Glossary

See selective availability.

Pilot's Handbook of Aeronautical Knowledge, p. G-26

A piece of plywood glued to an aircraft structural member. The saddle gusset has a cutout to hold a backing block or strip tightly against the skin to allow a nailing strip to be used to apply pressure to a glued joint in the skin.

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

Society of Automotive Engineers. A professional organization that has formulated standards for the automotive and aviation industries.

Aviation Maintenance Technician Handbook — Powerplant, p. G-24

A location in a magneto that allows a spark to jump to ground from the secondary circuit before the voltage rises high enough to damage the secondary insulation.

Aviation Maintenance Technician Handbook — Powerplant, p. G-24

A high-performance glider.

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

A method of molding metal parts in a mold made of sand. A pattern that duplicates the part to be molded is made of wood and is covered with a special casting sand that contains a resin to bind it. The mold is separated along a special parting line, and the pattern is removed. The mold is put back together, and molten metal is poured into the cavity. When the metal cools, the sand is broken away from the molded part. Sand casting is less expensive than permanent-mold casting.

Aviation Maintenance Technician Handbook — Powerplant, p. G-24

A type of composite structural material in which a core material is bonded between face sheets of metal or resin-impregnated fabric.

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

Data broadcast by the GPS satellite containing very accurate orbital data for that satellite, atmospheric propagation data, and satellite clock error data.

Pilot's Handbook of Aeronautical Knowledge, p. G-26

Fabric in which the warp threads pass under one fill thread and over several others. Satin-weave fabrics are used when the lay-up must be made over complex shapes.

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

A measurement of viscosity (resistance to flow)of a lubricating oil. The number of seconds needed for 60 milliliters of oil at a specified temperature to flow through a calibrated orifice. The viscosity number used for commercial aviation engine lubricating oil relates closely to the SSU viscosity of the oil at 210 ºF.

Aviation Maintenance Technician Handbook — Powerplant, p. G-24

The first fundamental skill of instrument flight, also known as “cross-check;” the continuous and logical observation of instruments for attitude and performance information.

Pilot's Handbook of Aeronautical Knowledge, p. G-26

A joint in a wood structure in which the ends to be joined are cut in a long taper, normally about 12:1, and fastened together by gluing. A glued scarf joint makes a strong splice because the joint is made along the side of the wood fibers rather than along their ends.

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

The subsystem in the lubrication system of a gas turbine engine that collects oil after it has lubricated the bearings and gears and returns it to the oil tank.

Aviation Maintenance Technician Handbook — Powerplant, p. G-24

A diagram that locates components with respect to each other within a system.

Aviation Maintenance Technician Handbook — General, p. G-9

A type of service valve used in an air conditioning system. This is a spring-loaded valve much like the valve used to put air into a tire.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

Used as a type of shorthand to express very large or very small numbers. For example, to express 1,250,000,000,000 in scientific notation is 1.25 × 1012.

Aviation Maintenance Technician Handbook — General, p. G-9

The shape of the blades of the propellers mounted on UHB engines. The name is derived from the shape of a curved Asian sword that has its edge on the convex side. See UHB engine.

Aviation Maintenance Technician Handbook — Powerplant, p. G-24

A name commonly used for torque links. See torque links.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

Supersonic combustion ramjet. A special type of ramjet engine whose fuel can be ignited while the vehicle is mobbing at a supersonic speed.

Aviation Maintenance Technician Handbook — Powerplant, p. G-24

Scrim cloth can be used in repair applications or for reinforcement of other types of materials including fiberglass, concrete and some plastics. When fully cured, the scrim cloth will add reinforcement and mimic the expansion and contraction of the surrounding substrate.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

Severe damage to moving parts caused when one metal part moves across another without sufficient lubricant between them. Enough heat is generated by friction to cause the high points of the surfaces to weld together; continued movement tears, or scuffs, the metal.

Aviation Maintenance Technician Handbook — Powerplant, p. G-24

A recess around the filler neck of an aircraft fuel tank. Any fuel spilled when the tank is being serviced collects in the scupper and drains to the ground through a drain line rather than flowing into the aircraft structure.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

See simplified directional facility.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

A coastal breeze blowing from sea to land caused by the temperature difference when the land surface is warmer than the sea surface. The sea breeze usually occurs during the day and alternates with the land breeze that blows in the opposite direction at night.

Pilot's Handbook of Aeronautical Knowledge, p. G-26

A reciprocating engine that has had its sea-level rated horsepower increased by supercharging. This is the same as a ground-boosted engine.

Aviation Maintenance Technician Handbook — Powerplant, p. G-24

The atmospheric pressure at sea level. Average sea level pressure is 29.92 inches of mercury, or 1013.25 millibars.

Aviation Maintenance Technician Handbook — General, p. G-9

The winding in a magneto or ignition coil that connects to the distributor rotor. The secondary winding is normally made of very small diameter wire and has a large number of turns, typically about 20,000.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

Designed for visual navigation of slow- or medium-speed aircraft. Topographic information on these charts features the portrayal of relief, and a judicious selection of visual check points for VFR flight. Aeronautical information includes visual and radio aids to navigation, airports, controlled airspace, restricted areas, obstructions and related data.

