Glossary

An aircraft with the horizontal stabilizer mounted on the top of the vertical stabilizer, forming a T.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

See terminal arrival area.

Pilot's Handbook of Aeronautical Knowledge, p. G-29

An instrument that measures the rotational speed of an object.

Aviation Maintenance Technician Handbook — Powerplant, p. G-27

A coat of finishing material sprayed on the surface and allowed to dry until the solvents evaporate. As soon as the solvents evaporate, a wet full-bodied coat of material is sprayed over it.

Aviation Maintenance Technician Handbook — Airframe, p. G-35

A clean, lintless rag, slightly damp with thinner. A tack rag is used to wipe a surface to prepare it to receive a coat of finishing material.

Aviation Maintenance Technician Handbook — Airframe, p. G-35

A method of holding parts together before they are permanently welded. The parts are assembled, and small spots of weld are placed at strategic locations to hold them in position.

Aviation Maintenance Technician Handbook — Airframe, p. G-35

Slightly sticky to the touch.

Aviation Maintenance Technician Handbook — Airframe, p. G-35

An electronic navigation system used by military aircraft, providing both distance and direction information.

Pilot's Handbook of Aeronautical Knowledge, p. G-29

Thermal anti-ice. A system used to prevent the formation of ice on an aircraft by flowing heated air inside the structure.

Aviation Maintenance Technician Handbook — Powerplant, p. G-27

The portion of the exhaust system of a gas turbine engine through which the gases leave. The tail pipe is often called the exhaust duct, or exhaust pipe.

Aviation Maintenance Technician Handbook — Powerplant, p. G-27

A rotor turning in a plane perpendicular to that of the main rotor and parallel to the longitudinal axis of the fuselage. It is used to control the torque of the main rotor and to provide movement about the yaw axis of the helicopter.

Helicopter Flying Handbook, p. G-5

Small vertical surfaces mounted underside of the horizontal stabilizer of some airplanes to increase the directional stability.

Aviation Maintenance Technician Handbook — Airframe, p. G-35

Per 14 CFR section 23.51: “the calibrated airspeed on the ground at which, as a result of engine failure or other reasons, the pilot assumed to have made a decision to continue or discontinue the takeoff.”

Pilot's Handbook of Aeronautical Knowledge, p. G-29

The distance required to complete an all-engines operative takeoff to the 35-foot height. It must be at least 15 percent less than the distance required for a one-engine inoperative engine takeoff. This distance is not normally a limiting factor as it is usually less than the one-engine inoperative takeoff distance.

Pilot's Handbook of Aeronautical Knowledge, p. G-29

An aural warning system that provides audio warning signals when the thrust levers are advanced for takeoff if the stabilizer, flaps, or speed brakes are in an unsafe condition for takeoff.

Aviation Maintenance Technician Handbook — Airframe, p. G-35

The weight of an aircraft just before beginning the takeoff roll. It is the ramp weight minus the weight of the fuel burned during start and taxi.

Aircraft Weight and Balance Handbook, p. G-5

A tapered shank sticking out from the blade of a knife or a file. The handle of a knife or file is mounted on the tang.

Aviation Maintenance Technician Handbook — Airframe, p. G-35

A trigonometric function comparing two sides of a right triangle as follows: opposite side Tan = adjacent side

Aviation Maintenance Technician Handbook — General, p. G-10

Instrument used to cut threads on the inside of a hole.

Aviation Maintenance Technician Handbook — General, p. G-10

The weight of any chocks or devices used to hold an aircraft on scales when it is weighed. The tare weight must be subtracted from the scale reading to get the net weight of the aircraft.

Aviation Maintenance Technician Handbook — General, p. G-10

See terrain awareness and warning system.

Pilot's Handbook of Aeronautical Knowledge, p. G-29

Omnidirectional lights that outline the edges of the taxiway and are blue in color.

Pilot's Handbook of Aeronautical Knowledge, p. G-29

Lights that are flush with the runway which emit a steady green color.

Pilot's Handbook of Aeronautical Knowledge, p. G-29

Time between overhauls. A time period specified by the manufacturer of an aircraft engine as the maximum length of time an engine should be operated between overhauls without normal wear causing parts of the engine to be worn beyond safe limits. TBO depends upon proper operation and maintenance in accordance with the engine manufacturer’s recommendations. The overhaul of an engine when it reaches its TBO hours is not mandatory, except for certain commercial operators that have the requirement written into their operations manual.

