T-45C TS, ADV, & IUT NFamFP-02
Night Emergency Procedures
LECTURE NOTES
Normally, the aircraft Undervoltage Sensing Unit, that is
connected to the 28 VDC Generator Bus, will detect a
generator undervoltage condition: 25 VDC or less.
Should that condition occur, a MASTER ALERT and
GENERATOR warning light will illuminate, as the
generator is disconnected from the electrical system.
Concurrently, the batteries will start powering the
Essential Services Bus; all Non-Essential Busses will
be disconnected. Both inverters will continue to be
powered on aircraft 165457 and up, and on 165456
and below with AFC 199 incorporated.
Should the Undervoltage Sensing Unit fail to detect a
generator undervoltage, there will be no specific
Caution or Warning panel alert to the pilot. When the
generator output voltage drops below the battery
voltage, current will begin to flow from the batteries to
power aircraft systems. Both the Essential and Non-
Essential Busses will continue to operate, draining
substantial power from the batteries. Eventually, as
battery voltage continues to drop, aircraft systems will
be affected: some may partially fail, others may
completely fail, lighting may dim, etc. Specifically, what
signs will alert the pilot to this aberrant condition are
hard to specify, for they will vary as per how the aircraft
has been configured for its mission, whether it's day or
night, instrument or VMC conditions.
As soon as any electrical system anomalies are noted,
the pilot should check the Battery Voltage gauge. If it
is below 25 VDC, it is probable that the Undervoltage
Sensing Unit has failed and the generator is producing
less voltage than the batteries, which are being
drained. The batteries may deplete very rapidly.
Consequently, the pilot should immediately attain IMC
conditions and anticipate total electrical failure. Battery
life may be substantially less than normal (27/12
minutes). The pilot should turn off all nonessential
equipment and immediately position the aircraft so that
it can be safely navigated using ground references.
The pilot should perform the Generator Failure
checklist.
(9-99) Original
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