Pilot's Handbook of Aeronautical Knowledge, p. G-26

A view obtained by cutting away part of an object to show the shape and construction at the cutting plane.

Aviation Maintenance Technician Handbook — General, p. G-9

A part of a gear wheel containing the hub and a portion of the rim with teeth.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

A heavy-duty, multiple-disc brake used on large, high-speed aircraft. Stators that are surfaced with a material that retains its friction characteristics at high temperatures are keyed to the axle. Rotors which are keyed into the wheels mesh with the stators. The rotors are made in segments to allow for cooling and for their large amounts of expansion.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

Selective calling system. Each aircraft operated by an airline is assigned a particular four-tone audio combination for identification purposes. A ground station keys the signal whenever contact with that particular aircraft is desired. The signal is decoded by the airborne selcal decoder and the crew alerted by the selcal warning system.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

A satellite technology permitting the Department of Defense (DOD) to create, in the interest of national security, a significant clock and ephemeris error in the satellites, resulting in a navigation error.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

A flow control valve used in hydraulic systems that directs pressurized fluid into one side of an actuator, and at the same time directs return fluid from the other side of the actuator back to the reservoir. There are two basic types of selector valves: open-center valves and closed-center valves. The four-port closed-center valve is the most frequently used type. See closed-center selector valve and open-center selector valve.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

The speed attained by a gas turbine engine during start-up that allows it to accelerate to its normal idling speed without assistance from the starter.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

A DC synchro system used in remote indicating instruments. The rotor in the indicator is a permanent magnet and the stator is a tapped toroidal coil. The transmitter is a circular potentiometer with DC power fed into its wiper which is moved by the object being monitored. The transmitter is connected to the indicator in such a way that rotation of the transmitter shaft varies the current in the sections of the indicator toroidal coil. The magnet in the indicator on which the pointer is mounted locks with the magnetic field produced by the coils and follows the rotation of the transmitter shaft.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

The woven edge of fabric used to prevent the material unraveling during normal handling. The selvage edge, which runs the length of the fabric parallel to the warp threads, is usually removed from materials used in composite construction.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

An inner ear organ that detects angular acceleration of the body.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

Any device based on either preferred conduction through a solid in one direction, as in rectifiers, or on a variation in conduction characteristics through a partially conductive material, as in a transistor.

Aviation Maintenance Technician Handbook — General, p. G-9

A two-element electrical component that allows current to pass through it in one direction, but blocks its passage in the opposite direction. A diode acts in an electrical system in the same way a check valve acts in a hydraulic system.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

A piezoelectric crystal that converts input energy of one form, such as pressure, into output energy of another, such as an electrical signal.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

A fuselage design that includes a substructure of bulkheads and/or formers, along with stringers, to support flight loads and stresses imposed on the fuselage.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

A form of aircraft stressed skin structure. Most of the strength of a semimonocoque structure is in the skin, but the skin is supported on a substructure of formers and stringers that give the skin its shape and increase its rigidity.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

A rotor system in which the blades are fixed to the hub, but are free to flap and feather.

Helicopter Flying Handbook, p. G-5

Heat that is added to a liquid causing a change in its temperature but not its physical state.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

A form of multipointer pneumatic altimeter with an adjustable barometric scale that allows the reference pressure to be set to any desired level.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

A measure of the signal strength needed to produce a distortion-free output in a radio receiver.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

A valve in a hydraulic system that requires a certain action to be completed before another action can begin. Sequence valves are used to assure that the hydraulically actuated wheel-well doors are completely open before pressure is directed to the landing gear to lower it.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

The most basic electrical circuit in which there is only one possible path for current to flow. Current must pass through the circuit components, the battery and the resistor, one after the other, or “in series.”

Aviation Maintenance Technician Handbook — General, p. G-9

An electrical circuit in which some of the components are connected in parallel and others are connected in series.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

A grouping of parallel resistors connected in series with other resistors.

Aviation Maintenance Technician Handbook — General, p. G-9

An electric motor with field coils connected in series with the armature.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

The highest altitude at which an aircraft can maintain a steady rate of climb of 100 feet per minute.

Aircraft Weight and Balance Handbook, p. G-4

Limits included in a reciprocating engine overhaul manual. If a part measures outside of the new-parts limits, but within the serviceable limits, it will not likely wear to the point of causing engine failure within the next TBO interval.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

An electrical or hydraulic actuator connected into a flight control system. A small force on the flight deck control is amplified by the servo and provides a large force to move the control surface.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

An electronic amplifier in an autopilot system that increases the signal from the autopilot enough that it can operate the servos that move the control surfaces.

Aviation Maintenance Technician Handbook — Airframe, p. G-30

A type of automatic control system in which part of the output is fed back into the input.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

A small movable tab built into the trailing edge of a primary control surface of an airplane. The flight deck controls move the tab in such a direction that it produces an aerodynamic force moving the surface on which it is mounted.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

The distance the jaws of a brake must be set back from the mold line to form a bend. Setback for a 90° bend is equal to the inside radius of the bend plus the thickness of the metal being bent. For a bend other than 90°, a K-factor must be used. See also K-factor.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

The horsepower actually available at a rotating shaft.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

A turbine engine used to drive an output shaft, commonly used in helicopters.

