Airplane Flying Handbook (FAA-H-8083-3A)
Glossary
Numbers and Symbols
14 CFR. (Title 14 of the Code of Federal Regulations. Federal regulations pertaining to aviation activity. Previously known as Federal
Aviation Regulations.
100-Hour Inspectio n. An inspection, iden tical in scop e to an annu al inspection. Mus t b e conducted every 100 hours of fligh t on
aircraft of under 12,500 pounds that are used for hire.
Absolute altitude. The vertical distance of an airplane above the terrain or above ground level (AGL).
Absolute ceiling. The altitude at which a climb is no longer possible.
Accelerate-go distance. The distance required to accelerate to V 1 with all engines at takeoff power, experience an engine failure at
V1 and continue the takeoff on the remaining engine(s). The runway required includes the distance required to climb to 35 feet by
which time V2 speed must be attained.
Accelerate-stop distance. The distance required to accelerate to V 1 with all engines at takeoff power, experience an engine failure at
V1, and abort the takeoff and bring the airplane to a stop using braking action only (use of thrust reversing is not considered).
Acceleration. Force involved in overcoming inertia, and which may be defined as a change in velocity per unit of time.
Accessories. Components th at are used with an engine, bu t are not a par t of th e engine itself. Units such as magnetos, carburetors,
generators, and fuel pumps are commonly installed engine accessories.
Adjustable stabilizer. A stabilizer that can be adjusted in fligh t to trim th e airplane, thereby allowing th e airplane to fly hands-off at
any given airspeed.
Adverse yaw. A condition of flight in which the nose of an airplane tends to yaw toward the outside of the turn. This is caused by the
higher induced drag on the outside wing, which is also producing more lift. Induced drag is a by-product of the lift associated with the
outside wing.
Aerodynamic ceiling. The point (altitude) at which, as the indicated airspeed decreases with altitude, it progressively merges with the
low speed buffet boundary where pre-stall buffet occurs for the airplane at a load factor of 1.0 G.
Aerodynamics. The science of th e action of air on an objec t, and with the motion of air on other gases. Aerodynam ics deals with the
production of lift by the aircraft, the relative wind, and the atmosphere.
Ailerons. Primary flight control surfaces mounted on the trailing edge of an airplane wing, near the tip. Ailerons control roll about the
longitudinal axis.
Air start. The act or instance of starting an aircraft’s engine while in flight, especially a jet engine after flameout.
Aircraft energy management. The process of planning, monitoring and controlling altitude and airspeed in relation to the airplane’s
energy state. Note that this definition is concerned with managing mechanical energy (altitude and airspeed) and addresses the safety
(flight control) side of energy management. It does not address the efficiency (aircraft performance) side of energy management,
which is concerned with how efficiently the engine generates mechanical energy from fuel and how efficiently the airframe spends that
energy in flight.
Aircraft logbooks. Journals containing a record of total operating time, repairs, alterations or inspections performed, and all
Airworthiness Directive (AD) notes complied with. A maintenance logbook should be kept for the airframe, each engine, and eac h
propeller.
Airfoil. An airfo il is any surface, such as a wing, propeller, rudder, or even a trim tab, which provid es aerodynamic force when it
interacts with a moving stream of air.
Airmanship. A sound acquaintance with the principles of flight, the ability to operate an airplane with competence and precision both
on the ground and in the air, and the exercise of sound judgment that results in optimal operational safety and efficiency.
Airplane Flight Manual (AFM). A document developed by the airplane manufacturer and approved by the Federal Aviation
Administration (FAA). It is specific to a particular make and model airplane by serial number and it contains operating procedures and
limitations.
Airplane Owner/Information Manual. A document developed by the airplane manufacturer containing general information about
the make and model of an airplane. The airplane owner’s manual is not FAA-approved and is not specific to a particular serial
numbered airplane. This manual is not kept current, and therefore cannot be substituted for the AFM/POH.
Airworthiness Certificate. A certificate issued by th e FAA to all aircraft that have been proven to mee t the minimum standards set
down by the Code of Federal Regulations.
