<BR>heading indicator that can be rotated<BR>to a specific heading for reference<BR>purposes, or to command an autopilot<BR>to fly that heading.<BR>HEADING INDICATOR¡ª<BR>An instrument which senses airplane<BR>movement and displays heading based<BR>on a 360&ordm; azimuth, with the final zero<BR>omitted. The heading indicator, also<BR>called a directional gyro, is fundamentally<BR>a mechanical instrument<BR>designed to facilitate the use of the<BR>magnetic compass. The heading indicator<BR>is not affected by the forces that<BR>make the magnetic compass difficult<BR>to interpret.<BR>HEADWIND COMPONENT¡ªThe<BR>component of atmospheric winds that<BR>acts opposite to the aircraft¡¯s flightpath.<BR>HIGH PERFORMANCE<BR>AIRCRAFT¡ªAn aircraft with an<BR>engine of more than 200 horsepower.<BR>HORIZON¡ªThe line of sight<BR>boundary between the earth and the<BR>sky.<BR>HORSEPOWER¡ª<BR>The term, originated by inventor<BR>James Watt, means the amount of<BR>work a horse could do in one second.<BR>engine. Some igniters resemble spark<BR>plugs, while others, called glow plugs,<BR>have a coil of resistance wire that<BR>glows red hot when electrical current<BR>flows through the coil.<BR>IMPACT ICE¡ªIce that forms on the<BR>wings and control surfaces or on the<BR>carburetor heat valve, the walls of the<BR>air scoop, or the carburetor units<BR>during flight. Impact ice collecting on<BR>the metering elements of the<BR>carburetor may upset fuel metering or<BR>stop carburetor fuel flow.<BR>INCLINOMETER¡ªAn instrument<BR>consisting of a curved glass tube,<BR>housing a glass ball, and damped with<BR>a fluid similar to kerosene. It may be<BR>used to indicate inclination, as a level,<BR>or, as used in the turn indicators, to<BR>show the relationship between gravity<BR>and centrifugal force in a turn.<BR>INDICATED AIRSPEED (IAS)¡ª<BR>The direct instrument reading<BR>obtained from the airspeed indicator,<BR>uncorrected for variations in atmospheric<BR>density, installation error, or<BR>instrument error. Manufacturers use<BR>this airspeed as the basis for determining<BR>airplane performance. Takeoff,<BR>landing, and stall speeds listed in the<BR>AFM or POH are indicated airspeeds<BR>and do not normally vary with altitude<BR>or temperature.<BR>INDICATED ALTITUDE¡ª<BR>The altitude read directly from the<BR>altimeter (uncorrected) when it is set<BR>to the current altimeter setting.<BR>INDUCED DRAG¡ªThat part of<BR>total drag which is created by the<BR>production of lift. Induced drag<BR>increases with a decrease in airspeed.<BR>INDUCTION MANIFOLD¡ªThe<BR>part of the engine that distributes<BR>intake air to the cylinders.<BR>INERTIA¡ªThe opposition which a<BR>body offers to a change of motion.<BR>INITIAL CLIMB¡ªThis stage of the<BR>climb begins when the airplane leaves<BR>the ground, and a pitch attitude has<BR>One horsepower equals 550<BR>foot-pounds per second, or 33,000<BR>foot-pounds per minute.<BR>HOT START¡ªIn gas turbine<BR>engines, a start which occurs with<BR>normal engine rotation, but exhaust<BR>temperature exceeds prescribed<BR>limits. This is usually caused by an<BR>excessively rich mixture in the<BR>combustor. The fuel to the engine<BR>must be terminated immediately to<BR>prevent engine damage.<BR>HUNG START¡ªIn gas turbine<BR>engines, a condition of normal light<BR>off but with r.p.m. remaining at some<BR>low value rather than increasing to the<BR>normal idle r.p.m. This is often the<BR>result of insufficient power to the<BR>engine from the starter. In the event of<BR>a hung start, the engine should be shut<BR>down.<BR>HYDRAULICS¡ªThe branch of<BR>science that deals with the<BR>transmission of power by incompressible<BR>fluids under pressure.<BR>HYDROPLANING¡ªA condition<BR>that exists when landing on a surface<BR>with standing water deeper than the<BR>tread depth of the tires. When the<BR>brakes are applied, there is a<BR>possibility that the brake will lock up<BR>and the tire will ride on the surface of<BR>the water, much like a water ski.<BR>When the tires are hydroplaning,<BR>directional control and braking action<BR>are virtually impossible. An effective<BR>anti-skid system can minimize the<BR>effects of hydroplaning.<BR>HYPOXIA¡ªA lack of sufficient<BR>oxygen reaching the body tissues.<BR>IFR (INSTRUMENT FLIGHT<BR>RULES)¡ªRules that govern the<BR>procedure for conducting flight in<BR>weather conditions below VFR<BR>weather minimums. The term ¡°IFR¡±<BR>also is used to define weather<BR>conditions and the type of flight plan<BR>under which an aircraft is operating.<BR>IGNITER PLUGS¡ªThe electrical<BR>device used to provide the spark for<BR>starting combustion in a turbine<BR>Glossary.qxd 5/7/04 10:46 AM Page G-8<BR>G-9<BR>been established to climb away from<BR>the takeoff area.<BR>INTEGRAL FUEL TANK¡ª<BR>A portion of the aircraft structure,<BR>usually a wing, which is sealed off and<BR>used as a fuel tank. When a wing is<BR>used as an integral fuel tank, it is<BR>called a ¡°wet wing.¡±<BR>INTERCOOLER¡ªA device used to<BR>reduce the temperature of the<BR>compressed air before it enters the<BR>fuel metering device. The resulting<BR>cooler air has a higher density, which<BR>permits the engine to be operated with<BR>a higher power setting.<BR>INTERNAL COMBUSTION<BR>ENGINES¡ªAn engine that produces<BR>power as a result of expanding hot<BR>gases from the combustion of fuel and<BR>air within the engine itself. A steam<BR>engine where coal is burned to heat up<BR>water inside the engine is an example<BR>of an external combustion engine.<BR>INTERSTAGE TURBINE<BR>TEMPERATURE (ITT)¡ªThe temperature<BR>of the gases between the high<BR>pressure and low pressure turbines.<BR>INVERTER¡ªAn electrical device<BR>that changes DC to AC power.<BR>ISA (INTERNATIONAL<BR>STANDARD ATMOSPHERE)¡ª<BR>Standard atmospheric conditions<BR>consisting of a temperature of 59¡ãF<BR>(15¡ãC), and a barometric pressure of<BR>29.92 in. Hg. (1013.2 mb) at sea level.<BR>ISA values can be calculated for<BR>various altitudes using a standard<BR>lapse rate of approximately 2¡ãC per<BR>1,000 feet.<BR>JET POWERED AIRPLANE¡ªAn<BR>aircraft powered by a turbojet or<BR>turbofan engine.<BR>KINESTHESIA¡ªThe sensing of<BR>movements by feel.<BR>LATERAL AXIS¡ªAn imaginary<BR>line passing through the center of<BR>gravity of an airplane and extending<BR>across the airplane from wingtip<BR>to wingtip.<BR>the coefficient of drag for any given<BR>angle of attack.<BR>LIFT-OFF¡ªThe act of becoming<BR>airborne as a result of the wings<BR>lifting the airplane off the ground, or<BR>the pilot rotating the nose up,<BR>increasing the angle of attack to start a<BR>climb.