Helicopter Flying Handbook, p. G-5

Longitudinal cracks in a piece of wood, usually between two annual rings.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

A necked-down section of the drive shaft of a constant-displacement engine-driven fluid pump. If the pump should seize, the shear section will break and prevent the pump from being destroyed or the engine from being damaged. Some pumps use a shear pin rather than a shear section.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

The strength of a riveted joint in a sheet metal structure in which the rivets shear before the metal tears at the rivet holes.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

The length of time a product is good when it remains in its original unopened container.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

Super-high frequency.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

Electrical wire enclosed in a braided metal jacket. Electromagnetic energy radiated from the wire is trapped by the braid and is carried to ground.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

The electrically conductive covering placed around an electrical component to intercept and conduct to ground any electromagnetic energy radiated from the device.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

Abnormal, and often violent, vibration of the nose wheel of an airplane. Shimmying is usually caused by looseness of the nose wheel support mechanism or an unbalanced wheel.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

A small hydraulic shock absorber installed between the nose wheel fork and the nose wheel cylinder attached to the aircraft structure.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

Resilient mounting pads used to protect electronic equipment by absorbing low-frequency, high amplitude vibrations.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

A pressure wave formed in the air by a flight vehicle moving at a speed greater than the speed of sound. As the vehicle passes through the air, it produces sound waves that spread out in all directions. But since the vehicle is flying faster than these waves are moving, they build up and form a pressure wave at the front and rear of the vehicle. As the air passes through a shock wave it slows down, its static pressure increases, and its total energy decreases.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

The head of a rivet which is formed when the shank is upset.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

A low-resistance connection between two points in an electric circuit.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

The type of finish put on fabric-covered aircraft intended for show. This finish is usually made up of many coats of dope, with much sanding and rubbing of the surface between coats.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

A patented ignition system for reciprocating engines. An induction vibrator sends pulsating DC into a set of retard breaker points on one of the magnetos. This provides a hot and retarded spark for starting the engine.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

Field coils in an electric motor or generator that are connected in parallel with the armature.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

An automatic selector valve mounted on critical components such as landing gear actuation cylinders and brake cylinders. For normal operation, system fluid flows into the actuator through the shuttle valve, but if normal system pressure is lost, emergency system pressure forces the shuttle over and emergency fluid flows into the actuator.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

A flight deck flight control used on some of the fly-by-wire equipped airplanes. The stick is mounted rigidly on the side console of the flight deck, and pressures exerted on the stick by the pilot produce electrical signals that are sent to the computer that flies the airplane.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

See standard instrument departure procedures.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

A small window in the high side of a vapor-cycle cooling system. Liquid refrigerant flows past the sight glass, and if the charge of refrigerant is low, bubbles will be seen. A fully charged system has no bubbles in the refrigerant.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

A line drawn on a sheet metal layout that is one bend radius from the bend-tangent line. The sight line is lined up directly below the nose of the radius bar in a cornice brake. When the metal is clamped in this position, the bend tangent line is in the correct position for the start of the bend.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

The acronym for Significant Meteorological information. A weather advisory in abbreviated plain language concerning the occurrence or expected occurrence of potentially hazardous en route weather phenomena that may affect the safety of aircraft operations. SIGMET is warning information, hence it is of highest priority among other types of meteorological information provided to the aviation users.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

An indication of signal strength received compared to background noise, which is a measure of the adequacy of the received signal.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

A signed number can be either a positive or negative number. A positive number is a number that is greater than zero. A negative number is a number that is less than zero.

Aviation Maintenance Technician Handbook — General, p. G-9

Presents four panels showing forecast significant weather.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

A semiconductor electron control device. An SCR blocks current flow in both directions until a pulse of positive voltage is applied to its gate. It then conducts in its forward direction, while continuing to block current in its reverse direction.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

An elastomeric material made from silicone elastomers. Silicone rubber is compatible with fluids that attack other natural or synthetic rubbers.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

Transmission and reception on the same frequency.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

A NAVAID used for nonprecision instrument approaches. The final approach course is similar to that of an ILS localizer; however, the SDF course may be offset from the runway, generally not more than 3°, and the course may be wider than the localizer, resulting in a lower degree of accuracy.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

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

Aviation Maintenance Technician Handbook — General, p. G-9

A continuous waveform with a constant frequency and amplitude.

Aviation Maintenance Technician Handbook — General, p. G-9

A linear hydraulic or pneumatic actuator that uses fluid power for movement in one direction and a spring force for its return.

Aviation Maintenance Technician Handbook — Airframe, p. G-31

A hand-operated fluid pump that moves fluid only during one stroke of the pump handle. One stroke pulls the fluid into the pump and the other forces the fluid out.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

Aircraft brakes in which a single steel disc rotates with the wheel between two brake-lining blocks. When the brake is applied, the disc is clamped tightly between the lining blocks, and the friction slows the aircraft.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

The ability for a pilot to manage all resources effectively to ensure the outcome of the flight is successful.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

Brakes that uses the momentum of the aircraft rolling forward to help apply the brakes by wedging the brake shoe against the brake drum.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

A turboprop engine in which the propeller reduction gears are driven by the same shaft that drives the compressor for the gas generator.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

A type of axial-flow-compressor gas turbine engine that has only one rotating element.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

A porous material made by fusing powdered metal under heat and pressure.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

Pilot knowledge of where the aircraft is in regard to location, air traffic control, weather, regulations, aircraft status, and other factors that may affect flight.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

A simple rough drawing that is made rapidly and without much detail.

