Instruction Manual

G1000 / GFC 700 System Maintenance Manual - 200/B200 Series King Air Page 2-15
190-00915-01 Revision 9
2.3 Electrical Power Distribution
This airplane uses a multi-bus system, as detailed below and in Figure 2-20. This Figure shows the
system post installation of this STC. Although this STC made several bussing changes to the distribution
system, the core electrical generation and distribution system remains unchanged from the basic airplane
design. Figure 2-21 shows the power sources for all equipment used by this STC. Each bus used or
modified by this installation is described below.
Left and Right Generator Buses:
The left and right generator buses receive power from their respective
left and right generators. The left and right generator buses also support all four dual fed buses and No. 1
and No. 2 avionics buses, respectively.
Isolation Bus:
The Isolation bus is fed by two generator buses and the battery bus. The Isolation bus is
used in this installation to provide power to the new Standby Instrument Bus and the new Essential bus.
Dual-fed Buses:
The electrical distribution uses four individual dual-fed buses referred through this
document as Dual Fed No. 1 Bus, Dual Fed No. 2 Bus, Dual Fed No. 3 Bus and Dual Fed No. 4 Bus.
Each of these dual fed buses are powered from the Left and the Right Generator buses.
Avionics Buses
: The No. 1 Avionics bus is powered from the Left Generator Bus via the Avionics No. 1
relay. The No. 2 Avionics bus is powered from the Right Generator Bus via the Avionics No. 2 relay.
Both Avionics relays are controlled using the Avionics Master Switch.
Left and Right Engine Instrument Buses
: On serial numbers BB-1484, 1486 and subsequent, the
electrical system includes the L ENG INSTR and R ENG INSTR buses. This STC relocates these two
buses such that they are powered from Dual Fed Bus No. 1 and No. 2 respectively. Prior to these serial
numbers, these two buses are not installed and engine instruments are powered directly from the dual fed
buses. (Figure 2-1 shows the system with these buses installed and relocated.).
Essential Bus
: The Essential bus is a new bus added by this STC. It is powered from Dual Fed No. 1 bus
and the Isolation bus.
Standby Instrument Bus
: The Standby Instrument bus is a new bus added by this STC. It is powered by
the Isolation bus and provides one source of power to the standby attitude indicator and standby altimeter
vibrator.
Entertainment Bus
: The Entertainment Bus is a new bus added by this STC. It is powered from the No.2
Avionics bus via a newly installed Entertainment Bus relay. This relay is controlled via the existing
Cabin Furnishing switch so that bus can be easily shed by pilot using single switch action along with the
other cabin equipment.
Emergency Standby Battery:
The Standby Emergency Battery (STBY BATT) system in the King Air
200/B200 is designed to provide uninterrupted DC power to the Standby Attitude indicator (including
gyro motor and internal instrument lighting), the Standby Altimeter (including vibrator and internal
instrument lighting), and the Standby Airspeed Indicator internal instrument lighting from the L-3 PS-
835(C or D Model) Emergency Standby Battery. This standby battery power is independent from the
normal electrical system and provides redundant power for the standby instruments in the event that all
other electrical power is lost.