Aviation Maintenance Technician Handbook — Powerplant, p. G-27

See threshold crossing height.

Pilot's Handbook of Aeronautical Knowledge, p. G-29

Top dead center. The position of a piston in a reciprocating engine when the piston is at the top of its stroke and the wrist pin, crankpin, and center of the crankshaft are all in line.

Aviation Maintenance Technician Handbook — Powerplant, p. G-27

See touchdown zone elevation.

Pilot's Handbook of Aeronautical Knowledge, p. G-29

See Tower En Route Control.

Pilot's Handbook of Aeronautical Knowledge, p. G-30

The manner in which procedures are executed.

Pilot's Handbook of Aeronautical Knowledge, p. G-30

A hinge that permits the rotor blades of a semirigid rotor system to flap as a unit.

Helicopter Flying Handbook, p. G-5

The registered trade name for a fluorocarbon resin used to make hydraulic and pneumatic seals, hoses, and backup rings.

Aviation Maintenance Technician Handbook — Airframe, p. G-35

Tetraethyl lead.

Aviation Maintenance Technician Handbook — Powerplant, p. G-27

An FSS service providing continuously updated automated telephone recordings of area and/or route weather, airspace procedures, and special aviation-oriented announcements.

Pilot's Handbook of Aeronautical Knowledge, p. G-30

Trailing edge of the mean aerodynamic chord.

Aircraft Weight and Balance Handbook, p. G-5

Glass that has been heat-treated to increase its strength. Tempered glass is used in bird-proof, heated windshields for high-speed aircraft.

Aviation Maintenance Technician Handbook — Airframe, p. G-35

Process that reduces the brittleness imparted by hardening and produces definite physical properties within the steel. Tempering always follows, never precedes, the hardening operation.

Aviation Maintenance Technician Handbook — General, p. G-10

Weights that can be carried in a cargo compartment of an aircraft to move the location of CG for a specifi[c] fl[i]ght condition. Temporary ballast must be removed when the aircraft is weighed.

Aircraft Weight and Balance Handbook, p. G-2

Restriction to flight imposed in order to: 1. Protect persons and property in the air or on the surface from an existing or imminent flight associated hazard; 2. Provide a safe environment for the operation of disaster relief aircraft; 3. Prevent an unsafe congestion of sightseeing aircraft above an incident; 4. Protect the President, Vice President, or other public figures; and, 5. Provide a safe environment for space agency operations. Pilots are expected to check appropriate NOTAMs during flight planning when conducting flight in an area where a temporary flight restriction is in effect.

Pilot's Handbook of Aeronautical Knowledge, p. G-30

Maintaining an excessively strong grip on the control column, usually resulting in an overcontrolled situation.

Pilot's Handbook of Aeronautical Knowledge, p. G-30

A report established for the 5 statute mile radius around an airport. Utilizes the same descriptors and abbreviations as the METAR report.

Pilot's Handbook of Aeronautical Knowledge, p. G-30

A procedure to provide a new transition method for arriving aircraft equipped with FMS and/or GPS navigational equipment. The TAA contains a “T” structure that normally provides a NoPT for aircraft using the approach. Terminal instrument approach procedure (TERP). Prescribes standardized methods for use in designing instrument flight procedures.

Pilot's Handbook of Aeronautical Knowledge, p. G-30

Areas where participating pilots can receive additional radar services. The purpose of the service is to provide separation between all IFR operations and participating VFR aircraft.

Pilot's Handbook of Aeronautical Knowledge, p. G-30

A group of threaded studs mounted in a strip of insulating plastic. Electrical wires with crimped-on terminals are placed over the studs and secured with nuts.

Aviation Maintenance Technician Handbook — Airframe, p. G-35

A low-powered VOR that is normally located on an airport.

Aviation Maintenance Technician Handbook — Airframe, p. G-35

See terminal instrument approach procedure.

Pilot's Handbook of Aeronautical Knowledge, p. G-30

A timed-based system that provides information concerning potential hazards with fixed objects by using GPS positioning and a database of terrain and obstructions to provide true predictability of the upcoming terrain and obstacles.

