Primary finding
Probable cause
Improper replacement of the right wing by maintenance personnel which resulted in the vapor return lines being reversed, and the auxiliary tank vent to be disconnected.
Investigator assessment
Analysis narrative
The pilot was leaving Green Bay, Wisconsin for the return flight to Rockford, Illinois. On the preflight inspection, the pilot said he noticed that the right auxiliary tank was overfilled, but did not worry about it. When he attempted to start the right engine, the right wing exploded. The airplane had recently been painted. During the painting process, both wings had been removed and replaced. The investigation revealed the fuel vapor return lines for the main and auxiliary tanks in the right wing had been reversed, and that the vent for the auxiliary tank had been disconnected, allowing the auxiliary tank to vent to the interior of the right wing.
Source record
Factual narrative
On April 3, 1993, at 1815 central standard time, a Beech B-55, N4167P, sustained substantial damage when the outboard section of the right wing exploded as the pilot started the right engine. The mishap occurred at Austin Straubel Field, Green Bay, Wisconsin. The commercial pilot was not injured. The personal flight was originating at Green Bay, with an intended destination of Rockford, Illinois. No flight plan was filed, and visual meteorological conditions prevailed at the time. The pilot stated he had flown from Rockford, Illinois, to Green Bay using the main fuel tanks. During the preflight inspection for the return trip, he said he noticed that the right auxiliary tank was overfilled. The examination of the wing and fuel system revealed the fuel return lines for the main tank and auxiliary tank on the right wing were reversed. A vent line connection for the right auxiliary tank was found unconnected. The airplane had been recently painted. Both wings had been removed and replaced during the painting. The airplane had flown three hours since the post-painting inspection. -