Engines- Electrical Systems Flashcards
Describe AC/DC electrical systems
what are their relative advantages
- AC: alternates equally in a negative and positive direction
- requires less current loads = light wiring (less weight on aircraft)
- DC: Straight line voltage
- heavier components
- increased maintenance
Sources of AC Electrical Power
Sources
- AC:
- AC Generator (alternator)
- transforms mechangical energy into electrical energy
- main source of electrical energy
- Inverter
- transforms DC current into AC
- AC Generator (alternator)
Sources of DC electrical Power
- DC Generator
- Transforms mechangical energy into electrical energy
- Transformer Rectifier
- transforms AC Voltage into DC
- carries high current loads
- Stable DC output
- Reliable
- Battery
- Emergency power should generator fail
- Engine Starting
What are the electrical distribution networks
A Bus is the distribution network
What are the 3 different types of controls needed for electrical equipment? Where are they located?
Three types of controls:
- Switches- cockpit
- manual control allows the crew to control the particular system
- Circuit breakers:
- located throughout the aircraft including the cockpit
- manual or automatic
- Fuses:
- automatic circuit protection
What is the Master Caution Panel?
What does the CHIP warning light indicate
The master caution panel provides the pilot with a centralized warning center for systems pertinent to flight safety.
the CHIP warning light signals that there is excess metel on the engine
Volitility
ability of a fluid to evaporate
Flashpoint
The lowest temperature at which a sufficient amount of vapor is given off by a liquid to form an ignitable mixture with it
What is the relationship between temperature, volatility, and flashpoint?
A highly volatile fule will vaporize at a lower temperature than a fuel with low volatility
High volatility fuel has a low flash point, low volatility fuel has a high flash point
inverse relationship
What are the three types of thrust ratings?
Thrust ratings
- Normal:
- thrust produced at the maximum continuous ITT
- NO TIME LIMITATIONS
- Military
- MAX ITT
- 30 minute time limit
- Combat:
- thrust produced with the afterburner- not based on turbine temperature
- NO TIME LIMITATIONS
Fuel System: Afterburner fuel control unit
Afterburner fuel control unit
meters fuel to the afterburner fuel nozzles (Spraybars)
Explain the operation of an afterburner fuel control unit
During afterburner operations, the fuel transfer valve opens and allows fuel to flow to the afterburner fuel control unit. This unit meters fuel to the afterburner spray bars
JP-4 Fuel
volatility?
Flash point?
other notable characteristics
JP-4
Highly volatile
Flash point: -35F
other notable characteristics: Easier starting, slower acceleration, lower operating temps, shorter range
JP-5 Fuel
volatility?
Flash point?
other notable characteristics
JP-4 Fuel
volatility: thermally stable
Flash point :140F
other notable characteristics: Navy’s primary jet fuel, high heat content per gallon
JP-8 Fuel
volatility?
Flash point?
other notable characteristics
JP-8 Fuel
volatility: safe to store and thermally safe
Flash point: 100F
other notable characteristics: very expensive. Used by NATO and the air force
Civilian Aircraft Fuel
Flash point
two types
Avgas
- Flashpoint: -45F
- defined by their octane rating
- Avgas 100
- high lead
- dyed green
- Avgas 100LL
- lower lead
- dyed blue
- Avgas 100
Fuel System: Fuel Tank
Fuel Tank
Starting point for fuel
reservoir or holding cell for fuel
Fuel System: boost pump
Boost Pump
submerged in the fuel tank
prevents aeration of the fuel supply which may result from a rapid pressure change incurred during a climb
Fuel System: Pressure Monitor
Pressure Monitor
located at boos pump outlet with corresponding gauge in cockpit
Fuel System: Low pressure fuel filter
downstream of the boost pump to strain impurities of the fuel
includes a bypass
Fuel System: engine-driven fuel pump
Delivers fuel to the Fuel Control Unit (FCU)
HIGH PRESSURE PUMP provides fuel in excess for the engine and afterburner demands
like all pumps, it also has a filter
Fuel System: Fuel Control Unit
“brain”
provides the fuel manifold with metered fuel to meet engine requirements
- Monitors:
- Starting
- Acceleration
- Deceleration
- Stabilizied (steady state) operation
- Senses the:
- Compressor Inlet Temperature
- RPM
- Turbine Temperature (ITT)
- PCL inputs from the aviator

Fuel System: Fuel Flow Gauge
Functions:
- measures the rate of consumption (pounds per hour)
- indicates fuel useage to the crew
Fuel System: fuel-oil cooler
fuel-oil cooler
- heat exchanger:
- cools oil, warms fuel