Pilot's Handbook of Aeronautical Knowledge, p. G-30

A wide-blade, short-diameter propeller used on a reciprocating engine when it is run in a test cell. A test club applies a specific load to the engine and forces the maximum amount of air through the engine cooling fins.

Aviation Maintenance Technician Handbook — Powerplant, p. G-27

A heavy, oily, poisonous liquid, Pb(C2H5)4 , that is mixed into aviation gasoline to increase its critical pressure and temperature.

Aviation Maintenance Technician Handbook — Airframe, p. G-35

See temporary flight restriction.

Pilot's Handbook of Aeronautical Knowledge, p. G-30

A calibrated orifice in the mask adapter for a continuous-flow oxygen system that increases the flow of oxygen to a mask being used by a passenger who is known to have a heart or respiratory problem.

Aviation Maintenance Technician Handbook — Airframe, p. G-35

See hot dimpling.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

The ratio of the amount of useful work produced by a heat engine, to the amount of work that could be done by all of the heat energy available in the fuel burned.

Aviation Maintenance Technician Handbook — Powerplant, p. G-27

The increase in size of a material as temperature increases.

Aviation Maintenance Technician Handbook — General, p. G-10

A number that relates to the change in the physical dimensions of a material as the temperature of the material changes. The thermal expansion coefficient of aluminum is approximately twice that of steel.

Aviation Maintenance Technician Handbook — Powerplant, p. G-27

A relief valve in a hydraulic system that relieves pressure that builds up in an isolated part of the system because of heat. Thermal relief valves are set at a higher pressure than the system pressure relief valve.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

The sudden change in engine operating temperature that occurs when engine power is suddenly reduced at the same time the airspeed, thus the cooling, is increased. Thermal shock occurs when an aircraft is required to rapidly descend to a lower altitude.

Aviation Maintenance Technician Handbook — Powerplant, p. G-27

A special form of electrical resistor whose resistance varies with its temperature.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

A material with a negative temperature coefficient that causes its resistance to decrease as its temperature increases.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

A loop consisting of two kinds of wire, joined at the hot, or measuring, junction and at the cold junction in the instrument. The voltage difference between the two junctions is proportional to the temperature difference between the junctions. In order for the current to be meaningful, the resistance of the thermocouple is critical, and the leads are designed for a specific installation. Their length should not be altered. Thermocouples used to measure cylinder head temperature are usually made of iron and constantan, and thermocouples that measure exhaust gas temperature for turbine engines are made of chromel and alumel.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

A fire-detection system that works on the principle of the rate-of-temperature rise. Thermocouples are installed around the area to be protected, and one thermocouple is surrounded by thermal insulation that prevents its temperature changing rapidly. In the event of a fire, the temperature of all the thermocouples except the protected one will rise immediately and a fire warning will be initiated. In the case of a general overheat condition, the temperature of all the thermocouples will rise uniformly and there will be no fire warning.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

A type of plastic material that becomes soft when heated and hardens when cooled. Thermosetting resin.A type of plastic material that, when once hardened by heat, cannot be softened by being heated again.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

A plastic resin that, once it has been hardened by heat, cannot be softened by heating again.

Aviation Maintenance Technician Handbook — Powerplant, p. G-27

The last layer of the atmosphere that begins above the mesosphere and gradually fades away into space.

Pilot's Handbook of Aeronautical Knowledge, p. G-30

The component in a vapor-cycle cooling system that meters the refrigerant into the evaporator. The amount of refrigerant metered by the TEV is determined by the temperature and pressure of the refrigerant as it leaves the evaporator coils. The TEV changes the refrigerant from a high-pressure liquid into a low-pressure liquid.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

A temperature-sensitive valve that controls the temperature of oil in an aircraft engine. When the oil is cold, the valve shifts and directs the oil through the oil cooler.

Aviation Maintenance Technician Handbook — Powerplant, p. G-27

An electrical switch that closes a circuit when it is exposed to a specified high temperature.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

Materials, such as microballoons, added to a resin to give it body and increase its workability.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

A drum-shaped cam in a hydro-mechanical fuel control whose outer surface is ground so that followers riding on the surface, as the cam is moved up and down and rotated, can move mechanical linkages to control the fuel according to a preprogrammed schedule.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

The theoretical height above the runway threshold at which the aircraft’s glideslope antenna would be if the aircraft maintained the trajectory established by the mean ILS glideslope or MLS glidepath.