<BR>LIMIT LOAD FACTOR¡ªAmount<BR>of stress, or load factor, that an aircraft<BR>can withstand before structural<BR>damage or failure occurs.<BR>LOAD FACTOR¡ªThe ratio of the<BR>load supported by the airplane¡¯s wings<BR>to the actual weight of the aircraft and<BR>its contents. Also referred to as<BR>G-loading.<BR>LONGITUDINAL AXIS¡ª<BR>An imaginary line through an aircraft<BR>from nose to tail, passing through its<BR>center of gravity. The longitudinal<BR>axis is also called the roll axis of the<BR>aircraft. Movement of the ailerons<BR>rotates an airplane about its<BR>longitudinal axis.<BR>LONGITUDINAL STABILITY<BR>(PITCHING)¡ªStability about the<BR>lateral axis. A desirable characteristic<BR>of an airplane whereby it tends to<BR>return to its trimmed angle of attack<BR>after displacement.<BR>MACH¡ªSpeed relative to the speed<BR>of sound. Mach 1 is the speed of<BR>sound.<BR>MACH BUFFET¡ª<BR>Airflow separation behind a<BR>shock-wave pressure barrier caused<BR>by airflow over flight surfaces<BR>exceeding the speed of sound.<BR>MACH COMPENSATING<BR>DEVICE¡ªA device to alert the pilot<BR>of inadvertent excursions beyond its<BR>certified maximum operating speed.<BR>MACH CRITICAL¡ªThe MACH<BR>speed at which some portion of the<BR>airflow over the wing first equals<BR>MACH 1.0. This is also the speed at<BR>which a shock wave first appears on<BR>the airplane.<BR>LATERAL STABILITY<BR>(ROLLING)¡ªThe stability about the<BR>longitudinal axis of an aircraft.<BR>Rolling stability or the ability of an<BR>airplane to return to level flight due to<BR>a disturbance that causes one of the<BR>wings to drop.<BR>LEAD-ACID BATTERY¡ª<BR>A commonly used secondary cell<BR>having lead as its negative plate and<BR>lead peroxide as its positive plate.<BR>Sulfuric acid and water serve as the<BR>electrolyte.<BR>LEADING EDGE DEVICES¡ª<BR>High lift devices which are found on<BR>the leading edge of the airfoil. The<BR>most common types are fixed slots,<BR>movable slats, and leading edge flaps.<BR>LEADING EDGE¡ªThe part of an<BR>airfoil that meets the airflow first.<BR>LEADING EDGE FLAP¡ª<BR>A portion of the leading edge of an<BR>airplane wing that folds downward to<BR>increase the camber, lift, and drag of<BR>the wing. The leading-edge flaps are<BR>extended for takeoffs and landings to<BR>increase the amount of aerodynamic<BR>lift that is produced at any given<BR>airspeed.<BR>LICENSED EMPTY WEIGHT¡ª<BR>The empty weight that consists of the<BR>airframe, engine(s), unusable fuel,<BR>and undrainable oil plus standard and<BR>optional equipment as specified in the<BR>equipment list. Some manufacturers<BR>used this term prior to GAMA<BR>standardization.<BR>LIFT¡ªOne of the four main forces<BR>acting on an aircraft. On a fixed-wing<BR>aircraft, an upward force created by<BR>the effect of airflow as it passes over<BR>and under the wing.<BR>LIFT COEFFICIENT¡ª A coefficient<BR>representing the lift of a given<BR>airfoil. Lift coefficient is obtained by<BR>dividing the lift by the free-stream<BR>dynamic pressure and the representative<BR>area under consideration.<BR>LIFT/DRAG RATIO¡ª<BR>The efficiency of an airfoil section. It<BR>is the ratio of the coefficient of lift to<BR>Glossary.qxd 5/7/04 10:46 AM Page G-9<BR>G-10<BR>MACH TUCK¡ªAcondition that can<BR>occur when operating a swept-wing<BR>airplane in the transonic speed range.<BR>A shock wave could form in the root<BR>portion of the wing and cause the<BR>air behind it to separate. This<BR>shock-induced separation causes the<BR>center of pressure to move aft. This,<BR>combined with the increasing amount<BR>of nose down force at higher speeds to<BR>maintain left flight, causes the nose to<BR>¡°tuck.¡± If not corrected, the airplane<BR>could enter a steep, sometimes<BR>unrecoverable dive.<BR>MAGNETIC COMPASS¡ªA device<BR>for determining direction measured<BR>from magnetic north.<BR>MAIN GEAR¡ªThe wheels of an<BR>aircraft¡¯s landing gear that supports<BR>the major part of the aircraft¡¯s weight.<BR>MANEUVERABILITY¡ªAbility of<BR>an aircraft to change directions along<BR>a flightpath and withstand the stresses<BR>imposed upon it.<BR>MANEUVERING SPEED (VA) ¡ª<BR>The maximum speed where full,<BR>abrupt control movement can be used<BR>without overstressing the airframe.<BR>MANIFOLD PRESSURE (MP)¡ª<BR>The absolute pressure of the fuel/air<BR>mixture within the intake manifold,<BR>usually indicated in inches of<BR>mercury.<BR>MAXIMUM ALLOWABLE<BR>TAKEOFF POWER¡ªThe maximum<BR>power an engine is allowed to<BR>develop for a limited period of time;<BR>usually about one minute.<BR>MAXIMUM LANDING<BR>WEIGHT¡ªThe greatest weight that<BR>an airplane normally is allowed to<BR>have at landing.<BR>MAXIMUM RAMP WEIGHT¡ª<BR>The total weight of a loaded aircraft,<BR>including all fuel. It is greater than the<BR>takeoff weight due to the fuel that will<BR>be burned during the taxi and runup<BR>operations. Ramp weight may also be<BR>referred to as taxi weight.<BR>allows air to continue flowing over the<BR>top of the wing and delays airflow<BR>separation.<BR>MUSHING¡ªA flight condition<BR>caused by slow speed where the<BR>control surfaces are marginally<BR>effective.<BR>N1, N2, N3¡ªSpool speed expressed in<BR>percent rpm. N1 on a turboprop is the<BR>gas producer speed. N1 on a turbofan<BR>or turbojet engine is the fan speed or<BR>low pressure spool speed. N2 is the<BR>high pressure spool speed on engine<BR>with 2 spools and medium pressure<BR>spool on engines with 3 spools with<BR>N3 being the high pressure spool.<BR>NACELLE¡ª<BR>Astreamlined enclosure on an aircraft<BR>in which an engine is mounted.<BR>On multiengine propeller-driven<BR>airplanes, the nacelle is normally<BR>mounted on the leading edge of the<BR>wing.<BR>NEGATIVE STATIC<BR>STABILITY¡ªThe initial tendency<BR>of an aircraft to continue away from<BR>the original state of equilibrium after<BR>being disturbed.<BR>NEGATIVE TORQUE SENSING<BR>(NTS)¡ª A system in a turboprop<BR>engine that prevents the engine from<BR>being driven by the propeller. The<BR>NTS increases the blade angle when<BR>the propellers try to drive the engine.<BR>NEUTRAL STATIC<BR>STABILITY¡ªThe initial tendency<BR>of an aircraft to remain in a new<BR>condition after its equilibrium has<BR>been disturbed.<BR>NICKEL-CADMIUM BATTERY<BR>(NICAD)¡ª A battery made up of<BR>alkaline secondary cells. The positive<BR>plates are nickel hydroxide, the<BR>negative plates are cadmium<BR>hydroxide, and potassium hydroxide<BR>is used as the electrolyte.