Cirrus Design Section 7
SR22T Airplane and Systems Description
P/N 13772-003 7-49
Main Distribution Bus 2
The output from ALT 2 is connected to the Main Distribution Bus 2 in
the MCU through an 80-amp fuse. Main Distribution Bus 2 powers
three circuit breaker buses through 30-amp fuses located in the MCU;
• NON ESS BUS,
• MAIN BUS 1,
• MAIN BUS 2.
Electrical System Protection
Circuit Breakers, Fuses and Voltage Suppressors
Individual electrical circuits connected to the Main, Essential, and
Non-Essential Buses in the airplane are protected by re-settable circuit
breakers mounted in the circuit breaker panel on the left side of the
center console. Loads on circuit breaker panel buses are shed by
pulling the individual circuit breakers.
Transient Voltage Suppressors
Transient Voltage Suppressors (TVS) are installed in key ares of the
electrical system to protect the system from lightning strikes. During
lightning strikes, enormous energy spikes can be induced within the
airplane electrical system. In the absence of any transient protection,
this unwanted energy would typically be dissipated in the form of high-
voltage discharge across the avionics and electrical systems of the
airplane. By adding a high power TVS at key power entry points on the
electrical busses, unwanted energy from electrical transients is
allowed to dissipate through a semi-conducting pathway to ground.
• Caution •
If smoke and/or fumes are detected in the cabin and it is
suspected that this event was caused by a TVS failure, the
operator should confirm that there is no fire and perform the
Smoke and Fume Elimination checklist.
Essential Buses
The circuit breaker panel ESS BUS 1 and ESS BUS 2 are powered
directly by ALT 1 and ALT 2 from the MCU Essential Distribution Bus
through 30-amp fuses inside the MCU and also by BAT 2 through the
20-amp BAT 2 circuit breaker.
In the event of ALT 1 or ALT 2 failure, the Essential Buses in the circuit
breaker panel will be powered by the remaining alternator through the
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