1. Battery
    • 24V, 40 Ampere
    • Provides Ess Bus backup power
    • May be NiCad or lead acid
  2. AC Generator (general)
    • (above 92% NR) provides three phase 115VAC (400Hz) to the monitor bus
    • Rated at 10,000VA
    • Located on the transmission
    • Also provide backup power to AC primary buses and 26VAC buses
  3. DC Generators (general)
    • 28VDC, 200Amp
    • Mounted on accessory gearbox
    • Function as starters until 45%N1 (6C+-13)
    • #1 powers Ess Bus and charges battery
    • Gen Cntrl Units - over/undervoltage, reverse current, and ground fault protection - test panel for testing of these functions
  4. External Power,
    Voltage and location?
    • 28VDC
    • Behind right main landing gear door. If left open, causes DOOR OPEN caution light.
  5. AC GEN BEARING light means...
    ...Aux set of bearings has taken over after main bearing failure.  Flight time limited to 5 hours.
  6. AC Inverters
    • Rated at 375VA
    • #1 receives power from #2 DC Prim bus
    • #2 receives power from DC Ess Bus
    • Supply 115V (400Hz) to inverter bus contactors
    • Lights: #1 or #2 INV FAIL caution lights
  7. 26VAC Transformers
    take power from either AC gen or the inverters, step it from 115VAC to 26VAC, and power the #1/#2 26VAC buses
  8. DC Ess Bus Feeder Failure
    Occurs if...
    Warning signs...
    So you should...
    • ...DC ess bus voltage <24Image Upload 10.5V with one or both DC gen operating
    • Problem may have been generator, gen contactor, bus tie contactor, or Ess Bus fuse
    • If it was the bus tie contactor or Ess Bus current limiter, recovery won't work
    • ...ESS BUS VOLTS LOW caution and light on Ess Bus Recovery switch will illuminate
    • ...switch Ess Bus Recovery switch ON (checklist)
    • *Caution light is on primary bus...check CB
  9. Essential Bus Recovery Switch
    • Opens bus tie contactor - this connects #2 DC gen to Ess Bus
    • Opens #1DC Gen contactor (with caution light as Gen 1 is killed)
    • Closes Ess Bus Recovery contactor
  10. AC Gen and Dual Inverter Failure
    • You will lose:
    • DAFCS
    • Both autopilots
    • Compass portion of HSI, ADI, and RMI
    • AHRS light, but not AHRS fail
  11. DECU (general)
    • Digital Engine Control Unit
    • One per engine, forward section of tailboom
    • Powered on Ess Bus until 60%N1, then by engine-driven alternator
    • DECU controls fuel metering valve through stepper motor, operates START and STOP electro valves, and provides...
    • Ovsp protection (122%N2),
Card Set
Electrical system of the S76 C+