N2713TBeech 35-C33A · 1967

On April 25, 2013, about 1806 central daylight time, a Beech 35-C33A, N2713T, was substantially damaged during a forced landing following a loss of engine power near Knoxville, Tennessee. The commercial pilot sustained serious injuries. The airplane was registered to a private individual and operated by the commercial pilot under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the post- maintenance test flight. The flight departed from Downtown Island Airport (DKX), Tennessee, at 1756.

According to mechanics at a repair facility that just completed work on the accident airplanes engine, the airplane owner reported engine roughness and a fuel pressure fluctuation at 7,500 feet. He also reported to the repair facility that when he turned on the auxiliary fuel pump, it caused the engine to run "smooth" and he continued the flight uneventfully. The mechanics went on to say that the when they received the airplane, they checked the fuel screens and checked the fuel system components.

They performed an extensive ground run up and after everything checked out satisfactory, flew the airplane over to another facility for further inspection. They continued to inspect the airplane and checked the ignition system, cleaned, gapped, tested all spark plugs and checked the spark plug wires. All of the fuel screens were checked and no abnormalities were noted. A suction test was performed from the firewall fuel fitting and after 5 gallons of fuel flow, no bubbles were found to indicate air leaks on either tank selection. All of the fuel tank vents were checked and no blockage was noted. All engine compartment fuel hoses were cleaned and examined and no anomalies were noted. During the examination it was discovered that the engine-driven fuel pump inlet fitting was loose. The fitting was removed, cleaned and reinstalled. The fuel flow was tested with the boost pump at the firewall and at the fuel divider; flow was good and uninterrupted. The fuel strainer was examined and no debris was found. All fittings were reconnected and the system was pressure tested and no leaks were noted. Several full-power run-ups were conducted, and all were satisfactory. After the full-power run-ups, screens were checked again and found to be clean. All performance and operational parameters were normal.

The accident pilot/mechanic was performing a post-maintenance test flight. He did a preflight inspection of the airplane and did a full power run-up with the auxiliary fuel pump on and off. He checked all aircraft and engine systems prior to departing; no anomalies were noted and all systems checked satisfactory. Takeoff power, fuel flow and the ground roll were normal. He stated that as a precaution he turned on the auxiliary fuel pump prior to takeoff and the fuel flow was steady in the green arc. Shortly after rotation the engine began to shutter and the fuel pressure dropped. As the airplane climbed out the pilot/mechanic reported that approximately 100-200 feet above ground level the engine lost approximately 70%-80% of power then lost all power. He cycled the auxiliary fuel pump off and on, cycled the mixture, and no changes were noted. The pilot/mechanic went on to say that he could not confirm the total loss of engine power, since by the sound of the propeller it may have been idling between 600 to 800 rpm while at a full power setting. The airplane was unable to maintain lift and a forced landing was performed.

According to a Federal Aviation Administration inspector, the airplane came to rest in a field in a residential area, and exhibited substantial damage. Further examination of the airplane revealed that the right wing outboard leading edge was buckled aft. The engine was broken away from the firewall and engine mounts. The engine was removed from the airframe and it was determined that it could be test run. The engine was sent to Continental Motors Incorporated under the oversight of the NTSB. The engine was re-inspected prior to the test run and impact damage was noted on the engine. During the preparation for the test run minor parts were replaced.

During the testing of the engine it started immediately during the first attempt. The engine ran for 10 minutes before it suddenly lost power; this was attributed to a distortion noted at the throttle body due to impact damage. The fuel was confirmed to and from the fuel manifold. The engine was restarted and a magneto check was performed. The engine was shut down and restarted and ran at full power for approximately 20 minutes without any abnormalities. The engine was shut down and allowed to cool and restarted. An additional engine test run was performed and no abnormalities were noted. The magnetos were bench tested and partially dissembled with no discrepancies noted.

A review of the pilot operating handbook and pilot's abbreviated checklist revealed that the published procedures and limitations stated: prior to takeoff the auxiliary fuel pump should be turned off for takeoff. The airplane was also placarded stating that the "AUX FUEL PUMP OPERATION" for takeoff and landings should be left in the off position except in the case of loss fuel pressure.