Daggett, CA, USA
N7011N
BEECH E33
While in cruise flight, the pilot transmitted that he was in trouble and thought the airplane had experienced a propeller failure. The air traffic controller provided the pilot with instructions to the nearest airport, which was about 21 miles away. The pilot radioed that he thought that he could make it and began a descent toward the airport. A witness near the accident site observed the airplane flying in a southwesterly direction about 500 feet above ground level. As the airplane approached a set of suspended power lines, it pitched up 15 degrees, increased altitude by 100 to 200 feet, yawed to the right, made two 360-degree rotations descending vertically, and impacted terrain, consistent with an aerodynamic stall/spin. Postaccident examination of the engine revealed a 2-inch hole in the top of the crankcase between the Nos. 3 and 4 cylinders. The No. 1 piston connecting rod had separated from the crankshaft, bending the end cap flat with no thermal discoloration evident. Laboratory examination of the bearing insert half identified circumferential wear marks on the back side of the bearing insert. The wear marks on the backside of the intact insert, the lack of heat damage to the connecting rod journal, and the lack of heat damage to the connecting rod and end cap suggest that the bearing began to spin, which led to extrusion/ejection of half of the connecting rod bearing. Once the bearing was free, fragments of bearing material worked their way up between the piston and the cylinder wall causing damage to and embedding in the piston skirt. The increased clearances between the connecting rod end cap and connecting rod journal caused large stress amplitudes that resulted in a fatigue fracture of the connecting rod bolts. In 1998, after 1,002 hours of operation, the engine was top overhauled. A top overhaul does not inspect or replace items inside the crankcase, such as the main bearings or connecting rod bearings. At the time of the accident, the engine had accumulated 2,601 hours. The engine manufacturer recommends that the time between overhaul be 1,500 hours or every 12 years.
HISTORY OF FLIGHT On October 16, 2011, at 1256 Pacific standard time, a Beech E33, N7011N, reported experiencing a loss of engine power, and subsequently impacted terrain during the forced landing 9 miles northeast of the Daggett-Barstow Airport, Daggett, California. The airplane was operated by Fly Corona! as a rental airplane under the provisions of Title 14 Code of Federal Regulations Part 91. The pilot, who had rented the airplane, sustained fatal injuries along with the two passengers. The airplane was substantially damaged. Visual meteorological conditions prevailed, and a visual flight rules flight plan had not been filed. The flight originated from North Las Vegas Airport, Las Vegas, Nevada, about 1200, with a planned destination of Corona, California. The Federal Aviation Administration (FAA) provided a video file containing the radar track of the airplane and associated radio communications. A review of the video file revealed that the pilot checked in with Los Angeles Center at 1253:02, stating that he was level at 8,500 feet mean sea level (msl). At 1253:30, the pilot radioed that he was in trouble, and that he thought the airplane had experienced a propeller failure. At 1253:47, Los Angeles Center radioed to the pilot that the Daggett Airport was at his 1 o’clock at 15 miles. Although the controller stated that the airport was 15 miles away, the radar track plot shows that the airport was 21 miles away at the this time. The pilot said that he thought he could make it to Daggett. Between 1254 and 1256, the pilot and Los Angeles Center exchanged information regarding the number of people on board, fuel state, and airplane color. During this time the airplane continued on a southwesterly course, stabilizing at 105 knots ground speed, and descending from 7,900 feet to 5,400 feet msl. Los Angeles Center continued to call traffic that was ahead about 2 miles, and about 1,000 feet below the airplane; however, the pilot never reported positive visual contact with the traffic. At 1256:29, the final radar return was recorded traveling at a ground speed of 105 knots, at 4,800 feet msl, approximately 3,000 feet above ground level (agl), and 13.7 miles from Daggett. The final radio transmission by the pilot was made at 1257:03, where he stated that he was still watching for the traffic that Los Angeles Center had identified ahead of him. A US Army helicopter pilot in the area at the time of the accident, reported that he heard the pilot state on the Daggett-Barstow airport radio frequency that he had an engine problem, and was 10 miles north of Barstow-Daggett Airport. He then observed the airplane flying on a southwesterly course about 500 feet agl as it approached a series of power lines. The airplane then pitched up 15 degrees, yawed to the right, and made two 360-degree rotations while in a vertical descent before the impacting terrain. There was no