DGCA CPL Technical General key terms

The main longitudinal structural member of a wing or tailplane; it carries the bending loads produced by lift and anchors the ribs and skin panels.

A chordwise member that gives the wing or tailplane its aerofoil shape and passes loads from the skin into the spar.

A slender longitudinal stiffener attached to the skin that helps the skin carry compression and shear loads without buckling.

A construction method where the skin shares flight and pressurization loads with a framework of frames, stringers, and bulkheads, giving high strength at low weight.

The outer covering of the airframe; in stressed-skin designs it carries part of the flight and pressurization loads as well as forming the aerodynamic surface.

A hinged control surface at the wing trailing edge that moves in opposite directions on each wing to roll the aircraft about its longitudinal axis.

A trailing-edge high-lift device that extends to increase wing camber and area, lowering stall speed and shortening takeoff and landing runs.

A system that uses pressurized fluid to transmit force and motion to actuators that operate landing gear, brakes, flaps, and some flight controls.

The piston engine operating sequence of intake, compression, power, and exhaust strokes, giving one power pulse per cylinder every two crankshaft revolutions.

The ratio of cylinder volume at bottom dead centre to the volume at top dead centre; it affects power output, efficiency, and detonation margin.

Explosive, uncontrolled burning of part of the fuel-air charge after spark ignition, producing heavy pressure spikes, noise, and possible engine damage.

A self-contained, engine-driven generator that produces the high-voltage pulses for spark plugs, so ignition does not depend on the aircraft battery.

A device that meters fuel into the engine intake air by venturi suction; it is susceptible to icing and needs mixture leaning as altitude increases.

A propeller whose blade angle is adjusted automatically by a governor so that engine RPM stays at the value selected by the pilot.

Turning the blades of a propeller to a very coarse angle, roughly parallel to the airflow, to cut drag after an engine failure.

A gas turbine that compresses air, burns fuel in a combustion chamber, and expands the hot gas through a turbine to drive a propeller or fan.

The combined pitot and static pressure sources that supply the airspeed indicator, altimeter, and vertical speed indicator with their operating pressures.

A pressure instrument that converts static pressure into indicated altitude above the reference set on its subscale or pressure-setting window.

An instrument that compares pitot impact pressure with static pressure to display the aircraft's speed through the air.

A spinning rotor mounted so that its axis resists change in direction; this rigidity, plus controlled precession, is the basis of many flight instruments.

A gyro horizon that shows the aircraft's pitch and roll relative to the real horizon, using a vertically spinning gyro for rigidity.

A directional gyro that displays heading and avoids the turning and acceleration errors of a magnetic compass, but needs periodic alignment with it.

A common conductive bar that collects power from generators or batteries and distributes it to the aircraft's electrical circuits and loads.

A rotating machine that produces alternating current, usually rectified to direct current, to supply electrical loads and charge the battery in flight.

A device that controls the field current of a generator or alternator so output voltage stays constant as engine speed and electrical load change.

A resettable protective switch that opens a circuit automatically when current exceeds its rating, protecting wiring from overheating and fire.

The electrical connection of metal structure and components so they share a common potential, preventing static sparks and reducing radio interference.

A metal made by combining two or more elements to obtain properties such as higher strength, hardness, or corrosion resistance than the pure metal.

A permanent fastener installed by deforming its shank to clamp sheets together; it is widely used to join aircraft skins and structure.

The twisting moment applied to a threaded fastener; it is set with a calibrated wrench to give correct clamping force without overstressing the bolt.

Corrosion caused by an electrochemical cell between dissimilar metals in contact in the presence of an electrolyte, which attacks the less noble metal.

Inspection methods such as dye penetrant, magnetic particle, eddy current, ultrasonic, and radiographic testing that reveal hidden defects without damaging the part.

Progressive damage from repeated cyclic stress, often beginning at a stress concentration such as a hole or sharp corner and growing into a crack.

A mandatory instruction from the aviation authority that requires inspection, modification, or limitation to correct an unsafe condition on a type-certificated aircraft.

A material of reinforcing fibres held in a resin matrix; it gives a high strength-to-weight ratio but can suffer hidden impact damage and delamination.

Separation between the layers of a composite laminate, often caused by impact or manufacturing defects and found by tap testing or ultrasonic inspection.