Incident Summary
Shortly after departure, the flightcrew heard a loud pop or crack, and the airplane made an uncommanded roll to the left. The right generator off light illuminated simultaneously. By holding continuous input to the control yoke, the crew returned the airplane to a wings-level attitude and executed an overweight landing without further incident.
Examination Findings
Post-incident examination revealed that one of two aileron cables on the right side aileron control had been severed by electrical arcing from the right engine generator feed line. No evidence of physical contact between the generator feed cable and the aileron cable was found. However, a pin hole approximately 1/8 inch in diameter was discovered on the plastic sheath of the generator feed cable in the area where the aileron cable passed nearby.
Clearance Issue
The Boeing production drawing specifies a minimum clearance of 1.0 inch between the aileron cable and the generator feed line. After the incident, when the aileron cable was replaced and tensioned on the airplane, the clearance between the aileron cable and generator feed line was measured at only 3/16 inch, significantly less than the specified minimum.