<BR>NORMAL CATEGORY¡ª<BR>An airplane that has a seating<BR>configuration, excluding pilot seats,<BR>MAXIMUM TAKEOFF<BR>WEIGHT¡ªThe maximum allowable<BR>weight for takeoff.<BR>MAXIMUM WEIGHT¡ª<BR>The maximum authorized weight of<BR>the aircraft and all of its equipment as<BR>specified in the Type Certificate Data<BR>Sheets (TCDS) for the aircraft.<BR>MAXIMUM ZERO FUEL<BR>WEIGHT (GAMA)¡ªThe maximum<BR>weight, exclusive of usable fuel.<BR>MINIMUM CONTROLLABLE<BR>AIRSPEED¡ªAn airspeed at which<BR>any further increase in angle of attack,<BR>increase in load factor, or reduction in<BR>power, would result in an immediate<BR>stall.<BR>MINIMUM DRAG SPEED<BR>(L/DMAX)¡ªThe point on the total<BR>drag curve where the lift-to-drag ratio<BR>is the greatest. At this speed, total drag<BR>is minimized.<BR>MIXTURE¡ªThe ratio of fuel to air<BR>entering the engine¡¯s cylinders.<BR>MMO¡ªMaximum operating speed<BR>expressed in terms of a decimal of<BR>mach speed.<BR>MOMENT ARM¡ªThe distance<BR>from a datum to the applied force.<BR>MOMENT INDEX (OR INDEX)¡ª<BR>A moment divided by a constant such<BR>as 100, 1,000, or 10,000. The purpose<BR>of using a moment index is to simplify<BR>weight and balance computations of<BR>airplanes where heavy items and long<BR>arms result in large, unmanageable<BR>numbers.<BR>MOMENT¡ªThe product of the<BR>weight of an item multiplied by its<BR>arm. Moments are expressed in<BR>pound-inches (lb-in). Total moment is<BR>the weight of the airplane multiplied<BR>by the distance between the datum and<BR>the CG.<BR>MOVABLE SLAT¡ªA movable<BR>auxiliary airfoil on the leading edge of<BR>a wing. It is closed in normal flight but<BR>extends at high angles of attack. This<BR>Glossary.qxd 5/7/04 10:46 AM Page G-10<BR>G-11<BR>of nine or less, a maximum<BR>certificated takeoff weight of 12,500<BR>pounds or less, and intended for<BR>nonacrobatic operation.<BR>NORMALIZING<BR>(TURBONORMALIZING)¡ª<BR>A turbocharger that maintains sea<BR>level pressure in the induction manifold<BR>at altitude.<BR>OCTANE¡ªThe rating system of<BR>aviation gasoline with regard to its<BR>antidetonating qualities.<BR>OVERBOOST¡ªA condition in<BR>which a reciprocating engine has<BR>exceeded the maximum manifold<BR>pressure allowed by the manufacturer.<BR>Can cause damage to engine<BR>components.<BR>OVERSPEED¡ªA condition in<BR>which an engine has produced more<BR>r.p.m. than the manufacturer<BR>recommends, or a condition in which<BR>the actual engine speed is higher than<BR>the desired engine speed as set on the<BR>propeller control.<BR>OVERTEMP¡ªA condition in which<BR>a device has reached a temperature<BR>above that approved by the<BR>manufacturer or any exhaust<BR>temperature that exceeds the<BR>maximum allowable for a given operating<BR>condition or time limit. Can<BR>cause internal damage to an engine.<BR>OVERTORQUE¡ªA condition in<BR>which an engine has produced more<BR>torque (power) than the manufacturer<BR>recommends, or a condition in a<BR>turboprop or turboshaft engine where<BR>the engine power has exceeded the<BR>maximum allowable for a given<BR>operating condition or time limit. Can<BR>cause internal damage to an engine.<BR>PARASITE DRAG¡ªThat part of<BR>total drag created by the design or<BR>shape of airplane parts. Parasite drag<BR>increases with an increase in airspeed.<BR>PAYLOAD (GAMA)¡ªThe weight<BR>of occupants, cargo, and baggage.<BR>P-FACTOR¡ªA tendency for an<BR>aircraft to yaw to the left due to the<BR>for scheduling fuel flow to the<BR>combustion chambers of a turbine<BR>engine.<BR>POWER¡ªImplies work rate or units<BR>of work per unit of time, and as such,<BR>it is a function of the speed at which<BR>the force is developed. The term<BR>¡°power required¡± is generally<BR>associated with reciprocating engines.<BR>POWERPLANT¡ª<BR>A complete engine and propeller<BR>combination with accessories.<BR>PRACTICAL SLIP LIMIT¡ªThe<BR>maximum slip an aircraft is capable of<BR>performing due to rudder travel limits.<BR>PRECESSION¡ªThe tilting or<BR>turning of a gyro in response to<BR>deflective forces causing slow drifting<BR>and erroneous indications in<BR>gyroscopic instruments.<BR>PREIGNITION¡ªIgnition occurring<BR>in the cylinder before the time of<BR>normal ignition. Preignition is often<BR>caused by a local hot spot in the<BR>combustion chamber igniting the<BR>fuel/air mixture.<BR>PRESSURE ALTITUDE¡ª<BR>The altitude indicated when the<BR>altimeter setting window (barometric<BR>scale) is adjusted to 29.92. This is the<BR>altitude above the standard datum<BR>plane, which is a theoretical plane<BR>where air pressure (corrected to 15&ordm;C)<BR>equals 29.92 in. Hg. Pressure altitude<BR>is used to compute density altitude,<BR>true altitude, true airspeed, and other<BR>performance data.<BR>PROFILE DRAG¡ªThe total of the<BR>skin friction drag and form drag for a<BR>two-dimensional airfoil section.<BR>PROPELLER BLADE ANGLE¡ª<BR>The angle between the propeller chord<BR>and the propeller plane of rotation.<BR>PROPELLER LEVER¡ª<BR>The control on a free power turbine<BR>turboprop that controls propeller<BR>speed and the selection for propeller<BR>feathering.<BR>PROPELLER SLIPSTREAM¡ª<BR>The volume of air accelerated behind<BR>a propeller producing thrust.<BR>descending propeller blade on the<BR>right producing more thrust than the<BR>ascending blade on the left. This<BR>occurs when the aircraft¡¯s<BR>longitudinal axis is in a climbing<BR>attitude in relation to the relative<BR>wind. The P-factor would be to the<BR>right if the aircraft had a counterclockwise<BR>rotating propeller.<BR>PILOT¡¯S OPERATING<BR>HANDBOOK (POH)¡ªA document<BR>developed by the airplane<BR>manufacturer and contains the FAAapproved<BR>Airplane Flight Manual<BR>(AFM) information.<BR>PISTON ENGINE¡ªA reciprocating<BR>engine.<BR>PITCH¡ªThe rotation of an airplane<BR>about its lateral axis, or on a propeller,<BR>the blade angle as measured from<BR>plane of rotation.<BR>PIVOTAL ALTITUDE¡ªA specific<BR>altitude at which, when an airplane<BR>turns at a given groundspeed, a projecting<BR>of the sighting reference line<BR>to a selected point on the ground will<BR>appear to pivot on that point.<BR>PNEUMATIC SYSTEMS¡ª<BR>The power system in an aircraft used<BR>for operating such items as landing<BR>gear, brakes, and wing flaps with<BR>compressed air as the operating fluid.<BR>PORPOISING¡ª<BR>Oscillating around the lateral axis of<BR>the aircraft during landing.<BR>POSITION LIGHTS¡ªLights on an<BR>aircraft consisting of a red light on the<BR>left wing, a green light on the right<BR>wing, and a white light on the tail.