NTSB Factual Report

On March 19, 2007, at 2155 eastern daylight time, a Beech 95-B55, N500JP, was substantially damaged following a right wing explosion during engine start at the Fulton County Airport-Brown Field (FTY), Atlanta, Georgia. The airline transport-rated pilot and the commercial pilot rated passenger were not injured. Visual meteorological conditions prevailed and no flight plan was filed for the positioning flight from FTY to Cobb County Airport-Mc Collum Field (RYY), Atlanta, Georgia. The airplane was registered to Caravan Leasing LLC and operated by Midline Airfreight Incorporated under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91.

The pilot stated that he landed at FTY to drop off a passenger, before returning the airplane to its home base. He said that after conducting a preflight inspection he started the left engine normally. He then primed the right engine with the electric fuel boost pump selected to "high boost," and initiated a right engine start. During the start, he heard a "thump" from the right side of the airplane, observed a small fire from the right engine cowling, and immediately stopped the engine. The pilot and passenger exited the airplane and noticed severe damage to the right wing from the engine nacelle to the wing tip.

During a telephone interview, the passenger stated that another company pilot reported a fuel leak from the same wing two weeks prior to the accident. The passenger further stated that he flew on the airplane five times after that report but never noticed a fuel leak.

Examination of the right wing revealed that the wing tip was split open, and the remainder of the wing was ruptured from the landing gear wheel well to the wing tip. An examination of the fuel system revealed that the fuel cell was not breached, neither were any of the fuel lines. Inspection of the wiring system did not reveal any chaffing or broken wiring throughout the wing, and all of the electric wiring was properly harnessed.

During examination and testing of the right main fuel tank, it was serviced with 29.2 gallons of fuel, which filled the tank. During the servicing, a "B-nut" fitting on the output side of the fuel boost pump leaked. The fuel that leaked from the fitting measured approximately "10 drops of fuel per-minute," and collected in the wheel well area. The fuel boost pump was then actuated in the "high-boost" position, and the "B-nut" fitting leaked at the same rate.

Examination of the maintenance logbooks revealed that the right wing fuel cell was replaced on December 29, 2006, at 3197.5 total aircraft hours. At the time of the accident, the airplane had accrued 3209.5 total aircraft hours.

NTSB Probable Cause

The improper maintenance of the "B-nut" fitting adjacent to the fuel pump by maintenance personnel, resulting in a fuel leak and wing explosion.