N521RTPilatus Aircraft PC-12/47E · 2020

On March 11, 2011, about 1207 central standard time (all referenced times are central standard time), a Lancair model LC41-550FG, N521RT, was substantially damaged during a forced landing following a loss of engine power during cruise flight near Carbondale, Illinois. The pilot was not injured. The airplane was registered to Robertson Contractors, Inc., and operated by a private pilot under the provisions of 14 Code of Federal Regulations Part 91. Day visual meteorological conditions prevailed for the cross-country business flight, which was operating on an instrument flight rules flight plan. The flight departed Eagle Creek Airpark (EYE), Indianapolis, Indiana, at 1049, and was destined for Poplar Bluff Municipal Airport (POF), Poplar Bluff, Missouri.

The pilot reported that during cruise flight the airplane experienced a momentary loss of engine power. He notified air traffic control that he was experiencing engine anomalies and that he was diverting to the nearest airport (Southern Illinois Airport (MDH); Carbondale, Illinois). He stated that as he completed the emergency checklist items, the manifold and oil pressure dropped to zero psi before he heard a loud "pop" sound from the engine. He noted that oil began to spray out of the upper engine cowling, the propeller stopped rotating, and smoke began to fill the cockpit. The pilot reported that the airplane did not have sufficient altitude to reach MDH and he made a forced landing to a nearby harvested agricultural field. During the landing roll, the airplane's right wing struck a power utility pole before the airplane impacted a ditch located alongside a road. The airplane came to rest on the opposite side of the road in a nose-low attitude.

According to Federal Aviation Administration (FAA) records, the pilot, age 28, held a private pilot certificate, issued on February 28, 2010, with single engine land airplane and instrument airplane ratings. His last aviation medical examination was completed on April 21, 2009, when he was issued a third-class medical certificate with no limitations or restrictions. A search of FAA records showed no previous accidents, incidents, or enforcement actions.

The pilot reported that he had accumulated 192 hours of flight time, of which 147 hours were logged as pilot-in-command. All of his flight experience had been completed in single-engine land airplanes, which included 74 hours in the same make and model as the accident airplane. He had accumulated 24 hours in actual instrument meteorological conditions (IMC), 46 hours in simulated IMC, and 17 hours at night. He had flown 11 hours during previous 90 days and 5 hours in the previous 30 days. The pilot's most recent flight review was completed in the accident airplane on June 24, 2010.

The accident airplane was a 2004 Lancair model LC41-550FG airplane, serial number (s/n) 41030. A Continental Motors model TSIO-550-C reciprocating engine, s/n 802677, powered the airplane. The 310-horsepower engine provided thrust through a Hartzell model HC-H3YF-1RF/F7693DF, s/n LX36B, constant-speed, three-blade, metal propeller. The airplane had a certified maximum takeoff weight of 3,600 pounds and was equipped for operation under instrument flight rules.

The accident airplane was issued a standard airworthiness certificate on October 8, 2004. Robertson Contractors, Inc. purchased the airplane on March 3, 2010. The airplane had accumulated a total service time of 501 hours at the time of the accident. The last annual inspection of the airplane was completed on March 1, 2010, at 260 total airframe hours. The last major engine maintenance was completed on January 1, 2008, at 215 total airframe hours, when the No. 5 cylinder was replaced because of a low cylinder compression reading. The right-side turbine inlet temperature probe was replaced on April 27, 2010, at 353 total airframe hours. A review of the maintenance records found no history of unresolved airworthiness issues.

The nearest aviation weather reporting station was located at Southern Illinois Airport (MDH), Carbondale, Illinois, about 5 miles north of the accident site. At 1152, the MDH automated surface observing system reported: variable wind direction at 6 knots, visibility 10 miles, scattered clouds at 25,000 feet above ground level, temperature 10 degrees Celsius, dew point -1 degrees Celsius, and an altimeter setting of 30.19 inches-of-mercury.

The accident airplane was a 2004 Lancair model LC41-550FG airplane, serial number (s/n) 41030. A Continental Motors model TSIO-550-C reciprocating engine, s/n 802677, powered the airplane. The 310-horsepower engine provided thrust through a Hartzell model HC-H3YF-1RF/F7693DF, s/n LX36B, constant-speed, three-blade, metal propeller. The airplane had a certified maximum takeoff weight of 3,600 pounds and was equipped for operation under instrument flight rules.

The accident airplane was issued a standard airworthiness certificate on October 8, 2004. Robertson Contractors, Inc. purchased the airplane on March 3, 2010. The airplane had accumulated a total service time of 501 hours at the time of the accident. The last annual inspection of the airplane was completed on March 1, 2010, at 260 total airframe hours. The last major engine maintenance was completed on January 1, 2008, at 215 total airframe hours, when the No. 5 cylinder was replaced because of a low cylinder compression reading. The right-side turbine inlet temperature probe was replaced on April 27, 2010, at 353 total airframe hours. A review of the maintenance records found no history of unresolved airworthiness issues.

A postaccident examination, completed by a FAA inspector, confirmed that all airframe structural and flight control components were located at the accident site. There were three ground tracks, consistent with the airplane's wheel spacing, identified in the soft terrain that preceded the main wreckage. These ground tracks continued on a south-southwest heading, about 200 yards, until they intersected a ditch and an east-west road. Portions of the airplane's right wingtip were located adjacent to a power utility pole situated about 55 yards north of the east-west road. The main wreckage was located on the opposite side of the road in a nose-low attitude.