<BR>CFRs require that these lights be<BR>displayed in flight from sunset to<BR>sunrise.<BR>POSITIVE STATIC STABILITY¡ª<BR>The initial tendency to return to a state<BR>of equilibrium when disturbed from<BR>that state.<BR>POWER DISTRIBUTION BUS¡ª<BR>See BUS BAR.<BR>POWER LEVER¡ªThe cockpit<BR>lever connected to the fuel control unit<BR>Glossary.qxd 5/7/04 10:46 AM Page G-11<BR>G-12<BR>PROPELLER<BR>SYNCHRONIZATION¡ª<BR>A condition in which all of<BR>the propellers have their pitch<BR>automatically adjusted to maintain a<BR>constant r.p.m. among all of the<BR>engines of a multiengine aircraft.<BR>PROPELLER¡ªA device for<BR>propelling an aircraft that, when<BR>rotated, produces by its action on<BR>the air, a thrust approximately<BR>perpendicular to its plane of rotation.<BR>It includes the control components<BR>normally supplied by its<BR>manufacturer.<BR>RAMP WEIGHT¡ªThe total weight<BR>of the aircraft while on the ramp. It<BR>differs from takeoff weight by the<BR>weight of the fuel that will be<BR>consumed in taxiing to the point of<BR>takeoff.<BR>RATE OF TURN¡ªThe rate in<BR>degrees/second of a turn.<BR>RECIPROCATING ENGINE¡ªAn<BR>engine that converts the heat energy<BR>from burning fuel into the<BR>reciprocating movement of the pistons.<BR>This movement is converted into<BR>a rotary motion by the connecting rods<BR>and crankshaft.<BR>REDUCTION GEAR¡ªThe gear<BR>arrangement in an aircraft engine that<BR>allows the engine to turn at a faster<BR>speed than the propeller.<BR>REGION OF REVERSE<BR>COMMAND¡ªFlight regime in<BR>which flight at a higher airspeed<BR>requires a lower power setting and a<BR>lower airspeed requires a higher<BR>power setting in order to maintain<BR>altitude.<BR>REGISTRATION<BR>CERTIFICATE¡ªA State and Federal<BR>certificate that documents<BR>aircraft ownership.<BR>RELATIVE WIND¡ªThe direction<BR>of the airflow with respect to the wing.<BR>If a wing moves forward horizontally,<BR>the relative wind moves backward<BR>horizontally. Relative wind is parallel<BR>to and opposite the flightpath of<BR>the airplane.<BR>alignment guidance during takeoff<BR>and landings. The centerline consists<BR>of a line of uniformly spaced stripes<BR>and gaps.<BR>RUNWAY EDGE LIGHTS¡ª<BR>Runway edge lights are used to<BR>outline the edges of runways during<BR>periods of darkness or restricted<BR>visibility conditions. These light<BR>systems are classified according to the<BR>intensity or brightness they are<BR>capable of producing: they are the<BR>High Intensity Runway Lights<BR>(HIRL), Medium Intensity Runway<BR>Lights (MIRL), and the Low Intensity<BR>Runway Lights (LIRL). The HIRL<BR>and MIRL systems have variable<BR>intensity controls, whereas the LIRLs<BR>normally have one intensity setting.<BR>RUNWAY END IDENTIFIER<BR>LIGHTS (REIL)¡ªOne component<BR>of the runway lighting system. These<BR>lights are installed at many airfields<BR>to provide rapid and positive<BR>identification of the approach end of a<BR>particular runway.<BR>RUNWAY INCURSION¡ª<BR>Any occurrence at an airport<BR>involving an aircraft, vehicle, person,<BR>or object on the ground that creates a<BR>collision hazard or results in loss of<BR>separation with an aircraft taking off,<BR>intending to takeoff, landing, or<BR>intending to land.<BR>RUNWAY THRESHOLD<BR>MARKINGS¡ªRunway threshold<BR>markings come in two configurations.<BR>They either consist of eight<BR>longitudinal stripes of uniform<BR>dimensions disposed symmetrically<BR>about the runway centerline, or the<BR>number of stripes is related to the<BR>runway width. A threshold marking<BR>helps identify the beginning of the<BR>runway that is available for landing.<BR>In some instances, the landing<BR>threshold may be displaced.<BR>SAFETY (SQUAT) SWITCH¡ªAn<BR>electrical switch mounted on one of<BR>the landing gear struts. It is used to<BR>sense when the weight of the aircraft<BR>is on the wheels.<BR>SCAN¡ªA procedure used by the<BR>pilot to visually identify all resources<BR>of information in flight.<BR>REVERSE THRUST¡ªA condition<BR>where jet thrust is directed forward<BR>during landing to increase the rate of<BR>deceleration.<BR>REVERSING PROPELLER¡ª<BR>A propeller system with a pitch<BR>change mechanism that includes full<BR>reversing capability. When the pilot<BR>moves the throttle controls to reverse,<BR>the blade angle changes to a pitch<BR>angle and produces a reverse thrust,<BR>which slows the airplane down during<BR>a landing.<BR>ROLL¡ªThe motion of the aircraft<BR>about the longitudinal axis. It is<BR>controlled by the ailerons.<BR>ROUNDOUT (FLARE)¡ª<BR>Apitch-up during landing approach to<BR>reduce rate of descent and forward<BR>speed prior to touchdown.<BR>RUDDER¡ªThe movable primary<BR>control surface mounted on the<BR>trailing edge of the vertical fin of an<BR>airplane. Movement of the rudder<BR>rotates the airplane about its vertical<BR>axis.<BR>RUDDERVATOR¡ªApair of control<BR>surfaces on the tail of an aircraft<BR>arranged in the form of a V. These<BR>surfaces, when moved together by the<BR>control wheel, serve as elevators, and<BR>when moved differentially by the<BR>rudder pedals, serve as a rudder.<BR>RUNWAY CENTERLINE<BR>LIGHTS¡ªRunway centerline lights<BR>are installed on some precision<BR>approach runways to facilitate landing<BR>under adverse visibility conditions.<BR>They are located along the runway<BR>centerline and are spaced at 50-foot<BR>intervals. When viewed from the<BR>landing threshold, the runway<BR>centerline lights are white until the<BR>last 3,000 feet of the runway. The<BR>white lights begin to alternate with red<BR>for the next 2,000 feet, and for the last<BR>1,000 feet of the runway, all centerline<BR>lights are red.<BR>RUNWAY CENTERLINE<BR>MARKINGS¡ª<BR>The runway centerline identifies the<BR>center of the runway and provides<BR>Glossary.qxd 5/7/04 10:46 AM Page G-12<BR>G-13<BR>SEA LEVEL¡ªA reference height<BR>used to determine standard<BR>atmospheric conditions and altitude<BR>measurements.<BR>SEGMENTED CIRCLE¡ªA visual<BR>ground based structure to provide<BR>traffic pattern information.<BR>SERVICE CEILING¡ª<BR>The maximum density altitude where<BR>the best rate-of-climb airspeed will<BR>produce a 100 feet-per-minute climb<BR>at maximum weight while in a clean<BR>configuration with maximum continuous<BR>power.<BR>SERVO TAB¡ªAn auxiliary control<BR>mounted on a primary control surface,<BR>which automatically moves in the<BR>direction opposite the primary control<BR>to provide an aerodynamic assist in<BR>the movement of the control.