NIFE Engines 3-9-1 Accessory, Starter, Ignition Flashcards
Aircraft accessories drive categories
- Air-driven
- Mechanically-driven
Air-driven accessories
Uses bleed air from the compressor
- air conditioning
- cockpit pressurization
- engine anti-ice
Mechanically-driven accessories
geared drive taken directly from the main shaft connecting the turbine to the compressor - used for
tachometers,
hydraulic pumps,
generators,
alternators,
and other accessories that must be mounted near or connected directly to the engine
Define interstage bleed air
A type of bleed air available from engines with dual/twin/split compressors that is used to ensure compressor stability.
Purpose of the starting system
to accelerate the engine until the turbine is producing enough power to continue the engine acceleration itself (called SELF-ACCELERATING SPEED)
Describe gas turbine starting sequence
- Starter on
- Ignition is activated
- Fuel added
- Engine Lights up
- Self Accelerating Speed
- Ignition Off
- Starter cuts out
- Engine Attains idle RPM
Types of abnormal starts
- Hot start
- Hung start
- False start
- Wet start
Hot start
exceeding the maximum allowable temperature for the turbine section during start
Hung start
the temperature within the turbine section continues to rise, and the compressor RPM stabilizes BELOW normal
False start
When compressor RPM stabilizes below normal, and the turbine temp remains within limits
Wet start
the fuel-air mixture does not light off initially, but has the capability to eventually ignite (MOST DANGEROUS)
Describe a DC electric starter
Mechanically connected to the compressor and is mounted on either the engine accessory gearbox or the front frame of the engine. Starts the engine by using a battery, APU, or external electrical source
Describe an air turbine starter
A small, geared, air turbine motor that is attached to the engine and accelerates the compressor using air from a ground cart or an internal power unit
Describe a basic aircraft ignition system
A high energy capacitor-type ignition system is normally used for gas turbine engines. This provides both high voltage and an exceptionally hot spark, which gives an excellent chance of igniting the fuel-air mixture at reasonably high altitudes
Ignitor plugs
- Annular Gap: Protrudes into the combustion chamber
- Constrained Gap: Creates an electric arc that extends beyond the chamber liner
