Technical data

13773-001
24-50
Page 1
ELECTRICAL LOAD DISTRIBUTION
1. DESCRIPTION
The power distribution system for this airplane consists of the main distribution bus and the essential distri-
bution bus in the MCU along with the associated buses in the circuit breaker panel and their associated cir-
cuit breakers and switches. Each bus and circuit are labeled on the circuit breaker panel. The clock bus is
fused within the MCU and is the only bus not connected to the master switch arrangement. The clock is
continuously powered through a 5-amp fuse connected to the primary bus in the MCU.
This airplane has four ways of obtaining electrical power for the essential bus. The essential bus can
obtain electrical power from BAT 1, BAT 2, ALT 1, or ALT 2. In an emergency, as long as one of the four
power sources remain functional, the essential bus will continue to supply electrical power to all of the flight
critical instruments. The essential power bus normally receives electrical power from the ALT 2 and BAT 2
electrical systems.
The main power bus receives power from the BAT 1 system (ALT 1 and/or BAT 1). The main power bus
provides power to the essential and nonessential power buses through a network of bus fuses or bus cir-
cuit breakers.
For normal operation, the Essential Buses in the circuit breaker panel are powered from the essential dis-
tribution bus in the MCU through 25-amp circuit breakers. BAT 2 is connected directly to the Essential Bus
in the circuit breaker panel and will power the bus should the voltage coming from the MCU distribution
buses drop below the battery voltage. Additionally, in the event of an ALT 2 failure, the circuit breaker panel
Essential Bus will be powered from ALT 1 through the main distribution and essential distribution buses in
the MCU. Main Bus 1, Main Bus 2, and the equipment Non-Essential Bus in the circuit breaker panel are
powered from ALT 1 through the main distribution bus in the MCU. The Avionics Non-Essential Bus in the
circuit breaker panel is powered from circuit breaker panel Main Bus 1.
Note: Individual circuit load charts and bus schematics showing system current flow during normal
and failure modes are provided in 91-00.(Refer to 91-00]
A. Circuit Protection Devices
The electrical system in this airplane is protected by using circuit breakers and fuses. A circuit breaker
panel is located near the pilot's right leg, and is labeled as to each circuit's identity. The circuit breaker
panel contains all circuit protection devices resettable in flight. The circuit breakers have their rated
values identified on the top of the shaft. The circuit breakers only have two positions, open and closed.
In the open position the circuit is disconnected and in the closed position the circuit breaker will auto-
matically open the circuit if an overload or circuit fault occurs. Each circuit breaker requires a manual
reset by the operator.
Avionics loads on the NON-ESSENTIAL Avionics Bus and ESSENTIAL Avionics Bus are protected by
15-amp AVIONICS circuit breakers connected to the respective bus through relays energized by the
AVIONICS switch.
In addition to the individual circuit breakers, 25-amp circuit breakers located in the Master Control Unit
(MCU) protect the Main Distribution Bus and the Essential Distribution Bus. Additionally a 15-amp cir-
cuit breaker is located in the MCU to protect the landing light circuit.
B. Switches
BAT 1, BAT 2, ALT 1, and ALT 2 master switches are side by side and directly in front of the pilot on the
bolster panel. The BAT 1 switch disconnects battery 1 from the main bus in the MCU. The alternator 1
switch disconnects the forward alternator (ALT 1) from the main bus. If BAT 1 and ALT 1 switches are
in the off position the flight critical instruments will remain powered from ALT 2 or BAT 2. If BAT 1 and
either ALT 1 or ALT 2 switches are turned on, the hour meter becomes activated.
31 July 2001