Aviation Maintenance Technician Handbook — General, p. G-9

A flight condition in which the rate of turn is too great for the angle of bank.

Helicopter Flying Handbook, p. G-5

Plates attached to the bottom of skid landing gear, protecting the skid.

Helicopter Flying Handbook, p. G-5

An uncoordinated turn in which the rate of turn is too great for the angle of bank, pulling the aircraft to the outside of the turn.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

The procedural, psychomotor, and perceptual skills used to control a specific aircraft or its systems. They are the airmanship abilities that are gained through conventional training, are perfected, and become almost automatic through experience.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

Drag generated between air molecules and the solid surface of the aircraft.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

A type of radiator used on some early liquid-cooled racing airplanes. The radiator was made of two thin sheets of brass, slightly separated so the heated coolant could flow between them. Skin radiators were mounted on the surface of the wing, on the sides of the fuselage, or on the floats of seaplanes. Air flowing over the smooth surface of the radiator removed heat from the coolant.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

The registered trade name for a synthetic, nonflammable, phosphate ester-base hydraulic fluid used in modern high-temperature hydraulic systems.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

The horizontal distance from the aircraft antenna to the ground station, due to line-of-sight transmission of the DME signal.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

A secondary control on an aircraft that allows it to fly at a high angle of attack without stalling. A slat is a section of leading edge of wing mounted on curved tracks that move into and out of the wing on rollers.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

A system whereby the heading gyro is “slaved to,” or continuously corrected to bring its direction readings into agreement with a remotely located magnetic direction sensing device (usually a flux valve or flux gate compass).

Pilot's Handbook of Aeronautical Knowledge, p. G-27

Often used to measure the length of an object. It provides greater accuracy than a ruler.

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

The difference between the geometric and effective pitch of a propeller.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

A smooth, continuous ring of brass or copper mounted on the rotor shaft of an electrical generator or alternator. Brushes riding on the smooth surface of the slip ring carry current into and out of the rotor coil.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

A shop tool used to form large radius curves on sheet metal.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

A paint mark extending across the edge of an aircraft wheel onto a tube-type tire. When this mark is broken, it indicates the tire has slipped on the wheel, and there is a good reason to believe the tube has been damaged.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

An uncoordinated turn in which the aircraft is banked too much for the rate of turn, so the horizontal lift component is greater than the centrifugal force, pulling the aircraft toward the inside of the turn.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

For the purpose of rib stitch spacing, the slipstream area is considered to be the diameter of the propeller plus one wing rib on each side.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

A fixed, nozzle-like opening near the leading edge of an airplane wing ahead of the aileron. A slot acts as a duct to force high-energy air down on the upper surface of the wing when the airplane is flying at a high angle of attack. The slot, which is located ahead of the aileron, causes the inboard portion of the wing to stall first, allowing the aileron to remain effective throughout the stall.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

An electrical fuse that allows a large amount of current to flow for a short length of time but melts to open the circuit if more than its rated current flows for a longer period.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

A heavy contaminant that forms in an aircraft engine lubricating oil because of oxidation and chemical decomposition of the oil.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

Spool-shaped sheet metal plugs installed in the hollow throws of some engine crankshafts.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

The unit of mass equal to that which experiences an acceleration of one foot per second, per second when a force of one pound acts on it. It is equal to 32.174 pounds, or 14.5939 kilograms, of mass. Also called a G-pound.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

An airplane of 12,500 pounds or less maximum certificated takeoff weight.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

A device that warns the flight crew of the presence of smoke in cargo and/or baggage compartments. Some smoke detectors are of the visual type, others are photoelectric or ionization devices.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

A device in a hydraulic or pneumatic component that absorbs shock and/or vibration. A snubber is installed in the line to a hydraulic pressure gauge to prevent the pointer fluctuating.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

Spectrometric oil analysis program. An oil analysis program in which a sample of oil is burned in an electric arc and an analysis is made of the wavelength composition of the resulting light. Each chemical element in the oil, when burned, produces light containing a unique band of frequencies. A computer analyzes the amount of each band of frequencies and prints out the number of parts of the element per million parts of the entire sample. SOAP can predict engine problems by warning the engine operator of an uncharacteristic increase of any elements in the oil.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

Wood from a tree that bears cones and has needles rather than leaves.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

A method of thermally joining metal parts with a molten nonferrous alloy that melts at a temperature below 800 °F. The molten alloy is pulled up between close-fitting parts by capillary action. When the alloy cools and hardens, it forms a strong, leak-proof connection.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

A loop of wire, often wrapped around a metal core, which produces a magnetic field when an electrical current is passed through it.

