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.

Test your knowledge on aircraft engines and operations with questions about equivalent shaft horsepower, economical operation terms, and thrust specific fuel consumption. See how well you understand different engine types and their efficiency.