Ooltewah, TN, USA
N541EM
KLAAS DEVELOPMENT INC LANCAIR IV P
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 the accident location in a pasture. The propeller blades and hub were examined at the recovery facility. Examination revealed both dowel pins remained inside their respective holes and five of the six bolts remained inside their respective bores. The bore that was devoid of any bolt remnants was examined and elongated. The hub assembly aft face also indicated score marks and impression around the radius of the hub and were generally equal in distance from the center of the hub. The propeller assembly was sent to the NTSB Materials Laboratory in Washington DC for further examination. For more detailed information on the propeller examination, reference the "Propeller Examination Report" located in the docket associated with this accident. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was performed on the pilot on September 4, 2014, by the Office of Hamilton County Medical Examiner. The cause of death was "Multiple blunt force injuries due to aircraft crash," the report went on to list the specific injuries. Forensic toxicology testing was performed on specimens form the pilot by the FAA Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma. The toxicology report stated no ethanol was detected in Vitreous, no carbon monoxide was detected in the blood, and no drugs of abuse were detected in the urine. TEST AND RESEARCH The propeller was examined at the NTSB Materials Laboratory. During the examination it was noted that the aft side of the propeller hub had separated from the forward side of the crankshaft due to the failure of six hub-mounting bolts; however, one bolt or bolt fragment was absent and unable to be located. The aft surface of the propeller hub exhibited crescent and circular witness marks around the periphery of the aft hub face. The marks were oriented as pairs of hemispherical-shaped wear marks at each bolt eye and were consistent with impact from whole or fragmented attachment bolts or dowels. The fracture surfaces of all the located bolt fragments exhibited two thumbnail-shaped crack features, which exhibited crack arrest marks emanating from the surface of the bolts. The fracture characteristics were consistent with failure from reverse bending fatigue and were consistent with fatigue striations an overstress failure. The bolt hardness, when tested averaged 41 HRC [Hardness Rating Conversion], which was above the minimum required hardness of 38 HRC. For more detailed information about the examination of the propeller hub reference the "NTSB Materials Laboratory Report" in the docket associated with this accident. Several electronic devices were sent to the NTSB Recorders Laboratory in Washington DC. Some of the devices, such as the Traffic Collision Alerting Device (TCAD) 9900B and Flightcom DVR, either did not have the ability to record data or the external battery was impact separated and any recorded data was subsequently lost. The Electronics International R-1 Tachometer, oil pressure, and manifold gauge were able to record various sampling rates, about once for every 4 minutes, and captured the accident flight. The last recorded data for the tachometer indicated 0 rpm and the last record oil pressure and temperature, recorded 75 seconds prior to the tachometer data, indicated 11 psi and 145 degrees F respectively. The second to last manifold pressure record indicated a reading of 9.1 inches of mercury (inHg) and the subsequent recording, 218 seconds later, recorded 28.7 inHg. In the previous 6 recordings indicated a range of 36.1 to 37.4 inHg. Otherwise the recorded data was unremarkable. For more detailed information reference the "NTSB Electronics Device Factual Report" located in the docket associated with this accident. The propeller governor was sent to the manufacturer for examination. The examination revealed damage which prevented operational testing of the governor. The governor was disassembled and the internal components were visually examined. The damage to the governor was consistent with impact damage. The examination revealed no preimpact mechanical malfunctions or abnormalities prior to the impact. ADDITIONAL INFORMATION Engine Examination The engine was shipped to the manufacturers facility for disassembly and detailed examination. The engine exhibited crush damage to the oil pan and rotation was only able to be accomplished through approximately 60 degrees of arc, as noted on the accident scene. The engine driven fuel pump exhibited impact damage around the aneroid casing. Both magnetos exhibited impact damage to the case and the right magneto drive gear. Borescope examination of the cylinders revealed minimal damage to all cylinders except Cylinder No. 5. Examination of Cylinder No. 5 revealed the connecting rod and bearing were damaged. Examination of the connecting rod and crankshaft area associated with Cylinder No. 5 exhibited signs similar to overheating from oil starvation. The crankshaft gear was observed through the aft and right front side of the engine case. Several gear teeth associated with the front gear were missing and exhibited heat signatures similar to oil distress. Heat stress was noted throughout the crankshaft and was similar to stress from oil starvation. No other abnormalities were noted that would have precluded normal operation. For more detailed information on the engine examination reference the "Engine Examination Report" located in the docket associated with this accident. Operator Aircraft Usage Log According to the operator's "Aircraft Usage" log, the airplane flew 35.2 hours since the propeller was overhauled and 15.3 hours since the most recent inspection, which did not include the accident flight. Of those 15.3 hours the pilot flew 3.7 hours. MT-Propeller Installation Guidance According to the MT-Propeller installation manual and considering the engine horsepower, the required torque value range for the 1/2 inch 20 UNF bolts would be between 90 and 100 foot-pounds of torque. The torque wrench that was reported to be utilized during the torqueing of the mounting bolts, was tested by an FAA inspector at a nearby facility. The wrench was examined and utilized settings for only foot pounds. The wrench was tested and found to be within tolerance and no abnormalities were noted with the wrench.
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.
Source: NTSB Aviation Accident Database
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