post impact fire. PERSONNEL INFORMATION The pilot, age 35, held a private pilot certificate for airplane single-engine land rating issued June 26, 2011, and a third-class medical certificate issued on October 13, 2010, with no limitations. The pilot’s logbook was recovered and examined. His total flight time as of the last logbook entry on September 25, 2011, was 94.4 hours, which included 21 hours in the make and model of the accident airplane. The pilot’s most recent flight review was his FAA private pilot check ride on June 25, 2011. AIRCRAFT INFORMATION The four seat, low wing, retractable landing gear airplane, serial number CD-1123, was manufactured in 1967. It was powered by a remanufactured Teledyne Continental Motors IO-470K3, 225-hp engine, installed on March 19, 1992. The airplane was equipped with a McCauley model 3A36C343 constant speed propeller, which was installed on June 16, 1998. A review of copies of the maintenance records showed that the most recent annual inspection was completed on July 27, 2011, at a total airframe time of 5,468 hours. The engine was last serviced on October 4, 2011, at an engine total time of 2,581.89 hours, with Aero Shell 100 oil. The engine logbook documented that on February 27, 1998, at 1,002.72 hours total time, a top overhaul was completed. The work order for the top overhaul listed the parts that were replaced which included; valve guides, exhaust valve, seals, hose, shaft, gasket set, ring set, clamps, bolds, nuts, gaskets, grade 80/SAE 40 aviation mineral oil, and the overhaul of 6 cylinders. Not included in the parts list were the main bearings or connecting rod bearings. Advisory Circular 43-11 Reciprocating Engine Overhaul Terminology and Standards, defines a Top Overhaul as follows: “Top overhaul consists of repair to parts outside of the crankcase, and can be accomplished without completely disassembling the entire engine. It can include the removal of cylinders, inspection and repair to cylinders, inspection and repair to cylinder walls, pistons, valve-operation mechanisms, valve guides, valve seats, and the replacement of piston and piston rings. All manufacturers do not recommend a top overhaul. Some manufacturers indicate that a powerplant requiring work to this extent should receive a complete overhaul.” On July 1, 2010, trace amounts of metal were found in the oil filter. The engine logbook indicates that the subsequent eight oil filter inspections did not reveal any metal in the filter elements. The total time on the engine at the time of the accident was 2,601.76 hours; time since the top overhaul was 1,599.04 hours. Teledyne Continental Motors Service Information Letter SIL98-9A states that the time between overhaul (TBO) for the IO-470 series engines is 1,500 hours or every 12 years. WRECKAGE AND IMPACT The wreckage was located in a shallow dry desert gully, resting on a 30-degree slope. Witness marks on the slope the same length of the wing indicated about 30-degree angle of bank to the left at the moment of ground impact. The propeller had separated from the engine and was located 15 feet up hill above the main wreckage. The propeller blades were not deformed, and each blade shank was in its proper location relative to the propeller hub. The blades exhibited some light erratic scratches. The engine, firewall, and cockpit floor decking had been pushed up and back into the cockpit and cabin space. The wings exhibited leading edge crushing and hydraulic deformation along the entire length of each wing; the fuel cells had been breached and no fuel was identified within either wing fuel cell. The landing gear main mounts were extended. The ailerons on both wings were attached, the flaps were extended, with both flap actuators exhibiting about 6 inches of extension. The aft section of fuselage and tail were intact with the rudder attached to the vertical stabilizer and the elevators attached to the horizontal stabilizer. Aileron, elevator, and rudder control continuity was established by tracing the control cables from their respective bell cranks to the cockpit. The left side of belly of the airplane exhibited a uniform coating of oil and dirt along its entire length. Examination of the engine revealed a 2-inch hole in the top of the crank case between the number 3 and 4 cylinders. Metal flakes were identified in the folds of the oil filter, and metal flakes were observed distributed on the interior surface of the oil sump. The number 1 piston connecting rod was not attached to the crankshaft; the end cap was bent flat, and was not discolored. The number 4 and 6 connecting rods had separated from the crank shaft and exhibited black discoloration consistent with extreme thermal stress. The number 5 connecting rod was attached to the crankshaft with its end cap attach bolts in place, however, it was discolored brownish-black, and the bearing had deformed, extruding from between the crankshaft and connecting rod yoke. The number 2 connecting rod was attached to the crankshaft and had dark discolorations. Mechanical damage to the interior of the engine case was evident with the most damage observed by the numbers 1, 2, and 4 cylinders. