N4166ZPiper PA-28-181 · 2000

On September 8, 2020, about 1130 central daylight time, a Piper PA-28-181, N4166Z, was substantially damaged when it was involved in an accident near McMinnville, Tennessee. The pilot and two passengers were fatally injured. The airplane was owned by Lebanon Flying Club and operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot flew uneventfully from Murfreesboro Municipal Airport (MBT), Murfreesboro, Tennessee, to Warren County Memorial Airport (RNC), McMinnville, Tennessee. Review of security video at RNC revealed that the airplane landed on runway 23 about 1123. It then taxied back to the beginning of the runway 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 travelled beyond camera view. A witness, who was walking in his backyard heard an airplane engine go silent, then heard the sound of an impact about 30 seconds later. During that time, he briefly saw the airplane through trees but could not determine its attitude. Review of radar data revealed targets consistent with the accident airplane arriving at RNC, but the airplane did not obtain enough altitude upon departure (about 500 ft above ground level) for any further radar data to be recorded.

According to the pilot’s logbook, she received a flight review on February 23, 2020. The only other entry was dated August 20, 2020, when she satisfactorily completed a 1-hour checkout flight to use a flying club airplane. The next flight was the accident flight.

The engine was overhauled by Continental Motor Services (CMS), Fairhope, Alabama on January 29, 2019. The engine 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 accrued 671.1 hours since overhaul during a period about 19 months.

Examination of the accident site by Federal Aviation Administration (FAA) inspectors and a representative from the airframe manufacturer revealed that the airplane came to rest flat and upright in a field about 1,000 ft northwest (45° right of runway departure end) of runway 23. All major components of the airplane were accounted for and remained intact. The engine was canted right, and the left side of the empennage exhibited buckling. The cabin roof had been separated by first responders. Three lapbelts were cut by first responders, but their ends remained attached to the respective fuselage attach points.

Fuel remained in both wing fuel tanks, and the fuel selector was found 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. Measurement of the pitch trim jackscrew corresponded to a partial nose-down trim setting. Examination of the engine 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 such that the pushrods and pushrod tubes remained captured in the cylinder head but were dislodged from the crankcase.

Metallurgical examination of the cylinder revealed a flat fracture with thumbnail-shaped arrest marks consistent with fatigue cracking, which was observed around approximately 180° of the cylinder circumference. The fatigue cracking emanated from the vertical stiffener on the front of the cylinder between the third and fourth fins. The fatigue cracking appeared to initiate at the start of the fillet between the vertical stiffener and the circumferential outer wall of the cylinder. The remainder of the fracture surface was consistent with overstress.

The hardness of the cylinder material was measured on the designed flat on the intake side of the cylinder head near the barrel junction. The hardness of the cylinder material measured approximately 59 HB [Brinell hardness number]/10mm/500kgf [kilogram-force] (converted from 19.9 HRA [Rockwell A hardness number]). The hardness specified on the manufacturer drawing was 60-75 HB/10mm/500kgf. A portion of one cooling fin was sectioned from the cylinder and the chemical composition was determined using standardless semiquantitative energy dispersive spectroscopy. The measured weight percentages of the cylinder cooling fin material were within specifications when compared to the composition required in manufacturer material specifications.

An autopsy was performed on the pilot by the State of Tennessee, Office of The Medical Examiner, Nashville, Tennessee. The cause of death was multiple blunt force injuries.

Toxicology testing was performed on the pilot by the laboratory at FAA Forensic Sciences. The results revealed trimethoprim detected in blood and urine. Trimethoprim is an anti-infection medication and not considered impairing.

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 on February 4, 2010, affected 18,000 ECi cylinders regarding inspection and/or replacement due to 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 did not reveal any other cylinder head cracks or separations pertaining to cylinders manufactured after the AD was issued.