Airworthiness Directive. A regulatory notice sent out by the FAA to the registered owner of an aircraft informing the owner of a
condition that prevents the aircraft from continuing to meet its conditions for airworthiness. Airworthiness Directives (AD) must be
complied with within the required time limit, and the fact of compliance, the date of compliance, and the method of compliance must
be recorded in the aircraft’s maintenance records.
Airworthiness. A condition in which the aircraft conforms to its type certificated design including supplemental type certificates and
field-approved alterations. The aircraft must also be in a condition for safe flight as determined by annual, 100-hour, preflight and any
other required inspections.
Alpha mode o f operatio n. Th e operatio n of a turbopro p engine that includes all o f the flight operations , from takeoff to landing.
Alpha operation is typically between 95 percent to 100 percent of the engine operating speed.
Alternate a ir. A dev ice which opens , eith er automatically or manually, to allo w induction airflow to continu e should the primary
induction air opening become blocked.
Alternate static source. A manual port that when opened allows the pitot static instruments to sense static pressure from an alternate
location should the primary static port become blocked.
Alternator/generator. A device that uses engine power to generate electrical power.
Altimeter. A flight instrument that indicates altitude by sensing pressure changes.
Altitude (AGL). The actual height above ground level (AGL) at which the aircraft is flying.
Altitude (MSL). The actual height above mean sea level (MSL) at which the aircraft is flying.
Altitude chamber. A dev ice that simulates high altitude conditions by reducing the interior pressure. The occupants will suffer from
the same physiological conditions as flight at high altitude in an unpressurized aircraft.
Altitude engine. A reciprocating aircraft engine having a rated takeoff power that is producible from sea level to an established higher
altitude.
Angle of attack. The acute angle between the chord line of the airfoil and the direction of the relative wind.
Angle of incidence. The angle formed by the chord line of the wing and a line parallel to the longitudinal axis of the airplane.
Annual inspection. Except as provided in regulation, no person may operate an aircraft unless, within the preceding 12 calendar
months, it has had an annual inspection, per 14 CFR part 91, section 91.409(a). This inspection is normally performed every 12
calendar months by an A&P technician holding an Inspection Authorization (14 CFR part 65, section 65.95(a)(2)).
Anti-icing. The prevention of the formation of ice on a surface. Ice may be prevented by using heat or by covering the surface with a
chemical that prevents water from reaching the surface. Anti-icing should not be confused with deicing, which is the removal of
ice after it has formed on the surface.
Attitude indicator. An instrument which uses an artificial horizon and miniature airplane to depict the position of the airplane
in relation to the true horizon. The attitude indicator senses roll as well as pitch, which is the up and down movement of the
airplane’s nose.
Attitude. The position of an aircraft as determined by the relationship of its axes and a reference, usually the earth’s horizon.
Autokinesis. This is caused by staring at a single point of light against a dark background for more than a few seconds. After a
few moments, the light appears to move on its own.
Autopilot. An automatic flight control system which keeps an aircraft in level flight or on a set course. Automatic pilots can be
directed by the pilot, or they may be coupled to a radio navigation signal.
Axes of an aircraft. Three imaginary lines that pass through an aircraft’s center of gravity. The axes can be considered as imaginary
axles around which the aircraft turns. The three axes pass through the center of gravity at 90° angles to each other. The axis from nose
to tail is the longitudinal axis, the axis that passes from wingtip to wingtip is the lateral axis, and the axis that passes vertically through
the center of gravity is the vertical axis.
Axial flow compressor. A type of compressor used in a turbine engine in which the airflow through the compressor is
essentially linear. An axial-flow compressor is made up of several stages of alternate rotors and stators. The compressor ratio is
determined by the decrease in area of the succeeding stages.
Back side of the power curve. Flight regime in which flight at a higher airspeed requires a lower power setting and a lower
airspeed requires a higher power setting in order to maintain altitude.
Balked landing. A go-around.
Ballast. Removable or permanently installed weight in an aircraft used to bring the center of gravity into the allowable range.
Balloon. The result of a too aggressive flare during landing causing the aircraft to climb.
Basic empty weig ht (GAMA). Basic empty weight includes the standard empty weight plus optional and special equipment that has
been installed.
