Chapter 3: Induction and Exhaust Systems

Reciprocating Engine Induction Systems

Basic Induction System

• Components: Air scoop, air filter, carburetor or fuel injection system.
• Air Scoop: Collects inlet air; located on the engine cowling for maximum airflow.
• Air Filter: Prevents dirt; housed in carburetor heat box or other housing.
• Fuel Metering Device: Sends air/fuel mixture to cylinders via intake manifold with long, curved pipes.
• Throttle Plate: Controls airflow; affects manifold pressure measured in inches of mercury (Hg).

Types of Induction Systems

• Updraft Induction System: Two runners, balance tube, and intake pipes; ensures even fuel distribution.
• Downdraft Balanced System: Provides optimum airflow; better fuel/air ratios for smoother operation.

Induction System Components

• Figure 32: Basic carburetor induction system diagram.
• Carburetor Heat Valve: Prevents icing by admitting warm air during icing conditions.
• Air Filters: Types include paper, foam, etc.; require regular servicing.

Induction System Icing

• Causes: Clouds, fog, rain, snow, high humidity.
• Types: Impact ice, fuel evaporation ice, throttle ice.
• Prevention: Carburetor heat system raises air temperature to prevent ice formation.
• Effects: Can cause engine to lose power or quit.

Induction System Filtering

• Dust and Dirt: Cause engine wear, affect fuel metering, and can clog oil passages.
• Prevention: Use of alternate induction system air inlet with dust filter.
• Maintenance: Regular inspection and cleaning of filters essential.

Induction System Inspection and Maintenance

• Inspection: Check for cracks, leaks, and ensure mounting security.
• Maintenance: Clean and service components regularly; follow manufacturer instructions.

Supercharged Induction Systems

• Purpose: Compress fuel/air mixture to normalize air pressure at altitude.
• Types: Internally driven superchargers (compress after carburetor) and externally driven turbo superchargers (compress before carburetor).
• Components: Include pressure and temperature sensing devices.
• Operation: Affected by altitude and power settings; turbocharger systems use engine oil for control.

Turbo Superchargers

• Function: Use exhaust gases to power a turbine that compresses incoming air.
• Components: Compressor assembly, turbine wheel, and full floating shaft bearing assembly.
• Operation: Controlled by waste gate and waste gate actuator; manages exhaust gas flow to the turbine.

Turbocharger Controllers

• Components: Include density controller, differential pressure controller.
• Purpose: Maintain constant power output and regulate turbocharger operation.
• Challenges: Bootstrapping and overshoot.

Turbine Engine Inlet Systems

• Purpose: Provide distortion-free airflow to compressor.
• Design: Inlet ducts vary by engine type and aircraft design.
• Components: May include inlet guide vanes for airflow straightening.

Reciprocating Engine Exhaust Systems

• Function: Safely expel high-temperature gases.
• Types: Short stack open system and collector system.
• Collector System: Used in turbo supercharged engines; raises back pressure, but offset by turbocharging gains.

Maintenance and Inspection

• Inspection: Check for leaks, cracks, and proper alignment.
• Failures: Can lead to carbon monoxide poisoning, power loss, or fire.

Turbocharger and Exhaust System Troubleshooting

• Common Issues: Coke deposits, leaks, and exhaust flow restrictions.
• Maintenance: Regular Deco king and adherence to manufacturer instructions.

Advanced Systems: Thrust Reversers and Afterburners

• Thrust Reversers: Used to slow aircraft post-landing, using mechanical or aerodynamic blockage.
• Afterburners: Increase thrust significantly; use additional fuel burned in exhaust nozzle.

Summary

• Induction and exhaust systems are critical for efficient engine operation.
• Regular maintenance and inspection are essential to prevent failures and ensure performance.
• Technology advancements continue to improve system efficiency and reduce emissions.