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Airplane Systems

Objective​

To understand the basics electrical, environmental, and deicing systems of a trainer aircraft.

Motivation​

It is important to have an intuitive understanding of how the electrical system of airplane works to troubleshoot issues, and to understand common failure modes of the flight instruments.

Format​

Timing​

45 minutes

Elements​

  • Hydraulic systems
    • Brakes
    • Hydraulic lines connect brake pedals to brake calipers
  • Landing gear
    • Tricycle landing gear common on trainers
    • Nosewheels can be steerable or free-catering
    • Retractable landing gear
      • Electronic or hydraulically actuated
  • Electrical system
    • Basic circuit: Electrical potential (pressure), current (volume)
    • Series vs parallel circuits
    • Cessna usually have 28V electrical systems
    • Batteries: Capacity measured in amp-hours (17 amp-hours means 17 amps for 1 hour, or visa-versa)
    • 2 12V batteries to make a 24V system
    • Alternator
      • A generator that produces AC, a conversion is then done to DC using a rectifier
      • Has more consistent current output at low RPMs
      • Voltage must be higher than the battery to charge it
    • Contactors/Relays/Solenoids
      • Operate in different way, but are essentially a "remote switch"
      • We don't want all of the current to have to pass through the physical switch
      • Examples: Battery contactor, starter contactor
    • Master switch
      • Left half for battery master
      • Right half for alternator master
    • Bus bars: efficient way of connecting may components to power
    • Fuses and circuit breakers: Over current protection
      • Fuses are consumable
      • Circuit breakers can be popped back in
    • Electrical instrumentation
      • Ammeter: Shows whether the alternator is producing sufficient power for the given load
        • A discharge on the ammeter indicates a draw from the battery
      • Low voltage warning light
      • Load meter
        • Shows a percentage of the load placed on the alternator/generator
  • Environmental system
    • Fresh air vents
    • Heater, potential source of CO
  • Deice and anti-ice system
    • Airplane is prohibited from flight into known icing (FIKI)
    • Pitot heat
    • Windscreen defrost can also be used
    • Some airplanes have pneumatic boots used to break off ice
    • Cirrus aircraft use a "weeping wing"
      • Forces TKS fluid (a ethylene glycol based liquid) out of a porous membrane on the leading edge

References​