History of Flight
On September 4, 2008, about 1845 central daylight time, a Weatherly 620B airplane, registration N2036U, was substantially damaged when it impacted terrain after a loss of engine power during aerial application near Atkinson, Nebraska. Visual meteorological conditions prevailed. The commercial pilot was not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 137 without a flight plan. The local flight originated at O'Neill Municipal Airport-John L Baker Field (ONL), O'Neill, Nebraska.
The pilot departed ONL and began aerial application operations. After one pass, he made a climbing left turn to realign for a second pass. As the airplane nose was lowered, the engine began to lose power. The pilot advanced the throttle and mixture controls in an attempt to regain power and turned toward a nearby pasture to land. The engine quit completely before reaching the pasture. The airplane impacted the ground and slid to a stop. During impact, the engine separated from the fuselage and came to rest on the left wing.
Pilot Information
The pilot, age 21, held a commercial pilot certificate with ratings for airplane single-engine land and instrument airplane. His last Federal Aviation Administration (FAA) second-class medical was issued July 17, 2008, with no limitations. He reported 500 total flight hours and 100 hours in this type airplane at the time of the accident.
Aircraft Information
The 1995-model Weatherly 620B, serial number 1596, was a low-wing airplane with fixed tail wheel landing gear, configured for one occupant. It was powered by a direct drive, carbureted, air-cooled, nine-cylinder radial engine, a Pratt and Whitney R985AN-14B, serial number JP202792, rated at 450 horsepower, driving a Hartzell two-bladed controllable pitch propeller.
The last airframe inspection was an annual type inspection completed on May 31, 2008. The airframe had accumulated 2,874 hours at that time. The engine was manufactured on June 20, 2005, and had accumulated 88 hours since its last overhaul, performed by Tulsa Aircraft Engines (TAE), Tulsa, Oklahoma. Total engine time was approximately 3,000 hours.
Wreckage and Impact
The initial impact point was in a flat, grassy pasture. The landing gear collapsed, and the airplane slid on its belly for several hundred feet before impacting a fence and rotating 180 degrees from the initial impact heading. It came to a stop with the engine resting on the left wing near the fuselage. Buckling of the fuselage and firewall indicated the airplane impacted the ground about 10 degrees nose low.
The left wing had leading edge damage on the inboard five feet, including a gouge approximately one foot deep and leading edge crushing. The right wing had multiple gouges in the leading edge, and the inboard five feet showed extensive crumpling. The gouges were consistent with impact damage from metal fence posts. Both wing tanks were breached during impact, and fuel escaped.
The presence of toxic chemicals at the accident site prevented immediate recovery. The airplane was exposed to natural elements for several days, including at least two days of rain showers. Additionally, the engine and wreckage were stored outdoors and uncovered for several weeks before the engine examination.
Weather
Weather at ONL at 1850 was 72 degrees Fahrenheit, dew point 41 degrees Fahrenheit, relative humidity 33 percent, with clear skies and 10 miles visibility. The FAA pamphlet "Tips for Winter Flying" carburetor icing chart indicated no carburetor icing conditions at the time of the accident.
Post-accident Examination
The operator had a second airplane conducting operations from the same location, fueled from the same tank as the accident airplane. The operator checked the fuel in the second airplane shortly after the accident and found no water or contaminants.
The engine was taken to TAE for analysis and warranty repairs. The analysis was conducted with FAA oversight on November 26, 2008. The engine arrived at TAE strapped to a pallet, uncovered during shipment. Initial examination showed cylinders number two and number seven were cracked in a manner consistent with impact damage. The carburetor and fuel pump were removed, the damaged cylinders replaced, oil transfer tubes replaced, and an engine run was conducted. In a test cell, the engine met all performance criteria, and no other defects were noted.
Inspection of the carburetor revealed corrosion consistent with water exposure on internal components, including the finger filter.
Engine and Fuel System Analysis
The fuel pump was removed and disassembled at Quality Aircraft Accessories, Tulsa, Oklahoma, under FAA oversight. The pump arrived intact. The inlet fuel fitting was present, but the inlet fuel line was completely separated at the fitting, with fracture surfaces characteristic of impact damage. The overboard vent tube with fittings and the fuel outlet fitting and line were attached to the pump.
When the inlet fitting was removed, there was evidence of rust on the blades and inlet portion. The outlet fitting had no discernable defects. The pump seal nut showed evidence of oil, contaminants, and minor heat damage to the bearings. The rotor assembly had evidence of water damage and rust deposits in the pump interior, liner, lower journal, and bearing. The deposits were excessive and impeded proper functioning.