Parker, AZ, USA
N4689D
BEECH H35
The flight instructor and pilot-rated owner were operating the airplane in cruise flight when the engine lost power. They manipulated the engine and fuel controls in an attempt to regain engine power, but the engine would not restart. They subsequently conducted a forced landing onto rough terrain. During the landing roll, the nose landing gear folded underneath the airplane, and the right wing sustained substantial damage. The engine was test run, and it would not maintain power unless the electric boost pump was operating. During a postrun examination of the engine, the fuel return line from the engine-driven fuel pump was found loose at the pump connection, and fuel was noted dripping from the rigid fuel line near the pump connection. The line was removed, and the "B" nut ferrule was found cracked. The "B" nut and the fuel pump fitting threads were damaged. The fuel pump and fuel control assembly were found intact, and, during a test run, functioned properly. During testing of the fuel manifold valve, a leak was observed at the vent port, indicating that the diaphragm was compromised. Based on this evidence, it is likely that the improperly attached fuel return line on the fuel pump and the leak from the fuel manifold valve led to a loss of pressure in the engine fuel delivery system, which resulted in the loss of engine power. The investigation could not determine when or by whom the maintenance was performed.
On May 22, 2014, about 1130 mountain standard time, a Beech H35, N4689D, experienced a loss of power during cruise flight near the Avi Suquilla Airport (P20), Parker, Arizona. The pilot executed a forced landing onto rough terrain, and the airplane was substantially damaged. The airplane was registered to the pilot-rated owner and operated by the flight instructor (FI) under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed for the flight, and no flight plan was filed. The FI and pilot-rated owner were not injured. The accident flight originated from Quail Mesa Ranch Airport (15AZ), Quartzsite, Arizona, about 1115 with a planned destination of P20.The pilot-rated owner (who could not act as pilot in command for medical reasons) reported to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) in a telephone interview, that about 5 miles from P20, the engine lost power. He stated that the engine and fuel controls were manipulated to try and regain engine power. Despite efforts, the engine would not restart, and a forced landing was initiated onto rough terrain. The pilot-rated owner further stated that he had about 15 to 20 gallons of fuel on board prior to departing 15AZ. During the landing roll, the nose landing gear folded underneath the airplane, and the right wing sustained substantial damage. The airplane was recovered to a secure facility in Phoenix, Arizona. Examination of the recovered airframe revealed that the fuselage was damaged and buckled from the firewall to the aft fuselage. The nose landing gear and supporting structure had impact damage. The right wing aft spar was buckled near the main landing gear area. The instrument panel was undamaged, and the radios were removed prior to the examination. The pilot-rated owner reported that the radios were removed prior to the accident flight. The fuel tank quantity gage indicated zero. Engine control cable continuity was established from the cabin controls to the engine components. The fuel selector handle was in the "left tank" position. Fuel was obtained from the fuel selector drain, and was clear of debris and contaminates. The fuel selector inlet screen was removed, and was found to be installed inverted on the lower side of the retention spring. A small amount of fibrous debris was found in the screen. A header tank was attached to each of the four wing tank inlet lines at the wing root areas. The boost pump and the hand pump were used to pump fuel from each of the wing tank lines; no anomalies were noted. The fuel selector had proper detents in each position. Examination of the engine revealed no impact damage. The propeller assembly remained attached to the engine and had impact damage. The top spark plugs were removed, and the electrode areas had light grey deposits. The electrodes had (worn out-normal) conditions when compared to a Champion AV-27 chart. The fuel injectors were removed, and were clear of debris. The fuel manifold valve was disassembled, and a yellow residue was found in the chamber below the screen. No debris was noted in the screen. The fuel control valve inlet screen was removed, and no debris was noted. Fuel was found at each of the previous noted components, and the fuel was consistent with 100LL fuel. The engine was setup for a test run with the use of a header tank and tie downs. The header tank has a vent line and a vented cap. The vented line was open during the engine run. The propeller was removed and replaced with an undamaged propeller assembly. The spark plugs, injectors, and all fuel screens were reinstalled. The engine was primed with the boost pump, and the engine started with little hesitation. The engine continued to run normally with the boost pump in the "ON" position. About a minute after start up, the boost pump was switched to the "OFF" position, and the engine shut down. The engine was run several times resulting in the same conclusion. During the post-run examination of the engine, the fuel return line from the engine driven fuel pump was loose at the pump connection. The line was removed, and the b-nut ferrule was cracked. The flare in the rigid fuel line was not smooth or consistent. The b-nut and the fuel pump fitting threads were damaged. The fuel pump was removed from the engine, and the drive coupling was found intact. The pump was operated by hand, and the drive shaft rotated normally. The pump was submersed in water, and the drive shaft was rotated with the use of an electric drill. The pump operated normally. The pump was disassembled, and no anomalies were noted. The engine driven fuel pump, fuel control valve, fuel manifold valve, injectors, and associated lines were sent to the manufacture for further examination and testing. According to the manufacturers report, the fuel pump and fuel control assembly were intact, and demonstrated the ability to function on the test bench. The fuel manifold valve and nozzles exhibited an abnormal flow vs. pressure indication on the test bench. There was a leak observed at the vent port indicating the fuel manifold valve's diaphragm was compromised.
The improperly attached fuel line and cracked fuel diaphragm due to unknown personnel’s inadequate maintenance, which resulted in the loss of engine power during cruise flight and the subsequent forced landing onto rough terrain.
Source: NTSB Aviation Accident Database
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