ERA14FA421

The inadequate torque of the propeller mounting bolts and inspection of the propeller, which resulted in the fatigue fracture of the bolts and a subsequent in-flight separation of the propeller assembly.

Shortly after departing on a personal cross-country flight and leveling off at the filed cruise altitude, the commercial pilot reported trouble maintaining altitude and descended to a lower altitude. He then reported both engine and instrument problems and requested to divert to a nearby airport. Subsequently, the pilot reported that the engine had lost power, oil was all over the windshield, and that there was no visibility due to the oil. Shortly thereafter, he stated that a forced landing was imminent; the last radar return for the flight was about 2 miles from a nearby airport and in the vicinity of the accident location. On-scene examination of the wreckage revealed that the propeller hub and propeller blades were missing and that oil was noted covering the airplane and windshield fragments. The propeller blades and hub were later located about 8 miles from the accident location. Five of the six propeller mounting bolts were found inside their bores. The sixth bolt was not located. Metallurgical examination determined that the remaining five mounting bolts failed due to reverse bending fatigue. The witness marks on the aft face of the propeller hub were consistent with marks from bolts or bolt fragments while the propeller hub was still partially attached. This would likely occur when the bolt or dowel was still intact before total separation of the propeller assembly. The reverse bending failure of the hub mounting bolts were likely indicative of a loose connection between the hub and the crankshaft. Maintenance records revealed that the propeller was overhauled about 35 flight hours before the accident and was inspected about 15 flight hours before the accident; however, the records did not note, nor were they required to, the torque setting that was achieved. Considering the extensive damage to the propeller flange in conjunction with the limited number of flight hours, it is likely that at least one of the propeller mounting bolts was not torqued sufficiently at the time of installation and gradually loosened during the subsequent flights.