<BR>SHAFT HORSE POWER (SHP)¡ª<BR>Turboshaft engines are rated in shaft<BR>horsepower and calculated by use of<BR>a dynamometer device. Shaft<BR>horsepower is exhaust thrust<BR>converted to a rotating shaft.<BR>SHOCK WAVES¡ªA compression<BR>wave formed when a body moves<BR>through the air at a speed greater than<BR>the speed of sound.<BR>SIDESLIP¡ªA slip in which the<BR>airplane¡¯s longitudinal axis remains<BR>parallel to the original flightpath, but the<BR>airplane no longer flies straight ahead.<BR>Instead, the horizontal component of<BR>wing lift forces the airplane to move<BR>sideways toward the low wing.<BR>SINGLE ENGINE ABSOLUTE<BR>CEILING¡ªThe altitude that a twinengine<BR>airplane can no longer climb<BR>with one engine inoperative.<BR>SINGLE ENGINE SERVICE<BR>CEILING¡ªThe altitude that a twinengine<BR>airplane can no longer climb at<BR>a rate greater then 50 f.p.m. with one<BR>engine inoperative.<BR>SKID¡ªA condition where the tail of<BR>the airplane follows a path outside the<BR>path of the nose during a turn.<BR>SPLIT SHAFT<BR>TURBINE ENGINE¡ªSee FREE<BR>POWER TURBINE ENGINE.<BR>SPOILERS¡ªHigh-drag devices that<BR>can be raised into the air flowing over<BR>an airfoil, reducing lift and increasing<BR>drag. Spoilers are used for roll control<BR>on some aircraft. Deploying spoilers<BR>on both wings at the same time allows<BR>the aircraft to descend without gaining<BR>speed. Spoilers are also used to<BR>shorten the ground roll after landing.<BR>SPOOL¡ªA shaft in a turbine engine<BR>which drives one or more<BR>compressors with the power derived<BR>from one or more turbines.<BR>STABILATOR¡ªA single-piece horizontal<BR>tail surface on an airplane that<BR>pivots around a central hinge point. A<BR>stabilator serves the purposes of both<BR>the horizontal stabilizer and<BR>the elevator.<BR>STABILITY¡ªThe inherent quality<BR>of an airplane to correct for conditions<BR>that may disturb its equilibrium, and<BR>to return or to continue on the original<BR>flightpath. It is primarily an airplane<BR>design characteristic.<BR>STABILIZED APPROACH¡ªA<BR>landing approach in which the pilot<BR>establishes and maintains a constant<BR>angle glidepath towards a predetermined<BR>point on the landing runway. It<BR>is based on the pilot¡¯s judgment of<BR>certain visual cues, and depends on<BR>the maintenance of a constant final<BR>descent airspeed and configuration.<BR>STALL¡ªA rapid decrease in lift<BR>caused by the separation of airflow<BR>from the wing¡¯s surface brought on by<BR>exceeding the critical angle of attack.<BR>A stall can occur at any pitch attitude<BR>or airspeed.<BR>STALL STRIPS¡ªAspoiler attached<BR>to the inboard leading edge of some<BR>wings to cause the center section of<BR>the wing to stall before the tips. This<BR>assures lateral control throughout the<BR>stall.<BR>SLIP¡ªAn intentional maneuver to<BR>decrease airspeed or increase rate of<BR>descent, and to compensate for a<BR>crosswind on landing. A slip can also<BR>be unintentional when the pilot fails<BR>to maintain the aircraft in coordinated<BR>flight.<BR>SPECIFIC FUEL<BR>CONSUMPTION¡ª<BR>Number of pounds of fuel consumed<BR>in 1 hour to produce 1 HP.<BR>SPEED¡ªThe distance traveled in a<BR>given time.<BR>SPEED BRAKES¡ªA control<BR>system that extends from the airplane<BR>structure into the airstream to<BR>produce drag and slow the airplane.<BR>SPEED INSTABILITY¡ª<BR>A condition in the region of reverse<BR>command where a disturbance that<BR>causes the airspeed to decrease causes<BR>total drag to increase, which in turn,<BR>causes the airspeed to decrease<BR>further.<BR>SPEED SENSE¡ªThe ability to<BR>sense instantly and react to any<BR>reasonable variation of airspeed.<BR>SPIN¡ªAn aggravated stall that<BR>results in what is termed an ¡°autorotation¡±<BR>wherein the airplane follows a<BR>downward corkscrew path. As the airplane<BR>rotates around the vertical axis,<BR>the rising wing is less stalled than the<BR>descending wing creating a rolling,<BR>yawing, and pitching motion.<BR>SPIRAL INSTABILITY¡ª<BR>A condition that exists when the static<BR>directional stability of the airplane is<BR>very strong as compared to the effect<BR>of its dihedral in maintaining lateral<BR>equilibrium.<BR>SPIRALING SLIPSTREAM¡ªThe<BR>slipstream of a propeller-driven<BR>airplane rotates around the airplane.<BR>This slipstream strikes the left side of<BR>the vertical fin, causing the airplane to<BR>yaw slightly. Vertical stabilizer offset<BR>is sometimes used by aircraft designers<BR>to counteract this tendency.<BR>Glossary.qxd 5/7/04 10:46 AM Page G-13<BR>G-14<BR>STANDARD ATMOSPHERE¡ª<BR>At sea level, the standard atmosphere<BR>consists of a barometric pressure of<BR>29.92 inches of mercury (in. Hg.) or<BR>1013.2 millibars, and a temperature of<BR>15¡ãC (59¡ãF). Pressure and temperature<BR>normally decrease as altitude<BR>increases. The standard lapse rate in<BR>the lower atmosphere for each 1,000<BR>feet of altitude is approximately 1 in.<BR>Hg. and 2¡ãC (3.5¡ãF). For example, the<BR>standard pressure and temperature at<BR>3,000 feet mean sea level (MSL) is<BR>26.92 in. Hg. (29.92 - 3) and 9¡ãC<BR>(15¡ãC - 6¡ãC).<BR>STANDARD DAY¡ª<BR>See STANDARD ATMOSPHERE.<BR>STANDARD EMPTY WEIGHT<BR>(GAMA)¡ªThis weight consists of<BR>the airframe, engines, and all items of<BR>operating equipment that have fixed<BR>locations and are permanently<BR>installed in the airplane; including<BR>fixed ballast, hydraulic fluid, unusable<BR>fuel, and full engine oil.<BR>STANDARD WEIGHTS¡ªThese<BR>have been established for numerous<BR>items involved in weight and balance<BR>computations. These weights should<BR>not be used if actual weights are<BR>available.<BR>STANDARD-RATE TURN¡ªA turn<BR>at the rate of 3&ordm; per second which<BR>enables the airplane to complete a<BR>360&ordm; turn in 2 minutes.<BR>STARTER/GENERATOR¡ª<BR>A combined unit used on turbine<BR>engines. The device acts as a starter<BR>for rotating the engine, and after<BR>running, internal circuits are shifted to<BR>convert the device into a generator.<BR>STATIC STABILITY¡ªThe initial<BR>tendency an aircraft displays when<BR>disturbed from a state of equilibrium.<BR>STATION¡ªA location in the<BR>airplane that is identified by a number<BR>designating its distance in inches from<BR>the datum. The datum is, therefore,<BR>identified as station zero. An item<BR>located at station +50 would have an<BR>arm of 50 inches.<BR>TAXIWAY LIGHTS¡ª<BR>Omnidirectional lights that outline the<BR>edges of the taxiway and are blue in<BR>color.<BR>TAXIWAY TURNOFF LIGHTS¡ª<BR>Flush lights which emit a steady green<BR>color.