Best angle of climb (VX). The speed at which the aircraft will produce the most gain in altitude in a given distance.
Best glide. The airspeed in which the aircraft glides the furthest for the least altitude lost when in non-powered flight.
Best rate of climb (VY). The speed at which the aircraft will produce the most gain in altitude in the least amount of time.
Blade face. The flat portion of a propeller blade, resembling the bottom portion of an airfoil.
Bleed air. Compressed air tapped from the compressor stages of a turbine engine by use of ducts and tubing. Bleed air can be used for
deice, anti-ice, cabin pressurization, heating, and cooling systems.
Bleed valve. In a turbine engine, a flapper valve, a pop off valve, or a bleed band designed to bleed off a portion of the compressor
air to the atmosphere. Used to maintain blade angle of attack and provide stall-free engine acceleration and deceleration.
Boost pump. An electrically driven fuel pump, usually of the centrifugal type, located in one of the fuel tanks. It is used to provide
fuel to the engine for starting and providing fuel pressure in the event of failure of the engine driven pump. It also pressurizes the fuel
lines to prevent vapor lock.
Buffeting. The beating of an aerodynam ic structure or surfac e by unsteady flow, gusts, etc. ; the irregular shaking or oscillation of a
vehicle component owing to turbulent air or separated flow.
Bus bar. An electrical power distribution poin t to which sever al circuits may b e connected. I t is often a solid m etal strip having a
number of terminals installed on it.
Bus tie. A switch that connects two or more bus bars. It is usually used when one generator fails and power is lost to its bus.
By closing the switch, the operating generator powers both buses.
Bypass air. The part of a turbofan’s induction air that bypasses the engine core.
Bypass ratio. The ratio of the mass airflow in pounds per second through the fan section of a turbofan engine to the mass airflow that
passes through the gas generator portion of the engine. Or, the ratio between fan mass airflow (lb/sec.) and core engine mass airflow
(lb/sec.).
Cabin pressurizatio n. A condition wher e pressurized air is forced into th e cabin simulating pressur e conditions at a much lower
altitude and increasing the aircraft occupants comfort.
Calibrated airspeed (CAS). Indicated airspeed corrected for installation error and instrument error. Although manufacturers attempt
to keep airspeed errors to a minimum, it is not possible to eliminate all errors throughout the airspeed operating range. At certain
airspeeds and with certain flap settings, the installation and instrument errors may total several knots. This error is generally greatest at
low airspeeds. In the cruising and higher airspeed ranges, indicated airspeed and calibrated airspeed are approximately the same. Refer
to the airspeed calibration chart to correct for possible airspeed errors.
Cambered. The camber of an airfoil is the characteristic curve of its upper and lower surfaces. The upper camber is more pronounced,
while the lower camber is comparatively flat. This causes the velocity of the airflow immediately above the wing to be much higher
than that below the wing.
Carburetor ice. Ice that forms insid e the carburetor du e to th e temperature drop caused by th e vaporization of th e fuel. Induction
system icing is an operational hazard because it can cut off the flow of the fuel/air charge or vary the fuel/air ratio.
Carburetor. 1. Pressure: A hydromechanical device employing a closed feed system from the fuel pump to the discharge nozzle. It
meters fuel through fixed jets according to the mass airflow through the throttle body and discharges it under a positive pressure.
Pressure carburetors are distinctly different from float-type carburetors, as they do not incorporate a vented float chamber or suction
pickup from a discharge nozzle located in the venturi tube. 2. Float-type: Consists essentially of a main air passage through which the
engine draws its supply of air, a mechanism to control the quantity of fuel discharged in relation to the flow of air, and a means of
regulating the quantity of fuel/air mixture delivered to the engine cylinders.
Cascade reverser. A thrust reverser normally found on turbofan engin es in which a blocker door and a series of cascad e vanes are
used to redirect exhaust gases in a forward direction.
Center of gravity (CG). The point at which an airplane would balance if it were possible to suspend it at that point. It is the mass
center of the airplane, or the theoretical point at which the entire weight of the airplane is assumed to be concentrated. It may be
expressed in inches from the reference datum, or in percent of mean aerodynamic chord (MAC). The location depends on the
distribution of weight in the airplane.
