Service difficulty report · Connector · Boeing 747238B

Difficulty date
December 15, 1999
Submitted
October 9, 2000
Operation
Air carrier
Aircraft
N163UA
Make and model
Boeing 747238B
Aircraft serial
21353
Aircraft time
82,884 hours, 17,050 cycles
Engine
Pwa JT9D7J
Engine time
68,631 hours, 17,493 cycles
Part
Connector
Condition
Damaged
Location
Nr 1 Pylon
Stage of operation
CL
How discovered
O
Nature of condition
B
Precautionary procedure
O

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

What was found

STRONG SMELL OF SMOKE AT CLIMB AT 23000, MOMENTARY FLAGS ON EPR AND FUEL FLOW GAUGE. NR 1 GEN FIELD LIGHT ON-SAI TOPPED. AFTER RESET APPEARED NORMAL. *S/D* SMOKE SMELL WAS CAUSED BY EXCESSIVE VOLTAGE (~100 VDC) APPLIED TO THE BRIDGE CIRCUIT OF THE NR 1 CSD TEMP INDICATOR. HIGH VOLTAGE WAS CAUSED BY AN INTERNAL SHORT IN THE D11J FIREWALL DISCONNECT ELECTRICAL CONNECTOR. THE CONNECTOR INSULATION WAS DETERIORATED, PROBABLY BY ENGINE OIL. THE INSULATION DAMAGE CAUSED PINS 20, 21 AND 8 TO SHORT TOGETHER. SIGNAL FROM THE CSD TO THE OIL TEMP INDICATOR. SHORTING CAUSED EXCITER POWER TO BE APPLIED TO THE TEMP INDICATOR COIL, WHICH BURNED. SHORT ALSO CAUSED THE GENERATOR TO TRIP OFF-LINE. REPLACED THE D11J CON