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

The solidity of a helicopter rotor system is the ratio of the total blade area to the disc area.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

The ratio of the total rotor blade area to total rotor disk area.

Helicopter Flying Handbook, p. G-5

A type of heat treatment in which the metal is heated in a furnace until it has a uniform temperature throughout. It is then removed and quenched in cold water. When the metal is hot, the alloying elements enter into a solid solution with the base metal to become part of its basic structure. When the metal is quenched, these elements are locked into place.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

The misperception of being in a nose-up or nose-down attitude, caused by a rapid acceleration or deceleration while in flight situations that lack visual reference.

Pilot's Handbook of Aeronautical Knowledge, p. G-27

A sonic venturi in a line between a turbine engine or turbocharger and a pressurization system. When the air flowing through the sonic venturi reaches the speed of sound, a shock wave forms across the throat of the sonic venturi and limits the flow. A sonic venturi is also called a flow limiter.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

The airframe component that replaces the turbine engine tail pipe. It reduces the distance the sounds made by the exhaust gases propagate by converting low-frequency vibrations.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

The dimension of a rotor blade or airfoil from root to tip.

Helicopter Flying Handbook, p. G-5

The state of confusion due to misleading information being sent to the brain from various sensory organs, resulting in a lack of awareness of the aircraft position in relation to a specific reference point.

Pilot's Handbook of Aeronautical Knowledge, p. G-28

A flight permit issued to an aircraft that does not meet airworthiness requirements but is capable of safe flight. A special flight permit can be issued to move an aircraft for the purposes of maintenance or repair, buyer delivery, manufacturer flight tests, evacuation from danger, or customer demonstration. Also referred to as a ferry permit.

Pilot's Handbook of Aeronautical Knowledge, p. G-28

The amount of fuel in pounds per hour consumed or required by an engine per brake horsepower or per pound of thrust.

Pilot's Handbook of Aeronautical Knowledge, p. G-28

Airspace in which flight activities are subject to restrictions that can create limitations on the mixed use of airspace. Consists of prohibited, restricted, warning, military operations, and alert areas.

Pilot's Handbook of Aeronautical Knowledge, p. G-28

The ratio of the mass of a solid or liquid to the mass of an equal volume of water.

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

The quantity of heat necessary to increase the temperature of a unit of the mass of a substance 1 °C. The specific heat of a substance is the ratio of its specific heat capacity to the specific heat capacity of water.

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

The ratio of the weight of an aircraft engine to the brake horsepower it develops.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

The distance traveled in a given time.

Pilot's Handbook of Aeronautical Knowledge, p. G-28

A secondary control of an airplane that produces drag without causing a change in the pitch attitude of the airplane. Speed brakes allow an airplane to make a steep descent without building up excessive forward airspeed.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

The speed of sound at sea level under standard temperature and pressure conditions is 1,108 feet per second or 658 knots.

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

A knot that runs through the depth of a beam perpendicular to the annual rings. Spike knots appear most frequently in quartersawed wood.

Aviation Maintenance Technician Handbook — Airframe, p. G-32

A flight maneuver in which an airplane descends in a corkscrew fashion. One wing is stalled and the other is producing lift.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

A condition that exists when the static directional stability of the airplane is very strong as compared to the effect of its dihedral in maintaining lateral equilibrium.

Pilot's Handbook of Aeronautical Knowledge, p. G-28

The slipstream of a propeller-driven airplane rotates around the airplane. This slipstream strikes the left side of the vertical fin, causing the aircraft to yaw slightly. Rudder offset is sometimes used by aircraft designers to counteract this tendency.

Pilot's Handbook of Aeronautical Knowledge, p. G-28

A leveling instrument placed on or against a specified place on the aircraft. Spirit levels have vials that are full of liquid, except for a small air bubble. When the air bubble is centered between the two black lines, a level condition is indicated.

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

A type of patch made in an aircraft plywood structure in which the edges of the patch are tapered for approximately five times the thickness of the plywood. A splayed patch is not recommended for use on plywood less than 1⁄10 inch thick.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

Parallel slots cut in the periphery of a shaft, parallel to its length. Matching slots, cut into the hub or wheel that fits on the shaft, lock the shaft into the device to transmit torque.

Aviation Maintenance Technician Handbook — Powerplant, p. G-25

A longitudinal crack in a piece of wood caused by externally induced stress.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

A type of electrical bus that allows all of the voltage-sensitive avionic equipment to be isolated from the rest of the aircraft electrical system when the engine is being started or when the ground-power unit is connected.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

A term used to describe the position of the two needles on the engine/rotor tachometer when the two needles are not superimposed.

Helicopter Flying Handbook, p. G-5

An electrical switch whose operating rocker is split so one half of the switch can be opened without affecting the other half. Split-rocker switches are used as aircraft master switches. The battery can be turned on without turning on the alternator, but the alternator cannot be turned on without also turning on the battery. The alternator can be turned off without turning off the battery, but the battery cannot be turned off without also turning off the alternator.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

Flight controls that are raised up from the upper surface of a wing to destroy, or spoil, lift. Flight spoilers are used in conjunction with the ailerons to decrease lift and increase drag on the descending wing. Ground spoilers are used to produce a great amount of drag to slow the airplane on its landing roll.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

Hydraulic brakes whose pedal has a spongy feel because of air trapped in the fluid.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

Self-ignition of a material caused by heat produced in the material as it combines with oxygen from the air.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

A freewheeling, nonreversible clutch that allows torque to be applied to a driven unit in one direction only.