HISTORY OF FLIGHT On September 3, 2014, about 1522 eastern daylight time, an experimental amateur-built Lancair IV-P, N541EM, was substantially damaged when it impacted an open field within an industrial park near Ooltewah, Tennessee. The airplane had departed from McGhee-Tysons International Airport (TYS), Knoxville, Tennessee, at 1451. Day visual meteorological conditions prevailed and an instrument flight rules flight plan had been filed for the flight destined for Jackson-Medgar Wiley Evers International Airport (JAN), Jackson, Mississippi. The commercial pilot was fatally injured. The business flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. Radar and voice communication data from Federal Aviation Administration (FAA) Air Route Traffic Control Center (ARTCC) revealed that the pilot reported on the Atlanta ARTCC frequency that he was at 11,000 feet and requested to deviate to the right for weather. The airplane subsequently leveled at its filed cruising altitude of 16,000 feet above mean sea level (msl). Shortly after reaching cruise altitude, the pilot reported that he was "having trouble holding altitude," descended to 15,000 feet msl, reported "engine problems," and then reported "instrument problems." The pilot subsequently requested to divert to Chattanooga-Lovell Field (CHA), Chattanooga, Tennessee. At 1513, the pilot reported that the airplane "lost engine power" and the corresponding radar return was approximately 7 miles north of Collegedale Municipal Airport (FGU), Collegedale, Tennessee and indicated an altitude of 6,000 feet msl. Then the pilot reported "oil all over the windshield" and that he "could not see a thing." Subsequently the pilot reported "I cannot see it. I cannot make it. I am just looking for anything at this point" and that "a forced landing was imminent." The last recorded radar transponder return for the flight was about 2 nautical miles north of FGU, and in the vicinity of the accident location. PERSONNEL INFORMATION According to FAA records, the pilot held a commercial pilot certificate for airplane single-engine land, multiengine land, and helicopter, with ratings for instrument airplane and helicopter. His most recent second class medical certificate was issued on July 1, 2014. According to the pilot's flight logbook the most recent entry was dated August 21, 2014, and the pilot had 2,811.5 total hours of flight experience. His most recent flight review was conducted on April 28, 2014. According to a representative of the operator, the pilot had 577.1 total hours of flight experience in the accident airplane make and model. AIRCRAFT INFORMATION According to FAA records, the airplane was issued and special airworthiness certificate on March 13, 2000, and was registered to Empire Equipment LLC on July 02, 2007. It was equipped with a Continental Motors TSIO-550 E3B engine serial number 803094. The engine as equipped with a MTV propeller model14-D/4 Blade. Review of the maintenance logbook records revealed an annual inspection was completed on the airframe and engine, on August 13, 2014, at a reported tachometer time of 1741.6 hours. Review of the aircraft maintenance logbook records revealed that on June 17, 2014, the propeller was removed, overhauled, and reinstalled; however, an entry in the propeller maintenance records shows that the propeller was overhauled on June 13, 2014. The propeller maintenance record further revealed that the propeller was inspected on August 13, 2014 and was considered to be in an airworthy condition. METEOROLOGICAL INFORMATION The 1527 recorded weather observation at Chattanooga-Lovell Field (CHA), Chattanooga, Tennessee, located about 9 miles to the west of the accident location, included wind from 040 degrees at7 knots, visibility 10 miles with thunderstorms, few cumulonimbus clouds at 3,200 feet above ground level (agl), scattered clouds at 4,000 feet agl, broken clouds at 18,000 feet agl and 25,000 feet agl, temperature 29 degrees C, dew point 21 degrees C; barometric altimeter 30.03 inches of mercury. The remark section included thunderstorms began at 1527 with occasional lightning in the clouds to the south and southwest of the airport and a thunderstorm south, southwest of the airport moving to the northeast. WRECKAGE AND IMPACT INFORMATION The airplane was located in a grassy area of an industrial park. The airplane came to rest on its belly and the landing gear was retracted. The initial impact point was denoted as a ground scar created by the left wing of the airplane and the main wreckage came to rest 108 feet 8 inches from the initial impact ground scar. The nose of the airplane impacted the ground 16 feet 4 inches from the initial impact point and began with a ground scar similar in shape and dimension as the propeller flange. The debris field was on a 202 degree heading from the initial ground scar and the airplane came to rest on a 015 heading. Subsequent examination of the surrounding area revealed a composite piece of the tail was located about 510 feet and on a magnetic heading of 036 degrees from the initial impact sight. Examination of security video, obtained from a nearby facility, revealed that the airplane impacted the ground in a left wing down, slightly inverted attitude. Subsequently, the nose of the airplane impacted the ground, followed by the right wing. The security video further revealed a mist emanating from the wreckage similar in appearance to fuel spray from the breeched right fuel tank. The airplane exhibited various degrees of impact and crush damage; the empennage, aft of the most aft bulkhead, was separated, but remained in the immediate vicinity of the main wreckage. Both wings exhibited impact damage on the outboard approximate one-half of each wing. Rudder cable continuity was confirmed from both sets of rudder pedals to the rudder horn located in the tail through the cable cut that was made to facilitate recovery. However, the rudder was separated from the vertical stabilizer at the attach points during the accident sequence, and was located in the immediate vicinity of the stabilizer. Elevator push/pull tube continuity was confirmed from both side mounted control columns in the cockpit to the base of the vertical stabilizer mounting surface on the aft bulkhead. The elevator operated smoothly on the separated vertical stabilizer. Left aileron continuity was confirmed from the side mounted control columns in the cockpit to the left wing's fracture point on the outboard section of the wing; however, the aileron was impact separated but was in the vicinity of the wreckage. Right aileron continuity was confirmed from the side mounted control columns to the push/pull tube fracture point at the fuselage wall and from that fracture point to the aileron. The instrument panel remained attached via cables and wires only. The ignition switch was in the "BOTH" position; however, the key was broken off flush with the switch body. All instrumentation remained attached and the turn and bank indicator indicated a left bank turn. The fuel selector valve indicator was on the right fuel tank. The throttle, mixture, and propeller levers were in the full forward position. An oxygen bottle was located securely mounted on the floor of the cockpit and the valve indicated it was still in the green band. The landing gear lever was in the "UP" position and the gear switch was bent to the right. The flap handle was in the full forward position, and the flaps also appeared to be in the "UP" or retracted flap position. On-scene examination of the engine revealed that the propeller flange remained in place; however, the propeller was unable to be located. The propeller flange bolt holes were devoid of any bolts or bolt shanks and the holes were packed with soil from the nose impact point. Approximately 4 weeks after the accident, the propeller was located about 8 miles to the north of t