<BR>TETRAHEDRON¡ª<BR>A large, triangular-shaped, kite-like<BR>object installed near the runway.<BR>Tetrahedrons are mounted on a pivot<BR>and are free to swing with the wind to<BR>show the pilot the direction of the<BR>wind as an aid in takeoffs and<BR>landings.<BR>THROTTLE¡ªThe valve in a<BR>carburetor or fuel control unit that<BR>determines the amount of fuel-air<BR>mixture that is fed to the engine.<BR>THRUST LINE¡ªAn imaginary line<BR>passing through the center of the<BR>propeller hub, perpendicular to the<BR>plane of the propeller rotation.<BR>THRUST REVERSERS¡ªDevices<BR>which redirect the flow of jet exhaust<BR>to reverse the direction of thrust.<BR>THRUST¡ªThe force which imparts<BR>a change in the velocity of a mass.<BR>This force is measured in pounds but<BR>has no element of time or rate. The<BR>term, thrust required, is generally<BR>associated with jet engines. A forward<BR>force which propels the airplane<BR>through the air.<BR>TIMING¡ªThe application of<BR>muscular coordination at the proper<BR>instant to make flight, and all<BR>maneuvers incident thereto, a constant<BR>smooth process.<BR>TIRE CORD¡ªWoven metal wire<BR>laminated into the tire to provide extra<BR>strength. A tire showing any cord<BR>must be replaced prior to any further<BR>flight.<BR>TORQUE METER¡ªAn indicator<BR>used on some large reciprocating<BR>engines or on turboprop engines to<BR>indicate the amount of torque the<BR>engine is producing.<BR>STICK PULLER¡ªA device that<BR>applies aft pressure on the control<BR>column when the airplane is approaching<BR>the maximum operating speed.<BR>STICK PUSHER¡ªA device that<BR>applies an abrupt and large forward<BR>force on the control column when the<BR>airplane is nearing an angle of attack<BR>where a stall could occur.<BR>STICK SHAKER¡ªAn artificial<BR>stall warning device that vibrates the<BR>control column.<BR>STRESS RISERS¡ª<BR>A scratch, groove, rivet hole, forging<BR>defect or other structural discontinuity<BR>that causes a concentration of stress.<BR>SUBSONIC¡ªSpeed below the speed<BR>of sound.<BR>SUPERCHARGER¡ªAn engine- or<BR>exhaust-driven air compressor used to<BR>provide additional pressure to the<BR>induction air so the engine can<BR>produce additional power.<BR>SUPERSONIC¡ªSpeed above the<BR>speed of sound.<BR>SUPPLEMENTAL TYPE<BR>CERTIFICATE (STC)¡ª<BR>A certificate authorizing an alteration<BR>to an airframe, engine, or component<BR>that has been granted an Approved<BR>Type Certificate.<BR>SWEPT WING¡ªA wing planform<BR>in which the tips of the wing are<BR>farther back than the wing root.<BR>TAILWHEEL AIRCRAFT¡ª<BR>SEE CONVENTIONAL LANDING<BR>GEAR.<BR>TAKEOFF ROLL<BR>(GROUND ROLL)¡ªThe total<BR>distance required for an aircraft to<BR>become airborne.<BR>TARGET REVERSER¡ªA thrust<BR>reverser in a jet engine in which<BR>clamshell doors swivel from the<BR>stowed position at the engine tailpipe<BR>to block all of the outflow and redirect<BR>some component of the thrust<BR>forward.<BR>Glossary.qxd 5/7/04 10:46 AM Page G-14<BR>G-15<BR>TORQUE SENSOR¡ª<BR>See TORQUE METER.<BR>TORQUE¡ª1.Aresistance to turning<BR>or twisting. 2. Forces that produce a<BR>twisting or rotating motion. 3. In an<BR>airplane, the tendency of the aircraft<BR>to turn (roll) in the opposite direction<BR>of rotation of the engine and propeller.<BR>TOTAL DRAG¡ªThe sum of the<BR>parasite and induced drag.<BR>TOUCHDOWN ZONE LIGHTS¡ª<BR>Two rows of transverse light bars<BR>disposed symmetrically about the<BR>runway centerline in the runway<BR>touchdown zone.<BR>TRACK¡ªThe actual path made over<BR>the ground in flight.<BR>TRAILING EDGE¡ªThe portion of<BR>the airfoil where the airflow over the<BR>upper surface rejoins the lower<BR>surface airflow.<BR>TRANSITION LINER¡ª<BR>The portion of the combustor that<BR>directs the gases into the turbine<BR>plenum.<BR>TRANSONIC¡ªAt the speed of<BR>sound.<BR>TRANSPONDER¡ªThe airborne<BR>portion of the secondary surveillance<BR>radar system. The transponder emits a<BR>reply when queried by a radar facility.<BR>TRICYCLE GEAR¡ªLanding gear<BR>employing a third wheel located on<BR>the nose of the aircraft.<BR>TRIM TAB¡ªA small auxiliary<BR>hinged portion of a movable control<BR>surface that can be adjusted during<BR>flight to a position resulting in a<BR>balance of control forces.<BR>TRIPLE SPOOL ENGINE¡ª<BR>Usually a turbofan engine design<BR>where the fan is the N1 compressor,<BR>followed by the N2 intermediate<BR>compressor, and the N3 high pressure<BR>compressor, all of which rotate on<BR>separate shafts at different speeds.<BR>TURBINE SECTION¡ªThe section<BR>of the engine that converts high<BR>pressure high temperature gas into<BR>rotational energy.<BR>TURBOCHARGER¡ª<BR>An air compressor driven by exhaust<BR>gases, which increases the pressure of<BR>the air going into the engine through<BR>the carburetor or fuel injection<BR>system.<BR>TURBOFAN ENGINE¡ªA turbojet<BR>engine in which additional propulsive<BR>thrust is gained by extending a portion<BR>of the compressor or turbine blades<BR>outside the inner engine case. The<BR>extended blades propel bypass air<BR>along the engine axis but between the<BR>inner and outer casing. The air is not<BR>combusted but does provide additional<BR>thrust.<BR>TURBOJET ENGINE¡ªA jet<BR>engine incorporating a turbine-driven<BR>air compressor to take in and compress<BR>air for the combustion of fuel,<BR>the gases of combustion being used<BR>both to rotate the turbine and create a<BR>thrust producing jet.<BR>TURBOPROP ENGINE¡ªAturbine<BR>engine that drives a propeller through<BR>a reduction gearing arrangement.<BR>Most of the energy in the exhaust<BR>gases is converted into torque, rather<BR>than its acceleration being used to<BR>propel the aircraft.<BR>TURBULENCE¡ªAn occurrence in<BR>which a flow of fluid is unsteady.<BR>TURN COORDINATOR¡ªA rate<BR>gyro that senses both roll and yaw due<BR>to the gimbal being canted. Has<BR>largely replaced the turn-and-slip<BR>indicator in modern aircraft.<BR>TURN-AND-SLIP INDICATOR¡ª<BR>Aflight instrument consisting of a rate<BR>gyro to indicate the rate of yaw and a<BR>curved glass inclinometer to indicate<BR>the relationship between gravity and<BR>centrifugal force. The turn-and-slip<BR>indicator indicates the relationship<BR>between angle of bank and rate of<BR>yaw. Also called a turn-and-bank<BR>indicator.<BR>TROPOPAUSE¡ªThe boundary<BR>layer between the troposphere and the<BR>mesosphere which acts as a lid to<BR>confine most of the water vapor, and<BR>the associated weather, to the<BR>troposphere.