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

A condition in the rigging of an aircraft engine control in which the stop at the engine is reached before the stop in the flight deck. The flight deck control moves slightly after the stop in the engine is reached, and when it is released, it springs back slightly.

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

The portion of an annual ring in a piece of wood formed principally during the first part of the growing season, the spring of the year. Springwood is softer, more porous, and lighter than the summerwood.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

A form of constant-displacement fluid pump that uses two meshing spur-gears mounted in a close fitting housing. Fluid is taken into the housing where it fills the space between the teeth of the gears and is carried around the housing as the gears rotate. On the discharge side of the pump, the teeth of the two gears mesh, and the fluid is forced out of the pump.

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

A four-sided plane figure whose sides are all the same length, whose opposite sides are parallel, and whose angles are all right angles.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

A non-negative number that must be multiplied by itself to equal a given number.

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

An electrical switch actuated by the landing gear scissors on the oleo strut. When no weight is on the landing gear, the oleo piston is extended and the switch is in one position, but when weight is on the gear, the oleo strut compresses and the switch changes its position. Squat switches are used in antiskid brake systems, landing gear safety circuits, and cabin pressurization systems.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

See profile tip.

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

Another name for oil-damped bearings. See oil-damped bearings.

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

An explosive device in the discharge valve of a high-rate-discharge container of fire-extinguishing agent. The squib drives a cutter into the seal in the container to discharge the agent.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

Structural Repair Manual.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

See secondary surveillance radar.

Pilot's Handbook of Aeronautical Knowledge, p. G-28

See standard service volume.

Pilot's Handbook of Aeronautical Knowledge, p. G-28

Elmo’s Fire. A corona discharge which lights up the aircraft surface areas where maximum static discharge occurs.

Pilot's Handbook of Aeronautical Knowledge, p. G-26

A flight control on the empennage of an airplane that acts as both a stabilizer and an elevator. The entire horizontal tail surface pivots and is moved as a unit.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

The characteristic of an aircraft that causes it to return to its original flight condition after it has been disturbed.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

Small wing-like horizontal surfaces mounted on the aft fuselage to improve longitudinal stability of airplanes that have an exceptionally wide center of gravity range.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

The distance between landing points in airline operation.

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

One disc of rotor blades and the following set of stator vanes in an axial-flow compressor.

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

Ignition timing that causes the spark plug nearest the exhaust valve to fire a few degrees of crankshaft rotation before the spark plug nearest the intake valve.

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

A type of hypoxia that results when the oxygen-rich blood in the lungs is not moving to the tissues that need it.

Pilot's Handbook of Aeronautical Knowledge, p. G-28

The point on the leading edge of a wing at which the airflow separates, with some flowing over the top of the wing and the rest below the wing.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

A flight condition in which an angle of attack is reached at which the air ceases to flow smoothly over the upper surface of an airfoil. The air becomes turbulent and lift is lost.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

A fixed device employed on the leading edge of fixed-wing aircraft to initiate flow separation at chosen locations on the wing during high-angle of attack flight, so as to improve the controllability of the aircraft when it enters stall.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

Conditions that have been decided upon by the ICAO for comparing all aircraft and engine performance. The most basic standard day conditions are: temperature, 15 ºC or 59 ºF; altitude, mean sea level; pressure, 29.92 inches of mercury.

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

The weight of the airframe, engines, all permanently installed equipment, and unusable fuel. Depending upon the part of the Federal regulations under which the aircraft was certificated, either the undrainable oil or full reservoir of oil is included.

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

A holding pattern in which all turns are made to the right. Standard instrument departure procedures (SIDS). Published procedures to expedite clearance delivery and to facilitate transition between takeoff and en route operations.

Pilot's Handbook of Aeronautical Knowledge, p. G-28

A World War I training airplane powered by a Curtiss OX-5 engine.

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

A turn in which an aircraft changes its direction at a rate of 3° per second (360° in 2 minutes) for low- or medium-speed aircraft. For high-speed aircraft, the standard rate turn is 1½° per second (360° in 4 minutes).

Pilot's Handbook of Aeronautical Knowledge, p. G-28

Defines the limits of the volume of airspace which the VOR serves.

Pilot's Handbook of Aeronautical Knowledge, p. G-28

A preplanned IFR ATC arrival procedure published for pilot use in graphic and/or textual form.

Pilot's Handbook of Aeronautical Knowledge, p. G-28

Values used in weight and balance calculations if specific weight for an item is unknown. The following are examples: • Aviation gasoline 6 pounds per gallon • Crew and passengers 170 pounds per person • Lubricating oil 7.5 pounds per gallon • Turbine fuel 6.7 pounds per gallon • Water 8.35 pounds per gallon

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

A pipe sticking up in a tank or reservoir that allows part of the tank to be used as a reserve, or standby, source of fluid.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

See standard terminal arrival route.

