Aircraft Engines and Operations Quiz

Engine Performance

• Equivalent Shaft Horsepower (ESHP) is concerned with Turboprop and Turboshaft engines.
• Economical operation of an engine is referred to as THP (Thermal Horsepower).
• Thrust Specific Fuel Consumption (TSFC) is the ratio between fuel flow and thrust of an engine.

Engine Efficiency

• Engine efficiency is the ratio of output power to input energy.
• Component efficiency, thermal efficiency, and propulsive efficiency are different aspects of engine efficiency.
• 100% propulsive efficiency would occur if aircraft speed equals exhaust velocity.

Turbofan Engines

• High-bypass turbofan engines have the fan mounted to the turbine section.
• A bypass engine is also referred to as a subsonic engine.
• Thrust ratio is the comparison of thrust produced by the fan to the thrust produced by the engine core exhaust.

Centrifugal and Axial Flow Compressors

• Disadvantages of centrifugal flow compressors include high starting requirements, large frontal area, and high cost manufacturing.
• Axial flow compressors have the advantage of increased pressure rise with an increase in the number of stages.

Combustion Section

• The combustion section is located between the compressor diffuser and turbine section.
• The primary function of the combustion section is to burn the fuel-air mixture.
• About 2/3 of the energy produced by the combustion section is used to drive the gas generator compressor.

Reverse-Flow Combustors

• Reverse-flow combustors are designed to reduce the length of the engine.
• Annular combustors require less cooling air than can-annular combustors.

APU (Auxiliary Power Unit)

• The gas generator, combustion section, and compressor turbine comprise the gas generator in a turboprop engine.
• The power turbine is an additional turbine wheel that is placed in the exhaust stream from the gas generator.
• The gas generator section performs only one function, i.e., converting fuel energy into kinetic energy.

Thrust and Propulsion

• Thrust is derived from Newton's second law of motion.
• The converging and diverging duct mentioned in Bernoulli's principle is called a C-D duct.

Turbine Blades

• Creep is a gradual deformation of turbine blades due to centrifugal load and elevated operating temperature.
• Turbine blades are also known as buckets.
• Reaction turbine blades produce a turning force.

Cooling Systems

• Cooling air is directed over each side of the disk.
• Open-ended blades are used on low-speed turbines.
• Film cooling is a type of cooling where bleed air is directed in through hollow blades.

Turbine Cracks

• Stress cracks usually appear as minute hairline cracks on or across the leading or trailing edge at a right angle to the blade length.
• Typical causes of stress rupture cracks include excessive temperature and centrifugal loading.

Noise Reduction

• Jet engine noise is mainly the result of turbulence produced when hot, high-velocity jet exhaust mixes with cold, lower-velocity ambient air.
• A corrugated perimeter design type of silencer alters the shape of the exhaust stream as it leaves the engine.

Thrust Reversers

• Thrust reversers aid in braking and directional control during normal landing.
• They can even be deployed in air to hasten emergency descent.