<BR>TROPOSPHERE¡ªThe layer of the<BR>atmosphere extending from the<BR>surface to a height of 20,000 to 60,000<BR>feet depending on latitude.<BR>TRUE AIRSPEED (TAS)¡ª<BR>Calibrated airspeed corrected for altitude<BR>and nonstandard temperature.<BR>Because air density decreases with an<BR>increase in altitude, an airplane has to<BR>be flown faster at higher altitudes to<BR>cause the same pressure difference<BR>between pitot impact pressure and<BR>static pressure. Therefore, for a given<BR>calibrated airspeed, true airspeed<BR>increases as altitude increases; or for a<BR>given true airspeed, calibrated airspeed<BR>decreases as altitude increases.<BR>TRUE ALTITUDE¡ªThe vertical<BR>distance of the airplane above sea<BR>level¡ªthe actual altitude. It is often<BR>expressed as feet above mean sea<BR>level (MSL). Airport, terrain, and<BR>obstacle elevations on aeronautical<BR>charts are true altitudes.<BR>T-TAIL¡ªAn aircraft with the<BR>horizontal stabilizer mounted on the<BR>top of the vertical stabilizer, forming<BR>a T.<BR>TURBINE BLADES¡ªThe portion<BR>of the turbine assembly that absorbs<BR>the energy of the expanding gases and<BR>converts it into rotational energy.<BR>TURBINE OUTLET<BR>TEMPERATURE (TOT)¡ª<BR>The temperature of the gases as they<BR>exit the turbine section.<BR>TURBINE PLENUM¡ªThe portion<BR>of the combustor where the gases are<BR>collected to be evenly distributed to<BR>the turbine blades.<BR>TURBINE ROTORS¡ªThe portion<BR>of the turbine assembly that mounts to<BR>the shaft and holds the turbine blades<BR>in place.<BR>Glossary.qxd 5/7/04 10:46 AM Page G-15<BR>G-16<BR>TURNING ERROR¡ªOne of the<BR>errors inherent in a magnetic compass<BR>caused by the dip compensating<BR>weight. It shows up only on turns to or<BR>from northerly headings in the<BR>Northern Hemisphere and southerly<BR>headings in the Southern Hemisphere.<BR>Turning error causes the compass to<BR>lead turns to the north or south and lag<BR>turns away from the north or south.<BR>ULTIMATE LOAD FACTOR¡ª<BR>In stress analysis, the load that causes<BR>physical breakdown in an aircraft or<BR>aircraft component during a strength<BR>test, or the load that according to<BR>computations, should cause such a<BR>breakdown.<BR>UNFEATHERING<BR>ACCUMULATOR¡ªTanks that hold<BR>oil under pressure which can be used<BR>to unfeather a propeller.<BR>UNICOM¡ª<BR>A nongovernment air/ground radio<BR>communication station which may<BR>provide airport information at public<BR>use airports where there is no tower or<BR>FSS.<BR>UNUSABLE FUEL¡ªFuel that<BR>cannot be consumed by the engine.<BR>This fuel is considered part of the<BR>empty weight of the aircraft.<BR>USEFUL LOAD¡ªThe weight of the<BR>pilot, copilot, passengers, baggage,<BR>usable fuel, and drainable oil. It is the<BR>basic empty weight subtracted from<BR>the maximum allowable gross weight.<BR>This term applies to general aviation<BR>aircraft only.<BR>UTILITY CATEGORY¡ª<BR>An airplane that has a seating<BR>configuration, excluding pilot seats,<BR>of nine or less, a maximum<BR>certificated takeoff weight of 12,500<BR>pounds or less, and intended for<BR>limited acrobatic operation.<BR>V-BARS¡ªThe flight director<BR>displays on the attitude indicator that<BR>provide control guidance to the pilot.<BR>V-SPEEDS¡ªDesignated speeds for a<BR>specific flight condition.<BR>VFE¡ªThe maximum speed with the<BR>flaps extended. The upper limit of the<BR>white arc.<BR>VFO¡ªThe maximum speed that the<BR>flaps can be extended or retracted.<BR>VFR TERMINAL AREA<BR>CHARTS (1:250,000)¡ª<BR>Depict Class B airspace which<BR>provides for the control or<BR>segregation of all the aircraft within<BR>the Class B airspace. The chart depicts<BR>topographic information and<BR>aeronautical information which<BR>includes visual and radio aids<BR>to navigation, airports, controlled<BR>airspace, restricted areas, obstructions,<BR>and related data.<BR>V-G DIAGRAM¡ªA chart that<BR>relates velocity to load factor. It is<BR>valid only for a specific weight,<BR>configuration, and altitude and shows<BR>the maximum amount of positive or<BR>negative lift the airplane is capable of<BR>generating at a given speed. Also<BR>shows the safe load factor limits and<BR>the load factor that the aircraft can<BR>sustain at various speeds.<BR>VISUAL APPROACH SLOPE<BR>INDICATOR (VASI)¡ª<BR>The most common visual glidepath<BR>system in use. The VASI provides<BR>obstruction clearance within 10¡ã of<BR>the extended runway centerline, and<BR>to 4 nautical miles (NM) from the<BR>runway threshold.<BR>VISUAL FLIGHT<BR>RULES (VFR)¡ª<BR>Code of Federal Regulations that govern<BR>the procedures for conducting<BR>flight under visual conditions.<BR>VLE¡ªLanding gear extended speed.<BR>The maximum speed at which an<BR>airplane can be safely flown with the<BR>landing gear extended.<BR>VLOF¡ªLift-off speed. The speed at<BR>which the aircraft departs the runway<BR>during takeoff.<BR>VLO¡ªLanding gear operating speed.<BR>The maximum speed for extending or<BR>retracting the landing gear if using an<BR>airplane equipped with retractable<BR>landing gear.<BR>VAPOR LOCK¡ªA condition in<BR>which air enters the fuel system and it<BR>may be difficult, or impossible, to<BR>restart the engine. Vapor lock may<BR>occur as a result of running a fuel tank<BR>completely dry, allowing air to enter<BR>the fuel system. On fuel-injected<BR>engines, the fuel may become so hot it<BR>vaporizes in the fuel line, not allowing<BR>fuel to reach the cylinders.<BR>VA¡ªThe design maneuvering speed.<BR>This is the ¡°rough air¡± speed and the<BR>maximum speed for abrupt<BR>maneuvers. If during flight, rough air<BR>or severe turbulence is encountered,<BR>reduce the airspeed to maneuvering<BR>speed or less to minimize stress on the<BR>airplane structure. It is important to<BR>consider weight when referencing this<BR>speed. For example, VA may be 100<BR>knots when an airplane is heavily<BR>loaded, but only 90 knots when the<BR>load is light.<BR>VECTOR¡ªA force vector is a<BR>graphic representation of a force and<BR>shows both the magnitude and<BR>direction of the force.<BR>VELOCITY¡ªThe speed or rate of<BR>movement in a certain direction.<BR>VERTICAL AXIS¡ªAn imaginary<BR>line passing vertically through the<BR>center of gravity of an aircraft. The<BR>vertical axis is called the z-axis or the<BR>yaw axis.<BR>VERTICAL CARD COMPASS¡ª<BR>Amagnetic compass that consists of<BR>an azimuth on a vertical card,<BR>resembling a heading indicator with a<BR>fixed miniature airplane to accurately<BR>present the heading of the aircraft.<BR>The design uses eddy current<BR>damping to minimize lead and lag<BR>during turns.