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

A single-component starter and generator used on many of the smaller gas-turbine engines. It is used as a starter, and when the engine is running, its circuitry is shifted so that it acts as a generator.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

Still, not moving.

Aviation Maintenance Technician Handbook — Airframe, p. G-33

Pressure of the ambient air surrounding the aircraft. Static pressure does not take into consideration any air movement.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

Devices connected to the trailing edges of control surfaces to discharge static electricity harmlessly into the air. They discharge the static charges before they can build up high enough to cause radio receiver interference.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

The load imposed on an aircraft structure due to the weight of the aircraft and its contents.

Aircraft Weight and Balance Handbook, p. G-5

The aerodynamic pitching moments required to return the aircraft to the equilibrium angle of attack.

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

The pressure of an unmoving fluid.

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

The number of revolutions per minute an aircraft engine can produce when the aircraft is not moving.

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

The initial response that an airplane displays after its equilibrium is disrupted.

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

A device used to limit the blade flap, or rotor flap, at low rpm or when the rotor is stopped.

Helicopter Flying Handbook, p. G-5

(GAMA) A location along the airplane fuselage usually given in terms of distance from the reference datum.

Aircraft Weight and Balance Handbook, p. G-5

A front that is moving at a speed of less than 5 knots.

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

The type of flight experienced when a helicopter is in straight-and-level, unaccelerated flight, and all forces are in balance.

Helicopter Flying Handbook, p. G-5

A method of liquid cooling in which the coolant, normally water, is allowed to absorb enough heat that it boils. The steam gives up its heat when it condenses back into a liquid.

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

In instrument flight, any turn greater than standard rate; in visual flight, anything greater than a 45° bank.

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

A nonferrous alloy of cobalt, chromium, and tungsten. Stellite is hard, water resistant, and corrosion resistant, and it does not soften until its temperature is extremely high. Stellite is welded to the faces of many reciprocating engine exhaust valves that operate at very high temperatures.

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

The point after which additional descent is permitted within a segment of an IAP.

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

A precision electric motor whose output shaft position is changed in steps by pulses from the control device. Stepping motors can make high-torque changes in small angular increments to their output shaft.

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

A petroleum product, similar to naphtha, used as a solvent and a cleaning fluid.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

The air/fuel mixture ratio that, when burned, leaves no uncombined oxygen nor any free carbon. It releases the maximum amount of heat, and therefore produces the highest exhaust gas temperature. A stoichiometric mixture of gasoline and air contains 15 pounds of air for 1 pound of gasoline.

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

Short takeoff and landing.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

A method of stopping the growth of a crack in a piece of metal or transparent plastic by drilling a small hole at the end of the crack. The stresses are spread out all around the circumference of the hole rather than concentrated at the end of the crack.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

DC-electric arc welding in which the electrode is negative with respect to the work.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

A combustor in a gas turbine engine through which the air from the compressor to the turbine flows in an essentially straight line.

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

A deformity or change in an object due to stress.

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

A device that converts a physical phenomenon into an electrical signal. Strain sensors in a wheel axle sense the magnitude of the force the axle deflects and create an electrical signal that is proportional to the force that caused the deflection

Aircraft Weight and Balance Handbook, p. G-5

An INS in which the accelerometers and gyros are permanently “strapped down” or aligned with the three axes of the aircraft.

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

A layer of the atmosphere above the tropopause extending to a height of approximately 160,000 feet.

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

The upper part of the Earth’s atmosphere. The stratosphere extends upward from the tropopause, which is approximately 36,000 feet above the surface of the Earth, to approximately 85,000 feet. The temperature of the air in the stratosphere remains constant at -56.5 ºC (-69.7 ºF).

Aviation Maintenance Technician Handbook — Powerplant, p. G-26

The internal resistance of an object to external forces attempting to strain or deform that object. Measured in pounds per square foot or pounds per square inch (psi).

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

Occurs as the result of the combined effect of sustained tensile stresses and a corrosive environment.

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

The personal analysis of the kinds of stress experienced while flying, the application of appropriate stress assessment tools, and other coping mechanisms.

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

A location where the cross-sectional area of the part changes abruptly. Stresses concentrate at such a location and failure is likely. A scratch, gouge, or tool mark in the surface of a highly stressed part can change the area enough to concentrate the stresses and become a stress riser.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

A type of aircraft structure in which all or most of the stresses are carried in the outside skin. A stressed skin structure has a minimum of internal structure.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

A part of an aircraft structure used to give the fuselage its shape and, in some types of structure, to provide a small part of fuselage strength. Formers give the fuselage its cross-sectional shape and stringers fill in the shape between the formers.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

A tachometer used to measure the speed of any rotating device without physical contact. A highly accurate variable-frequency oscillator triggers a high-intensity strobe light.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

The distance the piston moves inside the cylinder.

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

The accumulation of ice on the exterior of the aircraft.

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

A location in the aircraft, such as a bulkhead, that is identifi[e]d by a number designating its distance in inches or percent MAC from the datum. The datum is, therefore, identified as station zero. The stations and arms are identical. An item located at station +50 would have an arm of 50 inches.

