History of Flight
On September 8, 2020, about 1130 central daylight time, a Piper PA-28-181, registration N4166Z, sustained substantial damage during an accident near McMinnville, Tennessee. The pilot and two passengers were fatally injured. The aircraft was owned by Lebanon Flying Club and operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
The flight originated from Murfreesboro Municipal Airport (MBT), Murfreesboro, Tennessee, and landed uneventfully at Warren County Memorial Airport (RNC), McMinnville, Tennessee, on runway 23 at about 1123. Security video showed the airplane taxied back to the runway beginning for takeoff about 1128 and disappeared from camera view during initial climb about 1 minute later. Smoke was observed emanating from the airplane before it left the camera's field of view. A witness in his backyard heard the engine go silent, then heard the sound of an impact about 30 seconds later. He briefly glimpsed the airplane through trees but could not determine its attitude. Radar data recorded the airplane's arrival at RNC, but during departure it did not climb above about 500 ft above ground level, so no further radar returns were recorded.
Pilot Information
The pilot's logbook indicated she received a flight review on February 23, 2020. The only subsequent entry was dated August 20, 2020, when she successfully completed a 1-hour checkout flight to use a flying club airplane. The accident flight was her next flight.
Aircraft Information
The engine had been overhauled by Continental Motor Services (CMS), Fairhope, Alabama, on January 29, 2019. It was returned to CMS on September 10, 2019, at 300.45 hours since overhaul for inspection due to a propeller strike. At the time of the accident, the engine had accumulated 671.1 hours since overhaul over about 19 months.
Wreckage and Examination
FAA inspectors and an airframe manufacturer representative examined the accident site. The airplane came to rest flat and upright in a field about 1,000 ft northwest (45° right of the runway departure end) of runway 23. All major components were accounted for and remained intact. The engine was canted to the right, and the left side of the empennage exhibited buckling. The cabin roof had been separated by first responders, and three lapbelts were cut by first responders, though their ends remained attached to the fuselage attach points.
Fuel remained in both wing fuel tanks, and the fuel selector was positioned to the right main fuel tank. Flight control continuity was confirmed from the cockpit to all flight control surfaces, and the flaps were retracted. The pitch trim jackscrew measurement corresponded to a partial nose-down trim setting. Engine examination revealed that the No. 4 cylinder head was fractured circumferentially, exposing the top of the piston. The cylinder head was displaced horizontally from the crankcase, with the pushrods and pushrod tubes captured in the cylinder head but dislodged from the crankcase.
Metallurgical examination of the cylinder showed a flat fracture with thumbnail-shaped arrest marks consistent with fatigue cracking, observed around approximately 180° of the cylinder circumference. The fatigue cracking originated at the vertical stiffener on the front of the cylinder between the third and fourth fins, at the start of the fillet between the stiffener and the circumferential outer wall. The remainder of the fracture surface was consistent with overstress.
The cylinder material hardness was measured on the designed flat on the intake side of the cylinder head near the barrel junction at approximately 59 HB/10mm/500kgf (converted from 19.9 HRA). The manufacturer drawing specified a hardness of 60-75 HB/10mm/500kgf. A portion of a cooling fin was chemically analyzed using standardless semiquantitative energy dispersive spectroscopy; the measured weight percentages of the cylinder cooling fin material were within manufacturer specifications.
Medical and Pathological Information
An autopsy of the pilot performed by the State of Tennessee Office of the Medical Examiner listed the cause of death as multiple blunt force injuries. Toxicology testing by the FAA Forensic Sciences laboratory detected trimethoprim in blood and urine; this anti-infection medication is not considered impairing.
Additional Information
The cylinder was manufactured in 2018 by Continental Aerospace Technologies (CAT), which acquired Engine Components International Division (ECi) in 2015. FAA Airworthiness Directive (AD) 2009-26-12, issued February 4, 2010, affected about 18,000 ECi cylinders regarding inspection and/or replacement for cracks and cylinder head separation. The accident cylinder was not subject to the AD because it was manufactured after the AD was issued. Review of FAA service difficulty reports found no other cylinder head cracks or separations involving cylinders manufactured after the AD.