1)Explain what is otto cycle means and explain each cycle shortly
Intake: Air-fuel mixture enters the combustion chamber as the piston moves down, creating a
vacuum.
Compression: The intake valve closes, and the piston compresses the air-fuel mixture. increases
pressure and temperature.
Power: A spark plug ignites the compressed mixture just before piston reaches top , leading to rapid
combustion and an increase in pressure at roughly constant volume.
Exhaust: The exhaust valve opens, and the piston moves up to expel the burned gases.
2)Compressor stall occurs in which situations?
Compressor stalls in gas turbine engines occur when smooth airflow through the compressor is
disrupted. Examples include:
Inlet Distortions
High Angle of Attack
Variable Inlet Guide Vanes Malfunction
Combustion Instabilities
Foreign Object Ingestion (FOD)
3)What is the difference between centrifugal and axial compressors?
Centrifugal Compressors:
Airflow: Radial direction, outward by centrifugal force.
Compression: Converts kinetic energy radially outward.
Size: Compact, suitable for lower pressure ratios.
Axial Compressors:
Airflow: Parallel to axis, accelerated by axial blades.
Compression: Incremental axial blade compression.
Size: Larger, efficient for high-pressure ratios.
4)what are lubrications primary and secondary purposes?
Primary Purpose of Lubrication:
Reduce Friction: Minimize metal-to-metal contact, reducing wear and improving efficiency. Also,
dissipate heat generated during operation.
Secondary Purposes of Lubrication:
Sealing: Prevent entry of contaminants.
Cooling: Aid in heat dissipation.
Cleaning: Remove debris and maintain cleanliness.
Reducing Wear and Tear: Create a protective film to minimize wear on moving parts.
5what are the differences between dry and wet sump lubrication systems?
Dry Sump Lubrication Sytsem
Oil Storage: External tank or reservoir.
Oil Pumping: Multiple scavenge pumps for efficient oil removal.
Application: Common in high-performance and aerobatic aircraft, ensuring oil supply during extreme
maneuvers.
Wet Sump Lubrication System
Oil Storage: Integrated oil pan within the engine.
Oil Pumping: Single pump for circulating oil within the engine.
Application: Standard in many general aviation aircraft, providing a simpler and cost-effective
lubrication solution.
6)what is the purpose of afterburner ?and how it works?
Purpose of Afterburner:
Boosts thrust for high-speed flight or combat situations.
How Afterburner Works:
Extra fuel injected into jet engine exhaust. Ignites in the afterburner section. Rapid expansion
increases exhaust velocity. Provides significant additional thrust. Enables higher speeds or rapid
acceleration.
7)what is the difference between turbochargers and superchargers? Also explain wastegate.
.
Turbocharger:
Driven by exhaust gases.
Mounted on the exhaust manifold.
May experience turbo lag due to reliance on exhaust gases.
Generally more fuel-efficient as it utilizes waste exhaust energy.
Effective at higher engine speeds and altitudes.
A wastegate is a valve in a turbocharged engine that controls the flow of exhaust gases to regulate
the speed of the turbocharger's turbine. It opens to prevent over-boosting, ensuring a consistent and
safe level of boost pressure and protecting the engine from potential damage.
Supercharger:
Driven mechanically by the engine through a belt or gear.
Installed on the engine's intake manifold.:
Provides immediate boost since it's mechanically driven.
Tends to consume more fuel as it's mechanically linked to the engine.:
Effective at lower RPMs, providing consistent boost across a wider range.
8)what is APU?
APU stands for Auxillary Power Unit and APU is a small, independent engine in an aircraft that
generates power for lights, avionics, and other systems when the main engines are not running.
Compared to other gas turbine engines APU is not meant to produce thrust.
9)what does it mean flat rated engine? Why its used?
A flat-rated engine in aircraft maintains a consistent level of thrust across different conditions like
varying temperatures and altitudes. This design ensures reliable and predictable performance,
simplifying flight planning and offering operational flexibility.
10) What are the FADEC’s advantages and disadvantages?
Advantages;
Optimized Performance
Fuel Efficiency
Reduced Pilot Workload
Increased Reliability
Engine Health Monitoring
Improved Starting and Operation
DisAdvantages;
Complexity and Cost
Maintenance Challenges
Vulnerability to Electronic Failures
Limited Pilot Control in Emergency
