Service difficulty report · Wire · Piper PA23250

Difficulty date
May 6, 2011
Submitted
May 6, 2011
Operation
General aviation
Aircraft
N817JB
Make and model
Piper PA23250
Aircraft serial
274561
Aircraft time
4,200 hours
Part
Wire
Condition
Shorted
Location
Alternator
Stage of operation
CR
How discovered
O
Nature of condition
H
Precautionary procedure
A

As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.

What was found

WHILE IN FLIGHT THE RT ALTERNATOR FIELD HOT WIRE SHORTED TO GROUND IN THE ALTERNATOR. MAIN VOLTAGE REGUALTOR BREAKER TRIPED. A RESET ALSO RESULTED IN A TRIP. SWITCHING TO THE AUX VOLTAGE REGULATOR GAVE THE SAME RESULTS. A COMPLETE LOSS OF ELECTRICAL POWER RESULTED WITHIN A VERY SHORT TIME DUE TO NO CHARGING FROM EITHER ALTERNATOR. IN THE ACFT BOTH FIELD HOT WIRES ARE ELECTRICALLY TIED TOGETHER AT THE VOLTAGE REGULATORS. A SHORT TO GROUND ANYWHERE IN EITHER FIELD HOT WIRE CAUSES THE VOLTAGE REGULATOR TO TRIP AND STAY TRIPED RESULTING IN NO CHARGING FROM EITHER ALTERNATOR. THIS IS A DESIGN FLAW IN THE CHARGING/WIRING SYS OF THE ACFT. A VERY SIMPLE AND INEXPENSIVE SOLUTION WOULD BE TO PLACE A BREAKER OR SWITCH IN THE FIELD HOT WIRES COMING FROM THE VOLTAGE REGULATOR AND LOCATE THEM ON THE ELECTRICAL PANEL IN THE COCKPIT. THE PILOT WOULD THEN HAVE THE ABILITY TO ISOLATE THE FAILED SHORTED HOT WIRE AND CONTINUE TO GENERATED ELECTRICAL POWER FROM THE OTHER ALTERNATOR.

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