Air Bridge Piper PA-31-350 accident

After a complete loss of power from the left engine, the airplane was unable to maintain altitude on one engine and collided with large rocks during a landing on a beach at a recreation lake. Following a maximum gross weight takeoff, the airplane climbed to a cruise altitude of 9,500 feet msl. About 20 minutes into the flight, the pilot heard a loud "pop" sound and the left engine surged once. The pilot immediately turned around and started back toward lower terrain. He then attempted to restore power by following the checklist items, but was unsuccessful, and he then completed the shutdown and feather checklists. While proceeding to the closest airstrip for a landing, the airplane would not hold altitude at best single engine rate of climb airspeed and began to drift down. The pilot believed he would have an insufficient altitude margin to make any of the nearby landing airstrips or clear the mountainous terrain between his position and the departure airport. The pilot elected to land on the beach of a lake. During the landing rollout, the aircraft encountered moderately sized rocks and collapsed the nose and left landing gear. The left engine was installed on a test stand and examined. The only discrepancy was a fractured fuel injector line for the No. 6 cylinder injector nozzle. The fracture was completely through the line near the manifold end at a brazed joint between the line and a larger diameter ferrule end. No support clamps were observed on this line between the manifold and the injector nozzle. Support clamps were found on the injector lines to the remaining 5 cylinders. The fractured fuel injector line on the No. 6 cylinder was replaced with a serviceable line and the engine was started, accelerated to full power, and met all specifications. Metallurgical examination of the fractured fuel injector line found that it failed in fatigue from multiple origin sites on the line's outer surface. No material defects or mechanical damage, which could have contributed to the crack initiation, was found at any origin site. No evidence of clamps was found at any point along the line length. AD 93-02-05 applied to this engine and mandated compliance with Lycoming Service Bulletin 342A. The provisions of the AD and the SB require a one time inspection, then recurring inspections of the fuel injector lines at each 100-hour inspection, at each overhaul, and after any maintenance has been performed where the lines have been disconnected, moved or loosened. The line inspection involves looking for any evidence of cracks, dents, or other unserviceable wear indicators. The SB requires that any line found without clamps supporting the line run must be replaced, and that each line must be clamped. Specific clamping points for each line are noted on a diagram for each engine model incorporated within the Service Bulletin. The engine was last inspected on July 14, 2000, 23 hours prior to the accident. The fuel injection system on this engine is a constant flow type and a leak in any one line would reduce the flow to the other cylinders, which would result in an excessively lean condition. Based on both the pilot's report of the conditions at the landing site and the METAR from the closest aviation observation station, the density altitude on the surface was calculated to be 4,700 feet. The outside air temperature at the site, and the estimated temperature at the aircraft's cruise altitude, were outside of the temperature envelope for a positive rate of climb on the aircraft's single engine climb performance chart in the Airplane Flight Manual. According to Piper, the temperature lines on the charts are limits and no extrapolation can be made for points outside of the temperature lines.

Verbatim NTSB analysis and probable cause from the NTSB dataset