Piper ARCHER III Pilot Operating Handbook page 389

PA-28-181, ARCHER III
SECTION 7 - DESCRIPTION AND OPERATION (continued)
C. STANDBY ALTERNATOR System Description
The B&C Specialty Products Standby Alternator system automatically delivers
electrical power to the aircraft electrical power bus in the event of failure of the
primary alternator, provided the STBY ALTR switch is in the ON position.
Powering the bus allows the pilot flexibility to choose equipment suitable to the
current flight conditions. Equipment that would otherwise deplete the battery
reserve may be used within the standby alternator's current limit.
The standby alternator controller monitors the aircraft electrical power bus
voltage and activates the standby alternator if the bus voltage falls to less than
26.0 volts. As long as the electrical load is maintained below standby alternator
capacity, the bus voltage will not fall below 25.0 volts and the battery will remain
charged. Certain flight maneuvers such as climbs and lower power settings will
result in an engine RPM less than 2500. Flight conditions resulting in less than
2500 engine RPM will reduce the standby alternator system capability and
possibly require load shedding to maintain a system voltage above 25 volts. As
long as a minimum bus voltage of 25 volts is maintained, battery energy will
then be available for landing lights and other approach loads.
The standard aircraft amperage indication represents the standby alternator
output when the STBY ALTR ON annunciator is lit.
The standby alternator is capable of outputs greater than maximum continuous
load for less than 5 minutes without damage. Extended operation over rated load
may cause immediate or premature alternator failure and battery depletion.
During operations with low engine RPM, electrical system
voltage may decrease below 26 volts, causing the STBY
ALTR ON annunciator light to illuminate.
ISSUED: JULY 12, 1995
REVISED: FEBRUARY 14, 2006
NOTE
SECTION 9
SUPPLEMENT 23
REPORT: VB-1611
35 of 36, 9-187