General
CSP
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E
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ROTORCRAFT FLIGHT MANUAL
MD 500E
(Model 369E)
Revision 14
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11
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12. ELECTRICAL SYSTEM
The 500E electrical system is a direct current (DC) system with electrical pow-
er supplied by a 24 volt battery and a 28 volt, 150 amp generator driven by
the aircraft’s powerplant.
The original (‘‘pre−generic") system utilizes a model−specific wire harness with
additional wiring added as needed for optional equipment. Voltage regulation
and control is handled by a voltage regulator, reverse current relay, overvoltage
relay and a generator switch. This ‘‘pre−generic" system was delivered on air-
craft serial numbers 001E through 383E.
Beginning with aircraft serial number 384E the electrical system incorporated
a generic electrical wire harness that is common with other current production
MD500 series aircraft (500N and 369FF) and includes wiring for common op-
tional equipment kits and future growth. Co−location of major power distribu-
tion components, increased size and isolation of main feeder lines, and the use
of a single generator control unit (GCU) increases the reliability and perfor-
mance of the helicopter’s electrical system.
The early (‘‘early generic") version of the generic system utilized an air/ground
switch to disable the ENGINE OUT/low rotor audio warning while on the
ground and a three position RE−IGN test switch that, in addition to testing
the reignition system, also tested the ENGINE OUT/low rotor audio warning.
This ‘‘early generic" version was delivered on aircraft serial numbers 384E
through 508E.
On aircraft serial numbers 509E and subsequent, a modified (‘‘late generic")
version of the system eliminated the air/ground switch, incorporated the EN-
GINE OUT/low rotor audio warning disable into the generator switch, and
changed the RE−IGN test switch back to a two−position, momentary−type
switch. In operating the reignition system and checking the ENGINE OUT/low
rotor audio warning the ‘‘late generic" system functions almost identical to the
‘‘pre−generic" system.
Pilots should be aware that aircraft originally delivered with the ‘‘early gener-
ic" version of the system may have been modified in the field to the ‘‘late ge-
neric" version. Look at the RE−IGN test switch and it’s labelling to determine
which version of the system is installed in your particular helicopter. ‘‘Pre−ge-
neric" and ‘‘late generic" utilize a two−position, momentary−type switch, la-
belled OFF at the bottom and TEST at the top. ‘‘Early generic" systems utilize
a three−position switch labelled OFF at the bottom, FLT in the middle, and
TEST GND at the top (see Section IV for switch location and labelling).