Center-of-gravity limits. The specified forward and af t points within which th e CG must be located during fligh t. These limits are
indicated on pertinent airplane specifications.
Center-of-gravity range. The distance between the forward and aft CG limits indicated on pertinent airplane specifications.
Centrifugal flow compressor. An impeller-shaped device that receives air at its center and slings air outward at high velocity into a
diffuser for increased pressure. Also referred to as a radial outflow compressor.
Chart Supplements. A listing of data on record with the FAA on all open- to-the-public airports, seaplane bases, heliports, military
facilities and selected private use airports specifically requested by the Department of Defense (DOD) for which a DOD instrument
approach procedure has been published in the U.S. Terminal Procedures Publication, airport sketches, NAVAIDs, communications
data, weather data sources, airspace, special notices, VFR waypoints, Airport Diagrams and operational procedures.
Chord line. An imaginary straight line drawn through an airfoil from the leading edge to the trailing edge.
Circuit breaker. A circuit-protecting device that opens the circuit in case of excess current flow. A circuit breaker differs from a fuse
in that it can be reset without having to be replaced.
Clear air turbulence. Turbulence not associated with any visible moisture.
Climb gradient. The ratio between distance traveled and altitude gained.
Cockpit resource management. Techniques designed to reduce pilot errors and manage errors that do occur utilizing cockpit human
resources. The assumption is that errors are going to happen in a complex system with error-prone humans.
Coefficient of lift. See lift coefficient.
Coffin corner. The flight regime where any increase in airspeed will induce high speed Mach buffet and any decrease in airspeed will
induce low speed Mach buffet.
Combustion chamber. The section of the engine into which fuel is injected and burned.
Common traffic advisory frequency (CTAF). The common frequency used by airport traffic to announce position reports in the
vicinity of the airport.
Complex aircraft. An aircraft with retractable landing gear, flaps, and a controllable-pitch propeller, or one that is turbine-powered.
Compression ratio. 1. In a reciprocating engine, the ratio of the volume of an engine cylinder with the piston at the bottom center to
the volume with the piston at top center. 2. In a turbine engine, the ratio of the pressure of the air at the discharge to the pressure of air
at the inlet.
Compressor bleed air. See bleed air.
Compressor bleed valves. See bleed valve.
Compressor section. The section of a turbine engine that increases the pressure and density of the air flowing through the engine.
Compressor stall. In gas turbine engines, a condition in an axial-flow compressor in which one or more stages of rotor blades fail to
pass air smoothly to the succeeding stages. A stall condition is caused by a pressure ratio that is incompatible with the engine rpm
Compressor stall will be indicated by a rise in exhaust temperature or rpm fluctuation, and if allowed to continue, may result in
flameout and physical damage to the engine.
Compressor surge. A severe compressor stall across the entire compressor that can result in severe damage if not quickly corrected.
This condition occurs with a complete stoppage of airflow or a reversal of airflow.
Condition lever. In a turbine engine, a powerplant control that controls the flow of fuel to the engine. The condition lever sets the
desired engine rpm within a narrow range between that appropriate for ground and flight operations.
Configuration. This is a general term, which normally refers to the position of the landing gear and flaps.
Constant speed propeller. A controllable-pitch propeller whose pitch is automatically varied in flight by a governor to maintain a
constant rpm in spite of varying air loads.
Control touch. The ability to sense the action of the airplane and its probable actions in the immediate future, with regard to attitude
and speed variations, by sensing and evaluation of varying pressures and resistance of the control surfaces transmitted through the
cockpit flight controls.
Controllability. A measure of the response of an aircraft relative to the pilot’s flight control inputs.
Controllable-pitch propeller. A propeller in which the blade angle can be changed during flight by a control in the cockpit.
Conventional landing gear. Landing gear employing a third rear-mounted wheel. These airplanes are also sometimes referred to as
tailwheel airplanes.
Coordinated flight. Application of all appropriate flight and power controls to prevent slipping or skidding in any flight condition.
Coordination. The ability to use the hands and feet together subconsciously and in the proper relationship to produce desired results
in the airplane.
Core airflow. Air drawn into the engine for the gas generator.
