Aircraft Turbine Engine Fundamentals and Maintenance

Comprehensive vocabulary flashcards covering the Brayton cycle, engine thrust, components, lubrication types, and operational malfunctions of aircraft turbine engines.

Brayton cycle

A thermodynamic cycle characterized by variable volume and constant pressure.

Thrust

The aerodynamic force produced by a propeller or turbojet engine as it forces a mass of air to the rear, behind the aircraft.

Net Thrust Formula

$F_n = M_s(V_2 - V_1) / G$, where $F_n$ is force, $M_s$ is mass, $V_2$ is outlet velocity, $V_1$ is inlet velocity, and $G$ is gravity.

Divergent duct

A duct shape where pressure increases, velocity decreases, and temperature increases.

Convergent duct

A duct shape where pressure decreases, velocity increases, and temperature decreases.

Bypass air

The mass of air that bypasses the core and is used for thrust, associated with N1.

Core air

Air entering directly into the interior parts of the engine used for combustion and utilized by the N2.

N1

Low-pressure compressor speed.

N2

High-pressure compressor speed, which is governed by the fuel control.

Ram recovery

The process of recovering the pressure of the free stream air as it enters the engine inlet.

Cascade effect

The process where stators diverge air to raise pressure and rotors converge air to accelerate it into the next stage.

Bleed air

High temperature, high pressure air taken from the compressor for various purposes.

Combustor types

Can, Annular, and Can-Annular.

Film air

Air (typically 25% - 35%) used to cool the surface of the combustor by creating a protective layer.

Fir Tree

A common type of turbine blade attachment named for its profile shape.

Blade Creep

The progressive deformation or stretching of turbine blades; an audible noise on engine shut down may indicate partial contact with the shroud.

Viscosity

The resistance of a fluid to flow, also described as the internal friction or stiffness of the fluid.

Flash point

The temperature to which a liquid must be raised for it to ignite, but not continue to burn, when a flame is passed above it.

Fire point

The temperature to which oil must be heated for vapors to ignite and burn continuously when a small flame is passed above it.

SOAP

Spectrometric Oil Analysis Program; used to predict engine problems by warning of an uncharacteristic increase of elements in the oil.

Dry sump system

A lubrication system that has a separate oil tank, generally located outside the engine proper.

Wet sump system

A lubrication system that scavenges oil to the accessory case and uses a splash method to lubricate accessory gearings.

Hot tank system

Turbine engine lubrication systems that incorporate oil coolers in the pressure side of the system downstream of the engine driven pump.

Magnetic chip detector

A component that collects ferrous metal to indicate potential engine problems to the pilot or maintenance personnel.

Rotable

A part that has been started, operated, and shut down and will be subsequently re-used.

On-Condition

A maintenance philosophy where parts are replaced based on their actual condition rather than fixed time intervals.

Hot start

An engine start attempt where the internal temperatures exceed the manufacturer's specified limits.

Hung start

A start where the engine lights up normally but fails to reach a speed that allows continued acceleration without help from the starter.

EGT

Exhaust Gas Temperature.

TIT

Turbine Inlet Temperature.

ITT

Interstage Turbine temperature.

TOT

Turbine Outlet Temperature.

Fault Isolation Manual

A manual used to isolate a faulty component quickly during maintenance.