Pilot's Handbook of Aeronautical Knowledge, p. G-30

The control in an aircraft that regulates the power or thrust the pilot wants the engine to produce.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

See offset throw.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

The aerodynamic force produced by a propeller or turbojet engine as it forces a mass of air to the rear, behind the aircraft. A propeller produces its thrust by accelerating a large mass of air by a relatively small amount. A turbojet engine produces its thrust by accelerating a smaller mass of air by a much larger amount.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

The horsepower equivalent of the thrust produced by a turbojet engine. Thrust horsepower is found by multiplying the net thrust of the engine, measured in pounds, by the speed of the aircraft, measured in miles per hour, and then dividing this by 375.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

An imaginary line passing through the center of the propeller hub, perpendicular to the plane of the propeller rotation.

Pilot's Handbook of Aeronautical Knowledge, p. G-30

Tungsten inert welding is a form of electric arc welding in which the electrode is a nonconsumable tungsten wire. TIG welding is now called GTA (gas tungsten arc) welding.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

A table depicted on an instrument approach procedure chart that identifies the distance from the FAF to the MAP, and provides the time required to transit that distance based on various groundspeeds.

Pilot's Handbook of Aeronautical Knowledge, p. G-30

A patented piston-position indicator used to find the position of the piston in the cylinder of a reciprocating engine. The body of the Time-Rite indicator screws into a spark plug hole, and as the piston moves outward in the cylinder, it contacts the arm of the indicator. A pointer contacted by the arm moves across a calibrated scale to show the location of the piston in degrees of crankshaft rotation before top center.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

A turn in which the clock and the turn coordinator are used to change heading a definite number of degrees in a given time.

Pilot's Handbook of Aeronautical Knowledge, p. G-30

An indicator light used when timing magnetos to an engine to indicate when the breaker points open. Some timing lights incorporate an oscillator or buzzer that changes its pitch when the points open.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

The imaginary circular plane outlined by the rotor blade tips as they make a cycle of rotation.

Helicopter Flying Handbook, p. G-5

See traffic information service. Title 14 of the Code of Federal Regulations (14 CFR). Includes the federal aviation regulations governing the operation of aircraft, airways, and airmen.

Pilot's Handbook of Aeronautical Knowledge, p. G-30

Turbine inlet temperature. The temperature of the gases from the combustion section of a gas turbine engine as they enter the turbine inlet guide vanes or the first stage of the turbine.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

Thrust management computer.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

A condition of landing gear alignment in which the front of the tires are closer together than the rear. When the aircraft rolls forward, the wheels try to move closer together.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

A condition of landing gear alignment in which the front of the tires are further apart than the rear. When the aircraft rolls forward, the wheels try to move farther apart.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

A T-shaped handle fitted onto the end of a cable used to engage a simple starter with an overrunning clutch.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

The sum of the plus and minus allowance figures.

Aviation Maintenance Technician Handbook — General, p. G-10

An overhaul of the cylinders of an aircraft engine. The valves, pistons, and cylinders are overhauled, but the crankcase is not opened.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

An electrical coil wound around a ring-shaped core of highly permeable material.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

The tendency of a force to cause or change rotational motion of a body.

Aviation Maintenance Technician Handbook — General, p. G-10

The hinged link between the piston and cylinder of an oleo-type landing gear shock absorber. The torque links allow the piston to move freely in and out of the landing gear cylinder, but prevent it rotating. The torque links can be adjusted to achieve and maintain the correct wheel alignment. Torque links are also called scissors and nutcrackers.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

A tube in an aircraft control system that transmits a torsional force from the operating control to the control surface.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

An instrument used with some of the larger reciprocating engines and turboprop or turboshaft engines to measure the reaction between the propeller reduction gears and the engine case.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

A device in a spring tab to which the control horn is attached. For normal operation, the torsion rod acts as a fixed attachment point, but when the control surface loads are high, the torsion rod twists and allows the control horn to deflect the spring tab.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

The pressure a column of moving air will have if it is stopped.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

The temperature a column of moving air will have if it is stopped.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

The sum of the parasite drag and induced drag.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

The pressure a column of moving fluid would have if it were stopped from its motion. Total pressure is the sum of dynamic pressure and static pressure.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

The temperature of moving fluid that has been stopped from its motion. Total temperature is the sum of static temperature and the temperature rise caused by the ram effect as the fluid was stopped.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