Cowl flaps. Devices arranged around certain air-cooled engine cowlings which may be opened or closed to regulate the flow of air
around the engine.
Crab. A flight condition in which the nose of the airplane is pointed into the wind a sufficient amount to counteract a crosswind and
maintain a desired track over the ground.
Crazing. Small fractures in aircraft windshields and windows caused from being exposed to the ultraviolet rays of the sun and
temperature extremes.
Critical altitude. The maximum altitude under standard atmospheric conditions at which a turbocharged engine can produce its rated
horsepower.
Critical angle of attack. The angle of attack at which a wing stalls regardless of airspeed, flight attitude, or weight.
Critical engine. The engine whose failure has the most adverse effect on directional control.
Cross controlled. A condition where aileron deflection is in the opposite direction of rudder deflection.
Crossfeed. A system that allows either engine on a twin- engine airplane to draw fuel from any fuel tank.
Crosswind component. The wind component, measured in knots, at 90° to the longitudinal axis of the runway.
Current limiter. A device that limits the generator output to a level within that rated by the generator manufacturer.
Datum (reference datum). An imaginary vertical plane or line from which all measurements of moment arm are taken. The datum is
established by the manufacturer. Once the datum has been selected, all moment arms and the location of CG range are measured from
this point.
Decompression sickness. A condition where the low pressure at high altitudes allows bubbles of nitrogen to form in the blood and
joints causing severe pain. Also known as the bends.
Deicer boots. Inflatable rubber boots attached to the leading edge of an airfoil. They can be sequentially inflated and deflated to break
away ice that has formed over their surface.
Deicing. Removing ice after it has formed.
Delamination. The separation of layers.
Density altitude. This altitude is pressure altitude corrected for variations from standard temperature. When conditions are standard,
pressure altitude and density altitude are the same. If the temperature is above standard, the density altitude is higher than pressure
altitude. If the temperature is below standard, the density altitude is lower than pressure altitude. This is an important altitude because
it is directly related to the airplane’s performance.
Designated pilot examiner (DPE). An individual designated by the FAA to administer practical tests to pilot applicants.
Detonation. The sudden release of heat energy from fuel in an aircraft engine caused by the fuel-air mixture reaching its critical
pressure and temperature. Detonation occurs as a violent explosion rather than a smooth burning process.
Dewpoint. The temperature at which air can hold no more water.
Differential ailerons. Control surface rigged such that the aileron moving up moves a greater distance than the aileron moving down.
The up aileron produces extra parasite drag to compensate for the additional induced drag caused by the down aileron. This balancing
of the drag forces helps minimize adverse yaw.
Diffusion. Reducing the velocity of air causing the pressure to increase.
Directional stability. Stability about the vertical axis of an aircraft, whereby an aircraft tends to return, on its own, to flight aligned
with the relative wind when disturbed from that equilibrium state. The vertical tail is the primary contributor to directional stability,
causing an airplane in flight to align with the relative wind.
Ditching. Emergency landing in water.
Downwash. Air deflected perpendicular to the motion of the airfoil.
Drag curve. A visual representation of the amount of drag of an aircraft at various airspeeds.
Drag. An aerodynamic force on a body acting parallel and opposite to the relative wind. The resistance of the atmosphere to the
relative motion of an aircraft. Drag opposes thrust and limits the speed of the airplane.
Drift angle. Angle between heading and track.
Ducted-fan engine. An engine-propeller combination that has the propeller enclosed in a radial shroud. Enclosing the propeller
improves the efficiency of the propeller.
Dutch roll. A combination of rolling and yawing oscillations that normally occurs when the dihedral effects of an aircraft are more
powerful than the directional stability. Usually dynamically stable but objectionable in an airplane because of the oscillatory nature.
Dynamic hydroplaning. A condition that exists when landing on a surface with standing water deeper than the tread depth of the
tires. When the brakes are applied, there is a possibility that the brake will lock up and the tire will ride on the surface of the water,
much like a water ski. When the tires are hydroplaning, directional control and braking action are virtually impossible. An effective
anti-skid system can minimize the effects of hydroplaning.
