Lecture Notes: Airplane Engines and Propulsion Systems

Introduction to Airplane Engines

• Airplane engines are referred to as power plants.
• Engines power the airplane and generate electricity, vacuum, and heat.
• Two main types of aviation engines:
  • Reciprocating Engines
  • Turbine Engines
• Airlines use turbine engines; general aviation uses reciprocating engines.

Reciprocating Engines

• Composed of cylinders where fuel and air mixture is ignited.
• Pistons move in and out, rotating the crankshaft linked to the propeller.
• Four-stroke cycle:
  • Intake Stroke: Piston moves away, intake valve opens, draws in fuel-air mixture.
  • Compression Stroke: Piston moves back, compresses mixture.
  • Power Stroke: Spark plugs ignite mixture, pushes piston, rotates crankshaft.
  • Exhaust Stroke: Piston expels combusted gases, exhaust valve opens.

Components of Reciprocating Engines

• Camshaft: Controls valve timing, synchronized with crankshaft.
• Induction System: Throttle and mixture controls in cockpit.
  • Throttle: Controls amount of fuel-air mixture into cylinders.
  • Mixture: Controls fuel-to-air ratio.

Induction Systems

• Air passes through air filter, fuel stored in wings.
• Carburetor System: Mixes fuel with air; air velocity increases in venturi, drawing fuel out.
• Fuel Injection System:
  • Consists of fuel pumps, control unit, manifold valve, discharge nozzles.
  • Fuel and air mix immediately before entering combustion chamber.

Ignition System

• Components: Magnetos, spark plugs, wires, ignition switch.
• Magnetos: Generate sparks independently from electrical system.
• Ignition Switch: Controls magnetos, settings include off, right, left, both, start.

Abnormal Engine Conditions

• Detonation: Uncontrolled explosion causing high temperature and pressure.
  • Solutions: Reduce power, increase mixture.
• Pre-ignition: Fuel-air mixture ignites prematurely.
  • Causes: Hot spots on cylinder walls.

Engine Cooling

• Oil Cooling: Oil lubricates and cools engine.
• Air Cooling: Air flows over engine, restricted in high power/low speed scenarios.

Exhaust System

• Releases exhaust gases quietly.
• Provides cabin heat.

Propulsion and Thrust

• Propeller Function: Converts rotational energy into thrust.
  • Propeller blade is twisted to create equal thrust.

Types of Propellers

• Fixed-Pitch Propeller:
  • Not adjustable; controlled by engine RPM.
  • Found in Cessna 172.
• Constant-Speed Propeller:
  • Blade angle adjustable for different conditions.
  • Features a separate propeller control for RPM adjustment.
  • Found in Diamond DA-42.

These notes provide a concise summary of the key points discussed regarding airplane engines and their operation during the lecture.