The highest elevation in the first 3,000 feet of the landing surface, TDZE is indicated on the instrument approach procedure chart when straight-in landing minimums are authorized.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

Two rows of transverse light bars disposed symmetrically about the runway centerline in the runway touchdown zone.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

The control of IFR en route traffic within delegated airspace between two or more adjacent approach control facilities, designed to expedite traffic and reduce control and pilot communication requirements.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

A type of ring cowling used over a single-row radial engine. The cross section of the ring is in the form of an airfoil that produces enough forward thrust to compensate for the cooling drag of the engine. In the United States, townend rings are often called speed rings.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

See United States Terminal Procedures Publication.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

A transformer-rectifier unit. A TR unit reduces the voltage of AC and changes it into DC.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

The path followed by a blade segment of a propeller or helicopter rotor in one rotation.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

Flying a heading that will maintain the desired track to or from the station regardless of crosswind conditions. Traffic Alert Collision Avoidance System (TCAS). An airborne system developed by the FAA that operates independently from the ground-based Air Traffic Control system. Designed to increase flight deck awareness of proximate aircraft and to serve as a “last line of defense” for the prevention of midair collisions.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

An engine installed with the propeller facing the front of the aircraft. Thrust produced by the propeller mounted on a tractor engine pulls the aircraft through the air. tractor propeller. A propeller mounted on an airplane in such a way that its thrust pulls the aircraft.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

An airplane powerplant in which the propeller is mounted in the front, and its thrust pulls the airplane rather than pushes it.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

A ground-based service providing information to the flight deck via data link using the S-mode transponder and altitude encoder to improve the safety and efficiency of “see and avoid” flight through an automatic display that informs the pilot of nearby traffic.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

The thin edge at the rear of a propeller blade.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

To square up the Pratt truss used in an airplane wing. Trammel points are set on the trammel bar so they measure the distance between the center of the front spar, at the inboard compression strut, and at the center of the rear spar at the next compression strut outboard. The drag and antidrug wires are adjusted until the distance between the center of the rear spar at the inboard compression strut and the center of the front spar at the next outboard compression strut is exactly the same as that between the first points measured.

Aviation Maintenance Technician Handbook — Airframe, p. G-36

A wood or metal bar on which trammel points are mounted to compare distances.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

A set of sharp-pointed pins that protrude from the sides of a trammel bar.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

An FSS service, available in Alaska only, providing continuously updated automated broadcast of meteorological and aeronautical data over selected L/MF and VOR NAVAIDs.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

A device that changes energy from one form to another. Commonly used transducers change mechanical movement or pressures into electrical signals.

Aviation Maintenance Technician Handbook — Airframe, p. G-37; Aviation Maintenance Technician Handbook — Powerplant, p. G-28

A device that changes electrical energy of a given voltage into electrical energy at a different voltage level. It consists of two coils that are not electrically connected, but arranged so that the magnetic field surrounding one coil cuts through the other coil.

Aviation Maintenance Technician Handbook — General, p. G-10

A component in a large aircraft electrical system used to reduce the AC voltage and change it into DC for charging the battery and for operating DC equipment in the aircraft.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

A three-terminal device primarily used to amplify signals and control current within a circuit.

Aviation Maintenance Technician Handbook — General, p. G-11

The tendency of the single-rotor helicopter to move laterally during hovering flight. Also called tail rotor drift.

Helicopter Flying Handbook, p. G-5

The additional lift produced by a helicopter rotor as the helicopter changes from hovering to forward flight.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

Flight at an airspeed in which some air flowing over the aircraft is moving at a speed below the speed of sound, and other air is moving at a speed greater than the speed of sound.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

Flight at Mach numbers between 0.8 and 1.2. In this range, some air passing over the aircraft is subsonic, and some is supersonic.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

The airborne portion of the ATC radar beacon system.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

One of 4,096 four-digit discrete codes ATC assigns to distinguish between aircraft.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

The condition of increased drag and decreased lift in the aft portion of the rotor disk caused by the air having a greater induced velocity and angle in the aft portion of the disk.

Helicopter Flying Handbook, p. G-5

See gauge.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

A four-sided figure with one pair of parallel sides.