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was performed on the pilot on October 20, 2011, by the San Bernardino County Medical Examiner, San Bernardino, California. The FAA’s Civil Aerospace Medical Institute (CAMI) performed the toxicology on specimens from the pilot. The report indicates that the specimens had experienced putrefaction. No carbon monoxide or listed drugs were detected in the blood samples. The following concentrations of ethanol were detected; 144 mg/dl in muscle, 40 mg/dl in heart, and 20 mg/dl in vitreous. Additionally, 44 mg/dl of n-butanol was detected in muscle, and 1 mg/dl of n-propoanol was detected in vitreous. Toxicological review determined that the ethanol detected by CAMI toxicology was most likely from sources other than ingestion. TESTS AND RESEARCH NTSB Material Laboratory Examination of Engine Components The components that were examined by the lab consisted of the number 1 piston assembly (part no. 649044), piston pin, connecting rod (part no. 646126-B), fragment of the number 1 connecting rod yoke, number 1 connection rod end cap with bolt fragment, one connecting rod bearing shell, and one bolt fragment (part no. 629340). The yoke and the end cap each have a slot to accommodate an anti-rotation tang located on each bearing shell. When the connecting rod is assembled, these slots face one another. For convenience, the side of the yoke and end cap with the slot was referred to as the slot side and the side without the slot was referred to as the plain side. The bolts that attached the end cap to the yoke were fractured approximately midway along their length. The fractured ends were mechanically damaged and had no identifiable fracture features. The threaded bolt ends, along with their respective nuts, were missing, as was one of the connecting rod bearing shells. The piston skirt exhibited a matte grey appearance in some regions, below the pin boss, and a brown tinting in other regions. The underside of the piston exhibited multiple nicks and divots around both pin bosses and the adjacent skirt. The piston was fractured along a 45° spiral path starting at the bottom of the skirt and progressing around and toward the top of the skirt. A lip was observed along the edge of the fracture surface, consistent with an overstress fracture. The matte grey areas on the piston skirt were examined using an optical microscope. Multiple depressions and scratches were seen on the surface as were multiple embedded third-body particles. This part of the skirt was sectioned from the rest of the piston and examined using a scanning electron microscope (SEM). A backscatter image of the region shows bright regions that are embedded third-body particles and the dark regions are the aluminum piston. Multiple embedded particles were detected. One of the third-body particles was examined using energy dispersive spectroscopy (EDS). The particle was composed primarily of copper (Cu), iron (Fe), lead (Pb), and tin (Sn), consistent with the materials used to manufacture the connecting rod bearings. The end cap was flattened and mechanically damaged. A bolt fragment on the plain side of the end cap was trapped in the bolt hole. The bolt on the slot side had separated from the end cap. On the slot side, the end cap bolt hole outer strap was split apart. The bearing surface on the end cap (the backing surface for the bearing insert) had a shiny appearance and exhibited circumferential wear lines that were consistent with burnishing of the surface. One fragment of the yoke had fractured from the connecting rod. The fracture surface had a rough appearance, consistent with an overstress fracture. The bearing surface on the yoke has a burnished appearance, similar to the end cap. The material around the bolt hole was mechanically damaged except for the material around the outer strap, which had a burnished appearance. The connecting rod bearing shell was visually examined. The tang was fractured from the bearing, but the fracture surface had no interpretable features. On the inside of the shell, the Babbitt was worn through exposing the copper under layer at the edges. In the center of the bearing surface, Babbitt material was still present. The backside of the shell had a shiny appearance and exhibited circumferential wear lines consistent with burnishing of the surface. The entire Materials Laboratory Factual Report is located in the official docket of this investigation.
A loss of engine power due to the separation of a connecting rod, and the pilot's failure to maintain airplane control during a sudden maneuver to avoid power lines during the descent, which resulted in an unrecoverable aerodynamic stall and subsequent spin. Contributing to the accident was noncompliance with the manufacturer-recommended engine overhaul schedule.
Source: NTSB Aviation Accident Database
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