CEN12FA561

The pilot reported that the experimental, amateur-built airplane was in cruise climb when he noticed a gradual loss of fuel pressure, so he diverted to a nearby airport. The engine fuel pressure continued to drop, and the engine then lost total power. The airplane landed hard on the runway, which resulted in substantial damage to the composite wing structure and breached both wing fuel tanks. An examination of the engine revealed no defects or anomalies that would have precluded normal operation. An examination of the steel-braided flexible fuel lines removed from the electric fuel boost pump showed that two of the lines were installed twisted and that one of the lines was kinked and installed with a bend radius tighter than specified. The improper installation of the fuel lines caused a permanent set in the steel braid and a subsequent partial collapse of the inner wall of the fuel lines, which resulted in the partial blockage of fuel flow through the line and a subsequent loss of engine power due to fuel starvation.

On August 4, 2012, about 1030 central daylight time, a Savage Air LLC, Epic LT, experimental, amateur-built, pressurized single-engine turboprop airplane, N603JS, was substantially damaged during a hard landing at San Saba County Municipal Airport (81R), San Saba, Texas. The pilot and the three passengers were not injured. The airplane was registered to and operated by Savage Air LLC; Austin, Texas, under the provisions of 14 Code of Federal Regulations Part 91, as a personal flight. Day visual meteorological conditions prevailed and an instrument flight rules flight plan had been filed. The flight originated from Rusty Allen Airport (RWY), Lago Vista, Texas, about 1005, and was destined for Centennial Airport (APA), Denver, Colorado.The airplane was in a cruise climb about 19,000 feet mean sea level (msl) when the pilot noticed a gradual loss of fuel pressure. The pilot diverted to 81R and reported that the engine fuel pressure continued to drop below the minimum pressure. On a crosswind leg there was a complete loss of engine power. As the airplane was about mid-field on a downwind leg the pilot noticed construction equipment nearby and the runway was marked with a yellow "X". The pilot confirmed the runway was clear and he performed an engine-out landing touching down hard on the runway about 1,000 from the approach end. The airplane came to a stop on the runway. The occupants exited the airplane and discovered that the hard landing had resulted in obvious damage to both wings and that fuel was then quickly draining out of the airplane. The Electronics International (EI) MVP-50P panel-mounted electronic engine display was removed and sent to the National Transportation Safety Board vehicle recorder laboratory where the data files were recovered normally. The data showed that the unit had recorded the accident flight and had operated for 32 minutes and 9 seconds. Normal engine operation was noted until about 8 minutes before the end of the recording when fuel pressure and fuel flow indications suddenly dropped. A few seconds later there was a corresponding drop in recorded engine performance. Erratic fuel flow and fuel pressure were noted for about the next four minutes, then measures of engine performance suddenly dropped consistent with a loss of engine power. The recorded data ended four minutes later. A postaccident examination of the airplane revealed a displacement of both main landing gear trunnion attach fittings and separation of the carbon fiber structure in that area of both wings. The separations in the wing structures also compromised both wing fuel tanks and resulted in an almost complete loss of fuel. A closer examination of the fractures to the composite wing material on the accident airplane showed they were good overstress fractures with no indications of manufacturing defects or anomalies. The Pratt and Whitney Canada (PWC) PT6A-67A engine, serial number PCE-RT0032, was also examined and no defects or anomalies were found.The single electric fuel boost pump was removed and examined. Although the pump had an unauthorized modification to the pressure relief valve, tests showed the pump was operational and met the minimum flow rates at specified pressures. Photographs of the fuel pump before removal showed the plumbing was of steel braided flex lines. Two of the flex lines had been installed with a twist, and one of those twisted flex lines was also kinked as a result of an installation with a bend radius tighter than specified. When the lines were removed the twisted and kinked areas showed a permanent set in the steel braid exterior. Exemplar borescope camera photographs of similar fuel lines damaged by twisting and bending showed that the Teflon inner wall of the fuel lines in the earlier events had delaminated and collapsed, with a resulting partial blockage of fuel flow through the line. Since the accident, the manufacturer no longer uses a single fuel boost pump; instead, they now use two boost pumps, with one pump submerged in each wing tank. In addition, the manufacturer no longer uses flexible fuel lines in their manufacturing process.