NYC96IA131

Shortly after departure, the flightcrew heard a loud pop or crack, and the airplane made an uncommanded roll to the left. In addition, the right generator off light illuminated. By holding continuous input to the control yoke, the airplane was returned to a wings-level attitude, and returned for an overweight landing without incident. Examination of the airplane 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 contact between the generator feed cable and the aileron cable was found. However, a pin hole about 1/8 inch in diameter was found on the plastic sheath of the generator feed cable in the area where the aileron cable passed nearby. The Boeing drawing used for production states to maintain a 1.0 inch minimum clearance between the aileron cable and the generator feed line. When the aileron cable was replaced and tensioned on the incident airplane, the clearance between the aileron cable and generator feed line was measured at 3/16 inch.

On June 25, 1996, about 1857 eastern daylight time, Delta Airlines Flight 148, N185DN, a Boeing 767-332ER, experienced flight control problems shortly after takeoff from John F. Kennedy International Airport (JFK), Jamaica, New York. Visual meteorological conditions prevailed. There were no injuries to the 229 occupants. The aircraft received minor damage. The destination was Rome, Italy. The flight was operated under 14 CFR Part 121, and had departed from JFK at 1852.

In the NTSB Incident Report, Delta Airlines stated:

"...The flight departed JFK for FCO and was on radar vectors when a loud "crack" or "pop" was heard in the cockpit. The First Officer was the flying pilot. Approximately one to two seconds after the loud noise was heard, the "right generator off" light illuminated. An uncommanded roll to the left was observed by the First Officer, who countered with right aileron inputs. Control forces required to maintain wings level were high, however the aircraft was controllable at all times. The flight crew disconnected the autopilot and completed the checklist procedure for the generator malfunction. The flight returned to JFK for an overweight landing. The aircraft was landed by the Captain on runway 31L without further incident....."

The left side, right aileron cable P/N A2B-3 was severed at approximately station 340, Water Line 190, Right Buttock Line 67.5. This is just forward of the forward baggage compartment on the right side, in the electrical equipment bay. In the same area, the right generator power feeder bundle W208 passed. The bundle is made up of three generator power feed cables tied together, with each cable protected by a plastic sheath. When the aileron cable was replaced and tensioned, the clearance between the aileron cable and the generator feed cable was measured at 3/16 inch.

Evidence of arcing was observed on the severed halves of the cable. A small hole was found on the fed line at the location next to where the cable separation occurred. No evidence of direct contact between the aileron cable and the plastic sheath over the generator feed cable was found. A small hole, about 1/8 inch in diameter was found on the plastic sheath over the generator feed cable in the area where aileron cable passed next to the generator feed cable.

The Boeing drawing used for production states, "Maintain a minimum clearance of 1.0 inch between bundle [generator feed line] and control cable."

The airplane was delivered in 1991, and had accumulated 5,975.2 hours at the time of the incident.