Aircraft Weight and Balance Handbook, p. G-5

A process in which a solid material changes directly into a vapor without passing through the liquid stage.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

Flight at an airspeed in which all air flowing over the aircraft is moving at a speed below the speed of sound.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

The process where the value of one number is taken from the value of another.

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

A relief valve in an instrument vacuum system required to maintain the correct low pressure inside the instrument case for the proper operation of the gyros.

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

The resulting answer in the addition process.

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

The less porous, usually harder portion of an annual ring that forms in the latter part of the growing season, the summer of the year.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

A low point in an aircraft fuel tank in which water and other contaminants can collect and be held until they can be drained out.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

A sensitive radio receiver circuit in which a local oscillator produces a frequency that is a specific difference from the received signal frequency. The desired signal and the output from the oscillator are mixed, and they produce a single, constant intermediate frequency. This IF is amplified, demodulated, and detected to produce the audio frequency that is used to drive the speaker.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

A reciprocating engine that uses a mechanically driven compressor to increase the air pressure before it enters the engine cylinders.

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

An air compressor used to increase the pressure of the air being taken into the cylinders of a reciprocating engine.

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

Water in its liquid form at a temperature well below its natural freezing temperature. When supercooled water is disturbed, it immediately freezes.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

Water droplets that have been cooled below the freezing point, but are still in a liquid state.

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

Heat energy that is added to a refrigerant after it changes from a liquid to a vapor.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

Flight at an airspeed in which all air flowing over the aircraft is moving at a speed greater than the speed of sound.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

An approval issued by the FAA for a modification to a type certificated airframe, engine, or component. More than one STC can be issued for the same basic alteration, but each holder must prove to the FAA that the alteration meets all the requirements of the original type certificate.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

A document issued by the FAA approving a product (aircraft, engine, or propeller) modification.

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

A report that depicts an analysis of the current surface weather. Shows the areas of high and low pressure, fronts, temperatures, dewpoints, wind directions and speeds, local weather, and visual obstructions.

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

Caused by either direct chemical or electrochemical attack, it appears as a general roughening, etching, or pitting of the surface of a metal, frequently accompanied by a powdery deposit of corrosion products.

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

The condition of the surface of a reciprocating engine cylinder wall that has been honed to make it hold lubricating oil. Surface roughness is measured in micro-inches rms.

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

Strips of aircraft fabric that are doped over all seams and places where the fabric is stitched to the aircraft structure. Surface tape is also doped over the wing leading edges where abrasive wear occurs. The edges of surface tape are pink, or notched, to keep them from raveling before the dope is applied.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

A surface active agent, or partially soluble contaminant, which is a by-product of fuel processing or of fuel additives. Surfactants adhere to other contaminants and cause them to drop out of the fuel and settle to the bottom of the fuel tank as sludge.

Aviation Maintenance Technician Handbook — Airframe, p. G-34

A condition of unstable airflow, through the compressor of a gas turbine engine, in which the compressor blades have an excessive angle of attack. Surge usually affects an entire stage of compression.

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

An instrument consisting of a telescope mounted on a flat, graduated, circular plate on a tripod. The plate can be adjusted so it is level, and its graduations oriented to magnetic north. When an object is viewed through the telescope, its azimuth and elevation may be determined.

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

These fittings create a permanent connection that is virtually maintenance free. Swaged fittings are used to join hydraulic lines in areas where routine disconnections are not required and are often used with titanium and corrosion resistant steel tubing.

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

The component in a helicopter control system that consists basically of two bearing races with ball bearings between them. The lower, or nonrotating, race is tilted by the cyclic control, and the upper, or rotating, race has arms which connect to the control horns on the rotor blades. Movement of the cyclic pitch control is transmitted to the rotor blades through the swashplate. Movement of the collective pitch control raises or lowers the entire swashplate assembly to change the pitch of all the blades at the same time.

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

An airfoil that has the same shape on both sides of its chord line, or center line.

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

A check of an airframe to determine that the wings and tail are symmetrical about the longitudinal axis. System-pressure regulator (hydraulic system component). A type of hydraulic system-pressure control valve. When the system pressure is low, as it is when some unit is actuated, the output of the constant-delivery pump is directed into the system. When the actuation is completed and the pressure builds up to a specified kick-out pressure, the pressure regulator shifts. A check valve seals the system off and the pressure is maintained by the accumulator. The pump is unloaded and its output is directed back into the reservoir with very little opposition. The pump output pressure drops, but the volume of flow remains the same. When the system pressure drops to the specified kick-in pressure, the regulator again shifts and directs fluid into the system. Spool-type and balanced-pressure-type system pressure regulators are completely automatic in their operation and require no attention on the part of the flight crew.

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

A device used to transmit indications of angular movement or position from one location to another.

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

A remote instrument indicating system. A synchro transmitter is actuated by the device whose movement is to be measured, and it is connected electrically with wires to a synchro indicator whose pointer follows the movement of the shaft of the transmitter.

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

Oil made by chemical synthesis of a mineral, animal, or vegetable base. Synthetic oils have appropriate additives that give them such characteristics as low volatility, low pour point, high viscosity index, good lubricating qualities, low coke and lacquer formation, and low foaming.

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