Dynamic stability. The property of an aircraf t th at caus es it, when disturbed from straight-and-lev el fligh t, to develop forces or
moments that restore the original condition of straight and level.
Electrical bus. See bus bar.
Electrohydraulic. Hydraulic control which is electrically actuated.
Elevator. The horizontal, movable primary control surface in the tail section, or empennage, of an airplane. Th e elevator is hinged to
the trailing edge of the fixed horizontal stabilizer.
Emergency locator transmitter. A small, self-contained radio transmitter that will automatically, upon the impact of a crash, transmit
an emergency signal on 121.5, 243.0, or 406.0 MHz.
Empennage. The section of th e airplan e that consists of th e vertical stabilizer, the horizontal stabilizer, and th e associated control
surfaces.
Energy balance equation: According to this equation, the net transfer of mechanical energy into and out of the airplane (a function of
thrust minus drag) is always equal to the change in its total mechanical energy (a function of altitude and airspeed).
Energy distributio n error. An energy error wher e th e to tal mechanical energy is correc t, bu t th e distribution between potential
(altitude) and kin etic energy (airspeed) is no t correct relative to th e intended altitude-speed profile. When this error occurs, th e pilot
will observe that altitude and airspeed dev iate in opposite directions (e.g., higher and slower than desired ; or lower and f aster than
desired). An example would be an airplane on final approach that is above the desired glide slope and at a slower airspeed than
desired.
Energy error. An altitude and/or airspeed deviation from an intended target expressed in terms of energy. Depending on the
airplane’s total amount of energy and its distribution between altitud e and airspeed, energy errors ar e classified as total energy errors,
energy distribution errors, or a combination of both errors.
Energy exchange. Trading one form of energy (e.g., altitude) for another form (e.g., airspeed).
Energy height or total specific energy (E S). Measured in units of height (e.g., feet), it represents the airplane’s total energy per unit
weight. It is found by dividing the sum of potential energy and kinetic energy by the airplane’s weight. It also represents the maximum
height that an airplane would reach from its current altitude, if it were to trade all its speed for altitude.
Energy state. The airplane’s total mechanical energy and its distribution between altitude and airspeed.
Energy system. A flying airplane is an open energy system. That means that the airplane can gain energy from some source (e.g., fuel)
and lose energy to the environment (e.g., surrounding air) . In addition, energy can be added to or removed from the airplane’s total
mechanical energy stored as altitude and airspeed.
Engine press ure ratio (EPR). The ratio of turbin e discharg e pressur e divided by compressor in let pressure th at is used as an
indication of the amount of thrust being developed by a turbine engine.
Environmental systems. In an aircraf t, the systems, including th e supplemental oxygen systems, air conditioning systems, heaters,
and pressurization systems, which make it possible for an occupant to function at high altitude.
Equilibrium. A condition that exists within a body when the sum of the moments of all of the forces acting on the body is equal to
zero. In aerodynamics, equilibrium is when all opposing forces acting on an aircraft are balanced (steady, unaccelerated flight
conditions).
Equivalent shaft horsepower (ESHP). A measurement of the total horsepower of a turboprop engine, including th at provided by jet
thrust.
Exhaust gas temperat ure (EGT). The temperature of th e exhaust gases as they leave the cylinders of a reciprocating engin e or the
turbine section of a turbine engine.
Exhaust manifold. The part of the engine that collects exhaust gases leaving the cylinders.
Exhaust. The rear opening of a turbine engine exhaust duct. The nozzle acts as an orifice, the size of which determines the density and
velocity of the gases as they emerge from the engine.
False horizon. An optical illusion where the pilot confuses a row of lights along a road or other straight line as the horizon.
False start. See hung start.
Feathering propeller (feathered). A controllable pitch propeller with a pitch range sufficient to allow the blades to be turned parallel
to the line of flight to reduce drag and prevent further damage to an engine that has been shut down after a malfunction.
Fixation. A psychological condition where the pilot fixes attention on a single source of information and ignores all other sources.
Fixed-shaft turboprop engine. A turboprop engine where the gas producer spool is directly connected to the output shaft.
Fixed-pitch propellers. Propellers with fixed blade angles. Fixed-pitch propellers are designed as climb propellers, cruise propellers,
or standard propellers.