Examination of the main wreckage revealed substantial damage to the outboard half the right wing from where it impacted the power-pole. Additionally, the nose landing gear was bent aft and substantial damage was noted to the engine firewall. Flight control continuity was established between the individual flight control surfaces and their respective cockpit controls. The engine was removed and shipped to the manufacturer for further examination. The airplane's primary flight display (PFD) and multi-function display (MFD) devices were removed and shipped to the National Transportation Safety Board's (NTSB) Vehicle Recorder Division for data readout and analysis.

The pilot reported that the engine was always operated at a full-rich mixture setting during the takeoff and climb-to-cruise flight segments. The pilot stated that during cruise flight the engine power was set by selecting a manifold pressure of 31 inches-of-mercury, an engine speed of about 2,400 rpm, which yielded a fuel flow between 22 to 24 gallons per hour. He noted that he would monitor the engine temperatures, including EGT and TIT, throughout the flight using the MFD engine status page. Additionally, the pilot acknowledged that the EGT for the No. 2 cylinder consistently indicated about 150 degrees F warmer when compared with the other cylinders.

The engine was disassembled at the manufacturer's facility under the supervision of the NTSB Investigator-In-Charge. The examination revealed that the piston for the No. 2 cylinder had fractured into numerous pieces that were recovered from the oil sump. Additionally, the exhaust valve for the No. 2 cylinder had fractured where the valve head joined the valve stem. Both portions of the exhaust valve were found in the oil sump. The combustion chamber and both spark plugs for the No. 2 cylinder exhibited mechanical damage consistent with piston fragmentation. The exhaust valve head for the No. 1 cylinder was missing a V-shaped chip and there was a corresponding mark noted on the associated valve seat. The remaining components of the No. 1 cylinder assembly appeared undamaged and exhibited normal operating signatures. The cylinder, piston, and intake and exhaust valves for cylinders Nos. 1 and 2 were retained for additional metallurgical testing by the NTSB Materials Laboratory.

The NTSB Materials Laboratory examination established that the observed mechanical damage to the No. 2 cylinder and its piston was consistent with damage caused by a fractured exhaust valve. Additional examination of the No. 2 cylinder exhaust valve revealed a fracture perpendicular to the stem direction where the valve protrudes into the cylinder head during normal operation. The exhaust valve head, while retaining its general shape, had been extensively damaged. The fracture surface located on the exhaust valve head had been obliterated, which prevented additional analysis. The fracture surface on the exhaust valve stem exhibited a series of crack arrest marks that were consistent with a fatigue failure from multiple crack initiation sites. The entire fracture surface exhibited a high level of oxidation, which was consistent with prolonged exposure to a combustion environment. The chemical composition of the oxide layer revealed chemical compounds consistent with nickel and chromium oxides.

Additional metallurgical testing established that the exhaust valve head and its welded zone conformed to the manufacturer's design and material specifications. The No. 1 cylinder exhibited no impact or grinding damage; however, the inside of the cylinder head was covered with a layer of brittle, flaky spatter material. This material was consistent with deposits observed from coking or oxidizing of oil, which occurs at elevated valve stem temperatures. The V-shaped area missing from the No. 1 exhaust valve head exhibited a level of oxidation and damage that prevented a more detailed microstructural examination. Additionally, the V-shaped area did not exhibit any discernible fracture morphologies or patterns that could be associated with a specific failure mode.

The recovered Avidyne PFD and MFD units contained non-volatile memory that was downloaded and analyzed by a Recorder Specialist with the NTSB Vehicle Recorder Division. The entire accident flight was recorded by the PFD and MFD. The data indicated that the airplane departed at 1049:00 (hhmm:ss) and climbed to a cruise altitude of 10,000 feet mean sea level (msl). The engine cylinder exhaust gas temperature (EGT) spread was about 290 degrees Fahrenheit (F) between the cylinders for a majority of the accident flight. The EGT for cylinders Nos. 1, 3, 4, 5, and 6 were typically within 150 degrees F; however, the EGT for cylinder No. 2 was consistently about 135 degrees F warmer than the other cylinders. (The airplane pilot operating handbook [POH] did not provide a normal operating range for exhaust gas temperature, nor does it specify a maximum allowable value.)

About 1 hour 18 minutes into the flight, the No. 1 cylinder EGT increased about 130 degrees F; however, the other cylinders registered an increase of less than 20 degrees F. At 1156:03, the engine speed, fuel flow, oil pressure, and manifold pressure began to decrease. At 1157:40, the airplane started to descend from 10,000 feet msl and according to acceleration, altitude, and speed data, the airplane landed at 1207:23. The recorded engine parameters remained within their normal operating ranges, as specified by the POH, throughout the accident flight.

Additional MFD data sets, recorded during previous flights, were reviewed for differences in cylinder EGT values. The earliest flight with MFD data was recorded on September 9, 2010. A similar split in EGT temperatures between the No. 2 cylinder and the remaining cylinders was observed on all previous recorded flights. The elevated EGT observed on the No. 1 cylinder during the accident flight was not observed during any of the previous flights. The engine data recorded during cruise segments indicated that the powerplant settings were about 2,400 rpm with an estimated fuel flow of about 23 gallons per hour, at a manifold pressure of about 31 inches-of-mercury. Additionally, the recorded turbine inlet temperature (TIT) values remained within the normal operating range, as specified by the airplane POH. According to the available data, the engine had been operated in a manner consistent with the guidance provided in the performance section of the airplane POH.