Thu Apr10th

• Engine Control and Element Movement

  • Movement of various engine components is centralized around the main shaft.

  • Key components affected by the main shaft's movement include:

  • Low pressure fuel pump

  • Oil pump

  • Starter motor

  • Centrifuge

  • A gearbox piece will connect various components, allowing simultaneous operation.

• Fuel and Ignition System

  • Combustion Requirements: To initiate combustion, three elements are necessary: fuel, air, and ignition.

  • Fuel is injected into the combustion chamber via nozzles.

  • Ignition System:

  • Positioned externally to the engine case

  • Utilizes a high energy emitter unit for ignition purposes.

  • Electricity is supplied first by a DC power source (28 volts).

  • The DC power is then tempered, transformed into AC through a transformer, then rectified for delivery to a capacitor.

  • The capacitor stores energy until it reaches a threshold (e.g., 25,000 volts) to trigger a spark for ignition.

• Electrical System Overview

  • The system runs on a cycle:

  • DC supply >> Transform into AC >> Rectify signal >> Store in the capacitor.

  • Upon reaching the stored voltage threshold, a spark is generated, initiating combustion.

• Modes of Ignition

  • Different operating modes are utilized based on engine conditions:

  • Off: Ignition is disabled.

  • Continuous: Provides continuous sparks to prevent engine stalls.

  • Automatic: Activates when conditions suggest engine stability might fail, such as during turbulence or icing.

• Starting the Engine

  • A starter motor connected to the gearbox initiates engine movement.

  • The cool-down process is managed by wind milling, where the fan is moved by airflow even when the engine is off.

  • A mechanism must ensure the starter motor disengages to prevent damage once the engine starts self-sustaining.

• Pneumatic Systems

  • Air bleed systems activate to start engines, using external air from APU or cross-bleed from another engine when starting.

  • Starting Sequence:

  • Monitor compressor speed, then open fuel flow and ignition when reaching optimal conditions.

• Reverse Thrust Mechanisms

  • Two primary systems of thrust reversal:

  • Bucket Doors: Redirect airflow through deployed doors to slow down the aircraft.

    • Opens during landing to redirect air backward, increasing braking effectiveness.

  • Cold Stream Reverse: Utilizes bypass air before combustion, also redirects airflow to assist in braking.

  • Reverse thrust is more effective at high speeds for stopping but not included in landing distance calculations due to unreliability.

• Operational Safety Features

  • Automatic safety measures are installed to prevent reverse thrust deployment issues during flight or landing.

  • Systems must ensure proper door status before maximum reverse thrust application.

Overall, the engine and ignition system work in a complex interrelationship to ensure consistent, safe operation and efficient performance during flight, incorporating multiple safety and operational mechanisms.