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In 2003, mechanical and maintenance were the major cause
of 15% of all GA accidents, and 7.5% of fatal accidents
Typically,
one mistake or failure—a precipitating event—leads
to another in a cascading series of malfunctions and mistakes,
culminatiing in an accident. This is called the accident
chain.
By any calculation, the average pilot could
fly many, many lifetimes without having an accident of
any sort, let alone
a much more rare fatal mishap.
In 2003, electrical/ignition
failures accounted for 3% of all accidents, and 0% of fatal
accidents.
2004 Nall Report
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CIRRUS Monthly Proficiency Program
3 part series on IFR operations
August – Part 1: Electrical Systems
About the CIRRUS Electrical System
The Cirrus SR20 and SR22 airplanes incorporate a 28-volt direct current
negative ground system comprised of two alternators and two batteries.
The two alternators and batteries provide redundancy for safely
operating in the IFR environment.
- Alternators and Batteries
On the SR22, alternator Number 1 (ALT 1) is gear driven and rated
at 28 volts/60 amps. On the SR20, ALT 1 is belt driven and rated
at 28 volts/75 amps. Alternator Number 2 (ALT 2) also is gear
driven and rated at 28.75 volts and 20 amps.
On both the SR20
and SR22, the number one battery (BAT 1) is rated at 24 volts
and 10
amps, while the number two battery (BAT 2) consists
of two 12-volt, 7- amp batteries connected in series.
- MCU (Master
Control Unit)
The MCU controls ALT 1 and ALT 2 voltage regulation, starter,
landing light, external power and power generating functions.
In addition,
the MCU provides external power reverse polarity protection,
alternator overvoltage protection, and alternator fail and
overcurrent annunciations.
Although the MCU is a single unit, it has multiple routes
for electrical flow. This prevents a single point of failure.
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