NTSB Identification: NYC04LA119.
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Accident occurred Sunday, May 09, 2004 in Morrisville, VT
Probable Cause Approval Date: 05/30/2006
Aircraft: Piper PA-31-350, registration: N151LL
Injuries: 7 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

During departure, about 700 feet into the takeoff roll, the pilot observed that the left engine "seemed to lose a little manifold pressure," and he aborted the takeoff. While decreasing power during the aborted takeoff, the outboard section of the right wing "exploded." The airplane was stopped on the runway, and the occupants were evacuated. Examination of the airplane revealed that the upper and lower portions of the right outboard wing skin had separated from the wing structure. The inboard fuel cell vent line nipple was broken off from the cell, and examination of the area where the nipple had broken off revealed that the rubber was brittle and deteriorated. Further examination of the wing revealed that a 28-volt power wire used for a wingtip recognition light modification, was routed from the wing root area to the wingtip, following an aft stringer, and passing thru ribs via stringer cutouts with no chaffing protection. The wire was found to be shorted, and displayed evidence of arching to the wing structure. The airplane was equipped with four flexible rubber fuel cells, two in each wing panel. The rubber fuel cell involved in the accident was produced in 1977, and installed during the production of the airplane, which was completed in 1978. The wingtip recognition light modification was completed in 1987. According to the PA-31-350 Service Manual Inspection Report Checklist, a mechanic was to inspect fuel cells and lines for leaks, inspect the condition of the fuel cell material (every two years), and inspect the fuel cell vents (replacing the fuel tank vent line as required, or every five years, whichever came first).

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The improper installation of an electrical wire, which resulted in arching and the initiation of a fuel vapor explosion. A factor related to the accident was the failure of maintenance personnel to detect a cracked rubber fuel vent line nipple.

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