Flaps. Hinged portion of the trailing edge between the ailerons and fuselage. In some aircraft, ailerons and flaps are interconnected to
produce full-span “flaperons.” In either case, flaps change the lift and drag on the wing.
Flat pitch. A propeller configuration when the blade chord is aligned with the direction of rotation.
Flicker vertigo. A disorienting condition caused from flickering light off the blades of the propeller.
Flight director. An automatic flight control system in which the commands needed to fly the airplane are electronically computed and
displayed on a flight instrument. The commands are followed by the human pilot with manual control inputs or, in the case of an
autopilot system, sent to servos that move the flight controls.
Flight idle. Engine speed, usually in the 70-80 percent range, for minimum flight thrust.
Floating. A condition when landing where the airplane does not settle to the runway due to excessive airspeed.
Force (F). The energy applied to an object that attempts to cause the object to change its direction, speed, or motion. In aerodynamics,
it is expressed as F, T (thrust), L (lift), W (weight), or D (drag), usually in pounds.
Form drag. The part of parasite drag on a body resulting from the integrated effect of the static pressure acting normal to its surface
resolved in the drag direction.
Forward slip. A slip in which the airplane’s direction of motion continues the same as before the slip was begun. In a forward slip, the
airplane’s longitudinal axis is at an angle to its flightpath.
Free power turbine engine. A turboprop engine where the gas producer spool is on a separate shaft from the output shaft. The free
power turbine spins independently of the gas producer and drives the output shaft.
Friction drag. The part of parasitic drag on a body resulting from viscous shearing stresses over its wetted surface.
Frise-type aileron. Aileron having the nose portion projecting ahead of the hinge line. When the trailing edge of the aileron moves
up, the nose projects below the wing’s lower surface and produces some parasite drag, decreasing the amount of adverse yaw.
Fuel control unit. The fuel-metering device used on a turbine engine that meters the proper quantity of fuel to be fed into the burners
of the engine. It integrates the parameters of inlet air temperature, compressor speed, compressor discharge pressure, and exhaust gas
temperature with the position of the cockpit power control lever.
Fuel efficiency. Defined as the amount of fuel used to produce a specific thrust or horsepower divided by the total potential power
contained in the same amount of fuel.
Fuel heater. A radiator-like device which has fuel passing through the core. A heat exchange occurs to keep the fuel temperature
above the freezing point of water so that entrained water does not form ice crystals, which could block fuel flow.
Fuel injection. A fuel metering system used on some aircraft reciprocating engines in which a constant flow of fuel is fed to injection
nozzles in the heads of all cylinders just outside of the intake valve. It differs from sequential fuel injection in which a timed charge of
high-pressure fuel is sprayed directly into the combustion chamber of the cylinder.
Fuel load. The expendable part of the load of the airplane. It includes only usable fuel, not fuel required to fill the lines or that which
remains trapped in the tank sumps.
Fuel tank sump. A sampling port in the lowest part of the fuel tank that the pilot can utilize to check for contaminants in the fuel.
Fuselage. The section of the airplane that consists of the cabin and/or cockpit, containing seats for the occupants and the controls fo r
the airplane.
Gas generator. The basic power producing portion of a gas turbine engine and excluding such sections as the inlet duct, the fan
section, free power turbines, and tailpipe. Each manufacturer designates what is included as the gas generator, but generally consists of
the compressor, diffuser, combustor, and turbine.
Gas turbine engine. A form of heat engine in which burning fuel adds energy to compressed air and accelerates the air through the
remainder of the engine. Some of the energy is extracted to turn the air compressor, and the remainder accelerates the air to produce
thrust. Some of this energy can be converted into torque to drive a propeller or a system of rotors for a helicopter.
Glide ratio. The ratio between distance traveled and altitude lost during non-powered flight.
Glidepath. The path of an aircraft relative to the ground while approaching a landing.
Global position system (GPS). A satellite-based radio positioning, navigation, and time-transfer system.
Go-around. Terminating a landing approach.
Governing range. The range of pitch a propeller governor can control during flight.
Governor. A control which limits the maximum rotational speed of a device.