ELECTRICAL SYSTEM

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ELECTRICAL SYSTEM

• 28V DC electrical system.
• 34 ampere-hour, 24 volt Nicad battery located in
  right wing.
• Two 250amp starter/generators.
• Two 115V and 26V AC inverters powered by their
  respective generators.
• External power receptacle.

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Generator Control Panel

• Each generator is equipped with a generator
  control panel (GCP) which provide
• Voltage regulation
• Generator paralleling
• Reverse current protection
• Overvoltage protection
• Over-excitation protection

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Electrical Bus System

• The electrical system is divided into buses to
  provide redundancy and ground fault protection.
• Current limiters, circuit breakers, and one way
  diodes distribute electricity and isolate buses
  as necessary.
• Critical components are strategically powered by
  more than one bus.
• Dual components are powered by separate buses for
  redundancy ie. left/right landing light.
• The hot battery bus provides power to critical
  items when the battery switch is off.
• The isolation bus utilizes 325 amp current
  limiters to isolate the battery and the generator
  buses in the event of a ground fault.

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INVERTERS

• Each inverter receives DC power from its
  respective generator bus.
• Only one inverter may be powered at a time.
• The inverters supply 26V and 115V AC for the
  weather radar and engine gauges.

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AVIONICS

• Avionics are arranged on three separate buses to
  allow for sufficient avionics under a load shed
  situation.
• The avionics master switch is powered to the off
  position to provide switch redundancy.
• In the event of a switch failure the CB may be
  pulled in order to restore avionics power.

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FUEL SYSTEM

• Each engine is supplied by its own fuel system,
  connected with a crossfeed valve.
• Each system has three tanks main, auxiliary, and
  nacelle (collector).
• Fuel from the main and aux. tanks are fed into
  the nacelle tanks in order to feed the engines.
• Fuel flows from the nacelle tank through the
  firewall shut off valve to the primary boost
  pump, to the high pressure fuel pump, into the
  engine.

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FUEL PUMPS

• The system incorporates 4 fuel pumps per side
• High pressure boost pump engine driven pump
  creating fuel pressures of 900psi to feed the
  FCU.
• Primary boost pump (low press.) engine driven
  pump feeding 25-30psi fuel to the high pressure
  boost pump to prevent cavitation.
• Standby boost pump electric pump which is used
  as a backup to the primary boost pump, and for
  crossfeed operations.
• Jet transfer pump a motive flow pump which is
  used to transfer fuel from the aux. tank.

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FUEL PRESSURE

• If the low pressure engine driven boost pump
  should fail the corresponding FUEL PRESS
  annuciator will illuminate.
• The electric standby boost pump shall be turned
  on by the pilot allowing normal operation.
  Annunciator should extinguish monitor engine
  instruments.
• If the standby pump fails to extinguish the
  annunciator continued operation is limited to 10
  hours between engine driven high pressure fuel
  pump overhaul or replacement.

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FIREWALL SHUTOFF VALVES

• Each engine is equipped with an electrically
  powered fuel shutoff valve, powered by the hot
  battery bus and a duel fed bus.
• When the pilot closes a fuel firewall valve all
  fuel is cutoff from the engine.
• This provides protection during an engine fire
  situation.

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CROSSFEED SYSTEM

• Crossfeed is controlled by a pilot actuated
  crossfeed switch.
• Correct operation of the crossfeed system is
  indicated by the illumination of the green fuel
  crossfeed anninciator and both fuel pressure
  annunciators being extinguished.
• Activation of the crossfeed switch opens the
  crosssfeed valve and energizes the standby boost
  pump on the side supplying fuel.

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AUXILIARY FUEL TRANSFER SYSTEM

• Automatically transfers fuel from the aux tanks
  to the nacelle tank anytime there is fuel in the
  aux tanks.
• An aux transfer override feature is incorporated
  to bypass the float switch in the event of a
  failure.
• A no transfer warning light will illuminate
  anytime there is fuel in the aux tank and fuel
  transfer is not occurring automatically.

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