Aviation Maintenance Technician Handbook — General, p. G-11

Immediate indication of the direction of aircraft movement, as shown on instruments.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

A system for comparing engine performance parameters with a baseline of these same parameters established when the engine was new or newly overhauled. Parameters such as EGT, rpm, fuel flow, and oil consumption are monitored on every flight, and the baseline is plotted. Any deviation from a normal increase or decrease warns the technician of an impending problem.

Aviation Maintenance Technician Handbook — Powerplant, p. G-28

A three-sided figure in which the sum of the three angles equal 180°.

Aviation Maintenance Technician Handbook — General, p. G-11

A chemical compound, (CH3C6H4O)3PO, used in aviation gasoline to assist in scavenging the lead deposits left from the tetraethyl lead.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

Landing gear employing a third wheel located on the nose of the aircraft.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

The study of the relationships between the angles and sides of a triangle.

Aviation Maintenance Technician Handbook — General, p. G-11

To adjust the aerodynamic forces on the control surfaces so that the aircraft maintains the set attitude without any control input.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

A small control tab mounted on the trailing edge of a movable control surface. The tab may be adjusted to provide an aerodynamic force to hold the surface on which it is mounted deflected in order to trim the airplane for hands-off flight at a specified airspeed.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

A flight condition in which the aerodynamic forces acting on the control surfaces are balanced and the aircraft is able to fly straight and level with no control input.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

A circuit breaker that opens a circuit any time an excessive amount of current flows, regardless of the position of the circuit breaker’s operating handle.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

The boundary layer between the troposphere and the stratosphere which acts as a lid to confine most of the water vapor, and the associated weather, to the troposphere.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

The layer of the atmosphere extending from the surface to a height of 20,000 to 60,000 feet, depending on latitude.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

A procedure used in aircraft maintenance in which the operation of a malfunctioning system is analyzed to find the reason for the malfunction and to find a method for returning the system to its condition of normal operation.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

The actual height of an object above mean sea level.

Helicopter Flying Handbook, p. G-5

The power dissipated in the resistance of a circuit, or the power actually used in the circuit.

Aviation Maintenance Technician Handbook — General, p. G-11

Projections from the cylinder of a retractable landing gear strut about which the strut pivots retract.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

A fuselage design made up of supporting structural members that resist deformation by applied loads. The truss-type fuselage is constructed of steel or aluminum tubing. Strength and rigidity is achieved by welding the tubing together into a series of triangular shapes, called trusses.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

A type of structure made up of longitudinal beams and cross braces. Compression loads between the main beams are carried by rigid cross braces. Tension loads are carried by stays, or wires, that go from one main beam to the other and cross between the cross braces.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

Thrust specific fuel consumption. A measure of efficiency of a turbojet or turbofan engine. It is a measure of the number of pounds of fuel burned per hour for each pound of thrust produced.

Aviation Maintenance Technician Handbook — Powerplant, p. G-29

A rotary device actuated by impulse or reaction of a fluid flowing through vanes or blades that are arranges around a central shaft.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

The total pressure at the discharge of the low-pressure turbine in a dual-turbine axial-flow engine.

Pilot's Handbook of Aeronautical Knowledge, p. G-31

See gas turbine engine.

Aviation Maintenance Technician Handbook — Powerplant, p. G-29

A series of stator vanes immediately ahead of the first-stage turbine. The function of the inlet guide vanes is to divert the hot gases in the proper direction to enter the turbine, and to provide a series of convergent ducts which increase the velocity of the gases.

Aviation Maintenance Technician Handbook — Powerplant, p. G-29

Another name for turbine inlet guide vanes.

Aviation Maintenance Technician Handbook — Powerplant, p. G-29

A reciprocating engine that has power recovery turbines in its exhaust system. The power extracted from the exhaust by these turbines is directed into the engine crankshaft through a fluid coupling.

Aviation Maintenance Technician Handbook — Powerplant, p. G-29

An exhaust-driven air compressor used to increase the power of a reciprocating engine. A turbocharger uses a small radial inflow turbine in the exhaust system to drive a centrifugal-type air compressor on the turbine shaft. The compressed air is directed into the engine cylinders to increase power.

Aviation Maintenance Technician Handbook — Powerplant, p. G-29

A type of gas turbine engine that has a set of lengthened blades on the low-pressure compressor or low-pressure turbine. Air moved by these special blades bypasses the core engine and produces between 30% and 75% of the total thrust.

