Service difficulty report · Electrical Sys · Doug DC3C

Difficulty date
December 13, 2013
Submitted
September 14, 2015
Operation
General aviation
Make and model
Doug DC3C
Aircraft time
38,509 hours
Part
Electrical Sys
Condition
Malfunctioned
Part time
38,508 hours
Stage of operation
IN
How discovered
9
Nature of condition
O
Precautionary procedure
K

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

What was found

(CAN) WHILE PREPARING THE ELECTRICAL LOAD ANALYSIS FOR THE ACFT FOLLOWING MODIFICATIONS IT WAS DETERMINED THAT THE LOAD ON SOME OF THE BUSSES EXCEEDED THE LOAD PROTECTION FOR THAT PARTICULAR BUS. FOR PREPARATION OF THE ELECTRICAL LOAD ANALYSIS, THE ORIGINAL LOAD ANALYSIS DATED 1989, WAS USED AS A REF EVEN IN THE 1989 ELECTRICAL LOAD ANALYSIS, THE RT DISTRIBUTION BUS HAD A POTENTIAL LOAD IN CLIMB/APPROACH MODE OF 162.398 AMPS WHILE THE CURRENT PROTECTION FOR THAT BUSS WAS 150 AMPS. ALSO, THE EMERGENCY BUS HAD A POTENTIAL LOAD OF 37.446 AMPS WHILE THE CURRENT PROTECTION WAS RATED AT 30 AMPS. THIS CONDITION, IF LEFT UNCORRECTED, IS A VERY LARGE POTENTIAL RISK. WITH THE ADDITION OF CUSTOMER REQUESTED EQUIPMENT, THIS CONDITION IS AMPLIFIED. THE GENERATORS ARE MORE THAN CAPABLE OF SUPPLYING THE LOAD REQUIREMENTS BUT THE BUS SYSTEM REQUIRES ATTENTION. IF THE BUS CIRCUIT PROTECTION IS TRIPPED, THE FLIGHT CREW WILL LOOSE ALL EQUIPMENT TIED TO THAT BUS.

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