Accident Sequence
On May 19, 2015, at about 1650 eastern daylight time, a Piper PA-28-181, registration N597JG, was substantially damaged during a forced landing near Corryton, Tennessee. The student pilot and certificated flight instructor (CFI) aboard were not injured. The aircraft was operated by Knoxville Flyers Incorporated under 14 CFR Part 91. Visual meteorological conditions prevailed, and no flight plan had been filed for the instructional flight, which had departed Knoxville Downtown Island Airport (DKX) at 1430.
According to the CFI, the student was performing flight maneuvers when the CFI heard a loud "bang" from the engine area, accompanied by engine roughness and reduced rpm. The CFI assumed control, and the student completed the engine restart checklist in an attempt to resolve the roughness. The engine continued to lose power, and the airplane began losing altitude. The CFI declared an emergency and informed air traffic control that he would conduct an off-airport landing. He performed a forced landing in a field. During the landing sequence, the firewall was damaged.
Postaccident Examination
A detailed postaccident examination revealed that the nose gear mount attachment and firewall were buckled. No further damage was noted on the airframe. Examination of the engine revealed that the No. 4 cylinder head was fractured circumferentially on the head at the outboard barrel thread. The cylinder was removed and sent to the NTSB Materials Laboratory for further examination. Detailed examination of the fracture surfaces showed that a portion of the fracture surface had relatively smooth features with curving crack arrest lines, consistent with fatigue.
Examination of the cylinder revealed markings cast near the exhaust port opening: "ECI" and "AEL85099 IR." A stamp near the intake port opening read "51932-14."
Maintenance and Airworthiness Directive
Review of maintenance logbooks showed that the engine was overhauled on February 7, 2008. On May 1, 2014, the engine had accumulated 1,012.5 hours since overhaul. No anomalies were reported following a compression check performed during the annual inspection. The last engine service (oil change) prior to the accident was entered on May 13, 2015, with a recorded time of 1,509.7 hours since overhaul.
Airworthiness Directive (AD) 2009-26-12, effective February 4, 2010, required repetitive inspections or inspection and early replacement of cylinders with certain ECI part number AEL85099 heads installed on Lycoming 320, 360, and 540 series engines, including the Lycoming O-360-A4M engine installed on the accident airplane. However, the serial number for the cylinder head in this accident was outside the range of serial numbers listed in AD 2009-26-12 and therefore was not subject to the inspection and replacement requirements.