<BR>VERTICAL<BR>SPEED INDICATOR (VSI)¡ª<BR>An instrument that uses static pressure<BR>to display a rate of climb or descent in<BR>feet per minute. The VSI can also<BR>sometimes be called a vertical<BR>velocity indicator (VVI).<BR>VERTICAL STABILITY¡ªStability<BR>about an aircraft¡¯s vertical axis. Also<BR>called yawing or directional stability.<BR>Glossary.qxd 5/7/04 10:46 AM Page G-16<BR>G-17<BR>VMC¡ªMinimum control airspeed.<BR>This is the minimum flight speed at<BR>which a twin-engine airplane can be<BR>satisfactorily controlled when an<BR>engine suddenly becomes inoperative<BR>and the remaining engine is at takeoff<BR>power.<BR>VMD¡ªMinimum drag speed.<BR>VMO¡ªMaximum operating speed<BR>expressed in knots.<BR>VNE¡ªNever-exceed speed. Operating<BR>above this speed is prohibited since it<BR>may result in damage or structural<BR>failure. The red line on the airspeed<BR>indicator.<BR>VNO¡ªMaximum structural cruising<BR>speed. Do not exceed this speed<BR>except in smooth air. The upper limit<BR>of the green arc.<BR>VP¡ªMinimum dynamic hydroplaning<BR>speed. The minimum speed<BR>required to start dynamic<BR>hydroplaning.<BR>VR¡ªRotation speed. The speed that<BR>the pilot begins rotating the aircraft<BR>prior to lift-off.<BR>VS0¡ªStalling speed or the minimum<BR>steady flight speed in the landing configuration.<BR>In small airplanes, this is<BR>the power-off stall speed at the maximum<BR>landing weight in the landing<BR>configuration (gear and flaps down).<BR>The lower limit of the white arc.<BR>VS1¡ªStalling speed or the minimum<BR>steady flight speed obtained in a<BR>specified configuration. For most<BR>airplanes, this is the power-off stall<BR>speed at the maximum takeoff weight<BR>in the clean configuration (gear up, if<BR>retractable, and flaps up). The lower<BR>limit of the green arc.<BR>VSSE¡ªSafe, intentional one-engine<BR>inoperative speed. The minimum<BR>speed to intentionally render the<BR>critical engine inoperative.<BR>V-TAIL¡ªA design which utilizes<BR>two slanted tail surfaces to perform<BR>equal to the mass of the body times<BR>the local value of gravitational<BR>acceleration. One of the four main<BR>forces acting on an aircraft.<BR>Equivalent to the actual weight of the<BR>aircraft. It acts downward through the<BR>aircraft¡¯s center of gravity toward the<BR>center of the Earth. Weight opposes<BR>lift.<BR>WEIGHT AND BALANCE¡ªThe<BR>aircraft is said to be in weight and<BR>balance when the gross weight of the<BR>aircraft is under the max gross weight,<BR>and the center of gravity is within<BR>limits and will remain in limits for the<BR>duration of the flight.<BR>WHEELBARROWING¡ª<BR>A condition caused when forward<BR>yoke or stick pressure during takeoff<BR>or landing causes the aircraft to ride<BR>on the nosewheel alone.<BR>WIND CORRECTION ANGLE¡ª<BR>Correction applied to the course to<BR>establish a heading so that track will<BR>coincide with course.<BR>WIND<BR>DIRECTION INDICATORS¡ª<BR>Indicators that include a wind sock,<BR>wind tee, or tetrahedron. Visual<BR>reference will determine wind<BR>direction and runway in use.<BR>WIND SHEAR¡ªA sudden, drastic<BR>shift in windspeed, direction, or both<BR>that may occur in the horizontal or<BR>vertical plane.<BR>WINDMILLING¡ªWhen the air<BR>moving through a propeller creates<BR>the rotational energy.<BR>WINDSOCK¡ªA truncated cloth<BR>cone open at both ends and mounted<BR>on a freewheeling pivot that indicates<BR>the direction from which the wind is<BR>blowing.<BR>WING¡ªAirfoil attached to each side<BR>of the fuselage and are the main<BR>lifting surfaces that support the<BR>airplane in flight.<BR>the same functions as the surfaces of a<BR>conventional elevator and rudder<BR>configuration. The fixed surfaces act<BR>as both horizontal and vertical<BR>stabilizers.<BR>VX¡ªBest angle-of-climb speed. The<BR>airspeed at which an airplane gains the<BR>greatest amount of altitude in a given<BR>distance. It is used during a short-field<BR>takeoff to clear an obstacle.<BR>VXSE¡ªBest angle of climb speed with<BR>one engine inoperative. The airspeed<BR>at which an airplane gains the greatest<BR>amount of altitude in a given distance<BR>in a light, twin-engine airplane<BR>following an engine failure.<BR>VY¡ªBest rate-of-climb speed. This<BR>airspeed provides the most altitude<BR>gain in a given period of time.<BR>VYSE¡ªBest rate-of-climb speed with<BR>one engine inoperative. This airspeed<BR>provides the most altitude gain in a<BR>given period of time in a light, twinengine<BR>airplane following an engine<BR>failure.<BR>WAKE TURBULENCE¡ªWingtip<BR>vortices that are created when an<BR>airplane generates lift. When an<BR>airplane generates lift, air spills over<BR>the wingtips from the high pressure<BR>areas below the wings to the low<BR>pressure areas above them. This flow<BR>causes rapidly rotating whirlpools of<BR>air called wingtip vortices or wake<BR>turbulence.<BR>WASTE GATE¡ªA controllable<BR>valve in the tailpipe of an aircraft<BR>reciprocating engine equipped with a<BR>turbocharger. The valve is controlled<BR>to vary the amount of exhaust gases<BR>forced through the turbocharger<BR>turbine.<BR>WEATHERVANE¡ªThe tendency of<BR>the aircraft to turn into the relative<BR>wind.<BR>WEIGHT¡ªA measure of the<BR>heaviness of an object. The force by<BR>which a body is attracted toward the<BR>center of the Earth (or another<BR>celestial body) by gravity. Weight is<BR>Glossary.qxd 5/7/04 10:46 AM Page G-17<BR>G-18<BR>WING AREA¡ªThe total surface of<BR>the wing (square feet), which includes<BR>control surfaces and may include<BR>wing area covered by the fuselage<BR>(main body of the airplane), and<BR>engine nacelles.<BR>WING SPAN¡ª<BR>The maximum distance from wingtip<BR>to wingtip.<BR>WINGTIP VORTICES¡ª<BR>The rapidly rotating air that spills over<BR>an airplane¡¯s wings during flight. The<BR>intensity of the turbulence depends on<BR>the airplane¡¯s weight, speed, and<BR>configuration. It is also referred to as<BR>ZERO FUEL WEIGHT¡ª<BR>The weight of the aircraft to include<BR>all useful load except fuel.<BR>ZERO SIDESLIP¡ªAmaneuver in a<BR>twin-engine airplane with one engine<BR>inoperative that involves a small<BR>amount of bank and slightly<BR>uncoordinated flight to align the<BR>fuselage with the direction of travel<BR>and minimize drag.<BR>ZERO THRUST<BR>(SIMULATED FEATHER)¡ª<BR>An engine configuration with a low<BR>power setting that simulates a<BR>propeller feathered condition.
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²é¿´ÍêÕû°æ±¾: glossary