ANAC GMP Theoretical Exam (Powerplant Group) key terms

The average pressure that would produce the measured brake power during one complete engine cycle, used to compare the work output of reciprocating engines regardless of displacement or speed.

The ratio of cylinder volume when the piston is at bottom dead center to the volume remaining at top dead center, influencing power, efficiency, and detonation margin.

An operating sequence in which intake, compression, power, and exhaust events each occupy a separate piston stroke, requiring two crankshaft revolutions per complete cycle.

The relationship between crankshaft position and the opening and closing of intake and exhaust valves, determining breathing, overlap, and power characteristics.

The measured gap between the valve stem and the rocker arm or tappet, allowing for thermal expansion and ensuring the valve seats fully when hot.

Uncontrolled, explosive combustion of the remaining fuel-air charge after normal ignition, producing a sharp pressure spike that can damage pistons and bearings.

The crankshaft position, expressed in degrees before top dead center, at which the magneto or ignition system fires the spark plug.

A self-contained, engine-driven generator that produces high-voltage pulses for spark plugs without relying on the aircraft's electrical system.

A spring-loaded device on a magneto that retards spark timing and accelerates the rotating magnet at low cranking speeds, ensuring a strong spark during starting.

A differential pressure check that measures air escaping from a pressurized cylinder to reveal leaking valves, worn piston rings, or a cracked cylinder head.

Ice formation in the carburetor venturi caused by fuel vaporization and pressure drop, which restricts airflow and can cause sudden power loss.

A pilot-controlled system that routes heated air into the carburetor to melt accumulated ice and prevent further formation, usually causing a temporary power reduction.

The cockpit control that adjusts fuel flow relative to airflow, allowing the pilot to maintain the correct fuel-air ratio as altitude and power change.

The temperature of exhaust gases leaving the cylinders, used to monitor combustion quality and to set the fuel mixture for best power or economy.

The temperature of gases entering the turbine section, a limiting parameter that protects turbine blades and nozzles from overheating and creep damage.

A rotating airfoil in the turbine section that extracts energy from hot combustion gases and drives the compressor and accessories through the shaft.

A disruption of smooth airflow through compressor blades, causing reverse flow, loud bangs, and loss of thrust, often triggered by excessive angle of attack or throttle changes.

A severe, cyclic breakdown of compressor airflow that produces violent pulsations and can damage the engine if not corrected promptly.

The ratio of air mass flowing through the fan bypass duct to air mass passing through the engine core, a primary measure of turbofan efficiency.

A mechanism that redirects fan or exhaust gas forward to produce rearward force, helping decelerate the aircraft after landing and reducing brake wear.

Full Authority Digital Engine Control, a computer system that manages fuel metering, ignition, and thrust parameters without mechanical backup for normal operation.

The angle between the propeller blade chord and the plane of rotation, determining the distance the blade would advance in one revolution.

A propeller whose blade angle is automatically adjusted to absorb engine power at a selected rotational speed, improving efficiency across flight conditions.

A control unit that senses propeller speed and regulates oil pressure to change blade angle, maintaining the selected RPM under varying loads.

A measure of an oil's resistance to flow, determining how well it lubricates and circulates at cold start and how it maintains film strength when hot.

The practice of mixing a small quantity of fuel into the engine oil before cold-weather starting to lower viscosity and improve circulation.

An instrument that displays the pressure of oil delivered to the engine bearings, indicating lubrication system health and warning of blockage or pump failure.

The process of warming an engine before starting in cold conditions to ensure oil flows freely and to prevent damage from inadequate lubrication.

A visual examination of internal engine components through small access ports using a fiber-optic or digital instrument, avoiding engine disassembly.

A mandatory regulatory notice requiring inspection, repair, or modification of an engine or aircraft to correct an unsafe condition.

Technical guidance issued by a manufacturer recommending inspection or modification, which may become mandatory when referenced by an airworthiness directive.

A certification statement confirming that maintenance has been completed and the engine or aircraft is approved for return to service.

The study of how human capabilities and limitations affect maintenance performance, including fatigue, complacency, and communication errors.

A set of twelve common human error precursors in aviation maintenance, such as fatigue, pressure, distraction, and lack of resources.

The accurate perception of current conditions and likely future states in the work environment, supporting sound decisions and hazard avoidance.

Any loose material that can enter an engine intake or damage components, requiring inspection and strict tool and hardware control.

A ground operational check in which the engine is run through specified power settings to verify performance, response, and system indications.

The usable power delivered at the engine output shaft, measured by a dynamometer or derived from torque and rotational speed.