Aviation Maintenance Technician Handbook — Powerplant, p. G-29

A gas turbine engine that produces thrust by accelerating the air flowing through it. A minimum of energy is extracted by the turbine, with the majority used to produce an exhaust velocity much greater than the inlet velocity. The amount of thrust produced by the engine is determined by the amount the air is accelerated as it flows through the engine.

Aviation Maintenance Technician Handbook — Powerplant, p. G-29

A turbine engine in which several stages of turbines are used to extract as much energy as possible. The turbines drive reduction gears which in turn drive a propeller.

Aviation Maintenance Technician Handbook — Powerplant, p. G-29

A turbine engine in which several stages of turbines are used to extract as much energy as possible. The turbines drive shafts which are used to drive helicopter rotors, generators, or pumps.

Aviation Maintenance Technician Handbook — Powerplant, p. G-29

A centrifugal air compressor driven by exhaust gases flowing through a turbine. The compressed air is used to increase the power produced by a reciprocating engine at altitude.

Aviation Maintenance Technician Handbook — Powerplant, p. G-29

A rate gyroscopic flight instrument that gives the pilot an indication of the rate of rotation of the aircraft about its vertical axis. A ball in a curved glass tube shows the pilot the relationship between the centrifugal force and the force of gravity. This indicates whether or not the angle of bank is proper for the rate of turn. The turn and slip indicator shows the trim condition of the aircraft and serves as an emergency source of bank information in case the attitude gyro fails. Turn and slip indicators were formerly called needle and ball and turn and bank indicators.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

A rate gyro that senses both roll and yaw due to the gimbal being canted. Has largely replaced the turn-and-slip indicator in modern aircraft.

Pilot's Handbook of Aeronautical Knowledge, p. G-32

A component in an aircraft control system used to adjust cable tension. A turnbuckle consists of a brass tubular barrel with right-hand threads in one end and left-hand in the other end. Control cable terminals screw into the two ends of the barrel, and turning the barrel pulls the terminals together, shortening the cable.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

See Transcribed Weather Broadcast.

Pilot's Handbook of Aeronautical Knowledge, p. G-32

A metal cutting tool turned in a drill press or handheld drill motor. A twist drill has a straight shank and spiraled flutes. The cutting edge is ground on the end of the spiraled flutes.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

The power control on the end of the collective control.

Helicopter Flying Handbook, p. G-5

A stripe of paint on flexible hose that runs the length of the hose. If this stripe spirals around the hose after it is installed, it indicates the hose was twisted when it was installed. Twist stripes are also called lay lines.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

See dual-spool gas turbine engine.

Aviation Maintenance Technician Handbook — Powerplant, p. G-29

A constant-volume cycle of energy transformation that completes its operating cycle in two strikes of the piston, one up and one down. When the piston moves up, fuel is pulled into the crankcase, and at the same time the air/fuel mixture inside the cylinder is compressed. When the piston is near the top of its stroke, a spark plug ignites the compressed air/fuel mixture, and the burning and expanding gases force the piston down. Near the bottom of the stroke, the piston uncovers an exhaust port and the burned gases leave the cylinder. When the piston moves further down, it uncovers the intake port, and a fresh charge of fuel and air are forced from the crankcase into the cylinder.

Aviation Maintenance Technician Handbook — Powerplant, p. G-29

A fire detection system that uses individual thermoswitches installed around the inside of the area to be protected. These thermoswitches are wired in parallel between two separate circuits. A short or an open circuit can exist in either circuit without causing a fire warning.

Aviation Maintenance Technician Handbook — Airframe, p. G-37

The FAA issues a type certificate when a new aircraft, engine, propeller, etc., is found to meet safety standards set forth by the FAA. The TCDS lists the specifications, conditions and limitations under which airworthiness requirements were met for the specified product, such as engine make and model, fuel type, engine limits, airspeed limits, maximum weight, minimum crew, etc.

Aviation Maintenance Technician Handbook — General, p. G-11

The official specifications of an aircraft, engine, or propeller issued by the Federal Aviation Administration. The TCDS lists pertinent specifications for the device, and it is the responsibility of the mechanic and/or inspector to ensure, on each inspection, that the device meets these specifications.

Aviation Maintenance Technician Handbook — Airframe, p. G-38